Detecting changes in streamflow response to changes in non-climatic catchment conditions: Farm dam development in the Murray-Darling basin, Australia

Anecdotal evidence suggests that farm dams have an impact on the streamflow regime of a catchment. There is however a notable absence of suitable information on the nature and magnitude of these impacts. This work seeks to address this knowledge gap by identifying the nature of the impact of farm dams on the hydrology of catchments in the Murray-Darling Drainage Division, Australia. The 12 catchments selected for this analysis span zones of the Division with very different climatic and land use conditions. In 11 of the catchments considered there has been an increase in farm dam development over the last two to three decades. The remaining catchment, on the Jamieson River, has undergone no land use changes over the last 50 years and was selected as a control catchment for testing our approach. Statistically significant reductions in the quantity, potential streamflow response (PSR), were found for two catchments, the Yass River and Broadwater Creek. The average annual increase in farm dam capacity in these two catchments was 1.5 and 3.3% of mean annual flow, respectively. The remaining nine catchments displayed no statistically significant reductions in PSR for the entire period of simulation. Farm dam capacity information was available for five of the nine catchments. These five catchments displayed significantly smaller increases in farm dam capacity (not more than 0.3% of mean annual flow per year) than the Yass River and Broadwater Creek catchments.