I'm way overdue on one of these and only a little bit on the other.
I have often wondered if the concept of unitization (a governance regime for oil/gas reservoirs that imposes reservoir-wide management by combining the interests of multiple producers under a single management entity) could be applied to aquifer management. In my opinion there are certain aspects of existing forms of aquifer management that incorporate elements of unitization - adjudicated groundwater basins probably come closest, but none are truly unitization as practiced in the oil fields. Todd Jarvis, who is on the faculty of Oregon State University, as part of their Institute for Water and Watersheds, recently authored a paper (links to the abstract, I think you have to pay for the full paper) that looks at this idea from a theoretical perspective. Todd points out in an email that this approach might be useful in places, such as California, that have very little existing management of groundwater resources but considerable experience with unitization in oil fields. It's an interesting idea that I think merits further study.
The other document that is of great interest to me is the final Cornerstones Report on Market-Based Responses to Arizona's Water Sustainability Challenges prepared by the talented folks at Ecosystem Economics and the National Fish and Wildlife Foundation under a grant from the Walton Family Foundation (who have been funding a number of initiatives related to preservation of riparian ecosystems in Arizona). I haven't had a chance to do much more than glance through the report, but I did have a chance to review a draft copy last winter and participated in one of the workshops that helped brainstorm ideas to inform this report. It's a very honest and thorough assessment of the realities and challenges associated with using market-based approaches to securing water for environmental needs in Arizona and I highly recommend taking a look if this interests you.