Lake Springfield Watershed Management Plan

Synopsis

Lake Springfield is well over 3,000 acres in size and managed by City Water, Light and Power. It is the largest municipally-owned lake in Illinois. The Lake serves as the public water supply for approximately 165,000 customers, provides the cooling water source for Springfield’s power plant condenser, and is a major recreational area with over 600,000 visits annually. Northwater was retained as a sub-consultant to develop technical aspects of a watershed plan, including advanced modeling and the identification of specific practices needed to address declining water quality resulting from nitrogen, phosphorus, and sediment.

Client(s):

Sangamon County Soil & Water Conservation District
Completion Date:

2016
Services:

Water Resources, Water Supply
Market/Sector:

Agriculture, Government
Location:

Sangamon, Morgan, and Macoupin Counties, Illinois

Project Description

Northwater was retained as a sub-consultant responsible for all technical aspects of the Lake Springfield Watershed Management Plan. Lake Springfield is the largest municipally-owned lake in Illinois and is a source of drinking water, a recreation resource, and essential to the city’s power generation.

Technical roles included a detailed watershed characterization and advanced GIS spatial analysis and mapping, identifying watershed Best Management Practices (BMPs), public participation, and a custom watershed pollution load model.

The custom pollution load model (SWAMM) was built to quantify and locate sediment, nitrogen, and phosphorus loading to the lake. It was calibrated to existing water quality and stream flow data and resulted in spatially explicit loading by land/parcel unit. Model development and attributes also included: a custom GIS landuse layer, loading from drain tiles, tillage, and existing treatment practices, such as detention basins or filter strips. SWAMM was used to quantify load reductions from watershed treatment practices and identify “hot spots.”

SWAMM was incorporated into a secure online interface allowing managers to view and query map layers and hydrology, navigate the watershed, view and query areas of high sediment and nutrient loading, watershed plan recommendations, and expected pollutant reductions, place custom BMPs and calculate their load reductions, and track progress through a management dashboard.