On neutral ground: designing to minimise water use

Prolonged droughts are making water scarcity a global concern. Ramboll’s Rickesh Miyangar says new projects should aim for water neutrality, where water abstraction is no higher than existing levels

Over the summer this year, much of the UK experienced record spells of dry, hot weather, with hosepipe bans imposed in Yorkshire and much of South East England as the country grappled with mitigating its water-scarcity issues. 

Despite a damper September, two new reservoirs are being considered in Cambridgeshire and South Lincolnshire to provide water for 750,000 homes and help secure the region’s water supplies. Multiple water companies are reportedly also considering further drought measures. Emerging from this is a new concept for local authorities, developers and planners – water neutrality. 

Water neutrality is, essentially, the idea of water use in the area of a new development being equal to, or lower than, the previous total water use: that is, where water abstraction is not above the area’s existing levels. 

Many considerations need to be factored in when it comes to water neutrality. While existing measures can help improve the water efficiency of a site, more needs to be done to incorporate the idea of water neutrality into the planning stages of a development, especially as water abstraction can have an impact on the surrounding area, including the wildlife. 

Additionally, where drinking water is provided to a development by the local trunk mains, connecting larger developments to existing infrastructure needs to be assessed carefully to mitigate any adverse effects of a potential increase in water abstraction.

Reclaimed water systems offer the greatest water-saving benefits, reducing stress on aquifers

Achieving water neutrality

The reality is that water neutrality is far from simple to achieve. Setting stricter regulations could add an incentive for water neutrality to be planned into a project, but we cannot be too restrictive at this stage. 

Current Part G Building Regulations set a mandatory daily consumption of 125 litres per capita for new builds, which is a relatively easy goal to achieve. However, a more ambitious target of 80 litres per capita would require very strict measures. Currently, improving water efficiency is costly, and not all technologies are readily available or suitable for some developments.

Water neutrality may seem a distant goal, but steps to improve efficiency can still be taken, and there are a number of ways we can reduce a site’s water consumption.

Water efficiency techniques

‘Simple’ measures that can be easily implemented to improve the water efficiency of a development, including smart meters, flow restrictors and low-flush toilets. However, these alone cannot achieve the reductions required for water neutrality, or even a consumption figure close to it. As such, some developers may wish to consider reclaimed water technologies for their sites.

Rainwater, for example, can be harvested for re-use in the building for flushing toilets and irrigation (RWH), or greywater can be reclaimed from wash basins, showers and baths (GWH) before being filtered and treated, and passing into a clear-water storage tank. Strategically designed site-wide strategies may provide the greatest benefit to developers by linking the sustainable drainage system features to active/hybrid RWH/GWH systems.

Reclaimed water systems offer the greatest water-saving benefits, reducing stress on aquifers from over-abstraction, and reducing mains water costs. However, the equipment required for these systems can come at an increased cost for implementation and maintenance, so thought should be given to which measures are the most effective for each site.

The wider picture

The UK’s climate is changing and our summers are becoming drier. Water consumption and the idea of water neutrality will become an increasing focus for many stakeholders – it is only a matter of time before best practice is embedded in legislation as further water-consumption technologies are invented. 

At this stage, however, we should not be aiming for ‘net zero’ water. First, we need to better understand water demand and usage in prospective developments, and work to reduce demand in existing properties by offsetting, providing there is local stock against which to create the offset. 

Greater scrutiny of water efficiency is on the horizon, so stakeholders should take steps now to reduce a site’s consumption. Developing greater understanding of the available technologies and existing research, and embedding the water-saving methods best suited to a site, will help. If we take one lesson from this summer, it is that we must all start making that difference now.

About the author
Rickesh Miyangar is a director at Rambol