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Headwater influences on downstream water quality
Walter K Dodds1, Robert M Oakes
1Kansas State University, Manhattan, KS 66506, USA. wkdodds@ksu.edu
Environmental Management
|November 14, 2007
Summary
Land use in small headwater streams significantly impacts downstream water quality, affecting nitrogen and phosphorus levels. Protecting only downstream riparian zones is insufficient for effective water quality management.
Area of Science:
- Environmental Science
- Hydrology
- Ecology
Background:
- Land use significantly influences surface water chemistry.
- Understanding these relationships across different stream sizes is crucial for water quality management.
- Regional variations in land use impacts on water quality need assessment.
Purpose of the Study:
- To investigate how riparian and whole watershed land use affect surface water chemistry.
- To assess the influence of stream size on these land use-water chemistry relationships.
- To evaluate regional variations in these ecological connections.
Main Methods:
- Selected 68 watersheds across four U.S. EPA ecoregions in eastern Kansas.
- Quantified riparian land cover and watershed land use by Strahler order.
- Employed multiple regression analyses to link land use variables to water chemistry.
Main Results:
- Riparian land cover explained significant variation in total nitrogen (41%), nitrate (61%), and total phosphorus (63%).
- Water chemistry in downstream reaches correlated most strongly with land use in the entire watershed or riparian zones of small, first-order streams.
- Headwater stream influences were detected even when not flowing, and relationships were consistent across ecoregions.
Conclusions:
- Land use characteristics are primary drivers of water quality variation among watersheds.
- Nonpoint pollution control strategies must account for the impact of small upland streams.
- Solely protecting downstream riparian zones is inadequate for safeguarding water quality.
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