Conservation

Managing water levels on wetlands

Dams

Dams constructed in drainage channels hold water within isolated hydrological units. It is not normally beneficial to dam a channel without some sluicing to enable controlled movement of water, but it can be used to rationalise ditch systems, for example to improve water control within an existing system. It is also a technique used for re-wetting damaged peat bogs. But wherever possible water should be able to move through the entire water control network preventing stagnation and nutrient build-up and ensuring free movement of aquatic flora and fauna.

Dam construction is easier using clays and loams. Clay and silt dams can effectively be used across channels up to 5 m wide. Peat will only make satisfactory dams if well compacted and even then the effective width is less. In general the basal width of the dam should be five times its height. The top of the dam should be level and at least 500 mm above the normal water level.