Drought resets winter 2018/2019 and summer 2022
Wednesday – 19 Oct 2022 – 9:00am
Let’s start with the good stuff first.
Drought “resets” for Archuleta County…
We’ve recently had two drought “resets”: winter 2018/2019 and summer 2022. What did it take to significantly improve our drought conditions?
Long term trends…
Defining drought is tricky…
Drought.gov: In the early 1980s researchers found more than 150 published definitions of drought, reflecting differences in regions, needs, and approaches.
Drought is generally defined as “a deficiency of precipitation over an extended period of time (usually a season or more), resulting in a water shortage.”
Merriam-Webster Dictionary: “A period of dryness especially when prolonged.”
American Meteorological Society: “A period of abnormally dry weather sufficiently long enough to cause a serious hydrological imbalance.”
NOAA’s National Weather Service: “A deficiency of moisture that results in adverse impacts on people, animals, or vegetation over a sizeable area.”
Wikipedia: A drought is defined as drier than normal conditions. This means that a drought is “a moisture deficit relative to the average water availability at a given location and season”. A drought can last for days, months or years. Drought often exerts substantial impacts on the ecosystems and agriculture of affected regions, and causes harm to the local economy.
Determining and measuring drought…
“Common to all types of drought is the fact that they originate from a deficiency of precipitation resulting from an unusual weather pattern. If the weather pattern lasts a short time (say, a few weeks or a couple months), the drought is considered short-term. But if the weather or atmospheric circulation pattern becomes entrenched and the precipitation deficits last for several months to several years, the drought is considered to be a long-term drought. It is possible for a region to experience a long-term circulation pattern that produces drought, and to have short-term changes in this long-term pattern that result in short-term wet spells. Likewise, it is possible for a long-term wet circulation pattern to be interrupted by short-term weather spells that result in short-term drought.”
“Indices used to monitor short-term drought-related impacts (timescales ranging from a few days to a few months) include wildfire danger, non-irrigated agriculture, topsoil moisture, range and pasture conditions, and unregulated streamflows.”
A small example of the many indices:
- The Crop Moisture Index measures short-term drought on a weekly scale and is used to quantify drought’s impacts on agriculture during the growing season
- The Palmer Z-Index measures short-term drought on a monthly scale
- The Standardized Precipitation Index, a probability index that considers only precipitation, is computed for several timescales ranging from 1 to 72 months to capture the various scales of both short-term and long-term drought.
Drought isn’t defined or determined by what’s going on in your backyard. Lots of data is incorporated across large regions and entire drainages. Drought is slow to develop and slow to resolve.
The five different types of drought – meteorological, hydrological, agricultural, socioeconomic, and ecological – have different impacts, may or may not overlap, are determined and measured differently, and often have varying durations.
Be thankful for these drought resets! Why do I call them resets? The vast majority of data indicates that we will continue to struggle with drought. Lake levels throughout the region, and the two primary lakes – Powell and Mead – need multiple years in a row of above average precip to make a real difference. Unfortunately, the data says the odds are against it.
Sources and links…
Weekly drought maps: https://droughtmonitor.unl.edu/Maps/MapArchive.aspx
Drought data for Archuleta County: https://www.drought.gov/states/colorado/county/Archuleta
Monitoring drought: https://www.drought.gov/what-is-drought/monitoring-drought
Drought monitoring tools: https://drought.unl.edu/Monitoring/DroughtMonitoringTools.aspx
Colorado Climate Center: https://climate.colostate.edu/drought/