Submitted to: Soil and Water Conservation Society
Publication Type: Abstract only
Publication Acceptance Date: 10/15/2008
Publication Date: 10/20/2008
Citation: Garbrecht, J.D. 2008. Multiyear precipitation variations and runoff response in a mixed agricultural grassland watershed in central Oklahoma [abstract]. Soil and Water Conservation Society, Farming with Grass Conference, October 20-22, 2008, Oklahoma City, Oklahoma. Available: http://www.swcs.org.en.conferences/farming_with_grass/farming_with_grass_poster_presentations/ Interpretive Summary: Abstract only.
Technical Abstract: Climate varies seasonally, from year to year, and also from decade to decade and over longer periods of time. One key climate variable that has great impact on land productivity, runoff, soil erosion and water quality is precipitation. Precipitation drives soil moisture, evapotranspiration, biomass production, and surface runoff. Surface runoff, in turn, erodes and transports soils, nutrients and agricultural chemicals into downstream water bodies used for water supply, recreation and wildlife habitat. When precipitation varies, so does the water budget, surface runoff and associated erosion and transport of soils, nutrients and agrochemicals. Seasonal and year-to-year variations in precipitation are common and impacts on water resources and land productivity are well understood. However, variations in average annual precipitation lasting 5 to 15 years, termed multiyear variations or wet and dry periods, are only being recognized recently for their practical implications, as they have the potential to surpass the impacts of short-term annual variations due to the cumulative effects of sustained departure from average conditions. In this study, multiyear variations in the 1895-2007 annual precipitation record in central Oklahoma are reviewed, and the impact on watershed runoff response is illustrated for the Fort Cobb reservoir watershed in the Upper Washita River Basin, Oklahoma. Between 1940 and 2007, four dry periods and one extended wet period and corresponding high and low runoff periods were identified. Evaluation of annual precipitation and runoff data showed that in central Oklahoma watershed runoff responds sensitively to multiyear precipitation variations. The relative increase in watershed runoff between wet and dry periods was disproportionately larger than the corresponding increase in precipitation. Implications for water resources management, land productivity, erosion and sediment yield are discussed.