The Chess is dependent on the surrounding chalk for groundwater which provides the water you see flowing in the river, once it reaches the surface by upwelling through springs. Groundwater levels fluctuate with the seasons in response to rainfall recharging the groundwater. As a result, the river levels also fluctuate throughout the year, but there is a time lag between seasonal changes in rainfall and the river level. Therefore, the amount of rain received during spring has a significant impact on the amount of flow seen in the river later in the year. And this relationship between groundwater and river flow means that the Chess is highly dependent on groundwater levels to maintain good habitats for wildlife. View an interactive animation of how a chalk aquifer works (1.7 MB).
However, this natural system is put under stress by the abstraction of water from the river's groundwater catchment. Affinity Water (formerly called Veolia Water and Three Valleys Water) provides the public water supply for the area. 99% of the water they abstract from the Chess catchment goes to supply water to the public, most of it to local homes. A big problem is that the demand for water here is very high. For example, the average person in Chesham who lives in a property without a water meter uses 176 litres of water per day. Compare that to the average UK water consumption per person of 148 litres per day. In addition to this pressure, Thames Water also has an abstraction point in the Chess catchment; the water they abstract is exported out of the catchment to be used for drinking water supply in Thame.
Providing for this high demand has meant that the Chess is now classified as "over-abstracted" (see the Colne Catchment Abstraction Management Strategy: http://publications.environment-agency.gov.uk/pdf/GETH0108BLUD-e-e.pdf). There is now only enough water in the Chess to meet its environmental needs for around 35% of the time. Flows in the Chess can be very low, particularly during summer. Significant stretches of the Upper Chess in Chesham have dried up in recent years, including 1992, 1996-97, 2005-06, 2009 and 2011-12. It is estimated that it can take up to a decade for stretches to fully recover after drying out. Reduced flows can decrease habitat availability for wildlife and cause pollutants to become more concentrated.
Water demand in this area is likely to increase as a result of local development. Chiltern District Council published the its Core Strategy in 2011, outlining development for the district to 2026. A total of 2,650-2,900 new houses are planned for the district, with Chesham identified as one of the key towns for development - these new properties will all require water.
Climate change is also expected to impact upon water availability and demand. The South East of England is expected to have warmer, drier summers which will increase the demand for public water supply. This means that in the future the Chess may be smaller, and sections may dry up more and more often.
It's Easy To Take Action
Water is pumped to meet demand, so if we reduce our water consumption, the actual volume of water taken from the catchment will be reduced. Getting a water meter installed is an easy way to monitor your usage and save money. Visit our links page to find the many web sites providing advice on how to save water.