Measurement and management of furrow irrigation at the field scale

Abstract

Generally, the measurement, evaluation and optimisation of furrow irrigation is restricted to a single furrow or small number of adjacent furrows. The measurement process is too intensive to be applied at the full field scale. Consequently it is necessary to assume that the infiltration characteristics and inflow rates of the measured furrow(s) represent the remainder of the field. Many people have observed or speculated upon the significance of spatial variability but few outline potential strategies to deal with the issue. Clearly, a new approach was required. Research conducted by the authors and others at the NCEA has investigated and developed potential tools and techniques to better evaluate surface irrigation accounting for spatial and temporal variability. A trial was conducted in a typical commercial cotton field to showcase the tools and techniques to evaluate and optimise irrigation performance at the field scale. The resulting data also provided an insight into the nature of spatial variability. Complete inflow, advance and runoff measurements were used to accurately determine soil infiltration rates for a small number of furrows. Single advance points were then used to predict the infiltration characteristics across the remainder of the field. Combined with the whole field simulation model IrriProb this data enabled evaluation of the true irrigation performance taking into account the inter-furrow variability in infiltration and advance rates. The use of the optimisation component of IrriProb demonstrated the ability to identify the optimal field management to maximise irrigation performance. The evaluated field was found to be operating at near optimal conditions however the analysis identified some further improvements to efficiency and uniformity through the adoption of higher flow rates.