Current Theme: Waterworks
	Snowpack report - Niwot Ridge - April, 2005 Mark Losleben - CU INSTAAR Research Staff

The following snowpack conditions on Niwot Ridge have been reported by Mark Losleben for April 2005. Select here for more information about these snowpack reports

Moist, spring greetings from Niwot Ridge!

Snowpack conditions in Colorado and the western United States continue in the same pattern begun at the start of this snow season; wet in the south, dry in the north, with both C1 and South Platte basin snowpacks not clearly at their peak yet.

The C1 snowpack is at a seasonal maximum today, 30 April 2005, and it is still snowing! There are 12.875 inches of water (SWE) in the 49" snowpack. This is 97% of the manually measured record. This average condition is expressed in several ways: about one half of the time, March is greater than April SWE, and this April SWE ranks 15th out of 24 years. Other comparisons: April 2002 SWE was 0.0, and the mid-May SWE was greater than this value in 1995, 97, 98, 99 (it could happen again this year if the present weather pattern persists for two more weeks!).

This bodes well as the snowmelt season begins, for the soil moisture levels have been at or near field capacity (maximum) for about a year in this area, meaning the snowpack can filter more directly into streams and rivers without making up soil moisture deficits first. It also suggests that the fire season could be a little shorter this year because it will start later than in many recent past years.

According to the Snotel network, C1 (Niwot) SWE is 12.6" (103% of average), and cumulative winter precipitation is 20.4" (102% of average). These values are in good agreement with the manual records for this time of year (Snotel instrumental artifacts are often at a maximum now).

Snotel also reports the South Platte basin snowpack at 86% of average, and the winter precipitation to date also 86% (Snowpack Index, or SI, =1.0). For perspective, this is 112% of last year's value on this date, and is the peak value so far this year, making it latter than the average peak date of April 23. This also ranks the South Platte roughly in the middle of Colorado basins (fourth of eight) on a percentage basis. The San Miguel/Animas/Dolores/San Juan basin group is in first place (wettest) with 143% of average SWE (129% precipitation), and the Yampa/White is the driest with 69% of average SWE (84% precipitation).

The western US as a whole, is still wettest in the south, and driest in the north, and the departures from average are great. Washington SWE is only 22% of average (69% precipitation), Oregon is 36% and 66% (SWE and precipitation, respectively), while New Mexico is 159% (132% precipitation), California Great Basin sites are 158% (111% precipitation), and Utah is 141% (136% precipitation).

Notice that the areas with average, or greater, SWE also have SI's greater than one (more water stored in the snowpack for slower release through the season, compared to normal), and those with well below average snowpacks have SI's less than one. This is true on spatial scales from the local to state levels.

So, overall, the northwest is very dry, and the southwest reservoirs may get a drought reprieve this spring. Summer precipitation can moderate this picture, so there are still interesting times ahead!

There will be one more snowpack report (mid-May), and the full manual snowpack record follows.

Cheers! Mark

                      Sno Tel Data  Niwot Ridge, C-1
                      Snow Water Content (inches)
                      Values are for the end of given month
                      except as noted for May and June


     Season     Dec      Jan      Feb      Mar      Apr     May            Jun 
      81/82    4.75     10.5     11.75    15.5     14.9    12.0   (17th)
      82/83    3.63              4.75     12.75     17     11.75  (30th)
      83/84    12.6     13.25     15      18.9     20.75   
      84/85    3.75     6.25      8.5     10.25    8.75
      85/86     6.5      7.5      14      15.38    17.5
      86/87    6.25     8.75     11.25    12.75    11.75
      87/88     6.5      9.1     12.4     15.75    14.5
      88/89     5.5      7.6      11      10.25     5.6
      89/90     6.5     9.25     10.75    16.1     16.5
      90/91      3        5       7.1     9.38      10
      91/92    6.65     6.75      8.5     12.25    10.25
      92/93    5.75     6.75     10.75     14      15.875
      93/94    7.125    9.063    12.25    13.25    13.25     2.5  (18th)
      94/95    2.625    3.925     7.0     10.125   16.75    17.0  (22nd) 12.375(13th) 19.75(30th)
      95/96    7.50     12.00    17.5     20.375   18.75     6.125 (15th)
      96/97    8.75     12.625   15.125   14.625   20.375   18.0   (15th)
      97/98    7.0625   10.0     10.125   12.875   17.25    12.875 (15th)
      98/99    3.25     6.625     8.375    9.125   14.125   14.25  (15th)
      99/2000  3.5      7.5      10.625   12.375    7.625   
      00/2001  4.375    5.375     7.125   10.00     9.125
      01/2002  2.625    4.25      6.19     7.563    0.0
      02/2003  4.00     5.25      8.5     16.75    14.375   11.44 (15th)
      03/2004  2.75     4.813     7.75     7.875   10.125    3.69 (14th)
      04/2005  4.875    7.7       9.5     11.625   12.875

     Average   5.409    7.819    10.242   12.908   13.25