H/H and Pollutant Loading Modeling
developing watershed simulation tools for improved planning and design
EOR conducted a hydrologic/hydraulic (H/H) and pollutant loading study of the entire Minnehaha Creek watershed. This extensive watershed covers 180 square miles and includes area within 2 counties, 3 townships, and 27 cities. Included in the study was the detailed H/H modeling of 6 natural streams, 22 miles of Minnehaha Creek, and the 8-square-mile Lake Minnetonka along with its many tributaries.
In order to construct the system models, the Minnehaha Creek watershed was divided into 453 subwatersheds, and approximately 2,000 nodes and links were generated to characterize the drainage network. The H/H model was constructed in XP - SWMM, and the water quality and in-lake modeling was conducted with PLOAD and WiLMS. Also taken into account in the study were calculations of the significant groundwater contributions identified and evaluated along Minnehaha Creek.
Major components of the study:
- participated in 72 separate meetings with regional teams and resource groups
- identified more than 90 stakeholders and facilitated their input on management strategies
- documented the physical and biological characteristics of the watershed
- quantified the amount of water moving through the watershed (flow rates and volumes)
- performed water quality calculations for in-stream flows as well as lakes and ponds
- formalized management programs on a subwatershed basis
- predicted peak discharges and flood elevations for existing and 2020 developed conditions for a variety of precipitation events
- calculated phosphorus and total suspended solids (TSS) for existing and 2020 developed conditions
- completed phosphorus response models of all major lakes in the watershed for existing and 2020 developed conditions
This hallmark study demonstrates how decision makers can use detailed watershed modeling to understand how systems will respond to proposed actions, and thereby to be more informed when making critical design decisions during project development. For example, the combined use of the H/H and pollutant loading models developed for this study was pivotal to the design of future wetland restoration projects along Minnehaha Creek.