Quantifying the Impacts of Land Use, Management and Climate Change on Water Resources in Missouri River Basin

A location-specific evaluation of hydrological landscape responses concerning past and projected climate and land use land cover (LULC) changes can provide a powerful intellectual basis for developing efficient and profitable agroecosystems, and overcoming uncertain and detrimental consequences of LULC and climate shifts. This dissertation assessed the impacts of land use, management, and climate change on water resources in the Missouri River Basin (MRB) through four specific studies that included: (i) to study the responses of leached nutrient concentrations and soil health to winter rye cover crop (CC) under no-till corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation, (ii) to simulate hydrological responses of integrated crop-livestock (ICL) system under projected climate changes in an agricultural watershed, (iii) to evaluate the hydrological landscape responses in relation to past (1986-2018) LULC and climate shifts across South Dakota (SD), and (iv) to evaluate the hydrological landscape responses in relation to past (1986-2018) LULC and climate shifts across MRB. Cover cropping has been promoted for the ecological agricultural intensification, however, the vulnerability of CC establishment and expected soil health and water quality benefits under short and cold growing periods for CC are of concerns among producers in the northern Great Plains (NGP) region. Thus, a field experiment from 2017 to 2020 was conducted to assess the impacts of winter rye (Secale cereale L.) CC on soil health and water quality parameters under a no-till corn-soybean rotation at Southeast Research Farm (SERF), Beresford, SD. Interestingly, the study site faced one dry (2020) and two abnormally wet (2018 and 2019) years which received 31% lower (2020), and 31% (2018) and 23% (2019) higher precipitation, respectively, than the annual average (1953-2019). Data showed that biomass of the rye CC was 251 kg ha-1 in 2018, 1213 kg ha-1 in 2019, and 147 kg ha-1 in 2020, coinciding with contrasting growing degree days i.e., 1458, 2042, 794, respectively, as a consequence of variable weather conditions. Cover cropping did not impact water quality for the majority of the study period. However, a significant reduction in leached nitrate (~19-20%) and total nitrogen (TN) (~8.5-16%) concentrations were found only in 2019, pertaining to sequestered 18.8 kg N ha-1. Rye CC showed 13 and 11% significantly higher microbially active carbon and water-extractable organic nitrogen, respectively, than the control (No CC) treatment. The non-significant impacts on soil health indicators due to winter rye showed that study duration (3 years) may not be sufficient to see the beneficial impacts of cover crop on soils. However, significant reductions in leached nitrate and TN concentrations for one (2019) out of three study years suggest that well-established rye CC (biomass = 1213 kg ha-1; which was 4.8 and 8.3 times higher than that in 2018 and 2020) has the potential of reducing nutrient leaching and enhancing soil health for the study region. The ICL systems, when well managed properly, have beneficial impacts on soils and water yield, however, very limited studies are available due to the complexity of these integrated systems. Thus, a simulation study was conducted to assess the hydrological impacts of long-term implementation of ICL systems at watershed scale with the projected climate scenarios on water yield using the Soil and Water Assessment Tool (SWAT) model over two time periods [i.e. Near Future (2021-2050) and Far Future (2070-2099)]. This study was conducted in three phases over Skunk Creek Watershed (SCW), SD, USA. In phase I, the impact of long-term ICL system implementation (1976- 2005; 30 years) on soil hydrology was evaluated. Phase II and phase III evaluated the impacts of projected climate changes under existing land cover and ICL system, respectively. Outcomes of phase I showed a significant decrease in water yield and surface runoff. Phase II showed the susceptibility of SCW to extreme events such as floods and waterlogging during spring, and droughts during summers under the projected climate changes. Phase III showed the reduction in water yield and surface runoff due to the ICL system and minimizing the induced detrimental impacts only due to climate change. Evapotranspiration (ET) plays a significant role in crop growth and development, therefore, an accurate estimation of ET is very important for water use and availability. The past hydrological landscape responses were studied using well-validated (r2 = 0.91, PBIAS= -4%, and %RMSE = 11.8%) actual evapotranspiration (ETa) time-series (1986- 2018) estimations. The developed ETa products were further used to understand the crop water-use (CWU) characteristics and existing historic mono-directional (increasing or decreasing) trends across the SD and MRB regions. Spatial variability of the Operational Simplified Surface Energy Balance (SSEBop) model- and Landsat-based ETa estimations showed strong correspondence with land cover and climate across the basin. The drier foothills in northwestern MRB, dominated by grassland/shrubland, showed lower ETa (\u3c 400 mm/year), whereas, cropland dominated regions in lower semi-humid MRB and forested headwater exhibited higher ETa (\u3e 500 mm/year). For the SD region, Mann Kendall trend analysis revealed an absence of a significant trend in annual CWU at a regional scale due to the combined impact of varying weather conditions, and the presence of both increasing (12%) and decreasing (9%) CWU trends over a substantial portion at the pixel-scale. Whereas, for the MRB, summer season CWU trend analysis revealed a significant increasing trend at the regional-scale with 30% MRB cropland pixels under a significant increasing trend at pixel-scale. The existing increasing trends can be explained by the shift in agricultural practices, increased irrigated cropland area, higher productions, moisture regime shifts, and decreased risk of farming in the dry areas. Moreover, the decreasing trend pixels could be the result of the dynamic conversion of wetlands to croplands, decreased and improved irrigation and water management practices in the region. Overall, both studies highlight the potential of Landsat imagery and remote sensing-based ETa modeling approaches in generating historical time-series ETa maps over a wide range of elevation, vegetation, and climate

The desertification context

Desertification is a critical issue for Mediterranean drylands. Climate change is expected to aggravate its extension and severity by reinforcing the biophysical driving forces behind desertification processes: hydrology, vegetation cover and soil erosion. The main objective of this thesis is to assess the vulnerability of Mediterranean watersheds to climate change, by estimating impacts on desertification drivers and the watersheds’ resilience to them. To achieve this objective, a modeling framework capable of analyzing the processes linking climate and the main drivers is developed. The framework couples different models adapted to different spatial and temporal scales. A new model for the event scale is developed, the MEFIDIS model, with a focus on the particular processes governing Mediterranean watersheds. Model results are compared with desertification thresholds to estimate resilience. This methodology is applied to two contrasting study areas: the Guadiana and the Tejo, which currently present a semi-arid and humid climate. The main conclusions taken from this work can be summarized as follows: • hydrological processes show a high sensitivity to climate change, leading to a significant decrease in runoff and an increase in temporal variability; • vegetation processes appear to be less sensitive, with negative impacts for agricultural species and forests, and positive impacts for Mediterranean species; • changes to soil erosion processes appear to depend on the balance between changes to surface runoff and vegetation cover, itself governed by relationship between changes to temperature and rainfall; • as the magnitude of changes to climate increases, desertification thresholds are surpassed in a sequential way, starting with the watersheds’ ability to sustain current water demands and followed by the vegetation support capacity; • the most important thresholds appear to be a temperature increase of +3.5 to +4.5 ºC and a rainfall decrease of -10 to -20 %; • rainfall changes beyond this threshold could lead to severe water stress occurring even if current water uses are moderated, with droughts occurring in 1 out of 4 years; • temperature changes beyond this threshold could lead to a decrease in agricultural yield accompanied by an increase in soil erosion for croplands; • combined changes of temperature and rainfall beyond the thresholds could shift both systems towards a more arid state, leading to severe water stresses and significant changes to the support capacity for current agriculture and natural vegetation in both study areas.Supported by the Portuguese Foundation for Science and Technology and the European Union under Operational Program “Science and Innovation” (POCI 2010), Ph.D. grant ref. SFRH/BD/5059/200

Are all wetland models the same? Comparing wetland models and streamflow regulation of catchment-scale hydrological modelling tools under a changing climate

Comparing how wetlands are simulated in different hydrological modelling tools is needed to identify their suitability in different contexts. A simulated wetland will result in predictions of streamflow regulation, e.g., storing flood water and reducing high flows and releasing water in drier periods, which may or may not be realistic for a given area. Evaluating wetland models is critical for navigating the different types of physical wetlands with variable influences on streamflow, and the different simulated wetlands conceived in the plethora of modelling tools (i.e. software) available for use. A recent study found that sometimes wetlands are excluded from hydrological models used to inform water resource decisions. When wetlands are included in a hydrological model, few studies identify process similarities between the actual and modelled wetland or the realism of the modelled impacts of the wetland on streamflow before applying the model's output to water resource decisions. This research aims to identify and evaluate wetland characteristics, processes and impacts on catchment streamflow in different modelling tools and models (i.e. setups in a tool). Evaluating wetland models supports wetland-inclusive modelling and ensures that a wetland model is hydrologically sound and suitable. An unchannelled valley-bottom wetland located in the upper Kromme catchment, Eastern Cape, South Africa, was used. Wetland models were compared as independent units conceptually and as functional units within the catchment by modelling. First, using qualitative analysis, a conceptual assessment of wetland model structures in ACRU, WRSM-Pitman, MIKE SHE coupled with Hydro River and SWAT were considered in the context of the case study wetland. Second, using quantitative analysis, model outputs from wetland models in ACRU and WRSM-Pitman were assessed for model performance, behaviour and streamflow regulation during droughts and floods. The predicted impact of the wetland on catchment hydrology was determined from scenarios with and without a wetland and modelled wetland storage fluxes over the whole simulation period, four severe floods and three drought periods. The results from the qualitative and quantitative comparisons suggest that similarities between the physical and simulated wetland improves the likelihood of model suitability, good model performance and streamflow regulation predictions. Additionally, models setup for the same wetland with the same input data simulated potentially acceptable but different streamflow totals: for an observed total of 9.13 Mm3 ; WRSM-Pitman's comprehensive wetland simulated 10.64 Mm3 ; and from ACRU's riparian zone and wetland HRU's simulated 11.31 Mm3 and 8.89 Mm3 , respectively. Modelled actual evapotranspiration was underestimated by the riparian zone wetland (946.08 mm), overestimated in the comprehensive wetland model (2 054.80 mm) and moderately similar in the wetland HRU when compared with remotely-sensed data (1 520.30 mm). During extreme events, all models simulated flood attenuation while drought responses were variable (two wetland models predicted streamflow attenuation). By implication, the results suggest that good model performance does not guarantee the simulation of expected streamflow regulation roles recorded in literature. Furthermore, variable water yields and wetland impacts from the models demonstrated the possibility for different modelling efforts to result in different water supply, use and conservation measures. The study highlights the importance of contextualising model output for catchments with wetlands before applying the simulations to impact assessments or future climate scenarios

A Hydro-Climatic Analysis with Policy Implications for the Logone catchment, Lake Chad Basin

As a response to the generally perceived divide between the scientists and policy makers in decision making, this thesis seeks to bridge the gap between science and policy by framing the research questions based on the views expressed by policy makers. The thesis attempts to develop an approach for linking biophysical and social sciences research to support the use of scientific knowledge in decision making within the policy arena. Q methodology was used to derive discourses obtained from interviews with a range of stakeholders in government, non-governmental organizations, civil society, and academia in Cameroun. The aim was to reveal the different discourses in climate change in general and on the relationship between science and policy and how it can be applied in hydro – climatic research. Three different discourses emerged from the study. These highlighted concerns that water resources in the Sudano-Sahel zone of the country were vulnerable to climate change owing to past climate variability which could lead to food insecurity in Cameroun. The policy makers expressed the need for the scientists to conduct climate change impact studies on water resources in the region, stating that results from such studies could be useful for developing climate change adaptation policies. Results from the different homogeneity tests indicated that rainfall was homogenous across the Logone catchment during the period under study (1951 – 2000). A yearly trend analysis revealed the presence of statistically significant negative trends in annual rainfall time series at all stations across the catchment; while trend analysis using a monthly time-step revealed the presence of statistically insignificant positive trends at 32% of rain gauge stations. CMIP5 model validation against historical observations (1980 – 2005) indicated that the models were able to simulate the annual precipitation cycle in the LCB although some models overestimated precipitation during the dry season and underestimated during the rainy season. Furthermore, analysis revealed that by the middle of the century (2050 – 2075), future annual precipitation is projected to increase in the LCB by 2.5% and 5% while monsoon precipitation will decrease by 11.60% and 5.30% respectively under RCP4.5 and RCP8.5 scenarios relative to the historical period. The uncertainty range for annual precipitation is about 12% and 17% for annual and monsoon precipitation respectively under RCP4.5 and RCP8.5 scenarios. Although the uncertainty range for future precipitation projections for most models and the reliability ensemble average (REA) mean lie within the range of natural climate variability, additional analysis are needed for results to be useful for any future planning to enhance water resources management in the study area. Hydrological modelling in the Logone catchment using the SWAT model indicated that by using different calibration techniques, it is possible to reveal differences in the hydrological behavior in the different parts of the catchment using different parameter values. Results of SPI and SSI analysis showed that both the Sudano and Sahelian zones of the catchment are equally prone to droughts and floods. However, the Sudano zone is more sensitive to drier conditions while the Sahelian zone is sensitive to wetter conditions. In this thesis, meeting the needs of the policy makers could not be achieved without gaining an understanding of the hydrological behaviour of the study area which is a pre-requisite for any such studies that involves the simulation of climate change impacts on water resources. Therefore, the hydrological modelling exercise and the different statistical analysis carried out in the context of this thesis were all aimed at developing a rich portfolio of peer reviewed information database which the policy makers will find useful to develop relevant climate change adaptation policies and also enhance the management of water resources in the region

Modeling hydrological processes in a semi-arid mountainous catchment at the regional scale

In the Upper Drâa Valley (14,988 km2) on the southern slopes of the Moroccan High Atlas Mountains, a highly variable precipitation and large evaporation losses cause major water availability problems. The combined effect of projected increase in water demand and temperature and a decrease in precipitation poses a major challenge for water managers in the region. To assess the actual state of the hydrological system (1978-2007), but also the impacts of future changes (2000-2049) a conceptual model, adapted to the characteristics of a semi-arid mountainous environment, has been applied. A spatially explicit altitudinal representation, an oasis-irrigation routine, a second linear storage aquifer and a reservoir management module have been implemented in the SWAT model, extending it to SWAT-MAROC (SWAT-Mountainous and Arid Regions Oriented Concept). During the validation period the model performs well on a monthly timescale at the basin outlet (CME: 0.89) and satisfactorily at the two main tributaries Oued Ouarzazate (CME: 0.69) and Oued Dades (CME: 0.62). Furthermore model results are in line with validation data obtained from groundwater, snow and irrigation studies. Nevertheless the model exhibits flaws in representing water availability in groundwater-fed oases and soil water dynamics. Considering the variable sources of uncertainty, especially in arid and mountainous regions, a wide-ranging uncertainty assessment scheme, quantifying and comparing uncertainties with a signal-to-noise ratio, has been developed and applied. Uncertainties from the hydrological model are highest, followed by divergent signals from climate change ensembles, while the downscaling method has only minor effects on model results. It has been shown that climate change effects for the period 2000-2029 are subject to considerable uncertainties and no clear trends could be identified. For the period 2020-2049 the following developments are “likely” according to the IPCC terminology. Despite a decrease in precipitation (-11%) and especially snowfall (-31%), irrigation water availability in the surface water dependent oasis remains high enough (-5%) to sustain agriculture to the current extent. In contrast, water availability at the reservoir is decreasing disproportionately high (-17%). Therefore the potential for riparian conflicts between the Upper Drâa and the Middle Drâa might augment. A further finding is that the reservoir Mansour-Eddahbi is likely to become inoperable due to siltation in the period 2030-2042, dependent on the assumed pathways of socio-economic development.Modellierung hydrologischer Prozesse eines semi-ariden, gebirgigen Einzugsgebietes auf der regionalen Skala Das südmarokkanische Obere Drâatal (14.988 km2), an der Südabdachung des Hohen Atlas gelegen, ist durch eine hohe Niederschlagsvariabilität und starke Verdunstung gekennzeichnet, die bereits heute die Wasserverfügbarkeit beeinträchtigen. Die kombinierte Wirkung des prognostizierten Anstiegs der Wassernachfrage und der Temperatur sowie des Rückgangs der Niederschläge stellen eine große Herausforderung für das Wassermanagement dar. Um den aktuellen Zustand des hydrologischen Systems (1978-2007) zu beurteilen und die Auswirkungen von zukünftigen Veränderungen (2000-2049) zu erfassen, wird ein konzeptionelles Modell verwendet, das an die Eigenschaften der semi-ariden gebirgigen Region angepasst wurde. Dafür ist das SWAT-Modell um eine räumlich explizite Darstellung der Höhengliederung, ein Oasen-Bewässerungs-Modul, einen zweiten Grundwasserleiter und ein Stausee-Management-Modul zu SWAT-MAROC (SWAT – Mountainous and Arid Regions Oriented Concept) erweitert worden. Während der Validierungsphase erzielte das Modell auf monatlicher Zeitskala am Gebietsauslass (CME: 0,89) sowie an den beiden wichtigsten Zuflüssen Oued Ouarzazate (CME: 0,69) und Oued Dades (CME: 0,62) gute bis zufriedenstellende Ergebnisse. Darüber hinaus stehen Modellergebnisse im Einklang mit Validierungsdaten aus Grundwasser-, Schnee- und Bewässerungsstudien. Mängel zeigt das Modell bei der Simulation des Wasserdargebots in grundwassergespeisten Oasen und der Bodenwasserdynamik. Um diversen Unsicherheitsquellen, vor allem in ariden und bergigen Regionen, gerecht zu werden, sind im Rahmen eines umfassenden Bewertungsschemas quantifizierbare Unsicherheiten mit einer Signal-to-Noise-Ratio verglichen worden. Unsicherheiten aus dem hydrologischen Modell sind am höchsten, gefolgt von divergenten Signalen aus den Klimaensembles, während das Downscaling nur geringe Auswirkungen auf die Trends zeigt. Die Auswirkungen des Klimawandels für den Zeitraum 2000-2029 sind mit erheblichen Unsicherheiten behaftet und weisen keine eindeutigen Trends auf. Für den Zeitraum 2020-2049 sind folgende Entwicklungen „wahrscheinlich“ (entsprechend der IPCC Terminologie). Trotz einer Abnahme des Niederschlag (-11%) und insbesondere des Schneefalls (-31%), ist die Bewässerungswasserverfügbarkeit an den Oberflächenwasseroasen hoch genug (-5%), um die Landwirtschaft im aktuellen Umfang aufrecht zu erhalten. Die Wasserverfügbarkeit am Stausee hingegen nimmt überproportional ab (-17%). Deshalb könnte das Konfliktpotenzial zwischen den Wassernutzern des Oberen und Mittleren Drâa zunehmen. Weitere Implikationen für das mittlere Drâatal beinhaltet der Sedimenteintrag in den Stausee Mansour-Eddahbi. Dieser wird voraussichtlich in der Periode 2030-2042 versandet sein.Modélisation des processus hydrologiques dans un bassin versant montagneux semi-aride à l'échelle régional Dans la Haute V allée du Drâa ( 14.988 km2) située au sud du Haut Atlas M arocain, une précipitation très variable et de grandes pertes d' évaporation causent d es problèmes de disponibilité en eau. L'effet combiné projeté de l'augmentation de la demande e n eau et la température et une diminution des précipitations prévues constitue un défi majeur pour les gestionnaires de l'eau dans la région. Pour évaluer l'état actuel du système hydrologique (1978 - 2007), m ais aussi les impacts des changements futurs ( 2000 - 2049), un modèle conceptuel adapté aux caractéristiques d'un milieu semi - aride montagneuse, a été appliquée. Une représentation spatialement explicite d'altitude, une routine d'irrigation des oasis , un sec ond aquifère et un module de gestion des réservoirs ont été mis en œuvre dans le modèle SWAT, en l'étendant à SWAT – MAROC (SWAT – Mountainous and Arid Regions Oriented Concept) . Dans la période de validation , le modèle simule qualitativement bien sur une échelle de temps mensuelle à l'exutoire du bassin (CME: 0,89) ainsi que dans les deux principaux affluents Oued Ouarzazate (CME: 0,69) et Oued Dad e s (CME: 0,62). En outre les résultats du modèle sont en accord avec les données de validation obtenues à part ir d'études des e aux souterraines, de neige et d' irrigation. Néanmoins, le modèle présente des fai b l esse s dans la représentation de la disponibilité en eau dans les oasis alimentées par les eaux souterraines et de la dynamique de l'eau du sol. Les sources variables d'incertitude, en particulier dans les régions arides et montagneuses, ont été comparées dans le cadre d'un système d' évaluation des incertitudes, avec un Signal - to - Noise - Ratio . Les incertitudes de la modélisation hydrologique sont les plus élevé es suivi e s par des signaux divergents des ensembles de changement climatique, tandis que la méthode de downscaling n'a que des effets mineurs sur les résultats du modèle. Il a été démontré, que les effets du changement climatique pour la période 2000 - 2029 sont sujets à des incertitudes considérables et aucune tendance claire n'a pu être identifiée . Pour la période 2020 - 2049 les développements suivants sont "probables" selon la terminologie du GIEC. Malgré une diminution des précipitations ( - 11%) et surtout des chutes de neige ( - 31%), la disponibilité en eau d'irrigation dans l es oasis dépendant des eau x de surface reste assez élevé e ( - 5%) pour soutenir l'agriculture dans la mesure actuelle. En contraste, la disponibilité en eau , au niveau du réservoir est an ormalement en forte baisse ( - 17%). Par conséquent, le potentiel de conflits entre les riverains du Haute et Moyen Drâa pourrait augmenter. Une autre constatation est q ue le réservoir Mansour - Eddahbi est susceptible de devenir inutilisable en raison de l'en vasement dans la période 2030 - 2042

Impacts of Land Cover and Climate Change on Water Resources in Suasco River Watershed

Hydrological balance and biogeochemical processes in watershed are significantly influenced by changes in land use land cover (LULC) and climate change. Those changes can influence interception, evapotranspiration (ET), infiltration, soil moisture, water balance and biogeochemical cycling of carbon, nitrogen and other elements at regional to global scales. The impacts of these hydrological disturbances are generally reflected in form of increasing runoff rate and volume, more intense and frequent floods, decreasing groundwater recharge and base flow, elevated levels of sediments and increase in concentration of nutrients in both streams and shallow groundwater. Water quality of Sudbury, Assabet and Concord (SuAsCo) watershed in Massachusetts is also compromised because of influx of runoff, sediments and nutrients. There is a crucial need to evaluate the synergistic effects of LULC change and climate change on the water quality and water quantity in a watershed system. A watershed simulation model is used to simulate hydrologic processes and water quality changes in sediment loads, total nitrogen (TN), and total phosphorus (TP). The model is calibrated and validated with field-measured data. Climatic scenarios are represented by downscaled regional projections from Global Climate Model (GCM) models and regional built out scenarios of LULC are used to assess the impacts of projected LULC and climate change on water quality and water quantity. Simultaneous changes in LULC and climate significantly affect the water resources in the SuAsCo River watershed. Change in climate increased ET (4.7 %) because of high temperature, but independent change in land cover reduced ET (6.5%) because of less available vegetation. Combined change in land cover and climate reduced ET (2.1%) overall, which indicates that land cover change has significant impact on ET. Change in climate increased total run off (6%) and this increase is more significant as compared to 2.7 % increase in total runoff caused by land cover change. Change in land cover increased surface runoff more significantly (69.2%) than 7.9 % increase caused by climate change. Combined change in land cover and climate further increased the average storm peak volume (12.8 percent) because of high precipitation and impervious area in future. There is a potential for reducing runoff, sediments and nutrients loads by using conservation policies and adaptation strategies. This research provides valuable information about the dynamics of watershed system, as well as the complex processes that impair water resources

Adaptive agricultural water resources management in a desert river basin: Insights from hydrologic modeling

Many arid and semi-arid areas around the world are projected to experience increasing aridity levels throughout the 21st century. The increase in the frequency and severity of droughts and changing precipitation patterns will likely intensify the water shortages. The widening gap between water availability and demand in arid and semi-arid areas necessitates better understanding of water quantity and quality issues in these regions. The objectives of this dissertation are: (1) reviewing the challenges of applying soil and water assessment tool (SWAT) watershed hydrology and water quality model in arid/semi-arid regions with irrigated agriculture; (2) robust analysis of water availability in an example desert river basin under plausible future climate conditions; and (3) evaluating water and land management interventions for adaptive water resources management and agricultural water sustainability. The results show the possibility of dryer future and more saline water resources, increasing the risks of crop loss, especially for high-value crops like pecan. The current agricultural water management practices that support growing pecan orchards will be difficult to implement in the future due to growing water shortages. It is timely for agricultural producers to develop preparedness to use water with marginal quality or take action to reduce the net consumptive water use of their operations by improving agricultural water management. Changing the crop pattern and applying deficit irrigation for water intensive crops like alfalfa helps reduce the irrigation water consumption while growing more drought resistant crops such as pistachio and pomegranate could improve the resilience of agricultural producers to long-term droughts. Challenges of modeling agricultural watersheds in arid/semi-arid regions are addressed in this dissertation to provide a technical road map for watershed modelers interested in applying SWAT

Impacts of Anthropogenic Activities on Watersheds in a Changing Climate

The immediate goal of this Special Issue was the characterization of land uses and occupations (LULC) in watersheds and the assessment of impacts caused by anthropogenic activities. The goal was immediate because the ultimate purpose was to help bring disturbed watersheds to a better condition or a utopian sustainable status. The steps followed to attain this objective included publishing studies on the understanding of factors and variables that control hydrology and water quality changes in response to human activities. Following this first step, the Special Issue selected work that described adaption measures capable of improving the watershed condition (water availability and quality), namely LULC conversions (e.g., monocultures into agro-forestry systems). Concerning the LULC measures, however, efficacy was questioned unless supported by public programs that force consumers to participate in concomitant costs, because conversions may be viewed as an environmental service