Effects of global change on streamflow, water demand and supply: a case study from the Pyrenees

Abstract

Water resources have a fundamental value for both ecosystems and society. However, changes in climate, population, consumption patterns, land use and urbanization are affecting its quality and future availability. In Andorra, a country located in the middle of the Pyrenees, the confluence of climate change and a socioeconomic model with an important weight of the tourism industry based on an intensive use of water could threaten the future sustainability of water resources. This paper analyses the water resources of Andorra and its future sustainability using the Water Evaluation and Planning system (WEAP) modelling tool. The WEAP-Andorra model presents an initial estimate of the national water demand segregated into the main water consumers in the country (i.e. tourism, residential, primary sector, snowmaking, and hydro power production). It explores the future evolution of water resources combining climatic, including an extreme drought scenario, and socioeconomic variables (i.e. demography, tourism, irrigation, and snowmaking trends). The model includes an Adaptation scenario to assess the impact of some strategic adaptation measures. The results indicate a significant decrease in annual streamflow across all simulated scenarios by 2050. In the global change scenarios, yearly streamflow is projected to decrease between 5.3% and 8.5%, while in an extreme drought scenario, the loss reaches 65.4%. The impact of global change on future water demand at the country scale is not expected to be compromised. However, in an extreme drought scenario, it could be affected. The sectors most affected by the combination of global change and drought could be ski resorts, especially to ensure snowmaking and hydropower production. The future frequency and duration of droughts will determine the severity of the unmet demand.