Streamflow and Precipitation Update: July 2020
It may surprise you to know that the 2020 spring runoff on the San Juan River was a top-five event! While the 2019 spring runoff was the 5th highest since 1979, unfortunately, the 2020 runoff was the 3rd earliest peak date since 1979. The San Juan River peaked at 1930 cfs just after midnight on 5/2/20, which was over a month earlier than last year and 3 weeks earlier than normal.
Our snowpack was ambushed by record high temperatures in late April and early May which obliterated the snowpack at the Upper San Juan Snotel site by May 15th (orange line below). On each day between April 28th and May 1st, the air temperature on Wolf Creek Pass reached at least 60 degrees, which is 14-15 degrees above average. New records were set for April 30th and May 1st (62 and 61 degrees respectively) at the Wolf Creek Summit Snotel site, which has been recording air temperature since 1986. Nighttime temperatures did little to slow the steady snowmelt since evening air temperatures on Wolf Creek Pass remained above freezing during the last week of April and all of May with only 3 exceptions.
Below-average snowpack combined with above-average temperatures meant boating season transitioned to tubing season by mid-June, and by July 1st, tubing season was virtually over. Current streamflow conditions on the San Juan River are actually lower than they were at this time in 2018, which was the worst drought since 2002. The San Juan River dipped below 30 cfs yesterday morning in the absence of measurable moisture (and water diverted into the Park Ditch, which is an irrigation ditch located upstream of Pagosa Springs that can divert up to 60 cfs of river water).
Since April 1st, the Upper San Juan Snotel site has only reported 1.5 inches of precipitation (notice the stalled orange line below) compared to the 9.2 inches we normally receive between April 1st and mid-July (green line below). Since the water year began on October 1st, the Upper San Juan Snotel site is 65% of normal in terms of precipitation (28.1 inches out of the 43.1 inches we normally receive by this time).
Unfortunately, stubborn high pressure has been camped over the Four Corners for much of the summer. Should the high pressure drift further east, we could tap into some subtropical moisture. Until that happens, the static weather is another reason each day feels like Blursday. Soon I'll post the results of some research that I had my Global Science class compile last spring related to how many droughts were been broken in the past. Until then, we wait for the rain!