Water Resources Research Act Program

Details for Project ID 2018HI481B

Solving the Silica Conundrum in Hawaiian Streams and Groundwaters using Non-Traditional Isotope Geochemistry

Institute: Hawaii
Year Established: 2018 Start Date: 2018-03-01 End Date: 2019-02-28
Total Federal Funds: $14,137 Total Non-Federal Funds: $64,374

Principal Investigators: Olivier Rouxel, Nicole Lautze, Eric De Carlo

Abstract: Freshwater resources have significant economic, cultural and ecological importance in Hawaii and other Pacific islands. Considering Hawaii's geographic isolation, increasing urbanization and global climate change, maintaining the sustainability of water resources in the islands represents a formidable challenge. It has now become apparent that Hawaii's water budget is fundamentally changing (Oki, 2004): rainfall over the Hawaiian Islands has been declining steadily over the last three decades. This trend is likely to continue with global warming through the end of this century, leading to a commensurate downward trend in base flow. The long-term downward trends in the base flows of Hawaiian streams may result in a reduction in ground-water recharge and storage, with serious implications for nutrient dynamics across the soil-vegetation-stream interface. Groundwater provides approximately 80 percent of the fresh water used in Hawai`i for drinking water, agriculture, and industrial uses (Wallsgrove and Penn, 2012) and nearly all the use on the island of O`ahu. In order to meet this growing need, some Hawaii aquifers have been already drawn to near or greater than their estimated sustainable yield. This threatens freshwater supplies and quality, and prompts the need for a better understanding of the hydrologic connection among groundwater systems and their recharge by surface water (Oki and Meyer, 2001; Whittier et al., 2010). Groundwater chemistry has been used to help determine groundwater flow paths (source to discharge), as well as to help assess the geothermal potential of deep aquifers across the State of Hawaii (Thomas, 1985)- the latter which sparked the interest of both the economic sector and civil society. But many questions regarding groundwater chemistry remain. Hence, a better understanding of Hawai`i’s groundwater chemistry and its dynamics bears important implications for the State’s sustainable groundwater, drinking water and geothermal resources.