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What is a Watershed?

We all live in one! The land area that drains or “sheds” to a low point in the landscape such as to a river, lake or wetland is a watershed. There are different classifications of watersheds from basins to subwatersheds. Think about where the rainfall goes in a yard after it rains. It drains to the street, into a storm drain and into a local stream or lake. This, on the smallest scale, is one form of watershed. The quality of water draining off your land directly impacts your local stream and lake quality.

There are many land use activities that impact water quality in watersheds. One of them is directly tied to the amount of impervious surface in a watershed. Urban areas have surfaces that don’t absorb water, such as roads, streets, rooftops, parking lots, and even compacted soil. Studies indicate that as the amount of impervious surface increases in urban areas the poorer the stream quality. 

Watershed Challenges

In all watersheds there are upstream and downstream land owners as water passes through many jurisdicational boundaries – this diversity of land use and ownership can be a challenge when coordinating efforts to improve and protect water and soil quality and reduce flooding impacts on a watershed level. Working on a watershed level starts with stakeholders working together to create consistent land use plans and policy and employing practices to prevent water pollution, reduce stormwater runoff, and minimize flooding downstream.

Watershed Midwest Watersheds
Source: Polk SWCD
Watershed Iowa Watersheds
Source: Polk SWCD

“Plan Your Work, Work Your Plan”

Environmental concerns, such as nonpoint source pollution, often cut across political jurisdictions. Consequently, environmental mitigation and protection require a comprehensive and collaborative, partnership approach that works with a multitude of programs, departments and agencies.

A watershed approach provides a framework for coordinating and integrating the myriad of programs and resources. This approach directs the focus on water quality in a geographic area delineated by watersheds. Watershed planning takes the watershed approach to the next level – the creation of a plan to assess and address water and soil quality issues in each watershed.

These locally-led plans provide important information to citizens about point and nonpoint sources of pollution that are impacting the water resources within a given watershed. Watershed planning is at the heart of successful water quality restoration and protection. There are many plans already developed that can be drawn from a watershed plan is being developed that are unique to each watershed, such as Comprehensive Land Use Plans, Hazard Mitigation Plans and Park and Recreation Plans.

There are many resources to guide the watershed planning process, most agencies offer their assistance at no cost. The State of Iowa has regional basin coordinators, Soil and Water Conservation Districts, and urban conservationists. Iowa Natural Resource Conservations Service Centers and non-govermental council of governments are also excellent watershed planning resources. Assistance may also be available at Iowa’s regent universities. The Iowa Flood Center and the Iowa Watershed Approach are programs at The University of Iowa. And Iowa State University has the Daily Erosion Project.

Watershed Assessment & Data Collection

The best starting point is to contact a Basin Coordinator. They are the experts in the state who can help get the process started. Then, gather and analyze existing primary and secondary data. Here are some common types of data:

  • GIS Maps of Land Use and Population Characteristics: land use; cropped areas; major forested areas; impervious cover; potential pollution sources (point source and non-point source) land that needs remediation (brownfields, grayfields); protected areas (conservation easements); existing structural and non-structural conservation practices; park and recreational areas, boating access points; historic and significant cultural sites; demographics – population, housing characteristics
  • Stormwater Ordinances: floodplain; erosion and sediment control; post construction stormwater management; illicit discharge detection and elimination
  • Other Policies: environmentally sensitive areas; stream buffer; ag. land protection; overlay zoning; or planned unit development zone
  • Local Plans: comprehensive land use plan; hazard mitigation plan; parks and recreation plan
  • Physical Resources: watershed boundaries; hydrology; water use designations; floodplains; topography; soils and erodibility indices
  • Natural Resources: habitat; threatened and endangered species – plants, fish and wildlife
  • Pollutant Sources: point sources; non-point sources
  • Waterbody Condition: water quality standards; 305(b) report; 303(d) report; TMDL reports; source water assessments; IOWATER data
  • Waterbody Monitoring Data: real-time data collection

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