In 2017, the City of Kelowna began the process of separating agricultural and domestic water systems as part of their Integrated Water Supply Plan. The plan calls for an integrated water system that provides the lowest cost, city-wide solution for drinking water, that also maintains agricultural interests.  

The first phase of the work involved the design and construction of a new potable water system for water users in Southeast Kelowna. The Southeast Kelowna irrigation system would continue to provide water from Hydraulic Creek, but now only to agricultural users and for fire flow in the area. This would be a major change to the way the system operates, and the City realized that they needed to be able to predict the operation of this new system to prevent any potential issues before the system was fully transitioned. 

Water Engineer, Robyn Sherstobitoff and Process Mechanical Engineer, Matt Lozie worked with the City to build a new distribution model for the irrigation system, using the Innovyze InfoWater software. The City’s existing geographic information system (GIS) was used to complete infrastructure mapping. Water demands were created based on allocation data for agricultural users in the area and actual usage data from previous years. Robyn tells us, “We verified the model against actual field data to confirm its accuracy with respect to real conditions.”

As the future system usage would differ significantly from the historical usage due to the removal of domestic users from the system, historic data alone was not sufficient for demand projection. Instead, Associated Engineering used the irrigation allotments, based on property size and soil type, to estimate a total instantaneous allocated demand. Historical data from the system was then used to estimate a maximum day demand for the overall system, from which the established domestic demand was subtracted.

As scenarios when every customer is using their irrigation allotment simultaneously does not typically occur, the demands were then scaled and applied to the model nodes. The scaling factor used to complete this exercise was dependent not only on the historical data versus the water allotments, but also an evaluation of the location of the nodes in the system.

Matt says, “Model nodes at or near system dead ends were assumed to use their full irrigation allotments during maximum day scenarios. The remainder of the demand was distributed across the rest of the system at a reduced scale.” 

As the City continues to move forward with the Integrated Water Supply Plan, the completed model gives the City the ability to predict future needs for the system and evaluate options for supplying potential new agricultural users. The City is also able to evaluate fire capacity and redundancy in the system and identify any areas of the system that may see potential water quality issues due to reduced demands.

The model is now being used to complete conceptual design of planned upgrades to improve system performance and provide additional reliability. Robyn says, “This work results in a valuable tool that the City can continue to use for years to come.”