Originally Published: January 26, 2018 5:58 a.m.
Although water conservation is an important way to reduce groundwater pumping, people often ask, “Why should I conserve water when it will only support more new home building?” This is an important question with a complex answer.
First the easy part: Landscaping water accounts for about 30 percent of Prescott’s water use and can be greatly reduced with the use of drought-tolerant plants and virtually eliminated by adding on a simple rainwater harvesting system. Landscaping water is lost to evaporation and thus not available for recharge or reuse. Reducing landscape water use directly curtails groundwater pumping and decreases the overdraft of our aquifer.
The relationship between interior water conservation and development is more complicated because Prescott receives recharge credits from the Arizona Department of Water Resources for collecting wastewater and recharging the aquifer. Recharge credits become part of Prescott’s water portfolio and can be allocated to new development.
For existing homes connected to the municipal sewer system, conserving water indoors means less groundwater pumping and less water down the drain, thus reducing recharge credits for new development.
However, homes on septic tanks do not create recharge credits, so for them, reducing interior water use directly reduces groundwater pumping.
For new homes built on lots platted before 1999 in the Prescott Active Management Area, the allocation of water per home is fixed by state law. Even if these homes use less water, the City of Prescott cannot use the saved water to authorize more homes, but it can capture wastewater for recharge credits. Again, interior water conservation directly reduces both groundwater pumping and recharge credits.
For new homes built on lots platted after 1999, or for new subdivisions of fewer than 250 acres, Prescott must allocate recharge credits to prove a 100-year water supply. Because Prescott has already allocated most of its recharge credits, the City is now stretching the remaining water by reducing the allocation per home. This does not save water or reduce groundwater pumping because it permits more home construction.
So in this case, better conservation may permit more new homes. The upside is that housing demand may be met without the expensive Big Chino pipeline project.
For a new subdivision in an annexed area exceeding 250 acres, Proposition 400, passed by Prescott voters in 2005, requires that all recovered wastewater must be recharged without receiving credits for new development. This protected recharge benefits the aquifer, decreases the overdraft, and cannot be used for new homes.
In summary, water conservation by existing residents constrains new development and reduces groundwater pumping. However, Prescott’s efforts to stretch recharge credits will allow more development. On balance, the Citizens Water Advocacy Group (CWAG) believes we are all better off by conserving water, not using municipal water outdoors, and using rainwater harvesting for landscapes of drought-tolerant plants.
Naturalist Walt Anderson presents “Granite Dells: A Threatened Community Resource” when CWAG meets on Saturday, Feb. 10. Details at www.cwagaz.org.
Please submit your questions or comments to firstname.lastname@example.org.
Gary Beverly chairs the Citizens Water Advocacy Group Public Policy Committee and is a retired business owner working to protect the Verde River.