2.3 Hydraulic gradient analysis
Contours of groundwater elevations have been developed using data obtained from monitoring wells around the pond at elevations -5 mTAW and -20 mTAW. Four days have been selected to monitor the contours, two representing winter conditions (01/19/2015 and 01/11/2016) and two representing summer conditions (07/13/2015 and 07/19/2016). The contours help in visualizing the groundwater elevations as well as the direction of water flow. The flow of groundwater occurs in two distinct directions, i.e. radially outwards from the infiltration ponds to the pumping wells and radially inwards from the area outside the pumping wells towards the pumping wells.
Vertical hydraulic gradients are calculated using heads at elevations 3.55 mTAW (approximately 3 m below the surface), 0.55 mTAW (approx. 6 m below the surface) and -5 mTAW (approx. 11.5 m below the surface) at well series WP 21, 22, 23 and 24 surrounding the infiltration ponds. Analysis has been done on the average heads for the summer months (JJA) and the winter months (DJF) for 2015 and 2016. The variation of hydraulic heads with different seasons is also reflected on the vertical hydraulic gradient. WP 6.2 is assumed to reflect the conditions exactly underneath the ponds as it is located centrally between the two ponds. Vertical hydraulic gradient has been calculated between WP 6.2 and the pond bed to observe the variation of vertical gradient between summer and winter