Here's an article he wrote about rainwater in Venice. And here's Anupam's recently translated book on the water systems of Rajasthan, "The Radiant Raindrops of Rajasthan" [PDF]. I skimmed sections of the book, and it seems like quite a resource for folks in the desert southwest. However, some of the prescriptions aren't technological, but social:
The sacrosanct line, which divides private property from common property, gets strangely erased when it comes to kuins [well-like structures that collect rainwater]. To each their own kuin; everyone has the right to construct a kuin and use its water. However, the kuin is constructed on land which is the collective property of the village. The rain which falls there remains throughout the year in the form of humidity and it is this humidity which feeds the kuins throughout the year. The amount of humidity present is determined by the amount of rainfall. Constructing a kuin in that area means sharing the humidity present there and that is why, though the kuin is a private property, since it is constructed on collective property, it falls under the control of the village society. It is only in case of dire necessity that permission is granted to build a new kuin.