Balancing lake

In open countryside, heavy rainfall soaks into the ground and is released relatively slowly into watercourses (ditches, streams, rivers).

In an urban area, the extent of hard surfaces (roofs, roads) means that the rainfall is dumped immediately into the drainage system.

The function of a balancing lake as part of a sustainable urban drainage scheme is to contain this surge and release it slowly.

More advanced systems are computer-controlled such that the entire flow of a river can be diverted into a holding lake, perhaps to reduce the impact of a large scale rainstorm in the catchment on communities downriver.

Unlike most of the rest of the UK, the city has separate storm and foul sewers, so sewage pollution is not a significant problem.

The South Basin is designed for recreational use, mainly dinghy sailing and wind surfing, with a circumference path and banks as described above.