Bracing for More Drought in West

 

by Helen Neville

After four years of drought, people across the West are bracing for another horrific summer.  When gaged over the whole spring, much of the West has seen <50% of average precipitation this year (below, top figure), which seems bad enough.  But in the last week of March, almost the entire region hit an unbelievable 5% or less of normal precipitation (below, bottom figure).  California, for instance, usually has feet of snow storing water in the Sierra Nevada Mountains this time of year.  Instead, the state has been the consistent bulls-eye of the drought, and bare ground in the Sierra peaks this year already led to several ski area closures – in February.  Last week’s dire precipitation tally finally prompted the state to impose mandatory water restrictions for the first time in the state’s history. 

 

 Percent of average precipitation for Jan-March (top), and for last week of March (bottom), 2015:  http://www.wrcc.dri.edu/anom/

To the east, Coloradans are experiencing a slightly different twist to how drought is playing out.  This region has long experienced a snow-on-dust phenomenon caused by poor soil management that is further exacerbating climate-change-induced drought, in a somewhat vicious cycle:  both soil erosion and drought cause dust storms, which in turn blanket snow in a dark-colored film, which causes the snow to melt faster, only worsening the drought and erosion.  Given early agricultural practices in the state, this dust issue has been happening in Colorado for over a century, with an estimated 5-fold increase in ‘natural’ dust loading already occurring and shortening snow-pack duration by the late 1880s (1).  This year, despite a 10 year dust blanket, spring so far has brought fewer dust storms (2) in what could be taken as a sign of respite.  But not so fast:  the unusually high temperatures are causing the snow to be warmer, which will likely lead to more dust later.  That is, even snow can be cold or warm, and currently Colorado’s snow temperature is already right at the transitional cusp of turning into water.  This will lead to an early run-off, which means less water in streams over the summer.  Combine this with the lack of precipitation observed in the last month and Colorado is gearing up for some bad dust storms in April, the month where dust storms usually peak (2).  And repeat.

To make matters worse, snowpack across the West is predicted to keep declining in the future.  A recent scientific paper, published in the peer-reviewed journal Water Resources Research, projects continuing declines in the annual Snowfall Water Equivalent across the West for decades (3).  None of this bodes well for fish, and managers I work with in California and Nevada are already bracing for population losses and the potential need for emergency salvages, where that is even possible.  

This year will certainly test the waters for many of our beloved fish populations, making TU’s restoration work to improve stream habitat, flow and water temperatures all the more important.

Helen Neville is a research scientist for Trout Unlimited.

1. Painter, T.H., et al., Response of Colorado River runoff to dust radiative forcing in snow. Proceedings of the National Academy of Sciences, 2010. 107: p. 17125–17130.

2. Colorado's snow is dust-free for the first time in a decade, but conditions are still prime for snowmelt and summer drought. HCN article.

3. Lute, A.C., J.T. Abatzoglou, and K.C. Hegewisch, Projected changes in snowfall extremes and interannual variability of snowfall in the western United States. Water Resources Research, 2015. 51: p. 960-972.

 

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