Water conveyance and on-farm irrigation system efficiency gains in southern Alberta irrigation districts from 1999 to 2012

Efficiency gains from on-farm irrigation system upgrades and canal rehabilitation in southern Alberta irrigation districts are influenced by weather variability. The Irrigation Demand Model was used to estimate differences in on-farm demand and conveyance losses based on irrigation district characteristics in 1999 and 2012 using weather data from 1928 to 2012. Monte Carlo simulations were subsequently performed to determine the magnitude of potential efficiency gains at different chances of exceedance. Changes in irrigation systems and water conveyance infrastructure reduced gross demand by 74 mm from 1999 to 2012, with a 55-mm reduction in on-farm demand and a 19-mm decrease in conveyance losses at a 10% chance of exceedance. Reductions in gross demand on a volume basis from 1999 to 2012 ranged from 170 to 200 million m3, even with about 30,300 ha of irrigation expansion. Conveyance loss reductions were stable at about 50 million m3, so 70 to 75% of the potential water savings were achieved through reduced on-farm demand. Mean seasonal naturalized flows available for use in southern Alberta from 1912 to 2009 ranged from 2.08 billion m3 in high-demand years to 3.95 billion m3 in wet years. Gross demand based on irrigation district characteristics in 2012 varied from 1.73 billion m3 in wet years to 2.83 billion m3 in high-demand years. Additional gains in efficiency from on-farm irrigation system upgrades and rehabilitation of conveyance infrastructure in the future will help mitigate the increased risk of water scarcity as irrigation districts expand with current licensed water allocations.