Integrated hydrologic modeling of the Malibu Creek Watershed

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Hydrologic modeling; Malibu Creek watershed; Runoff; Soil Conservation Service model (SCS-WB); TOPMODEL


Environmental Indicators and Impact Assessment | Environmental Monitoring | Environmental Sciences | Fresh Water Studies


This study presents two hydrologic models used to assess flow regimes in the Malibu Creek watershed that are changed due to land use, climate variability, wildland fires, and other anthropogenic impacts. The two models chosen--TOPMODEL and the Soil Conservation Service's SCS-WB model--have the capability to produce simulations on varying spatial and temporal scales. TOPMODEL is a physically-based semi-distributed model that uses topography, soil types, and contributing drainage areas to calculate the runoff from the watershed. The SCS-WB model is a water budget-linked distributed model that uses surface slope, soil type, and antecedent precipitation to partition precipitation into direct overland runoff and effective precipitation. Infiltration is partitioned into evapotranspiration, through-flow, and groundwater recharge based on soil conditions. Both models are calibrated at a daily time scale for the period 1981-1989 and verified on the period 1991-1997. The required input data is precipitation, streamflow, temperature, estimated evapotranspiration, topography, land uses, and various soil characteristics. A 30-meter Digital Elevation Model (DEM) is used and the soil characteristics (e.g., water holding capacity, average permeability, effective depth) are obtained from a detailed soil survey of the Malibu area by the Soil Conservation Service. Once the models are properly calibrated and verified, comparisons will be made to assess the ability of the models to model streamflow accurately at different time scales (e.g., hourly, daily, monthly). Then, the appropriate hydrologic model will be used to assess the changes in flow regimes due to wildland fires in the watershed (both historical and hypothetical) and different climate scenarios (e.g., El Nino events). Future activities will link mesoscale atmospheric models, and the predicted precipitation fields, with the hydrologic model. Finally, the hydrologic models will be coupled with other components (e.g., water quality, wetland ecology, and coastal ocean circulation models) of this interdisciplinary project.


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