Polluted or low-quality water reduces the amount available for use. This increases pressure on water resources, especially in areas where demand is greater than supply (water deficiency).
Although the quality of river water in the UK has increased significantly over time there was a decrease in the overall number of water bodies awarded high or good surface water status between 2011 and 2016. In 2011, 37% of surface water bodies were assessed under the Water Framework Directive (WFD) in the UK as being in high or good status, falling to 35% in 2016; the indicator is therefore assessed as declining in the short term.
Status classification of UK surface water bodies under the Water Framework Directive, 2009 to 2016. Source – DEFRA – http://jncc.defra.gov.uk/page-4250
The main reasons for this are:
- chemicals used in fertilisers on farms, such as nitrates and phosphates, are being washed into rivers and groundwater;
- pollution from vehicles enter water sources as the result of run-off when it rains;
- chemical and oil spills from factories pollute local water sources and groundwater;
- sewerage waste can also enter water bodies;
- water running through old mine workings and old industrial sites can pick up hazardous heavy metals. This is known as historical waste.
Nearly 50% of the groundwater used for public supply in the UK is affected by pollution. This has led to many sources being closed or has had to undergo expensive treatment to make them safe for public consumption.
There is a range of strategies in place to support improving quality. This includes introducing regulations on the amount and type of pesticides and fertilisers that can be used. Also, drainage systems are improved to slow the movement of rainwater to that pollution can be broken down in the soil.