In the South West our access to safe drinking water is intrinsically linked to our rivers. 90% of our drinking water comes from surface water i.e. rivers and reservoirs, with groundwater (springs, wells, and boreholes) accounting for the remaining 10%. We are somewhat unique in this, as elsewhere in Britain groundwater accounts for a much higher percentage of drinking water sources. For example, Wessex Water gets 75% of its water supplies from groundwater.
During winter when high rainfall means the water level in rivers is very healthy, water is removed directly from the rivers, with the South West’s 20 reservoirs acting as back up. The river and reservoir systems are linked together by a network of pipes, enabling water to be pumped from rivers to reservoirs (rather than waiting for them to refill naturally), and crucially, allowing water to be moved around the region, from areas experiencing high rainfall to areas in the midst of a dry spell.
Such is the importance of rivers to our population’s drinking water (and to our wildlife) that South West Water have invested £100million since 1989 in dealing with inland waste water, ensuring our rivers and estuaries remain clean and healthy. According to the Environment Agency’s 2006 Chemical Survey, which measures the levels of pollutants in the water, 100% of the rivers in Cornwall and 98.91% of Devon’s rivers were of good or fair quality.
From rivers to homes
The fact that we have constant access to clean running water is something that we often take for granted in this country, but behind the scenes it is a rather long and highly scientific process that extracts water from our rivers and delivers it into our homes.
Firstly, the water is pumped from the rivers and sent to water treatment plants. Because the quality and chemical make-up of water can differ due to the various rivers it originates from, the treatment process is tailored to ensure the end product is of a consistently high quality.
Once the water has been collected, the first stage of treatment is screening to remove large objects such as branches and leaves which would clog up the treatment equipment. Then unwanted particles are removed, using flocculation (making them bigger and easier to remove), and filtering.Two methods of filtering are;
1. Rapid gravity filters: The water is passed through a tank full of course sand. The sand traps particles as the water passes through.
2. Slow sand filters: The water is then slowly filtered through large beds of much finer sand. This removes any remaining fine particles before the water goes for final treatment.
Other, extra, methods of filtering include ozone, carbon and ion exchange. These methods create chemical reactions in the water and remove fine particles.
Once the treatment process is complete, a very small amount of chlorine is added in order to kill any remaining bacteria, ensuring it is safe to drink. Once testing has confirmed that the water is of the required standard, it is pumped into our homes by a huge network of pipes and pumping stations.
Our access to safe clean drinking water is essential to our quality of life and in the South West it simply would not be possible without our rivers. Worth remembering next time you turn on your tap!