Climate change is widely predicted to impact upon the sustainability of water resources. Surface water sources are particularly susceptible to the predicted decrease in rainfall and increased occurrence of drought. However, groundwater resources are, to a lesser extent, also liable to be affected by climate change.
The rate of recharge is a key factor in the estimation of sustainable yield of an aquifer. Groundwater use is only sustainable when the abstraction rate from the aquifers is lower than the recharge rate. Aquifer recharge is the process whereby water reaches the aquifer, usually by percolation of water through overlying soils and strata. The rate of recharge is dependent upon rainfall, and most recharge occurs during heavier rainfall events. Following dry periods, very little rainfall will become recharged since rainwater will increase the soil moisture, and also cause surface run-off and possible flash-flooding. Only once the soil is sufficiently wet will rainwater percolate into the aquifer.