Long-term temporal variation of nitrate concentration-stream discharge (C-Q) relationship for an agrcultural watershed in Midwest USA

Abstract

Nutrients export from agricultural watersheds have long been recognized as a critical cause of eutrophication in receiving surface water bodies. Since 1970s, many changes have occurred in intensively managed, agricultural watersheds in U.S., including increased weather extremes, enhanced artificial drainage, timing and rate of fertilizer applications, and implementation of conservation tillage practices. Nutrient concentration – discharge relationship (C-Q relationship) can identify periods and locations influencing the change in nutrient export in stream discharge, which could help infer the relationship between observed changes in nutrient export to factors that cause these changes. We hypothesize that the long-term pattern of C-Q relationship would change in response to changes in climate, land use, and management practices that happened over the past 40 years. To test the hypothesis, we analyzed the long-term variation of nitrate C-Q relationship in an agricultural watershed in Ohio across different time scales, using a dataset of relatively high-frequency measurements of stream flow and nitrate concentrations. Further details are avaialble in the [PDF] file.