National Integrated Drought Information System: Upper Colorado Basin Pilot Project’s ‘Summary of Weekly precip and water supply’

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Henry Reges has graciously allowed me to post his notes from yesterday’s webinar:

Much of the Upper Colorado River Basin received very little moisture last week, with only spotty areas of precipitation in the Yampa-White and Green River basins and northern Utah. For the month of May, the majority of precipitation was focused over the northern region of Colorado and along the Utah-Wyoming border. After a wet start to the water year, the south has quickly begun drying out. Small decreases were seen in the water-year-to-date precipitation percent of averages from last week with the driest areas showing up in northeastern Utah and western Wyoming. Temperatures for the last week were near average to slightly cooler than average for most of the UCRB. However, since the average temperature this time of year is quickly warming up, much of the snowpack is melting and streamflows are again picking up. Less than 30% of the streamgages in the area are reporting below normal (below the 25th percentile) 7-day flows, compared to nearly 50% last week. Much below normal flows are mainly seen in Wyoming, where even though much of the snowpack has melted out, the very low peak snowpack values resulted in only minor increases in streamflow. Minor improvements in northeastern Utah streamflows were primarily the result of drainage from the south slopes of the Uinta mountain range, but are not expected to have any long term impacts, and streamflows will probably deteriorate again in the coming weeks. Reservoir levels continue to rise with the meltoff. Reservoir operators in the Colorado basin have coordinated their releases to match the natural peak flows in order to boost streamflows and mobilize sediment, as there is now extra water and no more concern that the reservoirs will not fill for the high demand season.

The forecast for the region is pretty quiet with some chance of precipitation in the next 1 to 3 days. The next weather system to move through looks to drop most of the moisture over western Wyoming with some chance in the plains of northeastern Colorado. After this, conditions will dry up as the area will be dominated by zonal flow with a building ridge to the west.

After looking at percentile rankings of snotel precipitation across the basin, one of the areas of biggest concern is northeastern Utah, which has been in D0 for quite some time. The percentiles suggest that some of the region could possibly be in D1, though it was recommended to defer to the U.S. Drought Monitor author (and other experts in the region who were not on the call) on any possible changes that should be made to the region. Due to continued poor conditions in the Green River basin (and feedback from local irrigators), Wyoming experts on the call wish to remain status quo for the D2 in the region, with the possibility of adjusting the D1 in extreme southwestern WY to better reflect conditions there, though they also defer to the Drought Monitor author on that particular change. Due to the persistent drying occurring in the four-corners region, the suggestion by the Drought Monitor author to expand and connect the D0 in Arizona, New Mexico, and Colorado, was met with no arguments. The author did suggest though that most of these changes would be focused on NM, so it’s possible that the expansion in southwestern Colorado will not happen for this week’s map.

Meanwhile, American Rivers has designated the Upper Colorado River the sixth-most endangered river in the U.S. Here’s a report from The Denver Post. From the article:

New water-diversion projects could sap the life from the river — threatening fish, boating and long-term water supply for the region, the group said in releasing its annual American’s Most Endangered Rivers report. The river begins in Rocky Mountain National Park and flows southwest toward Utah through a region inhabited by 93,000 full-time residents. “The key to a reliable and predictable water supply is a healthy river,” American Rivers president Rebecca Wodder said.

More Colorado River Basin coverage here.

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