The Cost of Alternative Water Supply and Efficiency Options in California

The Cost of Alternative Water Supply and Efficiency Options in California is the first comprehensive analysis to examine the cost of various strategies throughout the state to augment local water supplies and reduce water demand in urban areas. The study uses methods developed in the field of energy economics to determine the “levelized” costs of each supply and demand management option.

The study finds that the cost of new supplies in California is highly varied. Large stormwater capture projects are among the least expensive of the water supplies examined, with a median cost of about $590 per acre-foot. By contrast, seawater desalination, with a median cost of $2,100 per acre-foot for large projects and $2,800 per acre-foot for smaller projects, is among the most expensive water supply option. Brackish water desalination is much less expensive due to lower energy and treatment costs.

Generally, the cost of recycled water is in between that of stormwater capture and seawater desalination. Non-potable reuse – which treats water for irrigation and other non-drinking purposes – is typically less expensive than indirect potable reuse due to the lower treatment requirements; however, the cost of building or expanding a separate “purple pipe” distribution system to deliver non-potable water may be such that indirect potable reuse could be more cost effective.

Nonetheless, the study finds that urban water conservation and efficiency are the most cost-effective ways to meet current and future water needs. Indeed, many residential and non-residential measures have a “negative cost,” which means that they save the customer more money over their lifetime than they cost to implement.