St. Charles Watersheds Alliance

Improving St. Charles County Watersheds

Stormwater planning, habitat conservation and healthy ecosystems for every community in St. Charles County.

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See it in person

Explore watershed places in St. Charles County

Wetlands, conservation areas, a creek water trail and neighborhood stormwater projects you can visit, on one map with three self-guided tours.

Flooded bottomland forest wetland with green spring growth Tree-lined street with planted stormwater beds along the sidewalk
About Us

Proactive stormwater management for all of St. Charles County

The St. Charles Watersheds Alliance (SCWA) is a non-profit organization dedicated to advocating for proactive stormwater runoff management and habitat conservation in all of St. Charles County and its municipalities.

SCWA seeks to promote diligent stormwater planning and Low Impact Development green infrastructure techniques, and provide resources for stormwater education, planning, and construction. We encourage native planting and habitat restoration to enhance community resilience to stormwater impacts and improve water quality, and we promote resource sharing and collaborative networks with other organizations, businesses, and government entities.

Our goal is to create a sustainable and healthy ecosystem for all.

What we're working on

Watershed-scale thinking for a growing county

Streams, floodplains, prairies and wetlands don't stop at property lines. SCWA works at the scale of the whole watershed.

Volunteers checking a small rocky creek lined with native plants beside a neighborhood street
Communities

Working together for healthier watersheds

We work alongside residents, HOAs, developers, municipalities and businesses toward healthier, more resilient neighborhoods, through practical guidance, outreach and education, and locally driven research on St. Charles County’s streams and watersheds.

Concept rendering: the same neighborhood and creek before, with storm runoff flooding streets and eroding the creek, and after, with trees, planted creek buffers and clear waterBeforeAfterConcept rendering
Community perspective

Growth that works with the land

When a proposed project draws strong public interest, we can offer a neutral community perspective that complements city review: a practical look at effects on streams, habitat and stormwater, and sensible solutions residents and developers can support.

Retention pond with native plantings
With MidAmerica Watershed.Org

Certification & free resources

In partnership with MidAmerica Watershed.Org, we support green infrastructure certification and free planning tools, standards and GIS resources.

See the free resources →
Why it matters

Where rainfall goes, by land cover

On natural ground, most rain soaks into the soil or returns to the air through plants. As land is paved, that rain runs off instead, carrying pollutants, eroding stream banks and adding to flooding downstream.

On heavily paved land, runoff jumps from 10% to 55% of rainfall. Connected green infrastructure, like rain gardens, stream buffers, green streets and restored floodplains, helps St. Charles County watersheds get that water back into the ground.

  • Runoff
  • Shallow infiltration
  • Deep infiltration
  • Evapotranspiration
0%25%50%75%100%Natural cover: Runoff 10%10%Natural cover: Shallow infiltration 25%25%Natural cover: Deep infiltration 25%25%Natural cover: Evapotranspiration 40%40%Natural cover10–20% paved: Runoff 20%20%10–20% paved: Shallow infiltration 21%21%10–20% paved: Deep infiltration 21%21%10–20% paved: Evapotranspiration 38%38%10–20% paved35–50% paved: Runoff 30%30%35–50% paved: Shallow infiltration 20%20%35–50% paved: Deep infiltration 15%15%35–50% paved: Evapotranspiration 35%35%35–50% paved75–100% paved: Runoff 55%55%75–100% paved: Shallow infiltration 10%10%75–100% paved: Deep infiltration 5%75–100% paved: Evapotranspiration 30%30%75–100% paved
Share of annual rainfall. Data: Arnold & Gibbons (1996), as published by U.S. EPA and FHWA.
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