CNGA LooseLeaf April/May19

15 colorad o nga.org LooseLeaf  April/May 2019 Conservation with R A I NWAT E R & G R E YWAT E R Harvesting By Brad Lancaster Author of Rainwater Harvesting for Drylands and Beyond Harvesting rainwater and greywater are inexpensive, efficient ways to reuse on-site waters, rather than import more costly and resource intensive sources from reservoirs and water utilities. Besides, once your equipment and system is in place, the harvested water is free! Generally, the best practice for water conservation is to use water in this order: 1. harvest rain via rain gardens or earthworks (roof to landscape) first, 2. collect and re-use greywater, 3. collect and use rainwater from a tank (which also overflows to the earthworks), 4. utilize water provided through a municipal utility or special district last. Colorado laws on collecting rainwater Harvesting rain and roof runoff in rain gardens has always been legal, while collecting rain in tanks is limited in Colorado because of perceived conflicts with water rights related to groundwater and downstream users. A 2016 law made it legal for homeowners connected to the water grid to harvest roof runoff in a tank or tanks not exceeding a 110-gallon capacity. But, those not connected to the water grid can have much larger tanks. The collected precipitation is required to be used on the property where it is collected. New Mexico laws on collecting rainwater Most New Mexico homeowners can legally install and use a rainwater harvesting system with earthworks or large-capacity tanks. To find out if larger-scale commercial projects are allowed, check with the local contact for the state Water Rights Division. Santa Fe actually requires new construction, even for commercial buildings, to have some rainwater collection for landscape uses. Laws on collecting greywater Greywater harvesting is more widely accepted, and this perennial waste water from bathroom sinks, showers, tubs, and laundry machines at home can be used to irrigate landscapes. This can be as simple as a “bucket and chuck-it system” where you catch water in a bucket while showering, and then reuse on plants or to flush toilets. Setting up a system of enhanced natural infiltration The most efficient way to harvest rain is to design and install basin-like earthworks or rain gardens that enable more rainwater, and even greywater and air conditioning condensate to drain or infiltrate naturally into landscapes. The more efficient your earthworks and the lower the water use of your plant palette, the less you need will need a tank for additional collection. The keys to setting up an enhanced natural infiltration system are: • Slope hardscape and its runoff to adjoining landscapes. While rain will naturally fall onto the landscape itself, additional runoff water can be captured from roofs, patios and driveways with gutters, downspouts and swales. Capture the water as high as you can in the landscape, and let gravity distribute to points below. • Create three zones within your rain gardens—bottom, terrace and top. Each will have a different microclimate with the top being the hottest and driest and the bottom, the wettest and coldest. Plant according to water microclimate needs for best results. • Select water-efficient plants and mulch. A native plant palette is most water efficient. Once established, natives can thrive solely on free harvested waters. Mulch will increase water infiltration and decrease loss to evaporation. Research shows basins mulched with organic matter mulch retain twice as much moisture as those with gravel, while also feeding your soil’s beneficial organisms. Resources One-page site and water assessments for several cities in Colorado and New Mexico: harvestingrainwater.com/one-page-place-assessments Rocky Mountain Rain Garden Plant Matrix by Jason Gerhardt: harvestingrainwater.com/wp-content/uploads/2015/11/Rocky-Mountain- Plant-Matrix.pdf Downspout- and gutter-sizing table : harvestingrainwater.com/rainwater- harvesting-inforesources/rainwater-harvesting-inforesourcesdownspout- gutter-sizing Rainwater harvesting manual by the City of Albuquerque: ose.state. nm.us/WUC/Albq-brochures/rainwater-harvesting.pdf Information resources including books and links to websites on harvesting water from many sources: harvestingrainwater.com Rain garden photos reproduced with permission from Rainwater Harvesting for Drylands and Beyond by Brad Lancaster.

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