Groundwater under a future climate

The challenge

Water resource management has traditionally relied on understanding how the observed climate impacts on groundwater resources, and then setting water entitlements on the basis that the observed historical climate is an adequate predictor of future groundwater resources. The last couple of decades have shown that the changing observed climate is also having a changing response to the groundwater. The challenge is that the historical observed climate is now acknowledged as not the best predictor of the future climate and so we need to integrate projected future climates into our projections of future groundwater condition.

Durba Springs (Jurrpa), Western Australia

Our response

We work with hydroclimate modellers to develop future climate projections that are appropriate to use in our hydrological models. This involves the global efforts in modelling the future climate using Global Climate Models (GCMs) under a range of Shared Socio-economic Pathways (SSPs). These GCMs results are downscaled to a local climate time series that can be used as an input in our hydrological models.

A suite of future climate time-series are run through an unsaturated zone model to produce projections of future diffuse recharge. A model such as WAVES has the advantage that it also simulates the carbon balance. This means that the dynamic response of the vegetation to the future climate (including CO2 fertilisation) is propagated through to the water balance.

In some aquifers the diffuse recharge may not be the dominant source of recharge to the aquifer. To determine the change in overbank flood recharge under a future climate requires that the future climate time series are run through a rainfall-runoff model and then a river systems model to simulate the future flooding projections. The change in overbank flood recharge can than be post-processed from the output of the river systems model.

The change in recharge is run through a groundwater model to simulate the future groundwater condition. This can be used to answer questions that policy makers may have around future groundwater levels or health of groundwater-dependent ecosystems under conditions of future climate and development.

This is still an active area of research for us in exploring how the boundary conditions between the climate, recharge, river and groundwater models interact to make appropriate projections of future groundwater condition that can be used by water managers and policy makers.

Lake Disappointment, Western Australia

The results

We work with state and Commonwealth water agencies to help answer their questions around the availability of future groundwater resources and the impacts that climate change may have on groundwater dependent environmental assets. This has resulted in water managers and policy makes having the appropriate information necessary for making decisions on how to allocate scarce water resources for both consumptive and environmental uses.

Contact

Russell Crosbie