Efficient Water Allocation when Climate is Changing: An interdisciplinary approach

This study analyzes the effects of rising water supply variability provoked by climate change on the welfare of a society whose economy heavily depends on water availability. Several studies recommend that communities should impose policies that ensure a minimum level of water allocation for human consumption. We compare two contracts, one where society allocates to the firm a fixed proportion of the annual water-runoff; and the other one, where due to the uncertainties of climate change, the community instead allocates to human consumption a fixed annual amount of water-runoff. We consider a risk-averse community. We show that, unless water supply is absolutely fixed, a higher variability and scarcity of water supply does not necessarily imply that society is better off choosing a contract that assures a minimum water for human consumption. Depending on the characteristics of water supply frequency distribution, particularly the third moment, it is possible that society would not benefit by switching to the fixed allocation contract for human consumption. We illustrate the main analytical results using data and runoff climate change projections from a water basin located in the central region of Chile, showing that in this case the community is better-off sticking to the current contract.