Investigation of ground water level fluctuations at the Savannah River Site

Abstract

A primary concern at many waste sites is the ability to correctly predict the migration pathways of contaminants. We wish to determine the conditions that would result in erroneous predictions of contaminant trajectories. Ignoring the effects of barometric pressure can cause large errors in predicted trajectories in confined and watertable aquifers. We find the prediction error is largest in watertable aquifers because of barometric efficiencies near 100 percent. We propose to reduce this error by using total heads (water levels plus barometric pressure) to calculate the hydraulic gradient. An improved hydraulic gradient can be calculated even when water levels are measured at different times. Another proposal is to avoid using measurements following large precipitation events because these water level measurements could corrupt calculated hydraulic gradients for some wells. Water levels in wells near streams rise quickly following large precipitation events but usually return to normal once stormflows have subsided.