The sad pictures of over a million native fish carcasses, floating along the Darling River in NSW, brought water quality right into focus. Local residents found dead Murray Cod over 50 years old, a grim indication of the significance of the disaster.
The striking feature, that kept repeating in interviews of concerned locals, was the genuine shock, the pained surprise that this happened.
An interim report by the NSW Department of Primary Industries found that the mass fish death was likely caused by a lack of dissolved oxygen in the water, caused by several related and compounding factors. These included high air temperatures up to the event, low flow conditions, and changes in water temperature associated with a drop in air temperature.
But fatalism and droughts aside, water flows can be largely managed. So why did this happen, and what can we do to prevent it from happening again?
We explore how continuous water monitoring is possible so that a fish kill event is never a surprise.
Water conditions and temperature can be monitored continuously. The conditions that increase the risk of algal blooms can be detected, such as elevated nutrient levels in waters, thermal stratification, and forecast changes in temperatures. Monitoring this risk can allow for active management, such as environmental buyback of stored water.
Commercial fish farms already use remote water monitoring systems to detect threatening environmental conditions to fish and prevent them before they become a real problem. Screenshot below of our work with Pentair, for illustration.
These remote sensor networks can continuously monitor water properties to understand the risks to ecosystems from pH, salinity, turbidity, and temperature, to dissolved oxygen and more. These commercial fish farms even undertake biological monitoring of the presence and abundance of pest invertebrate species.
Easy alerting and notification systems are automated and can trigger immediate remedial action (like using aerators to bring clean pest-free water up from depths) should a parameter fall outside tolerances. In fact, they take constant action, continuously refining water conditions, as measures trend in this direction or that.