A new study published last week by Heather Cooley and colleagues at the Pacific Institute concludes that water conservation remains the cheapest water supply alternative as compared to the big new sources widely discussed, things like storm water capture, desalination, and recycling/reuse:

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.

Here are the data, lined up side by side:

cost of alternative water sources