The Spatial Dynamics of Droughts and Water Scarcity in England and Wales

Abstract

Water scarcity occurs when water demand exceeds natural water availability over a range of spatial and temporal scales. Though meteorological and hydrological droughts have been analyzed over large spatial scales, the impacts of water scarcity have typically been addressed at a catchment scale. Here we explore how droughts and water scarcity interact over a larger and more complex spatial domain, by combining climate, hydrological, and water resource system models at a national scale across England and Wales. This approach is essential in a highly connected and heterogeneous region like England and Wales, where we represent 80 different catchments; 70 different water resource zones; 16 water utility companies; and the water supply for over 50 million people. We find that if a reservoir's storage is in its first percentile (i.e., the volume that is exceeded 99% of the time), then there is, on average, a 40% chance that reservoirs in neighboring catchments will also be at or below their first percentile storage volume. The coincidence of low reservoir storage decays relatively quickly, stabilizing after about 100–150 km, implying that if interbasin transfers are to be provided to enhance drought resilience, they will need to be at least this length. Based on a large ensemble of future climate simulations, we show that extreme droughts in precipitation, streamflow, and reservoir storage volume are projected to worsen in every catchment. The probability of a year with water use restrictions doubles by 2050 and is four times worse by 2100.

Regional Differences in Spatiotemporal Drought Characteristics in Great Britain

“…Moreover the set of extracted drought events could be used for similar coherence analyses using different, operationally aligned regions in future. Importantly, however, here we only consider the possibility of coherent historical meteorological droughts but water resources planning requires future climate change to be considered and hydrological modelling and water supply system simulations to be undertaken (as in e.g., Dobson et al (2020)). Some studies suggest the likelihood of coherent droughts across regions is likely to increase in future under anthropogenic warming (Rudd et al, 2019) whereas others do not show such large changes in coherence (Dobson et al, 2020).…”

Selecting Indicators and Optimizing Decision Rules for Long‐Term Water Resources Planning

“…Consistent with several other water planning studies, this framework uses a discrete event simulation model to represent the water supply system (Dobson et al., 2020; Mortazavi‐Naeini et al., 2015). In simulation, decision rules are consulted at discrete time steps to inform adaptation actions.…”

“…This study follows the same hydrological modeling framework outlined by Dobson et al. (2020), using the best performing DECIPHeR parameter set for catchments in the Thames Basin to simulate future flows. For the purpose of this study, the 30‐year Near and Far Future flow scenarios are transformed into 100 longer 80‐year transient time series, as explained in supporting information .…”

Hot Spots and Climate Trends of Meteorological Droughts in Europe–Assessing the Percent of Normal Index in a Single-Model Initial-Condition Large Ensemble

“…Lorenzo-Lacruz et al (2010) for example state an increasing correlation between drought indices and hydrological variables in central Spain for longer drought periods. Nevertheless, for impact assessment other indices, accounting e.g., for the effects of temperature or evapotranspiration, may be better suited, e.g., in conjunction with the use of impact models like hydrological models (Dobson et al, 2020). Lorenzo-Lacruz et al (2010) find that the SPEI shows more severe droughts within their Spanish study area than the precipitation-only based SPI, suggesting that without temperature the (hydrological) impact of droughts may be underestimated.…”