Grantee Research Project Results

Land Use, Hydrological Processes, and Applications of a Distributed Hydrological Model for Water Quality Concerns

EPA Grant Number: F07B81071
Title: Land Use, Hydrological Processes, and Applications of a Distributed Hydrological Model for Water Quality Concerns
Investigators: Toohey, Ryan C.
Institution: University of Idaho
EPA Project Officer: Hahn, Intaek
Project Period: August 1, 2007 through August 1, 2008
RFA: GRO Fellowships for Graduate Environmental Study (2007) RFA Text |  Recipients Lists
Research Category: Fellowship - Hydrology , Watersheds , Academic Fellowships

Objective:

Hydrological processes profoundly affect human health and the quality of the environment. Hydrological processes also determine how non-point source pollution reaches rivers and groundwater. Land uses often differ in soil characteristics and evapotranspiration regimes, which influences the hydrological response of a watershed. Since water quality models depend on hydrological models, the influence of land use on hydrological processes needs to be explored. Also, with distributed hydrological models, hydrology and contaminant sources can be evaluated in a new spatial context. However, even in the United States, water quality models often do not utilize the most recent hydrological knowledge.

Therefore in the proposed project, I will address the following environmental problems: 1) How does land use affect runoff response at the field scale?, 2) How does land use change affect runoff response at the watershed scale?, 3) How can we use a distributed model to identify critical management areas for agrichemical pollution and erosion?

Approach:

In this project, we examine hydrological processes at three scales: 1) the field scale (1-5 ha), 2) the watershed scale (250 km²), and 3) the regional scale (2500 km²). At the field scale, I compare several different types of land use in terms of soil properties, soil moisture dynamics, and runoff response. I will use the Soil Moisture Routing model to test conceptual models based on field data and observations. At the watershed scale, I will perform long-term trend analysis on rainfall and river discharge, and modeling investigations to determine whether land use change over time (≈ 35 years) impacts daily, seasonal and annual river discharges. Finally, at the regional scale, I will combine the Soil Moisture Routing model with land use maps, soil maps, and a detailed agricultural database to investigate critical source areas in terms of water quality and erosion potential.

Expected Results:

I expect to find that even in high rainfall intensity / deep soil land types, such as Costa Rica, saturation-excess runoff is a dominant runoff process. This has tremendously important implications for water quality models where this mechanism dictates longer contact of the water with soil. However, differences in soil properties, soil moisture dynamics, and runoff response among the land uses may elucidate potential modifications of this subsurface process. Also, I expect to see over time that land use does indeed change river discharges and the spatial extent of saturated areas. Finally at the regional scale, I expect that the SMR model will simulate observed river discharge and saturated areas providing a powerful tool to investigate risks to water quality.

Supplemental Keywords:

Hydrology, distributed hydrological models, the SMR model, land use, critical source areas, water quality, Costa Rica,, Scientific Discipline

Progress and Final Reports:

Final