Stormwater Harvesting and Reuse Study

Putting Stormwater to Good Use: Calculating the Benefits of Stormwater Harvesting and Reuse

City:

Subwatershed:

Project Status: 
Completed
Year Completed: 
2013
About this project: 

Overview
Stormwater is usually viewed as a burden to be managed but it also can be a great resource. The pollutants found in stormwater -- phosphorus and nitrogen -- are the same chemicals that grass, plants and trees need to thrive.  

By using stormwater instead of drinking water for tasks like watering the lawn or putting out fires, we can conserve resources and reduce the amount of polluted stormwater that enters our lakes, rivers and streams. 

A rainwater cistern collecting water from a roof and irrigating a field with rainwater

Purpose of the Study

  • Address the lack of technical guidance for harvesting and reusing stormwater, especially in the Midwest
  • Create a tool for measuring the specific water quality benefits of harvesting projects -- reduction of runoff volume and phosphorus load
  • Help communities understand the challenges of harvesting and reuse
  • Evaluate potential sites for harvesting and reuse within the metro area
  • Funded by the Mississippi Watershed Management Organization and Minnehaha Creek Watershed District

Key Findings

  • Harvesting benefits and reusesHarvesting and reuse are more effective at reducing volume, per square foot, than typical trenches and basins
  • Harvesting is also advantageous in areas where soil issues prevent safe infiltration
  • The outputs of the calculator spreadsheet help manage overflow, determine proper sizing, and inform irrigation decisions
  • Existing ponds can be retrofitted for harvesting and reuse
  • While the lack of adequate green space is a limiting factor in developed areas, the lack of runoff is a limiting factor in areas that are undeveloped

About the Calculator

  • Available for free here
  • Spreadsheet-based model
  • Simultaneously calculates annual volume reduction and phosphorus removal as a percentage of the annual watershed load
  • Helps quantify benefits of reuse as a Best Management Practice (BMP), and could be used for determining if a site meets rule requirements

Inputs and Outputs Graphs and Tables

Presentation from Emmons & Olivier Resources, Inc. on the study: