Mid March Winter Snowpack and Implications for Wildfire Fuels
|New Mexico is nearing the end of the season for accumulating snowpack. This feature will illustrate how our current meager snowpack compares to recent years and how variations in the snowpack affect the grass fuels. Documentation of two areas will be included - the Sandia and Jemez Mountains.
Snowpack is important to New Mexicans for many reasons - water runoff for irrigation, cattle grazing and ski season certainly come to mind. Snowpack also has distinct effects on the duration and intensity of the fire season. Duration, abundance and composition of the snowpack all have direct impacts on the fire season. For example, an abundant, heavy/wet snowpack over a long duration typically shortens the fire season. A snowpack that exists longer into the spring period doesn't allow surface fuels to be exposed to the intense New Mexican sun as quickly. Once the abundant snowpack melts, surface temperatures increase promoting adequate greenup because soil moisture levels tend to be higher. This greenup lessens the intensity of the fire season. A heavy/wet snowpack over a longer duration also tends to compact or flatten surface fuels such as grass and leaves. Surface fuels that are not suspended in the vertical or upright generally reduce the speed of a surface fire and typically lessens the intensity.
Conversely, a below normal snowpack that is lighter in composition and shorter in duration tends to lengthen the fire season. Surface fuels are exposed to the spring sun earlier in the season and dry out more quickly. Spring greenup is less and sporadic. Previous grass growth is suspended in the vertical and more readily available to spur on fast-moving and intense wildfires. Therefore, snowpack and its effects on the fire season change year to year. New Mexicans need to be aware of these changes.
State Highway 536, otherwise known as the Sandia Crest Road, is located a few miles east of Albuquerque New Mexico, and is shown in white on the map to the right. This road starts at an elevation of 7,000 feet and continues up to 10,600 feet near the crest of the Sandia Mountains. The distance from the start of the highway to the end of the road is only 5.5 miles as the crow flies. This road provides a wonderful example of how vegetation and meteorology changes with elevation. For several years, photographs have been taken at various elevations to document snowpack in the varying environments. Locations (and elevations) at which the photos were taken are marked by the open circles on the map.
|At the east end of the road, around 7,000 feet, grass, shrubs, and smaller timber (typically piñon/juniper and ponderosa) dominate. By 8,000 feet, the road enters an area of heavier ponderosa pine timber, although locally drier or more exposed aspects can remain in a shrub or grass component. As the climb continues, the ponderosa pines give way to a mixed conifer forest of spruce and Douglas fir. Douglas fir needles are shorter than those of the ponderosa pine. Green-up along this highway during the spring and summer months occurs at different times, while snowfall and rainfall can be quite variable from lower to higher elevations. Photos for this feature were taken by Brent Wachter, and are used to illustrate the current snowpack as well as differences in snowpack and fuels from year to year at different elevations along this highway. Photos since 2010 are shown below, for locations at 8,000 ft (left column) and 10,000 ft (right column).|
|8000 ft||10000 ft|
|Currently (2013) the snow pack in the Sandias is well below normal and snowcover was absent at this 8,000 foot location. Grass is suspended in the vertical as a result of the light snowpack.||At 10,000, while snow cover is evident, the snowpack is the least abundant when compared to the previous three years (see images directly below).|
|For March of 2012, snow is visible in the background and the grass appears flat. There must have been enough heavy/wet snow prior to this time to compact the grass during the course of the winter.||
At the higher elevation, snowpack is visually more abundant in this picture but the depth is still less than what was observed in 2010.
|For 2011, snow is visible in the background and the grass is somewhat suspended in the vertical. This indicates a lighter overall snowpack.||A La Niña event reduced the snowpack greatly from what was observed in the previous year (2010) but 2011 snowpack was still a bit deeper than the 2013 snowpack during the same time frame.|
|We need to go back to 2010 to find widespread snow at 8000 feet. The depth of the snow suggests that the grass is most likely flat.||In 2010, an El Niño event was in place, and winter precipitation provided an abundant and long duration snowpack. Note that this picture was actually taken in early April - no March image is available.|
|Snowpack and Fuels|
The pictures below were all taken at 8000 feet in the Sandia Mountains at the same location and nearly the same time frame. The photos illustrate year to year changes in grass compaction. How much grass grew the previous year is not the most significant factor for wildfire fuels. What is important is whether or not the grass has been significantly compacted by a heavy and long lasting winter snowpack. Come spring, the compacted grass will be much less available for a surface fire spread.
In the case of 2013, the preceding grass fuel loading is below average in many locations due to the lack of greenup during the previous year's growing season, BUT the snowpack was light. The net effect is a 2013 grass fuel bed that is upright and, therefore, more available for surface fire spread - it essentially has the highest available loading to fuel wildfires than other recent years illustrated in this feature.
It should be noted, however, that certain grass species can be flattened or compacted by snowpack, then later able to "stand back up" under the right drying conditions in the spring - analogous to static electricity effects on the hair on your head. A finer hair will stand up more readily and grass behaves in a similar manner. A thicker stem that has been broken cannot stand back up. Flatter stemmed grasses vary on their ability to stand back up. Take note of the grass type in your neighborhood.
|In 2010, blanket of heavy, wet snow existed late into March across the Sandias. This snowpack has compacted the grass as shown in the photo to the right.||In this close up of a snow free area, notice that the grass is flat to the ground due to the heavy, wet snow. The grass is a mix of thin and flat stems.|
|In 2011 (left), grass is much more suspended - although some compaction is evident within the broad stemmed species.|
|Grass and oak leaf litter was fully compacted in 2012 because the snowpack was wetter or heavier in weight at this particular location and it lasted longer into the spring season.||The same location in 2013 shows very little impact by the winter snowpack with thin, long and thick stemmed grass species still upright. Some of the broad stemmed species exhibit some flattening. The grass fuel loading may have been below normal at this particular location leading into the winter season, however, the total fuel bed is upright making it available for wildfires to spread quickly through.|
State Highway 4, which runs from San Ysidro to White Rock or Los Alamos, winds its way through the southern Jemez Mountains. Similar to the Sandia Mountains, fuel and weather are drastically different based on elevation changes. San Ysidro is at 5500 feet and White Rock is around 6500 feet but the road climbs as high as 9000 feet near the Valle Caldera National Preserve. Photos were taken the past several years to illustrate vegetative and snowpack changes by season. Locations (and elevation) at which the photos were taken are marked by the open circles on the map.
|At the south end of Highway 4, grass/shrub and cottonwoods dominate the fuel picture. The highway then quickly transitions into a Piñon and Juniper fuel component combined with grass and some shrubs. Ponderosa pine, fir on the north and east aspects combined with open areas of shrub and grass dominate the landscape between Jemez Springs and Los Alamos. A return to a dominant Piñon and Juniper fuel component occurs between Los Alamos and White Rock along the north end of the highway. Photos taken since 2011 are used for this feature and illustrate the 7700 ft (western location, left hand column) and 8700 ft (eastern location and right hand column) elevation levels along this route.|
|7700 ft||8700 ft|
|In mid March of 2013, grass is clearly vertically suspended.||At the higher elevation, 2013 snowpack is broken and thin but still more abundant at this point compared to 2011.|
|In 2012, grass has been flattened significantly.||Snowpack visually abundant compared to the other years.|
|Grass is suspended and looks to be more in the vertical than in 2013 during the same time period. The grass fuel loading also looks to be higher, and this relates to the active green-up New Mexico experienced in 2010.||The scant 2011 snowpack is evident, with brown spots visually showing up along the surrounding higher peaks in the background.|
Fire managers in New Mexico are quickly trying to get their pile burn projects completed in 2013 before the snowpack fully erodes away. Snowcover around a pile burn helps reduce the amount of fire creep away from the piles, both during the day and overnight hours following ignition.
|In this photo, smoke marks the location of a distant pile burn being managed by the Santa Fe National Forest in the Jemez Mountains. Highway 4 is on the left hand side of the photo. Notice the snow evident along the ridgetop.||Adequate snowcover currently exists around these piles in the Santa Fe National Forest but that won't last much longer.|
|To conclude, the lack of snowpack in terms of duration, amount and composition has resulted in impacts at many locations thoughout New Mexico. Drought may have limited the growing season last year and the grass fuel loading in many areas is below normal, but whatever grass that did grow is generally upright and available to fuel wildfires. Snow is also eroding away quickly due to the spring winds and the sun's warmth. The wildfire season has started across the low and mid elevations of New Mexico. Fire Managers are adjusting their prescribed burn practices. New Mexicans, especially in the fuel transition zones between the higher elevation timber and dominant grass/shrub lands, should be aware and stay fully alert during warm/dry/windy days!|