Snowmaking's slippery slope: The effect of mountain reservoirs on water demand

Snowmaking is the primary adaptation of winter tourism to climate change and requires increased water use in winter. However, water withdrawals during this period coincide with the mountain low-flow period, which can potentially cause conflicts with other human uses and ecosystems. To address concerns about water availability, the number of reservoirs is increasing. Ski lift operators promote these reservoirs as environmentally beneficial under their ‘ecological engagement’ commitments, arguing that they reduce the impact of snowmaking by shifting some water withdrawals to periods outside the low-flow season. In theory, mountain reservoirs should therefore support both economic activity and environmental sustainability. Using econometric analysis of data from 35 ski resorts across nine seasons, we show that reservoirs significantly increase water withdrawals during the low-flow period. By employing maximum likelihood estimation of fixed-effects dynamic panel data models, we find that a 1 % increase in reservoir capacity leads to a 0.28 % short-term increase in low-flow withdrawals (0.4 % in the long term), ceteris paribus. These findings inform ongoing discussions to ensure that current socio-economic decisions do not lead to future water use conflicts in mountain socio-ecological systems. • Most of the water used for snowmaking is withdrawn during the winter low-flow period, a critical time for aquatic ecosystems. • Mountain reservoirs are expected to reduce water withdrawals during this period. • We find that mountain reservoirs increase water withdrawals during low-flow periods. • Mountain reservoirs heighten the risk of water use conflicts in mountain regions.