Waterwise Landscaping | Conserve Water | Create Diversity | Rainwater Harvesting
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The Library Garden Demonstrates Harvesting Rainwater for Landscape Use

Rainwater harvesting is the capture, diversion, and storage of rainwater for landscape irrigation and other uses. Harvesting rainwater can reduce the use of drinking water for landscape irrigation. Coupled with the use of native and drought-tolerant plants, rainwater harvesting is an effective water conservation tool because it provides ‘free’ water that is not from the City’s municipal water supply.

There are many benefits to harvesting rainwater. Water harvesting not only reduces dependence on groundwater and the amount of money spent on water, but also reduces off-site flooding and erosion by holding rainwater on the site.

Rainwater harvesting is appropriate for large scale landscapes such as parks, schools, commercial sites, parking lots, and apartment complexes, as well as small scale residential landscapes. System design ranges from simple to complex. A rainfall water harvesting system has three components: the supply (rainfall), the demand (landscape water requirement), and the system that moves the water to the plants. Storage is an additional element which is optional.

The Library Garden demonstrates rainwater harvesting by draining rainfall runoff from the adjacent parking lots and directs it into a catchment area that is built of boulders and concrete. The runoff is captured and used immediately to water the high to moderate water use plants that are located in a concave depression due south of the catchment area. Western River Birch, horsetail, cattails, and irises are planted in the depression or gully that runs north-south through the Library Garden.

"No Watering" Option

Although this is a controversial idea to some people, simply not watering and relying on rainwater to irrigate a landscape is an option. Having a rainfed-only versus an irrigated lawn has several pros and cons as outlined in the tables. Motivations for this approach are multiple:

  • water conservation
  • reduced water bills
  • smaller quantities of lawn chemicals or none at all
  • reduced labor and costs for landscape maintenance, and
  • reduced adverse environmental effects.

To rely strictly on rainwater for irrigation is to accept the fact that lawn grass naturally turns brown during hot, dry periods. The reason that many lawns, particularly those with cool-season grass species, look bright green under a broiling sun is that they are kept that way artificially with supplemental irrigation. Dormancy is nature’s mechanism to help grass survive heat and drought; a lawn will “recover” with the return of rain and cooler temperatures.

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