Water balance, climate change and land-use planning in the Pearl Harbor Basin, Hawai'i

The Pearl Harbor basin on the tropical oceanic island of O'ahu, Hawai'i, exhibits extreme climatic gradients, rapid land-use change and groundwater use near sustainable yield. The basin's water usage and groundwater recharge, and hence water yield, are strongly influenced by the spatial distribution of land use. Current recharge is expected to drop by about one-eighth with the demise of the remaining sugar-cane and pineapple. Evidence suggests that lower rainfall and increased evaporation may well accompany warmer periods in Hawaii, and water-balance simulations indicate many scenarios having a significant decrease in available water. Land-use planners can use such results in tandem with multiobjective optimization models to generate alternative land-use plans and show trade-offs among objectives.