Open water, be it rivers, lakes or ponds, can appear very inviting in the warm weather – but they all hold risks.
Unlike a swimming pool, there are no lifeguards and the water is not chlorinated.
Animals swim and may drown in rivers and rubbish can fall in, as well as numerous hazards not immediately visible to the naked eye.
In a river such as the Lea, water levels vary and so too does the water quality. Much of the water in the Lea at Wheathampstead, particularly when there has been little rain, is effluent discharge from East Hyde sewage works. This is treated and tested to be safe for the environment, but it is not treated to be safe to drink.
Hot weather and low flows which normally occur when there is no rain can lead to a rapid decline in water quality. Also a lack of oxygen can dramatically impact on fish populations.
In the summer months harvest works disturb the earth so additional pollutants may reach the river.
Anything spilled on the road (e.g. hydrocarbons) can be washed into the river via storm drains. This is lower risk at present due to lack of rainfall, but if any surface water drain is flowing at this point, it is likely that contaminants are in that water. Similarly, sewer misconnections from private homes, such as washing machines connected to surface drains rather than the sewer, go through the storm drains to the rivers.
And of course one can drown face down in just a few centimetres depth of water, for example if you trip and fall.
No river in England is certified as safe for swimming; they all pose a risk if the water is swallowed.
Enjoy the river, but please be safe and keep away from danger.