Climate change impact and adaptation
Impact assessment of climate change on groundwater resources
Weather extremes are expected to be more frequent and severe in a changing climate. Increasing dry spell duration will impact the equilibrium of groundwater table, while increasing rainfall intensity will help build up the aquifer’ capacity to mitigate the drought. The question is whether the restored ability of the aquifer for drought mitigation under present climate is still held in the future. It is answered by investigating how the aquifer balance will be affected by changes in the future climate.
The outputs of General Circulation Models (GCMs) are used to project local climate scenarios in the future. Due to the gap between the resolution of GCMs and the local spatial scale, the outputs of GCMs are downscaled to the local scale using statistical downscaling methods. Statistical analysis is performed to investigate plausible changes in the magnitude and frequency of extreme rainfall and drought events. The response of the groundwater table to the change of climate is investigated based on the outputs of groundwater models driven by the future climatic conditions. The ability of aquifers to mitigate the effects of drought in the future is assessed under plausible climate scenarios.
An example of the framework of assessing climate change impacts can be found in L. Wang 2015 external page(follow linkcall_made).
Identify the contributions of the climate, human activities and their combination to the state of groundwater resources
The climate has long-term influences on the state of the groundwater, while humane activities such as pumping for irrigation and artificial recharge have immediate effects on the groundwater table. For the shallow aquifer of the study area, the recharge mainly includes rainfall infiltration, infiltration from irrigation and seepage from rivers and channels. Currently, more than 70 % of the recharge of the shallow aquifer is contributed by rainfall. Changes in the future climate will thus have potential impacts on the groundwater resources. The depletion of groundwater is mainly caused by pumping for irrigation. Changes in water use including implementing water-saving measures and introducing surface water resources will also indirectly influence the groundwater state. The contributions of the climate, human activities and their combination are identified by analyzing the water balance of aquifers based on historical records. Analysis on the factors influencing recharge and depletion of the aquifer under the present climatic condition provides the basic information for the impact assessment of future climate change and for understanding the effects of water management policies.
Adaptation to climate change in GWM
Changes in the occurrence frequency and magnitude of climate extremes will impose new challenges on the groundwater management. Adaptation strategies need to be developed to keep sustainable use of groundwater resources against climate extremes. The strategy can be for example to implement the conjunctive water-use measures in order to preserve an aquifer’s capability of drought mitigation. Due to the deep uncertainty in the future climate, trade-offs need to be made between robustness and optimality of adaptive decisions. In this study, future climate scenarios are used to describe uncertainty as multiple views of the future. Adaptation strategies are assessed over a wide range of plausible scenarios, which allows decision makers to understand the assumptions underlying alternative options and to identify appropriate adaptations against expected climate extremes.