Boulder County 2021 Water Year: Dry forecasted
February 24, 2021
It seems the old Chinese adage (curse?), "May you be born in interesting times," continues to play on from 2020 into 2021. Atop Covid-19, business pivots from farmers markets and foodservice accounts to increased CSA and online sales. Working outdoors in very smoky conditions last summer/fall, and doing their best to keep farm workers safe from both, Boulder County farmers are now staring down a 2021 snowpack in the Indian Peaks portion of the South Platte River watershed that varies from 63-79% of a 30-year average (NRCS Colorado Snow Survey for Feb 5). These conditions run parallel to an extreme drought in the watershed above 7500 feet (US Drought Monitor for Feb 4, 2021; four categories of drought from D1 – moderate, D2 – severe, D3 – extreme, and D4 - exceptional). Agriculture often deals with multiple challenges but early 2021 is shaping up to be problematic from the perspective of higher temperatures, lower precipitation, and low surface water irrigation supply, the deciding factor for profitability for most farms.
As a positive for snowpack, NOAA's Climate Prediction Center published a one-month outlook for February 2021, showing a 33% chance of above average precipitation. With most of the snowpack contributions deposited in February and March, this is welcome news. Mind you, the 3-month precipitation outlook, presumably for March and April, shows a 33% chance of below average precipitation. Based on the NOAA data, it looks like our chances for increasing the snowpack are mostly in February. And considering the 3-month temperature outlook is about 40% of above normal temperatures, this added factor is not helpful for maintaining snowpack as the irrigation season commences.
With extreme drought in the elevations that collect snowpack and deliver runoff into streams, very dry soil will absorb much of the water melted from snow, holding it and preventing streamflow that would occur if the soil was sufficiently saturated before the snowmelt..
Remember back to 2012? Our last very impactful drought year? Some irrigation canals (ditches) in the southern part of Boulder County did not carry water. Those north of Highway 52 struggled to supply farms and ranches. Currently, the Feb. 4 US Drought Monitor shows the plains of Boulder County in a severe drought (D2).
The earthen bottom of irrigation ditches must be fully saturated with water before the ditches can effectively carry water to farms and ranches. This happens ideally from spring precipitation and not from surface waters released into the irrigation ditch. If the irrigation season starts off with a dry ditch bottom, percolation losses during the first calls for water from farmers can subtract a significant amount of the volume of water sent down the ditch. Similarly, parched field soil requires more water early in the season to fully wet the soil. In a scarce water year, the hardship of not enough water ripples through the system.
Most would be surprised by how much water it takes to produce a crop. With the unit of acre-feet as the basis (the volume of 12 inches of water over the area of an acre, 43,560 square feet, equal to 325,851 gallons), some field crops can be partially irrigated and use as little as 1 acre foot/acre (corn) to produce a crop, while fully irrigated grass or alfalfa can put 3 acre feet/acre to work producing abundant, high quality hay. Vegetable crops generally cannot be partially irrigated and mixed vegetable farms in Boulder County use an average of nearly 2 acre feet per acre.
As Boulder County farmers and ranchers are quick to point out, Mother Nature bats last, and we will have to see if this is another very impactful drought year. For now, the odds are stacked against them for a return to ample irrigation water.