Assessing the impact of climate change on groundwater in an area in New Zealand

Climate and its variability have a considerable impact on seasonal water resources availability. Understanding the impact of climate change and the time lagged  response in areas where groundwater is the main water resource supporting human activity (water supply, agriculture and industry), is necessary to manage potentially damaging consequences for hydrologically-driven ecological functions, ecosystem services, economic response and adaptation, cultural values and recreation.  

In this study, we assess the impact of climate change on groundwater in Edendale area, South New Zealand, which has been experiencing increasing water abstraction pressure and declining groundwater level. We use downscaled CMIP5 IPCC climate predictions to drive a hydrologic model (TopNet) to simulate changes in land surface recharge (LSR) under different climate models and future climate scenarios (i.e. RCPs – Representative Concentration Pathways) , and then the ensemble of LSR simulations further drive the Edendale groundwater model (MODFLOW) to simulate groundwater system.

Our initial result show: in spite of differences in simulations of different climate models and future climate scenarios, to the end of this century, there will be a slight annual increasing trend both for precipitation and LSR, significantly in Autumn and less significantly in other seasons; generally groundwater level and groundwater discharge (to rivers) will be increasing, following seasonal and annual patterns of changes in precipitation and LSR; differences are large for both climate models and future scenarios, largest for RCP8.5 and smallest for RCP2.6. We hope the results will support the long-term water management planning in the Edendale area.