Using multiple methods to investigate the effects of land-use changes on groundwater recharge in a semi-arid area

• Published in: Hydrology and earth system sciences 2021-01, Vol.25 (1), p.89-104
• Main Authors: Barua, Shovon, Cartwright, Ian, Dresel, P. Evan, Daly, Edoardo
• Format: Article
• Language: English
• Subjects: Agriculture; Analysis; Annual rainfall; Annual rainfall data; Aquifer recharge; Aquifers; Arid regions; Arid zones; Catchment area; Catchments; Estimates; Evapotranspiration; Evapotranspiration estimates; Evapotranspiration rates; Fluctuations; Groundwater; Groundwater recharge; Groundwater resources; Groundwater table; Investigations; Land clearance; Land clearing; Land use; Land use management; Management; Mass balance; Methods; Precipitation; Rain; Renewal; Resource management; Semi arid areas; Semiarid lands; Semiarid zones; Specific yield; Surface water; Tritium; Uncertainty; Water; Water resources; Water table; Water table fluctuations; Water, Underground
• ISSN: 1607-7938; 1027-5606; 1607-7938
• DOI: 10.5194/hess-25-89-2021

Understanding the applicability and uncertainties of methods for documenting recharge rates in semi-arid areas is important for assessing the successive effects of land-use changes and understanding groundwater systems. This study focuses on estimating groundwater recharge rates and understanding the impacts of land-use changes on recharge rates in a semi-arid area in southeast Australia. Two adjacent catchments were cleared ∼180 years ago following European settlement, and a eucalypt plantation forest was subsequently established ∼15 years ago in one of the catchments. Chloride mass balance analysis yields recharge rates of 0.2 to 61.6 mm yr−1 (typically up to 11.2 mm yr−1). The lower of these values probably represents recharge rates prior to land clearing, whereas the higher likely reflects recharge rates following the initial land clearing. The low pre-land-clearing recharge rates are consistent with the presence of old groundwater (residence times up to 24 700 years) and the moderate-to-low hydraulic conductivities (0.31 to 0.002 m d−1) of the aquifers. Recharge rates estimated from tritium activities and water table fluctuations reflect those following the initial land clearing. Recharge rates estimated using water table fluctuations (15 to 500 mm yr−1) are significantly higher than those estimated using tritium renewal rates (0.01 to 89 mm yr−1; typically