A watershed is a land area that drains rainfall runoff (or stormwater) to a single outlet, or “discharge point.” The discharge point can be a lake, river, ditch, or storm sewer pipe discharge or outfall. The City of Madison is divided into 22 major watersheds.

Watershed Study

A watershed study is an analysis of a watershed. Individual studies might focus on water pollution, aquatic life, flooding, or other issues impacting that watershed. The City watershed studies focus on chronic flooding, which we investigate by using computer models that are created to estimate rainfall/runoff and routing of stormwater. The study will analyze where and why flooding occurs and then evaluate possible solutions.


Rainwater produced from a rain event.

Stormwater Runoff

The portion of the rainwater that does not soak into the ground.

Stormwater Conveyance System

The system of underground pipes and open channels designed to convey stormwater runoff.

Stormwater Inlets

Grates in the ground that take in stormwater runoff; connected to the stormwater conveyance system.

Detention Ponds

Ponds designed to hold stormwater runoff to improve water quality and/or help prevent flooding.


Computer software that is used to evaluate the stormwater conveyance system,

Local Storm Sewer Projects

Storm sewer that is reconstructed with another already-scheduled project – typically street reconstruction.

Stand-alone Projects

Flood mitigation projects that will be constructed on their own – not tied to another already-scheduled project.