Assessment of Urban Land Use and Cover on Groundwater Recharge and Quality

Abstract

This study focusses on a method for estimating the urban recharge and evaluating the ground water quality for drinking and irrigation purposes. The study was carried out in the Liverpool Local Government Area of New South Wales, Australia, and it included year-long monitoring of four boreholes for the water table depth and water quality. Average depth of water table was in the range of 1 to 4 m from the land surface. The pattern of variations in the water table depth (WTD) varied across the four boreholes. The WTD variations between borehole 2 (BH2) and borehole 3 (BH3) were similar, but significantly different variations were exhibited in BH1 and BH 4, with BH1 showing a quicker response to rainfall events. The presence of lake appears to have influenced the recharge pattern in the adjacent area as reflected in the WTD variations in BH3 and BH4. The recharge rates for BH3 and BH4 was about 2 to 5 times higher than those observed for BH1 and BH2, which are located at a relatively greater distance from the lake. This indicates that the presence of urban lakes can influence recharge rate in the area. Water quality analysis indicated higher salt and turbidity levels, which may be attributed to the local geology (the Wianamatta group) present in the study area and/or possible saltwater intrusion. This has implications for the treatment cost associated with the supply of the groundwater for drinking and irrigation purposes. Pearson’s analysis indicated a significant correlation between EC, TDS, Turbidity and pH. The turbidity of groundwater varied between 33 and 530 NTU, indicating that the turbidity may have been affected by the dissolution of salt deposits via colloidal particles. Significant variations in groundwater quality during rainy periods, also, indicated the existence of groundwater recharge in the study area. This study highlights the issues associated with the groundwater recharge and quality management in urban landscapes and provides a basis for further research.