Дисертації з теми "Hydraulic and Hydrological Modelling"

Terrace building have been expanded in the 19th century because of the increased demographic pressure and the need to crop additional areas at steeper slopes. Terraces are also important to regulate the hydrological behavior of the hillslope. Bench terraces, reducing the terrain slope and the length of the overland flow, quantitatively control the runoff flow velocity, facilitating the drainage and thus leading to a reduction of soil erosion. The study of the hydrologic-hydraulic function of terraced slopes is essential in order to evaluate their possible use to cooperate for flood-risk mitigation also preserving the landscape value. Few studies in literature are available on rainfall-runoff transformation and flood risk mitigation in terrace areas. Then, research results in this field are still scarce. The goal of this work is to improve knowledge on hydrological processes affecting a terraced slope and their effect on flood control. Specific researches objectives are: • Studing the the reduction of peak runoff at the toe of a hillslope and the delay in the passage of peak flow, which are provided by sequence of dry-stone walls under different space arrangements along the hillslope; • Understanding the rainfall-runoff separation mechanism and the superficial and subsurface flow propagation in case of terraced slopes. In order to reach the above objectives the hydrological response of a bench terrace was investigated by using a research approache based on modelling and experimental activities. In the first part of the thesis the The FLO-2D model is used to analyse the runoff propagation mechanism of a terraced slope (sequence of dry-stone walls) by varying number and spacing of terraces and assuming two hydrological soil setting scenarios in terms of antecedent moisture conditions within the Soil Conservation Service-Curve Number method. The model analysis shows that the majority of runoff modifications at the outlet of a terraced system result from topographical modifications rather than local variations of the infiltration capacity at the dry-stone wall zone. Repeated modelling applications show that, given a quite-typical scenario of a 20°-sloped hillslope and a reference intense rainstorm, the peak discharge reduction at the hillslope outlet depends on the percentage of the area managed with terraces. The reduction can be calculated with a logarithmic-type function (for example, an increase of terraced area from 10% to 30% might bring to runoff peak reduction of almost 45%). This information can help determine where terrace additions are more effective in terms of hydrological benefit. The second part of the thesis focus on an experimental/modelling research that aims to better focus the times of the hydrological response, which are determined by a hillslope plot bounded by a dry-stone wall, considering both the overland flow and the groundwater. A physical model, characterized by a quasi-real scale, has been built to reproduce the behavior of a 3%, 6% and 9% outward sloped terrace at bare and vegetated soil condition.The model consists of a steel metal box (1 m large, 3.3 m long, 0.8 m high) containing the hillslope terrain. The terrain is equipped with two piezometers, 9 TDR sensors measuring the volumetric water content, a surface spillway at the head releasing the steady discharge under test, two scales one at the wall base to measure the groundwater discharge and another at the top of the wall to measure the surface runoff. The experiments deal with different initial moisture condition (high and low degree of saturation), and discharges of 19.5, 12.0 and 5.0 l/min. Each experiment has been replicated, conducting a total number of 35 tests. The volumetric water content analysis produced by the 9 TDR sensors was able to provide a quite satisfactory representation of the soil moisture during the runs. Then, different lag times at the outlet since the inflow initiation were measured both for runoff and groundwater. Moreover, the time of depletion and the piezometer response have been monitored and analyzed, well corroborating the findings on the kinematics of the terrace plot. Finally, the computation of the specific Curve Number (Soil Conservation Service) of the physical model has revealed values rather large if compared with those reported in the literature. This phenomenon was likely caused by the high values of the inflow discharge, the limited cross-width of the model (1 m), the increasing compactness of the soil owing to the experiment repetition and the confined waterproof box). The experimental results indicate that terrace soil was highly heterogeneous, including discontinuities and piping systems that facilitated a rapid infiltration and the development of fast subsurface flow. The Groundwater in general is a small part of the total outflow but in case the presence of pipe is important it is coupled with impulsesive infiltration rates. A conceptual hydrological model was implemented and calibrated based on the experimental data. The model results fit well the measurements even if the groundwater component is not properly modelled. This is due to the activation of important piping systems during some of the tests; the physical proces that describ this located losses were not studied and integrated in the model. These pioneering experiments have produced some remarkable outcomes on the important role of lag-times (runoff and groundwater) and provided new knowledgement on the hydrological functioning of bench terraced systems for addressing more efficient management and maintenance issues of this important agricoltural structures.
I sistemi terrazzati si sono diffusi nel diciannovesimo secolo a seguito della crescente pressione demografica e della conseguente necessità di estendere le coltivazioni anche su terreni ad elevata pendenza. Oltre che dal punto di vista agrario tali sistemi sono importanti ai fini della regolazione della risposta idrogeologica di un versante. Infatti essi riducono la pendenza e la lunghezza dello scorrimento superficiale, controllando quindi quantitativamente la velocità del deflusso superficiale, facilitando il drenaggio e contribuendo in questo modo alla riduzione dei fenomeni erosivi. Lo studio della funzione idrologico-idraulica dei versanti terrazzati è essenziale per valutarne il possibile utilizzo come misure di mitigazione del rischio idraulico capaci anche di preservare il valore paesaggistico dei territori su cui essi insistono. In letteratura sono disponibili pochi studi inerenti la risposta idrologica di versanti terrazzati; l’avanzamento della ricerca in tale ambito è l’obiettivo principale di questo lavoro. In particolare vengono affrontate le seguenti tematiche: - la valutazione degli effetti di mitigazione della pericolosità idraulica (riduzione del picco di piena e suo ritardo temporale) a scala di versante indotti dalla presenza di sistemi terrazzati; - lo studio dei meccanismi di trasformazione afflussi-deflussi e dei processi di propagazione degli stessi in sistemi terrazzati; Al fine di raggiungere tali obiettivi è stato implementato un approccio integrato basato su attività sperimentali e modellistiche. Nella prima parte del lavoro è stato utilizzato il modello idraulico FLO-2D per analizzare i processi di propagazione in atto in un versante terrazzato (composto da una sequenza di muri a secco) al variare del numero e della disposizione spaziale dei terrazzi e assumendo due diversi scenari di saturazione del suolo rappresentati da diversi valori di umidità iniziale antecedente l'evento, come previsto dal metodo Soil Conservation Service - Curve Number. L'analisi modellistica mostra che la riduzione del deflusso alla base del sistema terrazzato dipende maggiormente dalle modifiche topografiche piuttosto che dalle variazioni della capacità di infiltrazione del suolo adiacente il muro. Le simulazioni eseguite su di un versante con una pendenza di 20° e alimentato da un evento di precipitazione intensa, mostrano che il picco di piena alla sezione di chiusura si riduce in funzione della percentuale di area terrazzata. Tale riduzione può essere valutata attraverso una specifica funzione logaritmica (per esempio, al crescere dell'area terrazzata da 10% a 30% la riduzione del picco di piena può essere quasi del 45%). Questa informazione può aiutare a individuare il corretto inserimento dei terrazzi per una maggiore efficace in termini di benefici idrologici. La seconda parte del lavoro riguarda lo studio della risposta idrologica di un’unità terrazzata con un muro a secco attraverso attività sperimentali e modellistiche. In particolare è stato costruito un modello fisico a scala reale per riprodurre il comportamento di un terrazzo al variare della sua pendenza (3%, 6% e 9%) e del tipo di copertura del suolo (suolo nodo o inerbito). Il modello consiste in un box metallico (1 metro di larghezza, 3.3 metri di lunghezza e 0.8 m di altezza) che contiene al suo interno un terrazzo composto da un versante delimitato a valle da un muro a secco. Tale versante è stato strumentato con 9 sensori TDR per la misura del contenuto di umidità del suolo, uno sfioratore delle portate liquidi in ingresso al versante a monte dello stesso, due bilance per la misura del deflusso, una posizionata alla base del muro per la misura del deflusso sotterraneo e una in corrispondenza della parte superiore del muro per la misura del deflusso superficiale. Gli esperimenti sono stati caratterizzati da differenti condizioni di umidità iniziale (ad alto e basso grado di saturazione) e da portate liquide in ingresso costanti e pari a 19.5, 12 e 5 l/minuto. Ogni esperimento è stato replicato per un totale di 35 esperimenti eseguiti. L'esame delle misure dei 9 sensori TDR ha fornito una soddisfacente rappresentazione dell'andamento dell'umidità globale del suolo nel corso di ogni esperimento. Sono stati poi misurati diversi tempi caratteristici della risposta idrologica alla sezione di chiusura sia per il deflusso superficiale che per il deflusso sotterraneo. I risultati ottenuti aiutano a comprendere la cinematica dei processi idrologici che caratterizzano l’unità terrazzata. E’ stato calcolato uno specifico Curve Number (Soil Conservation Service) associato all’unità terrazzata che assume valori piuttosto alti se comparati a quelli riportati in letteratura. Questo comportamento è probabilmente legato alle alte portate in ingresso, alla limitata sezione idraulica (1m), alla crescente compattazione del suolo causata dal susseguirsi delle prove e al fatto che il terrazzo è confinato all'interno di una struttura metallica impermeabile. Un innovativo modello idrologico è stato implementato e calibrato sui dati sperimentali. I risultati modellistici riproducono in modo soddisfacente le misure soprattutto per quanto riguarda il deflusso superficiale che è la componente prevalente di deflusso. In generale il deflusso sotterraneo non risulta invece essere propriamente simulato in quanto il modello non tiene conto di particolari fenomeni di infiltrazione impulsiva presenti in alcune prove. Infatti, i risultati sperimentali indicano che il suolo all'interno del terrazzo è altamente eterogeneo, con la presenza di discontinuità e sistemi di canali sotterranei che facilitano una rapida infiltrazione e lo sviluppo di deflusso sub-superficiale impulsivo che va a sommarsi al deflusso profondo (generalmente di modesta entità) alimentato dall’infiltrazione connessa agli strati superficiali del suolo. La sperimentazione effettuata risulta innovativa e fornisce nuove conoscenze sulla funzione idrologica-idraulica di un sistema terrazzato che possono servire per indirizzare in modo più efficiente la gestione e la manutenzione di queste importanti sistemazioni agrarie.

Loktak Lake is an internationally important wetland in northeast India that provides valuable goods and services to local communities as well as supporting high biodiversity. Over the last three decades ecological modifications have occurred, most notably due to the construction and operation of the Ithai Barrage. The focus on maximising hydropower generation increased mean lake water levels and reduced their annual variability. This thesis synthesises hydrometeorological and related data for the lake and its catchment. Data are employed in coupled hydrological / hydraulic catchment models (MIKE SHE / MIKE 11) of three gauged sub-catchments, which are calibrated / validated using observed discharges. Results are used to estimate ungauged sub-catchment flows. Catchment model results are combined with meteorological data and current abstractions within a water balance model which successfully simulates observed lake water levels. A series of barrage operation options are developed using the water balance model which prioritise the requirements of major stakeholders (hydropower, agriculture, and the lake ecosystem). A final option is developed, which shows that it is possible to balance the demands of these stakeholders. The implications of climate change are assessed by forcing meteorological inputs to the catchment and water balance models based upon a number of climate scenarios. In the majority of these scenarios, river inflows increase resulting in higher lake water levels that could further exacerbate ecological degradation of the lake as well as enhancing flooding of lakeside communities. The elevated water levels may permit additional irrigation abstractions however existing infrastructure limits increases in hydropower generation. The sustainability of the barrage operation options in the face of climate change is assessed. Results suggest that climate change is likely to limit the ability of barrage management to satisfy hydropower and agricultural demands whilst at the same time establishing a more ecologically appropriate lake water level regime.

In recent years, the increasing awareness of scarcity of water resources, indications of likely climate variability, and the increasing pressure to use available fresh water resources more efficiently have together reinforced the need to look at infrastructure solutions with due regard to environmental considerations and social impacts, present and future. There is a vital need to apply an integrated approach to catchment management to implement sustainable solutions to resolve issues such as water supply and sewerage, drainage and river flooding. Many potentials solutions are available to control water demand and manage flood problems. Greywater recycling and rainwater harvesting are novel technologies. However, their catchment scale impacts on hydraulic and hydrological flows are poorly understood. The research aim is to identify the hydrologic and hydraulic impacts of scaling up such technologies at catchment scale. For this particular study, a computer simulation model will be used to evaluate how increasing urbanisation, climate change and the implementation of greywater recycling and rainwater harvesting may alter the water balance within a representative catchment. To achieve these aims data from the Carrickmines catchment in Ireland have been collected; a simulation model has been adapted to carry out the study, the model has been calibrated and validated, results have been analysed, and finally, a sensitivity analysis has been carried out. The results show that rainwater harvesting systems are comparatively more effective than greywater recycling techniques in reducing flood frequency and intensity. Under five year return period rainfall events, the implementation of rainwater harvesting at any scale and number of units is a useful technique to control river flow and floods. However, the study also shows that under extreme conditions the efficiency of rainwater harvesting systems decreases. The study concludes that implementing the two technologies within a single catchment is not a solution to several forms of hydrological problem. The study shows that implementing rainwater harvesting or re-use technologies are a very useful way to protect local freshwater reserves and therefore conserve our environment.

The water quality deteriorations in river and estuarine waters are a global issue. Particularly, the water quality impairment due to contamination of Faecal Bacteria Indicator, such as E. coli and Faecal Coliform in river channel, estuary bathing and shellfish waters are of special interests due to potential risks to human health. These indicators are important in water quality assessment outlined in both EU Water Framework Directive and US Clear Water Act. The hypothesis of the study is that the global climate change and intensive farming would cause severe deterioration to faecal coliform levels in these water bodies. Approaches to quantify these impacts are carried out with numerically modelling through catchment model Soil and Water Assessment Tool (SWAT) and hydrodynamic model DIVAST with the focus in the coastal catchment of river Frome and Piddle connected to a natural harbour in Dorset, southern England.

Conventional hydrological compartmental models have been shown to exhibit a high degree of uncertainty for predictions of peak flows, such as the design floods for design of hydropower infrastructure. One reason for these uncertainties is that conventional models are parameterised using statistical methods based on how catchments have responded in the past. Because the rare occurrence of peak flows, these are underrepresented during the periods used for calibration. This implies that the model has to be extrapolated beyond the discharge intervals where it has been calibrated. In this thesis, hydromechanical approaches are used to investigate the properties of stream networks, reflecting mechanisms including stage dependency, damming effects, interactions between tributaries (network effects) and the topography of the stream network. Further, it is investigated how these properties can be incorporated into the streamflow response functions of compartmental hydrological models. The response of the stream network was shown to vary strongly with stage in a non-linear manner, an effect that is commonly not accounted for in model formulation. The non-linearity is particularly linked to the flooding of stream channels and interactions with the flow on flood-plains. An evaluation of the significance of using physically based response functions on discharge predictions in a few sub-catchments in Southern Sweden show improvements (compared to a conventional model) in discharge predictions – particularly when modelling peak discharges. An additional benefit of replacing statistical parameterisation methods with physical parameterisation methods is the possibility of hydrological modelling during non-stationary conditions, such as the ongoing climate change.
QC 20101022

In hydrological and hydraulic modelling, river geometry is a crucial input data. Recent investigations have been looking at methods to improve the description of cross sections extracted by DEM derived by satellite images. SRTM derived DEM are often lacking precise information as the sensors cannot detect the submerged river parts, but, on the other hand, it is available on a global scale which makes it very attractive and useful, especially in data scarce regions. This study aims at applying the so called “slope break” method to improve river cross section geometry extracted from SRTM DEM. The report is divided into three parts: a) The making of a Matlab-code to improve cross sections geometry extracted by satellite derived DEM; b) an application of the code to real cross-sections from the river Po in Italy and c) hydraulic simulations with and without SRTM modified cross sections to test the performance of the method, in collaboration with senior colleagues. The Matlab successfully performs the slope break point and finds, when appropriate, the approximated lowest point zmin of the cross section below the water surface. The comparison of the river geometry of the modified SRTM cross sections versus LiDAR available cross sections show the good performance of the method in improving the river geometry description. This code can simplify the work and improve many SRTM river cross sections in an effective way. The hydraulic simulations performed with and without the modified cross sections show how the modified SRTM model improves when compared to LiDAR results

This study developed an innovative stormwater quality treatment design framework for effective mitigation of urban stormwater pollution. The research method is primarily based on a stormwater quality modelling exercise and an extensive statistical analysis for defining the relationships among rainfall, catchment and stormwater quality characteristics. The identified relationships were translated into a framework, enabling the determination of rainfall parameters and treatment system design specifications. Adopting this framework will enhance treatment system performances leading to greater protection of aquatic ecosystems.

La hidrologia històrica quantitativa és una branca emergent de les ciències de la Terra que es basa en l’ús d’informació històrica (és a dir, informació produïda per les persones: documents, imatges, limnimarques) per a reconstruir el cabal pic de riuades antigues. Aquesta ciència multidisciplinària (molt propera, en concepte, a la paleohidrologia) utilitza mètodes d’historiografia, hidràulica, hidrologia, meteorologia, climatologia, estadística i, fins i tot, de les ciències socials, i té moltes aplicacions útils, no només en la planificació del risc d’inundacions, sinó també en la recerca hidrològica bàsica. Malgrat tot plegat, la hidrologia històrica quantitativa no s’ha convertit, de moment, en una eina d’ús general a Catalunya i a la conca de l’Ebre. Aquesta tesi desenvolupa algunes de les grans possibilitats de la hidrologia històrica quantitativa tot aplicant-la en diversos casos d’estudi en diferents conques de Catalunya i la conca de l’Ebre. La conclusió final és que l’ús de la hidrologia històrica millora la prevenció i la gestió del risc de riuades, tant en conques aforades com no aforades de la zona estudiada.
Era idrologia istorica quantitativa ei ua branca emergenta des sciéncies dera Tèrra que se base en emplec d’informacion istorica (ei a díder, informacion produsida pes persones: documents, imatges, limnimarques) entà rebastir eth cabau pic d'aiguats ancians. Aguesta sciéncia multidisciplinària (fòrça propèra, en concèpte, ara paleoidrologia) emplegue metòdes d’istoriografia, idraulica, idrologia, meteorologia, climatologia, estadistica e, autaplan, des sciéncies sociaus, e a fòrça aplicacions utiles, non sonque ena planificacion deth risc d’inondacions, mès tanben ena recèrca idrologica basica. Maugrat tot aquerò, era idrologia istorica quantitativa non s’a convertit, de moment, en un utís d’emplec generau en Catalonha e ena conca der Ebre. Aguesta tèsi desvolòpe bères ues des granes possibilitats dera idrologia istorica quantitativa en tot aplicar-la en diuèrsi casi d’estudi enes diferentes conques de Catalonha e dera conca der Ebre. Era conclusion finau ie qu’er emplec dera idrologia istorica melhore era prevencion e era gestion deth risc d’inondacions, tant en conques aforades coma no aforades dera zòna estudiada.
La hidrología histórica cuantitativa es una rama emergente de las ciencias de la Tierra que se basa en el uso de información histórica (es decir, información producida por las personas: documentos, imágenes, limnimarques) para reconstruir el caudal pico de riadas antiguas. Esta ciencia multidisciplinaria (muy próxima, en concepto, a la paleohidrología) utiliza métodos de historiografía, hidráulica, hidrología, meteorología, climatología, estadística e, incluso, de las ciencias sociales, y tiene muchas aplicaciones útiles, no sólo en la planificación del riesgo de inundaciones, sino también en la investigación hidrológica básica. A pesar de todo ello, la hidrología histórica cuantitativa no se ha convertido, de momento, en una herramienta de uso general en Cataluña y en la cuenca del Ebro. Esta tesis desarrolla algunas de las grandes posibilidades de la hidrología histórica cuantitativa aplicándola en varios casos de estudio en diferentes cuencas de Cataluña y la cuenca del Ebro. La conclusión final es que el uso de la hidrología histórica mejora la prevención y la gestión del riesgo de inundaciones, tanto en cuencas aforadas como no aforadas de la zona estudiada.
Quantitative historical hydrology is an emerging branch of Earth sciences that is based on the use of historical information (that is, man-made pieces of information: documents, pictures, flood marks) to reconstruct the peak flows of long-past floods. This multidisciplinary science (which is very close in concept to paleohydrology) uses methods from historiography, hydraulics, hydrology, meteorology, climatology, statistics, and even social sciences, and is full of possible useful applications, not only in flood risk management but also in basic hydrological research. However, quantitative historical hydrology is not being generally used in Catalonia or the Ebro River basin so far. This thesis develops some of the huge possibilities of quantitative historical hydrology by applying it to several study cases in different catchments in Catalonia and the Ebro River basin. The final conclusion is that the use of historical hydrology improves flood risk prevention and management, both in gauged and ungauged catchments within the studied area.

This Thesis focues on two main research topics: (1) the use of innovative techniques for the evaluation of main hydraulic variables of natural rivers (e.g. river bathymetry, discharge, water level) and (2) the monitoring and hydrological modelling of Monate Lake (Varese, Italy).

Technological advances in computer science, namely cloud computing and data mining, are reshaping the way the world looks at data. Data are becoming the drivers of discoveries and strategic developments. In environmental sciences, for instance, big volumes of information are produced by monitoring networks, satellites and model simulations and are processed to uncover hidden patterns, correlations and trends to, ultimately, support policy and decision making. Hydrologists, in particular, use models to simulate river discharges and estimate the concentration of pollutants as well as the risk of floods and droughts. The very first step of any hydrological modelling exercise consists of selecting an appropriate model. However, the choice is often made by the modeller based on his/her expertise rather than on the model's suitability to reproduce the most important processes for the area under study. Since this approach defeats the ''scientific method'' for its lack of reproducibility and consistency across experts as well as locations, a shift towards a data-driven selection process is deemed necessary. This work presents the design, development and testing results of a completely novel data mining algorithm, called AMCA, able to automatically identify the most suitable model configurations for a given catchment, using minimum data requirements and an inventory of model structures. In the design phase a transdisciplinary approach was adopted, borrowing techniques from the fields of machine learning, signal processing and marketing. The algorithm was tested on the Severn at Plynlimon flume catchment, in the Plynlimon study area (Wales, UK). This area was selected because of its reliable measurements and the homogeneity of its soils and vegetation. The Framework for Understanding Structural Errors (FUSE) was used as sample model inventory, but the methodology can easily be adapted to others, including more sophisticated model structures. The model configuration problem, that the AMCA attempts to solve, can be categorised as ''fully unsupervised'' if there is no prior knowledge of interactions and relationships amongst observed data at a certain location and available model structures and parameters. Therefore, the first set of tests was run on a synthetic dataset to evaluate the algorithm's performance against known outcomes. Most of the component of the synthetic model structure were clearly identified by the AMCA, which allowed to proceed with further testing using observed data. Using real observations, the AMCA efficiently selected the most suitable model structures and, when coupled with association rule mining techniques, could also identify optimal parameter ranges. The performance of the ensemble suggested by the combination of AMCA and association rules was calibrated and validated against four widely used models (Topmodel, ARNOVIC, PRMS and Sacramento). The ensemble configuration always returned the best average efficiency, characterised by the narrowest spread and, therefore, lowest uncertainty. As final application, the full set of FUSE models was used to predict the effect of land use changes on catchment flows. The predictive uncertainty improved significantly when the prior distributions of model structures and parameters were conditioned using the AMCA approach. It was also noticed that such improvement is due to constrains applied to both model and parameter space, however the parameter space seems to contribute more. These results confirm that a considerable part of the uncertainty in prediction is due to the definition of the prior choice of the model configuration and that more objective ways to constrain the prior using formal data-driven techniques are needed. AMCA is, however, a procedure that can only be applied to gauged catchment. Future experiments could test whether AMCA configurations could be regionalised or transferred to ungauged catchments on the basis of catchment characteristics.

Testing and trying out of the applicability and utility of watershed hydrological models in different; catchment sizes, hydro-geologic conditions, soil conditions and with different time resolutions is necessary for a range of spatial scales to assess the utility of these models in water shade management means like flood protection, land slide prevention, erosion control etc. The main purpose of this thesis is to tryout TOPLAND hydrological model, i.e. the new developments to the LANDPINE model allowing for using TOPMODEL distributed runoff generation, with different precipitation input methods. It focuses on the simulation of precipitation events with time resolution of one hour. Short term time resolution event simulations are important to capture flow events in small and large catchments; since these events are responsible for local flood, land slide etc., especially in areas where they are strongly localized. The model simulation has been carried out using three different precipitation input methods; gauge IDW interpolation, gauge simulated and radar based precipitation data for the selected hourly events of 2006 (27-07-2006 00:00 to 29-07-2006 23:00) and 2009 (19-07-2009 05:00 to 25-07-2009 20:00). 2009 Event The 2009 event is characterized by high peak and uniformly distributed event. For the bias corrected radar precipitation, the objective method of result comparison showed an excellent correspondence between observed and simulated flows with NS (R2) of 0.98, correlation (R2) of 0.98 and PBIAS of 0.48% at the calibration point (Gaulfoss). The bias corrected radar precipitation also showed a very good performance of the model at the interior uncalibrated gauging stations with average values of NS (R2) 0.85, correlation (R2) 0.93 and PBIAS 16.6% of the HugdalBru, Lillebudal and Eggafoss gauging stations. The gauge IDW interpolation and gauge simulated precipitation input methods also showed a very good performance of the model both at the calibration and internal uncalibrated gauging stations. 2006 Event The 2006 event is characterized by low peak and unevenly distributed (localized) event. The bias corrected radar precipitation is the only precipitation input method that made possible for calibration of the model. The objective method of result comparison showed a very good result for NS (R2) of 0.96, correlation (R2) of 0.97 and PBIAS of 5.1% at the calibration point (Gaulfoss). At the internal uncalibrated gauging stations, the correlation and PBIAS showed a good performance with average correlation (R2) of 0.77 and PBIAS of 21.3% and a poor average NS (R2) of 0.3.

In many areas of the world, the absence of streamflow data to calibrate hydrological models limits the ability to make reliable streamflow predictions. Whilst a large and increasing number of regions are insufficiently gauged, there are also many highly monitored catchments. Transferring the knowledge gained in data-rich areas to data-scarce regions offers possibilities to overcome the absence of streamflow observations. In this thesis knowledge is transferred in the form of signatures, which reflect hydrological response characteristics of a particular catchment. Several signatures may be required to capture different aspects of catchment functional behaviour. Using a large dataset of catchments, observed signatures are regressed against physical and climatic catchment descriptors. Signatures for an ungauged location with known descriptors are then estimated utilising the derived relationships. A Bayesian procedure is subsequently used to condition a conceptual model for the ungauged catchment on the estimated signatures with formal uncertainty estimation. Particular challenges related to the Bayesian approach include the selection of signatures, and specification of the prior distribution and the likelihood functions. A methodological development is based on an initial transformation of the commonly adopted uniform parameter prior into a prior that maps to a uniform signature distribution, aimed at cases where limited prior knowledge regarding the model structure adequacy and the parameters distribution exist. The suggested methodology contributes to improved estimation of response signatures, and is particularly relevant when regionalised information is highly uncertain. A further contribution of this thesis refers to the integration of several regionalised signatures into the model, accounting for the inter-signature error covariance structure. By increasing the number and regionalisation quality of signatures in the conditioning process, better predictions are obtained. Additionally, the consideration of the inter-signature error structure may improve the results when correlations between errors are shown to be strong. When regionalised signatures are integrated into the model, it is shown that model structural inadequacy has a strong effect on the prediction quality.

The aim of this thesis was to test and evaluate whether parameter regionalization of a hydrological model can be used to model the impact of forest clearcutting on streamflow in Sweden. This is an important task to be able to perform water management and impact assessments adequately. The HBV conceptual rainfall-runoff model was applied for 218 Swedish catchments of different sizes that were spread across the country and covered a wide range of different forest cover percentages. The modelling approach included calibration of the model for each catchment using a genetic algorithm and then associating the resulting optimal parameter values with the percentage of forest cover. The obtained relationship between different model parameters and forest cover was validated with help of a paired catchment study site in northern Sweden where a clear cut was done in 2006: calibrated optimal parameter sets of pre- and post-clearcutting conditions were compared to parameter sets obtained from the Sweden-wide analysis. Correlations were found for about half of the fifteen hydrological model parameters, but the validation with the paired catchment study site could only partially confirm these obtained relationships. The results suggest that the adopted parameter regionalization approach is too basic. However, some of the results seem promising and emphasize the need for further research and development of the approach to provide a more reasonable method to model the impact of forest clearcutting on streamflow.
Det huvudsakliga målet med detta examensarbete var att testa och utvärdera om parameterregionalisering av en hydrologisk modell kan vara en lämplig metod för att modellera och kvantifiera påverkan från skogsavverkning på vattenbalansen i Sverige. Detta är en viktig uppgift för att kunna hantera våra vattenresurser och utföra konsekvensanalyser på ett tillfredsställande sätt. En konceptuell hydrologisk modell tillämpades på 218 avrinningsområden av olika storlekar och som var geografiskt utspridda i hela Sverige där även andelen skog i avrinningsområdena hade ett brett spektrum. Den använda modelleringsmetoden innefattade kalibrering av varje avrinningsområde genom att använda en genetisk algoritm, varefter de optimala parametervärdeana korrelerades mot andelen skog i avrinningsområdet. Idén med denna metod är att använda dessa potentiella samband för att justera modellparametrarna och därmed simulera en skogsavverkning. De erhållna sambanden mellan modellparametrarna och skogstäcket validerades med hjälp av data från en försöksstudie i norra Sverige där en skogsavverkning gjordes under 2006. Skillnaden mellan de bäst fungerande parametervärdena före och efter skogsavverkningen jämfördes med de tidigare sambanden från andra avrinningsområden i Sverige. Signifikant korrelation hittades för ungefär hälften av de 15 hydrologiska modellparametrarna, men valideringen mot den riktiga skogsavverkningen kunde bara delvis bekräfta de erhållna sambanden. Resultaten visar att detta sätt att använda parameterregionalisering antagligen är för grundläggande. Vissa resultat är ändå lovande och fortsatt forskning och utvidgning av metoden är nödvändig för att kunna tillhandahålla en rimlig metod för att kvantifiera en skogsavverknings effekter på vattenbalansen.

There is currently worldwide interest in the effect of human activity on tile global environment, especially the effect of greenhouse gases and land-use change on the global climate, and models are being developed to study both global change and the local effects of global change. The research reported here (funded by CNPq-Brazil) involves the development of GRASP:Groundwater Recharge modelling Approach with a Scaling up Procedure. GRASP has been integrated into the UP (Upscaled Physically-based) macromodel, developed under the UK NERC TIGER programme, which is designed for studying the effects of climate and land-use change on the availability and quality of water resources. The UP macromodel will be coupled to the UK Meteorological. Office's Unified (weather and climate) model to create a state-of-the-art coupled atmospheric/hydrological model. Several important requirements for the design of new large-scale hydrological models are identified in a wide ranging review on GCMs; (General Circulation Models) and physically -based hydrological modelling, and these requirements have been applied in the development of GRASP(and UP). The main requirements are a physical basis, proper treatment of spatial variability, and simplicity. Using the concept of partial analysis, two point-scale models, SM (Soil Moisture content approach) and TF (Transfer Function approach), are developed for recharge, both based on the one-dimensional Richards' equation. SM is a simple two-parameter model relating recharge to water storage in the unsaturated zone, and several unsuccessful attempts are made to link its parameters to physical propcrties. TF is a transfer function model, and is parameterised using the matric potential and unsaturated hydraulic conductivity functions using a new approach developed especially for GRASP. Both SM and TF are verified against numerical solutions of Richards' equation.

NewAge-JGrass system for forecasting and modelling of water resources in general at the basin scale. As a modern hydrological modelling, it is composed of two parts: (i) the system for data and results visualization based on the Geographic Information System uDig and (ii) the component based modelling system. All the system is based on Java because of its portability. Java is a modern and mature language aware of the web and has features such as multithreading that are essential to build scalable modelling platform. There are a few open source frameworks available that allow adaptation for our task, such as the GeoTools project by the Open GIS Consortium, representing a solid foundation for spatial analysis. OMS was chosen for facilitating model connectivity because of it low invasiveness in code practice and capability in production of leaner and more descriptive modelling code . uDig as visualization/GIS platform, including GIS services, and its integration with the JGrass GIS, developed by http://udig.refractions.net/, offers a spatial toolbox which contains the features previously offered by JGrass. Compared to traditional hydrological models, which are built upon monolithic code, JGrass-NewAge allows for multiple modelling solutions for the same physical process, provided they share similar input and outputs constraints. Modeling components are connected by means of a concise scripting language NewAge-JGrass components can be grouped in several categories. The geomorphic and DEM analyses which solves the problem of basin delineation; the tools for making spatial extrapolation/interpolation of the meteorological data; the estimation of the radiation forcing; the estimation of evapotranspiration; the estimation of the runoff production; the channel routing and tools for automatic model parameter calibration such as DREAM, Particle Swarm and LUCA. NewAge requires interpolated meteorological variables (such as air temperature, precipitation, and relative humidity) as input data for each hillslope. They can be computed by a deterministic or geostatistic approaches. The energy model includes both, shortwave and longwave radiation calculation components for each hillslope. The first implements algorithms that take into account shade and complex topography and cloud cover. Evapotraspiration can be modelled using two different solutions: the Fao-Evapotraspiration model and the Priestley-Taylor model. A snow melting and snow water equivalent model is also part of the system. Duffy's model and Hymod model are the runoff production models implemented in NewAge. In both cases the model is applied for each hillslope. Finally, the discharge generated at each hillslope is routed to each associated stream link. Modeling solutions (connections of different components) are applied in three different river basin and verifications against measured data (discharge, radiation fluxes, snow water equivalent) are presented by using traditional goodness of fitting indices.

NewAge-JGrass system for forecasting and modelling of water resources in general at the basin scale. As a modern hydrological modelling, it is composed of two parts: (i) the system for data and results visualization based on the Geographic Information System uDig and (ii) the component based modelling system. All the system is based on Java because of its portability. Java is a modern and mature language aware of the web and has features such as multithreading that are essential to build scalable modelling platform. There are a few open source frameworks available that allow adaptation for our task, such as the GeoTools project by the Open GIS Consortium, representing a solid foundation for spatial analysis. OMS was chosen for facilitating model connectivity because of it low invasiveness in code practice and capability in production of leaner and more descriptive modelling code . uDig as visualization/GIS platform, including GIS services, and its integration with the JGrass GIS, developed by http://udig.refractions.net/, offers a spatial toolbox which contains the features previously offered by JGrass. Compared to traditional hydrological models, which are built upon monolithic code, JGrass-NewAge allows for multiple modelling solutions for the same physical process, provided they share similar input and outputs constraints. Modeling components are connected by means of a concise scripting language NewAge-JGrass components can be grouped in several categories. The geomorphic and DEM analyses which solves the problem of basin delineation; the tools for making spatial extrapolation/interpolation of the meteorological data; the estimation of the radiation forcing; the estimation of evapotranspiration; the estimation of the runoff production; the channel routing and tools for automatic model parameter calibration such as DREAM, Particle Swarm and LUCA. NewAge requires interpolated meteorological variables (such as air temperature, precipitation, and relative humidity) as input data for each hillslope. They can be computed by a deterministic or geostatistic approaches. The energy model includes both, shortwave and longwave radiation calculation components for each hillslope. The first implements algorithms that take into account shade and complex topography and cloud cover. Evapotraspiration can be modelled using two different solutions: the Fao-Evapotraspiration model and the Priestley-Taylor model. A snow melting and snow water equivalent model is also part of the system. Duffy's model and Hymod model are the runoff production models implemented in NewAge. In both cases the model is applied for each hillslope. Finally, the discharge generated at each hillslope is routed to each associated stream link. Modeling solutions (connections of different components) are applied in three different river basin and verifications against measured data (discharge, radiation fluxes, snow water equivalent) are presented by using traditional goodness of fitting indices.

The recent high profile flooding events – that have occurred in many parts of the world – have drawn attention to the need for new and improved methods for water resources assessment, water management and the modelling of large-scale flooding events. In the case of the Zambezi Basin, a review of the 2000 and 2001 floods identified the need for tools to enable hydrologists to assess and predict daily stream flow and identify the areas that are likely to be affected by flooding. As a way to address the problem, a methodology was set up to derive catchment soil moisture statistics from Earth Observation (EO) data and to study the improvements brought about by an assimilation of this information into hydrological models for improving reservoir management in a data scarce environment. Rainfall data were obtained from the FEWSNet Web site and computed by the National Oceanic and Atmospheric Administration Climatic Prediction Center (NOAA/CPC). These datasets were processed and used to monitor rainfall variability and subsequently fed into a hydrological model to predict the daily flows for the Zambezi River Basin. The hydrological model used was the Geospatial Stream Flow Model (GeoSFM), developed by the United States Geological Survey (USGS). GeoSFM is a spatially semi-distributed physically-based hydrological model, parameterised using spatially distributed topographic data, soil characteristics and land cover data sets available globally from both Remote Sensing and in situ sources. The Satellite rainfall data were validated against data from twenty (20) rainfall gauges located on the Lower Zambezi. However, at several rain gauge stations (especially those with complex topography, which tended to experience high rainfall spatial variability), there was no direct correlation between the satellite estimates and the ground data as recorded in daily time steps. The model was calibrated for seven gauging stations. The calibrated model performed quite well at seven selected locations (R2=0.66 to 0.90, CE=0.51 to 0.88, RSR=0.35 to 0.69, PBIAS=−4.5 to 7.5). The observed data were obtained from the National Water Agencies of the riparian countries. After GeoSFM calibration, the model generated an integration of the flows into a reservoir and hydropower model to optimise the operation of Kariba and Cahora Bassa dams. The Kariba and Cahora Bassa dams were selected because this study considers these two dams as the major infrastructures for controlling and alleviating floods in the Zambezi River Basin. Other dams (such as the Kafue and Itezhi-Thezi) were recognised in terms of their importance but including them was beyond the scope of this study because of financial and time constraints. The licence of the reservoir model was limited to one year for the same reason. The reservoir model used was the MIKE BASIN, a professional engineering software package and quasi-steady-state mass balance modelling tool for integrated river basin and management, developed by the Denmark Hydraulic Institute (DHI) in 2003. The model was parameterised by the geometry of the reservoir basin (level, area, volume relationships) and by the discharge-level (Q-h) relationship of the dam spillways. The integrated modelling system simulated the daily flow variation for all Zambezi River sub-basins between 1998 and 2008 and validated between 2009 and 2011. The resulting streamflows have been expressed in terms of hydrograph comparisons between simulated and observed flow values at the four gauging stations located downstream of Cahora Bassa dam. The integrated model performed well, between observed and forecast streamflows, at four selected gauging stations (R2=0.53 to 0.90, CE=0.50 to 0.80, RSR=0.49 to 0.69, PBIAS=−2.10 to 4.8). From the results of integrated modelling, it was observed that both Kariba and Cahora Bassa are currently being operated based on the maximum rule curve and both remain focused on maximising hydropower production and ensuring dam safety rather than other potential influences by the Zambezi River (such as flood control downstream – where the communities are located – and environmental issues). In addition, the flood mapping analysis demonstrated that the Cahora Bassa dam plays an important part in flood mitigation downstream of the dams. In the absence of optimisation of flow releases from both the Kariba and Cahora Bassa dams, in additional to the contribution of any other tributaries located downstream of the dams, the impact of flooding can be severe. As such, this study has developed new approaches for flood monitoring downstream of the Zambezi Basin, through the application of an integrated modelling system. The modelling system consists of: predicting daily streamflow (using the calibrated GeoSFM), then feeding the predicted streamflow into MIKE BASIN (for checking the operating rules) and to optimise the releases. Therefore, before releases are made, the flood maps can be used as a decision-making tool to both assess the impact of each level of release downstream and to identify the communities likely to be affected by the flood – this ensures that the necessary warnings can be issued before flooding occurs. Finally an integrated flood management tool was proposed – to host the results produced by the integrated system – which would then be accessible for assessment by the different users. These results were expressed in terms of water level (m). Four discharge-level (Q-h) relationships were developed for converting the simulated flow into water level at four selected sites downstream of Cahora Bassa dam – namely: Cahora Bassa dam site, Tete (E-320), Caia (E-291) and Marromeu (E-285). However, the uncertainties in these predictions suggested that improved monitoring systems may be achieved if data access at appropriate scale and quality was improved.

The objective of this thesis is to develop a model that represents the dynamics of a hydraulically operated forestry crane. The model was derived with the traditional Euler-Lagrange formalism and considers the crane mechanics, three double-acting hydraulic cylinders and the valve control unit. On the basis of the derived model we reproduced the entire crane model in MATLAB in order to run simulations herewith. This gave us the possibility to do parameter changes for further studies of the crane in motion.

Another major goal within the thesis work was to estimate cylinder friction of the hydraulic actuators. We built up a test rig and used double-acting cylinders for determing their frictional behaviour. For this, we ran open-loop experiments in order to create velocity-friction maps that represented the static friction force of the cylinders. In this concern, we varied system pressure and cylinder load to study their influence on the friction force. By means of the derived static friction maps we approached the cylinder’s dynamic friction behaviour and applied both step and ramp control inputs to examine the spring-damping characteristics of the microspoic bristles in the contacting area. The dynamic friction experiments have been exerted in the fashion of the LuGre model. As a result we acquired different nominal friction parameters that we necessarily used to develope adequate friction models.

A third objective of this thesis was to establish a crane-tip control. Instead of a traditional control, providing a direct relationship between joystick input and cylinder extension, the focus was to build up a control for the end-effector’s trajectory in a two-dimensional frame. This could be achieved by using inverse kinematics in order to determine the required joint angles that corresponded to the desired position of the crane-tip.

The work also contains a CD including all developed MATLAB models that have been written within this project.

This Master’s Thesis work deals with the development of improved hydro turbine models for the evaluation of a hydraulic power generating system performance in response to small disturbances in power system analysis tool. These improved models must be able to reflect the possible interaction between the hydraulic system and power system in the computer simulations of a power plant equipped with Francis turbines.The accuracy of a Hydraulic Power Generating System is studied by means of analysis of the dynamic behaviour of different models of the hydraulic machine and conduit system. The stability study of different models for Synchronous Machines and Turbine Governing System are beyond the scope of this work.Appropriate representations of the hydraulic turbine and conduit system are developed in various models of varying degrees of detail. Firstly, nonlinear models for a simple turbine without surge tank considering the inelastic and elastic travelling wave effects have been developed. After that, nonlinear models considering the inelastic and elastic travelling wave effects for a turbine with surge tank for Hydropower Systems with long length penstocks are implemented. Finally, the nonlinear models for a turbine with long length penstocks are linearized at an operating point considering both the nonlinear turbine characteristics and the travelling wave effects.The Master’s Thesis work is divided into three parts. The first part, comprising Chapters 2 to 8, reviews the physical characteristics and mathematical models of the components of a hydraulic power generating system. The influence of each component of the power system by means of appropriate mathematical models is essential for the understanding of system stability. The second part, comprising Chapters 9 to 11, deals with the dynamic study of the system stability characteristics of the different hydraulic power generating system models implemented in SIMPOW and LVTrans. Finally, the third part, Chapter 12 and Chapter 13, presents the discussion of the simulation results of the hydroelectric power system models, and draws general conclusions on this work and suggests possibilities for the approach further work, respectively.It was concluded that approaches based on nonlinear and linear models including the elasticity of the conduit system and the nonlinear turbine characteristics extracted from the Hill Charts, are the most accurate models for any acceptable study of the interaction between hydraulic system and power system.The study of dynamic performance and interaction between the hydraulic system and power system of these extended linear and nonlinear models including the elastic water hammer effect and varying the nonlinear characteristics of the hydraulic turbine must be studied in detail.

To meet the increasing demand on control precision in industrial forklifts, physical modelling of the lifting system has been combined with parameter estimations from data. A number of different controllers have been evaluated in terms of their ability to achieve a load independent lifting speed. The model and controller performance as well as stability properties were evaluated in simulations, and the most promising controller was implemented on the real system. Especially the electric motor turned out to be difficult to model, and therefore experimental data was used to approximate some parts of it. This, along with some friction parameters that had to be estimated caused a slight loss in model generality. An observer (Extended Kalman filter) was used to estimate the unknown states, including the velocity of the forks. The simulated performance of the MPC controller was slightly better than the PID controller, except for a bigger overshoot when starting from a turned off motor. The PID controller also handles model errors better, because of its integral action. Due to the simplicity in relation to performance, only the PID controller was implemented on the forklift. The model turned out to perform well, but not well enough to estimate the lifting height accurately. The PID controller worked as intended and it could therefore be concluded that a more advanced control algorithm, such as an MPC controller, is not necessary for this system.

The Hydraulic Fracturing process and its engineering applications have been studied and reported in this thesis. The Distinct Element Method (DEM) was adopted as the main and preferred numerical technique because of its distinctive features and advantages. This method allows the phenomenon to be modelled and viewed microscopically at the inter-particle level by conceptualising the rock mass as an assembly of discrete particles interacting with each other via contacts. This method allows for a more detailed and dynamic monitoring of the hydraulic fracturing process. Sequel to a detailed review on the study of the hydraulic fracturing phenomenon, the research was extended to investigate specific cases of applications of hydraulic fracturing in geo-mechanical and environmental problems. Examples of such cases include carbon dioxide injection and storage in a reservoir system, and the behaviour of naturally occurring faults subjected to hydrostatic fluid pressures. The key factors governing the geo-mechanical responses of porous media (rocks), including reservoir formations were identified and further examined to ascertain the following: the role and inter-relationship between operating and material/fluid variables such as injection flow rate, fluid pressure, and interstitial velocity; type and pattern of fracture propagation; influence of environmental conditions as well as the configuration of the well-reservoir system, amongst others. Because of broad similarities in enabling conditions, analyses and applications of the phenomenon were also extended to study the sand production process. However, since the emphasis of the study was on identifying and examining the controlling variables as well as establishing patterns of sanding production rates rather than the study of the cavitation process, investigations were conducted using a finite element procedure; moreover, the limit of computational capacity has prevented a large scale DEM model for such problems. Modelling results show that fracturing mode, pattern and intensity are highly dependent on operating and environmental conditions; the reservoir erosion processes also indicate likewise tendencies. The numerical modelling techniques adopted and results obtained facilitate an improved understanding of geo-mechanical mechanisms at sub-surface systems, and could be further improved for industrial applications, such as site evaluation and assessment of the efficiency of stimulation techniques.

During the past few decades, substantial improvements were made to rail infrastructure worldwide. This was necessary to accommodate the ever increasing transportation demand and requirements. Nowadays, trains are required to transport heavier loads and to travel at higher speeds. One of the major improvements was achieved by the development of the off-flange curving bogie designs to reduce wheel and rail wear. Off-flange designs include passive steering and actively controlled steering. The development and implementation of self-steering bogies on locomotives was promoted in the early 1980’s by two major locomotive manufacturers. Up to date, thousands of these locomotives, with built-in self-steering bogies, have been manufactured and taken into service (Swenson, 1999). Most self-steering bogies have mechanical linkage systems to steer the wheel sets. As an alternative to the mechanical linkage system, the DCD Group (a South African manufacturer of rail and mining equipment) initiated the development of a Passive Hydraulic Steering (PHS) system. First PHS prototype systems, developed by DCD, have proven that huge wear reduction possibilities exist on both, rails and wheels. In addition the prototype systems also significantly decreased noise and vibration levels when negotiating tight corners (Swenson & Scott, 1996 and DCD Rolling Stock, 2012). However, existing prototype solutions require further improvements and development for optimisation. To be able to identify and implement improvements, the need exists to perform modelling and testing of the systems to obtain a better understanding of the operation and suitability of a complete unit. The aim of this research project is thus, to mathematically model an existing prototype PHS system and validate the model with data from experiments and tests. This model can then be used in order to improve and optimise performance, cost and reliability of the system, before mass production is considered. A literature survey was conducted, focusing on general wheel and rail wear mechanisms, techniques to improve wheel and rail life and on existing techniques for modelling the hydraulics and multi-body dynamics of locomotive systems. The literature survey was followed by extensive laboratory tests on component basis, a quarter PHS system and on the full PHS system. From these tests all parameters needed for the characterisation of the PHS and the mathematical model were determined. These tests also provided data for the validation of the PHS model. Finally, a mathematical model of the PHS system was successfully generated and validated. This model can now be used in a multi-body dynamic locomotive simulation to evaluate its effectiveness. The results and findings of the literature survey, experiments and modelling are reported on and discussed in this report.
Dissertation (MEng)--University of Pretoria, 2015.
tm2015
Mechanical and Aeronautical Engineering
MEng
Unrestricted

A physically-based, distributed sediment yield component has been developed for the SHE hydrological modelling system. This new component models the hillslope processes of soil detachment by raindrop impact, leaf drip impact and overland flow, and transport by overland flow. If the eroded soil reaches a river system it is routed downstream along with any inobilised river bed material. Deposition on land or in a river is simulated and the river bed material size distribution is continuously updated with allowance for armour layer development. The equation developed for soil detachment by raindrop and leaf drip impact was successfully tested using data from a field plot with a range of soybean canopy covers and rainfall intensities. The soil detachment coefficient in this equation was determined for a range of soil types and showed a variation consistent with that which may be expected from a consideration of the physics of a soils resistance to detachment. At present two soil detachment coefficients need calibration. In order to investigate the variation in these coefficient values, as well as to test the component, various applications were carried out. The hilislope sub-component was applied to rainfall simulator plots with a variety of surface conditions. Two sets of calibration parameters, distinguishable on a physical basis according to the degree of soil disturbance, were found to be appropriate for all the plots. To investigate scale effects, parameters calibrated at the rainfall simulator plot scale were transferred to a 1-ha rangeland sub-catchment. With no further calibration, the catchmerit response for four events was poorly simulated for both water and sediment. However, with reasonable variations in the antecedent soil moisture content but no variation in plot calibrated sediment parameters, the sediment yield for two of the four events could be successfully simulated. These applications suggest that parameter transfer is feasible if the sediment yield characteristics at the different scales are similar. Further applications of the hilislope sub-component were carried out for two small agricultural catchments. The sediment response could be simulated to at least the same accuracy as achieved by two existing distributed soil erosion models. The channel sub-component was applied to the East Fork River, Wyoming. Although the complex sediment storage/supply effects could not be reproduced completely, the simulated response was nevertheless of similar accuracy to that achieved by two existing alluvial river models. The new component is considered to be a valuable contribution to sediment yield modelling as a physically-based approach is used for both the hilislope and channel phases of the catchinent sediment system, within the framework of an advanced hydrological modelling system.

The rigorous development, application and validation of distributed hydrological models obligates to evaluate data in a spatially distributed way. In particular, spatial model predictions such as the distribution of soil moisture, runoff generating areas or nutrient-contributing areas or erosion rates, are to be assessed against spatially distributed observations. Also model inputs, such as the distribution of modelling units derived by GIS and remote sensing analyses, should be evaluated against groundbased observations of landscape characteristics. So far, however, quantitative methods of spatial field comparison have rarely been used in hydrology.

In this paper, we present algorithms that allow to compare observed and simulated spatial hydrological data. The methods can be applied for binary and categorical data on regular grids. They comprise cell-by-cell algorithms, cell-neighbourhood approaches that account for fuzziness of location, and multi-scale algorithms that evaluate the similarity of spatial fields with changing resolution. All methods provide a quantitative measure of the similarity of two maps.

The comparison methods are applied in two mountainous catchments in southern Germany (Brugga, 40 km²) and Austria (Löhnersbach, 16 km²). As an example of binary hydrological data, the distribution of saturated areas is analyzed in both catchments. For categorical data, vegetation zones that are associated with different runoff generation mechanisms are analyzed in the Löhnersbach. Mapped spatial patterns are compared to simulated patterns from terrain index calculations and from satellite image analysis. It is discussed how particular features of visual similarity between the spatial fields are captured by the quantitative measures, leading to recommendations on suitable algorithms in the context of evaluating distributed hydrological models.

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Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung
Workshop vom 9. - 10. Februar 2006

Lake Tana Basin is of significant importance to Ethiopia concerning water resources aspects and the ecological balance of the area. The growing high demands in utilizing the high potentials of water resource of the Lake to its maximal limit, pictures a disturbing future for the Lake. The objective of this study was to assess the influence of topography, soil, land use and climatic varia-bility on the hydrological and hydrodynamic processes of the Lake Tana Basin. The physically based SWAT model was successfully calibrated and validated for flow and sediment yield. Se-quential uncertainty fitting (SUFI-2), parameter solution (ParaSol) and generalized likelihood un-certainty estimation (GLUE) calibration and uncertainty analysis methods were compared and used for the set-up of the SWAT model. There is a good agreement between the measured and simulated flows and sediment yields. SWAT and GIS based decision support system that uses multi-criteria evaluation (MCE) was used to identify the most vulnerable areas to soil erosion in the basin. The results indicated that 12 to 30.5% of the watershed is high erosion potential. Pro-jected changes in precipitation and temperature in the basin for two seasons were analyzed using outputs from fifteen global climate models (GCMs). A historical-modification procedure was used to downscale large scale outputs from GCM models to watershed-scale climate data. The results showed significant changes in streamflow and other hydrological parameters in the period between 2045-2100. SWAT was combined with a three dimensional hydrodynamic model, GEMSS to investigate the flow structure, stratification, the flushing time, lake water balance and finally the Lake‘s water level response to planned water removal. We have found an alarming and dramatic fall of the water levels in Lake Tana as response to the planned water withdrawal. The combination of the two models can be used as a decision support tools to better understand and manage land and water resources in watersheds and waterbodies. The study showed that the Lake Tana Basin may experience a negative change in water balance in the forthcoming decades due to climate change as well as over abstraction of water resources.
QC 20100720

A good understanding of the local and regional water cycle and how it is modified by landscape changes may help policymakers take the pertinent decisions in order to avoid adverse effects of future hydro–climatic changes. This knowledge is of particular interest in the most vulnerable areas of the world such as the African continent. In this context the aim of this project is to model hydrological responses to possible changes in climatic conditions in Lake Babati, northern Tanzania. For this reason a water balance model specially designed to simulate lake level changes was adapted to Lake Babati and calibrated with the available local meteorological and hydrological data record covering the last decades. The necessary ambient condition changes to produce a dry–out and an overflow of the lake were investigated and the response of the system to future IPCC climate change projections was studied. The results show that for instance a temperature change of less than 3ºC or a precipitation change of around 100 mm/year could eventually bring the lake from a dry–out situation to an overflow situation. Furthermore, the IPCC derived scenarios show a clear tendency of the lake to increase its volume and reach the overflow level in a relatively short time.

There are a number of engineering situations where fluid-saturated geological media can be subjected to thermal effects. These include the disposal of heat-emitting nuclear fuel wastes in saturated geological formations, extraction of energy resources such as oil and natural gas by steam injection and the recovery of geothermal energy by ground source heat exchangers. The objective of this thesis is to study the coupled thermal-hydrological-mechanical (T-H-M) response of fractured geological media by the computational implementation of mathematical models. From the generalization of Biot's classical theory of consolidation of a saturated porous elastic medium to include thermal effects, we first derived the equations governing coupled T-H-M processes in saturated geological media. In order to obtain numerical solutions for the governing equations, the finite element method was used. A finite element computer code, FRACON (FRActured media CONsolidation), was developed in order to simulate plane strain and axisymmetric problems. Eight-noded isoparametric elements were developed to represent the intact regions of the geological medium, while special joint elements were developed to simulate discrete joints. The intact regions of the geological medium was assumed to exhibit linear elasticbehaviour. The joints between intact regions were modelled by constitutive relationships which reproduced both linear elastic and nonlinear elasto-plastic responses. The elasto-plastic stress-strain relationship of the joint, was formulated by appeal to classical theories of interface plasticity. The elasto-plastic model for joint behaviour thus formulated is capable of reproducing many of the fundamental features of mechanical behaviour associated with naturally occuring joints, such as dilation under shear and strain softening due to surface asperity degradation. Furthermore, the thesis presents a physically-based hydraulic model of the joint that permits the inclusion of the effec
The development of the FRACON code followed an extensive procedure of code verification via analytical solutions and intercode comparison. A unique set of benchmark problems was proposed in order to perform code verification for coupled T-H-M.
The FRACON code was used to interpret certain laboratory and field experiments, including the following: (1) coupled T-H-M laboratory experiment on a block of cementitious material; (2) lab experiments on joint shear behaviour under constant normal stress and constant normal stiffness conditions; (3) coupled shear-flow laboratory experiment on a joint; (4) Field experiments of fluid injection in a horizontal fracture in a granitic rock mass.
Lastly, the FRACON code was used to simulate the coupled T-H-M response of a rock mass to radiogenic heat from nuclear fuel wastes buried in the rock formation. The coupled H-M response of this rock mass to a future glaciation scenario was also simulated. It was shown that the mechanical/hydraulic regimes of the rock mass could be significantly changed by the above two factors. The importance of the consideration of T-H-M processes in the overall scheme of safety assessment of sites targeted for nuclear fuel waste repositories is supported by the findings of this thesis.

The management of large scale strategic urban combined drainage systems is becoming increasingly dependent upon weather radar systems which can provide quantitative precipitation information to improve the overall efficiency of a system's operational performance. Thus, there has been an increasing requirement for a more detailed knowledge of the radar rainfall data accuracy and the development of a mathematical rainfall-runoff model that can be used to analyse and control a system in real-time. Within this context, several important factors including signal attenuation, temporal and spatial data resolutions and rainfall quantisation schemes that determine the accuracy of radar rainfall estimates were examined in this thesis. In order to facilitate real-time flow simulation and forecast, a Conceptually Parametrised Transfer Function (CPTF) model has been developed based on Dynamic Linear Reservoir theory. The model is structurally simple and operationally reliable. It can be easily identified and robustly updated following a pulse response-to-CPTF procedure in which Genetic Algorithms play a key role. Using the model, the accuracy of areal rainfall estimates obtained by the Hameldon Hill radar has been assessed, firstly by comparing the radar rainfall estimates with `ground truth', and then by comparing the simulated hydrographs with the actual flow observations. Finally, a case study was conducted using radar rainfall data to highlight the potential benefit of real-time control for the strategic urban drainage system in the Fylde Coast. The major achievements documented in this thesis are: 1) A rule for determination of an appropriate input data resolution for hydrological models; 2) A general probability density function for describing the sampled radar rainfall intensities; 3) An efficient quantising law (ß-Law) and an associated adaptive rainfall quantisation scheme; 4) Three general conceptual pulse-response functions developed based on Dynamic Linear Reservoir theory; 5) CPTF model; and 6) A case study on the potential benefit of real-time control in the Fylde urban drainage system.

This research applies, evaluates and compares approaches to hydrological modelling and stream flow forecasting within a GIS environment. Three different approaches to modelling stream flow were investigated, namely; TOPMODEL, a regression approach and a GIS-based model, HydroGrid. TOPMODEL is a parametrically simple, physically-distributed model that allows the topological modelling of catchment processes. Regression modelling is a statistical technique that derives an empirical equation based on the assumption that the values of a dependent variable will depend upon the values of the independent variables. HydroGrid is a purpose-built GIS-based model for catchment modelling using the functionality that GIS offers for modelling the spatial variations of catchment characteristics. All three approaches were evaluated using readily available data for a lowland catchment, in Staffordshire, U.K. Model validation used six years of data covering the period 1991-92 through to 1996-97 - with years running from March-February. Five performance indicators were used to assess the models enabling both for detailed evaluation of the models and comparisons to be drawn with other research. The performance of the three models tested showed great similarities, with all approaches tending to over-predict stream flow. Model performance was also evaluated using three different evapotranspiration models - the Penman formula, the Crowe-irrigation method and the sine curve method. All three models performed best during wet years or wetter seasons indicating a common weakness in the accurate modelling of low stream flows. Despite similarities in performance, clear benefits of hydrological modelling within a GIS framework are identified. Overall, the results show that although the methods used here can help in daily flow modelling, there is a major need to improve methods for catchment modelling with routine data sources. An important development could be to loose-couple hydrological models with a GIS to improve their ability to use available information but also, as shown in this work, to model catchment processes directly within a GIS.

This thesis identifies, quantifies and models water fluxes within the Dauges National Nature Reserve, an acidic valley mire in the French Massif Central. A range of techniques were used to investigate the nature and geometry of granite weathering formations and of peat deposits. Rainfall, reference evapotranspiration, stream discharge, stream stage, groundwater table depths and piezometric heads were monitored over a three-year period. The distributed, physics-based hydrological model MIKE SHE/MIKE 11 was used to model water flow within the mire and its catchment. It was shown that the mire is mostly fed by groundwater flowing within the densely fissured granite zone and upwelling through the peat deposits. Upwelling to the peat layer and seepage to overland flow were highest along the mire boundaries. However hydrological functioning differs from this general conceptual model in some locations due to the high variability of the peat hydraulic characteristics, the presence of highly permeable alluvial deposits or past human interference including drainage. The equivalent porous medium approach used to model groundwater flow within the fissured granite zone gave satisfactory results: the model was able to reproduce discharge at several locations within the high-relief catchment and groundwater table depth in most monitoring points. Sensitivity analyses showed that the specific yield and horizontal hydraulic conductivity of the fissured zone are the parameters to which simulated stream discharge and groundwater table depth, including in peat, are most sensitive. The model was forced with new vegetation parameters to assess the potential impacts of changes in catchment landuse on the mire hydrological conditions. Replacement of the broadleaf woodlands that currently cover most of the catchment with conifer plantations would lead to a substantial reduction in surface and groundwater inflows to the mire and to a substantial drop in summer groundwater table depths, particularly along the mire margins.

Aid In Action Porthcawl (a registered South Wales Charity Organisation) has been carrying out charity work in the town of Rubik in the Mirdita Region of North Albania for many years. Rubik lies within the Catchment of the River Fani which is remote, ungauged and characterised by frequent flooding, erosion and deforestation. Over the years these processes have had a huge environmental and socioeconomic impact on the residents of Rubik. Aid In Action was concerned about this situation and wished to provide a sustainable solution. Following discussions with staff at the University of Glamorgan, it was agreed that a sustainable solution was the development of an integrated hydrological decision support system for the whole River Fani Catchment. Hydrological models can be a valuable tool, providing a common platform for experts, decision-makers and stakeholders for the sustainable management of catchments, especially when used within the framework of a Geographic Information System (GIS). Such models and systems require quantitative data of good quality over appropriate spatial and temporal scales. For remote mountainous ungauged river catchments in developing countries the development of a catchment model and management system is often complicated due to limited availability of such data. Very often, any available data are difficult to obtain; they could, for example, be scattered among local authorities and are generally in the national language of the country concerned, thus adding the challenge of having records translated into the study language. Over the last few decades, advances in hydrological data capture (e.g. using remote sensing) and data management systems (e.g. GIS) have provided opportunities for overcoming some of the challenges of modelling ungauged catchments. However, the data captured is often from different sensors and sources and at different scales. This research project sought out to creatively use multi-source and multi-scale data to develop a GIS based hydrological model of the River Fani Catchment in the North of Albania to provide, a long term solution for the sustainable management of the Fani Catchment, thus improving the quality of life for the residents of Rubik and the rest of the Catchment. Data from various remote sensing sensors (e.g. Landsat, MODIS, ASTER) and other sources such as published maps, limited gauged flow and rainfall records, local library archives, digital datasets (e.g. CORINE and radar rainfall) and interviews with residents were used to develop the integrated GIS-based hydrological (using WMS hydrological modelling environment) and hydraulic (HEC-RAS) model of the Fani Catchment. The model was then used to not only map significant environmental change in the Catchment (e.g. deforestation using various vegetation indices), but also to assess flooding impact and to analyse various “What-if” scenarios of conservation strategies (e.g. deforestation, afforestation and provision of runoff attenuation systems). The results suggest that the changes in vegetation cover (apart from farming practices) are not considerably extensive in the Catchment between 1984 and 2000. It was observed that afforestation as a flooding mitigation measure did not play a decisive role in runoff reduction compared with attenuation measures. This study has demonstrated the effectiveness of remote sensing and GIS in generating quantitative information on land classification, change detection, soil erosion and general catchment management for remote and ungauged catchments in developing countries. This has been particularly so, owing to recent developments in sensor technologies and increasing available datasets from data providers and the global scientific community at little or no cost.

Evapotranspiration as a major component of the water balance has been identified as a key factor in hydrological modelling. Water management can be improved by means of increased use of reliable methods for estimating evapotranspiration. The limited availability of measured climate and discharge data sets, particularly in the developing world, restricts the reliability of hydrological models in these regions. Furthermore, rapid changes in hydrological systems with increasing development mean uncertainties in water resource estimation are growing. These changes are related to the modification of catchment hydrological processes with increasing human activity. Dealing with data uncertainty and quantifying the impacts of catchment activities are significant challenges that scientists in the field of hydrology face today. Uncertainties in hydrometeorological data are associated with poor observation networks that provide data at point scales which are not adequately representative of the inherent heterogeneity within catchment processes. Using uncertain data in model applications reduces the predictive power of hydrological models as well as the ability to validate the model outcomes. This study examines the potential of using remote sensing-based evapotranspiration data to reduce uncertainty in the climatic forcing data and constraining the output of a rainfall-runoff hydrological model. It is common to use fixed seasonally variable potential evapotranspiration (PET) instead of temporally varying PET data as inputs to standard rainfall-runoff models. Part of the reason is that there are relatively few stations available to measure a variety of meteorological input data needed to compute PET, as well as the apparent lack of sensitivity of rainfall-runoff models to different types of PET inputs. As hydrometeorological data become more readily available through the use of earth observation systems, it is important to determine whether rainfall-runoff models are sensitive to time-varying PET derived from these earth observations systems. Further potential includes the use of actual evapotranspiration (ETa) from this type of data to constrain model outputs and improve model realism. It is assumed that a better representation of evapotranspiration demands could improve the efficiency of models, and this study explores some of these issues. The study used evapotranspiration estimates (PET and ETa) from the MOD16 global product with one of the most widely used hydrological models in South Africa. The investigation included applying the Pitman model in a number of case study catchments located in different climatic regions of the country. The main objectives of the study included (i) the establishment of behavioural model parameter sets that generate acceptable hydrological response under both naturalised and present-day conditions, (ii) the use of time-varying PET estimates derived from MOD16 data to force the model, and (iii) the use of MOD16 ETa estimates to constrain model-simulated ETa. Before examining the use of different PET forcing data in the model, a two-step modelling approached was employed both a single-run and an uncertainty version of the Pitman model. During the first step (using a single-run version), available information on catchment physical properties and regionalised groundwater recharge together with model calibration principles were used to develop model functionality understanding and establish initial parameter sets. The outcomes from the first step were used to define uncertain parameter ranges for the use in the uncertainty version of the Pitman model (second step). Further, catchment water uses were quantified to ensure comparability with present-day flow conditions represented by the stream flow records. The effects of forcing the Pitman model with MOD16-based time-varying PET data inputs were evaluated using static and dynamic sensitivity analysis approaches. In the static approach, parameter sets calibrated using fixed seasonal distributions of PET data remain unchanged when forcing the model with other forms of PET, whereas in the dynamic method, the model is recalibrated with changing PET inputs. In both approaches, model sensitivity was assessed by comparing objective function statistics of reference flow simulations with those simulations incorporating changing PET data inputs. The use of the MOD16 ETa data to constrain model- simulated evapotranspiration losses was conducted by calibrating the parameters such that the simulated-ETa matched the evapotranspiration loss estimated from the MOD16 data. Despite issues around model equifinality and significant uncertainty within water use information, the Pitman model simulations were generally satisfactory and compared with observed stream flow data where available. The use of time-varying PET data does not improve the efficiency of the model when both static and dynamic sensitivity approaches are used. This was highly expected with the static approach where fixed model parameter sets do not account for the changes in evapotranspiration demands. However, with the dynamic approach, it was difficult to conclude why the model efficiency did not improve given the flexibility of the model to achieve appropriate parameter sets to different forms of PET. The study noted that the insensitivity of the model to changes in PET demands could be due to uncertainties in the model structure and MOD16 data. Attempts to constrain the model-simulated actual evapotranspiration with MOD16 ETa estimates were hampered by large errors in the MOD16 data and resulted in the non-closure of the catchment annual water balance, even when likely errors in the other components of the water balance were accounted for. There is still a great deal of work that needs to be done to reduce uncertainties associated with the use of earth observation data in hydrological modelling. This study has identified some of the specific gaps within the application of evapotranspiration data from earth observation information. While the MOD16 data applied with the Pitman model did not achieve improved simulations, the study has demonstrated the enormous potential of the data product in the future should the identified uncertainties be resolved. Lastly, the investigation highlighted some of the possible model structural uncertainties specifically associated with the simplified soil-moisture accounting routines within the model. It is possible that amending the model structure through investigating the dynamics of the relationship between soil moisture and evapotranspiration losses would assist in the improved utilisation of earth observation products related to the MOD16 ET data.

In order to effectively manage river basin systems, a full understanding of the effects of land use change on hydrological processes, as well as knowledge on spatial heterogeneity of surface runoff with associated catchment characteristics, is required. This thesis employed the SWAT2009 model and SUFI-2 tool to understand the hydrological response to land use change in the Daning River catchment, Three Gorges Reservoir area, China. Firstly, appropriate landscape representations for the SWAT-based hydrological modelling were examined. DEM spatial resolution, catchment delineation scale and HRU definition were identified so that the inputs uncertainty could be reduced to a minimal level. Secondly, a consistent underestimation of discharge using station-based climatic records disclosed there was insufficient precipitation due to the location of the rain gauge at relatively low altitude. Considering the orographic effects on precipitation, Daning hydrological models were well calibrated and validated with the sparse climate observations. The model prediction uncertainty was also quantified. Thirdly, using the calibrated hydrological models of the Daning River catchment, this study quantified the effects of land use change (1990 and 2004) on the hydrological processes in the whole basin and sub-catchment levels. In 1982-1993, the change of land use pattern from 1990 to 2004 resulted in an increase of surface runoff, whereas, in 1996-2007 reverting the land use from 2004 to 1990 caused a slight decrease of river flows. Increased forest cover decreased surface runoff at the sub-catchment level. A concurrent increase of agricultural land, which brought about more surface runoff, weakened the forest‘s ecological function of water retention at the catchment scale. This thesis highlights that the strategy of land use exploration for human use along with the afforestation is not always effective in ecological protection. With the changing land use in future, composition of forests and agricultural land is a significant element being considered.

This thesis explores several important hydrological modelling topics surrounding the use of continuous rainfall-runoff simulation for flood frequency estimation. A continuous simulation methodology suitable for flood frequency estimation is developed. The methodology features a rainfall-runoff model (TOPMODEL, e.g. Beven, 1997), a new profile-based stochastic rainfall model (developed in this thesis), and an uncertainty estimation procedure (Generalised Likelihood Uncertainty Estimation, or GLUE e.g. Beven and Binley, 1992). By explicitly accounting for a catchment's soil moisture conditions, allowing the direct simulation of long return period flood events (via the coupling of TOPMODEL with the stochastic rainfall model), and quantifying the uncertainty associated with the simulated flood estimates, this methodology is an attractive alternative to the more traditional statistical and event-based techniques available for flood frequency estimation. It is tested successfully using data obtained from five, gauged, UK catchments. In addition to exploring the possible consistency between flood peak and continuous flow rainfall-runoff model parameterisations, the methodology is used to examine the potential impacts of climatic change upon flood frequency. Two further issues are also addressed. These are: the choice of stochastic rainfall model (for use within continuous simulation studies), and the modification of a pulse-based stochastic rainfall model for enhanced extreme rainfall simulation.