Dissertations / Theses on the topic 'HYDRUS-1D'
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Nichols, William. "Modeling Performance of an Operational Urban Rain Garden Using HYDRUS-1D." Thesis, Villanova University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10811265.
Full textTools for predicting rain garden performance are limited, particularly for predicting seasonal performance. Changes in temperature cause changes in the viscosity of water, infiltration rates, and evapotranspiration rates. A variably-saturated soil model, HYDRUS-1D, was calibrated and validated using observed ponding depth and soil moisture data for the Philadelphia Zoo Rain Garden, owned and operated by the Philadelphia Water Department (PWD). Warm and cold seasons were simulated with typical meteorological data and temperature-adjusted saturated hydraulic conductivity values. Design-storm simulations confirmed that the rain garden is over-performing. Maximum capacity of the system was simulated by increasing the loading ratio until overtopping occurred or ponding remained longer than 24 hours. This study will demonstrate how modeling of an operational urban rain garden offers a realistic picture of performance and could be used as a tool for informing regulations and design.
Inforsato, Leonardo. "Determinação das propriedades hidráulicas do solo pelo método de evaporação monitorada por atenuação de radiação gama." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/64/64134/tde-12112018-141229/.
Full textMathematical models are commonly used in studies of water dynamics in unsaturated soil. The main equation to quantify water the dynamics is the differential Richards equation. Its analytical solution is impossible in almost all cases, requiring numerical methods, among which the Van Genuchten - Mualem water conductivity and water retention functions are frequently used to obtain the numerical solution. The objective of this work is to present a new method to obtain the Van Genuchten - Mualem parameters, using the inverse modeling of water content data measured periodically by gamma radiation attenuation in evaporating samples. Hydrus-1D software was used for the inverse modeling. The method was tested in samples with different textures, collected in 11 locations in the region of Piracicaba, state of São Paulo, Brazil. Of the sets of samples analyzed, only one presented an unsatisfactory result, concluding that the method is valid
Atmosudirdjo, Aryani. "Simulation of Leachate Generation from a Waste Rock Dump in Kiruna Using HYDRUS-1D." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-379225.
Full textPinho, Roque Emmanuel da Costa de. "Teores de água e solutos no solo: desempenho e sensibilidade do modelo Hydrus-1D." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/11/11131/tde-25022010-154643/.
Full textThe concern about the fate of chemical products and water, applied to the soil, has been motivating several researchers to develop and apply theoretical models, aiming to describe the physical processes involved in the transport of those products in soil profile. The present research had as objective the application of the model Hydrus- 1D for water and solute (nitrate and potassium) simulation profile, in laboratory conditions, using soil columns filled with two types of unsaturated soil (Oxisol (Haplustox) and Hapludox), as well to evaluate the acting and sensitivity of the model. The transport parameters were obtained for each solute by breakthrough curves (BTCs). The transport parameters obtained and the boundary conditions were inserted in the Hydrus-1D model to realize the simulations. The acting of the Hydrus-1D model was evaluated using the statistical indicators: maximum error, mean absolute error, normalized root mean-square error, coefficient of residual mass, determination coefficient, efficiency and Willmott concordance index. The model sensitivity was evaluated by the method proposed by McCuen and Snyder (1986) and applied to the parameters: input flow, soil saturated hydraulic conductivity, water content (saturation point), alpha and n (soil water retention curve parameters), distribution coefficient and dispersivity. The obtained results, experimentally, showed the nitrate displacement following the wetting front and, in relation to the potassium ion, a larger retention was observed at the superficial soil columns layers. Therefore, was possible to conclude that Hydrus-1D model was efficient for both water and potassium displacement simulations, for both studied soils and by the balance model for solute transport in soil, the Hydrus- 1D model was not efficient to simulate the nitrate displacement in both soils. The experimental procedures to estimate transport parameters, by the BTCs, were enough to describe the potassium movement in soil, generating input information necessary to the model simulation. To the simulation of the nitrate displacement, was possible to conclude that the model Hydrus-1D requests a more detailed experimental process, being necessary the estimate of a larger number of transport parameters. In relation to the sensitivity analysis of the Hydrus-1D model, when simulated the content of potassium and water at the soil columns, was observed that the model shows more sensitivity about to the parameters: water content (saturation point) and input flow. This parameters need to be estimated with more precision. There was a low sensitivity to the parameters soil saturated hydraulic conductivity and dispersivity for both studied soils.
Vogel, Mie. "Effects of Model Spin-Up on Simulated Recharge Using the Hydrus-1D Vadose Zone Model." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-385590.
Full textSantos, Rafaelly Suzanye da Silva. "Simulação da dinâmica do íon potássio pelo modelo HYDRUS-1D em condições de solo salino." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/11/11152/tde-06012015-110030/.
Full textThe increased demand for food due to population growth requires that agricultural practices become increasingly intensive and very technical, including the increased use of agricultural chemicals (fertilizers). If improperly applied without considering possible impacts on natural resources, agricultural chemicals may lead to soil and groundwater contamination through their leaching from the soil root zone. They may be responsible also for increased salinity in some soils of semiarid regions in northeastern Brazil. Since many transient physical and chemical processes affect their transport in the subsurface, mathematical models have become popular tools in soil and water engineering and management in order to understand the correlation between water dynamics and solute movement in soils. Thus, this research aimed at using the HYDRUS-1D software package to simulate water and potassium movement, under laboratory conditions, in unsaturated saline soil columns filled with two soil types: an Ultisol (S1) and an Oxisol (S2). Comparisons were made with experimental data while also a sensitivity analysis was carried out to evaluate the effect of various parameters on solute transport under saline conditions. For this purpose the following studies were performed: 1) Measurement of solute breakthrough curves (BTCs) to estimate the transport parameters of the potassium ion by applying potassium solutions of 1,000 ppm, 2,000 ppm and 3,000 ppm to both soil types, 2) Application of similar potassium solutions to columns containing the same saline unsaturated soils, 3) Simulation of water and potassium distributions for different saline soil materials using HYDRUS-1D, and 4) Performance evaluation and sensitivity analyses of the HYDRUS-1D numerical model. The performance evaluation was conducted using the following statistical indices: maximum error, mean absolute error, normalized root mean square error, coefficient of residual mass, coefficient of determination, efficiency and Willmott\'s concordance index. The sensitivity analyses considered standard deviations resulting from positive and negative changes (+ 10% + 20% + 30% + 40% + 50%) (-10%, -20%, -10%, -40%, -50%) in the values of the saturated volumetric soil moisture content, the saturated hydraulic conductivity, and the parameters n and ? of van Genuchten\'s (1980) model for the unsaturated soil hydraulic functions. Results indicate that the experimental procedures (BTCs) for estimating the transport parameters of potassium for saline soil conditions were sufficient to describe potassium ion transport in the soils by generating the required input information for the simulation models. Relative to HYDRUS-1D model, the displacement of potassium was found to follow closely the wetting front, with the model providing a very efficient means for simulating the movement of both water and potassium in the two soils during saline conditions. The sensitivity analysis showed that the model was relatively sensitive to negative variations of the input data, notably the saturated water content, the saturated hydraulic conductivity, and the n and ? soil hydraulic parameters.
Tyaquiçã, da Silva Santos Pedro. "Balanço hídrico em teto com cobertura vegetal no semiárido pernambucano." Universidade Federal de Pernambuco, 2011. https://repositorio.ufpe.br/handle/123456789/5886.
Full textFaculdade de Amparo à Ciência e Tecnologia do Estado de Pernambuco
Na atualidade, metade da população mundial reside nos grandes centros urbanos. Grande parcela desse crescimento tem ocorrido em países em desenvolvimento. No Brasil, já se verifica um contingente de cerca de 80% da população residindo nas áreas urbanas. Neste crescente cenário de urbanização, impactos ambientais e socioeconômicos decorrentes de eventos hidrológicos têm sido recorrentes, afetando grande parte da população. O aumento da impermeabilização reduz as taxas de infiltração, que por sua vez leva à diminuição das taxas de recarga para os aquíferos e à diminuição do escoamento de base. O escoamento superficial é intensificado, aumentando em velocidade e, a frequência e magnitude dos picos de cheia, levando ocasionalmente às enchentes. Nesse contexto, têm sido empregados os telhados verdes em várias partes do mundo principalmente com finalidades estéticas de valorização do espaço urbano e para melhoria do conforto ambiental. Essas áreas verdes podem servir também para detenção do escoamento superficial, minimizando as enchentes urbanas. A simulação da dinâmica da água no solo do telhado verde realizada no programa Hydrus 1-D, a partir das características do sistema do teto verde implantado e dados obtidos em campo, proporcionou a caracterização da dinâmica da água em seu perfil de solo, fornecendo subsídios quanto ao desempenho deste dispositivo no amortecimento do escoamento superficial oriundo dos telhados
Mallmann, Fábio Joel Kochem. "Modelagem na transferência de cobre e zinco em solos contaminados por dejetos líquidos de suínos." Universidade Federal de Santa Maria, 2013. http://repositorio.ufsm.br/handle/1/3345.
Full textSoils subjected to successive pig slurry (PS) amendments present zinc (Zn) and copper (Cu) increases, mostly on soil surface layer. The continuous application of PS causes accumulation of these heavy metals (HM) in soil, increasing risks for environmental contamination. Therefore, development of methods to estimate Zn and Cu accumulation in surface layer and their movement in soil is very important for the management planning of PS and of the agricultural soils amended with these residues. The main objective of this work was to model the vertical transport of Zn and Cu in profile of agricultural soils receiving successive application of PS at high, moderate and low doses, evaluating the effects of soil tillage and water absorption by roots on the movement of these HM. We also aimed to predict the long-term accumulation of HM in soil surface and their transport into groundwater, comparing estimated results with the threshold values established for agricultural soils and groundwater by the Conselho Nacional do Meio Ambiente (CONAMA). Two studies were performed on field experiments composed by different PS doses, the first located on an Alfisol in Santa Maria RS, and the second on an Oxisol in Campos Novos SC. Hydro-physical and chemical characteristics of these soils were measured and, accompanied by atmospheric and PS application data sets, were introduced into HYDRUS-1D for parameterization of the two-site model used. In the first study, simulations for next 100 years were performed under scenarios combining two PS doses and four time intervals between soil tillage of the arable layer. The solute transport model used on these simulations was already validated for this local soil in another study. In the second study, the validation of a solute transport model was carried out primarily, following the same approaches used for the Alfisol. Afterwards, root water uptake and root growth modules were introduced to the model. The future scenarios were simulated using applications of different PS doses during the next 50 years. The solute transport model previously validated for the Alfisol was also validated for the Oxisol, and the introduction of the root modules in HYDRUS-1D produced even better results. This increased the usefulness of the model for its use in simulations related to Zn and Cu transport on other contaminated soils. Future scenarios exhibit a great accumulation of these two HM in soil surface layer during the simulated times. Moreover, when soils are submitted to high PS annual doses, its Cu concentrations reached the maximum values established by CONAMA for agricultural soils in approximately 94 years on the Alfisol and in 29 years on the Oxisol. Reduction in PS doses and sporadic soil tillage are strategies that slow the increase of these HM concentrations in soil surface layer, decreasing so the environmental risks and making PS additions on agricultural soils viable for longer time.
Solos submetidos a sucessivas aplicações de dejeto líquido de suínos (DLS) apresentam incrementos nos seus teores de zinco (Zn) e cobre (Cu), principalmente na camada superficial. A continuidade dessa prática faz com que esses metais pesados (MP) se acumulem no solo, aumentando o potencial de contaminação do ambiente. Dessa forma, o desenvolvimento de métodos que estimem o acúmulo superficial e o movimento de Zn e Cu no solo é de extrema importância no planejamento do manejo dos DLS e dos solos agrícolas que recebem esses resíduos. O trabalho objetivou modelar o transporte vertical de Zn e Cu no perfil de solos agrícolas contaminados por aplicações sucessivas de altas, moderadas e baixas doses de DLS, avaliando o efeito do revolvimento do solo e da absorção de água pelas raízes no movimento desses MP, prevendo, no longo prazo, seus acúmulos na camada superficial do solo e suas transferências rumo ao lençol freático, confrontando os resultados estimados com os respectivos limites de concentração para solos agrícolas e águas subterrâneas estabelecidos pelo Conselho Nacional do Meio Ambiente (CONAMA). Foram realizados dois estudos em experimentos de campo com diferentes doses de DLS, o primeiro localizado sobre um Argissolo, em Santa Maria RS, e o segundo sobre um Latossolo, em Campos Novos SC. Diversas características físico-hídricas e químicas foram determinadas nesses solos para, juntamente com os dados atmosféricos e do histórico de aplicação de DLS nessas áreas, serem introduzidos no HYDRUS-1D para parametrização do modelo químico de dois sítios utilizado. No primeiro estudo foram realizadas simulações para os próximos 100 anos, considerando cenários combinando duas doses de DLS e quatro intervalos de tempo entre revolvimentos periódicos da camada arável do solo. O modelo de transporte de solutos utilizado nessas simulações já havia sido validado para o solo deste local em outro trabalho. No segundo estudo foi feita a validação de um modelo de transporte de solutos, seguindo as mesmas premissas do modelo utilizado no Argissolo. Posteriormente, módulos de absorção de água e crescimento de raízes foram incorporados ao modelo. Realizaram-se então simulações futuras de cenários considerando aplicações de diferentes doses de DLS durante os próximos 50 anos. O modelo de transporte de solutos validado previamente no Argissolo foi validado também no Latossolo, apresentando resultados ainda melhores quando os módulos de raízes foram introduzidos no HYDRUS-1D. Isso aumenta a abrangência desse modelo para simular o transporte de Zn e Cu em outros solos contaminados. Os cenários futuros mostram que ocorre grande acúmulo desses MP na camada superficial do solo durante os períodos simulados. Além disso, quando os solos são submetidos a altas doses anuais de DLS, as suas concentrações de Cu atingem os valores máximos estipulados pelo CONAMA, para solos agrícolas, em aproximadamente 94 anos no Argissolo e 29 anos no Latossolo. Reduzir as doses de DLS e revolver o solo esporadicamente são alternativas que retardam o aumento da concentração desses MP na camada superficial do solo, diminuindo o potencial de impacto ao ambiente e tornando a adição de DLS em áreas agrícolas viável por mais tempo.
Sun, Hongyan. "Characterizing Water and Nitrogen Dynamics in Urban/Suburban Landscapes." DigitalCommons@USU, 2011. https://digitalcommons.usu.edu/etd/1073.
Full textParajuli, Kshitij. "Advancing Methods to Quantify Actual Evapotranspiration in Stony Soil Ecosystems." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7242.
Full textZwirtes, Anderson Luiz. "Medição e simulação da temperatura e conteúdo de água em argissolo sob resíduos de aveia." Universidade Federal de Santa Maria, 2017. http://repositorio.ufsm.br/handle/1/13227.
Full textThis research was conducted with the objective of studying the dynamics of soil temperature and water content as a function of the different amounts of black oat residue (Avena sativa Schreb.) in the soil cover, through existing relationships with meteorological variables, as well as the simulation of these dynamics using Hydrus-1D. The experiment was carried out in an Argissolo Vermelho Distrófico arênico (Rhodic Paleudalf) in Santa Maria - RS. The treatments consisted of the use of 3, 6 and 9 Mg ha-1 of oat straw in soil cover and an uncovered soil treatment (0 Mg ha-1). Soil temperature and water content at different depths, in addition to meteorological conditions, were measured during the period from December 1, 2014 to December 6, 2015. The effect of straw on soil temperature was analyzed at different depths, correlating covered soil temperature with uncovered soil temperature. The equations used for estimating soil surface temperature were adjusted by the least square method, where the surface temperature is estimated as a function of air temperature and incident solar radiation, and its performance compared to the sinusoidal equation. The hydraulic and thermal parameters required for the simulation of soil temperature and water content were optimized by the reverse solution and validated on uncovered soils. The optimized parameters were used to simulate the temperature and water content in soils with different amounts of straw with two contour conditions for the soil surface temperature, one measure and the other estimated. The straw affected the soil temperature down to 50 cm deep. The uncovered soil temperature at which inversion of the straw effect occurred was 19.6 ° C at the surface and 15.8 ° C at 50 cm depth. The presence of straw keeps the soil warmer than the soil without straw at the beginning of the day, but prevents it from warming similar to the ground without straw for the rest of the day, causing in turn that, bare soil gets warmer during the day and cools more at night compared to the covered soil. This temperature was similar in all amounts of straw, but decreased in depth. The temperature of the soil surface can be estimated as a function of air temperature and solar radiation. In uncovered soil the proposed equation presents better performance compared to the sinusoidal equation. In covered soils the sinusoidal equation had better performance. The optimal hydraulic and thermal parameters of the soil improved the simulations of temperature and soil water content. The soil temperature with different amounts of oat straw can be simulated using Hydrus-1D, and the use of the contour condition with the measured surface temperature performed better than the estimated surface temperature.
Esta pesquisa foi conduzida com o objetivo de estudar a dinâmica da temperatura e do conteúdo de água do solo em função de diferentes quantidades de resíduos de aveia preta disposta em cobertura por meio das relações existente com variáveis meteorológicas, bem como a representação destes comportamentos por meio de simulação utilizando o Hydrus-1D. O experimento foi conduzido em um Argissolo Vermelho Distrófico arênico em Santa Maria - RS. Os tratamentos consistiram da utilização de três diferentes níveis de cobertura do solo (3, 6 e 9 Mg ha-1) com palha de aveia (Avena sativa) e um tratamento com solo descoberto (0 Mg ha-1). A temperatura do solo e o conteúdo volumétrico de água, em diferentes profundidades, além das condições meteorológicas, foram mensurados durante o período de 01/12/2014 a 06/12/2015. O efeito da cobertura do solo com resíduos vegetais na temperatura do solo foi analisado nas diferentes profundidades correlacionando a temperatura do solo com palha e a temperatura do solo descoberto. O método dos mínimos quadrados foi usado para gerar equações de estimativa da temperatura da superfície do solo em função da temperatura do ar e da radiação solar e o seu desempenho foi comparado com a equação senoidal. Os parâmetros hidráulicos e térmicos, necessários para a simulação da temperatura e do conteúdo de água do solo, com o Hydrus-1D, foram otimizados por meio da solução inversa e validados em solos descobertos. Os parâmetros otimizados foram usados para a simulação da temperatura e do conteúdo de água em solos com diferentes quantidades de palha com duas condições de contorno para a temperatura da superfície do solo, uma medida e outra estimada. A palha exerce influência sobre a temperatura do solo até 50 cm de profundidade. A temperatura do solo descoberto em que ocorre a inversão do efeito da palha foi de 19,6 °C na superfície e 15,8 °C a 50 cm de profundidade. A presença de cobertura de palha mantém o solo mais aquecido que o solo sem palha no início do dia, mas impede que ele se aqueça igual ao solo sem palha no restante do dia. Assim resultando em uma percepção de que a palha aquece e resfria o solo em relação à temperatura do solo desnudo. Essa temperatura foi semelhante em todas as quantidades de palha, porém decresceu em profundidade. A estimativa da temperatura da superfície do solo pode ser estimada em função da temperatura do ar e da radiação solar. Em solo descoberto as equações propostas tem melhor desempenho que a equação senoidal. Em solos cobertos a equação senoidal teve melhor desempenho. Os parâmetros hidráulicos e térmicos do solo otimizados melhoraram as simulações da temperatura e conteúdo de água do solo. A simulação da temperatura do solo com diferentes quantidades de cobertura vegetal pode ser simulada usando o Hydrus-1D, sendo que o uso da condição de contorno com a temperatura da superfície medido teve melhor desempenho que o utilizando a temperatura da superfície estimada.
Jiang, Shuang. "Bacterial leaching from dairy shed effluent applied to a fine sandy loam under flood and spray irrigations." Lincoln University, 2008. http://hdl.handle.net/10182/668.
Full textMeyer, Nathaniel Andrew. "Simulating the accumulation of calcite in soils using the soil hydraulic model HYDRUS-1D." Thesis, 2012. http://hdl.handle.net/2152/ETD-UT-2012-08-6255.
Full texttext
Li, Yi-Hsien, and 李奕賢. "Application of HYDRUS-1D Model to Estimate Parameters of Soil Water Characteristic Curve Parameters." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/09696158260471921317.
Full text國立中央大學
應用地質研究所
98
Infiltration test is an important technique to investigate the hydrologic properties in soils, while the unsaturated flow numerical models can be an efficient tool to understand flow mechanism when the physical properties and conditions of soils are changed. This study employs HYDRUS-1D model and self developed Levenberg-Marquardt algorithm to inversely estimate parameters in the van Genuchten formula. The developed LM model was tested based on the synthetically generated data from HYDRUS-1D model. Additionally, the initial guesses of soil parameters in LM model were systematically analyzed to obtain general insight into the laboratory and field scale applications. The tested model was then used to estimate soil parameters of laboratory sand box under different infiltration scenarios. During the infiltration tests, the suction or pressure and water content were measured with tensiometers TDR(Time Domain Reflectometry). Such measured data can thus be used in the LM model to estimate the soil parameters. The estimated parameters were compared with those based on trial and error approach. Field scale double-ring infiltration was tested on the river bank of Zhuoshui river near His-Luo. The saturated infiltration rate(fc), initial infiltration rate (f0), and infiltration parameter by using the in Horton formula were estimated by the developed LM model. The objective of the field scale test is to obtain the saturated infiltration rate(f0) to compare with the results of laboratory experiment. Estimate Van Genuchten parameters by combining the laboratory infiltration experiment of field soil sample and saturated infiltration parameters. The results of the study reveal that the developed LM model associated with HYDRUS-1D model can accurately estimate van Genuchten soil parameters. The results of model test shows that the lower initial guess values would lead to better estimations of residual water content (θr) and α values. The saturated hydraulic conductivity (Ks) is the most sensitive parameter while the initial guess n values are relatively insignificant. The LM inversion of tests show that LM model associated with HYDRUS-1D model can estimate accurately van Genuchten for laboratory scale tests soil parameters. The field scale multiple depth double-ring infiltration tests reveals that the saturated infiltration rates(f0) of Zhuoshui river near His-Luo have one order of magnitude difference for different depths such depth difference of hydraulic conductivity (Ks) (0.0014 and 0.00015 cm/s) were also shown in laboratory scale tests. Based on the soil sample from Zhuoshui river the sand box experiment data were then used in LM model to estimate soil parameters. This simulation results showed that the value of α is from 0.01688 to 0.09289(cm-1), the value of n from 2.528 to 5.886(-), the material of the soil can be classified as sand and silt.
Hsu, Kan-Sheng, and 許堪昇. "Soil Temperature and Volumetric Water Content Prediction in Greenhouse by Using Hydrus-1D, ICON and Random Forest Method." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/p6tjuv.
Full text國立臺灣大學
生物環境系統工程學研究所
107
Due to the impact of climate change and the rising frequency of extreme weather have caused the problem of food security and water resources. Precision agriculture in greenhouses is gradually becoming a trend because it is less affected by external environmental factors and easier to manage. In order to effectively improve the utilization of water resources and reduce wasting water, this study planted cherry tomatoes in the greenhouse and installed monitoring instruments to collect data. The soil temperature and volumetric water content during tomato growth can be predicted effectively by combining the weather forecast. The Hydrus-1D, random forest method and ICON were used to simulate the change of soil temperature and volumetric water content in the greenhouse. The results of the simulation show good performances among the three models. Further combined with weather forecast data, three models were applied to predict soil temperatures and volumetric moisture contents. Both of predicted soil temperature and volumetric water content by Hydrus-1D followed the trend of real measured data, but Hydrus-1D can’t predict the watering situation. The predicted performance of soil temperature by ICON was low. Nevertheless, both predictions by random forest method were better than others. This study simulated and predicted the soil temperatures and volumetric water contents by applying Hydrus-1D, random forest method and ICON to improve greenhouse management and increase water-use efficiency.
Adhikari, Bishwodeep. "The Contributions of Soil Moisture and Groundwater to Non-Rainfall Water Formation in the Namib Desert." Thesis, 2019. http://hdl.handle.net/1805/20533.
Full textNon-rainfall waters such as fog and dew are considered as important source of water in drylands, and the knowledge of possible sources of its formation is very important to make future predictions. Prior studies have suggested the presence of radiation fog in drylands; however, its formation mechanism still remains unclear. There have been earlier studies on the effects of fog on soil moisture dynamics and groundwater recharge. On the contrary, no research has yet been conducted to understand the contribution of soil moisture and groundwater to fog formation. This study, therefore, for the first time intends to examine such possibility in a fog-dominated dryland ecosystem, the Namib Desert. The study was conducted at three sites representing two different land forms (sand dunes and gravel plains) in the Namib Desert. This thesis is divided into two parts: the first part examines evidences of fog formation through water vapor movement using field observations, and the second part simulates water vapor transport using HYDRUS-1D model. In the first part of the study, soil moisture, soil temperature and air temperature data were analyzed, and the relationships between these variables were taken as one of the key indicators for the linkage between soil water and fog formation. The analysis showed that increase in soil moisture generally corresponds to similar increase in air or soil temperature near the soil surface, which implied that variation in soil moisture might be the result of water vapor movement (evaporated soil moisture or groundwater) from lower depths to the soil surface. In the second part of the study, surface fluxes of water vapor were simulated using the HYDRUS-1D model to explore whether the available surface flux was sufficient to support fog formation. The actual surface flux and cumulative evaporation obtained from the model showed positive surface fluxes of water vapor. Based on the field observations and the HYDRUS-1D model results, it can be concluded that water vapor from soil layers and groundwater is transported through the vadose zone to the surface and this water vapor likely contributes to the formation of non-rainfall waters in fog-dominated drylands, like the Namib Desert.