Memory and Management: Competing Controls on Long-Term Nitrate Trajectories in U.S. Rivers
Abstract
Excess nitrogen from intensive agricultural production, atmospheric N deposition, and urban point sources elevates stream nitrate concentrations, leading to problems of eutrophication and ecosystem degradation in coastal waters. A major emphasis of current US-scale analysis of water quality is to better our understanding of the relationship between changes in anthropogenic N inputs within watersheds and subsequent changes in riverine N loads. While most water quality modeling assumes a positive linear correlation between watershed N inputs and riverine N, many efforts to reduce riverine N through improved nutrient management practices result in no measurable improvements in water quality. Here, we use nitrate concentration and load data from more than 400 US watersheds, along with developed N input trajectories for these watersheds, to quantify time-varying relationships between N inputs and riverine N export. Our results show substantial variations in watershed N import-export relationships over time, with quantifiable hysteresis effects. Additionally, we see clear relationships between input-export trajectories and watershed land use and management. The empirical analysis in this study is bolstered by modeled simulations to reproduce and further explain drivers behind the hysteretic relationships commonly observed in the monitored watersheds.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H12G..06V