1. Snow Accumulation Reservoir
Wind-blown dust caused by poor soil management is darkening snow which has a significant negative impact on snow melt and accumulation in the Southwestern Colorado Mountains. These mountains include the headwaters for the Rio Grande and other important rivers to New Mexico.
“The research shows that on average, dust landing on the San Juan Mountains melts snow 25-50 days earlier than normal based on 100 years worth of data. And, runoff can decrease by 5 percent because of water evaporating through plants and soil as well as snow turning to water vapor.” Durango Herald, May 12, 2018
Right: Preceding wind events (blue circles) on April 13, 2013 in the Four Corners area (pink lines).
The National Oceanic and Atmospheric Administration (NOAA) explains this little known phenomenon, also sometimes called ‘pink snow’:
“Human activities, such as livestock grazing and building, are breaking down desert soil in the Southwest, leaving dusty particles to be swept up by the wind. The wind eventually drops the dust on the snow-capped mountains of the Colorado River’s watershed. In areas where dark dust has settled, the snow turns pink, red, or brown. Snow dusted with dark particles absorbs more sunlight and melts faster than white snow.” NOAA: Dust on Snow Reduces Colorado River Flow
A 2010 study reveals that “this phenomenon robs the Colorado River of about 5 percent of its water each year. The lost water amounts to more than 250 billion gallons—nearly twice what the city of Las Vegas uses in a year.”
While we don’t have data for the impact of pink snow on New Mexico’s rivers, it is likely that the Rio Grande and other watersheds in our state are also receiving less water. Improved management to facilitate soil health presents an opportunity to stabilize this important resource in the desert Southwest, and prevent the loss of snow melt due to blowing dust.
The Colorado Dust on Snow Program (CODOS) studies the phenomenon. Read more at http://www.codos.org/
2. Evaporation
The New Mexico Climate Center simply states that “potential evaporation in New Mexico is much greater than average annual precipitation.”
“Average annual precipitation ranges from less than 10 inches over much of the southern desert and the Rio Grande and San Juan Valleys to more than 20 inches at higher elevations in the State” while “during the warm months, May through October, evaporation ranges from near 41 inches in the north-central to 73 inches in the southeast portions of the State.”
A 2013 study estimates that New Mexico loses 70 to 109 percent (if irrigated) of rainfall to evaporation, meaning it evaporates back into the atmosphere.
For a 10 inch rainfall zone, somewhere between 7 to all of the 10 inches of rainfall will most likely evaporate.
Improved land management, by using the 5 Soil Health Principles, can significantly reduce evaporation, leading to the retention of additional water and presenting the opportunity to recharge both the Soil Moisture Reservoir (the natural resource with the largest capacity to store water) and the deeper Groundwater Reservoir.
3. Soil Moisture Reservoir
The final opportunity is optimizing the capture of rainfall through the management of soil health. Research shows the important relationship between water infiltration and soil organic matter (OM), cover and aggregation –all of which can be influenced through land management.
According to the USDA-NRCS, the most conservative estimates suggest that for every 1% increase in soil OM soils can hold 20,000 gallons more water per acre.
“Organic matter causes soil to form stable soil aggregates, or crumbs,” says NRCS Soil Health Division Director, Dr. Bianca Moebius-Clune. “With better soil structure, infiltration of water into the soil improves, which allows the entire soil profile to take in and hold more water when it rains. Healthy soil acts much like a sponge, with its ability to absorb and hold much of its volume in water.”
As soil cover increases, so does water infiltration:
- 10% vegetative/litter cover – 73% runoff rate
- 37% cover – 14% runoff rate
- 60-75% cover – 2% runoff rate
Moebius-Clune says there’s good news and a new hope in healthy soil. “By farming using soil health principles and practices adapted to each local production system, such as reducing tillage, growing cover crops and diversifying rotations (including animals), farmers are actually increasing microbial activity, building organic matter and sequestering more carbon in their soil. They are improving its ability to take in and hold ‘water in the bank.’ They’re even creating wildlife and pollinator habitat—all while decreasing risks from extreme weather and harvesting better profits and often better yields.” A hedge against Drought: why healthy soil is water in the bank
For example, a rancher in the eastern part of New Mexico has had these results after practicing the soil health principles for 14 years:
- Water infiltration rates: increased 33%
- Static water levels in the wells: increased 1-2 feet
- Headquarters well flow: increased from ¼ GPM to 1.5 GPM
- At the same time, his stocking rate has doubled from 58 acres per Animal Unit in 2004 to 25 acres per Animal Unit in 2017, making his ranch more profitable within the same land base.