Laserfiche WebLink
<br />L.,... <br />,.....,01 b..... <br />_.... <br />-..'"''' <br />_"0',. <br />-...." <br />..'\:1... <br />_...... <br />.-. <br /> <br /> <br />I <br />I <br />, <br />I <br />- , <br />-- <br /> <br />MountaIn Snowpack <br />as of April 1, 2005 <br />....- <br />-' <br />..,.. <br />......00 <br />."c.,.. <br />_10.,. <br />.",.. <br />_to... <br />... <br /> <br /> <br />, <br />, <br />, <br />-, <br />" <br /> <br />Mountain Snow pack <br />as of April 1 , 2004 <br /> <br />" <br />f ~,' <br />. -II <br />,_ \ 'i <br />--"'\-.t <br /> <br />Figure 2. Snowpack expressed as percent of 3D-year average in various sub.basins of the <br />Colorado River basin, as of 1 April 2004 (left) and 1 April 2005 (right). Data are from SNOTEL <br />sites operated by the National Resource Conservation Service (NRCS) and figures are from the <br />NRCS National Water and Climate Center. <br /> <br />2.3. Use ofSNOTEI.lln..'Cipitation Data to Estimate Snowpack Ablation <br /> <br />To estimate snowpack ablation, we compared November I to April I accumulated <br />gauge snowfall at 16 SNOTEL sites against April I SNODAS SWE there. November I <br />is a nominal datc after which most precipitation falls as snow rather than min. The 16 <br />sites were from Colorado, Utah, Wyoming, and Arizona, at dispersed geogmphic <br />locations and elevations. Interestingly, thc SNOTEL pn.'Cipitation.to-SNODAS SWE <br />ratios were 1.22 in 2004 and 0.89 in 2005, respectively. The latter ratio, indicative of <br />greater snowpack water than precipitation, might reneet a problem with gauge <br />precipitation measurement or the arbitrary November I start date of the snowfall season. <br />There is signilicant gauge under catch of snowfall in wind-exposed locations that might <br />explain much of the problem. The bottom line is that we cannot tmst the SNOTEL <br />gauge-measured seasonal precipitation to estimate seasonal melt of the snowpack. There <br />is one othcr option to estimate melt. The SNODAS model outputs snow melt at the base <br />of the pack. We post daily melt products on our Colorado web site6. To generate <br />seasonal melt, we would have to sum the daily values over an entire winter. "Ibis is <br />beyond the scope of the current study but may be pursued later. <br /> <br />5 <br />