By Guest Writer Phil Brink, Consulting Coordinator, Colorado Cattlemen’s Ag Water NetWORK (agwaternetwork.org)
If farmers and ranchers use more efficient irrigation methods, won’t they use less water? This is a common question which stems from confusion between the terms ‘efficiency’ and ‘conservation’.
Conservation means using less water. Efficiency refers to the amount of water applied compared with the amount of water used by plants. Greater irrigation efficiency does not mean lower total crop water use. If 100 acre-feet of water is applied to a field over a growing season using flood irrigation, and the crop’s consumptive use is 50 acre-feet, then the system is 50 percent efficient. The remaining half evaporates from the field surface or runs off the end of the field or percolates down below the root zone. Surface and subsurface flows leaving irrigated fields can recharge groundwater, support wetlands, and be used by others downgradient – including other farmers, municipalities, and domestic well owners. This practice enables multiple uses of water within basin systems as water is diverted and then some of it returns back to the river, augmenting mid- and late summer flows and enabling additional diversion and use.
Now, back to efficiency. If the same field upgrades to a sprinkler which is 85% efficient, edge-of-field runoff is eliminated. The rancher needs to divert less water from the ditch but there is also no field runoff. There is no actual reduction in water used by the crop. It still uses 50 acre-feet. So the irrigation system is more efficient, but there has been no net water conservation.
Read the rest of Phil’s article here: https://www.agwaternetwork.org/Media/Documents/Water%20and%20Ag_Valuing%20our%20essential%20resources_April%202020_Part%201%20and%202.pdf
And stay tuned next week as we explore more water issues in Rio Blanco County!