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Technical University of Denmark (DTU) (2012)

Integrated ecohydrological modeling at the catchment scale

Loinaz, Maria Christina

Titre : Integrated ecohydrological modeling at the catchment scale.

Auteur : Loinaz, Maria Christina

Université de soutenance : Technical University of Denmark (DTU)

Grade : Doctoral Thesis (PhD) 2012

Résumé partiel
Water resources managers increasingly face the challenge of balancing water allocation in environments of water scarcity, high food production demand, and rising pollution levels. Scientists face the challenge of providing managers with accurate predictions on the outcome of management alternatives that help to guide the decision process. The need to take a holistic approach and evaluate interrelated factors that impact the availability of water resources, such as climate, landscape processes, and surface water interaction with groundwater at the catchment scale is increasingly recognized. It is through this approach that human interaction with the environment can be properly assessed. The field of ecohydrology is an interdisciplinary science that seeks to understand the links between the physicochemical stressors with biological receptors to support policy for the sustainability of natural resources. This PhD study focuses in developing integrated ecohydrological models at the catchment scale that quantify the changes in receptors caused changes in environmental stressors as a results of management alternatives. The modeling approach involves coupling spatially distributed and physically based hydrological models to process-based ecological models. The output is a measure of ecological status as a result of a changing environment. The models include the dynamic interactions between the main components of the hydrologic cycle, with a focus on surface water and groundwater interactions, which are key drivers in aquatic ecology. Another key driver in aquatic ecology is stream temperature, which traditionally has been simulated at the local stream scale with point source thermal loads. This study has extended the previous work on stream temperature model development to include diffuse loads at the catchment scale. The research methodology was applied in two case studies, both located in agricultural catchments. One case, located in Idaho, US, deals with the issues of water scarcity, intensive agricultural practices, high stream temperatures, and fish habitat degradation, which are widespread problems in the Western US. To evaluate management alternatives for an intensively cultivated valley an integrated surface water-groundwater and stream temperature model was developed. The model was coupled to an ecological model that predicts fish growth as a function of temperature and other factors. Among the main findings of this study is that groundwater flow has a strong influence on stream temperature levels and dynamics in areas with high surface water and groundwater exchange. Moreover, the strong relationship between stream iv temperature and the volume and source of streamflow (snowmelt, groundwater, urban and agricultural runoff) demonstrate the value of temperature data in an integrated flow model calibration. Land use and water use changes impact both the surface water and groundwater resources and can thus substantially change stream temperature dynamics. Local scale factors such as stream vegetation and geomorphology also play an important role in determining stream temperature. Thus, a combination of restoration strategies must be evaluated to find the optimal thermal conditions. Fish optimal growth and sustainability is dependent on a specific range of temperatures, but is also affected by seasonal variability, which should be taken into account when evaluating restoration altern

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Page publiée le 9 octobre 2012, mise à jour le 17 juillet 2017