Drought and the forest: dry winter can be mitigated by 'monsoons'
(Editors note: Based on the weather this winter, if things don't change, the local area will be experiencing a drought. This is the third in a series of articles examining droughts, water use, water storage/sources, personal water footprints and what the impacts of a prolonged drought has done in the past and can do to the eastern Utah in the future).
As children most of us like the mud.
We stomp in it, we play in it and we make a lot of things out of it.
The mixing of water and soil makes for a great time when we are kids.
For Jan Curtis-Tollestrup and Robert Davidson, that has never changed, other than the fact that they deal in the combination of the two daily as part of their charge as scientists for the Manti-La Sal National Forest. While they don't play in the mud, they do revel in the fact that water and soil are an important part of a healthy forest.
To Curtis-Tollestrup, a hydrologist, and Davidson, a certified soil scientist, the basics of water and soil are apparent. While the pair come from different disciplines, when it comes to a healthy forest, it is difficult to separate the two fields. They even work together in a small office at the forest headquarters in Price.
Their job is to know how water, and the soil that exists in the watershed above Carbon and Emery counties, affects the ecosystem of the forest. How that water falls on the forest, how it runs off and when it lands on the ground has a great deal to do with how the forest does each year. Dry years bring a higher chance of fires while wet years nourish the forests. But extremes either way are not necessarily all bad, nor all good.
While the lack of snow this winter has put almost everyone into the mode of thinking that it will be a drought year, neither Davidson nor Curtis-Tollestrup are ready to throw in the towel yet.
"We could still get a lot of snow during the rest of February and March and the spring could be wet as well," said Davidson as he reviewed the year to year moisture charts in their office. "And remember 1977? That was a year when we had less snow in the mountains than we do now. In fact there was no snow."
The chart Davidson was reviewing showed data that cycles certainly do happen when it comes to snowpack. Less than two years after 1977 the snowfall was above average. And in 1983, a year almost everyone that lives in Utah that is old enough to remember, the snow was overwhelming and very wet. It, and consequent rains, created huge problems in the spring when it began to run off as water, including the Thistle Slide that destroyed the town of Thistle and isolated eastern Utah from its quickest route to the Wasatch Front for months.
Last year near record snowfall again plugged the mountain passes and roads. The runoff did create some flooding, but nowhere near the 1983 levels, largely because of better planning and to a larger extent a cool spring that lasted through June. Because of that the water came down out of the mountains more slowly.
And it hasn't been that long since the area suffered through another poor water year in 2006.
Several factors affect soil moisture
"Soil moisture is dependent upon a lot of things," said Davidson. "And a lot of that depends on how the season goes. If water stays in the soil throughout the winter, then more water runs off in the spring."
Curtis-Tollestrup pointed out that both low ground moisture during the winter and high levels are positive in different ways.
"If the soil is dry when the runoff starts, more of it will go into the ground and that recharges the aquifer," she said. "If it runs off it can create a lot of surface water."
That's good for irrigators and for reservoirs.
The past six months have been interesting for many observers because there was a lot of rain in the area in October and early November which brought the soil moisture up. In many years the moisture that comes like that gets locked into the ground by winter snows. Then in the spring the moisture content of the soil is great enough that the water runs off rather than soaking into the ground. This past six months that soil moisture measured to near 60 percent in November but over the winter it had dropped to 40 percent as of early February. The lack of winter snow cover, little moisture and freezing temperatures have added up to a decrease.
One would think the cold temperatures would keep moisture in the soil. But that isn't what happens. Generally we all think of water as having three forms; liquid, gas and solid (ice). In this case what happens is sublimaton. In the case of sublimation, the liquid form of water is skipped as the cold draws the moisture from the uncovered soil, creating less moisture in the ground that was there only a short time before. With no snow covering the ground, there is no real moisture to either recharge the ground or the streams.
There is still hope
Yet not all is lost, say the pair. Recent storms and some predicted for the rest of this week could bring a lot more moisture to the mountains and the forests. And there are a lot of scenarios that could make or break the water year in the forest, making for a healthy year or an unhealthy one. A big catch up is needed to make this any semblance of a normal water year.
There are many scenarios that can happen each season. A high moisture content in ground the fall before a large snowpack covers it can mean good water in the spring and summer, but if it gets to hot too fast then it can mean flooding. A low moisture content in the soil, with a large snowpack will make things about equal as the water soaks in and runs off. A lot of moisture in the soil in the fall and a small snowpack that covers it for the winter can still mean good runoff because the water will go into streams rather than go into the ground. There are also many other combinations of runoff and the amount of moisture in the soil that could be considered as well.
Summer monsoons can mitigate forest fires
People generally don't understand how much water is yielded from snow either. Many think that one inch of snow is one inch of water. But this is never true even with very wet snow. While many worry about the snow pack, the health of the forest, particularly the chances of wildfire decimating any area of it, has to do as much with the monsoon season in the summer as it does with snow in the winter.
"The monsoon season in the summer is a deal breaker," said Davidson. "You can enter the summer dry, with no moisture, but the monsoon can be more critical for the forest than that factor is."
Of course the monsoon can cause problems too. If it gives only a little water and lots of lightning, that can be a cause of fires. But a good monsoon soaks everything and keeps the danger down.
The best scenario? High ground moisture in the spring, a good snowpack that runs off at a medium rate and a good wet monsoon season.
The worst? Little moisture in any way. Right now things are down in all areas and hoped improvement through more snow or rain is where things presently stand..
When one thinks of the forest, one thinks of trees and other plants on the forest floor. But there are other parts of the forest just as important. The national forests in Utah are made up of those trees, but they are also made up of streams and wetlands.
And how drought affects those various aspects of a forest may not always be important to culinary and irrigation water supplies, but it does have an effect on the health of the forest as a whole.