James A. Roumasset

Cost Optimal Joint Management of Interdependent Resources: Groundwater vs. Kiawe (Prosopis pallida)

Local and global changes continue to influence interactions between groundwater and terrestrial ecosystems. Changes in precipitation, surface water, and land cover can affect the water balance of a given watershed, and thus affect both the quantity and quality of freshwater entering the ground. Groundwater management frameworks often abstract from such interactions. However, in some cases, management instruments can be designed to target simultaneously both groundwater and an interdependent resource such as the invasive kiawe tree (Prosopis pallida), which has been shown to reduce groundwater levels. Results from a groundwater-kiawe management model suggest that at the optimum, the resource manager should be indifferent between conserving a unit of groundwater via tree removal or via reduced consumption. The model’s application to the Kona Coast (Hawai‘i) showed that kiawe management can generate a large net present value for groundwater users. Additional data will be needed to implement full optimization in the resource system.

Incentivizing interdependent resource management: watersheds, groundwater, and coastal ecology

Managing water resources independently may result in substantial economic losses when those resources are interdependent with each other and with other environmental resources. We first develop general principles for using resources with spillovers, including corrective taxes (subsidies) for incentivizing private resource users. We then analyze specific cases of managing water resources, in particular the interaction of groundwater with upstream or downstream resource systems.