In a populated region with very high potential evapotranspiration, where the rainwater falls only during the winter and mostly in the mountains, the need for sustainable water management and fair distribution is crucial. In the West Bank, Palestine, the main potable water source is a karst mountain aquifer system. Precipitation occurs usually in the form of rainfall in the mountainous regions during winter period and recharges the groundwater systems. The water either reaches the surface as spring water, or is extracted through pumped wells. But the scarcity of drinking water in Palestine is not due to lack of water resources or technical knowledge of water extraction but a direct consequence of Israeli policies, water management, breached water rights and the occupation of Palestinian territories. Because of such restrictions, ground water is not an option to provide more freshwater, instead it is suggested to collect rainwater runoff in reservoirs. In 2011, the first surface water dam was built in Palestine in Al Auja, just north of Ariha. It was built as an experimental project for future dams and is therefore a small earth fill dam which will be expanded to collect water also from an adjacent watershed, much larger than the current one. The purpose of this study is to determine how much bigger the reservoir needs to be to safely store the inflowing rainwater runoff in the future. This was achieved through hydrological modelling using the HEC-HMS software which is a physical based model. The data used in this study were: 25 m DEM, land use data, soil data (both from remote sense and field visit), river network map, precipitation data, location of the gauges and geological formations. Field visits and soil tests were also great contributions of insights and knowledge crucial for the project. Hourly time-series data for precipitation for the winters 2011-2012 and 2012-2013 and monthly evapotranspiration for 2010-2011 were used as input to the model. Water level data in Al Uja reservoir with 20 minutes intervals were used to evaluate the simulations. Simulations were first optimized for the current scenario to find sets of parameters that match the changes in water level in the dam reservoir. This was done both for single rainfall events as well as for the whole seasons. The parameters creating the most matching results were used in additional simulations with the adjacent watershed included. The difference in results between the simulations with the current watershed and the expanded one was used to answer how much more water the reservoir would have received during 2011-2012 and 2012-2013 if the larger watershed were included. The model results reveal that the reservoir should have been able to hold about three times as much water as today. Installation of an inflow meter is suggested for the future along with an evaluation of local climate change in precipitation and evapotranspiration.

Climate change and socio-economic development are greatly affecting the quality of freshwater, especially the excessive accumulation of nutrients (N and P), which eventually leads to the occurrence of eutrophication. Lake Vomb is one of the main sources of drinking water in southern Sweden and the nutrient load from the catchment makes it a eutrophic lake with recurring algal blooms. This project developed a hydrological model by Soil and Water Assessment Tool (SWAT) to model the impact of climate and socio-economic changes on nutrient dynamics on Lake Vomb. Two combinations of future scenarios were selected as combinations of Representative Concentration Pathways (RCP) and Shared Socioeconomic Pathways (SSP): 1) SSP1/RCP4.5 and 2) SSP5/RCP8.5. For the calibration and validation period, satisfactory results were obtained for monthly flow (R2 and NSE were 0.92 and 0.82, respectively) and yearly nutrient load simulation obtained overall convincing results (R2, NSE and PBIAS were 0.67, 0, 17% for total nitrogen (TN) and 0.78, -0.11, -1% for total phosphorus (TP) at the main inflow and R2, NSE and PBIAS were 0.46, 0.27, 15% for TN and 0.62, -0.01, -0.06% for TP at the second inflow). Simulation results of increased future flow scenarios showed higher peaks under the RCP8.5 scenario than under RCP4.5. Also, there was an increasing trend that flow will continuously rise during the simulation period. Results from future nutrient load simulation showed that the TN load was below the baseline in most scenarios and the TP load was all above the baseline. Besides, nutrient loading is more sensitive to the combination of SSPs and RCPs and got the highest loads under RCP4.5/SSP1. The challenge of reducing nutrient load increases over time, especially for P because the simulated load was higher for 2090-2100 than the load for 2040-2050. This project has limitations such as uncertain agriculture activities input and nutrient observations. This project provides projections of flows and nutrient loads into Lake Vomb for a combination of possible future scenarios and more different scenarios such as different RCPs and different designed SSPs deserve to be studied in the future.

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

Long-term human-environmental interactions in naturally fragile drylands are a focus of geomorphological and geoarchaeological research. Furthermore, many dryland societies were also affected by seismic activity. The semi-arid Shiraki Plain in the tectonically active southeastern Caucasus is currently covered by steppe and largely devoid of settlements. However, numerous Late Bronze to Early Iron Age city-type settlements suggest early state formation between ca. 3.2-2.5 ka that abruptly ended after that time. A paleolake was postulated for the lowest plain, and nearby pollen records suggest forest clearcutting of the upper altitudes under a more humid climate during the Late Bronze/Early Iron Ages. Furthermore, also an impact of earthquakes on regional Early Iron Age settlements was suggested. However, regional paleoenvironmental changes and paleoseismicity were not systematically studied so far. We combined geomorphological, sedimentological, chronological and paleoecological data with hydrological modelling to reconstruct regional Holocene paleoenvironmental changes, to identify natural and human causes and to study possible seismic events during the Late Bronze/Early Iron Ages. Our results show a balanced to negative Early to Mid-Holocene water balance probably caused by forested upper slopes. Hence, no lake but a pellic Vertisol developed in the lowest plain. Following, Late Bronze/Early Iron Age forest clear-cutting caused lake formation and the deposition of lacustrine sediments derived from soil erosion. Subsequently, regional aridification caused slow lake desiccation. Remains of freshwater fishes indicate that the lake potentially offered valuable ecosystem services for regional prehistoric societies even during the desiccation period. Finally, colluvial coverage of the lake sediments during the last centuries could have been linked with hydrological extremes during the Little Ice Age. Our study demonstrates that the Holocene hydrological balance of the Shiraki Plain was and is situated near a major hydrological threshold, making the landscape very sensitive to small-scale human or natural influences with severe consequences for local societies. Furthermore, seismites in the studied sediments do not indicate an influence of earthquakes on the main and late phases of Late Bronze/Early Iron Age settlement. Altogether, our study underlines the high value of multi-disciplinary approaches to investigate human-environmental interactions and paleoseismicity in drylands on millennial to centennial time scales.

Can one society’s flood risk perception and management strategy impact the neighbouring society? This study applies a socio-hydrological model to four ideal types of society living along the same river. These societies have various rationalities and risk perceptions: risk-controlling, risk-monitoring, risk- neglecting and risk-downplaying. Combined with a hydraulic model of the river, this study explores the human-flood interactions and how the four societies can influence each other. The results show that the society that adopts soft-measures experiences the lowest flood loss; the society that neglects flood risks suffers from much higher flood losses. Dynamics, including the levee effect and adaptation effect, can also be observed. The society that builds levees to alter the hydrological regime causes the flood stage to be higher than it would have been without levees, indirectly increasing flood loss for the neighbouring societies. A more sustainable flood risk management strategy calls for broader considerations than the conventional method. / Skulle ett samhälles uppfattning om översvämningsrisk och förvaltningsstrategi påverka det närliggande samhället? Denna studie tillämpar en sociohydrologisk modell på fyra idealtyper av samhälle som lever längs samma flod. Dessa samhällen har olika rationaliteter och riskuppfattningar: riskkontroll, riskövervakning, riskförsummelse och risknedsättande. I kombination med en hydraulisk modell av floden, utforskar denna studie interaktionen mellan människa och översvämning och hur de fyra samhällena kan påverka varandra. Resultaten visar att det samhälle som vidtar mjuka åtgärder upplever lägst översvämningsförlust; det samhälle som försummar översvämningsrisker lider av mycket högre översvämningsförluster. Dynamik, inklusive valleffekten och anpassningseffekten, kan också observeras. Det samhälle som bygger vallar för att förändra den hydrologiska regimen gör att översvämningsstadiet blir högre än det skulle ha varit utan vallar, vilket indirekt ökar översvämningsförlusterna för de närliggande samhällena. En mer hållbar strategi för hantering av översvämningsrisk kräver bredare överväganden än den konventionella metoden.

Warming climate will affect communities across Canada. Many of these communities do not have the adaptive capacity to deal with climate change related challenges. Indigenous communities are believed to be disproportionally affected by climate change because of the lack of adequate infrastructure, and historical and political obstacles that limit their overall adaptive capacity. Therefore, climate change data and information are required to understand the full extent to which these communities are exposed to climate risks. Many past studies in the literature have outlined the effects of climate change at large spatial scales. While these studies are important for understanding the broad effects of climate change, they are not useful for community or local adaptation planning. Ultimately, climate change impacts will be felt at a local level. Hence, high resolution climate change impact studies are urgently needed to capture the realities of these effects in greater detail and to provide relevant data and information at local and community levels, in particular for marginalized and Indigenous communities. Using observed meteorological and hydrologic data, high-resolution downscaled future climate simulations, and a process-based hydrologic model, this thesis explored the physical impacts of climate change on the Six Nations of the Grand River (Six Nations) reserve, which is the largest (by population) Indigenous community in Canada and the seventh largest in the United States and Canada. Changing climate conditions and extreme climate trends in the Six Nations reserve were explored using the widely used ETCCDI (Expert Team on Climate Change Detection and Indices) extreme climate indices. Results indicated a warming and wetting trend in Six Nations, with the temperature rising by 3°C to 6°C by the end of the century and changes in seasonal precipitation. Extreme high temperature and precipitation indices will increase, causing potential human health impacts and increased flooding hazards for the community. A warming climate directly impacts the hydrological cycle and patterns. Analysis conducted using the Coupled Groundwater and Surface-Water Flow Model (GSFLOW) found that the McKenzie Creek - an important water provider for Six Nations - is sensitive to climate change due to its reliance on precipitation. Furthermore, study results showed that winter precipitation and streamflow are projected to increase, and snowpack water content is expected to decrease. These changes in streamflow will cause earlier winter-spring flooding events. Furthermore, agricultural production may be affected by reduced spring soil moisture recharge. Additionally, GSFLOW projected little to no change in late spring and summer streamflow which resulted in low water availability (Ptot-ET) during the growing season. Water availability was further examined by assessing future Blue Water (BW) and Green Water (GW) scarcity in the McKenzie Creek watershed. The water footprint method was used to calculate BW and GW scarcity. Study results showed that under current levels of water usage, BW scarcity would be “low” in the future. However, BW scarcity would increase to “significant” levels in the future, if water users started to withdraw more water for consumption, assuming maximum water withdrawal allocation (i.e., 0.47 m3s-1). This level of BW scarcity has the potential to cause ecological degradation and exacerbate water quality issues in the McKenzie Creek watershed. GW scarcity showed a steadily increasing trend throughout the 21st century due to climate warming. Spatial analysis showed that the western portion of the McKenzie Creek watershed may experience slightly higher levels of GW water scarcity in the future because of the lower water holding capacity of the soil. This may cause water users to withdraw more BW resources in western upstream areas, thereby decreasing BW available for downstream communities, including the Six Nations. Such disparity in water use among Indigenous and non-Indigenous communities may affect community relationships and social cohesion in the area. This thesis provides decision makers in Six Nations and more broadly in the McKenzie Creek watershed area with relevant climate change impact data and information that can be used in future climate change adaptation planning, disaster risk mitigation, and water resources management. Moreover, the results highlight the need for a comprehensive climate change vulnerability assessment of the Six Nations. / Thesis / Doctor of Philosophy (PhD)

[ES] La cuantificación de la incertidumbre predictiva es de vital importancia para producir predicciones hidrológicas confiables que soporten y apoyen la toma de decisiones en el marco de la gestión de los recursos hídricos. Los post-procesadores hidrológicos son herramientas adecuadas para estimar la incertidumbre predictiva de las predicciones hidrológicas (salidas del modelo hidrológico). El objetivo general de esta tesis es mejorar los métodos de post-procesamiento hidrológico para estimar la incertidumbre predictiva de caudales mensuales. Esta tesis pretende resolver dos problemas del post-procesamiento hidrológico: i) la heterocedasticidad y ii) la función de verosimilitud intratable. Los objetivos específicos de esta tesis son tres. Primero y relacionado con la heterocedasticidad, se propone y evalúa un nuevo método de post-procesamiento llamado GMM post-processor que consiste en la combinación del esquema de modelado de probabilidad Bayesiana conjunta y la mezcla de Gaussianas múltiples. Además, se comparó el desempeño del post-procesador propuesto con otros métodos tradicionales y bien aceptados en caudales mensuales a través de las doce cuencas hidrográficas del proyecto MOPEX. A partir de este objetivo (capitulo 2), encontramos que GMM post-processor es el mejor para estimar la incertidumbre predictiva de caudales mensuales, especialmente en cuencas de clima seco. Segundo, se propone un método para cuantificar la incertidumbre predictiva en el contexto de post-procesamiento hidrológico cuando sea difícil calcular la función de verosimilitud (función de verosimilitud intratable). Algunas veces en modelamiento hidrológico es difícil calcular la función de verosimilitud, por ejemplo, cuando se trabaja con modelos complejos o en escenarios de escasa información como en cuencas no aforadas. Por lo tanto, se propone el ABC post-processor que intercambia la estimación de la función de verosimilitud por el uso de resúmenes estadísticos y datos simulados. De este objetivo específico (capitulo 3), se demuestra que la distribución predictiva estimada por un método exacto (MCMC post-processor) o por un método aproximado (ABC post-processor) es similar. Este resultado es importante porque trabajar con escasa información es una característica común en los estudios hidrológicos. Finalmente, se aplica el ABC post-processor para estimar la incertidumbre de los estadísticos de los caudales obtenidos desde las proyecciones de cambio climático, como un caso particular de un problema de función de verosimilitud intratable. De este objetivo específico (capitulo 4), encontramos que el ABC post-processor ofrece proyecciones de cambio climático más confiables que los 14 modelos climáticos (sin post-procesamiento). De igual forma, ABC post-processor produce bandas de incertidumbre más realista para los estadísticos de los caudales que el método clásico de múltiples conjuntos (ensamble). / [CA] La quantificació de la incertesa predictiva és de vital importància per a produir prediccions hidrològiques confiables que suporten i recolzen la presa de decisions en el marc de la gestió dels recursos hídrics. Els post-processadors hidrològics són eines adequades per a estimar la incertesa predictiva de les prediccions hidrològiques (eixides del model hidrològic). L'objectiu general d'aquesta tesi és millorar els mètodes de post-processament hidrològic per a estimar la incertesa predictiva de cabals mensuals. Els objectius específics d'aquesta tesi són tres. Primer, es proposa i avalua un nou mètode de post-processament anomenat GMM post-processor que consisteix en la combinació de l'esquema de modelatge de probabilitat Bayesiana conjunta i la barreja de Gaussianes múltiples. A més, es compara l'acompliment del post-processador proposat amb altres mètodes tradicionals i ben acceptats en cabals mensuals a través de les dotze conques hidrogràfiques del projecte MOPEX. A partir d'aquest objectiu (capítol 2), trobem que GMM post-processor és el millor per a estimar la incertesa predictiva de cabals mensuals, especialment en conques de clima sec. En segon lloc, es proposa un mètode per a quantificar la incertesa predictiva en el context de post-processament hidrològic quan siga difícil calcular la funció de versemblança (funció de versemblança intractable). Algunes vegades en modelació hidrològica és difícil calcular la funció de versemblança, per exemple, quan es treballa amb models complexos o amb escenaris d'escassa informació com a conques no aforades. Per tant, es proposa l'ABC post-processor que intercanvia l'estimació de la funció de versemblança per l'ús de resums estadístics i dades simulades. D'aquest objectiu específic (capítol 3), es demostra que la distribució predictiva estimada per un mètode exacte (MCMC post-processor) o per un mètode aproximat (ABC post-processor) és similar. Aquest resultat és important perquè treballar amb escassa informació és una característica comuna als estudis hidrològics. Finalment, s'aplica l'ABC post-processor per a estimar la incertesa dels estadístics dels cabals obtinguts des de les projeccions de canvi climàtic. D'aquest objectiu específic (capítol 4), trobem que l'ABC post-processor ofereix projeccions de canvi climàtic més confiables que els 14 models climàtics (sense post-processament). D'igual forma, ABC post-processor produeix bandes d'incertesa més realistes per als estadístics dels cabals que el mètode clàssic d'assemble. / [EN] The predictive uncertainty quantification in monthly streamflows is crucial to make reliable hydrological predictions that help and support decision-making in water resources management. Hydrological post-processing methods are suitable tools to estimate the predictive uncertainty of deterministic streamflow predictions (hydrological model outputs). In general, this thesis focuses on improving hydrological post-processing methods for assessing the conditional predictive uncertainty of monthly streamflows. This thesis deal with two issues of the hydrological post-processing scheme i) the heteroscedasticity problem and ii) the intractable likelihood problem. Mainly, this thesis includes three specific aims. First and relate to the heteroscedasticity problem, we develop and evaluate a new post-processing approach, called GMM post-processor, which is based on the Bayesian joint probability modelling approach and the Gaussian mixture models. Besides, we compare the performance of the proposed post-processor with the well-known exiting post-processors for monthly streamflows across 12 MOPEX catchments. From this aim (chapter 2), we find that the GMM post-processor is the best suited for estimating the conditional predictive uncertainty of monthly streamflows, especially for dry catchments. Secondly, we introduce a method to quantify the conditional predictive uncertainty in hydrological post-processing contexts when it is cumbersome to calculate the likelihood (intractable likelihood). Sometimes, it can be challenging to estimate the likelihood itself in hydrological modelling, especially working with complex models or with ungauged catchments. Therefore, we propose the ABC post-processor that exchanges the requirement of calculating the likelihood function by the use of some sufficient summary statistics and synthetic datasets. With this aim in mind (chapter 3), we prove that the conditional predictive distribution is similarly produced by the exact predictive (MCMC post-processor) or the approximate predictive (ABC post-processor), qualitatively speaking. This finding is significant because dealing with scarce information is a common condition in hydrological studies. Finally, we apply the ABC post-processing method to estimate the uncertainty of streamflow statistics obtained from climate change projections, such as a particular case of intractable likelihood problem. From this specific objective (chapter 4), we find that the ABC post-processor approach: 1) offers more reliable projections than 14 climate models (without post-processing); 2) concerning the best climate models during the baseline period, produces more realistic uncertainty bands than the classical multi-model ensemble approach. / I would like to thank the Gobernación del Huila Scholarship Program No. 677 (Colombia) for providing the financial support for my PhD research. / Romero Cuellar, J. (2019). Improving hydrological post-processing for assessing the conditional predictive uncertainty of monthly streamflows [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/133999

Societal developments are associated with land use change, and with urbanization in particular. Urbanization can influence hydrological processes by decreasing evapotranspiration and infiltration as well as by increasing streamflow, peak flow and overland flow. This causes higher risks of flooding. Although several studies have investigated the impacts of urbanization on streamflow over the last decades, less is known about how urbanization affects the hydrological processes in peri-urban areas characterized by a complex mosaic of different land uses. This study aimed to model the impact of land use change, or more specifically urbanization, on the hydrological responses of the small peri-urban Ribeira dos Covões catchment (6.2 km2) located in central Portugal. The catchment has undergone rapid land use change since the mid- 1950s associated with conversion of agricultural fields (decreased from 48 to 4%) into woodland and urban areas, which increased from 44 to 56% and from 8 to 40%, respectively. For the study, the hydrological modelling system MIKE SHE was used. Parameters and data of climate, vegetation and soil types were used as input. There were also land use maps and daily streamflow values available for the hydrological years 2008/09 to 2012/13, which were used to calibrate and validate the model. The statistics from the calibration and validation both indicated that the model simulated the streamflow well. The model was designed to examine both how past land use change might have affected the streamflow, and to investigate the impacts on hydrology if the urban area was to be increased to cover 50% of the catchment. It was not only the importance of the urban cover’s size that was tested, but also the placement of additional urban areas. Three future scenarios were run, all with a 50% urban cover, but distributed differently within the catchment. The study did not indicate that an increase in urbanization leads to higher peak flow or streamflow. Neither could any decrease in infiltration be seen. All three scenarios however gave an increase in overland flow of approximately 10% and a decrease in evapotranspiration by 55%, regardless of where the urban areas were added. The reliability of the models can be enhanced by additional climate, soil and vegetation data. This would improve the results and make them more useful in decision making processes in the planning and management of new urban areas. / Samhällets ständiga utveckling medför förändringar i markanvändning. Utvecklingen och förändringarna är framför allt associerade med urbanisering som kan påverka ett avrinningsområdes hydrologiska processer genom att exempelvis reducera dess evapotranspiration och infiltration samt öka vattenföringen, högsta flödet och ytavrinningen. Det i sin tur ökar risken för översvämning. Trots att många studier har undersökt urbaniseringens inverkan på vattenföring de senaste decennierna saknas viss kunskap om dess påverkan på hydrologin i stadsnära avrinningsområden, kännetecknade av flera olika typer av markanvändning. Denna studie syftade till att modellera hur förändringar i markanvändning, eller mer specifikt urbanisering, påverkar hydrologin i det lilla stadsnära avrinningsområdet Ribeira dos Covões (6,2 km2) i centrala Portugal. Avrinningsområdet har genomgått snabba markanvändningsförändringar sedan mitten av 1950-talet i samband med en omvandling av åkrar (täckningsarean har minskat från 48 till 4 %) till skogsmark och urbaniserade områden, vilkas storlek har ökat från 44 till 56 % respektive 8 till 40 %. För att uppfylla syftet har den hydrologiska modellen MIKE SHE använts. Parametrar avseende klimat samt vegetations- och jordegenskaper användes som indata till modellen. Det fanns också tillgång till en markanvändningskarta över området samt dagliga flödesvärden mellan de hydrologiska åren 2008 och 2013. Dessa användes för att kalibrera och validera modellen. Statistiken för både kalibreringen och valideringen indikerade en fullt acceptabel modell. Modellen var avsedd att undersöka dels hur tidigare förändring i markanvändning kan ha påverkat vattenföringen, dels för att studera effekten på hydrologin om urbaniseringen fortgår tills dess täckning är 50 % av avrinningsområdet. Det var inte bara betydelsen av de urbana ytornas storlek som testades, utan även placeringen av dem. Tre framtidsscenarier togs fram, alla med en urban yta på 50 % fördelad olika inom avrinningsområdet. Studien indikerade inte att ytterligare urbanisering ökar vare sig flödet eller det högsta flödet. Inte heller gav de någon minskning av infiltration. Alla tre scenarierna gav emellertid en ökning av ytavrinningen med cirka 10 % och en minskning av evapotranspirationen med 55 %, oavsett placering av de urbana ytorna. Modellernas tillförlitlighet skulle kunna förbättras med hjälp av ytterligare klimat-, vegetations- och jordindata. Det skulle förbättra resultaten och göra dem användbara i beslutsfattanden vid planering och utveckling av nya urbana områden.

Thesis (PhD)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Bugan, R.D.H. Modelling and regulating hydrosalinity dynamics in the Sandspruit River catchment (Western Cape). PhD dissertation, Stellenbosch University. The presence and impacts of dryland salinity are increasingly become evident in the semi-arid Western Cape. This may have serious consequences for a region which has already been classified as water scarce. This dissertation is a first attempt at providing a methodology for regulating the hydrosalinity dynamics in a catchment affected by dryland salinity, i.e. the Sandspruit catchment, through the use of a distributed hydrological model. It documents the entire hydrological modelling process, i.e. the progression from data collection to model application. A review of previous work has revealed that salinisation is a result of land use change from perennial indigenous deep rooted vegetation to annual shallow rooted cropping systems. This has altered the water and salinity dynamics in the catchment resulting in the mobilisation of stored salts and subsequently the salinisation of land and water resources. The identification of dryland salinity mitigation measures requires thorough knowledge of the water and salinity dynamics of the study area. A detailed water balance and conceptual flow model was calculated and developed for the Sandspruit catchment. The annual streamflow and precipitation ranged between 0.026 mm a-1 - 75.401 mm a-1 and 351 and 655 mm a-1 (averaging at 473 mm a- 1), respectively. Evapotranspiration was found to be the dominant component of the water balance, as it comprises, on average, 94% of precipitation. Streamflow is interpreted to be driven by quickflow, i.e. overland flow and interflow, with minimal contribution from groundwater. Quantification of the catchment scale salinity fluxes indicated the Sandspruit catchment is in a state of salt depletion, i.e. salt output exceeds salt input. The total salt input to and output from the Sandspruit catchment ranged between 2 261 - 3 684 t Catchment-1 and 12 671 t a-1 - 21 409 t a-1, respectively. Knowledge of the spatial distribution of salt storage is essential for identifying target areas to implement mitigation measures. A correlation between the salinity of sediment samples collected during borehole drilling and the groundwater EC (r2 = 0.75) allowed for the point data of salt storage to be interpolated. Interpolated salt storage ranged between 3 t ha-1 and 674 t ha-1, exhibiting generally increasing storage with decreasing ground elevation. The quantified water and salinity fluxes formed the basis for the application of the JAMS/J2000-NaCl hydrological model in the Sandspruit catchment. The model was able to adequately simulate the hydrology of the catchment, exhibiting a daily Nash-Sutcliffe Efficiency of 0.61. The simulated and observed salt outputs exhibited discrepancies at daily scale but were comparable at an annual scale. Recharge control, through the introduction of deep rooted perennial species, has been identified as the dominant measure to mitigate the impacts of dryland salinity. The effect of various land use change scenarios on the catchment hydrosalinity balance was evaluated with the JAMS/J2000-NaCl model. The simulated hydrosalinity balance exhibited sensitivity to land use change, with rooting depth being the main factor, and the spatial distribution of vegetation. Revegetation with Mixed forests, Evergreen forests and Range Brush were most effective in reducing salt leaching, when the “salinity hotspots” were targeted for re-vegetation (Scenario 3). This re-vegetation strategy resulted in an almost 50% reduction in catchment salt output. Overall, the results of the scenario simulations provided evidence for the consideration of re-vegetation strategies as a dryland salinity mitigation measure in the Sandspruit catchment. The importance of a targeted approach was also highlighted, i.e. mitigation measures should be implemented in areas which exhibit a high salt storage. / AFRIKAANSE OPSOMMING: Die teenwoordigheid en impak van droëland versouting word duideliker in die halfdor Wes-Kaap. Dit kan ernstige gevolge inhou vir die streek wat reeds as ‘n waterskaars area geklassifiseer is. Hierdie verhandeling is ‘n poging om ‘n metode vir die regulering van waterversoutingsdinamiek in ‘n opvangsgebied wat deur verbrakking van grond geaffekteer is, i.e. die Sandspruit opvangsgebied, te bepaal deur gebruik te maak van ‘n verspreide hidrologiese model. Dit dokumenteer die volledige hidrologiese modeleringsproses, i.e. vanaf die versameling van data tot die aanwending van die model. ‘n Oorsig van vorige studies bevestig dat versouting ‘n gevolg is van die verandering vanaf meerjarige inheemse plantegroei met diep wortelstelsels tot die verbouing van gewasse met vlak wortelstelsels. Dit het ‘n verandering in die water en versoutingsdinamiek in die opvangsgebied tot gevolg gehad in soverre dat dit die mobilisering van versamelde soute en gevolglike versouting van die grond en waterbronne tot gevolg gehad het. Die identifikasie van maatreëls om droëland versouting te verminder, vereis ‘n deeglike kennis van die water- en versoutingsdinamiek van die studie gebied. ‘n Gedetailleerde waterbalans en konseptuele vloeimodel was bereken vir die Sandspruit opvangsgebied. Die jaarlikse stroomvloei en neerslag varieer tussen 0.026 - 75.401 mm a-1 en 351 - 655 mm a-1 (gemiddeld 473 mm a-1), onderskeidelik. Dit is bevind dat evapotranspirasie die dominante komponent is van die waterbalans, aangesien dit 94% uitmaak van die neerslag. Stroomvloei word aangedryf deur snelvloei, i.e oppervlakvloei en deurvloei met minimale bydrae van grondwater. Die omvang van die opvangsgebied se soutgehalte het aangedui dat die Sandspruit opvangsgebied tans ‘n toestand van soutvermindering ondervind, i.e. sout invloei word oorskrei deur sout uitvloei. Die totale sout in- en uitvloei in die Sandspruit opvangsgebied het gewissel tussen 2 261 - 3 684 t Opvangsgebied-1 en 12 671 - 21 409 t a-1 onderskeidelik. Kennis van die ruimtelike verspreiding van opbou van soute in die grond is belangrik om areas te identifiseer vir die toepassing van voorsorgmaatreëls. ‘n Korrelasie tussen die soutinhoud van sediment monsters wat versamel is tydens die boor van boorgate en die grondwater EC (r2 = 0.75) het die interpolasie van puntdata waar sout aansamel toegelaat. Hierdie interpolasie van sout aansameling het gewissel tussen 3 t ha-1 and 674 t ha-1 en bewys ‘n algemeen verhoogde opbou met vermindering in grond elevasie. Die hoeveelheidsbepaling van water en die versoutings roetering vorm die basis vir die aanwending van die JAMS/J2000-NaCl hidrologiese model in die Sandspruit opvangsgebied. Die model het ‘n geskikte simulasie van die hidrologie van die opvangsgebied geimplimenteer, en het ‘n daaglikse Nash-Sutcliffe Efficiency van 0.61 getoon. Die gesimuleerde en waargenome sout afvoer het teenstrydighede getoon t.o.v daaglike metings maar was verenigbaar op ‘n jaarlikse skaal. Aanvullingsbeheer deur die aanplanting van meerjarige spesies met diep wortelstelsels is geidentifiseer as ‘n oorwegende maatreël om die impak van verbrakking van grond teë te werk. Die effek van verskeie veranderde grondgebuike op die balans van die opvangsgebied se hidro-soutgehalte is geëvalueer met die JAMS/J2000-NaCl model. Die balans van gesimuleerde hidro-saliniteit het ‘n sensitiwiteit t.o.v veranderde grondgebruik getoon, met die diepte van wortelstels as die hoof faktor, asook die ruimtelike verspreiding van plantegroei. Hervestiging van verskeie tipes bome, meerjarige bome en “Range Brush” was die effektiefste t.o.v die vermindering in sout uitloging waar die soutgraad konsentrasie areas ge-oormerk was vir hervestiging van plantegroei (Scenario 3). Die strategie van hervestinging het ‘n afname van 50% in versouting in die opvangsgebied getoon. In die geheel het die resultate van die simulasies genoegsame bewys gelewer dat ‘n strategie van hervestiging en groei as ‘n voorsorg maatreël kan dien om droëland versouting in die Sandspruit opvangsgebied teen te werk. Die belangrikeid daarvan om ‘n geteikende benadering te volg is benadruk, i.e. voorsorg maatreëls kan toegepas word in areas met hoë soutgehalte.

Muitos rios brasileiros ainda não são monitorados. A carência de informações relevantes costuma gerar diversos problemas para a administração pública. Por vezes, essa falta de dados pode ser compensada por meio de modelagem hidrológica, que requer um conhecimento prévio sobre a bacia a ser estudada. Atualmente, a mudança no uso e cobertura do solo em bacias hidrográficas é um dos temas mais abordados nas pesquisas hidrológicas, podendo a avaliação dos impactos causados por essa ser feita através de modelagem hidrológica. O presente trabalho utilizou o framework JAMS (Jena Adaptable Modelling System) na elaboração de um modelo hidrológico para a bacia do Ribeirão da Onça, a qual está localizada em zona de afloramento do Sistema Aquífero Guarani, um dos mais importantes aquíferos transfronteiriços do mundo. A bacia é predominantemente rural, logo, seu uso e ocupação do solo variam ao longo do tempo. Sendo assim, objetivou-se avaliar os efeitos das alterações de uso do solo no regime hidrológico da bacia por meio da elaboração de múltiplos modelos hidrológicos no JAMS/J2K, os quais foram calibrados independentemente (de 2008 a 2015) e validados por um modelo atual (2017), a fim de se gerar uma parametrização capaz de predizer os efeitos hidrológicos decorrentes de alterações no uso e ocupação do solo da bacia. Previamente à elaboração dos modelos, procedeu-se à validação dos dados hidrológicos e climatológicos coletados e disponíveis da bacia, por meio da análise das correlações entre as medições dos equipamentos, feita por programa elaborado em Python. Em seguida, elaboraram-se mapas de uso do solo para os anos de 2008, 2011, 2013, 2015 e 2017. Então, os modelos com seus conjuntos de URHs (Unidades de Resposta Hidrológica) específicos foram calibrados, e os parâmetros ótimos encontrados para cada modelo foram aplicados nos demais para identificação de quais poderiam ser os mais representativos. Durante esta etapa, verificou-se que o modelo de 2013 comportava-se anomalamente, devido à estiagem ocorrida em seu período de calibração, o que justificou sua retirada das etapas seguintes. Em seguida, um programa criado em Python permitiu que os arquivos .dat gerados durante a calibração fossem analisados visualmente, por meio de gráficos de dispersão e plots violinos, embasando a tomada de decisão relativa à redução da amplitude de variação dos parâmetros para uma posterior busca manual por parâmetros representativos temporalmente. Os parâmetros encontrados produziram modelos com NSE variando de 0,25 a 0,39; PBIAS de -20,98 a -0,74 e R2 de 0,45 a 0,65, sendo que o modelo de validação (2017) obteve NSE de 0,26; PBIAS de -1,78 e R2 de 0,45; indicando que a parametrização encontrada, apesar de não conseguir produzir modelos que eficientemente reproduzam os picos no escoamento, é capaz de estimar satisfatoriamente o escoamento de base, mesmo em condições de mudanças de uso e ocupação do solo. Com isso, realizou-se a aplicação do conjunto de parâmetros em cenários hipotéticos de uso e ocupação do solo, que produziu resultados coerentes com o que se espera. Além disso, também se realizou a setorização do modelo, utilizando os dados de vazão de duas calhas Parshall instaladas na bacia. No entanto, não houve êxito na setorização, evidenciado pelos valores de NSE (-35,41 e 88,08), PBIAS (118,63 e 118,81) e R2 (0,15 e 0,12). O fraco desempenho na setorização pode ser corrigido calibrando-se o modelo espacialmente, em adição à calibração temporal, ou seja, com múltiplos dados de entrada de vazão, localizados em pontos distintos na bacia. / Many Brazilian rivers are not monitored. The lack of relevant information may generate multiple problems for public administration. Sometimes this data may be supplied through hydrological modelling, which requires a previous knowledge regarding the watershed that will be studied. Currently, the land use and cover change in watersheds is one of the most researched themes in the hydrological scientific community, with the impacts caused by it being able t obe assessed by hydrological modelling. In that sense, this work has used the framework JAMS (Jena Adaptable Modelling System) in the elaboration of a hydrological model for the Ribeirão da Onça catchment, which is located in an outcrop zone of the Guarani Aquifer System, one of the largest transboundary aquifers in the world. The catchment is mainly rural; thus, its land use and occupation vary heavily over time. In this context, the intent of this work was to evaluate the effects of the land use/cover changes in the hydrological processes through the elaboration of multiple J2K/JAMS hydrological models, which were calibrated individually (2008 through 2015) and validated with a recent model (2017), with the goal of creating a model that is able to predict long term hydrological effects of land use/cover changes in the catchment. Before creating the models, a validation of the hydrological and climatic data available in the catchment was done, through the analysis of the correlations between the measures, achieved with the use of a Python software. After that, land use maps were elaborated for the years 2008, 2011, 2013, 2015 and 2017. Then, the models with their HRU (Hydrological Response Units) specific sets were calibrated, then the optimal parameters for each model were applied on the other ones, to assess which were the most representative. During this step, the 2013 model was deemed anomalous, due to the drought that occurred during its calibration period, which justified its removal from the following stages. After that, an application made in Python allowed the .dat files generated during calibration to be visually analysed, through scatter and violin plots, aiding the decisions regarding the new maximum and minimum values for the parameters, preceding a manual search for the globally representative parameters set. The set that was found produced models with NSE varying from 0.25 to 0.39, PBIAS from -20,98 to -0,74 and R2 from 0,45 to 0,65, being that the validation model (2017) achieved an NSE of 0.26; PBIAS of -1.78 and R2 of 0.45, meaning that the parameters found, despite not being able to effectively reproduce the runnof peak values, is able to satisfactorily estimate the base runoff, even in land use and cover change conditions. With that, the parameters set found was applied in hypothetical scenarios of land use and cover, which produced coherent results with what was expected. A model sectorization was also attempted, using discharge data from two Parshall flumes installed in the catchment. However, there was no success in the attempt, evidenced by the NSE (-35.41 and 88.08), PBIAS (118.63 and 118.81) and R2 (0.15 and 0.12) values. The weak performance of the sectorization may be fixed by calibrating the model spatially, in addition to the calibration in regards to time. In other words, with multiple input discharge data, located in distinct points inside the catchment.