Abstract
Increasing uncertainties associated with land-use changes, growing population, and climate change motivate strategic management of groundwater for resource use and ecosystem dependencies for current and future needs. We use a major drinking water aquifer in the Hawaiian Islands to demonstrate the value of operationalizing groundwater sustainable yield policy using a multi-objective simulation optimization management framework. Sustainable yield is the amount of withdrawal that can be sustained for the long-term without impairing the resilience of an aquifer system and its dependent ecosystems. The Hawaiian Islands provide an ideal case study as the isolation makes self-sufficiency in water resources a necessity. In addition, the State's water policy requires water to be managed under a public trust doctrine, including protecting cultural and ecological values of water. The simulation optimization methodology allows us to analyze efficient spatial distribution options for groundwater withdrawals under varying constraints, including head level, salinity, and minimum spring discharge in the face of future uncertainties around land-use and climate change. We demonstrate the importance of incorporating additional constraints on groundwater withdrawals into management decisions, in order to better align with the public trust doctrine of the State's water policy. Our process provides a framework for engaging with water management agencies to align water policy tools with management goals. The approach adopted is applicable to many localities, such as other Pacific Islands, where cultural and ecological values are of critical importance.