WRRCSR No. 7.4:85 Deep Percolation of Water from Pineapple Fields

Abstract

Efforts are being made to identify the sources, concentrations, spatial extent, movements, and rates of degradation of recently detected groundwater contaminants in Hawai'i. A spatially detailed evaluation of the time series of water percolation is required so that leaching from the top soil, downward transport through the profile, and eventual movement of the pesticides within the basal groundwater may be estimated. Using the water balance method, the 1946 through 1983 sequence of downward percolating water will be estimated for each present and former pineapple grating area of central O'ahu. Thus far, work on this project has focused on land-use identification, parameter evaluation, and data gathering. Results obtained using the same model in a previous study indicate that ET-suppression by pineapple causes percolation to be significantly higher than that experienced under a natural vegetative cover. This may account for the unexpected movement of these chemicals through the great thickness separating the pineapple fields from the basal water table.