Stocktake of your farm dams | Murray Matters

STOCKTAKE: The dry start to the year has resulted in low water levels in farm dams. Photo: MAX MASON-HUBERS

STOCKTAKE: The dry start to the year has resulted in low water levels in farm dams. Photo: MAX MASON-HUBERS

The dry start to the year has resulted in low water levels in farm dams. Generally speaking, the lower the level, the lower the quality of water.

Good quality water is vital for stock health. If water quality is poor, livestock potentially drink less than they require or, rarely, may stop drinking altogether. When animals drink less, it impacts on feed consumption; stock may lose condition and, if lactating, their milk production will reduce.

Animal water requirement is reduced during the cooler months. However, this will depend on:

• Class of stock, as lactating stock require significantly more water than dry and young stock.

• Feed on offer – dry feed such as hay and grain will increase water consumption.

• Higher salt levels will increase water consumption.

There are a number of water quality issues that can occur during and after extended dry periods, such as high salt levels in the remaining water, algae blooms, and water pollution.


As water levels reduce, the salt concentration can double.  

Pregnant, lactating and younger classes of livestock are less tolerant than mature dry stock.  Livestock grazing green feed can better tolerate salinity levels at the upper limit compared with those grazing dry feed, saltbush or eating a high-salt diet. Livestock can tolerate saline water to certain concentrations when introduced slowly, but marked increases may cause animals to refuse to drink it or cause toxic effects.


As dams shrink, stock is forced to wade in deeper for water, which causes the dam edges to become muddy and boggy. Our advice is to check dams after significant rainfall, as water may turn black and give off a putrid smell due to the runoff of manure, soil and vegetated material. One option to reduce debris entering the dam is to erect shade cloth across the inlet. 


Algae occur naturally in dams and troughs.  Algal blooms are common in summer in still or slow-flowing water when temperatures are warm and water is abundant with nutrients, in particular phosphorus and nitrogen.  

Most algal blooms are not toxic, but the build-up of algae in water reduces palatability and can block water pipes and outlets. Some, such as blue-green algae, produce toxins that can have serious health implications for humans, animals and birds. Blue-green algae forms a scum that looks like green acrylic paint and leaves sky-blue marks on rocks or plants around the edge of the dam. If you suspect a blue-green algae outbreak, remove stock from the water source and collect a sample for testing.

If you’re concerned about water quality, we advise you use a NATA-accredited laboratory. You need to collect at least 500 ml of water in a clean glass or plastic bottle. The water sample should be representative. NSW DPI water sampling kits are available at Albury LLS office.

Sue Briggs, is a senior land services officer, Sustainable Agriculture.