|Van Liew, Michael|
Submitted to: ASAE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: July 1, 2003
Publication Date: July 27, 2003
Citation: VAN LIEW, M.W. THE IMPACT OF CHANGES IN LAND USE ON THE AVAILABILITY OF WATER FROM AGRICULTURAL WATERSHEDS UNDER DRY, AVERAGE, AND WET CLIMATIC CONDITIONS. CD-ROM. LAS VEGAS, NV: AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS. 2003. Technical Abstract: In recent years competing demands for water coupled with population growth have placed considerable pressure upon the efficient management of available water resources in the Southern Great Plains (SGP). Implementation of a change in land cover represents one method that could be utilized to enhance the availability of water for meeting future projected needs. Because the nature and scale of hydrologic impacts depend on the form of the land cover change and its climatic context, further studies are needed to determine how potential changes in land cover affect both water quantity and quality for watersheds in the SGP. The objective of this study was to determine the variations in streamflow associated with various hypothetical changes in land cover. The Soil and Water Assessment Tool (SWAT) was utilized to conduct the study on subwatershed 442, located on the Little Washita River Experimental Watershed in Southwestern Oklahoma, under various climatic conditions. SWAT was first calibrated on the subwatershed, and four scenarios were then simulated to compare the impact of changes in land cover on hydrologic response under dry, average, and wet climatic conditions. These scenarios included land covers on the watershed that were entirely 1) dense brush (average canopy cover greater than 30%), 2) moderate brush (average canopy cover from 10% to 30%), 3) grassland, or 4) winter wheat. Simulation results show that a change in land cover from dense brush to grassland leads to increases in streamflow of 146%, 111%, and 54% under dry, average, and wet climatic conditions, respectively. Results of this study demonstrate that certain changes in land cover in the SGP, such as a change from brush to grassland, hold promise for enhancing the availability of streamflow to meet projected future water resources needs. However, changes in the relative contributions of surface and subsurface flow to total streamflow must also be considered in the selection of appropriate land cover changes that may be envisioned for improving water yield, since these changes may significantly impact the potential for flooding and the movement of sediment, nutrients, and pesticides on the watershed.