Evaluating whole field irrigation performance using statistical inference of inter-furrow infiltration variation

Inter-furrow infiltration variability is often ignored during the evaluation and optimisation of furrow irrigation. Existing techniques for estimating infiltration parameters are generally too intensive in measurement and computation for routine application at the field scale and have therefore primarily been used to study the behaviour of single furrows. This paper identifies the inter-furrow infiltration variation within typical furrow-irrigated fields and determines that this variation can be adequately described using a log-normal distribution. A procedure to predict whole field furrow infiltration characteristics using minimum field measurements is then presented. The technique uses a single advance measurement for single furrows and the log-normal probability distribution to predict the statistical distribution of infiltration functions across the field based on the measured infiltration curve for one or more fully evaluated furrows. This technique also considers the infiltration curve over appropriate ranges of opportunity time. Simulations using the predicted infiltration parameters demonstrate more accurate estimates of the whole field efficiency and uniformity than those extrapolated from infiltration measurements on a limited number of furrows as sampled in a conventional evaluation.