… saving water for a sunny day …

About the author

Derek Hunt is a founder-member of the UK Rainwater Management Association, and Managing Director of member-company Rainharvesting Systems Ltd.

Managing a scarce natural resource

According to the Environment Agency, water supplies are under varying degrees of stress, across great swathes of England south of the Humber estuary.  These stresses are predicted to become more severe due to population growth and changing weather patterns.

Ironically, right across the areas where supplies are most stressed, there is also a very high risk of localised flash flooding, a risk which will also continue to increase as population growth increases demand for the development of more homes and places of work.

So the good news for the development industry will the growing demand for its services, slightly tempered by the knowledge that future projects will need to take increasing account of the requirement to relieve stresses on water supplies, whilst also reducing flood risks.

Farmers already affected

The long, hot 2018 summer provides a handy reminder of what is forecast to lie ahead, and helps to validate what the Environment Agency has long been predicting will be the impact on UK growing conditions.  Short of simply accepting that their land is destined to become unproductive, it seems that the farming industry in southern England will have little option, other than to save winter rainfall for summer irrigation use.

There is plenty of evidence, particularly in the low-rainfall south-east of England, that this transition is already underway, with the construction of farm-level reservoirs in various forms.  Properly designed, these reservoirs can serve a double purpose by helping to reduce downstream flood-risks.  To do so, however, they will need to contain an “attenuation” capacity, that is spare capacity to temporarily store water during peak weather event for later slow release at a rate with which downstream drainage infrastructure can cope.

Farmers already affected

The long, hot 2018 summer provides a handy reminder of what is forecast to lie ahead, and helps to validate what the Environment Agency has long been predicting will be the impact on UK growing conditions.  Short of simply accepting that their land is destined to become unproductive, it seems that the farming industry in southern England will have little option, other than to save winter rainfall for summer irrigation use.

There is plenty of evidence, particularly in the low-rainfall south-east of England, that this transition is already underway, with the construction of farm-level reservoirs in various forms.  Properly designed, these reservoirs can serve a double purpose by helping to reduce downstream flood-risks.  To do so, however, they will need to contain an “attenuation” capacity, that is spare capacity to temporarily store water during peak weather event for later slow release at a rate with which downstream drainage infrastructure can cope.

Getting it right in Wales

This rural example of the need to manage rain at the point it falls, from both a flood and drought perspective, has been taken fully on board by the Welsh Government which identifies harvesting rainwater for re-use as its top priority in the design of sustainable drainage systems (SuDS).  This aligns well with the Principality’s aim of implementing Schedule-3 of the 2010 Flood and Water Management Act, which requires the Adoption of SuDS on new developments to ensure their long-term maintenance and effectiveness.

These are trends that the drier and more flood-prone regions of the UK will inevitably follow – particularly given one or two repeats of the 2018 summer; the challenge for the development sector is therefore to embrace these new surface water management challenges in a cost-effective way.

Against this background, it really beggars belief that it is beyond the national wit to manage rainfall in flood-prone areas in ways that safeguard subsequent water-supplies to avoid droughts.  A thought endorsed by the 2017 IPCC report, which identifies droughts as a significant threat to the UK environment and economy.