The U.S. Drought Monitor, established in 1999, is a composite index that includes many weather and drought indicators and it produces the drought map that policymakers and media use in discussions of drought and in allocating drought relief. It is jointly produced by the National Drought Mitigation Center at the University of Nebraska-Lincoln, the United States Department of Agriculture, and the National Oceanic and Atmospheric Administration. Maps courtesy of NDMC-UNL.
Here is their most current map of drought conditions in the United States, released April 20, 2017 (Click map to enlarge).
One can easily see many areas of continuing drought throughout the country, including areas of severe and extreme drought.
The U.S. Drought Monitor has five definitions of drought severity: abnormally dry (D0), moderate drought (D1), severe drought (D2), extreme drought (D3) and exceptional drought (D4). These designations are based on multiple factors, such as soil moisture, streamflow and precipitation index, as well as compounded factors, like the Palmer Drought Severity index, which takes into account temperature, precipitation and soil moisture. Virtually 100 percent of California suffered from the drought in varying levels of severity from 2014 to 2016. The drought was especially bad in August 2014, when 58.41 percent of the state was affected by the most severe level (D4) of drought (Click chart to enlarge).
Today, after the wettest winter in several years, people have been fast to jump to the unwarranted and just plain wrong conclusion that the drought is over. The term “drought” can have different meanings to different people, depending on how a water deficiency affects them. Droughts have commonly been classified into three different types:
- Meteorological Drought: Lack of precipitation
- Agricultural Drought: Lack of soil moisture
- Hydrologic Drought: Reduced streamflow or groundwater levels
Water quality degradation, surface and groundwater level declines and land subsidence all are serious impacts of drought, and increased rainfall during a limited period can seldom resolve long-range problems. In California for example, looking at the state’s three primary water sources sheds light on questions related to drought and its on-going consequences:
- Surface Water: Precipitation in water year 2017 has filled the majority of California’s major reservoirs to above-historic average levels, and flows in the majority of streams have been at or above average for most of the last four months. This only indicates that most of California’s rivers, creeks, lakes and reservoirs are in good condition.
- Snowpack: On average, the Sierra Nevada snowpack supplies about 30% of California’s water needs as it melts in the spring and summer. A series of back-to-back atmospheric river storms
blanketed the Sierra Nevada in January and February of this year, and as of April 24, 2017, statewide snow accumulation data indicate that snowpack in the Northern, Central, and Southern Sierra is 190% of normal for this date.
- Groundwater: Groundwater aquifers recover much more slowly than surface water and are limited in many ways, including by how much and how fast water can recharge. Unlike surface water, which can recover during a few days of heavy rain, groundwater aquifer recovery often takes years or decades. Groundwater systems are also relied upon more heavily during times of drought. In addition, in many areas of the state, groundwater systems have been depleted for long periods even between droughts,f rom which they had not recovered. Excessive, long-term groundwater over-use resulting in groundwater depletion can cause subsidence and permanent loss of groundwater storage as well as water quality degradation and seawater intrusion. These long-term impacts on groundwater have not been remedied by the recent weather. If recovery is possible, it will likely take man, many years to accomplish.
Clearly, a few weeks of heavy rain do not solve such a long-term problem, and the fact of deficient groundwater, which cannot be replenished in the short run, means that drought conditions through much of California, especially Southern Californian, and in states across the country, continues.
In California, governor Jerry Brown has taken action that is dead wrong in issuing his Executive Order B-40-17, officially ending the drought state of emergency in all California counties except for Fresno, Kings, Tulare, and Tuolumne. In fact, The latest National Weather Service Climate Prediction Center seasonal drought outlook, valid for April 20 to July 31, 2017, shows drought in areas of Southern and Central Coastal California likely to persist throughout those dates. Clearly, a long, dry summer going into the fall will not only mitigate against drought recovery throughout California (and other areas of the country) but reverse the favorable effects of the heavier than normal rain of the past winter.
We have history and current trends working against us. Groundwater provides 30% to 46% of California’s water supply and because of the drought, these sources became increasingly depleted. More than 57% of the state’s groundwater sources have decreased by more than 10 feet from spring of 2006 to spring of 2016. This poses a dangerous risk to our environment as well as over-reliance on the use of groundwater can lead to the lowering of water tables causing land subsidence and decreased water quality.
National Weather Service records show that prior to this past rainy season, downtown Los Angeles had only seen 38.79 inches of rain over the preceding five years, but that this past season (since October, 2016) saw 13 inches of rainfall, 216% greater than normal.
Thinking that this sort of increased precipitation will continue is not based on fact or reality. California’s groundwater, the singular most important element in the state’s supply of drinkable water, will not be replenished this year, next year, the year after, nor likely in the foreseeable future. In fact, the U.S. Drought Monitor says that TODAY 38.34% of California remains under drought conditions.
Ramifications from California’s drought are felt not just in the state, but across the country. Fully 25% of all produce consumed in the United States is produced in California’s Central Valley. Falling production due to the drought (and other factors that periodically arise, from plant disease, insect infestation to labor problems) causes decreased availably and rising prices across the country. As California goes, so goes the country, and a drought in the Golden State affects wide areas that may be luckier as far as lessening drought conditions are concerned.