Lower Derwent Reservoir, Peak District
“Water, water everywhere, nor any drop to drink!” as The Rime of the Ancient Mariner goes. In the UK there have been numerous droughts over the last fifty years, with water supplies affected in the 1970s and 1990s. The lessons learnt from those droughts have meant that infrastructure has become much more resilient to drought conditions and may be one reason why drought isn’t all that high on the public agenda unless there’s a hosepipe ban. It may not always be that way, and it’s important that the message of responsible and efficient water use continues to be promoted otherwise people will continue to be unhappy and perplexed when water restrictions are imposed.
Whilst an overabundance of water has caused floods and made the headlines across the country in recent years, memories of droughts tend to fade. And yet the IPCC’s climate models predict that as extremes of weather become the new norm in the UK we’ll increasingly face droughts in future as well as floods. Our temperate climate is set to become increasingly polarised, and the challenge we are likely to face is can we store water from flood conditions to supply us in a drought.
As recently as 2012 parts of the country were experiencing severe drought, and these conditions exacerbated the flooding experienced at the end of that year, as the parched ground encouraged overland flow. By the end of 2012, 1 in 4 days had been drought and 1 in 5 had been flood. Wetter winters and dramatic floods in the meantime have pushed drought down the list in the public consciousness, perhaps because damage from flooding has had a greater impact and economic cost.
In the Environment Agency’s latest Drought Response document, published in June 2015, three types of drought are identified: Environmental drought, when a shortage of rainfall has a detrimental impact on the natural environment; Agricultural drought when crop production and farming practices are affected; and lastly Water Supply drought, when water supply is threatened. In general terms these are escalating conditions, and so a water supply drought takes longer to develop than environmental or agricultural drought conditions.
Aside from climate changes, efficiency gains are being made at a household level - around half the population now have water meters and in the South-East they have become compulsory – driven by water stress. However the majority of our defence against drought takes the form of centralised major infrastructure. But can we learn from other sectors where approaches are changing to a more localised, decentralised model?
As renewable technologies have become more widely available there has been a proliferation of smaller-scale energy generation across the country. District heating systems, the norm in Scandinavia, are becoming common here too, sharing benefits of local power generation and waste heat. Anaerobic digesters are now a common sight on farms and in communities to process organic waste and harvest the useful methane gas generated for biofuels, power generation or injection back into the grid.
It’s not beyond the realm of possibility that local resilient water supplies for drought conditions could supplement major infrastructure, although it’s true that the distribution of electricity, heat and gas are much less constrained by gravity than water without pumping.
The problem is that while smaller scale power generation can be distributed reasonably evenly across the country, rainfall is not. Even with local resilience solutions, the south-east would remain water stressed, while other parts of the country remain water-rich. This is not a dissimilar situation to the wind industry, where supply is richest around the north and west coasts.
With the inequality in rainfall across the country, the future is likely to require more mechanisms to transport water from water-rich areas to water-stressed areas. This could include, for example, abstracting rebounding city groundwater supplies to relieve environmental drought in watercourses.
Whilst the idea of community-scale resilience is appealing, bulk transport across the country needs major infrastructure – like the Elan Valley Aqueduct which supplies Birmingham from Wales. The truth is that much of this major infrastructure is creaking at the seams – in fact Severn Trent is in the process of developing an alternative water supply for Birmingham to enable it to maintain the 100 year old structure more regularly.
Water companies have been creative with this in the past. For example, transporting water between catchments along rivers like the River Tame, and the extensive canal network is another obvious choice for moving water to drought areas.
As our weather patterns become more polarised, our design approach needs to become more integrated in order for us to effectively adapt to a changing climate. In between householder water efficiency measures and major infrastructure, what could the community-level systems look like?
Perhaps the next stage of evolution for Sustainable Drainage Systems (SuDS) is to move beyond just attenuation, beyond water quality, and towards sustainable water supply for non-potable uses? In order to do this we need to further erode the silo thinking that can be prevalent in our design disciplines - water supply vs drainage design; above ground vs below ground. We need to become holistic systems-thinkers as well as experts in detailed design.
Ofwat suggests that rainfall on the average roof yields around 85000l/year, which theoretically could provide around one third of the yearly demand of a household of four people, taking British Water’s average usage figure of 180l/person/day.
So it’s not unimaginable that this could provide much of the non-potable water used day to day, although it does require a change of approach when designing new development. Sustainability criteria such as BREEAM already award new schemes additional credits where no rainfall is discharged off-site for small events with depths up to 5mm. Typically this is hard to achieve on any site where there is a positive discharge to sewer or watercourse, and so broadening thinking to re-use could be a means to achieve higher scores for new development as well as encourage cross-discipline thinking.
Drought may not be in the headlines at the moment, but it won’t be long before it is. In the meanwhile, despite barriers to overcome, we should be think, plan, design and implement more holistically and creatively how we can best utilise our water resources. On every scale there are benefits to be reaped. Big infrastructure is undoubtedly needed, but there are opportunities to build water resilience at smaller scales too which we should also explore.