Tesi sul tema "Hydrology"

Even though dams are designed to bypass floods of significant magnitudes, floods less severe than the design flood may pose a threat to dams. Ongoing research into climate change also shows an increasing trend towards severe floods, that is an increased probability of floods exceeding the present design floods. Therefore, acquiring understanding of floods and risk reduction measures to mitigate any of their undesired effects is of great importance. Dam safety management in Norway has moved towards active use of risk analyses. At the same time, emergency planning and exercises are emphasized as necessary tools for handling abnormal situations such as severer floods. Few dam safety experts or dam owners have experienced large floods, which makes it difficult to assess the complexity of floods. Floods may also be difficult to assess fully by means of traditional risk analyses, as these normally focus on single dams. Floods have a certain geographical extent and must be expected to occur simultaneously in a system of dams and reservoirs.

This thesis hopes to extend knowledge of floods and dam safety. The main conclusion of a literature review of risk analysis and emergency planning is that human factors must be a focus. This is further supported by findings from the case studies of hazard floods. Emergency planning and exercises are believed to be of major importance to successful flood handling, but a survey of status for these issues in Norway shows that there is still work to be done. Many dam owners have not managed to start developing emergency action plans nor carry out emergency exercises. Not surprisingly, most of these are municipalities and private citizens, typical owners of smaller dams. Further revision of the emergency planning guidelines should take these findings into consideration. The authorities should bear in mind the need for alternative approaches to encourage these dam owners to develop emergency action plans. Possible problems related to development trends in our society also deserve attention, such as increased focus on cost-effective organizations at the expense of safety and the need for robust organizations and technical systems to handle future emergencies.

In many parts of the world snow melt runoff influence discharge from combined sewer overflows (CSO) and flooding in urban drainage systems. Despite this, urban snow hydrology is a field that has received little attention from the urban drainage community. The objectives of this research were to better understand urban snow hydrology and through field work and hydrological modelling quantify effects of anthropogenic activities (AA) on snow distribution, and melt in an urban environment. This means in principle how the presence (design geometry) and operation of roads and buildings influence the snow distribution and melt in urban areas. The Risvollan urban catchment (20 ha) located in Trondheim, Norway, was used as a study area. A literature review of urban snow hydrology was also carried out.

A gridded urban hydrology model (GUHM) was developed as part of the study. The principal idea of the GUHM is to subdivide an urban catchment into orthogonal equal area grid cells. The snow routine in the GUHM is based on an energy balance approach, which together with a soil-runoff routine is used to calculate a time series of rain, snow water equivalent (SWE), snow melt, and runoff, for each grid cell. In GUHM, processes such as snow clearing of roads, locally low albedos, heat/shadowing from buildings, and effects of slope and aspect are included in the model structure.

A technique for observing time series of snow covered area (SCA) for an urban catchment is presented. The method is based on image processing and neural network technology to calculate SCA from a time series of images taken from a tall building in the Risvollan catchment. It was shown that SCA on roads and roofs in general becomes more rapidly snow free during melt periods compared to the park areas of the Risvollan catchment. This can be explained by snow clearing of roads, snowdrift from roofs and high snow melt rates on roofs and roads. The high melt rates was attributed to locally low albedos in vicinity to roads, rooftop snow packs exposure to wind and solar radiation, in addition to anthropogenic heat release from the roofs themselves.

Field observations of SWE were carried out in the Risvollan catchment and it was shown that areal mean SWE located on/or nearby roads and buildings were significantly lower during mid and end of the winter, than in park areas. This can be attributed to higher melt rates caused by AA. A time series of SCA and SWE was obtained through field work for the period from 2000 to 2003 in the Risvollan catchment.

The GUHM was applied and calibrated for the Risvollan catchment for a three year period. Two seasons were used as validation period. Comparison between the simulated and observed SWE, SCA and runoff data showed that the GUHM was able to simulate snow accumulation and melt for whole seasons with short time resolution (1 hour) satisfactory.

The GUHM was used to quantify effects of AA on snow distribution and melt for six different land use scenarios in the Risvollan catchment for the period June 1998 to June 2003. The modelling results showed that when the area coverage of buildings and roads increased, the SCA and SWE more rapidly decreased during melt periods. Because of this more runoff will be produced in the early winter season (Jan-March) compared to if the catchment had been covered with only sparsely vegetated areas.

The simulation results showed that when the impervious surface covers of a catchment increase, the peak and volume runoff will also increase, as expected.

Both the field observations and the hydrological model study carried out in this work showed that AA lowers SCA and SWE more rapidly in an urban environment compared to more untouched terrain. The reasons for this are redistribution of snow, and strong snow melt rates on roads, roofs, and in snow deposit areas. Low albedos and anthropogenic heat release are the main reasons for the enhanced snow melt rates.

The hydrological conditions on the southern slopes of Mt Kilimanjaro, Tanzania, are complex and not similar to very many other places. High annual precipitation with complex distribution patterns occurs on these slopes. Extensive water consumption and concentrated groundwater sources of unknown origin are found on the plains. The distribution and utilisation of the scarce water resources can easily be influenced by change in these and in other factors. A hydrological model is developed for the area and used for studying these processes and their influence on potential change in land use and climate.

This study is a part of a cooperative project between the University of Dar es Salaam, Tanzania and the Norwegian University of Science and Technology in Trondheim, Norway, focusing on how changes in land use influence the hydrologic -al responses of a catchment.

Extensive fieldwork has been performed in the course of several stays in the area. Three gauging stations were established on the slopes south of Mt Kilimanjaro for gauging the runoff from areas with and without influence from human activities. Precipitation and temperature measurements from the lower boundary of the forest reserve and up to 4000 metres above sea level (masl) were performed. Extensive field surveys were performed for identifying and understanding the hydrological processes taking place in the catchment. In addition, hydrological data were collected from the regular observation network.

The stream gauging and the precipitation measurements were analysed. The results were used in a water balance assessment of the southern slopes of Mt Kilimanjaro for determination of the extent of infiltration in the higher areas. Based on the results from the three sub-studies, a hydrological model was developed which describes the vertical water balance above and in the soil zone. The model can be used for investigation of the hydrological impact of changes in land use or climate. The model takes meteorological data as an input in addition to parameters describing the land cover and water demand in the catchment. This was applied for analysing the impact of prospective land use and climate changes.

The analysis of the discharge data and field inspections indicated that no surface runoff comes from the area above 2800 masl. The study of the precipitation data resulted in a function describing the relative distribution of precipitation according to elevation for the southern slopes of Mt Kilimanjaro. The analysis indicates that the maximum precipitation intensity occurs about 400-500 meters higher than previously assumed. The water balance assessment gave indications on the extent of the deep groundwater infiltration on the southern slopes of Mt Kilimanjaro.

These findings were incorporated into the hydrological model, which was calibrated for three catchments on the southern slopes of Mt Kilimanjaro. The calibration for a small 21 km² uphill catchment, a mid-hill 52 km² catchment and a large 1783 km² catchment reaching from the plains to the peak of Mt Kilimanjaro showed good accordance between the simulated and the observed discharge for the three catchments.

The calibrated model was successfully used for simulating the period from 1958 to 2000 for the large catchment and showed good accordance for the simulation period. Simulations with changes in forest cover, water demand and climate were performed. The climate changes simulated were based on the findings from the Intergovernmental Panel on Climate Change and land use and forest cover and were evaluated on the basis of potential management schemes. The simulations indicate that the water demand in the area is not being met, and that changes in water demand are not fully reflected in the river discharge. The results also show that the changes have greater influence in years where the water deficit is already substantial, so called “dry years”, than in years with a smaller deficit.

The tools developed and illustrated can be developed further for use in operational water management predicting the hydrological response due to changes in land use and water demand based on various management schemes. It is advised that the infrastructure developed during this work for collecting further measurements concerning the hydrological elements in the area continues to be operated.

Thesis (Ph. D.)--Ohio State University, 2003.
Title from first page of PDF file. Document formatted into pages; contains xvi, 378 p.; also includes graphics (some col.). Includes bibliographical references (p. 229-252). Available online via OhioLINK's ETD Center

River-floodplain connectivity is defined as the water mediated transfer of materials and energy between a river or stream and its adjacent floodplain. It is generally accepted that restoring and/or enhancing river-floodplain connectivity can reduce the downstream flux of reactive solutes such as nitrogen (N) and phosphorus (P) and thus improve downstream water quality. However, there is little scientific literature to guide ecological engineering efforts which optimize river-floodplain connectivity for solute retention. Therefore, the aim of my dissertation research was to examine feedbacks between inundation hydrology and floodplain biogeochemistry, with an emphasis on analyzing variation experienced along the river continuum and the cumulative effects of river-floodplain connectivity at the basin scale. This was completed through four independent investigations. Field sites ranged from the Atchafalaya River Basin, the largest river-floodplain system in the continental US, to the floodplain of a recently restored headwater stream in Appalachia. We also developed a method to examine river-floodplain connectivity across large- river networks and applied that methodology to US stream network. Largely, our results highlight the role floodwater residence time distributions play in floodplain biogeochemistry. In headwater streams, residence times restrict redox dependent processes (e.g. denitrification) and downstream flushing of reactive solutes is the dominant process. However, in large-river floodplains, redox dependent processes can become solute limited because of prolonged residence times and hydrologic isolation. In these floodplains, the dominant process is often autochthonous solute accumulation. Further, results from our modeling study suggest large-river floodplains have a greater impact on downstream water quality than floodplains associated with smaller streams, even when considering cumulative effects across the entire river network.
Ph. D.

Satellite-based remotely sensed data were used to estimate regional-scale surface energy fluxes and a water deficit index of a semi-arid heterogeneous region in southeast Arizona. Spectral reflectance and radiometric temperature of the surface, derived from the digital counts of TM bands of LANDSAT-5 satellite, were used for this purpose. These reflectance and temperature, along with conventional meteorological information of the region, were used as inputs to numerical models which estimate surface energy fluxes. Point-based meteorological data of the region were spatially extrapolated over a grid of 120 m X 120 m so that it could be used with the spatially continuous remotely sensed data. The water deficit index (WDI) was estimated using surface temperature and a spectral vegetation index, "soil adjusted vegetation index" (SAVI). The surface fluxes were net radiation flux, sensible heat flux, soil heat flux and latent heat flux. Measured values obtained from the meteorological flux measurement (METFLUX) stations in the study area were compared with the modeled fluxes. Latent heat flux (LE) was the most important one to estimate in the scope of this study. The method of spatially extrapolating the point-based meteorological information and combining with the remotely sensed data produced good estimation of LE for the region, with a mean absolute difference (MAD) of 65 W/m² over a range of 67 to 196 W/m² . Also it was found that the numerical models that were previously used to estimate daily LE values from a region using mid-day remotely sensed data (mostly from NOAAAVHRR) can also be used with the mid-morning remotely sensed data (from LANDSAT). Out of the two models tested for this purpose (`Seguin-Itier' and 'Jackson' models), one was found to need some modification so that it could use mid-morning remotely sensed data as inputs. The other was found to be useable as it is, without any modification. Outputs from both models compared well with the measured fluxes from the METFLUX stations. In an effort of estimating the water deficit of the different biomes of the region, WDI of the biomes were estimated. The main goal of this effort was to be able to monitor the surface hydrologic conditions of the region using remotely sensed vegetation and surface information, and minimum ground data. Good estimation of the water deficit condition of the area were obtained by this method. This method was found to be sensitive to a few of the ground information such as wind speed and leaf area index (LAI). It was also found that if the required ground data were correctly estimated, this method could be used as an operational procedure for monitoring the vegetation water stress of the biomes and hence for better management of the region.

El principal objectiu d'aquesta investigació és estudiar la dinàmica hidrològica d'una conca Mediterrània
afectada per canvis d'ús del sòl, mitjançant el monitoreig d'aquest i de l'aigua superficial. Aquest
objectiu s'ha treballat a partir mesuraments de components del balanç hídric pels diferents tipus de
cobertura i sòl, amb règims d'humitat i temperatura de transició.
Aquest estudi s'ha realitzat a la conca de la Ribera Salada (Prepirineu meridional Català, al NE
d'Espanya), amb una extensió de 222.5 km2, i un interval altitudinal de 420 a 2385 m i predomini de
pendents entre 12 - 25 % i 25 - 50 %. El substrat consisteix en conglomerats calcaris massius, calcilutites
i llims. La precipitació es de 507 i 763 mm. Amb sòls poc profunds, calcaris i pedregosos, essent
majoritàriament Inceptisòls (Typic Calciusteps, Typic Haploustepts) i Entisòls (Typic Ustifluvents, Typic
Udorthortents). A les zones més elevades de la conca, els sòls són més humits, degut a l'augment de la
precipitació, on es produeixen processos de descarbonatació del sòl. L'ús del sòl és majoritàriament
forestal, amb presència d'ecosistemes de ribera, subalpins i vegetació submediterrània. Algunes àrees es
troben amb cultius de patata, cereal i pastures. Una de les característiques més importants d'aquesta
conca són els canvis d'ús del sòl que ha patit en els últims 50 anys degut a l'abandó dels masos i cultius
tradicionals. Es seleccionaren vuit llocs de mostreig considerant les següents cobertes: Quercus ilex, bosc
de ribera, Pinus sylvestris, pastures, cultius (cereal-patata) i Pinus uncinata. A partir de l'any 1997 fins el
2005, s'han anat monitorejant el contingut d'humitat del sòl, l'escolament i els cabals. Des del 2004 s'han
anat anotant dades de drenatge. Les variables meteorològiques es mesuren a l'estació de Lladurs de la
XAC (Xarxa Agrometeorològica de Catalunya).
Els resultats obtenguts durant tres anys mostren una domini del règim d'humitat ústic (SSS, 2006), o xèric
en aquells anys més secs. En la modelització de règims d'humitat i temperatura del sòl, s'utilitzaren els
models de simulació NSM "Newhall simulation model" (Newhall, 1976) i JSM "Jarauta simulation
model" (Jarauta 1989). NSM (Newhall,1976) tendeix a sobre estimar el règim d'humitat del sòl, però
JSM (Jarauta, 1989) simula correctament el règim d'humitat del sòl (SSS, 2006) de la conca, funcionant
millor en condicions intermitges d'humitat del sòl. Ambdós models simulen correctament el règim de
temperatura dels sòls. Predomina un règim de temperatura mèsic-tèrmic, amb tendència a tèrmic els anys
secs. A petita escala la profunditat del sòl, pendent, pedregositat i una alta porositat del sòl són factores
que varien el règim d'humitat del sòl. La informació de sòl i clima, complementada mitjançant SIG, va
permetre l'obtenció de mapes de règim d'humitat del sòl de la conca, a escala 1:50000, els quals
permeten establir mediante simució els règims d'humitat del sòl en diferents escenaris de canvis
meteorològics.
El model TOPLATS ha sigut utilitzat en l'estimació de l'humitat del sòl en diferents usos del sòl. Aquest
model fou calibrat amb les equacions del filtre Kalman estès (EKF), que deriven de la minimització del
quadrat de la diferència entre els valors reals i els estimats (Goegebeur & Pauwels, 2007). Aquesta
metodologia interrelaciona correctament els valors de pluja, humitat del sòl, escolament i infiltració,
essent els valors d'humitat els que més s'aproximen als reals. Els resultats mostren que aquest filtre és
una eina útil per estimar el volum d'aigua del sòl emmagatzemada en conques a escala puntual,
assegurant una aplicació correcta del model hidrològic.
Per la modelització del comportament de l'humitat del sòl i diferents components del balanç hídric
s'utilitzà el modelo TOPLATS (Famiglietti & Wood, 1994). El model de simulació TOPLATS permite
simulà acceptablement el comportament de l'humitat del sòl. Els resultats de infiltració, escolament,
intercepció, evapotranspiració de referència i temperatura del sòl són correctes. Les diferències existents
entre valors simulats i observats són: l'humitat del sòl no sobrepassa el 5%, la infiltració fluctua entre 4%
i 15%, la diferència entre els valors reals i simulats d'evapotranspiració, depèn de l'estació de l'any,
essent 1mm a l'hivern i 2.7 mm a l'estiu. La temperatura varia entre 0.01ºC i 3.5ºC. El model calibrat
prediu amb precisió el comportament de les diferents components del balanç hídric. Respecte als valors
mesurats d'aigua de drenatge correspon al 11-41 % de la pluja total.
Respecte al balanç d'aigua en el sòl (ΔSW), els valors són negatius durant cert període de l'any, arribant a
valors crítics els mesos secs. La recuperació de humitat del sòl durant la resta de mesos succeeix de
manera parcial. A la part mitja de la conca, alguns mesos els valors d'humitat del sòl s'acosten a
condicions de punt de marchites (ecosistema submediterrani). A la part alta de la conca el sòl conserva
humitat (ecosistema subalpí). Els valors de cabal trobats corresponen a aportacions per escolament el
cuals són molt baixos. La majoria de les sortides es deuen a evapotranspiració, intercepció, infiltració i
drenatge (en ordre de importància).
El principal objetivo de esta investigación es estudiar la dinámica hidrológica de una cuenca Mediterránea
afectada por los cambios de uso del suelo, mediante el monitoreo del suelo y el agua superficial. Dicho objetivo
se ha abordado a partir de la medición de componentes del balance hídrico para diferentes tipos de cobertura y
suelo, considerando regimenes de humedad y temperatura de transición.
Este estudio se ha realizado en la cuenca de la Ribera Salada (Prepirineo meridional Catalán, NE España) de
222.5 km2, con un intervalo altitudinal de 420 a 2385 m y predominio de pendientes entre 12 - 25 % y 25 - 50
%. El sustrato consiste en conglomerados calcáreos masivos, calcilutitas y limos. La precipitación anual es de
507 y 763 mm. Los suelos són poco profundos, calcáreos y pedregosos, siendo en su mayoría Inceptisols
(Typic Calciusteps, Typic Haploustepts) y Entisols (Typic Ustifluvents, Typic Udorthortents). En las partes
altas de la cuenca los suelos son más húmedos, debido al aumento de la precipitación, allí ocurren procesos de
descarbonatación del suelo. Predomina el uso forestal, con ecosistemas de ribera, subalpinos y vegetación
submediterránea. Algunas áreas se dedican al cultivo de patatas, cereal y pastos. Una de las características más
importantes de esta cuenca es los importantes cambios de uso del suelo sufridos en los últimos 50 años, debido
al abandono de las masías y cultivos tradicionales.
Se seleccionaron ocho sitios de muestreo, considerando las siguientes coberturas: Quercus ilex, bosque de
ribera, Pinus sylvestris, pastos, cultivo (cereal-patata) y Pinus uncinata. A partir del año 1997 hasta 2005, se
han venido monitoreando el contenido de humedad del suelo, escorrentía y caudales. Desde 2004 se vienen
tomando datos drenaje. Las variables meteorológicas se miden la estación Lladurs perteneciente a la XAC
(Xarxa Agrometeorológica de Cataluña).
Los resultados obtenidos par un period de tres años muestran una predominancia del regimen de humedad
ústico (SSS, 2006), o xérico en los años más secos. Se utilizaron los modelos de simulación NSM "Newhall
simulation model" (Newhall, 1976) y JSM "Jarauta simulation model" (Jarauta 1989) en la modelización de
regimenes de humedad y temperatura del suelo. NSM (Newhall,1976) tiende a sobre estimar el régimen de
humedad del suelo. Por contra, JSM (Jarauta, 1989) simula de forma correcta el régimen de humedad del suelo
(SSS, 2006) presente en la cuenca, funcionando mejor bajo condiciones medias de humedad del suelo. Ambos
modelos simulan de forma correcta el régimen de temperatura de los suelos. Predomina un régimen de
temperatura mésico-térmico, con tendencia a térmico para los años secos. A pequeña escala la profundidad del
suelo, pendiente, pedregosidad y alta porosidad del suelo son factores que hacen variar el régimen de humedad
del suelo. La información de suelo y clima, complementada mediante SIG, permitió obtener mapas de régimen
de humedad del suelo para la cuenca, a una escala 1:50000, los cuales permiten establecer mediante simulación
los regimenes de humedad en el suelo bajo diferentes escenarios de cambios meteorológicos.
El modelo TOPLATS ha sido utilizado en la estimación de la humedad en el suelo para diferentes usos del
suelo. Este modelo fue calibrado con las ecuaciones del filtro Kalman extendido (EKF), que se derivan de la
minimización del cuadrado de la diferencia entre los valores reales y los estimados (Goegebeur & Pauwels,
2007). Esta metodología interrelaciona correctamente los valores de lluvia, humedad en el suelo, escorrentía y
infiltración, siendo los valores de humedad los mas ajustados a los valores reales. Los resultados muestran que
este filtro es una herramienta para estimar el volumen de agua en el suelo almacenada en las cuencas a escala
puntual, asegurando una aplicación correcta del modelo hidrológico.
Para la modelización del comportamiento de la humedad del suelo y los diferentes componentes del balance
hídrico se utilizó el modelo TOPLATS (Famiglietti & Wood, 1994). El modelo de simulación TOPLATS
permite simular aceptablemente el comportamiento de la humedad del suelo. Los resultados para infiltración,
escorrentía, intercepción, evapotranspiración de referencia y temperatura del suelo son correctos. Las
diferencias existentes entre valores simulados y observados son: la humedad del suelo no sobrepasa el 5%, la
infiltración fluctúa entre 4% y 15%, la diferencia entre los valores reales y simulados de evapotranspiración,
depende de la estación del año, siendo 1mm en invierno y 2.7 mm en verano, la temperatura varia entre 0.01 ºC
y 3.5ºC. El modelo calibrado predice con precisión el comportamiento de las diferentes componentes del
balance hídrico. Respecto a los valores medidos para agua de drenaje corresponde al 11-41 % de la lluvia total.
Respecto al balance de agua en el suelo (ΔSW), los valores son negativos para un corto periodo del año,
alcanzando valores críticos en meses secos. La recuperación de humedad del suelo para el resto de los meses
ocurre de manera parcial. En la parte media de la cuenca, para algunos meses los valores de humedad del suelo
son cercanos a condiciones de punto de marchites permanente (ecosistema submediterráneo). En la parte alta
de la cuenca el suelo conserva condiciones intermedias de humedad (ecosistema subalpino). Los valores de
caudal encontrados corresponden a los aportes por escorrentía, los cuales son muy bajos. La mayor parte de las
salidas ocurren por evapotranspiración, intercepción, infiltración y drenaje (en orden de importancia).
The main aim of this research is to study the hydrological dynamics of a Mediterranean mountain basin
affected by land use changes, by means of the monitoring of soil and surface water. This aim has been
reached by measuring and simulating hydric balance components of different soils and under different
vegetational types, considering water and temperature transition regimes.
This research was done in Ribera Salada basin (Catalan Pre Pyrenees, NE Spain), with an area of 222.5
km2, altitudes between 420 and 2385 m, with predominance slopes between 12 - 25 % and 25 - 50 %. The
substrate consists of massive calcareous conglomerates, calcilutites and limestones. Main annual
precipitation are 507 to 763 mm. Soils are shallow, calcareous and stony, being most of them Inceptisols
(Typic Calciusteps, Typic Haploustepts) and Entisols (Typic Ustifluvents, Typic Udorthortents). In the
upper and moister part of the basin soil decarbonatation takes place. Forest use is predominant, going
from brook forest environments to subalpine and submediterranean vegetation. Agricultural uses include
mainly the growing of cereals, potatoes and pastures. One of the most important characteristics in this
basin are the significant soil use changes in the last 50 years, due to the abandonment of farms and
traditional crops.
Eight sites were studied, corresponding to soils under Quercus ilex, brook forest, Pinus sylvestris, pasture,
crops (cereal-potatoes) and Pinus uncinata. From 1997 until 2005, soil moisture, run-off, water flow and
interception were monitored. From 2004 on, drainage data has been recorded. Meteorological variables
were measured by means of a complete Lladurs meteorological station, belonging to XAC (Catalan
Agrometeorological Network).
The obtained results to three years show the predominance of ustic moisture regime (SSS, 2006), or xeric
during the driest years. The simulation models NSM "Newhall simulation model" (Newhall, 1976) and
JSM "Jarauta simulation model" (Jarauta 1989) were used to represent soil moisture and temperature
regimes. NSM estimates a higher level of soil moisture regimes than observed. On the contrary, JSM
simulates correctly soil moisture regimes, working better under intermediate soil moisture conditions.
Both models simulate correctly the soil temperature regimes, being mesic-thermic to thermic during the
driest years. At detailed scale (plot observation), soil depth, slope, stone amount and high soil porosity are
factors that affect the soil moisture regimes. Soil and climate information, implemented through a GIS,
allowed us to obtain soil moisture regime maps of the basin at a 1:50000 scale, which are very useful to
simulate soil moisture regimes in different scenarios of meteorological changes.
The TOPLATS model, when used to estimate soil moisture under different cover types, was calibrated
with Extend Kalman filter (EKF) equations derived through a minimization of the square difference
between the true and estimated model state (Goegebeur & Pauwels, 2007). This methodology interrelates
correctly rainfall, soil moisture, runoff and infiltration. Among them, the obtained soil moisture values
corresponded the best to observed data. The results show that it is a useful tool to estimate soil water
volume stored in basins at a point scale, ensuring a correct application of this hydrological model.
To model soil moisture behaviour and the different hydric balance components, the TOPLATS model
(Famiglietti & Wood, 1994) was used. TOPLATS model simulates correctly the soil moisture behaviour.
The differences between observed and simulated values are the following: soil moisture does not surpass
5%; the infiltration fluctuates between 4% to 15%; in evapotraspiration depends on the season being
between 1 mm in winter to 2.7 mm in summer, soil temperature values difference fluctuates between
0.01ºC and 3.5ºC.The calibrated model predicts precisely the behaviour of different hydric balance
components. The measured water drainage amount is 11-41 % of total rain.
The observed and simulated soil water storage in the basin (ΔSW), has negative values during the driest
months. Soil moisture recovery during the rest of the months is only partial. In the medium part of the
basin, occupied by submediterranean ecosystems, soil moisture values are closer to drought conditions
during some months of the year. In the highest part of the basin (subalpine ecosystems) there are
intermediate soil moisture conditions in dry periods. Most part of water outputs are due to
evapotranspiration, interception, infiltration and drainage, in decreasing order of importance. Run-off
values are very low.

Stodmarsh National Nature Reserve includes the largest reedbed in Southern England and is an important habitat for breeding waders and several rare bird species, including Bitterns. A succession of drought years in the 1990s brought the issue of the hydrology and water requirements of the wetland to the attention of managers and there is concern about future water supplies to the reserve. This study aims to calculate the amount of water required by the site in order to maintain optimum habitat conditions. The greatest area of uncertainty in the water balance is the evapotranspiration rate of the reedbeds and therefore a secondary aim is to increase understanding of this flux. Detailed hydrological measurements were carried out over two years to establish the water balance of the site. Evapotranspiration was measured using the Bowen ratio technique, accompanied by additional physiological and meteorological measurements. Results showed that evapotranspiration from reeds was generally less than reference evapotranspiration and that stornatal resistance was the most important factor controlling evapotranspiration rates. The hydrology of the site was modelled using a thirty year historical data series to quantify the return periods of flood and drought conditions of different severity. These were used to predict water resource requirements and availability and confidence limits were attached to the results. In 70% of years, summer deficits in the rainfall-evapotranspiration balance require the addition of water from the Lampen Stream. In 10% of these years, the entire surmner discharge of the Lampen Stream would be insufficient to meet site water requirements and an additional source of water is required. Competition with other water users and limits on abstraction will increase the number of years an additional water source is required. In addition future climate change is likely to increase summer water requirements whilst decreasing resource availability.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Includes bibliographies.
by William Kensett Nuttle.
Ph.D.

Urbanization is continuously growing all over the world. Both developing and developed countries encourage rapid expansion for increased growth and production. However, urbanization in combination with climate change can lead to higher chances of extreme flood events. Mankind always settled around rivers and floodplains that are naturally more flood prone areas, making stormwater modeling and urban planning indispensable for safety and reduction of flood risk.Until now many important studies have been conducted on the dangers of living in floodplains of urbanized cities, but most of them are about developing countries such as Bangladesh or Vietnam, leaving a noticeable gap in the developed world. However, all these researches share one thing in common as they do not take into account the interactions between water and society by ignoring the constantly changing human factor.Socio-hydrology is a new branch of hydrology closely related to Integrated Water Resource Management (IWRM) that tries to explore this dynamic relationship. This study explores the historical evolution of a highly urbanized industrial city in Finland and attempts to understand both the human and engineering effects of urbanization. The city of Pori is the most flood prone area in Finland, which makes for an important study that will yield important results and possible recommendations for future research, while for the first time incorporating socio-hydrology, the human factor and flood risk in a major European city.This is an empirical project with data collected from various different sources put all together for the first time that could change the perceptions of both inhabitants and scientists and be the basis for a more thorough, modeling based research in the future. The research question of this dissertation is how socio-hydrological dynamics have affected flood risk changes over the past decades in the city of Pori.
Urbaniseringen växer fortlöpande över hela världen. Både industriländer och utvecklingsländer befrämjar snabb expansion för ökad tillväxt och produktion. Dock leder urbanisering i kombination med klimatförändring till högre risk för extrema översvämningar. Människor har i alla tider bosatt sig runt vattendrag och flodslätter som naturligt är mer benägna att översvämmas, något som gör att dagvattenhantering och stadsplanering är absolut nödvändigt för ökad säkerhet och reducerad översvämningsrisk.Fram tills nu har många viktiga studier genomförts som behandlar farorna för människor bosatta i urbaniserade städer intill flodslätter, men de flesta av dem har utgått från utvecklingsländer som Bangladesh eller Vietnam, något som lett till en märkbar avsaknad av information gällande industri-länder. Gemensamt för dessa studier är dock att de ignorerar den ständigt föränderliga mänskliga faktorn och på så sätt inte tar i beaktning interaktioner mellan vatten och samhälle.Socio-hydrologi är en ny gren inom hydrologi som är nära besläktad med Integrerad Vattenresurs-förvaltning och som försöker utforska detta dynamiska samspel. Denna studie undersöker den historiska utvecklingen av en starkt urbaniserad industristad i Finland och försöker tolka de mänskliga och tekniska effekterna av urbanisering. Staden Pori (Björneborg på svenska) är den mest översvämningsbenägna platsen i Finland, vilket gör denna studie till ett viktigt arbete för att ta fram betydelsefulla resultat och eventuella rekommendationer för framtida forskning. Dessutom inkorporeras socio-hydrologi, den mänskliga faktorn och översvämningsrisk för första gången i forskning gällande en större europeisk stad.Detta är ett empiriskt projekt med data insamlat från olika källor som sammanställts för första gången och som kan förändra både invånares och forskares synsätt, samt vara en grund för mer utförlig och modellbaserad forskning i framtiden. Frågan som denna avhandling försöker besvara är hur socio-hydrologisk dynamik har påverkat förändringar av översvämningsrisker i staden Pori i Finland över de senaste årtiondena.

A distributed hydrological rainfall-runoff model has been developed using a GIS integrated with a dynamic programming module (PCRaster). The model has been developed within the framework of the EU-project TWINBAS at IVL Swedish Environmental Research Institute, and is intended for use in WATSHMAN – a tool for watershed management developed at IVL. The model simulates runoff from a catchment based on daily mean values of temperature and precipitation. The GIS input data consist of maps with soil type, land-use, lakes, rivers and a digital elevation model. The model is a hybrid between a conceptual and a physical model. The snow routine uses the degree-day method, the evapotranspiration routine uses the Blainey-Criddle equation, the infiltration routine is based on Green-Ampt, groundwater is modelled assuming a linear reservoir and the flow routing is done with the kinematic wave equation combined with Manning’s equation.

The GIS and the hydrologic model are embedded in one another, allowing calculation of each parameter in each grid cell. The output from the model consists of raster maps for each time step for a pre-defined parameter, or a time series for a parameter at a specified grid cell. The flow network is generated from the digital elevation model and determines the water flow on the grid scale. The smallest possible grid size is thus obtained from the resolution of the digital elevation model. In this implementation the grid size was 50 m x 50 m. The raster structure of the model allows for easy use of data from climate models or remotely sensed data.

The model was evaluated using the River Kölstaån catchment, a part (110 km2) of the Lake Mälaren catchment, which has its outflow in central Stockholm, Sweden. The integration of the GIS and the hydrologic model worked well, giving significant advantages with respect to taking lakes and land-use into account. The evaluation data consisted of observed run-off for the period 1981 to 1991. The result from the calibration period shows a great variation in Reff (Nash & Sutcliffe) between the years, the three best years having Reff-values of 0.70 – 0.80. The Reff-value for the entire calibration period was 0.55 and 0.48 for the validation period, where again there was great variation between different years. The volume error was 0.1 % for the calibration period and -21 % for the validation period. The evapotranspiration was overestimated during the validation period, which is probably a result of excess rain during the calibration period. The results are promising and the model has many advantages – especially the integrated GIS-system – compared to the present WATSHMAN model. It could be further developed by introducing a second groundwater storage and refining the evapotranspiration and infiltration routine. Given the promising results, the model should be evaluated in other larger and hillier areas and preferably against more distributed data.

En helt distribuerad GIS-baserad hydrologisk modell för modellering i avrinningsområden på lokal/regional skala har byggts upp i PCRaster. Arbetet utfördes på IVL Svenska Miljöinstitutet AB inom ramen för EU-projektet TWINBAS, som har som mål att identifiera kunskapsluckor inför implementeringen av EU:s ramdirektiv för vatten. Modellen är tänkt att användas i WATSHMAN (Watershed Management System), IVLs verktyg för vattenplanering i avrinningsområden där bland annat källfördelningsberäkningar och åtgärdsanalyser ingår. Den uppbyggda modellen är en hybrid mellan en fysikalisk och en konceptuell hydrologisk modell och predikterar vattenföring på pixelnivå i avrinningsområden. Simuleringen drivs av dygnsmedelvärden för temperatur och nederbörd och modellen tar hänsyn till markanvändning, jordart, topografi och sjöar. De modellekvationer som används är grad-dagsmetoden för snö, Blainey-Criddle för evapotranspiration, Green-Ampt för infiltration, linjärt magasin för grundvatten och Mannings ekvation för flödesrouting.

Det geografiska informationssystemet och den hydrologiska modellen är helt integrerade, vilket gör att alla parametervärden beräknas för varje enskild pixel. Som utdata ger modellen en rasterkarta för varje tidssteg för en i förväg bestämd parameter, eller tidsserier över parametervärden i definierade punkter. Vattnet transporteras i ett utifrån höjdmodellen genererat flödesnätverk och vattnets flödesväg bestäms därmed på pixelnivå. Minsta möjliga pixelstorlek bestäms således utifrån höjdmodellens upplösning, och var vid denna tillämpning 50 m gånger 50 m. Modellens uppbyggnad med raster gör det enkelt att använda data från klimatmodeller eller fjärranalys.

Avrinningsområdet för Kölstaån, ett biflöde till Köpingsån i Mälardalen, har använts för att utvärdera modellen. Integreringen av GIS och hydrologisk modell fungerade mycket väl och gav stora fördelar t ex vad gäller att ta hänsyn till sjöar och markanvändning. Modellen kalibrerades med data från åren 1981 till 1986 och det erhållna volymfelet var då 0,1 % och Reff-värdet (Nash & Sutcliffe) 0,55. Stora variationer erhölls dock mellan åren; för de tre bästa åren låg Reff-värdet mellan 0,70 och 0,80. Ett mycket kraftigt nederbördstillfälle samt regleringar i huvudfåran av vattendraget ligger troligtvis bakom de mindre väl beskrivna åren. Även under valideringsperioden (1987 till 1991) fungerade modellen väl, så när som på att avdunstningen överskattades på vårarna (antagligen beroende av det stora regnet under kalibreringen), och Reff-värde och volymfel hamnade på 0,48 respektive -21 %, även här med stora variationer mellan åren. Resultaten är lovande och modellen har många fördelar jämfört med den nuvarande WATSHMAN-modellen. Den skulle kunna förbättras ytterligare genom att dela upp grundvattnet i två magasin samt förfina evapotranspirations- och infiltrationsrutinerna. Den höjdmodellsbaserade modellen bör utvärderas även i andra mer kuperade områden samt mot mer distibuerade data.

Thesis (Ph. D. - Renewable Natural Resources)--University of Arizona, 2001.
Page 189 missing in original volume. There are two pages numbered 190. Includes bibliographical references (leaves 329-334).

As projections of future climate raise concerns over water availability and extreme hydrological events, global hydrology models are increasingly being employed to better understand our global water resources and how they may be affected by climate change. Being a relatively recent development in hydrological science, global hydrology modelling has not yet undergone the same level of assessment and evaluation as catchment scale hydrology modelling. Until now, global hydrology models have presented just one deterministic model output for use in scientific research. Recently, multi-model ensembles have compared these outputs for different global models, but this has been done prematurely as the uncertainties within individual models have yet to be understood. This study demonstrates a rigorous uncertainty investigation of the 123 parameters within the Mac-PDM global hydrology model over 21 global river catchments. Mac-PDM was selected for its relative simplicity amongst global hydrology models, and its suitability for application using high performance computer clusters. A new version of the model, Mac-PDM.14 is provided, with updated soil and vegetation classifications. This model is then subjected to a 100,000 parameter realisation Generalised Likelihood Uncertainty Estimation (GLUE) experiment, requiring 40 days of high performance computing time, and outputting over 2Tb of data. The top performing model parameterisation from this experiment provides an annual average error of 47% when compared to observed records, a 45% improvement over the previous version of the model, Mac-PDM.09. Given the computational expense of such an experiment, smaller sample sizes of parameter realisations are explored. Whilst the top performing parameterisation in a sample size as small as 1,000 can perform almost as well as that from 100,000 parameterisations, the number of good parameterisations is fewer, and the range of model uncertainty may therefore be significantly underestimated. Mac-PDM.14 is shown to have a lower mean absolute relative error than all models involved in both the Water and Global Change (WATCH) project and the Inter-Sectoral Impacts Model Intercomparison Project (ISI-MIP). Parameter uncertainty is compared to model uncertainty, and the uncertainty range between the models within the WATCH and ISI-MIP projects is comparable to the parameter uncertainty within Mac-PDM.14. Catchment specific calibrations of the global hydrology model are explored, and it is demonstrated that the model performance is improved by 22 to 92%, for the Niger and the Yangtze respectively, with catchment specific parameter values over a global calibration. Approximate Bayesian Rejection is applied to explore the catchment specific parameter values that result in good parameter performance. Few trends can be identified from this analysis, which suggests that Mac-PDM may be over-parameterised. Catchment specific calibrations in both high latitude and arid to semi-arid regions show significant improvement over global calibration, which indicate a deficiency in model structure; the addition of a glacier component to Mac-PDM is recommended. Model calibrations are validated using the ISI-MIP forcing dataset, and the best model performance gives an error of 44%. This is a betterment on the performance with the WATCH forcing data used in calibration, and so implies that models not need to be recalibrated every time new forcing datasets are employed. This research highlights that the performance of global hydrology models can be significantly improved by running a parameter uncertainty assessment, and that in catchment scale studies, catchment specific calibration should be carefully considered. Furthermore, the uncertainty within individual global hydrology models is an important consideration that should not be overlooked as these models are increasingly included in ensembles and interdisciplinary studies.

Despite the importance of the hydrological regime for the functioning of wetland environments, the understanding of hydrological processes, particularly evaporative dynamics and clay soil moisture fluxes, is limited and the original research outlined in this thesis constitutes a real contribution to further the scientific understanding of wetland systems. Two lines of investigation are followed based upon field experiments and monitoring of groundwater and ditch water levels together with soil moisture over time and space. The first investigation assesses the effectiveness of the Environmentally Sensitive Area (ESA) scheme of the North Kent Marshes to achieve its objective of soft moist ground conditions through the manipulation of ditch water levels. Results demonstrate that due to the clay soil texture and low hydraulic conductivity of the marsh substrate, little relationship exists between the position of ditch water levels and groundwater. Flooding the marsh surface with brackish ditch water does promote high surface soil moistures and optimal habitat for waterfowl. However the deleterious effects upon soil structure and floristic diversity by flooding large areas need to be taken in consideration for the sustainable management of the wetland. Results from this investigation prove that precipitation and evaporation are the dominant fluxes of water, and so the second investigation focused upon the loss of water from the wet grassland by evaporation. There are two foci of research. Firstly the relationship between surface resistance and soil moisture content is examined, so that 'correct' surface resistance values could be input to the Penman Monteith method to compute actual evaporation according to the wetness of the marsh soil. Research results show a complex relationship with decreasing rates of actual evaporation below potential rates with soil moisture loss, and a functional relationship has been quantified. Secondly the actual evaporative water loss of the wetland was determined taking into account the small-scale heterogeneity of surface wetness conditions. The Weighted Penman Monteith (WPM) approach was followed referencing results against data by the Bowen Ratio Energy Balance method. Research results show that the WPM method could be used to compute the actual evaporation loss, however the adoption of the Priestly-Taylor approach with suitable values of a is a simpler method and of equal accuracy.

Studies of glacier-hydrology have focused on clean Alpine glaciers, and recently ice sheet outlet glaciers, but there are few studies on debris-covered glaciers. It is known debris affects ablation rates, and that debris-covered glaciers evolve differently to their debris-free counterparts, but how the debris influences the hydrology is poorly understood. This thesis aims to understand the influence of the debris on the hydrological system and water balance of Miage Glacier, Western Italian Alps. The supraglacial hydrology was studied by modelling ablation using a distributed energy balance melt model, and measuring supraglacial stream discharges; the structure and evolution of the englacial and subglacial network was investigated using dye tracing and water chemistry monitoring; and the proglacial runoff was examined through detailed hydrograph analysis. Glacier velocity measurements were used to investigate the debris’ influence on the glacier dynamics. High ablation rates occurred on clean ice and beneath thin debris on the upper glacier, resulting in large supraglacial streams which led into an efficient drainage system. Glacier velocities had a greater magnitude and variability close to the upper glacier moulins. Thick debris on the lower glacier reduced ablation, and consequently the discharge of supraglacial streams and efficiency of the hydrological network. Despite locally inefficient subglacial drainage, glacier velocities on the lower glacier remained subdued, partly because the debris attenuated water inputs. This attenuation reduced the occurrence of high amplitude diurnal cycles in the proglacial runoff and confined them to particularly warm weather. Lag times from peak air temperature to peak runoff were long relative to comparable debris-free glaciers. Evaporation of rainfall from debris-surfaces was high, and dependant on the debris permeability, suggesting this is an important water balance component. Under climate warming, it is predicted the ablation of Miage Glacier will increase, but this may be negated given an increase in debris cover.

Throughout history there has been a close relationship between hydrological and social processes. Most of early civilizations around the world developed thanks to the accessibility to rivers and their water resources. However, traditional hydrological approaches have not been able to capture this observed interaction and have ignored for too long the human-driven impacts in the hydrological system and how they, in turn, shape the hydrological conditions that have been commonly observed. The present research develops a new conceptual model with the intention to capture the two-way interactions between societies and their responses under extreme hydrological events, both floods and droughts. This conceptualization accounts for the observations that societies accumulate memory (increase the level of awareness) after an extreme events. Based on the accumulation of societal memory, the human system (societies) takes decisions about water management, thus impacting the hydrological system (rivers). When no extreme hydrological events are registered, societal memory decays at a certain rate and then new decisions are taken over the water management of the hydrological system. Inspired by the extreme droughts and floods events observed in the three last decades in the catchment of the Brisbane River in Australia, the aforementioned conceptualization is applied. Results indicated that the simple proposed conceptual model is able to capture the interactions between the human and the hydrological system. Additionally, the model exposes that societal memory is the driver of the human system and is the main reason for societies to create impacts on the natural conditions of the catchment. At the same time, this conceptualization demonstrated that water management decisions based on the accumulation of societal memory can actually create an exacerbation of the potential damages associated to extreme hydrological events. Finally, the development of this new approach points out the strong necessity to acquire further insights to improve the understanding of the interplay between hydrological and social processes.
Genom historien har det funnits en nära relation mellan hydrologiska och sociala processer. De flesta tidiga civilisationer runt om i världen utvecklades tack vare tillgången till floder och deras vattenresurser. Traditionella hydrologiska metoder har emellertid inte lyckats fånga denna observerade interaktion och har alltför länge ignorerat de mänskligt drivna effekterna i det hydrologiska systemet och hur de i sin tur formar de hydrologiska förhållandena som ofta observerats. Denna forskning har utvecklat en ny konceptuell modell med avsikt att fånga tvåvägsinteraktionen mellan samhällen och deras respons under extrema hydrologiska händelser, både översvämningar och torka. Denna konceptualisering baseras på observationen att samhällen ackumulerar minne (ökar medvetenheten) efter en extrem händelse. Baserat på ansamling av samhällets minne fattar det mänskliga systemet (samhällen) beslut över vattenhushållning, vilket påverkar det hydrologiska systemet (floder). När inga extrema hydrologiska händelser registreras, avklingar samhällsminnet med en viss hastighet och sedan fattas nya beslut om vattenhushållningen i det hydrologiska systemet. Den konceptuella modellen har tillämpats på Brisbaneflodens avrinningsområde, i Australien, med anledning av den extrema torka och stora översvämningar som observerats under de tre senaste decennierna. Resultaten tyder på att den enkla föreslagna konceptuella modellen kan fånga samspelet mellan människa och hydrologiska system. Dessutom visar den att ett samhälles minne är drivkraften för det mänskliga systemet och är den främsta orsaken till att samhällen gör inverkan på de naturliga förhållandena i avrinningsområdet. Samtidigt visar konceptualiseringen att denna typ av vattenförvaltning, som baseras på samhällsminnet, faktiskt kan förstärka de potentiella skador som kan uppkomma i samband med extrema hydrologiska händelser. Slutligen framhåller utvecklingen av denna nya metod det stora behov som finns för att förbättra förståelsen av samspelet mellan de hydrologiska och sociala processerna.

For this dissertation I studied groundwater and surface water interactions in the Kenai Lowlands, Alaska. In particular, I examine two important aspects of groundwater and surface water interactions: 1) Groundwater's influence on surface-water temperature; and 2) Groundwater's role in forming hydrologic flow paths that can connect uplands to streamside wetlands and streams. Chapter 2 investigates the controls on stream temperature in salmon-bearing headwater streams in two common hydrogeologic settings: 1) drainage-ways, which are low-gradient streams that flow through broad valleys; and 2) discharge-slopes, which are high gradient streams that flow through narrow valleys. The results from chapter 2 showed significant differences in stream temperatures between the two hydrogeologic settings. Observed stream temperatures were higher in drainage-way sites than in discharge-slope sites, and showed strong correlations as a continuous function with the calculated topographic metric flow-weighted slope. Additionally, modeling results indicated that the potential for groundwater discharge to moderate stream temperature is not equal between the two hydrogeologic settings, with groundwater having a greater moderating effect on stream temperature at the low gradient drainage-way sites. Chapter 3 examines the influence of groundwater on juvenile coho salmon winter habitat along the Anchor River. Two backwater habitats were selected from the larger set of 25 coho overwintering sites from a previous study for an in-depth hydrologic analysis. The results from chapter 3 showed that the type of groundwater discharge (i.e., focused versus diffuse groundwater discharge) can play an important role in determining habitat suitability in these backwater sites. During winter, focused discharge from a local groundwater seep maintained higher surface-water temperatures and higher concentrations of dissolved oxygen compared to the site with more diffuse groundwater discharge. Chapter 4 investigates the linkages along hydrologic flow paths among alder (Alnus spp.) stands, streamside wetlands, and headwater streams. Chapter 4 tested four related hypotheses: 1) groundwater nitrate concentrations are greater along flow paths with alder compared to flow paths without alder; 2) on hillslopes with alder, groundwater nitrate concentrations are highest when alder stands are located near the streamside wetlands at the base of the hillslope; 3) primary production of streamside wetland vegetation is N limited and wetlands are less N limited when alder stands are located nearby along flow paths; and 4) stream reaches at the base of flow paths with alder have higher nitrate concentrations than reaches at the base of flow paths without alder. The results from chapter 4 showed that groundwater nitrate concentrations were highest along flow paths with alder, however no difference was observed between flow paths with alder located near versus alder located further from streamside wetlands. Vegetation had a greater response to N fertilization in streamside wetlands that were connected to flow paths without alder and less when alder stands were near. Finally, higher nitrate concentrations were measured in streams at the base of flow paths with alder. The combined results of this dissertation showed that, in the Kenai Lowlands, groundwater and surface water interactions have a direct influence on the local ecology and that a fundamental understanding of the hydrology can aid in the successful management and protection of this unique and important ecosystem.

Doutoramento em Geociências
In Portugal, there is an old tradition in using clayey materials for therapeutic purposes. They are applied in pelotherapy, at several beaches of the Atlantic coast in the form of clay-sea water mixtures (peloids) to treat skin and rheumatic diseases. During many generations, peloids have been applied without scienti c studies that prove their therapeutic validity. In the last decade, the Portuguese scienti c community has become increasingly more interested in assessing the properties that make clayey materials suitable for therapeutic purposes. The abundance of clayey formations and the established practices of medical hydrology in our country turned this interest into a new perspective of application. The studied materials include di erent clays (in age and origin) mainly collected from well-known Mesozoic-Cenozoic formations, in some cases outcropping at beaches where empirical applications occur. This thesis focus in the study of silt-clay fraction (< 63 m).To determine their suitability for therapy, compositional, physicochemical, technological, thermal and rheological properties were assessed. Conventional techniques (XRD, XRF and Sedigraph) were used to assess compositional features of silt-clay fraction. Electron microscopy (SEM, VPSEM, HREM) was used to study the micromorphology and composition of clay fraction (< 2 m). Physicochemical properties (cation exchange and speci c surface) were assessed using the Ammonium Acetate and BET methods. Technological properties (plasticity and abrasivity indices) were assessed using the Atterberg limits and Einlehner abrasion tests. Thermal properties (speci c heat and cooling kinetics) were estimated by DSC analysis and cooling tests. Pharmacotechnical tests (compressibility index, sediment volume and Brook eld viscosity) were used to assess the powder owability as well as the physical stability and viscosity of clay-water dispersions. We selected as suitable Portuguese clays for health applications the samples A-Pe, A-Be2, A-Sd, J-Fr , M-To, C-Lu1, C-Lu2, Pl-Ba, M-Ga and J-Ab because they represent safe materials, with an adequate composition, good technological, physicochemical and thermal properties for application, also presenting an adequate rheology when dispersed in water. Their most relevant characteristics are the high clay minerals content, abundant smectite, illite and kaolinite, and safe hazardous concentrations. They also showed moderate capacity to exchange Ca 2+, high plasticity, low abrasivity, high speci c heat and slow cooling kinetics. They evidenced fair powder owability and good potential to formulate viscous dispersions when stabilized. Because the majority of the assessed characteristics are in accordance with those presented by clays applied in European spas for pelotherapy, we considered this group of clays also suitable for medical hydrology treatments in Portuguese spas.
Em Portugal, o uso de materiais argilosos para fins terapêuticos é uma prática que persiste desde a antiguidade. A aplicação (peloterapia) é realizada em algumas praias do litoral Atlântico sob a forma de pastas de argila misturada com água do mar (pelóide). Ao longo de várias gerações os pelóides têm sido utilizados para tratar doenças dermatológicas e reumáticas sem estudos científicos que comprovem a sua validade terapêutica. Na última década, a comunidade científica Portuguesa tem vindo a interessar-se cada vez mais pela avaliação das propriedades que tornam os materiais argilosos adequados para peloterapia. A abundância de formações argilosas e as práticas de hidrologia médica reconhecidas no nosso pais transformaram este interesse numa nova perspectiva de aplicação. Para este estudo, foram amostradas diferentes argilas (em idade e origem) provenientes sobretudo de formações Mesozóicas-Cenozóicas bem conhecidas. Algumas destas formações a oram em praias onde a aplicação tradicional de argila ocorre. Esta tese foca-se no estudo da fracção silto-argilosa (< 63 m) dos materiais amostrados. A avaliação das suas propriedades composicionais, físico-químicas, tecnológicas, térmicas e reológicas permitiu estimar a sua aplicabilidade terapêutica. Técnicas convencionais (DRX, FRX, Sedigraph) foram utilizadas para estudar a composição da fracção silto-argilosa. A microscopia electrónica (SEM, VPSEM e HREM) permitiu estudar a micromorfologia e a composi ção da fracção argilosa (< 2 m). As propriedades físico-químicas (troca catiónica, superfície específica) foram determinadas pelos métodos do Acetato de Amónio e BET. As propriedades tecnológicas (plasticidade e abrasividade) foram avaliadas utilizando os limites de Atterberg e teste de abrasão de Einlehner. As propriedades térmicas foram determinadas recorrendo á análise térmica calorimétrica (DSC) e cinética de arrefecimento. Ensaios de tecnologia farmacêutica (compressibilidade, volume de sedimento e viscosidade de Brook eld) foram utilizados para o estudo da uidez de pós assim como da estabilidade física e viscosidade das dispersões argila-água. Foram seleccionadas como argilas Portuguesas com aplicabilidade em saúde as amostras A-Pe, A-Be2, A-Sd, J-Fr , M-To, C-Lu1, C-Lu2, Pl-Ba, M-Ga and J-Ab por serem materiais seguros e de composição adequada, com propriedades físico-químicas, tecnológicas e térmicas benéficas para aplicação. Estas argilas apresentam igualmente uma reologia apropriada quando dispersas em água. As suas características mais relevantes são o elevado conteúdo em minerais de argila, abundância de esmectite, ilite e/ou caulinite e a toxicidade aceitável. Apresentam uma capacidade razoável para trocar catiões, destacando-se o Ca 2+, assim como elevada plasticidade, baixa abrasividade, elevado calor específico e cinética de arrefecimento lenta. Por fim, evidenciaram uma uidez de pó razoável e capacidade para originar dispersões viscosas quando estabilizadas. Uma vez que a maioria das características avaliadas nas argilas Portuguesas estão de acordo com aquelas aplicadas nos spas Europeus para peloterapia, consideramos este grupo de argilas aplicável para tratamentos de hidrologia médica nos spas Portugueses.

Spatiotemporal phenomena related to the rainfall measurements can be characterised by statistical models grounded on physical concepts instead of being identified by spatiotemporal patterns based on standard correlations and related analytical tools. This perspective is useful in understanding if the relationships among neighbouring zones and consecutive years are attributable to latent physical mechanisms. Satellite data are used to examine this theory and provide evidence on empirical basis. A recent hydrological theory, which is based on the concept of self-organisation, consists of simplified physical mechanisms that are essential for the explanation of local data relationships. The regression models inspired by the diffusion of innovation can approximate the evolution of the rainfall process within a year through a more straightforward perspective. However, the multitude of collected data requires innovative techniques of data management and advanced analytical solutions, in order to achieve optimal results in reasonable time. Indeed, the nonlinear least squares and nonlinear quantile regression are considered to make inference on the response variable given some covariates. A new quantile regression technique is developed in order to provide simultaneous estimates that do not violate the monotonicity property of quantiles. The nonlinear least squares highlight strong connections among rainfall and the salient features of the measurements areas. Furthermore, the quantile regression analyses quantify the intrinsic variability of the data.
I fenomeni spazio-temporali relativi alle misurazioni di piovosità possono essere caratterizzati da modelli statistici fondati su concetti fisici invece di essere identificati da modelli standard basati su correlazioni spazio-temporali e i relativi strumenti analitici. Questa prospettiva è utile per capire se i rapporti tra zone confinanti e anni consecutivi sono attribuibili a meccanismi fisici latenti. Dati satellitari vengono utilizzati per esaminare questa teoria e fornire prove su base empirica. Una recente teoria idrologica, basata sul concetto di auto-organizzazione, è caratterizzata da meccanismi fisici semplificati che sono essenziali per la spiegazione delle relazioni locali presenti nei dati osservati. I modelli di regressione, che si ispirano alla teoria della diffusione di innovazioni, sono in grado di approssimare l'evoluzione del processo di precipitazione di un singolo anno attraverso una più semplice prospettiva. Tuttavia, la moltitudine di informazioni raccolte richiede tecniche innovative di gestione dei dati e soluzioni analitiche avanzate con lo scopo di ottenere risultati ottimali in tempi ragionevoli. Infatti, i minimi quadrati e la regressione quantilica per modelli non-lineari vengono utilizzati per fare inferenza sulla variabile risposta condizionatamente ad alcune covariate. Una nuova tecnica di regressione quantilica è stata sviluppata ad hoc al fine di fornire stime simultanee che non vìolino la proprietà di monotonicità dei quantili. I minimi quadrati non lineari evidenziano un forte legame tra le precipitazioni e alcune caratteristiche salienti delle zone di misurazione. Inoltre, le analisi ottenute tramite la regressione quantilica quantificano la variabilità intrinseca nei dati.

A flash flood is a flood that follows the causative storm event in a short period of time. The term “flash” reflects a rapid response, with water levels in the drainage network reaching a crest within minutes to a few hours after the onset of the rain event, leaving extremely short time for warning [Creutin and Borga, 2003; Borga et al., 2008]. Flash floods are localized phenomena that occur in watersheds of few hundred kilometres or less, with response times of a few hours or less [Creutin and Borga, 2003; O’Connor and Costa, 2004]. Such basins respond rapidly to intense rainfall because of steep slopes and impermeable surfaces, saturated soils, or because of human (i.e., urbanization) or fire-induced alterations to the natural drainage. Causative events are generally excessive storms, but can also be the sudden release of water impounded by a natural jam (i.e., formed by ice or rock, mud, and wood debris) or human-made dam or levee. This thesis focuses on flash flood events associated with heavy rainfall. Europe experienced several catastrophic flash floods in the last decades. Data concerning a number of these floods occurred during the last 15 years have been reported in Marchi et al. (2010). Examination of these data and references therein shows that: Flash floods occur in any of the hydroclimatic regions of Europe, even though three regions appear to be characterized by high flash flood potential: Mediterranean, Alpine Mediterranean, and Inland Continental Europe; Heavy rainfall accumulation is a necessary but not sufficient condition for flash floods, since hydrology critically controls flash-flood-triggering. Without hydrological analysis, it is impossible to evaluate the flood potential of storms, particularly in the fringe of the flood/no flood threshold; Flash flood hazard is related to both stream response (flood) and landscape response (landslide and erosion). The intense erosion and solid transport associated with these extreme events add to the hazard and strongly influence the quality of soils, waters and ecosystems. The twofold consequence of the above observations is that forecasting of flash-floods: Depends critically on meso-scale storm forecasting, with a specific attention to the processes leading to slow movement of the precipitation system; Necessitates real time hydrological modelling, with a specific attention to the runoff generation processes over a wide range of scales. Although they are seldom all deployed at the same time, the technical requirements for a hydrometeorological flash flood forecasting system include: A numerical weather prediction (NWP) model, capable to provide short-range Quantitative Precipitation Forecasts (QPF); A remote sensing based (radar, satellites) precipitation detection system, for storm monitoring and for the possible initialization and conditioning of the NWP model, and A hydrological-hydraulic forecasting model, capable to forecast the stream response from the rain input. These requirements are similar to those of more common riverine flood forecasting systems. However, some features characterise flash flood forecasting with respect to riverine flood forecasting and point out to their larger uncertainty. These are: The short lead time, which implies both the integration of meteorological and hydrologic forecast, and the difficulties of using data assimilation procedures based on real time observed discharges to reduce uncertainty in hydrologic predictions; The need to provide local forecasts, which means that, on one hand, the rainfall must be monitored and forecasted on a wide range of space/time scales, and, on the other hand, every tributary of a monitored basin can be considered as a potential target for flood warning. Estimation of extreme rainfall rates by weather radar at the appropriate time and space scales is the cornerstone of flash flood analysis and forecasting. A large body of research work has greatly improved in the last two decades radar technology and algorithms for rain quantification. This work has shown that well maintained conventional radar systems can estimate rainfall at ground level provided that a number of precautions are taken, and in particular: The siting of the instrument and its scanning protocol must be carefully selected and analysed; The quality of the instrument must be routinely checked; The signal processing must take into account the physics of the instrument as well as the properties of the atmospheric and ground targets. A downstream control of the radar rainfall processing can rely on rain-gauge measurements at ground level using a variety of methods. When these precautions are taken, different studies have shown that radar-based rainfall estimates are reliable and may be used as input in rainfall-runoff models for flood modelling and forecasting [Borga et al., 2000; Delrieu et al., 2005; Borga et al., 2002]. These very positive results must not be hiding some weaknesses: Most of these results never had the opportunity to be coherently validated over a significant number of flash floods events. The use of specific experiments or of limited operational radar data sets is insufficient to test complex combinations of algorithms, especially if high rain intensities are of interest. Very few results have been translated into operational hydrologic applications. This thesis aims to investigate the use of weather radar for the purpose of understanding the hydrometeorological mechanisms leading to flash floods, and then for flash flood forecasting. The outline of the thesis work is as follows. Chapter 1 provides a literature review of the rainfall estimation by weather radar for flash flood-generating storms. Chapter 2 describes a number of procedures for the rainfall estimation at the ground during flash flood events in mountainous catchments. A metric for the analysis of the rainfall field spatial patterns is proposed in Chapter 3, in the context of the analysis of a number of Romenian flash floods. This metric is used for the analysis of two flash flood events, respectively occurred in 2003 in the Eastern Italian Alps (Chapter 4) and in Western Slovenia (Chapter 5). Major conclusions from the work are reported in Chapter 6.
Una piena improvvisa è una piena che segue l’evento precipitativo che la ha causata entro un breve periodo di tempo. Il termine “improvvisa o flash” riflette una risposta rapida, con il picco di piena che si verifica nella rete di drenaggio nel volgere di alcuni minuti fino a poche ore dopo l’inizio dell’evento di pioggia. Questo fatto lascia intendere quanto poco tempo ci sia per l’allerta [Creutin and Borga, 2003; Borga et al., 2008]. Questo tipo di bacini rispondo rapidamente ad una precipitazione intensa a causa di pendii ripidi e superfici impermeabili, terreni saturi, o a per fattori determinati dall’uomo (vedi per esempio l’urbanizzazione) o a causa di alterazioni del drenaggio naturale del terreno dovuto ad incendi. Gli eventi scatenanti le piene improvvise sono generalmente precipitazioni che portano all’eccesso di drenaggio, ma questo tipo di piene possono anche essere scatenate dal rilascio improvviso di acqua trattenuta da impedimenti naturali (per esempio formati da ghiaccio e roccia, fango e detriti di legno) o di tipo artificiale come dighe e argini. Questa tesi si concentra su eventi di piena improvvisa associati a precipitazioni intense. L’Europa ha conosciuto diverse inondazioni catastrofiche negli ultimi decenni. I dati relativi un certo numero di queste inondazioni che si sono verificate nel corso degli ultimi 15 anni sono riportati da Marchi et al. (2010). Dall’analisi di questi dati e di queste fonti risulta che: Una piena improvvisa si può verificare in qualsivoglia regione idroclimatica dell’Europa, anche se tre regioni sembrano essere caratterizzate da una grande incidenza di di piene improvvise: l’area Mediterranea, quella Alpino-Mediterranea, e quella Continentale; Una gran quantità di pioggia accumulata è una condizione necessaria ma non sufficiente al verificarsi di una piena improvvisa, dal momento che l’idrologia controlla in modo decisivo l’innesco della piena improvvisa. Senza un’analisi di tipo idrologico, risulta impossibile valutare la probabilità che una data precipitazione scateni una piena, in praticolare in termini di una soglia oltre la quale si verifica la piena; La pericolosià delle piene improvvise è collegata sia alla risposta del fiume (la piena) che alla risposta del terreno (fenomeni di tipo franoso ed erosivo). L’intensa erosione ed il trasporto solido associati a questi fenomeni estremi si aggiungono alla pericolosità ed influenzano in modo significativo la qualità dei terreni, delle acque e degli ecosistemi. La duplice conseguenza delle osservazioni appena fatte è che la previsione di piene improvvise: Dipende in modo determinante dalle previsioni delle precipitazioni che si sviluppano alla meso-scala, con una attenzione specifica ai processi che frenano la circolazione del sistema di precipitazione; Richiedone modelli idrologici che lavorino in tempo reale, con una particolare attenzione ai processi du generazione del deflusso a vasta scala. Anche se raramente sono tutti utilizzati contemporaneamente, i requisiti tecnici per un sistema di previsione idrometeorologica per le piene improvvise comprendono: Un modello numerico di previsione (NWP2), in grado di fornire previsioni quantitative di pioggia a corto raggio (QPF3); Un sistema di rilevamento in remoto per la pioggia (radar, satellite), per il monitoriraggio dei fenomeni temporaleschi e la possibilie inizializzazione e condizionamento del modello NWP, e Un modello di previsione idrologico-idraulico, in grado di prevedere la risposta del corso d’acqua all’input pioggia. Tali requisiti sono simili a quelli più comuni utilizzati per la previsione delle alluvioni dei sistemi fluviali. Tuttavia, alcuni elementi caratterizzano la previsione delle piene improvvise rispetto alla previsione delle alluvioni e ne sottolineano la grande incertezza. Questi sono: Il breve periodo durante il quale questi processi si sviluppano, che implica sia l’integrazione di un sistema di previsione di tipo meteorologico e idrologico, che la difficoltà nell’utilizzo di procedure di assimilazione di dati basate sull’osservazione in tempo reale delle portate al fine di ridurre l’incertezza nelle previsioni idrologiche; La necessità di fornire previsioni a scala locale, il che significa da una parte che la pioggia deve essere monitorata e prevista su una vasta scala spazio-temporale, all’altra che ciascun tributario del bacino monitorato può essere considerato come un bersaglio potenziale per un allarme di piena. La stima di fenomeni precipitativi estremi tramite l’utilizzo del radar meteorologico alla appropriata scala spazio-temporale è una pietra miliare dell’analisi e della previsione delle piene improvvise. Una grande branca della ricerca in questo campo ha favorito un notevolmente migliorato, negli ultimi due decenni, delle tecnologie radar e degli algoritmi per la stima di pioggia. Questo lavoro ha dimostrato che anche utilizzando sistemi radar convenzionali si possono ottenere stime di precipitaziona a livello del suolo, a condizione che vengono adottate una serie di precauzioni, in particolare: L’ubicazione dello strumento e del suo protocollo di scansione devono essere attentamente selezionati ed analizzati; La qualità dello strumento deve essere sottoposta a controlli ordinari; L’elaborazione del segnale deve tener conto della fisica dello strumento così come delle proprietà atmosferiche e dei bersagli di terra. Un controllo a valle del trattamento delle precipitazioni radar può essere fatto tramite misurazioni da pluviometro a livello del suolo utilizzando una varietà di metodi. Quando si sono prese queste precauzioni, diversi studi hanno dimostrato che le stime di precipitazione basate su radar meteorologico sono affidabili e possono essere utilizzate come input di modelli afflussodeflusso per la modellazione e la previsione delle piene [Borga et al., 2000; Delrieu et al., 2005; Borga et al., 2002]. A fronte di questi risultati molto positivi non devono però essere nascosti alcuni punti deboli: La maggior parte di questi risultati non hanno mai la possibilità di essere coerentemente convalidati su un numero significativo di eventi di piena improvvisa. L’utilizzo di esperimenti specifici o di una banca dati limitata di dati radar è insufficiente a testare la combinazione complessa degli algoritmi utilizzati, specialmente se si è interessati ad intensità di pioggia elevata. Un numero molto limitato di risultati positivi è stato tradotto in applicazioni idrologiche operative. Questa tesi si propone di esaminare l’uso del radar meteorologico ai fini della comprensione dei meccanismi idrometeorologici che portano alla formazione di piene improvvise, e quindi alla loro previsione. L’organizzazione del lavoro di tesi è la seguente. Il Capitolo 1 fornisce una revisione della letteratura sul tema della stima di precipitazione tramite radar meteorologico per le precipitazioni che causano la formazione di piene improvvise. Il Capitolo 2 descrive una serie di procedure per la stima delle precipitazioni al suolo durante gli eventi di piena improvvisa in bacini montani. Una metrica per l’analisi spaziale del campo di pioggia viene proposta nel Capitolo 3, nel contesto dell’analisi di una serie di piene improvvise verificatesi in Romania. Questa metrica è utilizzata per l’analisi di due eventi di piena, accaduti rispettivamente nel 2003 nelle Alpi Italiane friulane e nella parte ovest della Slovenia (Capitolo 5). Le conclusioni principali del lavoro di tesi sono riportate nel Capitolo 6.

A global climate change may have large impacts on water resources on regional and global scales. General circulation models (GCMs) are the most used tools to evaluate climate-change scenarios on a global scale. They are, however, insufficiently describing the effects at the local scale. This thesis evaluates different approaches of statistical downscaling of precipitation from large-scale circulation variables, both concerning the method performance and the optimum choice of predictor variables.

The analogue downscaling method (AM) was found to work well as “benchmark” method in comparison to more complicated methods. AM was implemented using principal component analysis (PCA) and Teweles-Wobus Scores (TWS). Statistical properties of daily and monthly precipitation on a catchment in south-central Sweden, as well as daily precipitation in three catchments in China were acceptably downscaled.

A regression method conditioning a weather generator (SDSM) as well as a fuzzy-rule based circulation-pattern classification method conditioning a stochastical precipitation model (MOFRBC) gave good results when applied on Swedish and Chinese catchments. Statistical downscaling with MOFRBC from GMC (HADAM3P) output improved the statistical properties as well as the intra-annual variation of precipitation.

The studies show that temporal and areal settings of the predictor are important factors concerning the success of precipitation modelling. The MOFRCB and SDSM are generally performing better than the AM, and the best choice of method is depending on the purpose of the study. MOFRBC applied on output from a GCM future scenario indicates that the large-scale circulation will not be significantly affected. Adding humidity flux as predictor indicated an increased intensity both in extreme events and daily amounts in central and northern Sweden.

Climate variability and landscape characteristics interact to define specific catchment hydrological response. Catchments are considered fundamental landscape units to study the water cycle, since all aspects of the land surface component of the hydrological cycle come together in a defined area, which enables scientific research through mass, momentum and energy budgets. The role of climate-landscape interactions in defining hydrologic partitioning, particularly at the catchment scale, however, is still poorly understood. In this study, a catchment scale process-based hydrologic model (hillslope storage Boussinesq- soil moisture model, hsB-SM) was developed to investigate such interactions. The model was applied to 12 catchments across a climate gradient. Dominant time scales (T.S.) of catchment response and their dimensionless ratios were analyzed with respect to climate and landscape features to identify similarities in catchment response. A limited number of model parameters could be related to observable landscape features. Several T.S. and dimensionless numbers show scaling relationships with respect to the investigated hydrological signatures (runoff coefficient, baseflow index, and slope of the flow duration curve). Some dimensionless numbers vary systematically across the climate gradient, pointing to the possibility that this might be the result of systematic co-variation of climate, vegetation and soil related T.S. Each of 12 behavioral hsB-SM models were subsequently subjected to each of 12 different climate forcings. Mean deviations from Budyko's hypothesis controlling long-term hydrologic partitioning (represented by the evaporation index, E/P, dependence on the aridity index, PET/P) were computed per catchment and per climate. The trend observed per catchment could be explained by the dimensionless ratio of perched aquifer storage-release T.S. and mean storm duration T.S. The trend observed per climate could be explained by an empirical relationship between fraction of rainy days and average daily temperature during those days. Catchments that produce more E/P have developed in climates that produce less E/P, when compared to Budyko's hypothesis. Also, climates that give rise to more E/P are associated with catchments that have vegetation with less efficient water use parameters. These results suggest the possibility of vegetation and soil co-evolution in response to local climate leading to (catchment scale) predictable hydrologic partitioning.

The quality of the Earth’s water resources have deteriorated due to human impacts. A key scientific challenge is to understand, quantify and predict the water-borne spreading of pollutants at relevant scales for freshwater management and water quality restoration programs. However, understanding the natural processes controlling large-scale hydrological transport of pollutants may be masked by river regulation schemes (in the form of dams and reservoirs), which are common in many large rivers. The main objective of this thesis is to increase the current knowledge regarding large-scale spreading of metals in hydrological systems. This objective is addressed through studying net impacts of mining (a main contributor to global metal pollution) on the spreading of metals in water systems and through investigating the mitigation opportunities of wetlands across the landscape. The main study region of this thesis is the Lake Baikal basin of Russia and Mongolia, which includes the large unregulated Selenga River and its delta-wetland areas. In addition, a set of global wetland sites are also studied. A multi-method approach is used in the four studies of this thesis. The methods include field-measurements, data synthesis, metal mass flow and water flow-path quantifications, as well as geochemical modelling. Results show that mining in the upstream part of the Lake Baikal basin is a significant contributor to riverine mass flows of several metals. The mass flows increased by an order of magnitude over the mining site. The observed speciation between dissolved (more bioavailable) and suspended (less bioavailable) phases could be well predicted for some metals (Fe, V, Pb and Zn) using a geochemical equilibrium model. However, the model failed to reproduce the speciation of other metals (Cr, Cu, Mn and Mo). In these cases, non-equilibrium processes may need to be considered, and adsorption databases may need to be developed, in order to make dependable predictions. Results also suggest that the concentration of dissolved organic carbon, which exhibits seasonal variability and long-term increasing trends due to climate change effects in the Arctic, can have a large impact on metal pollution transport. Further, observations showed that individual wetlands of the Selenga River delta locally retained between 77-99 % of incoming metal loads. However, a systematic analysis of current knowledge showed that large-scale net effects can differ considerably from the functions observed at individual wetlands on smaller scales. Along large-scale flow-paths, through which wetlands are connected with each other as well as with the larger landscape, key processes which can considerably contribute to such scale differences in function may occur. A survey of the current wetland research showed that relatively few studies have considered the larger scales at which key pollutant pressures and water quality changes take place. This thesis highlights the need for more research on large-scale wetland systems, which can aid in evaluating net pollution effects at landscape scales. This in turn can facilitate evaluations of how and when wetland systems may function as large-scale nature-based solutions.
Kvaliteten på jordens vattenresurser har försämrats på grund av mänsklig påverkan. En viktig vetenskaplig utmaning är att förstå, kvantifiera och förutsäga den vattenburna spridningen av föroreningar, på skalor som är relevanta för vattenresursförvaltning och åtgärdsprogram. De underliggande, naturliga processer som styr storskalig hydrologisk föroreningstransport kan dock maskeras av att de flesta stora floders flöden är reglerade med hjälp av dammar och reservoarer. Målet med den här avhandlingen är att öka kunskapen kring hydrologisk storskalig spridning av metaller. Detta görs genom att studera nettoeffekter av gruvverksamhet (en viktig källa till globala metallföroreningar) på metallers spridning i vattensystemet, samt att undersöka våtmarkers möjligheter att rena förorenade flöden i landskapet. Avhandlingens huvudstudieområde är Bajkalsjön och dess tillrinningsområde (i Ryssland och Mongoliet), vilket inkluderar den oreglerade Selengafloden och dess delta-våtmarksområden. Även en grupp av globala våtmarksområden har studerats. Flera metoder användes i de fyra studierna som ingår i denna avhandling, inklusive fältmätningar, datasyntes, massflödes- och flödesvägskvantifieringar, och geokemisk modellering. Resultaten visar att gruvdrift i uppströms-delar av Bajkalsjöns tillrinningsområde bidrar betydligt till förhöjda halter av flera metaller i flodsystemen. Massflödenena ökade en storleksordning över gruvområdet. Den observerade metall-specieringen mellan lösta (mer biotillgängliga) och partikulära (mindre biotillgängliga) faser kunde modelleras väl för vissa metaller (Fe, V, Pb och Zn) med en geokemisk jämviktsmodell. Modellen lyckades dock inte reproducera specieringen av andra metaller (Cr, Cu, Mn och Mo). I dessa fall kan icke-jämviktsprocesser behöva beaktas, och adsorptions-databaser kan behöva utvecklas för att förbättra prediktionerna. Resultaten visar också att koncentrationen av upplöst organiskt kol, som uppvisar stora årstidsvariationer samt långsiktigt ökande trender på grund av klimatpåverkan i Arktis, kan ha stor inverkan på metallföroreningars transport. Observationer visade att enskilda våtmarker i Selengafloden lokalt kunde minska inkommande massflöden av metaller med 77 till 99 %.  En systematisk genomgång av aktuellt kunskapsläge visade dock att storskaliga nettoeffekter kan skilja sig mycket från de funktioner som observeras vid enskilda våtmarker på mindre skalor. Längs storskaliga flödesvägar, genom vilka flera våtmarker är kopplade till varandra och till det större landskapet, kan viktiga processer ske, vilket avsevärt kan bidra till sådana skal-skillnader i funktion. En genomgång av aktuell våtmarksforskning visade att relativt få studier beaktade dessa större skalor där föroreningsspridning och vattenkvalitetsförändringar sker. Denna avhandling belyser behovet av ökat forskningsfokus på storskaliga våtmarkssystem. Detta kan hjälpa till att förstå föroreningars nettoeffekter på landskapsskalor, vilket underlättar vid bedömning av hur och när våtmarkssystem fungerar som storskaliga, så kallade naturbaserade lösningar.

Successfully modeling one system response (e.g. hydrograph or solute transport) sometimes gives the false sense of well-characterizing the modeled system. This is partly because of the well-known equifinality issue; during the calibration process multiple parameter combinations can produce similarly good results. One step forward towards a better-defined system is using measured (at relevant scale) values for the model parameters, as well as using multiple conditions to constrain the model. But when not enough, or relevant, field measurements are available, virtual experiments (VE’s) can be used as a supplementary method to model calibration. The advantage of VE’s over model calibration is that they can also be used to explore assumptions both on the system hydrological processes, and on the model structure. One goal of this study was to utilize both field measurements and models for better characterization of the S-transect hillslope, located in Västrabäcken catchment, Northern Sweden. This included (a) characteristics in space: system vertical boundaries, hydraulic parameters, pore water velocity distribution, spatial correlation of flowpaths, soil water retention properties; (b) characteristic of system’s dynamic behavior: storage – discharge relationship, transit time distribution, turnover time; and (c) outputs’ sensitivity to external forcing, and to small scale structure assumptions. The second goal was to comment on the value of field measurements and virtual experiments for extracting information about the studied system. An intensely monitored study hillslope was chosen for this work. Although the hillslope has already been the subject of multiple field and modelling studies, there are still open questions regarding the characteristics listed above. The models used were the Vertical Equilibrium Model (VEM), and the Multiple Interacting Pathways (MIPs) model. It was found that the hillslope was well connected; from the near-stream areas up to the water divide the storage – discharge relationship could be described as an exponential function. Also, the dynamic storage (which controls the hydrograph dynamics) was much smaller comparing to the total hillslope storage. The unsaturated soil storage was found to be more sensitive to water table positions than vertical flux magnitude. The dynamic condition of external forcing (precipitation and evapotranspiration) affected the transit time distribution (TTD) shape. And, opposite to expectations, TTD was not sensitive to micro-scale structural assumptions tested here.

In the study of dynamic subsurface processes there is a need to monitor temperature and groundwater fluxes efficiently in both time and space. Distributed Temperature Sensing has recently become more accessible to researchers in Earth Sciences, and allows temperatures to be measured simultaneously, at small intervals, and over large distances along fibre optic cables. The capability of DTS in conjunction with heat injection to detect groundwater fluxes, is assessed in this thesis using a combination of numerical modelling, laboratory tests, and field trials at the Ploemeur research site in Brittany, France. In particular, three methodological approaches are developed: thermal dilution tests, point heating, and the hybrid cable method. A numerical model was developed to assess the sensitivity range of thermal dilution tests to groundwater flow. Thermal dilution tests undertaken at Ploemeur showed lithological contrasts, and allowed the apparent thermal conductivity to be estimated in-situ, but failed to detect previously identified transmissive fractures. The use of DTS to monitor in-well vertical flow is then investigated. This is first using a simple experiment deploying point heating (T-POT), which tracks a parcel of heated water vertically through the borehole. The method allowed for the relatively quick estimation of velocities in the well. The use of heated fibre optics is then trialled, and through a field test was shown to be sensitive to in-well vertical flow. However, the data suffered from a number of artefacts related to the cable installation. To address this, a hybrid cable system was deployed in a flume to determine the sensitivity relationship with flow angle and electrical power input. Additionally, a numerical model was developed, which suggested a lower limit for velocity estimation due to thermal buoyancy. With the emergence of Distributed Acoustic Sensing, fibre optics may become an increasingly practicable and complete solution for monitoring subsurface processes.

There is increasing recognition that the hydrology of the Greenland Ice Sheet plays an important role in the dynamics and therefore mass balance of the ice sheet. Understanding the hydrology of the ice sheet and being able to predict its future behaviour is therefore a key aspect of glaciological research. To date, the ice sheet’s hydrology has tended to be inferred from the analysis of surface velocity measurements, or modelled in a theoretical, idealised way. This study focuses on the development of a high spatial (100 m) and temporal (1 hour) resolution, physically based, time-dependent hydrological model which is applied to the ~2,300 km2 Paakitsoq region, West Greenland, and is driven, calibrated, and evaluated using measured data. The model consists of three components. First, net runoff is calculated across the ice sheet from a distributed, surface energy- balance melt model coupled to a subsurface model, which calculates changes in temperature, density and water content in the snow, firn and upper-ice layers, and hence refreezing. The model is calibrated by adjusting key parameter values to minimize the error between modelled output and surface height and albedo measurements from the three Greenland Climate Network (GC-Net) stations, JAR 1, JAR 2 and Swiss Camp. Model performance is evaluated in two ways by comparing: i) modelled snow and ice distribution with that derived from Landsat-7 ETM+ satellite imagery using Normalised Difference Snow Index (NDSI) classification and supervised image thresholding; and ii) modelled albedo with that retrieved from the Moderate- resolution Imaging Spectroradiometer (MODIS) sensor MOD10A1 product. Second, a surface routing / lake filling model takes the time-series of calculated net runoff over the ice sheet and calculates flow paths and water velocities over the snow / ice covered surface, routing the water into ‘open’ moulins or into topographic depressions which can fill to form supraglacial lakes. This model component is calibrated against field measurements of a filling lake in the study area made during June 2011. Supraglacial lakes are able to drain by a simulated hydrofracture mechanism if they reach a critical volume. Once water is at the ice / bed interface, discharge and hydraulic head within subglacial drainage pathways are modelled using the third model component. This consists of an adaptation of a component (EXTRAN) of the U.S. Environmental Protection Agency Storm Water Management Model (SWMM), modified to allow for enlargement and closure of ice-walled conduits. The model is used to identify how the subglacial hydrological system evolves in space and time in response to varying surface water inputs due to melt and lake drainage events, driven ultimately by climate data. A key output from the model is the spatially and temporally varying water pressures which are of interest in helping to explain patterns of surface velocity and uplift found by others, and will ultimately be of interest for driving ice dynamics models.