Impacts of Autonomous Adaptations on the Hydrological Drought Under Climate Change Condition

Abstract:

Because of expected effects of climate changes on quantity and spatial distribution of available water resources, assessment of the changes in the balance between the demand and supply of water resources is critical for some regions. Historically, water deficiencies were overcome by planned water management such as dam regulation and irrigation. But only few studies have investigated the effect of anthropogenic factors on the risk of imbalance of water demand and supply under climate change conditions. Therefore, estimation of the potential deficiency in existing infrastructures under water-environment change is needed to support our society to adapt against future climate changes. This study aims to estimate the impacts of climate changes on the risk of water scarcity projected based on CMIP5 RCP scenarios and the efficiency of autonomous adaptation by anthropogenic water management, such as reservoir operation and irrigation using ground water. First, tendencies of the changes in water scarcity under climate change are estimated by an improved land surface model, which integrates natural water cycles and human activities. Second, the efficiencies of human-developed infrastructure are analyzed by comparing the naturalized and fully anthropogenic offline simulations.

It was found that number of hydrological drought days will be increased and decreased in approximately 70 % and 24 % of global land, respectively, considering anthropogenic water management, however, they are approximately 82 % and 16 %, respectively, under naturalized condition without anthropogenic water management. The differences indicate how autonomous adaptation through anthropogenic water management can reduce the impacts of climate change. Also, adequate enhancement of infrastructure is necessary against expected water scarcity under climate change because such positive and negative effects of artificial water regulation show comparable impact on water scarcity risk to that of climate change in regions where human activity is significant, even if it is under the worst-case RCP8.5 scenario. More realistic assessment of the impacts of climate change on water resources and the cost estimation of how much economic investments are needed to maintain the current level of the risks of water scarcity are necessary.