This is a small Basin with one main river (Broken River) draining from steep forested hills south of Benalla then flowing through flat farmland to the Goulburn River at Shepparton. Downstream of Benalla the Broken Creek branches off from the Broken River and flows to the Murray River near Barmah. The flat farmland which makes up most of the Basin has several areas of gentle sloping hills of sedimentary and granitic rocks and one small area of volcanic rock north of Shepparton.

The soils through which the waterways flow are composed of finely textured unconsolidated deposits resulting in mud and sand substrate in the rivers. Gravel and rubble substrates are restricted to the upper reaches of the Broken River. Mean annual rainfall decreases northwards from 700-1,000mm in the mountains around Lake Nillahcootie to 400-500mm towards the Murray River.

Lakes Nillahcootie and Mokoan store most of the run-off from the higher rainfall area resulting in low winter flows in parts of the Broken River and Broken Creek. The central area is used for grazing and mixed cereals with a large area of intensive irrigation and cropping in the north between Shepparton and Cobram on the Murray River.

The lower reaches of Broken Creek flow through red gum woodland (Barmah Forest). Despite the extensive farmland throughout the Basin there is good riparian vegetation of mature red gums along the larger waterways. Surface water is fresh. There are high levels of turbidity in Broken Creek.

Water is diverted from the Broken River via Gowangardie Weir to Shepparton, also via the Broken Weir into Mokoan Lake. From the Broken River via Casey's Weir to Tungamah and St James. Pumped from Broken Creek to Nathalia, Numurkah and Goorambat. From Hollands Creek via Hollands Weir into Lake Mokoan. From Ryan's Creek to McCall-Say Weir (1,140ML) and Loombah Weir (680ML) then to Benalla. From Back Creek to Devenish. From Boosey Creek to Tungamah. From Mt Glenrowan Creek via a 41ML reservoir to Glenrowan. From channels to Dookie, Picola, Katandra West and Katamatite. The Broken River is stored in Lake Nillahcootie.

None in this Basin.

Barmah State Forest and its associated waterways and wetlands, are listed as wetlands of international significance under the Convention on Wetlands (Ramsar, Iran 1971).

The Department of Sustainability and Environment has listed trout cod as Critically Endangered, Macquarie perch as Endangered, Murray cod, freshwater catfish and golden perch as Vulnerable and Murray rainbowfish and flat-headed galaxias as Data Deficient. Murray cod, Macquarie perch, trout cod, freshwater catfish, Murray rainbowfish, Murray spiny crayfish and the Lowland Riverine Fish Community of the Southern Murray-Darling Basin have been listed under the Flora and Fauna Guarantee Act 1988

The Murray spiny crayfish, Euastacus armatus, is also present in the Basin.

The upper reaches of Holland and Ryans Creeks flowing in forest are in excellent condition. All other waterways are only in moderate condition apart from some minor tributaries, which are in poor to very poor condition. Although the major waterways have good riparian vegetation, instream debris and fish cover in permanent pools, they suffer from low flows each year and a lack of flooding during spring (as a result of flow regulation) which inhibits spawning of native fish. Some reaches have bank erosion and sedimentation. Salinity is low but water quality for aquatic life is rated as moderate in most waters. However, poor conditions (high turbidity, low dissolved oxygen and high nutrient levels) occur in the lower reaches of Broken Creek.

There are a number of algae living in our fresh water and all are chlorophyll-bearing, aquatic organisms of simple organisation, either single-celled or multi-cellular. However none are as dangerous as the blue-green algae which is now considered to be a photosynthesizing bacteria rather than a true algae. Blue-green algae occur naturally in fresh water throughout the world but only become a problem when present in extreme numbers, forming what is called a ‘bloom’. Unfortunately a major problem for the management of Victoria’s water resources is the frequent occurrence of blue-green algal blooms in some waters. An algal bloom is triggered by a high level of nutrients, particularly nitrogen and phosphorus. Major problems associated with blue-green algal blooms are the production and release of toxins, the discolouring of water resulting in foul tastes and odours and accumulations of surface scums.

The decay of the algal bloom also results in a loss of dissolved oxygen in the water causing the death of fish and other aquatic biota due to lack of oxygen. Some species of blue-green algae have special characteristics that allow them to grow and multiply faster than other types of algae. For example some are able to use nitrogen from air as well as water. Some can use sunlight more efficiently than most algae, and other varieties contain pockets of gas that allow them to float to the surface and out-compete algae for sunlight.

Anglers need to be aware of the dangers of fishing in waters where a blue-green algal bloom is occurring. The water itself can be toxic if swallowed or cause rashes and itchiness to the skin if splashed on the body.

When the algae die and decompose they can release toxins into the water. These toxins can be neurotoxins (affecting the nervous and respiratory systems), hepatotoxins (affecting the liver) or toxins which can irritate or inflame the skin. If contaminated water is swallowed the cells can break down in the stomach and the toxins can enter the intestinal lumen. In time they reach the liver and cause the death of the parenchymal liver cells. This can be fatal. There are no known antidotes for blue-green algae toxins once a lethal dose has been ingested. Most conventional treatments and disinfection afforded most public drinking water supplies are not effective in removing or deactivating the toxins. Boiling is similarly ineffective. You might still catch fish in a contaminated water but they may taste muddy or earthy. The flesh can be eaten but the liver and gut are poisonous. For this reason people should not eat mussels or other shellfish collected from water affected by blue-green algae.

A reduction in nutrients entering the water, particularly phosphorus, is considered to be the best means for long-term control of these algal blooms. A number of initiatives are underway to reduce the input of nutrients into our waterways. However other factors such as rainfall and runoff, the colour and turbidity of the water, water temperature, the shape of the waterbody and in a river, the flow rate, all affect the likely-hood of a blue-green algal bloom occurring. The frequency of blue-green algal blooms indicates that the natural ecological balance of many of our waters has been altered by undesirable management practices. It will take sometime to restore this balance.