Water-Table Data Description

Observations of the transient water table that forms at the soil-bedrock interface were collected using a spatial grid of 135 crest-stage gauges (Figure 4a) and a smaller set of individually instrumented continuous recording wells (Figure 4b). Extensive saturation at the bedrock surface, as recorded by crest-stage gauges and water-table wells, only occurred during the two largest rainstorms. These rainstorms (6 February 2002 and 30 March 2002) are described in Tromp-van and McDonnell (2006c).

The crest-stage gauges record the maximum rise of the water table generated at the soil-bedrock interface during a defined period of time, typically associated with a rainstorm; pieces of floating cork rise within the gauge and stick on a wooden rod at the maximum water table elevation above the bedrock surface in each gauge. The locations of the 135 crest-stage gauges are shown in Figure 4a (see also Figure 2 in Tromp-van Meerveld and McDonnell, 2006c). Spatial maps of maximum water-table elevation are available for 17 periods (Datafile 3). Observations of maximum water-table height are binned into ranges of no rise, 0-10, 10-20, 20-40 and >40 cm. Note that several crest-stage gauges were installed beyond the left-hand side of the trench, corresponding to bedrock depressions shown in Figure 2 and Figure 4, in order to investigate if any saturated flow was bypassing the trench on that side of the hillslope.

A series of 29 water-table recording wells provide additional temporal information on the dynamics of the development and decline of transient saturation within the hillslope (Datafile 4). The 29 recording wells are located along two downslope transects and within a bedrock hollow (Figure 4b). Recording wells were instrumented with capacitance rods (Trutrack, New Zealand; the use of brand names is for information purposes and does not indicate endorsement by the U.S. Geological Survey), which measured water table height greater than 7.5 cm above the soil-bedrock interface. Capacitance rods were unable to record water table heights below 7.5 cm (blanking depth). As a result, all water-table heights are expressed in cm above the 7.5 cm blanking depth of capacitance rods (e.g., 1 cm recorded water-table height = 8.5 cm actual water table height).

Recording wells and crest-stage gauges are named by location using the X, Y coordinates of the 2 m grid (see DEM). For example, well 9.20 is located 9 m from the right-hand side of the hillslope and 20 m upslope of the trench face. Metadata provided within the Excel spreadsheet list the names and locations of the 29 recording wells. 

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