Influence of Historical Climate Patterns on Streamflow and Water Demand in Wales, UK

Abstract

Ensuring reliable drinking water supplies is anticipated to be a key future challenge facing water service providers due to fluctuations in rainfall patterns and water demand caused by climate change. This study investigates historical trends and relationships between precipitation, air temperature and streamflow in five catchments in Wales, before correlating these with actual total abstraction data provided by the water company, to give insight into the supply-demand balance. Changes in seasonal and annual averages, as well as extreme events, are assessed for a 34-year period (1982–2015) and a breakpoint analysis is performed to better understand how climate has already changed and what this might mean for the future of water supply. Results show a north-south divide in changes in extreme temperature and streamflow; a strong warming trend in autumn average temperatures across Wales (Sen’s slope range: 0.38–0.41, p <0.05), but little change in precipitation. Abstraction, as a proxy for overall water demand, is shown to be positively correlated to temperature (Spearman’s ρ value range: 0.094–0.403, p <0.01; Pearson’s r value range 0.073–0.369, p <0.01) in four of five catchments. Our study provides new insight into the relationship between abstraction volume and hydroclimatic factors and highlights the need for catchment-scale water resource planning that accounts for hydroclimatic variations over small spatial distances, as these nuances can be vital.