This past spring year was particularly mettlesome for water managers seeking to balance water supplies and demand in the Upper Gunnison River Basin.
Although there currently are no shortages of water this year, the vagaries of last winter, from unseasonably warm to unseasonably cold, may hold some warning about future water forecasting for regional hydrologists, cautioned Greg Smith, Senior Hydrologist for NOAA’s Colorado River Basin Forecasting Center in Salt Lake.
The art of forecasting water supplies has as one of its main tools historical data and the rapidity of changes in the Earth’s climate recently has been handcuffing the best efforts of forecasters, said Smith during the last week’s Aspinall Unit Operations meeting in Grand Junction.
The quarterly meetings, sponsored by the Western Colorado Area Office of the Bureau of Reclamation, offer a look at what hydrologists and weather forecasters portend for future water supplies in the Upper Colorado River Basin.
“2017 was challenging,” Smith said when addressing the year’s weather. “When we go from one (weather) extreme to the other, as we have seen this year, that makes our job even more difficult.”
A pair of linked examples was the unusual warming in March, which caused some very early low-elevation melting and ensuing runoff, followed by an unseasonably cold May (“February-like temperatures,” Smith said) which drastically slowed that runoff and caused concern among water managers wondering when and if the runoff would begin anew.
All this was tied to the near-record snows of late December and January, which overwhelmed some of the region’s remote-sensing SNOTEL sites.
“Several sites quit reporting and we thought they had broken but in reality they had been completely buried by the snow,” Smith said. “In March, a lot of the sites (in the Upper Gunnison Basin) recorded their highest totals on record … some of which go back 39 years.”
Are the aberrant weather patterns of last winter just that or are they indications of a new normal that eventually will become part of the historical data?
Smith isn’t sure.
“Well, we try to use long-term records in making our (water-supply) forecasts, at least 20 years or more,” Smith said. “So even these recent weather patterns will take a while to become part of the permanent record.
“And we’re certainly aware of weather changes. Even a few degrees one way or the other affects snowmelt and eventually water supplies.”