Rainwater Harvesting/Stormwater Reuse & Rain Barrel Programs

Development of rainwater harvesting and stormwater reuse concepts and programs

This image shows Wall garden to capture rooftop runoff
Wall garden to capture rooftop runoff Image Courtesy of Emmons & Olivier Resources, Inc.

High intensity land use patterns and increasing pressure on water resources require effective stormwater management solutions in tight spaces. Rainwater harvesting programs collect runoff from rooftops, parking lots and other surfaces and reuse the water for such things as irrigation of gardens and municipal ballparks, washing patio furniture and lawn watering. Additionally, harvested rainwater when approved could be used indoors for non-potable uses such as toilet and urinal flushing. Indoor use designs are subject to review by the Plumbing Plan Review Program of the MN Department of Labor and Industry in accordance with the MN Plumbing Code, Chapter 4715 and would require pretreatment practices including filtration and disinfection. The effect is volume control, reduced flooding and erosion, and less demand for treated potable water. This fact sheet discusses the benefits of rainwater harvesting, highlights existing programs and provides conceptual designs for a variety of effective rainwater harvesting systems.

Benefits / Pollution Reduction

Rainwater harvesting programs serve multiple benefits. The collected rainwater can be used for purposes that would otherwise require potable, tap water. This reduces the cost of tap water to the owner and conserves potable water resources. All of the water captured and subsequently infiltrated (e.g. used for irrigation) removes 100 percent of the solids, nutrients, metals, pathogens and toxins that would otherwise have washed off, drained to the storm sewer, and then reached downstream waterbodies.

Harvesting and re-using rainwater decreases the impact of stormwater runoff to our lakes and streams; it protects the environment and minimizes localized flooding and erosion. It has additional benefits in urban areas, including, but not limited to, an increase in soil moisture levels for urban greenery. In addition, it can be used to meet regulatory requirements for stormwater volume control and water quality.

Program Development & Implementation

Programs designed to promote rainwater harvesting and reuse can incorporate any combination of the elements below.

Rain Barrels

Rainwater harvesting can be accomplished using rain barrels and/or cisterns. Rain barrels are typically small scale (25-100 gallons) and located at the downspout of a gutter system. They can also be linked to expand the overall storage volume (right). They are used to collect and store rainwater for watering landscapes and gardens or washing patio furniture. The simplest method of delivering water is by the force of gravity. However, more complex systems can be designed to deliver the water from multiple barrels connected in a series with pumps and flow control devices.

The total volume of storage available from rain barrels represents roof runoff from relatively small rainfall events, typically substantially less than one inch of rain over the surface. This is a small volume for a single rain barrel, but cumulative effects of rain barrels installed across a watershed include volume reduction and water quality treatment since typically the first half to one-inch of runoff contains the dirtiest water. During wet weather, there will likely be little or no storage available because of prior filling and little demand for irrigation water. If the ground can absorb it, consider discharging collected water onto vegetated areas between rainfall events to maximize rainwater capture and infiltration even if unnecessary for irrigation.


This image shows an installed rain barel
Installed rain barel Image Courtesy of Emmons & Olivier Resources, Inc.

Rain barrel design, installation and operation guidance The following general guidance provides an overview of the items to consider in rain barrel design, installation and operation. Specific design guidance for installation and construction can be found in many of the resources in the Additional Resources section.

  • The system should be watertight, have a smooth interior surface, be located on level and stable ground, have a tight-fitting lid, durable screens on the inlet and outlet and have an emergency overflow device
  • Barrel material should withstand the pressure of water over long periods of time
  • The barrel should include an overflow deflection and routing feature to keep water away from the foundation of your home
  • Rain barrels should not be used for the following roof types: tar and gravel, asbestos shingle and treated cedar shakes because of the high potential for polluting the captured water
  • To prevent the breeding of mosquitoes, water in the rain barrel should be emptied in less than five days or enclosed with a fine screen over all openings
  • Rain barrels and cisterns should be disconnected and drained in the winter to prevent freezing and deformation of the rain water harvesting system. When emptied, they can be reconnected to collect spring meltwater.

Regional rain barrel programs and initiatives The utilities of Austin, Rochester and Owatonna, MN, teamed up to offer a 💲10 rebate to water customers for rain barrel purchases of over 40 gallons in volume. Martin County SWCD in Fairmont, MN, coordinated with Hormel Foods Corporation to salvage their 55 gallon food-grade drums to recycle for use in its Rain Barrel Program. St. Croix County, Wisconsin, runs a program retrofitting food-grade barrels into rain barrels and selling them for 💲30. Many cities provide a limited supply of rain barrels to residents at a reduced cost.

In the past, Nine Mile Creek Watershed District has sponsored a Rain Barrel Decorating Event with optional art competition in Bloomington and Hopkins, MN, for residents living in the District. The District supplied rain barrels at discounted price and free painting supplies for decorating the barrels onsite.

In 2007, the City of Minneapolis supplied 2,000 rain barrels to residents at the reduced cost of 💲45. The barrels were available through a 💲100,000 grant from the Environmental Protection Agency and in partnership with Minneapolis/Metro Blooms and the Green Institute. Monitoring was conducted by the City of Minneapolis to determine the volume control and water quality benefits of rain barrels (Neighborhood Rain Barrel Partnership Project, 2008). Data indicated that the average 50-gallon rain barrel could capture a 0.26-inch precipitation event, or 64 percent of the 28 precipitation events monitored. Additional benefits could be realized by increasing available storage to limit overflow (e.g. plumbing barrels in series).

Cisterns

Cisterns have a greater storage capacity than rain barrels and may be located above or below ground. Due to their size and storage capacity, these systems (often large polyethylene drums) typically collect runoff from areas larger than residential rooftops such as commercial parking lots.

Collected water is typically used to irrigate landscapes, gardens, and ballparks on a regular basis (e.g. feeding an automated irrigation system) reducing the strain on municipal water supplies during peak summer months. Again, cisterns may be used in series and water is typically delivered using a pump system. Pump systems in cisterns can be designed with a floating level that shuts off the pump and converts the water source to a municipal supply when cistern levels are too low.

St. Anthony Village, MN, constructed an underground cistern that collects stormwater runoff from adjacent roadways and filters backwash from the adjacent water treatment plant for reuse. The cistern is designed to hold 500,000 gallons of water which is used to water the adjacent City Park and City Hall. A surface stormwater pond can also overflow to the cistern and be used for irrigation. The 💲1.5 million project was designed and

St. Anthony Village, MN, constructed an underground cistern that collects stormwater runoff from adjacent roadways and filters backwash from the adjacent water treatment plant for reuse. The cistern is designed to hold 500,000 gallons of water which is used to water the adjacent City Park and City Hall. A surface stormwater pond can also overflow to the cistern and be used for irrigation. The $1.5 million project was designed and installed in conjunction with an adjacent road project making connection to storm sewer easier; the cistern overflows to storm sewer when full.

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