Potential Impacts of Climatic Change and of Sea‐Level Rise on the Yields of Aquifer, River and Reservoir Sources

Abstract

Using regional statistics of daily rainfall, a simple water-balance model was employed to generate runoff sequences with which to simulate the yieldktorage behaviour of reservoin in south-east England, in north-west England. and North Wales. Similarly sequences of recharge to an unconfined aquifer in eastern England were the basis of deriving its yield/ storage behaviour. Then, taking scenarios of the year 2030 rainfall and evaporation, provided by the University of East Anglia's Climatic Research Unit, reductionsin yieldwere calculatedto be5-15YobeIow present-day values. For direct supply reSeNOin, greater percentage reductions in yield were found to apply to the south-east region, as compared to the north-west. The results from the aquifer example are interpreted on a novel basis which allows an immediate comparison with the surface reservoir examples.Coastal sea-water intrusion was modelled for three common geological conditions (i) the Grimsby Chalk (confined), (ii) the Brighton Chalk (unconfined), and (iii) the Otter Valley Sandstone (unconfined). In all three cases the effect of a possible 0.6 m rise in mean sea level was s h o w to have only a marginal effect on sustainable yields, which reduced by about 1.5%Estuarine fresh-salt water interfaces are important (0 the abstraction regime of freshwater intakes in the lower reaches ofriven. The effect ofa 0.6-m sea-level rise on the saline interfacc location at high tide was evaluated by hydrodynamic computational models. Only a minor inland shift of the interface was found, less than 800 m in the Thames tideway and less than 500 m in the Lune estuary. The Severn estuary is exceptional in having its saline interface move 3.5 km landwards for the Same 0.6-m rise in mean sea level.

Changes in the Distribution of Annual Rainfall in the British Isles

“…The ten-year moving average started to increase in the mid-1970s at each individual station in West Scotland. By contrast, a similar series for south-east England (not illustrated here) shows an infrequency of wet years since the 1960s and a slight downward trend (13). The wetness of western Scotland since the mid-1970s is outstanding over longer timescales.…”

Evidence for changes in historic and future groundwater levels in the UK

“…A small number of older studies exist (e.g. Cole et al, 1994;Cooper et al, 1995;Limbrick et al, 2000;Malcolm and Soulsby, 2000) but these are not considered here. First we review impacts on groundwater recharge and then we consider projections of changes in groundwater levels.…”

“…Water companies have undertaken a number of studies of the potential impacts of climate change on their groundwater sources but these are all unpublished. In addition to potential changes in borehole yields, changes in groundwater levels would affect baseflow discharge to rivers, and groundwater flood risk (Hughes et al, 2011) and saline intrusion to coastal aquifers, which only a few studies have considered (Cole et al, 1994;Malcolm and Soulsby, 2000). Yusoff et al (2002) provided evidence of the uncertainty in groundwater-level projections under climate change at a Chalk site in Norfolk.…”

Climate Change Water Resources Planning Impacts Incorporating Reservoir Surface Net Evaporation Fluxes: A Case Study

“…On that score, using GCM-based scenarios should be more convincing than using arbitrary changes in the hydroclimate (Arnell, 1996). With regard to water resources and river¯ows, some of the notable climate-change impact studies include Nemec & Schaake (1982); Gleick (1986Gleick ( , 1987; Nathan et al (1988); Cole et al (1991); Arnell (1992); Cole et al (1994); Burn & Simonovic (1996); Arnell et al (1997); Holt & Jones (1997). Their main concern has largely been how climate change affects single reservoir in¯ows and, eventually, the realizable yield.…”