Watershed Basics

Western Lake Erie Basin and associated watersheds (Credit: Western Lake Erie Basin Partnership)


The geographic focus of the Tri-State Watershed Alliance (TSWA) is the St. Joseph, St. Marys, and Upper Maumee watersheds that are part of the larger Western Lake Erie Basin.

What is a watershed? 

A watershed is an area of land that drains all the streams and rainfall to a common outlet such as the outflow of a reservoir, mouth of a bay, or any point along a stream channel. Scientists use a Hydrologic Unit Code to identify each hydrologic unit. The number of digits assigned to an area of land varies depending on whether it is being used to identify a large watershed, such as the Great Lakes Basin, or a smaller watershed such as the St. Marys River watershed.

Watershed Management Plan

A watershed management plan (WMP) helps to define and guide a strategy for achieving water resource goals for a geographically defined watershed.

Credit: HowStuffWorks

WMPs have been developed for various watersheds in the focus area of the Tri-State Watershed Alliance:

Upper Maumee River Watershed
Upper St. Joseph River Watershed

Middle St. Joseph River Watershed
Lower St. Joseph River-Bear Creek Watershed 
St. Marys River Watershed

What watershed are you in?

The following online tools can help you find
what watershed you are in:

Indiana State Department of Agriculture 
EPA “Surf Your Watershed”
USGS “Science In Your Watershed”


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