Design considerations
The size of a reservoir is governed by the water balance from the various water sources available and project budget. Currently, reservoirs in England over 25,000 m3 must be notified and registered with the Environment Agency. This is being reduced to 10,000 m3 in Wales and likely in England in the foreseeable future. A Panel Engineer must sign off the design, supervise and periodically check the reservoir to ensure its safety. The design of a reservoir is dependent on-site conditions, geology, water table, water storage requirements and other localised restrictions.
Evaporation losses can be reduced by using a floating cover. This can be installed as an impermeable membrane or floating tile system. However, a floating cover system is not typically aesthetic and placement of the reservoir may therefore prevent the use of such a system.
Generally, reservoirs do not provide as many ecological benefits as a pond network, as vegetation build up and shallow banks are not encouraged as part of the design. However, reservoirs can be important habitats for overwintering birds.