May 2002 Drought Report

• severe drought affected about 29 percent of the contiguous United States as of the end of May 2002, which is a jump of almost 7 percent when compared to the end of April;
• the coverage of the current (November 1999-present) drought peaked in August 2000 at about 36% of the contiguous U.S., which was as extensive as the major droughts of the last 40 years, but not as large as the "dust bowl" droughts of the 1930's and 1950's;
• the total drought area decreased to about 10 percent by November 2000, but has shown a general increasing trend for much of the period since then (see graph below left);
• on a broad scale, the last two decades were characterized by unusual wetness with short periods of extensive droughts, whereas the 1930's and 1950's were characterized by prolonged periods of extensive droughts with little wetness (see graph below right);
• although various parts of the U.S. have experienced unusually wet conditions during the last 31 months, little change occurred in the aggregate national wetness picture during much of this period;
• the percentage of the nation severely wet has held steady at about three to eleven percent during this period, only recently falling below one percent (see graph below left);
• a file containing the national monthly percent area severely dry and wet from 1900 to present is available;
• historical temperature, precipitation, and Palmer drought data from 1895 to present for climate divisions, states, and regions in the contiguous U.S. are available at the Climate Division: Temperature-Precipitation-Drought Data page in files having names that start with "drd964x" and ending with "txt" (without the quotes).

These overall conditions are evident in the following indicators:

• the Palmer Indices and Standardized Precipitation Index,

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• the runoff, evaporation, and soil moisture conditions as calculated by the National Weather Service,
• maps showing the percent of normal precipitation for May and spring (March-May), the departure from normal of the number of days with precipitation for May and spring, and the maximum number of consecutive days with no measurable precipitation for May and spring,

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• the percent of average precipitation map for the hydrologic year thus far (October 1, 2001 - May 31, 2002), and the percent of average basin snow water content map for the end of May, for the SNOTEL stations in the western mountains provided by the USDA Water and Climate Center,
• the statewide precipitation ranks for May (short-term) and March-May, December-May, and June-May (longer-term), and

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• the USGS May daily streamflow maps.

Two other drought-related monitoring tools are the Vegetation Health Index and the Keetch-Byram Drought Index:

• NOAA satellite observations of vegetation health from early June revealed stress on vegetation across much of the southwestern U.S. and in parts of the Plains and northern and central Rockies.
• The USDA Forest Service uses a satellite-based vegetation health index tool to monitor the risk of wildfires. This Greenness Index for mid-May revealed above-average stress on vegetation across much of the West and Great Plains, extending into the Great Lakes region.
• The Keetch-Byram Drought Index (KBDI) is used by the Wildland Fire Assessment System to monitor the risk of wildfires. The early June KBDI showed dry conditions in the Desert Southwest, parts of the central and northern Rockies, and from the southern Plains to the mid-Atlantic coast. The Forest Service fire danger analysis indicated a high risk of wildfires in the Southwest, across much of the Great Plains, and in parts of the southern Great Lakes and New England. The fire threat conditions can change rapidly from week to week.

A detailed discussion of drought conditions in the western U.S. can be found for the following regions:

• Pacific Northwest region
• West region (California and Nevada)
• Southwest region (AZ - CO - NM - UT)
• Alaska

Dry conditions in the western U.S. stretched from the Canadian border to the Mexican border. As illustrated in the North America vegetation health index map to the right below, the drought did not stop at the borders. According to news reports (Reuters),

• several stations in the Canadian prairie provinces of Saskatchewan and Alberta had a record or near-record dry May this year
• forest and grass fires, dust storms, and drying water holes have accompanied the dry weather
• with dryness throughout the central and southern areas of the plains provinces of Manitoba, Saskatchewan and Alberta, some experts now believe between one half to two thirds of Canada's western grainbelt is suffering from a moisture deficit
• five counties in eastern Alberta, along the border with Saskatchewan, have already declared an agricultural disaster
• for many farmers, this is the third, or even fourth year of drought.

• Up to 400,000 acres of winter wheat, which relies on snow and rain, rather than irrigation, that were seeded last autumn were written off. National winter wheat levels are at their lowest point since 1978 (The Arizona Republic).
• As noted by the USDA, Montana farmers were forced to abandon more than 20 percent of the state's winter wheat for the second consecutive year in 2002, which is the first such occurrence since 1935-36 and 1936-37.
• The USDA will provide the state's agricultural producers with payments for cover crops and no-till farming in an effort to control wind erosion and prevent dust storms (Reuters 5/29).
• By the first week of June, conditions for at least 40 percent of the range and pastures in the state were rated poor to very poor according to the U.S. Department of Agriculture.

• According to the USDA, winter wheat, pastures, and summer crops across the Southern Plains are being hurt by hot and dry weather.
• In early June, the USDA NASS reported that wheat conditions in Kansas, Oklahoma, and Texas were rated as 45, 33, and 53 percent poor to very poor.
• In Kansas, agricultural extension agents are saying a million acres of agricultural land may have to be abandoned this year because of the drought (The Arizona Republic).

• By the end of May, the Idaho Department of Water Resources had issued drought emergency declaration orders for 7 counties during 2002.
• According to media reports (The Idaho Statesman), hundreds of mostly domestic wells in eastern Idaho have dried up from the ongoing drought.

On balance, however, the 2001-2002 wet season ranked near the middle of the historical distribution for the region as a whole (see table below).

The Southwest and southern California are ripe for the riskiest fire season ever, said Edy Williams-Rhodes, fire management director for the Forest Service's southwestern region (NBC News).

• By the first week of June, conditions for at least 80 percent of the range and pastures in Arizona, New Mexico, and Colorado were rated poor to very poor according to the U.S. Department of Agriculture.
• According to media reports (NBC News):
  • In Utah, reservoirs were about half full and streams were running below 50 percent of normal. Officials warned of irrigation cutbacks from 20 percent to 100 percent.
  • In Arizona, some ranchers were liquidating herds.
  • Nevada's Lake Mead was at its lowest level in 30 years as water was redirected from Hoover Dam to other watersheds. Deer hunting quotas have been cut because the herd is decimated.
  • In New Mexico, water was flowing at less than 10 percent of average on the Rio Grande, the lowest level in 102 years.

• The current drought covers much of the same region as it did in 2000 when wildfires burned approximately 8.4 million acres (3.4 million hectares) in the U.S.
• By early June 2002, wildfires had burned more than 1.3 million acres (526,000 hectares) in the U.S., approximately 100,000 more acres (40,000 hectares) than for the same period in 2000, which was one of the worst wildfire seasons in 50 years.
• Unlike 2000, when only 22% of the contiguous U.S. was in severe to extreme drought at the end of May (based on the Palmer Hydrological Drought Index), the same level of drought severity now affects more than 29% of the U.S. with the potential for worsening conditions as the country enters the summer season.
• By the end of May 2002, the Palmer Hydrological Drought Index, integrated across the summer 2000 wildfire region, had reached levels comparable to the severity experienced during the peak (July-September) of the summer 2000 fire season.
• From MSNBC News:
  • The fires have been fueled by some of the driest conditions on record, ravaging ranches and wildlife, and taxing firefighting resources brought on months ahead of schedule. Every one knows the hottest and driest months are still ahead. "This is by far the most aggressive fire season I've ever seen," said Bill Wilcox, a fire management officer for Arizona's Coronado National Forest.
  • The Southwest and Southern California are ripe for the riskiest fire season ever, said Edy Williams-Rhodes, fire management director for the Forest Service's southwestern region.

The Standardized Precipitation Index (SPI) and Palmer Z Index are used as measures of short-term drought. Research by Tom Karl (1986) suggests that the Z Index may be a useful indicator of fire potential. The SPI (see maps to right) illustrate the magnitude of the dryness over the Southwest during May and spring. The Z Index map (below) shows the combination of hot and dry weather during May.

Karl, T.R., 1986. "The sensitivity of the Palmer Drought Severity Index and Palmer's Z-Index to their calibration coefficients including potential evapotranspiration." Journal of Climate and Applied Meteorology, 25:77-86.

Cook, E.R., Meko, D.M., Stahle, D.W. and Cleaveland, M.K. 1999. "Drought reconstructions for the continental United States." Journal of Climate, 12:1145-1162.

Woodhouse, C.A. In review. "A 431-year reconstruction of western Colorado snowpack." Journal of Climate.

• Several fires in Colorado, started by carelessly lit campfires and other human activities, have destroyed hundreds of homes and businesses and forced the evacuation of thousands of residents and park visitors. Federal lands in five Colorado counties have been closed to all uses and the state has banned all public use of fire on all federal lands throughout Colorado's borders. "This is a potential tragedy of epic proportions, and the fire season isn't even upon us," Governor Bill Owens said (Environment News Service).
• All of Colorado's 64 counties have been designated federal disaster areas by the USDA because of the ongoing drought, in what farmers are calling the worst dryness in a half-century (AP 5/30).
• Snowpack levels are at all-time lows. Denver will shut off 14 public fountains this summer (NBC).

• According to The Arizona Republic, wildlife has been devastated and reservoir, lake, and streamflow levels have dropped to record or near-record lows. The fire danger is high across the state, and the city of Flagstaff implemented mandatory outdoor watering restrictions during May. Rangers have noted the impact of the drought on forests: "Douglas fir trees are beginning to die of a lack of water, and even drought-resistant trees such as junipers and piñon pines are starting to show stress."
• On May 17, Agriculture Secretary Ann M. Veneman designated the entire state of Arizona as a drought disaster area.
• Governor Jane Hull activated a state emergency drought response plan and formed a drought task force coordinated through the state Agriculture Department and the Division of Emergency Management.
• Cattlemen have been severely impacted. According to The Arizona Republic, while most of the state's farmers have enough water this year, some already are hurting, and all fret about next year's cattle and crops if the drought continues.
• The drought has seriously impacted the Navajo Nation. According to news reports (The Arizona Republic):
  • More than 7,000 stock ponds are dry across 17 million acres of the reservation in Arizona, New Mexico and Utah. Many of the tribe's 900 windmills, most of them pumping groundwater from shallow, subsurface pools, are expected to stop producing within the next month.
  • Thousands of head of livestock, as well as the tribe's world-famous rural traditions, are threatened.
  • People have described the drought with words like: "desperate situation", "never seen a drought like this before", "it looks like another planet".
• The Tohono O'odham Nation declared a state of emergency by month's end as dwindling water supplies threatened livestock (The Arizona Republic).
• According to an early June drought situation report by the Arizona Division of Emergency Management:
  • Marginal snowpack conditions and well below normal winter rainfall resulted in very low streamflow and reservoir levels in the state. Winter precipitation amounts have been well below normal for six of the last seven years, leading to a serious drought outlook for the next several months.
  • Water supply problems are expected in many parts of the state, although no critical shortages had developed by the beginning of June. Eight counties, and the Navajo and Tohono O'odham Nations, have declared drought emergencies.
  • The wildland fire season has been exceptionally active so far, due to the very dry condition of the grasses in the rangelands, and because of the warm, dry, and windy conditions.
• As noted by The Arizona Republic, "the current drought is the state's worst drought since the 1950s, and although it doesn't rival the 1890s, when it was so dry and windy that a good 6 inches of the state's topsoil blew away, the state is parched. We have the genesis of the worst fire season and the worst drought in history, according to the Arizona Farm Bureau."

• several stations in the panhandle had the driest spring on record
• low water levels in area lakes caused power generation shortfalls in some hydroelectric plants
• the wildfire danger increased across the panhandle and some burn bans were issued

As noted by media reports, hot, dry, windy weather near the end of May fanned numerous forest fires across parts of the state. By early June, the year-to-date (January 1-June 4) acreage burned exceeded 400,000 acres, which is 26 times the average and three and a half times the total acres for the same time of year for the previous 7 years combined (BLM - Alaska Fire Service). The drought code used by the Alaska Fire Service had moderately dry conditions extending from the southern coast into east central Alaska, with a high risk of wildfires in early June extending across the interior portions of the state.

Colorado - Delaware - Delaware River Basin (DE-NJ-NY-PA) - Florida Panhandle - Georgia - Hawaii - Idaho - Kentucky - Maine - Maryland - Missouri - Montana-1 - Montana-2 - Nebraska - New Jersey-1 - New Jersey-2 - New Jersey-3 - New Mexico - North Carolina - Oklahoma-1 - Oklahoma-2 - Oklahoma-3 - Oregon-1 - Oregon-2 - Pennsylvania-1 - Pennsylvania-2 - Pennsylvania-3 - South Carolina - Texas - Vermont - Virginia - Washington - Wyoming

For additional information on current and past wildfire seasons please see the National Interagency Fire Center web site or the U.S. Forest Service Fire and Aviation web site.

NCDC's Drought Recovery Page shows the precipitation required to end or ameliorate droughts and the probability of receiving the required precipitation.

Additional climate monitoring graphics can be found at the Climate Prediction Center's monitoring pages:

• Weekly, Monthly, 3-Month, 12-Month Monitoring
• El Nino, Drought, Snow Cover, and Degree Day Monitoring
• Weekly Drought Monitoring
• Soil Moisture Monitoring

Drought conditions on the Canadian prairies can be found at the Agriculture and Agri-Food Canada Drought Watch page.