Recent heavy rain and snow has helped put a dent in extreme drought conditions in the western U.S. but they weren’t enough to end it. For places like California, Oregon, Nevada, and Utah drought conditions persist with reservoirs only rebounding somewhat from several atmospheric river events to hit since December.
While heavy rains measured in feet and heavy snow measured in yards has made headlines in recent weeks, long-term drought conditions are still present as parts of the West have been in drought for more than 20 years. According to NOAA, the impacts of long-term drought are often slow to build and recover, and can vary by location and by type of drought. Severe hydrologic and ecological drought indicators—such as depleted groundwater aquifers and reservoirs and changes in the condition of plants and trees, ecosystem processes, and wildlife—can take months to years of normal to above-normal precipitation to recover.
While the recent atmospheric river events had provided much needed water to the region, groundwater levels across the western U.S. remain low. Storage in reservoirs, while much higher than they were just months ago, are sill low at or below seasonal norms. This is especially the case for Lakes Powell and Mead in the Upper and Lower Colorado River Basins, which are important for water supplies in southern Nevada, Arizona, and southern California. The upper Snake River basin, which contains more than 60% of the agricultural land in Idaho, is also short of water.
Scientists with the National Integrated Drought Information System, NIDIS for short, say that while short-term rain events replenish soil moisture near the surface, it can take months or years for that water to percolate into deep groundwater aquifers. Although evaporative demand is lower during the cooler winter months, warm spells can start to dry out soils and evaporate water from reservoirs, streams, and the snowpack. The amount and type of precipitation that falls over the remainder of winter and spring will be very important to the occurrence and evaluation of long-term drought.
According to the latest data from Drought Monitor, most of California remains under a Moderate to Severe Drought. In portions of Oregon, Nevada, and Utah, the same is true with additional areas under Extreme Drought. While conditions are dry in the West, they are even worse in the Central States, where Extreme and Exceptional Drought conditions exist over Kansas, Oklahoma, and Nebraska.
The NOAA Climate Prediction Center’s Seasonal Outlook shows chances of drought removal or improvement for central and northern California, Oregon, Idaho, and the northern Rockies, with drought remaining in southern California, Nevada, and Utah. The current forecasts indicate atmospheric river activity could pick up again in early February, but the storm tracks are still uncertain.
