An assessment of surge-irrigation in the Burdekin : Final report CSR35

Abstract

Furrow irrigation is the natural choice for sugarcane. It is relatively cheap to operate and generally not capital intensive, However in operation furrow irrigation has distinct limitations. It is generally inefficient in its use of water with 50% utilisation being a typical figure (Stewart 1988). With pumping costs being greater than $2 per tonne cane and QWRC water charges be i ng $32 per mega 1 i tre for farms on channe 1 supp 1 y, there is a need to increase efficiency in order to save moneY,conserve water resources and guard against rising water-tables and salinity. With furrow irrigation the furrow is both the source and the sink of irrigation water. The advance of the water down a dry furrow is typically much slower than the recession of water in a wet furrow except for short or flat furrows which are blocked. Inevitably the upper reaches of the furrow receive more water than lower down . To ensure adequate watering of the lower reaches irrigation water is often allowed to run off to waste for some considerable time. Surge irrigation is the application of irrigation water in pulses rater than continuously . If the off-phase is sufficiently long for the surface soil to dewater, it has been found (see Walker and Skogerboe, 1987) that when irrigation water is reapplied it rapidly advances over the previously wetted section such that less water is required to complete the advance phase of the irrigation. A more rapid advance gives a more uniform distribution of water. Because the irrigation on-time is only a portion of clock time (typically half) it allows better control of run off because irrigators have more time to interact with it.