Assessing the impacts and potential control of terrestrial plant colonization of a reservoir bed during an extreme drawdown event

Murray-Darling Freshwater Research Centre

MDFRC item.

Extended periods of drawdown of reservoirs can result in the 'terrestrialization' of the lake bottom sediments, which describes the process whereby the exposed dry sediment takes on soil-like qualities. Opportunistic colonization of lake bed by terrestrial plants can occur under such conditions. A survey of plant communities of a large reservoir (Lake Hume) following its extreme drawdown, resulted in significant quantities of carbon, nitrogen and phosphorus being bound up in the terrestrial vegetation that colonized the lake bed. The phosphorus uptake from the sediment into plant material particularly could represent a significant pathway for phosphorus re-mobilization back into the lake. The potential of using stock grazing as a control measure for mitigating the effects of terrestrial plant colonization is also discussed.