Irrigation Efficiency Crucial for Ensuring Sustainable Water Resource

Waleed Ali and Daniel Wagenaar - Murrumbidgee Irrigation and Xylem Water Solutions , 17 December, 2020

Irrigation network efficiency is a fundamental component in ensuring a sustainable water resource. It has become more pertinent with the expansion of irrigation areas, ageing infrastructure and climate change. There are a number of aspects that drive an efficient irrigation network, with water resource planning, maintenance programs and flow monitoring networks forming the key components. The knowledge of water lost due to evaporation, leakage or unauthorised abstractions as a result of a well-designed monitoring network is invaluable, as this assists in decision making processes for future expansion or maintenance of the irrigation network.

The ability to accurately monitor flows within irrigation networks, even under stress during peak demand can highlight structures that exceed their hydraulic limit during certain flow conditions. Most importantly, it gives both the customers and operators the confidence that the flow and associated billing from water releases are accurate.

Murrumbidgee Irrigation (MI) implemented a validation process to review the flow monitoring network at strategic points over a three-month period. The process consisted of temporary installation of SonTek SL1500-3G acoustic Doppler instruments at nine predefined measurement sites. An index velocity rating was developed that is based on velocity measurements from these instruments and discharge measurements from RiverSurveyor M9 Acoustic Doppler Current Profiler (ADCP). The index velocity rating is robust against variable backwater conditions, normally encountered during peak demand.

The process implemented by MI to automate the data collection, audit and index velocity rating development is sophisticated to ensure accurate assessment of the flows. The SL1500-3G instruments send velocity and diagnostic data at fixed sample intervals via serial output over TCP/IP to an SQL database. The ADCP discharge measurements performed during the week are processed at the office, from where the information is captured into custom designed application. The application compares the data captured from the discharge measurements against the velocity data stored on the SQL database. Index Velocity rating is developed based on information entered, from where a detailed assessment is performed to determine if the index velocity rating is valid. During the verification period, field personnel have the option to request that no flow changes are made during the discharge measurements. This ensures that the flow in the channel is relative stable during the discharge measurements.

The flow results from the index velocity ratings are used to further improve the existing stage-discharge relationships at each of the flow measurement sites selected within the irrigation network.