Regions or areas bounded by drainage divides and occupied by drainage systems; specifically the tract of country that gathers water originating as precipitation and contributes it to a particular stream channel or system of channels, or to a lake, reservoir, or other body of water. [Glossary of Geology, 4th ed.]
Upcoming interagency study to assess status of ecological conditions, their relationships with contaminants and nutrients, anthropogenic factors affecting these, and develop models that may predict these ecological conditions.
Overview of project assessing water quality of the Tualatin River basin near Portland, Oregon with links to reports on chemical and nutrient levels and selected data on streamflow, water temperature, weather and precipitation.
The Sacramento-San Joaquin River Delta is the hub of California's water system and an important habitat for fish and wildlife. USGS research has provided resource managers and other stakeholders with a good understanding of how pesticides enter the Delta.