Headwater streams and farm dams

INTRO - Small dams in the upper catchments have a big impact on the persistence of stream flows and waterholes of many streams across Victoria in dry times.  Loss of continuity along streams threatens the survival and breeding of many fish and other aquatic animals.  Protection of high-quality habitat is critical for conservation but there are also solutions that can improve flows from small dams.

Protecting our catchments to conserve biodiversity in rivers and streams

Small dams in the upper catchments have a big impact on the persistence of stream flows and waterholes of many streams across Victoria in dry times.  Loss of continuity along streams threatens the survival and breeding of many fish and other aquatic animals.  Protection of high-quality habitat is critical for conservation but there are also solutions that can improve flows from small dams.

Public discussions of water issues give a sense that our river networks comprise the major streams and large in-stream dams.   And, from a purely volumetric point of view, that’s where many of the big problems are.  But discussions have done very little to address the impacts of small dams on these small headwater systems. 

Mapping of farm dams has shown half a million large off-channel dams and between two and three hundred thousand small farm dams.  These are dams that can be constructed without significant barriers to the licensing.  In terms of volumetric water use, they account for a really small fraction; less than 10% right across the basin.  We estimated the relative impact of different forms of water resource development across the river networks of the basin, and found that a huge fraction of the network is impacted by the small dams.  Managing these small dams is very important for the conservation water-dependent species within the river network. 

Castle Creek near Euroa has a very narrow catchment rising in the Strathbogie Ranges and crossing the plains into the Goulburn River.   When dams in the headwaters of the creek are half full, they stop the downstream flow of water.  Once they fill up and start to spill, flows occur as they normally would.  Farm dams have a particularly profound impact where periods of low rainfall and significant evaporative losses lead to the emptying of the dams, as this means a refilling phase which strongly influences the downstream hydrology.

Resources 

Links to Scientific papers, factsheets/websites etc

Living projects

Links to Exemplar projects