A groundwater recharge field study: site characterization and initial results

Abstract

Abstract:A ®eld study site was installed in east-central Pennsylvania to examine processes controlling groundwater recharge. It was instrumented to monitor climatic inputs, soil water dynamics and groundwater response. Characterization of the layered fractured bedrock underlying the site by rock coring, seismic surveys and interval packer testing showed consistencies between layer depths, fracture frequencies, seismic velocities and hydraulic conductivities. Monthly summaries of rainfall and percolate over two years showed that percolate rates were generally high and closely related to precipitation during the dormant season. During the growing season, however, the relationship became erratic with large variabilities occurring between individual lysimeter measurements. Eight dormant season rainfall events were examined in detail. Smaller events produced similar responses from 1 m deep percolate lysimeters. Approximately 10±15 mm of rain was required to initiate percolate, with the time delay in response dependent on how long it took this depth to accumulate; 5 to 6 mm of the rain was retained in storage, with the remainder becoming percolate. Larger rains, from 30±110 mm, caused correspondingly larger depths of percolate and larger water table responses, but generally similar patterns of site response. Groundwater at the site was typically about 6 m below the land surface during the dormant season. It responded 1±2 hours after the onset of percolate, and reached its maximum elevation anywhere from 4 to 16 hours after that, even though percolate was still occurring. Based on causative depth of recharge and amount of water level rise in wells, the speci®c yield of the aquifer was found to be of the order of 0 . 01. This value is characteristic of fracture geometry rather than matrix properties of the bedrock.

Combined estimation of specific yield and natural recharge in a semi-arid groundwater basin with irrigated agriculture

“…(7) known as the ''water-budget method'' for estimating S y (Healy and Cook, 2002), was initially proposed by Walton (1970) and was afterwards used namely by Hall and Risser (1993) and Gburek and Folmar (1999). The water-budget method is the most widely used technique for estimating specific yield in fractured-rock systems, probably because it does not require any assumptions concerning flow processes (Healy and Cook, 2002).…”

Discrete‐Storm Water‐Table Fluctuation Method to Estimate Episodic Recharge

“…Previous studies of recharge at Masser site include those of Gburek and Folmar (1999) and Risser et al (2005Risser et al ( , 2009). Heppner et al (2007) analyzed individual recharge events at the Masser site using two methods: lysimeter data analysis and WTF analysis with the MRC method.…”

Hydrometric transit times along transects on a steep hillslope

“…The HTT variations for the downslope points showed distinctively different response features from the upslope points (see Figure 5d). An abundance of macropores in the undisturbed soil layer can cause rapid response in the water table as shown in Figure 5c [ Gburek and Folmar, 1999]. Upslope contributions and relatively large topographic convergence (see Figure 1) at downslope part lead to the difference between Figures 5c and 5d [Kim, 2009].…”