A combined transient flow and water budget (TFWB) method and accounting procedure was developed and used to measure and partition the components of recharge to a sand and gravel aquifer underlying about 6.0 m of glacial till overlain by a nearly level land surface. The TFWB procedure was used to evaluate and quantify the dynamic interaction between surface recharge, till water level (at 2-4 m), and water cycling within the soil and vadose zone. Site-specific recharge activity was highly dependent upon surface microtopography. However, the homogenizing effect of the water table, measured by capillary movement of water through the vadose and soil zone, substantially offset the effects of surface and soil spatial variability and allowed relatively uniform estimates of local recharge at individual measurement sites. Substantial internal cycling of water within the soil and vadose zone was caused by the interaction of surface infiltration variability and water redistribution at the water table, even for measurement sites having little direct surface recharge activity. Through internal cycling, a single volume of water originating at the surface frequently passed through more than one soil and vadose profile during the recharge process. By applying TFWB procedures for the full soil and vadose zone between the surface to the water table, good estimates of local recharge to the Carrington aquifer could be made for the experimental area using few measurement sites.
ASJC Scopus subject areas
- Water Science and Technology