Thursday 30 November 2017
Groundwater levels across the Chilterns have declined to worrying levels and fears of a major drought are growing after a dry autumn. While other parts of the UK have experienced high levels of rainfall and flooding in recent weeks, persistently low rainfall over the past year is taking a visible toll on the Chilterns streams. The Hamble Brook and Hughenden Stream have been completely dry for most of the year and where flow is present, in several rivers such as the Misbourne and Ver, it is currently less than a third of the average for the time of the year. The Misbourne is dry for more than 50 % of its total length and the Environment Agency have had to intervene recently to rescue fish from the receding waters. The Ver is dry for 10km between its source and Redbourn and flows are pitifully low despite Affinity Water reducing the water it takes from the valley by nearly 6 million litres a day last year. Even the R. Chess, considered by many as the healthiest of the Chilterns rivers, has dried through Chesham as groundwater in the valley reached its lowest October level since records began.
The worrying state of the Chilterns precious streams at present is mainly because last winter was so dry. Chalk streams rely on water held in the chalk aquifer for their flow and it is the rain that falls during the winter months (October to March) that soaks into the ground and replenishes the aquifer. Unfortunately, last winter provided less than two thirds of average recharge, which meant that levels peaked lower than normal and have declined ever since.
Although lack of rainfall has been the main driver for the poor state for the chalk aquifer and the condition of the chalk streams it supports, abstraction of water for public supply is also significant contributory factor. The Chilterns rivers have suffered from low flows for many decades due to the effects of high levels of abstraction and although some rivers have seen reductions in the amount of water taken, low flows persist in many. Although both water companies in the area, Thames Water and Affinity Water, have plans to reduce abstraction in the area, further over the next few years it may come too late or not go far enough to come to the rescue of the worst affected rivers.
Despite the condition of the area’s rivers and the low groundwater, a drought has still not officially been declared, which has led to frustration from several local river groups. The River Chess Association have called for water companies and the Environment Agency to take greater steps to reduce demand for water and protect the Chess and the Colne Valley Fisheries Consultative have voiced similar concerns for the Colne in a new film which they have published.
A dry autumn (October provided just a third of average rainfall) has raised fears of a second consecutive dry winter which would compound an already desperate situation for the area’s chalk streams. Allen Beechey, who manages the Chilterns Chalk Streams Project explained, “We will need significantly above average rainfall this winter in order to bring groundwater back to something like normal levels and revive our chalk streams. With each passing, dry month this seems less and less likely. Unless we get some exceptionally wet weather, like occurred in the summer of 2012, there is a real possibility that our rivers be in a worse position this time next year. It is clear that climate change is making our weather more volatile. We are certainly seeing droughts more regularly and with the level of development planned for the area the stresses on the aquifer and chalk streams will only increase. It is vital that we take greater action to protect these rare and precious rivers both now and in the future. Planned reductions in abstraction by both Affinity Water and Thames Water are greatly welcomed, but even greater reductions will be needed in future, for the long term health of the Chilterns chalk streams. Unless new strategic water resources are developed, this is unlikely to happen."