Mapping future water scarcity in a water abundant nation: Near-term projections for Scotland

With its abundant water resources, Scotland has ambitions to become a 'hydro nation'. Hydroclimatological projections indicate that the spatial and temporal distribution of water is likely to change, with parts of Scotland becoming significantly drier. This study, conducted in conjunction with the Scottish Environment Protection Agency (SEPA) looked to identify which regions and sectors may be subject to increased water scarcity pressures in the near-future (2020–2049). Accounting for more than 99% of (non-public water) surface water abstractions, four key water using sectors were considered: agriculture, aquaculture (finfish), hydropower (with storage; excluding run-of-river (ROR)) and whisky. Drought events, defined by SEPA as a period where daily flow falls below a long-term Q95 threshold for more than 30-days, were profiled in terms of their average frequency, duration and intensity (over a 30-year time slice). Two hotspots (of drought and abstraction) identified were the rivers Spey and Tay, which represent the centres of the Scotch whisky sector and agriculture respectively. Under climate change, the frequency of drought events could see a two or three-fold increase (median 2–7 additional events). The direction of the change in average drought duration was more uncertain (median change of 0–4 days per event). The results indicated that abstraction exacerbated the pressure. Capturing different sources of uncertainty (parameter and structural), the hydroclimatological data was drawn from two climate ensembles. Overall, the PPE (parameter uncertainty) was found to have narrower uncertainty bounds overall, though the MME (structural uncertainty) was subject to less uncertainty in specific locales in the north. These results highlight the limitation of focussing on one ensemble type/source of ensemble uncertainty across such a diverse domain. Overall, the paper demonstrates the need for a consistent approach to future water resource planning across Scotland. This planning must consider all sectors consistently and requires cross-sector and cross-disciplinary input and collaboration in order to facilitate wise use of future water resources.