Ground-Water Availability in the Wailuku Area, Maui, Hawaii

摘要

Most of the public water supply in Maui, Hawaii is from a freshwater lens in the Wailuku area of the island. Because of population increase, ground-water withdrawals from wells in this area increased from less than 10 Mgal/d during 1970 to about 23 Mgal/d during 2006. In response to increased withdrawals from the freshwater-lens system, water levels declined, the transition zone between freshwater and saltwater became shallower, and the chloride concentrations of water pumped from wells increased. To aid in management of ground-water resources and to plan for sustainable growth on the island, the Maui County Department of Water Supply (DWS) entered into a cooperative agreement in 2003 with the U.S Geological Survey (USGS) to study the ground-water availability in central and west Maui. The objectives of this 4.5-year study were to (1) obtain a better understanding of the ground-water flow system in the study area, (2) estimate ground-water recharge in the study area, and (3) simulate ground-water flow and transport using a numerical model to estimate the effects of selected withdrawal and recharge scenarios on water levels and the transition zone between freshwater and saltwater in the Wailuku Aquifer Sector. For management purposes, the State of Hawaii Commission on Water Resource Management (CWRM) divided central and west Maui into three aquifer-management sectors: Central, Wailuku, and Lahaina Sectors. Although the main area of interest for this study is the Wailuku Aquifer Sector, which includes the Iao and Waihee Aquifer Systems, the study area includes all of west Maui, the central isthmus, and about a third of east Maui in order to provide an understanding of the regional flow system.