Green Infrastructure: Rainwater Harvesting 

From an at-home rain barrel to a large commercial cistern, rainwater harvesting is a form of green infrastructure that conserves water.

Freshwater is one of our most precious resources. Rainwater harvesting allows homeowners and businesses to collect and store rainfall to up their sustainability and reduce their water bills.  

Rainwater harvesting is one form of green infrastructure that can help our neighborhoods be more resilient to stormwater issues. If you missed it or need a refresher, read our first blog post in the green infrastructure series to learn more about what green infrastructure is and how it can help solve stormwater problems in our community. 

Capturing Rain to Use at Home 

Stormwater is a major issue in many of our neighborhoods. Because roads, parking lots, and buildings cover the suburban landscape, there are not many places where rain can soak into the ground. When rain can’t go into the soil, it travels across the landscape and becomes stormwater runoff, leading to flooding and contamination of local streams.  

Rainwater harvesting collects and stores rain where it falls, therefore reducing the amount of water that runs off a property. By using the collected rainwater for household tasks, a homeowner gets a free source of water, lowering their water bill and reducing the demand on municipal water treatment plants.  

Why Harvest Rain? The Benefits of Collecting Rainfall 

  • Capture free water to use for watering your lawn, garden, and houseplants. 
  • Reduce your water bill. 
  • Simplify the path of water to your home. Instead of a complex process of sourcing water from waterbodies, transporting, and treating it, all before the water gets to your home, we can collect rain right where it falls on your property. This lessens strain on infrastructure and lowers energy used at the water treatment plant. 
  • Lower the demand on municipal water sources, which is especially important for communities sourcing from groundwater. If many homeowners and businesses sourced part of their daily water use from rainwater, there could be less need for frequent, expensive water infrastructure maintenance and expansion. 
  • Reduce stormwater runoff coming from your property. Less stormwater runoff means less flooding in your neighborhood and less contamination of local waterways from polluted runoff.  
Downspout drains into rain barrel

Features of Rainwater Harvesting Systems 

Simply put, rain falls on a roof, flows through downspouts, and enters a container for storage. From there, rainwater harvesting system can vary in several ways: 

Cistern Size 

Collecting rainwater happens at different scales—from a 50-gallon rain barrel to a 100,000-gallon commercial cistern! The right-size container for a home will depend on household water use, the size of the roof (also called the catchment area), and the amount of rain, which can be estimated from average precipitation rates for the area. 

Cistern Location 

Rain barrels usually sit next to a home, directly under a downspout. Larger rainwater cisterns can be above or below ground.  


Systems also vary in how the water moves through them. Simple systems, like a rain barrel, move water purely through gravity, mostly for filling up a watering can or bucket. Large systems typically require some kind of pump to move water. These include direct pumped, indirect gravity, and indirect pumped systems.  


Rainwater can be contaminated by debris, dirt, dust, bird droppings, and other particles that collect on roofs between rains. Roof washers and filters are key to reducing the amount of contaminates that enter a rainwater harvesting system. Roof washers divert the initial water that falls on the roof so that the dirtiest water does not get into the cistern. Filters further improve the water quality of the collected rain. 

Rainwater harvesting is an excellent option to explore if you want to use rain as a resource and reduce your water bill. Obviously, you actually need to use the water you’ve collected to get the benefits of collecting rain. It might be wise to start with a rain barrel and then upgrade to a larger cistern when you’re ready to source more of your household’s water from rain. 

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