For analyzing the effect of climate change on the streamflow at a regional scale, six General Circulation Models (GCMs) were selected from among eighteen GCMs from the Coupled Model Intercomparison Project (CMIP5) for the Pajaro River Watershed in central California. The 1/8° latitude-longitude resolution bias-corrected and downscaled CMIP5 projections were utilized for an ensemble of GCMs under four Representative Concentration Pathways (RCP2.6, RCP4.5, RCP6.0 and RCP8.5). The twenty-first century is segregated into three time-periods (2016-2039, 2040-2069 and 2070-2099) for comparing the streamflow against changing precipitation and temperature according to the CMIP5 projections. The daily maximum and daily minimum temperature are projected to consistently rise through to the latter part of the century. Csiro-mk3-6 and canesm2 models project an increase of 3.1°C in annual average daily maximum temperature and 3.4°C in annual average daily minimum temperature respectively in 2070-2099 period under RCP8.5 scenarios. Future precipitation is projected to increase in January and February, which means the wet months in the Pajaro River Watershed are likely to get more rainfall. The dry months would continue to receive diminished precipitation throughout the century. The streamflow was increasing on future January, and sporadically, in February months but diminished during the dry months. The range of annual average streamflow for the future years stretched from 0.1 to 29.1 m3/s for the GCM ensemble, mostly close to the lower limit. The results suggest considering multiple climate change scenarios and evaluating alternative setups would provide a robust basis for hydrological assessment.

Made available in DSpace on 2018-08-01T22:35:55Z (GMT). No. of bitstreams: 1 tese_9507_TAMÍRES PARTÉLLI CORREIA2016.pdf: 3373249 bytes, checksum: 745d9e1d9d1057a74e6d90b15125440c (MD5) Previous issue date: 2016-02-29 / CORREIA, Tamíres Partélli. Aplicação do modelo SWAT para simulação de cenários de uso da terra na bacia hidrográfica do Rio Jucu. 2016. Dissertação (Mestrado em Ciências Florestais) Universidade Federal do Espírito Santo, Jerônimo Monteiro - ES. Orientador: Prof. Dr. Sidney Sara Zanetti. Coorientador: Prof. Dr. Roberto Avelino Cecílio. A bacia hidrográfica do rio Jucu, juntamente com a bacia do rio Santa Maria da Vitória, são responsáveis por 50% do abastecimento de água no estado do Espírito Santo, e pela produção de 11% da energia elétrica do estado, e abrigam remanescentes florestais importantes para a preservação da biodiversidade. Devido à importância dessa área para conservação e manutenção dos mananciais, faz-se necessário o uso de ferramentas que visam a otimização dos usos da terra e entendimento do comportamento da dinâmica da água na bacia hidrográfica. Entre as técnicas utilizadas para representar os processos hidrológicos, destaca-se a modelagem. Dentre os diversos modelos hidrológicos, ressalta-se o modelo SWAT (Soil and Water Assessement Tool), um modelo físico e semi-distribuído. O presente estudo teve como objetivo principal simular cenários do uso e ocupação da terra, utilizando o modelo SWAT, na bacia hidrográfica do rio Jucu, localizada no estado do Espírito Santo. Foram definidos 6 cenários para avaliar a vazão mínima, média e máxima, sendo eles: com 20% de área de floresta nativa na bacia (F20) (cenário 1); cenário 2: com 36% de área de floresta nativa na bacia (uso da terra atual) (F36); cenário 3: com 50% de área de floresta nativa na bacia (F50); cenário 4: com 100% de área de floresta nativa na bacia (F100); cenário 5: com 100% da área da bacia ocupada com cultivo de eucalipto (E100); cenário 6: com 100% da área da bacia ocupada com pastagens (P100). O modelo foi calibrado e validado para a escala diária e mensal, utilizando índices estatísticos: coeficiente de eficiência de Nash e Sutcliffe, coeficiente de eficiência de Nash e Sutcliffe modificado, coeficiente de determinação e o índice PBIAS, que indicaram o desempenho satisfatório nas fases calibração e validação do modelo. Todos os cenários comprovaram a sensibilidade do modelo às alterações de uso da terra na bacia. Para o estudo das vazões mínimas de referência (Q7,10 e Q90), que diz respeito a disponibilidade de água na bacia hidrográfica, os maiores valores foram encontrados para os cenários 4 (F100), 3 (F50), 5 (E100), 2 (F36), 1 (F20) e 6 (P100), respectivamente, em ordem decrescente. O estudo das vazões mínimas é de extrema importância para avaliar como as florestas são importantes para manter a água dentro do sistema, principalmente nos períodos secos. Já para as vazões máximas (vazões de enchentes), os maiores valores ocorreram nos cenários 6 (P100), 5 (E100), 1 (F20), 2 (F36), 3 (F50) e 4 (F100), respectivamente, também em ordem decrescente. Em relação ao cenário atual (F36), observou-se que houve aumento na vazão média nos cenários 6 (P100) e 1 (F20), e decréscimo da vazão média nos cenários 4 (F100), 3 (F50) e 5 (E100). O estudo permitiu mostrar a importância das florestas para manter uma maior regularidade dos cursos de água, associado com maiores vazões mínimas e menores vazões máximas em cenários com mais floresta, tendo ficado evidente que somente a avaliação da vazão média não é suficiente para análise do comportamento hídrico na bacia.

Dans des contextes semi-arides et fortement anthropisés la caractérisation et la quantification des transferts de polluants dans les eaux de surface et vers la mer est importante à appréhender pour aider à une meilleure gestion de la ressource en eau dans un contexte de changements environnementaux. Sur le Nord-africain notamment la difficulté d’obtenir des données en quantité et qualité suffisante est difficile. La présente étude s’intéresse aux mécanismes de transfert des nitrates et des sédiments à l’échelle du bassin versant de la Tafna (7200 km2) et des plus grands fleuves de l'Afrique du Nord par une approche couplant les mesures in situ et le modèle SWAT (Soil and Water Assessment Tool). La partie in situ a permis de quantifier la quantité de nitrates apportée par les différents exutoires des sous bassins de la Tafna. Elle a aussi mis en évidence la contribution du bassin versant à l’eutrophisation de la Méditerranée tout en mesurant les quantités de nitrates acheminées vers les eaux marines. Les résultats ont mis en évidence les facteurs qui influent sur les flux et les concentrations en nitrates et notamment l’occupation du sol et les barrages ont une grande influence sur les flux de nitrates dans la Tafna. Les stations d’étude ont été classées selon un gradient d’eutrophisation, les stations amont présentant de fortes concentrations en nitrates, elles s’opposent aux stations avals. Les résultats de simulation sur la période 2003 à 2011 ont montré qu’une grande partie de l'eau de surface de la Tafna provient du ruissellement de surface (59%) et du flux latéral (40%), alors que la contribution des eaux souterraines est insignifiante (1%). La Tafna transfère une quantité annuelle moyenne de 2942 t.an-1 de sédiment vers la mer entre 2003 et 2011. SWAT a montré aussi que les cinq barrages de la Tafna stockent une grande quantité de sédiments, plus de 27 000 t.an-1 (90% des sédiments transportés par la Tafna). Le modèle reproduit aussi le flux de nitrates dans les stations de mesure entre 2003 et 2011. La Tafna transporte une quantité moyenne annuelle de 37 à 86 tN.an-1 jusqu'à la Méditerranée. Sur la base de ces résultats, l’approche de modélisation a pemis d’effectuer un changement d’échelle vers les grands bassins du nord-africain. La simulation a montré que les barrages de la Tafna stockent une quantité importante de nitrates [80 à 486 tN.an- 1], qui représente en moyenne 62% de la quantité totale de nitrates transportée annuellement par le fleuve. L’application du modèle sur les plus grands fleuves d'Afrique du Nord, Moulouya (55 860 km2), Tafna (7 200 km2), Chélif (44 694 km2) Oued el Kbir-Rhumel (8824 km2) et Medjerda (23 213 km2) a permis de représenter les flux d'eau, de sédiments et de nitrate. Les fleuves de cette région transportent une quantité de sédiments de 706 .103tan-1 vers la Mer ou le fleuve Oued Kbir-Rhumel qui contribue à la plus grande quantité (55%).Le flux de nitrates transportés vers la mer est de 5330 tN.an-1, le fleuve Moulouya qui contribue à la plus grande quantité (32%). Les barrages de cette région stockent une grande quantité de sédiments (98%) et de nitrates (39%) transportés par les fleuves vers la Méditerranée.

Increasingly erratic flow in the upper reaches of the Mara River, has directed attention to land use change as the major cause of this problem. The semi-distributed hydrological model SWAT and Landsat imagery were utilized in order to 1) map existing land use practices, 2) determine the impacts of land use change on water flux; and 3) determine the impacts of climate change scenarios on the water flux of the upper Mara River. This study found that land use change scenarios resulted in more erratic discharge while climate change scenarios had a more predictable impact on the discharge and water balance components. The model results showed the flow was more sensitive to the rainfall changes than land use changes but land use changes reduce dry season flows which is a major problem in the basin. Deforestation increased the peak flows which translated to increased sediment loading in the Mara River.

A SWAT hydrological model is developed to evaluate the individual and combined impacts of urbanization and climate change on water quantity (discharge) and quality (N and P) of the watershed of Carp River in Ontario, Canada. Seven numerical experiments (scenarios) were developed to represent the different configurations of the watershed in terms of land use (either current or projected) and climate regime (current or future, observed or simulated). The reference period is 1990-2018, and the future period is 2021-2050. The 2017 land use was used to represent the reference period. The future land use is the projected 2050 land use obtained from the City of Ottawa. The future climate was obtained by downscaling the outputs of nine (9) Regional Climate Models (RCMs) under two Representative Concentration Pathways (RCPs): RCP4.5 and RCP 8.5. The developed scenarios are the following: • S0o (baseline scenario) corresponding to the current land use map and the observed climate regime on the reference period • S0m is similar to S0o except that RCM outputs are used instead of the observed climate on the reference period • S1 corresponds to the future land use and historical climate regime on the reference period. • S0M45/S0M85 corresponds to the current land use and the future climate regime under RCP4.5 (S0M45) and RCP8.5 (S0M85) • S1M45/S1M85 corresponds to the future land use map and future climate regime under the two RCPs. The changes or impacts on quantity and quality in each scenario were estimated by comparing the results with the baseline scenarios S0o/m (reference) at two levels: globally (at the main outlet) and locally (at the outlet of an upstream sub-watershed). For a consistency purpose, S0o is used when assessing land-use change scenario while S0m was the reference in climate change and combined effects scenario. This allowed the comparison to be consistent with the same climate data frame. The results showed that climate change is likely to be the most dominant factor affecting discharge and nitrogen, while urbanization will control the quantity of phosphorus. Unsurprisingly, the combined effect had a more significant impact on water quantity and quality. However, the impact is not additive, and the relationship is not linear. Compared with S0, the annual average discharge increased by 1.57%, 5.49%, 7.52%, 6.75%, and 9.34% in S1, S0M45, S0M85, S1M45, and S1M85, respectively. In comparison, the change for annual N load was estimated at -1.88%, 29.62%, 2.03%, 24.84%, and -1.20% respectively. Change in annual average P was respectively 26.49%, 1.07%, -4.49%, 23.81% and 19.15%. Local impact assessment indicates the impact in upstream sub-watersheds may differ from the main outlet's impact in terms of magnitude and direction of change. Therefore, only considering global change may lead to a wrong interpretation of the impacts over the watershed. It is, therefore, necessary to evaluate the impacts at the local level as well.

Pluvial flood is a natural hazard that severely threatens people’s property and safety. With the development of algorithms and computer technologies, numerical modeling has emerged as an effective tool for predicting the impacts of floods. Despite being one of the most costly types of floods in West Africa, pluvial flooding has not been studied as extensively as riverine flooding, probably because modeling runoff across urban areas remains a challenge. Recently, a module based on the SCS Curve Number Method is incorporated in the open-source software TELEAMC-2D, which provides a possibility to model the infiltration process dynamically. TELEMAC-2D is one of the first hydraulic models to consider hydrologic parameters. Although the update is expected to increase the suitability of TELAMC-2D in pluvial flood modeling, the infiltration routine has not yet been tested in a real situation in a semi-arid area. This study aims to investigate the capability of TELEMAC-2D in simulating the rainfall-runoff process during a pluvial flood event in a semi-arid urban area, Niamey city in west Africa. Due to the lack of calibration data, a hydrological model SWAT is used to evaluate the performance of TELEMAC-2D. Through the comparison between the runoffs generated by the two models, it is found that TELEMAC-2D has a similar trend with SWAT in runoff simulation. However, TELEMAC-2D significantly overestimates the runoff magnitude despite having the same SCS values as SWAT. The reason for the overestimation is TELEMAC-2D that does not properly consider evaporation. Two suggestions are made to improve pluvial floods simulations using TELEMAC-2D in semi-arid areas: 1) couple TELEMAC-2D with a hydrologic model, and use net rainfall generated by the hydrologic model as precipitation input; 2) provide functions in infiltration subroutine that calculate rainfall abstractions by other hydrologic phenomena in addition to the infiltration process.

La pollution par les nitrates des eaux de surface et des eaux souterraines a suscité une attention mondiale ces dernières années. La recharge des eaux souterraines via d'infiltration dans les zones cultivées est une source importante de la contamination des eaux de surfaces. Les plaines alluviales supportent une activité agricole intensive et subissent une pollution aux nitrates importante. Il a été démontré que les échanges entre les eaux de nappes et la rivière contribuent à la rétention et/ou transformation de l'azote dans le continuum eaux de surface-eaux souterrains. La compréhension et la quantification des processus d'atténuation des concentrations en nitrates se produisant à l'interface nappe-rivière permettraient d'améliorer la connaissance du cycle de l'azote à l'échelle du bassin versant. Les objectifs de cette thèse sont : 1) quantifier les volumes d'eau échangés entre la rivière et l'aquifère alluvial dans les zones de plaine alluviale à l'échelle du bassin versant et 2) quantifier les taux de dénitrification dans les nappes alluviales à l'échelle du bassin versant et évaluer leurs influences sur les flux de nitrates de la rivière. Un échantillonnage sur le terrain ainsi qu'un travail de modélisation ont été effectués pour atteindre ces objectifs. Les campagnes d'échantillonnages sur le terrain ont eu lieu d'avril 2013 à mars 2014 sur le site d'étude de Monbéqui dans la plaine alluviale de la Garonne. Le modèle Soil and Water Assessment Tool (SWAT) qui est largement utilisé à travers le monde a été choisi pour simuler les processus hydrologiques et le cycle de l'azote. Cependant, la simulation des échanges nappe-rivière qui se produisent dans la plaine alluviale n'est pas prise en compte dans la version originale de SWAT. Premièrement, l'équation de Darcy a été introduite pour simuler les échanges nappe-rivière à partir de la structure Landscape Unit (LU). L'influence des crues débordantes sur ces échanges a également été ajoutée dans le modèle. Le modèle modifié, SWAT-LUD, a d'abord été appliqué à un méandre de la plaine alluviale de la Garonne- Monbéqui (25 km²). Ensuite, un module supplémentaire représentant les processus de dénitrification dans les aquifères peu profonds des nappes alluviales a été développé et ajouté au modèle SWAT-LUD. Les flux de nitrates ainsi que les taux de dénitrification de l'aquifère alluvial de Monbéqui ont alors été quantifiés. Dans un deuxième temps, le modèle SWAT-LUD a été appliqué à l'échelle de la plaine alluviale de la Garonne dans son cours moyen (environ 4600 km²) et l'influence de la dénitrification de l'aquifère alluvial sur les flux de nitrates de la rivière a été quantifiée. Finalement, le modèle a été appliqué sur l'ensemble du bassin versant de la Garonne (environ 51 500 km²) et l'influence des échanges nappes-rivières sur le cycle hydrologique du bassin versant a été évaluée. Les résultats ont montré que le modèle SWAT-LUD pouvait représenter de façon réaliste les échanges nappe-rivière ainsi que les taux de dénitrification dans les aquifères alluviaux à différentes échelles. Les flux échangés vont majoritairement de l'aquifère vers la rivière et contribuent pour 65% du volume total échangé. À l'échelle du bassin versant de la Garonne, le volume annuel échangé entre la nappe et la rivière représente environ 5% du débit annuel de la Garonne. A l'échelle du méandre, le taux annuel de dénitrification dans la zone riparienne a été estimé à environ 130 N-NO3-.ha-1.an-1. Près de 40% des nitrates arrivant dans cette zone ont été dégradés via les processus de dénitrification. Dans le cours moyen de la Garonne, les taux de dénitrification annuels dans ces mêmes zones varient entre 55 et 120 kg N-NO3-. ha-1. an-1. / Nitrate pollution in surface water and groundwater systems has attracted worldwide attention in recent decades. Recharged groundwater infiltrating through cultivated fields is an important source of the nitrate contamination of surface water. As alluvial plains support intensive agricultural activities, they often suffer from groundwater nitrate pollution. The exchanges between surface water and groundwater (SW-GW) were proved contributing to nitrate retention and/or transformation in the land-surface water continuum. The understanding and quantifying of nitrate attenuation processes occurring at the surface-groundwater interface would enhance understanding of nitrogen cycling at the catchment scale. The objectives of this thesis were: 1) quantifying the exchanged SW-GW volume in the floodplain area at the catchment scale and 2) quantifying the shallow aquifer denitrification rate in the floodplain area at the catchment scale and evaluating its influence on the nitrate flux in the river. Field sampling and modelling study were conducted to achieve these objectives. Monthly field work campaigns were carried out from April 2013 to March 2014 at the Monbéqui site in the Garonne river floodplain. The Soil and Water Assessment Tool (SWAT) which has been successfully applied all over the world was chosen to simulate the hydrologic processes and nitrogen cycle. However, the simulation of the water exchange between river and groundwater occurring in the floodplain area was not simulated in the original SWAT model. Firstly, the Darcy's equation was implemented to simulate SW-GW exchanges based on the Landscape Unit (LU) structure in the floodplain area. The influence of flooding on the water exchange was also introduced to the model. The modified model was called SWAT-LUD and was applied to a meander of Garonne floodplain - Monbéqui (around 25 km2). Then, another module representing the denitrification processes in the floodplain shallow aquifer was developed and added to the SWAT-LUD model. The nitrate flux and shallow aquifer denitrification rates in Monbéqui was then quantified. Afterwards, the SWAT-LUD model was applied to the middle floodplain section of the Garonne River (around 4 600 km2) and the influence of shallow aquifer denitrification on the nitrate flux in the river was quantified. Lastly, the model was applied to the entire Garonne catchment (around 51 500 km2) and the hydrologic influence of SW-GW exchanges was evaluated. The results showed that the SWAT-LUD model could satisfactorily represent the SW-GW exchanges and shallow aquifer denitrification rate at different spatial scales. The main water flow direction is from the shallow aquifer to the river, with water flowing in this direction accounted for around 65% of the total exchanged water volume. In the Garonne catchment, the annual total exchanged water volume represented around 5% of the total discharge volume of the Garonne river. For the Monbéqui site, the simulated annual denitrification rate in the riparian zone was around 130 kg N-NO3-ha-1y-1. Around 40% of the nitrate input in this zone was degraded through denitrification. In the middle floodplain section, the annual denitrification rate in the near bank zone ranges from 55 to 120 kg N-NO3-ha-1y-1.

No description available.

To date only a limited number of studies have been done at the field level to observe the effects of agricultural management practices on carbon sequestration, water quality, and bioenergy crop yield in Mississippi. Therefore, the goals of this study were to monitor soil organic carbon (SOC) levels at the field scale and perform a comprehensive analysis of the potential environmental impacts at the watershed scale using the Soil and Water Assessment Tool (SWAT) in two watersheds located in Mississippi. It was found that SOC levels generally are affected by depth, land use, and time. The SWAT models showed good performance overall and predicted that perennial grass production in the Town Creek watershed would render the most feedstock with the least environmental impact. The results of this study were consistent with the available literature, but a longer study period is recommended.

As the need for climatic data is increasing in times of climate change and water scarcity, remote sensing (RS) and hydrological modelling are ways to battle these problems, especially in data scarce areas. The actual evapotranspiration (ETa) is one of the key parameters when assessing the water balance and a good estimate of this parameter is thus of great importance. In this study a hydrologicalmodel was created with the Soil and Water Assessment Tool (SWAT) over the Malwathu Oya river basin, Sri Lanka, and the SWAT ETa estimates were compared to RS derived ETa from FAO’s open access database WaPOR. A sensitivity analysis and a calibration with observed streamflow data of the SWAT model was conducted with the SUFI-2 algorithm in SWAT-CUP. The calibration was satisfactory and showed the following values for the performance parameters: R2 = 0.72, Nash-Sutcliffe Efficiency, NSE = 0.69, and Percent of Bias, PBIAS = -10.4. The most sensitive parameters were CN2 (runoff curve number for moisture condition II), SOL_AWC (soil available water capacity), and ESCO (soil evaporation compensation factor). The water balance partitioning from the calibrated SWAT model showed a ratio of 0.68 between ETa and precipitation as an annual average between 2012–2020. In the comparison between SWAT ETa and WaPOR ETa the SWAT ETa showed a clear underestimation, particularly during the drier Yala growing season (May – August). However, the SWAT land use classes representing the cultivated rice fields agreed well with WaPOR while the forest and range grasses were underpredicted. To increase the performance of SWAT in estimating ETa the following was recommended: improvement of the simulation of the shallow aquifers, more accurate forest parameters, deactivation of the default dormancy period in SWAT, calibration with ETa instead of streamflow, and a higher resolution soil map together with more soil measurements. / Eftersom behovet av klimatdata ökar i tider av klimatförändringar och vattenbrist är fjärranalys (RS) och hydrologisk modellering exempel på metoder för att lösa dessa problem, särskilt i områden med brist på data. Den faktiska evapotranspirationen (ETa) är en nyckelparameter vid bedömning av vattenbalansen och en bra uppskattning av denna parameter är därför av stor betydelse. I denna studie skapades en hydrologisk modell med Soil and Water Assessment Tool (SWAT) över avrinningsområdet Malwathu Oya i Sri Lanka, och SWAT ETa -uppskattningarna jämfördes med RS-beräknad ETa från FAO:s öppna databas WaPOR. En känslighetsanalys och en kalibrering med observerade flödesdata av SWAT-modellen utfördes med SUFI-2-algoritmen i SWAT-CUP. Kalibreringen var tillfredsställande och visade följande värden för prestandaparametrarna: R2 = 0,72, Nash-Sutcliffe-Efficiency, NSE = 0,69 och Percent of Bias, PBIAS = -10,4. De mest känsliga parametrarna var CN2 (avrinningskurvtal för fukttillstånd II), SOL_AWC (jordens tillgängliga vattenkapacitet) och ESCO (kompensationsfaktor för markavdunstning). Vattenbalansfördelningen från den kalibrerade SWAT-modellen visade ett förhållande på 0,68 mellan ETa och nederbörden som ett årligt medelvärde mellan 2012–2020. I jämförelsen mellan SWAT ETa och WaPOR ETa visade SWAT ETa en tydlig underskattning, särskilt under den torrare Yala-växtsäsongen (maj – augusti). Däremot överensstämde SWAT-markanvändningsklasserna som representerade de odlade risfälten väl med WaPOR medan skog och gräsfälten var underskattade. För att öka prestandan för SWAT vid uppskattning av ETa rekommenderades följande: förbättring av simuleringen av de grunda akvifärerna, förbättrade skogsparametrar, inaktivering av den automatiska växtviloperioden i SWAT, kalibrering med ETa i stället för flöde och en jordartskarta med högre upplösning samt fler jordprover.