The ongoing challenge for environmental water managers is to apply the best available science to achieve demonstrable ecological outcomes, often within highly modified systems that are primarily operated to meet the needs of irrigated agriculture.
Despite the highly regulated nature of Gunbower Creek a population of Murray Cod has managed to survive. However, a decade of annual fish monitoring has tracked the decline in the population, with distinct and persistent fragmentation indicating the lack of successful recruitment.
A new approach to managing environmental flows within the highly regulated Gunbower Creek was needed. We designed a full year environmental flow hydrograph to accommodate specific life history processes for Murray cod, without impacting on consumptive water users.
Two aspects of the regulated flow regime were identified as critically impacting on Murray cod; extreme daily flow variability throughout spring, and cease-to-flow conditions throughout winter.
Working closely with irrigation operator’s, environmental flow releases were augmented into irrigation releases, ensuring demands of irrigators and the Murray Cod were met. We termed this experimental flow regime for Gunbower Creek the ‘Murray cod hydrograph’.
During the first year of implementation, monitoring confirmed strong Murray cod spawning, and for the first time in more than a decade, a strong cohort of young-of-year Murray cod was detected in the following year. Three years on, monitoring has indicated an improved population structure and an increase in overall abundance of Murray cod in Gunbower Creek. The initial achievement of implementing this hydrograph represents a success story in cooperation and knowledge sharing between ecologists, catchment managers and irrigation operators.
We present new initiatives in flow management that are being applied in regulated rivers to restore fish populations.