Time domain electromagnetic surveys for assisting in determining the groundwater resources on the Hamakua Coast, Island of Hawaii : preliminary report

Abstract

This report contains the results of surface Time Domain Electromagnetic (TDEM) geophysical surveys performed for groundwater resource evaluation along the Hamakua Coast on the Island of Hawaii. Blackhawk GeoServices (Blackhawk) conducted the surveys from April 15 through April 24 and May 1 through May 3, 2004 for Tom Nance Water Resource Engineering (TNWRE) and the Department of Water Supply (DWS), County of Hawaii, Hawaii. TDEM is a geophysical method that determines from the surface the geoelectric section (resistivity layering) of the subsurface. From the geoelectric section, information about geology and water quality can be inferred, this is possible because the electrical resistivity of the earth depends on lithology, porosity, the degree of saturation, and concentration of dissolved solids in the ground water. The main objectives of the TDEM surveys on Hawaii were to explore for possible basal and high-level groundwater occurrences at the survey areas. These TDEM surveys were conducted along four (4) mauka-makai transects located near Kukuihaele, Kapulena, Paauhau and Paauilo along the Hamakua Coast. Geophysical surveys, combined with other hydrogeologic information, are used to provide optimum locations for well placement and well completion depths.