Tag Archives: rainwater harvesting

Last week GrowNYC completed 2 new rainwater harvesting installations at community gardens in the Bronx River Watershed. Funding was provided by the Bronx River Watershed Initiative.

Belmont Little Farmers

A 500 gallon tank was connected to the downspout of a building with a 600 sq foot roof adjacent to the garden. The installation was completed by GrowNYC staff and members of the GreenApple Corps. A trellis was also built to grow vines to beautify this Bronx Land Trust garden.

River Garden

Located directly on the Bronx River, the River Garden was in need of a new shed, a shade structure and water for irrigation purposes. The new 100 sq foot shed with an attached 100 shade structure provides 200 sq feet of rainfall collection surface. The water is stored in a 305 gallon tank. The system also provides storm water management by diverting rainfall from running directly into the river. The project was completed by GrowNYC staff with the assistance of the Bronx Environmental Stewardship Training program of Sustainable South Bronx.

Last night’s downpour covered New York City in an inch of rain and caused flooding in some neighborhoods. Storms place a huge burden on the city’s sewer system, the effects of which are felt by the local watershed.

GrowNYC has helped build over 60 rainwater harvesting systems in community gardens throughout the city. These systems help mitigate stormwater runoff, reduce the demand on the public water supply system, and make it easy for gardeners to water their gardens. But just how much water do they save?

The general formula we use for calculating rainwater harvesting potential is that one thousand square feet of catchment area (like a roof) will yield 600 gallons of water per inch of rain. We also take into account the efficiency of the systems and say that 75% of potentially harvestable rain is actually collected.

If a typical building’s footprint is 20′ x 50′ (1000 square feet), that means 450 gallons of water could have been harvested by last night’s one inch rainfall. A typical 10′ x 10′ shed could have harvested 45 gallons.

For reference, a typical watering can is about 2.5 gallons.

More information about GrowNYC’s rainwater harvesting program is here.
For a PDF guide to building your own system, click here.