Submitted to: International Soil and Water Conservation Conference
Publication Type: Abstract Only
Publication Acceptance Date: 3/14/2011
Publication Date: N/A
Interpretive Summary: Abstract Only.
Technical Abstract: Nitrate (NO3-N) is a useful form of nitrogen because it is biologically available to plants and is therefore a valuable fertilizer. Excessive levels of NO3-N in drinking water can produce negative health impacts on humans and animals and can lead to excessive algal growth in water bodies. In order to determine the impacts of nitrates in streams and develop mitigation strategies at the watershed-scale, it is important to understand effects of many complex interactive factors within the landscape. The objective of this study is to identify spatial and temporal patterns in NO3-N concentrations and relate them to the climate, geographic, physiographic, and management effects within the Fort Cobb Reservoir watershed in southwestern Oklahoma. Water samples were collected bi-weekly from 2005-2009 at 15 sites and analyzed for nitrate. Ancillary data include: climate, topographic, soil, geologic, and land use data computed for each contributing area. Spatial autocorrelation will be evaluated using contiguity and upstream connectivity matrices. Regression trees will be developed for dry and wet phases with or without spatial autocorrelation based on recursive partitioning. Results of 1) NO3-N concentrations patterns across the 15 locations for four annual seasons during the dry and wet phases and 2) the relationships of NO3-N concentrations to climate and watershed characteristics during the two phases will be presented. Understanding the effects of prevailing climate conditions and the basic geophysical characteristics of the watershed on NO3-N will lead to accurate determination of the impacts of agricultural management and conservation effects on water quality at a watershed scale.