ARS | Publication request: WATERSHED VULNERABILITY TO LOSSES OF AGRICULTURAL CHEMICALS: THE INTERPLAY OF CHEMISTRY, HYDROLOGY, AND LAND-USE

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 7, 1999
Publication Date: N/A

Technical Abstract: The objectives of this study were to conduct a multi-scale, multi-basin reconnaissance survey of northern Missouri streams to determine the relative importance of land-use and hydrology to agricultural chemical contamination of streams in northern Missouri. In 1994 and 1995, samples were collected from 140 sites on 95 different streams and rivers representing about 52,000 km**2 throughout northern Missouri and southern Iowa with a diversity in soils, hydrology, and land-use. Samples were collected under pre- and post-plant conditions and analyzed for common herbicides and dissolved nutrients. Atrazine, cyanazine, and metolachlor were the most frequently detected herbicides. Atrazine was detected in at least 90% of pre-plant samples and 100% of post-plant samples. Nutrient and herbicide concentrations showed opposite trends across the study region. Streams draining watersheds with runoff-prone soils had the highest herbicide concentrations, while streams draining watersheds with well drained soils had the highest nitrate concentrations. Current data are sufficient to develop a conceptual framework for assessing watershed vulnerability based on three key factors: 1) compound chemistry; 2) hydrology; and 3) land-use.