Improving performance of bay irrigation through higher flow rates

Bay (border check) irrigation systems are utilised extensively throughout the Goulburn Murray Irrigation District (GMID). However, the performance of these systems have rarely been assessed, in part due to the difficulty in determining the soil intake function. The CRC for Irrigation Futures has recently completed a project to demonstrate the Irrimate™ performance evaluation process in bay irrigation through on-farm trials. The Irrimate™ approach originally developed for furrow irrigation has already provided real benefits to farmers and has been accepted across the cotton industry. Bay irrigation has a number of unique characteristics which presented a number of challenges for the tools used to evaluate furrow irrigation. Informed by field trials, new monitoring strategies were tested and new modelling approaches developed in order to provide the same robust evaluation procedure for bay systems. Evaluations provide objective information to irrigators both quantifying efficiencies of current practices and providing strategies to improve performance. Trials were conducted across 11 sites in order to benchmark current performance and to examine the potential advantages of higher flow rates. Performance varied widely between sites with application efficiencies ranging from 45.9% to 89.5%. Initial modelling indicated that higher flow rates offer potential to increase efficiency. Trials in the second season confirmed the modelling work demonstrating water savings in excess of 20% through flow rates approximately double the conventional rates. The results also show that higher flow rates do not automatically lead to higher efficiency. When adopting higher flow rates irrigators must have greater control over cut-off times. System evaluation is an essential step to reap the benefits of higher flows. The results of this study provide objective information for the modernisation of irrigation systems in the GMID.