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Our Watershed - Its condition and threats

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Editor’s note: This is the fifth in a series running over several consecutive Fridays. It is written by members of the Hermit’s Peak Watershed Alliance, which seeks to foster land stewardship in the Gallinas, Sapello and Tecolote watersheds.

When compared with heavily populated and largely urban or industrial watersheds, the Gallinas Watershed is in relatively good shape. But, if we expect it to continue supplying our water in to the future, we have to face some realities and maximize its performance and resilience to future threats.

The challenge is to balance the needs of the river system with the needs of the people who live within it.

The upper Gallinas Watershed (the area upstream of the city of Las Vegas diversion) is actually quite small for a watershed that must supply 90 percent of the water for Las Vegas. It is 76 square miles (48,968 acres) of land dominated by ponderosa pine and mixed conifer forests with some rangeland, small amounts of agricultural lands and rural residential areas. About half the land is managed by the U.S. Forest Service and the other half is owned and managed by private individuals and the city of Las Vegas.

This land produces water, timber, agricultural products, homes and other resources for around 15,000 people. Historic and current land uses have taken their toll on the way our watershed functions and its ability to support us now and down the road.

Natural processes that shape the land and maintain our watershed have changed considerably with human use. Compromised plant ecology in our watershed exists from the mountain tops to valley bottoms. And the shape and functionality of the river and floodplain have been degraded.

Aggressive logging and grazing during the railroad building era followed by over one hundred years of fire suppression has lead to forests with high densities of small, unproductive trees and little understory plant cover. These forests lack diversity and have a greater tendency to catastrophically burn over large areas. The effect on our water supply is that less water is able to infiltrate the soil, reducing the soil’s capacity to act as the watershed’s sponge. If less water sinks into the soil, more water runs off leading to more damaging floods during storm events. If you believe the experts, the question is when the fire will come, not if. When it does, this fire is likely to be much more severe than if we had had smaller, more frequent fires.

Critical vegetation like willows, cottonwoods and abundant herbaceous plants that grow next to rivers and streams in the Bosque (riparian area) have been overgrazed because livestock tend to concentrate in those wet and green places. To gain access to the river and increase visibility, riparian areas have been cleared of shrubs and trees, and in the process making the banks more vulnerable to erosion when the bigger flows happen.

Meadows and valley bottoms have been historically overgrazed causing reduced plant growth and contributing to fewer low intensity ground fires.

Excessive bare ground is prone to erosion, arroyo formation and rapid water runoff with little infiltration. This also creates conditions ripe for noxious weeds to take over. All these circumstances add sediment to our water supply, cause drainage channels to become entrenched (down cut) and reduce plant diversity. It is a self fulfilling cycle of degradation. As the watershed’s sponge begins to dry the residents of San Miguel County feel each lost drop.

In some areas where the river was once able to spread out and dissipate water during flood events the River has been straightened to allow development of valley bottoms for residential and agricultural uses. It is no coincidence that the areas that make great fields were once flood plains. A straightened river channel has no place to dissipate energy but down and as a result often leads to entrenchment and disconnecting the stream from its historic floodplain.

Straightened and entrenched river channels have lost deep pools, large logs, side channels and attached wetlands all of which not only increase the beauty of the river but also make it more resilient to large flood events. Lost too is habitat for fish and the services of slowed water flow, improved infiltration, water storage in the floodplain and reduced erosion.

When streams become entrenched and disconnected from the surrounding floodplains, water that once was absorbed by the banks and even in sub irrigated pastures quickly makes its way downstream and out of the system.

Straightened and entrenched stream channels starve riparian areas and floodplains of water requiring more irrigation of valley bottoms to maintain production over time.

Beaver ponds and wetlands that once stored vast quantities of water and sediment have been removed in many places.  These features now only occur in a few isolated locations rather than throughout the river system because of conflicts with human land uses. While beaver dams and thick stands of willow may not provide an obvious benefit to people we are beginning to realize their benefit to the overall health of the system and its ability to absorb big events.

The overall effect of these compromised conditions is that less water is stored in soils to be cooled, cleaned and slowly released to the river over time. This means less high quality water available to the city in a sustainable and consistent fashion. It also means a higher risk of damage in the event of fire related or naturally occurring floods. If you believe the climate experts, longer droughts and bigger storm events will be more common in our future. To thrive in these conditions, we will need a watershed that is functioning at its peak performance.

While it is difficult to estimate the exact magnitude of these compromised conditions, we do know these relationships occur and degraded conditions exist, with reduced water quality and quantity as a consequence. The temperature impairment in the Gallinas River and El Porvenir Creek is one measure of this. Another is the city’s need to refrain from water withdrawals at many times during the year because water is either too laden with sediments or is of insufficient quantity.

While the big threats to our water supply are drought and climate change, there are local, more manageable threats that are well within our ability to address. Each of these threats poses an opportunity to better understand our watershed, work to restore and maintain its health (there are even some jobs to be had here), and become better stewards of the land that is critical to sustaining us.

The degraded conditions we see in the Gallinas can all be remedied with thoughtful restoration and land management work. Stay tuned for a discussion of those opportunities.

Information for this article is largely derived from the Updated Watershed Based Plan for the Upper Gallinas River that can be found on the Hermit’s Peak Watershed Alliance website.

Next week: Opportunities to improve our current system.

The Hermit’s Peak Watershed Alliance may be reached by visiting its website at hermitspeakwatersheds.org or by calling 505-425-5514.