Saving Hertfordshire's 'rainforest'
PUBLISHED: 09:38 20 March 2018 | UPDATED: 09:38 20 March 2018
A global rarity, Herts’ chalk streams are threatened by increasingly dry seasons and housing development. Our water demands could be deadly
Towards the end of last year I took a walk along the river Gade near Water End. Recent heavy snow had turned the countryside white, while the flowing river sparkled in the winter sunshine. From the footbridge I realised that the water was very shallow, barely enough for a game of Poohsticks, which we used to enjoy here when my children were younger. I heard a kingfisher’s call – a rapid song reminiscent in tone of a squeaky toy – and soon spotted it perched on a twig overhanging the water, its bright turquoise back distinct against the snow. It seemed not to notice me, sometimes diving into the water and returning to its perch with a fish in its long bill, sometimes flying, low and straight, over the water to another perch.
A chalk stream sparkling in the sun, perhaps with a sighting of its resident kingfisher, is a classic Hertfordshire scene. Rivers like the Gade, Ver, Mimram and Beane are fed by springs arising from water (the aquifer) in the underlying chalk. They shaped much of the county’s landscape and the mills they once supported were essential to the local economy. There are 161 chalk streams in England, 85 per cent of the world’s total, renowned for the rich variety of wildlife they support, including rare and declining species like water vole and brown trout.
At the moment they are in trouble. The low flow on the Gade is a symptom of low winter rainfall. From October 2016 to March 2017 under two-thirds of the average rainfall for this period fell over the county. Winter rain is essential to keep the aquifer topped up and chalk streams flowing. October 2016 was especially dry in Hertfordshire, with under 40 per cent of the average rainfall. Last October was equally dry, and in November the Ver at Colney Street had only 21 per cent of its normal flow, a situation replicated across the county and the Chilterns. Although there was some heavy rain around Christmas, as I write in early January the situation remains critical. At the end of December the aquifer in the upper Ver valley was nearly six metres (just under 20 feet) below the average expected, the lowest level for 20 years.
Low flows on chalk streams have become increasingly common during the last 100 years. Recent climate changes, with warmer summers and changes in the pattern of winter rainfall, have added to the lowering of the aquifer caused by increasing amounts of water being taken for the public water supply. Thanks to lobbying by bodies concerned about the chalk streams, like the Ver Valley Society and the River Beane Restoration Association, in some places the amount of water taken from the aquifer has been reduced. A borehole at Bow Bridge in the Ver Valley, which produced six million litres a day, closed in 2016, while from another at Whitehall in the Beane Valley abstraction was reduced by 90 per cent last year.
By far the biggest threat looming over our chalk streams is the massive growth in housing proposed for the county and throughout southern England. Between 40,000 and 50,000 homes are proposed for the Green Belt alone in Hertfordshire. In the Dacorum area, where the upper reaches of the Gade are located, a recent consultation on growth options proposed up to 25,000 new homes by 2036. If all of these are built there will be a 40 per cent increase in the number of households in the borough. Without major new sources of water, and there are none likely to be available soon, water supplies for new developments in the county will primarily come from the hugely stressed chalk aquifer.
Some globally-rare habitats which occur mainly in the UK, such as limestone pavements and Caledonian pine woods, have protective conservation status. England’s chalk streams have little protection. A few have been designated as wildlife habitats but none of the streams deriving from the Chilterns aquifer are included in this list. National planning policy requires local planning authorities to ensure that developments they permit do not have unacceptable adverse impacts on the natural or historic environment, including the flow and quantity of surface and groundwater, or on human health. Dacorum Borough Council devoted nine lines of text in its recent consultation document to this issue, saying only that ‘The council, water companies and developers will work together to ensure that investments are made in water and sewerage infrastructure and that essential new infrastructure is delivered.’
Will this be enough to keep our chalk streams flowing? Much depends on the weather. Ironically, we must hope for rain, and plenty of it, over the coming years. Otherwise our streams, and their kingfishers, may disappear, and that would be a tragedy.
Water End is about three miles to the north-west of Hemel Hempstead, on Ordnance Survey Explorer map 182.
Liz Hamilton is a member of Herts Campaign to Protect Rural England. Visit cpreherts.org.uk to find out about its work to protect countryside in the county from unnecessary development, and what you can do to help.