Channel Seepage, Water Savings and Water Efficiency
Abstract
A study to assess the potential for water recovery from reduced channel seepage losses and improved accuracy of flow measurement in the West Corurgan Private Irrigation District (WCPID) was commissioned by the Murray–Darling Basin Commission through its Living Murray Development of Infrastructure Projects Program.
Seepage and leakage losses were estimated from several large scale channel pondage tests. These tests fine-tuned previous seepage rate estimates from an overall average of 14.96 mm/d to a range from 1.7 to 4.4 mm/d for four major soil groups. Application of these rates to the whole system resulted in an estimate of seasonal channel seepage losses of 2,300 to 2,750 ML. Leakage losses were estimated in the order of 175 ML, while net evaporation losses
ranged from 1,500 to 3,100 ML. System filling accounted for 1,600 to 2,000 ML. The total water entitlement of WCPID is 80,828 ML.
WCPID pumps water from the River Murray near Corowa (NSW), lifting it approx. 12 metres into the channel system to enable irrigation supply to farms by gravity. Flow measurements occur at two locations: the river pumps and at the Dethridge Wheels that deliver water to the farms. Both the pumps and a selection of Dethridge wheels were calibrated to refine the estimates of system losses.
A detailed water balance assessment of four irrigation seasons with allocations of 43%, 90%, 102% and 33% showed potential water savings of 1,600 to 3,000 ML per season through more accurate flow measurement at the pumps, 2,000 ML/season through optimised channel operation, flow control and measurement in the channel system, and on-farm water savings of up to 30% of current applications. On farm water savings would be required to off-set reduced supply to irrigators when water savings at the river pumps are realised.
Authors
Willem F. Vlotman, Peter Wallis, Leanne Wilkinson, & Stephen Harding