They sound like a cool idea—especially just after the recent deluge in Sacramento—but in relation to building upstream dams like Auburn, not too competitive, as this blog post from California Water Blog notes.
Imagine capturing some of the heavy rain that has been draining off Northern California roofs lately to water yards this summer, for what will likely be a fourth year of drought.
The drought has generated interest in household cisterns commonly known as “rain barrels” that collect and store rooftop runoff for when it is most needed – during the dry season – to irrigate landscapes and replenish community groundwater supplies. Advocates of these rainwater collectors point to their prevalence in Australia following its decade-long Millennium Drought.
But how cost-effective are rain barrels for individual home and business owners, compared with the more communal approach of adding storage capacity behind a dam upstream?
Here are some back-of-the-envelope calculations:
The cost of household cisterns includes the storage tank, installation and connection to a roof, maintenance and the value of land for the cistern’s footprint. A 50-gallon rain barrel costs about $100, and a 300-gallon tank runs about $600.
The cost of the storage tank or barrel alone amounts to $652,000 an acre-foot of storage capacity (summed over many households). This compares with about $2,000 an acre-foot for expanding storage capacity at large upstream dams.
Retrieved February 9, 2015 from http://californiawaterblog.com/2015/02/08/the-romance-of-rain-barrels/