Legacy phosphorus and climate change: how the past and future matter for lake water quality
Abstract
Phosphorus (P) is an essential nutrient for crops, yet overabundance in freshwater bodies causes eutrophication. While many agricultural watersheds in the Midwest U.S. are focused on alternative management practices to improve water quality, such practices have yet to show substantial improvements downstream. It is recognized that built-up supplies of P in soils and sediments, ie legacy P, provides a long-term, diffuse supply to water bodies that is difficult to control. Focusing on a dairy-rich watershed in southern Wisconsin, USA, we examined the effects of soil P overabundance on lake water quality, and the implications for P overabundance under future climate and land use scenarios. Using process-based models, we found a significant relationship between watershed soil P supply and lake water quality indicators. Results also revealed a synergistic relationship between rainfall intensity and manure P supply in affecting dissolved P loss from manure, suggesting that increasingly strong storms expected with climate change are likely to exacerbate P loss from the landscape in livestock-rich regions. Finally, we compared the effects of land use/land management and climate under long-term, future scenarios. We found that climate was the more important driver in water quality outcomes, yet land use/management had a significant and consistent effect over decadal timescales. The scenario analysis revealed that drawing down legacy P was the most important aspect of land management affecting long term water quality, superseding erosion risk. In conclusion, overabundance of P in soils and sediments is a critical driver of freshwater quality, the effects of which may be exacerbated by increases in precipitation and rainfall intensity. Management practices that remove excess P from manures and soils address the root of the problem, and may be more effective than erosion control measures in reducing diffuse P pollution in a changing climate.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H23A..01M
- Keywords:
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- 1803 Anthropogenic effects;
- HYDROLOGY;
- 1831 Groundwater quality;
- HYDROLOGY;
- 1834 Human impacts;
- HYDROLOGY;
- 1871 Surface water quality;
- HYDROLOGY