Shallow groundwater within the Shepparton Irrigation Region (SIR) is accessed from discontinuous shoestring sands and is more commonly constrained by seasonal hydrological loading than competition between users. Under the Basin Plan, the Water Resource Plan must detail how the annual volume of groundwater take will be determined. The Basin Plan requires that the determining method be fit-for-purpose and there are provisions for flexibility in the approach. This flexibility enables consideration to be given to cost effectiveness. The discontinuous nature of the sand aquifers means that the resource cannot be realistically considered as a single ‘consumptive pool’. Additionally, there are high operational costs associated with area-wide metering. Within this context, work was undertaken to develop a methodology for estimating and reporting shallow groundwater extraction in the SIR.
Work completed in 2014 assessed costs and suitability of various methods of usage estimation. This work concluded that metering a subset of bores would be a suitable method as a means of substantially reducing cost, whilst maintaining a reasonable level of certainty in regional scale estimates of take. Historical metered usage data was available across the SIR. Subset sites were selected that were compliant with Goulburn-Murray Water safety criteria and largely operational, recognising that this would bias the sample towards higher levels of take. A realistic match between estimated and historical metered usage was achieved by extrapolating subset metered take as a percentage of entitlement moderated by linear relationships between shallow groundwater take, and spring rainfall and Deep Lead extraction. The method produced results that were consistent with historical levels of take albeit a slight over-estimate of the actual volume (a conservative approach to reporting).
This presentation explores the technical approach employed and demonstrates that metering in the SIR can be met with a fit-for-purpose, cost effective method as an alternative to area-wide metering.