Performance evaluation and improvement of bankless channel surface irrigation systems

Bankless Channel Irrigation Systems (BCISs) are a surface irrigation system composed of adjacent, terraced bays with an interconnecting channel constructed such that the rim of the channel is level with the floor of each adjoining bay. The mode of irrigation is similar to Drain Back Level Basins (DBLBs) where the accumulated surface storage of each upstream bay is used to augment flow to a downstream bay. The systems of this study have been adapted from rice-based layouts to incorporate furrows for row-cropping. It is this style of BCIS that has generated considerable interest in Australia, particularly in the south east, where the system is used to grow a variety of crops and offers considerable labour and machine efficiency savings. Two defining features of BCISs are a positive field slope which rises from the bankless channel, and the hydraulic interaction between adjoining bays during the recession phase of the upstream bay and the advance phase in the downstream bay. These two features make evaluation challenging and mean no available hydraulic simulation model can simulate irrigation in these systems across an entire field. To improve the irrigation performance of BCISs a method of evaluating current performance was required. Consequently, the objectives of this research were to firstly identify appropriate evaluation methods for evaluating BCISs, then use these methods to evaluate the performance of current systems. This understanding could then be used to identify appropriate hydraulic models for the purpose of identifying parameters which influence irrigation performance in BCISs. In developing appropriate irrigation evaluation techniques for BCISs, a variety of evaluation methods were employed on a commercially operated BCIS in the Murrumbidgee Irrigation Area (MIA) of south eastern Australia. Field measurements were taken during a number of irrigations in the 2007/08 irrigation season from a central furrow in each bay of the three bay system. It was assumed that advance across the bay would be uniform given the positive slope of each bay. Observed variation in the advance front between furrows within individual bays suggested advance was not uniform. Consequently, several furrows were instrumented in the subsequent irrigation season of 2008/2009. Evaluation results showed a significant difference (p