What is in this article?:
- Soil drought expected to end; hydrologic drought to be long-term issue
- Trouble for cities
- The drought that has covered most of the Southwest for two years is coming to an end.
- A hydrologic drought could persist for years.
- Average rainfall for several years will not refill reservoirs.
Reduced stream flow occurs with hydrologic drought.
Trouble for cities
“This could mean trouble for some cities. We have to get a lot of rain for hydrologic drought relief. High temperatures, low rainfall and high winds equal high evaporation,” he said. Those conditions have persisted for the last two years.
Now, with catchment levels as low as they are, a “typical year with average rainfall will not be enough to maintain the reservoir levels.”
In fact, Lyons said, several years of just average rainfall would result in reservoir levels continuing to drop. An event such as a hurricane that hovers over the area for several days, dropping up to 20 inches of water and creating massive flooding, might be necessary for a quick refill. Otherwise, the region will need several years of above average rainfall to bring reservoir levels up to normal capacity.
“Rainfall has to soak the soil first, before water can begin to run off and into streams that carry it to the reservoirs.” He said to “pre-condition” soil for runoff would require something on the order of a two-inch rain event.
Lyons said the current drought, now afflicting more than half of the United States, is “bad, but not as bad as the Dust Bowl Days of the 1930s.”
But it’s bad enough with 87 percent of the U.S. corn acreage, 85 percent of soybean acreage, 63 percent of hay production and 72 percent of cattle operations experiencing drought. “The current drought monitor, which has created a big hoopla because of the effect on the Midwest, shows drought extending into Texas. Conditions in West Texas are not good,” Lyons said.
He said forecast for the next 90 days shows possibility for “some improvement” for south and east Texas. For the rest of the state, the drought likely will persist until at least November with “an equal chance of above and below average rainfall and temperatures.”
Beginning in December, Lyons said, El Nino should become the dominant force in Southwest weather. “That forecast is not perfect. El Nino could fizzle, but it seems pretty certain that we will have an El Nino event. The magnitude, however, is not as certain.”
In an El Nino cycle, the Southwest typically has more snowfalls and some bigger ones.
Regardless of how much snowfall the region receives this winter and regardless of whether the drought breaks by Christmas, without a significant amount of precipitation, either in a massive and possibly destructive event or above average precipitation over the course of several years, the area’s hydrologic drought will continue.
“Eventually, all kinds of water restrictions will be employed if things don’t change,” Lyons said.