For the InstructorThese student materials complement the Water Science and Society Instructor Materials. If you would like your students to have access to the student materials, we suggest you either point them at the Student Version which omits the framing pages with information designed for faculty (and this box). Or you can download these pages in several formats that you can include in your course website or local Learning Managment System. Learn more about using, modifying, and sharing InTeGrate teaching materials.
As another hedge against water shortage and climate change, the Southern Nevada Water Authority has entered into a series of "Water Banking" agreements with other the Lower Basin Colorado River states, Arizona and California. In these agreements, Nevada pays the other Colorado River water rights holders to store unused water in times of surplus by injecting it into aquifers. Nevada then receives credits for the stored water; if the water is needed, Nevada uses the credits to draw the equivalent water from Lake Mead, and in exchange the "banker" withdraws the same amount from the aquifer. Although pumping is energy intensive, groundwater banking does not require construction of large reservoirs, and the water is not subject to large evaporative losses.
In its water banking agreement with Arizona, the SNWA paid $100 M initially, and began making yearly $23 M payments in 2009 that will continue through 2019. The agreement allows the SNWA to withdraw up to 40,000 acre-feet per year. In 2004, SNWA also began a water banking agreement with the Southern California Metropolitan Water District (the water district that serves L.A.) in which some of Nevada's surplus Colorado River water is stored in an aquifer in Southern California. The agreement allows the SNWA to withdraw up to 30,000 acre-feet per year, provided that they give 6 months notice. Since 1987, Southern Nevada has also been banking its own surplus water – when available - in the valley's aquifer for later use if needed. To date, about 330,000 acre feet have been stored.
1) How much is the cost of water banking per acre-foot? Do you think that's worth it – and how does it compare to the cost of other water resources?
2) Do you see a problem with the water banking approach to mitigating drought? Do you think it is sustainable in the long-term? Why or why not?