Image caption: Map 1: Water level situation of rivers and streams in part of southwestern England (riverlevels.uk)
By Chad Staddon, Sun Shun and Stevie Miller
As of mid-2022, water levels across the world are lowering due to a long-term drying/heating trend. Rivers in parts of the UK are rapidly approaching low levels not seen since the historic 1976 drought, when the country saw temperatures exceeding 32°C for fifteen days with the nation’s highest ever recorded temperature reaching 35.9°C in Cheltenham. But now, the Met Office has issued its first Red Warning for heat, indicating a danger to life – but it’s not just the intensity of this heatwave that’s raising alarms. The frequency of heatwaves like this across the world speaks to the influence of human activity on global climates; record after record is being broken as years go by and climate change’s results become more apparent.
The impact of new peak temperatures is not just a family trip to the beach or day without rail travel. The worldwide repercussions of rising temperatures can be seen in examples such as Lake Mead, the almost-dry reservoir behind the iconic Hoover Dam in the US southwest, which is perhaps 100 days from being too low to produce hydroelectricity. Historic low flows in many parts of Australia are contributing to ever worsening fire seasons, a troubling pattern also seen as wildfires rage in parts of France, Spain and Portugal.
Here in the southwest of England we are experiencing an intensifying drought trend. The recent heat – as lovely as some summer warmth has been – has been problematic beyond just an uncomfortable lack of air-conditioning. Map 1 seems to show that whilst many stream flows are significantly below baseline averages (red or yellow dots), many seem to be doing okay (green symbols). But a closer look reveals a more complex picture.
Covering only the area around Bristol and Bath, Map 2 shows that even “green” stream flows tend to be only at or near normal levels for this time of year. Few streams are experiencing rising flows over any time horizon. Rather than being truly “healthy waters”, our rivers and streams are under a variety of threats that are combining to reduce average flows, impacting flora and fauna and human communities.
That’s not all: surface stream flows are only part of the story of our drying environment. During June groundwater levels receded in all aquifers – generally either just reaching normal levels or sinking below (with some notably low levels) – reflecting the prolonged period of below average rainfall and increasing soil moisture deficits. Similarly, reservoir levels fell, and although some increased relative to average (e.g., in western Scotland and Northern Ireland), others in the midlands (Derwent Valley), southwest (Colliford and Wimbleball), and Wales (Brianne and Elan Valley) were significantly lower than average. Our reservoirs are not yet as dangerously low as Lake Mead, but they are low enough that we may soon have mandatory water restrictions in some areas.
So, what can we do about the parlous state of our water resources? Certainly we must not give in to the temptation to believe that somehow the winter rains will save us, or that if recent years have been drier than average then surely coming years will be wetter and it will all come good. This is “magical thinking” and divorced from what the science of climate change is telling us. The longer-term climate trends suggest that our rains will be ever more unpredictable across the year and because surface and groundwater storage is limited, even periods of heavier than average rain may not help improve our water balance. We must also not sell ourselves the notion that new technologies, such as desalination or wastewater recycling, will save the day. Both are wonderful technologies, but they require considerable energy and capital inputs as well as producing waste outputs (e.g., brine) that are difficult to sustainably manage.
Really, it is to ourselves that we need to look for solutions to a deteriorating water supply-demand balance. It is said that the “average” water user in the UK uses 140-160 litres per person per day, though our research suggests that the actual range of water use is from approximately 100 to 250 litres per day. By better understanding who is using what volumes of water, for what reasons and under what conditions, it is possible to design demand-reduction policies that are effective and fit for purpose. This is where the future of water management needs to be. This is how we will save our dwindling water sources.
Source: Centre for Ecology and Hydrology (2022) Hydrological Summary for the United Kingdom, June 2022