Recent heavy rain and snow have helped dampen extreme drought conditions in the western United States, but have not been enough to end them. For places like California, Oregon, Nevada and Utah, drought conditions remain in place, with reservoirs recovering only somewhat from several atmospheric flow events that have occurred since December.
While heavy rains in feet and heavy snow in yards made headlines in recent weeks, long-term drought conditions still exist as parts of the west have been affected by drought for more than 20 years. According to NOAA, the effects of a long-term drought often develop and recover slowly and can vary by location and type of drought. Severe hydrological and ecological indicators of drought – such as depleted aquifers and reservoirs and changes in the condition of plants and trees, ecosystem processes and wildlife – can take months to years with normal to above-average rainfall to recover.
While recent atmospheric flow events have provided the region with much-needed water, water tables in the western United States remain low. Storage in reservoirs, while much higher than it was months ago, is still at or below seasonal norms. This is particularly true of 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 Idaho’s farmland, is also arid.
Scientists at the National Integrated Drought Information System, or 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 seep into deep aquifers. Although the need for evaporation is less in the cooler winter months, warm spells can dry out soils and evaporate water from reservoirs, streams, and the snowpack. The amount and type of precipitation that falls over the rest of the winter and spring will be very important for the occurrence and assessment of a long-term drought.
Most of California continues to experience a moderate to severe drought, according to the latest data from Drought Monitor. In parts of Oregon, Nevada and Utah, the same is true for other areas affected by extreme drought. While conditions are dry in the west, they are worse in the central states, where extreme and exceptional drought conditions prevail across Kansas, Oklahoma and Nebraska.
The NOAA Climate Prediction Center Seasonal Outlook shows opportunities for drought elimination or improvement for central and northern California, Oregon, Idaho and the northern Rocky Mountains, with drought persisting in southern California, Nevada and Utah. Current forecasts suggest that atmospheric flow activity could pick up again in early February, but storm tracks are still uncertain.