Hawaiian Alpine Lake Level, Rainfall Trends, and Spring Flow

Abstract

During the period May 1965 to November 1978 (162 months) 127 measurements were made of Lake Waiau water levels and overflow. This small perched body of water is located in Puu Waiau crater, at about 3970-m altitude, near the summit of the dormant volcano, Mauna Kea, Hawaii. Differences in water level are compared to the Hawaii statewide rainfall index, and to Waihu Spring flow. It is suggested that lake level is a useful indicator of rainfall trends among the islands. Measurements of the tritium concentrations of Puu Waiau crater perched lake and groundwaters, and of the nearby spring waters on the south slopes of Mauna Kea, are used to indicate that seepage from the lake is probably the principal spring-water source during drought periods. The tritium measurements suggest that something blocks direct groundwater seepage out of the Waiau crater, and indications are that the blockage is ice in a subsurface layer of relict permafrost. Study of the changes in lake and groundwater levels during the 30-month dry period July 1976 to December 1978 indicates that the groundwater basin probably occupies almost the entire Waiau crater catchment area (i.e., ~ 10 5 m2). It is suggested that permanent water-level and overflow gauges be established at Lake Waiau, and that long-term records from these gauges would be climatologically and hydrologically useful.