Page 261 - VEWH Seasonal Watering Plan 2020-21
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The Broken system includes the Broken River, upper Broken Creek, lower Broken Creek and the Broken wetlands.
5.5.1 Broken River and upper Broken Creek
System overview
The Broken River is a tributary of the Goulburn River, rising in the Wellington-Tolmie highlands and flowing north-west to Benalla and then west for a total distance of 190 km before it joins the Goulburn River near Shepparton. Lake Nillahcootie is the main storage on the Broken River. It is about 36 km upstream of Benalla and harvests water from the river to support stock and domestic supply and irrigated agriculture. The main tributaries of the Broken River are Hollands Creek, Ryans Creek and Lima East Creek.
Lake Nillahcootie has a storage capacity that is about half the mean annual flow of its upstream catchment, so it fills in most years. The operation of Lake Nillahcootie has modified the river’s natural flow pattern: winter/spring flow is less than natural because a large proportion of inflow is harvested, while summer/autumn flow is higher than natural because water is released to meet downstream irrigation demands. These impacts are most pronounced in the reach between Lake Nillahcootie and Hollands Creek. Below Hollands Creek, the river retains a more natural flow pattern, due to flows from unregulated tributaries. The catchment has been extensively cleared for agriculture including dryland farming (such as livestock grazing and cereal cropping) and irrigated agriculture (such as dairy, fruit and livestock).
Water is released from Lake Nillahcootie to meet downstream demand and minimum flow requirements specified under the bulk entitlement for the Broken River system. Releases from storage may be less than 30 ML per day as tributary inflows immediately below the storage (such as from Back Creek) can supply much of minimum-flow requirements specified in the bulk entitlement.
Upper Broken Creek is defined as the 89-km stretch
of creek from the Broken River (at Caseys Weir) to the confluence with Boosey Creek near Katamatite. Upper Broken Creek flows across a flat, riverine plain and has naturally low runoff from its local catchment. It receives flood flows from the Broken River, although the frequency of these floods has been reduced by earthworks and road construction.
Upper Broken Creek has been regulated for more than
a century. Before 2007, water was diverted into upper Broken Creek at Casey’s Weir to meet local demand, but recent water savings projects have reduced the demand
on the creek. There is now low flow throughout the year between Caseys Weir and Waggarandall Weir. Flow below Waggarandall Weir is mainly influenced by rainfall and catchment runoff. These changes have reduced the amount of permanent aquatic habitat.
Delivery of water for the environment to the Broken River is primarily constrained by the availability of water. Usually, the available volume of water for the environment is insufficient to provide all recommended flows. Deliveries of water for the environment to upper Broken Creek are also restricted by channel capacity and by the need to avoid flooding low- lying adjacent land.
Environmental values
The Broken River retains one of the best examples of healthy in-stream vegetation in a lowland river in the region. A range of native submerged and emergent plant species including eelgrass, common reed and water ribbons populate the bed and margins of the river. These plants provide habitat for a range of animals including small- and large-bodied native fish species. Murray cod, Macquarie perch, golden perch, silver perch, river blackfish, mountain galaxias and Murray-Darling rainbowfish all occur in the Broken River. The river also supports a large platypus population.
The upper Broken Creek area is dominated by unique box streamside vegetation and remnant plains grassy woodland. It supports numerous threatened species including brolga, Australasian bittern, buloke and rigid water milfoil. Much of the high-quality native vegetation in the region is set aside as a natural features reserve. Upper Broken Creek supports a variety of native fish species including carp gudgeon, Murray cod, golden perch and Murray-Darling rainbowfish, as well as platypus and common long-necked turtle.
Both the Broken River and upper Broken Creek are listed in the Directory of Important Wetlands in Australia.
5.5 Broken system
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