Assessing lifestyle, productive and environmental consequences of tailwater reuse in the Shepparton Irrigation Region, Australia

Abstract

Installation of tailwater reuse systems in irrigated farms is encouraged to achieve river water quality outcomes however, assessment of their efficacy in improving irrigation efficiency or intercepting nutrients and chemicals is limited to a few studies. The lifestyle, productive and environmental consequences of tailwater reuse dam on dairy farms was investigated using interviews, field monitoring and risk assessment in the Shepparton Irrigation Region (SIR) of Australia. Thirty one reuse dams were monitored during the 2013/14 and 2014/15 irrigation seasons, with water quantity and quality data collected.The farmers believe that reuse dams provide greater flexibility in water management and recycling on farm. Between 3 and 28% of water delivered to a reuse dam catchment was captured in the reuse dam. On average 63% of the total water captured in a reuse dam was pumped out for reuse. Only 14% of dam capacity was available to capture unanticipated storm runoff for 90% of the time. Reuse water satisfied environmental guidelines thresholds with respect to EC, pH and NOx-N, but greatly exceeded maximum levels for TN, TP and FRP with median concentrations of 8.1, 3.7, and 1.9 mg/L, respectively. Under current irrigation and resue practices productive risk appears low however, there is a likelihood of reuse water spills to regional drains following 25 mm in 24 h rainfall events. Even in the absence of large rainfall events number of spills were recorded on 46% of farms. Although it appears that the reuse dams in the SIR provide productivity benefits and environmental benefits to some extent, current reuse dam management practices on many farms do not conform to key recommended practices. Thus, the risk to the environment from spills of nutrient enriched water is greater than that envisaged by the regulatory agencies. The impact of water spilled into the drains is unclear and requires further investigation.