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Dynamics of diffuse pollution from US southern watersheds
J D Schreiber1, R A Rebich, C M Cooper
1USDA-ARS-National Sedimentation Laboratory, Oxford, MS 38655, USA.
Water Research
|June 8, 2001
Summary
Understanding diffuse pollution is key for effective water quality management. Conventional tillage farming significantly increases sediment and nutrient runoff compared to no-till or forested areas, impacting stream health.
Area of Science:
- Environmental Science
- Water Quality Management
- Agricultural Hydrology
Background:
- Diffuse pollution significantly impacts water bodies, necessitating a comprehensive understanding of pollutant sources, transport dynamics, and event characteristics.
- Agricultural practices, particularly tillage methods, are major contributors to sediment and nutrient loads in waterways.
Purpose of the Study:
- To investigate the effects of diffuse pollution, focusing on pollutant sources, transport quantities, and the impact of transient pollution events.
- To inform the design of effective Best Management Practices (BMPs) for remediating diffuse pollution and mitigating its ecological effects.
Main Methods:
- Comparative analysis of sediment and nutrient loads from different land uses (conventional-till, no-till soybean watersheds, and forested areas) in the Yazoo Basin, Mississippi.
- Evaluation of pollutant transport during transient pollution events, such as storm events.
Main Results:
- Conventional-till soybean watersheds exhibited significantly higher sediment loads (19,000 kg/ha/yr) and nutrient transport (77-96% of P and N) compared to no-till watersheds (500 kg/ha/yr, 31% nutrient transport).
- Forested areas had low sediment loads (200 kg/ha/yr) but contributed substantially to nutrient transport (47-76% of P and N).
- Transient pollution events, like storms, can transport nearly the annual load of sediment, nutrients, and pesticides.
Conclusions:
- Tillage practices profoundly influence sediment and nutrient export, highlighting the importance of agricultural management in water quality.
- Best Management Practices (BMPs) must address both diffuse pollution sources and the episodic nature of pollutant transport to protect stream and reservoir ecosystems.