EFFECTS OF HYDROGEOLOGICAL SETTING AND ESTIMATION METHODS ON GROUNDWATER FLOW VECTORS

Groundwater flow vectors were estimated at four well sites with dissimilar hydrogeological settings using two methods: borehole flowmeters, and hydraulic gradient coupled with conductivity data. The wells at all four sites were completed in unconsolidated geologic materials. In wells where vector estimations by the two methods differed greatest, the direction of groundwater flow was influenced by local drainage where relief was relatively great and measurement depth was relatively small. Local hydrologic features such as proximity to a sub-regional groundwater divide, fault zones, and pumping influenced the flowmeter-derived estimates but were not indicated by maps of the potentiometric surface. Flowmeter-measured Darcy velocity was 1–4 orders of magnitude greater than the Darcy velocity estimated from hydraulic gradient and conductivity data. A summary variable to qualify estimates based on hydraulic conductivity, saturated thickness, relief, drainage density, and recharge may be useful to identify sites where flowmeter measurements will (1) be affected by local hydrologic features and (2) vary with vector estimations from hydraulic gradient and conductivity data.