Simple solutions for Stormwater Management

Rainwater harvesting is the process of collecting rainwater and storing it for later use. Storage methods can range from small barrels to large underground storage tanks. 


The simplest way to start rainwater harvesting is to install a rain barrel next to a building that has downspouts collecting water from the roof. More elaborate rainwater storage systems can be installed underground in the interior of a structure connecting to a building’s water system. It is even possible for these larger systems to meet all non-potable and separate water uses, such as toilet flushing and laundry. 


Rainwater is a valuable resource that is underutilized in our communities. In the past, many homes were designed to have cisterns to capture and utilize rainfall for household purposes. Today, our rooftops and yards are designed to shed rainwater runoff into the stream, down the storm drain, and into streams, rather than absorbing or infiltrating it where it falls. This stormwater runoff picks up pollutants and impacts the water quality of our surface waters.


We commonly use drinking water for our lawns and gardens during the growing season when we could be using rainwater. Rainwater can be harvested for these uses which helps to conserve drinking water while also preventing runoff, and protecting water quality. 

Rain Barrels

Rain barrels are places in locations that can easily catch water such as at the end of a downspout. Using downspout adaptors or flexible elbows, rain barrels are places at the end of downspouts that are directed from the top of the barrel. Rain barrels will fill quickly and require an overflow drain for excess water to prevent damage. The overflow drain can be as simple as a garden hose installed at the top of the rain barrel to drain away excess water either away from the house or to another rain barrel. 


As stormwater reuse and water conservation become more widespread, the use of cisterns for non-potable water for commercial and industrial use is growing. Cisterns have great potential to be used as a secondary source of water for irrigation and gardening on corporate campuses or residential areas, while larger cisterns can be adapted to supplement non-potable water systems.

Cisterns can be placed above or below ground, or stored inside a heated area. Small cisterns can be as easy to install as a rain barrel, whereas larger systems will require design assistance and contractors. Before installing a cistern, it is important to observe local city and county regulations pertaining to indoor use of captured rainwater to prevent cross-contamination of drinking water. 


  • Make sure the top of the rain barrel has a screen where the downspout releases water to ensure mosquitos can’t access the water to minimize breeding. 
  • Install rain barrels on a level and sturdy foundation. At more than 8 pounds per gallon of water, a full 50 gallon rain barrel weighs over 400 pounds. 
  • Drain, leave the valve open, or redirect downspouts away from the system during the winter to prevent freeze damage.
  • Rainwater harvesting systems can be installed adjacent to rain gardens to provide maximum water filtering capabilities by overflowing into the rain garden once the usable storage is full. 
  • It only takes 60 square feet of rooftop to fill a 50 gallon rain barrel during an inch of rain
  • Divert overflow away from building foundations
Rain barrel capturing rainfall from homeowner's roof to be used for watering plants.
This natural looking water feature harvests rainfall from the home's rooftop, and reuses the water in the stream for other outdoor watering.
These structural blocks and plastic liner are used to store water underground. They are used as the reservoir below natural or landscaped water features, like show to the right.

What is your Water Collection Potential?


Make sure to account for both monthly changes in rainfall events and your usage of detained water to determine the size of containment unit needed at your location. The months with heavy rainfall are times that extra irrigation isn’t needed, so it’s important to determine your desired use. If you’d like to use rainwater to do your laundry, you would likely want a larger container than someone who only wanted to use their collected rainwater to water plants. 

Use the following equation to determine the potential yield in gallons of rainwater that can be harvested from an area generating runoff


Harvested Rainwater (in gallons) = 

Rooftop surface (sq. ft.) x avg. rainfall event (in.) * 0.623 

Polk Soil and Water Conservation District

1513 North Ankeny Blvd., Suite 3

Ankeny, IA, 50023

(515) 964 1883 ext. 3

Monday – Friday

7:30 am – 4:00 pm

Polk Soil and Water Conservation District is an Equal Opportunity Employer.

Receive the latest news

Subscribe To Our Quarterly Newsletter

Local stories directly to you