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DRAFT IRRIGATION SEASON PROTOCOL Irrigation Season The irrigation season begins when the irrigation of crops aids in the growth and greening thereof, or likewise ends when irrigation no longer aids in the growth and greening. The irrigation season established herein is presumptively set to mirror the season during which water users irrigate growing crops and is designed to provide guidance to water right(s) holders for the use of their water but does not allow irrigators to expand the current use of their water right(s). Irrigating growing crops includes historic practices such as, but not limited to: flushing ditches with water, initiating diversions, germinating volunteer seed and building soil moisture (i.e. filling the soil moisture profile). There are many variables that can affect the start of irrigation season including climate, weather, snowpack accumulation and snowpack melt. These variables are not predictable from year to year, so the Division Engineer may assess conditions and make adjustments to the start and end of irrigation season accordingly. The statutory definition of "beneficial use" sets the limits for these practices, as determined by the Division �! Engineer. §37 -92- 103(4), C.R.S. (2010). Irrigation season shall begin Aril 1 nd "en October 31 of any given ro J�Lg year. It is within the Division Engineer's discretion to modify these presumptive dates t make the irrigation ca season longer or shorter, or to make any other modifications related, to irrigation seas n that he /she deem appropriate. A water user may divert water for irrigation purpose either before April 1 or after bpEcItober 31, however this office will not honor a call outside of the April 1 through ctober 3 time frame unless a modification of these dates has been made by the Division Engineer for that given year. Within the timeframe of priI` hrough ctober 31 the Water Commissioner will only honor a call when water can be beneficially use or irrigation purposes without waste. It is implicit that, along with vested rights, there shall be optimum r c utilization of the water of this state and that such right to water does not give right to waste it. �Vlu to Factors that the Division Engineer may consider in modifying these dates are: • Daily average temperature. Once the daily average temperature drops below 45 °F for several days, plants, specifically grass hay, stop consuming water. Or, conversely when the daily average temperature rises above 45 °F for several days, plants begin to consume water. • Daily minimum temperature. Once the daily minimum temperature drops below 28 °F, plants stop growing. • The demand for water by plants drops off dramatically after harvesting thus questioning the need for prolonged irrigation late into the irrigation season. • As mentioned above, filling the soil moisture profile is considered a beneficial use which can occur in both the spring and fall months. This however raises the question of how much water is needed to fill the soil moisture profile? Assuming the rooting depth of grass is 3 -feet and 2- inches of water per foot of rooting depth is needed to fill this profile, a total of 6- inches of water is needed. So, by way of example, if someone wanted to irrigate 100 acres of land in the fall to fill the soil moisture profile before the end of the year and we assume an irrigation efficiency of 50 %, this person would need to apply 6- inches divided by 50% times 100 acres or 100 AF of water. If the ditch they are using is running 4 cfs and we assume a 10% ditch loss, the person should be able to fill up the soil moisture profile in 14 days. • Putting water on soil that is frozen can cause damage to the plants. • Putting too much water on the ground, including filling the soil moisture profile in the fall and then having a wet or heavy snow pack winter, can result in leaching of nutrients from the soil. ly