Drought Information Statement for Arizona & SE California - Updated July 17, 2021

Drought Persists Though Monsoon Rains May Offer Improvement

Updated on Saturday, July 17, 2021

Summary:

Despite a good start to the 2021 Monsoon, the 2020-21 Water Year remains much drier than normal with most locations in the southwest region still near the driest top 10 years on record. The limited
higher elevation snowfall from the winter resulted in poor runoff and challenged some of the worst reservoir inflow years on record. Early monsoon season rainfall has been beneficial for many locations in Arizona with many observations of better than 2 to 3 inch accumulations already. As with most monsoon seasons, rainfall totals have been spotty with much of western and northeast Arizona missing out on better accumulations. In areas that have received good rainfall, this will help in soil moisture recharge such that future precipitation events will contribute more readily to runoff.

Much of the drought impacts have been focused in short term influences such as forage for ranchers, water availability for land based wildlife, and small stream flow for aquatic wildlife. Recent wetness during the past couple winter seasons has resulted in adequate long term hydrologic stability. However with reduced snow melt this year, reservoirs have experienced little recharge. Early monsoon season rainfall may have helped some areas with soil moisture recharge, but it will take much more precipitation to fully ameliorate this drought.  

Local Area Affected:

The National Drought Monitor depicts only minor deterioration of drought measures across Arizona and SE California.

Exceptional Drought (D4) - parts of south-central and southwest Arizona and SE California

In Arizona: far southeast Maricopa, southern Gila, eastern Pinal, and northern La Paz counties 

In SE California: far northeastern Riverside County

Extreme Drought (D3) - across much of central, southern, and eastern Arizona and SE California

In Arizona: much of Maricopa, western Pinal, and the majority of La Paz counties

In SE California: most of eastern Riverside County

Severe Drought (D2) -  parts of southwest Arizona and SE California

In Arizona: southern La Paz, northern Yuma and southwest Maricopa counties

In SE California: small part of Riverside County and northern Imperial County

Moderate Drought (D1) - southwest Arizona and SE California

In Arizona: southern Yuma County

In SE California: southern Imperial County

Abnormally Dry (D0) - southwest Arizona

In Arizona: far southern Yuma County

Local Climatology:

Below are precipitation totals since the beginning of the 2020-21 Water Year from selected locations across Arizona and southeast California (Please note Normals have been adjusted to reflect the new 1991-2020 official climate period):

In addition to the precipitation deficit, drought conditions have worsened and expanded more rapidly as a result of extreme temperatures. Precipitation deficits over the past year are solidly at record low levels for the entire Southwest United States. Add in the near record heat over the past year, and it's fairly clear why Extreme and Exceptional Drought covers much of the Southwest. 

The U.S. Drought Monitor is a weekly collaborative effort between a number of federal agencies including NOAA/NWS, U.S. Department of Agriculture and the National Drought Mitigation Center. Details and explanations of the Drought Monitor can found at the web site:

http://droughtmonitor.unl.edu/ 

The categories of drought are defined as follows:

Abnormally Dry (D0) - Going into drought: short-term dryness slowing planting, growth of crops or pastures; fire risk above average. Coming out of drought: some lingering water deficits; pastures or crops not fully recovered.

Moderate Drought (D1) - Some damage to crops, pastures; fire risk high; streams, reservoirs, or wells low, some water shortages developing or imminent, voluntary water use restrictions requested.

Severe Drought (D2) - Crop or pasture losses likely; fire risk very high; water shortages common; water restrictions imposed.

Extreme Drought (D3) - Major crop/pasture losses; extreme fire danger; widespread water shortages or restrictions.

Exceptional Drought (D4) - Exceptional and widespread crop/pasture losses; exceptional fire risk; shortages of water in reservoirs, streams, and wells, creating water emergencies.

State and Local Actions:

A Drought Emergency Declaration remains in effect for the state of Arizona as signed by the governor in accordance with the Arizona Drought Preparedness Plan. The continuation of this Drought Emergency has been recommended by the Drought Interagency Coordinating Group in their bi-annual meeting on May 11, 2021. This recommendation is based on long term precipitation deficits, along with ongoing negative impacts across the state. . 

Additional information concerning the drought in Arizona can be obtained via the Arizona Department of Water Resources web site at:

https://new.azwater.gov/drought

Additional information concerning the drought in California can be obtained via the California Department of Water Resources web site at:

http://www.water.ca.gov/waterconditions

River, Stream Flow, and Reservoir Conditions:

Some smaller streams throughout Arizona have seen some response as a result of early monsoon season rainfall. In fact, many unregulated smaller streams are flowing at near to above normal levels this July. Winter runoff into area reservoirs was near the lowest recorded in many parts of the state. The more highly regulated larger rivers remain in a near normal flow rates due to continual management efforts.

With soil moisture abnormally dry and winter precipitation extremely poor, total system runoff on the Salt/Verde basin this past spring was the 2nd lowest recorded and offered little help for reservoir recharge. Fortunately, good precipitation the past 2 winter seasons along with excellent management has kept the system in good shape. Early monsoon rainfall may help replenish soil moisture in many locations and set the stage for more effective runoff later in the monsoon and next water year.

Hourly and forecast river stages out to 90 days can be found at the National Weather Service's (NWS) Advanced Hydrologic Prediction Service (AHPS) web page:

http://water.weather.gov/ahps2/index.php?wfo=psr

Additional Current stream and river stages may be viewed at the following USGS Web Site:

http://waterwatch.usgs.gov/

Agriculture Impacts:

78% of the Arizona range and pasture land rated as poor to very poor compared to 90% last month, but just 31% at this time last July and the 5-year average of 46%. Very dry and breezy weather much of the spring depleted most remaining available soil moisture after a very poor winter. Spring rainfall needed for healthy forage area was mostly absent, and supplemental feed has been necessary. Reports continue to indicate many stock ponds low or empty requiring water hauling. Even with early monsoon rainfall, stock ponds have not refilled owing to the tremendous soil moisture deficit. Ranchers continue to experience the worst impacts from this extreme and exceptional drought.

For additional information on agriculture impacts may be viewed at the United States Department of Agriculture (USDA) National Agricultural Statistics Service NASS Web Site:

  https://www.nass.usda.gov/Statistics_by_State/
index.php

Fire Danger Hazards:

The National Fire Danger Rating: Moderate to High category across the region

The current KDBI: Southwest Arizona and southeast California: Ranging from Extreme lower elevations of SE California and southern Arizona and High in some of the higher elevations of northern and eastern Arizona

Palmer drought severity index (PDSI):
The current weekly PDSI shows nearly steady state conditions across the region as recent monsoon rainfall has yet to be incorporated into this drought measure. The worst PDSI measure continues to be spread over northern Arizona where drier than normal conditions have been most prevalent over the past several years. Even in SW Arizona and SE California where long term drought severity has been more muted, PDSI measures are falling.  

Spring weather was predominantly hot, dry, and breezy producing a crop of unusually dry fuels. Acreage burned by wildfires this spring outpaced last year with abundant fine fuels holding little moisture. Fire restrictions were put in place across much of Arizona for state owned lands with closures of national forests in an attempt to limit further wildfire starts. However, early monsoon activity and much more pronounced humidity levels have nearly ended the fire season for the time being, though long term drought will need further improvement before the larger fire risk is tempered.

With the recent surge of better moisture and periodic rainfall, 100-hour dead fuel moisture has improved to a 11-15% range in the eastern 2/3rds of Arizona, while still hovering in a 6-10% range to the west. Similarly, 10-hour dead fine fuels have improved markedly over the eastern parts of Arizona where values have increased into a 7-15% range. Even to the west, modest improvements into a 5-6% range have been noted. 

The Keetch-Byram Drought Index (KBDI) is a drought index that is specifically related to fire potential. The KDBI is broken into four categories which indicate the susceptibility of ground fuels to fire danger. Below are the four categories and a brief description of each.

KBDI and Dead Fuel Moisture data can be found on the Wildland Fire Assessment System (WFAS) web site at:

http://www.wfas.net

Precipitation/Temperature Outlooks:

The 8-14 day temperature outlook for July 25-31 period calls for better chances of below average temperatures and slightly enhanced odds for below normal rainfall range. The 90 day outlook for the period August through October 2021 indicates better chances for above average temperatures and somewhat enhanced odds for below normal precipitation. 

La Nina peaked in the tropical Pacific during the past winter with sea surface temperatures now hovering around average. The equatorial Pacific and atmospheric flow has settled into a neutral state, and will remain as such through the summer. ENSO status typically has minimal influence on monsoon rainfall. There is about a 65% chance of La Nina returning again in the fall/winter 2021-22 with odds favoring another winter of below normal precipitation. There is very little chance of a transition to El Nino.

For updated temperature and precipitation probabilities consult the following Climate Prediction Center (CPC) Web Sites:

8 to 14 Day Outlook:

http://www.cpc.ncep.noaa.gov/
products/predictions/814day/

30 Day Outlook:

http://www.cpc.ncep.noaa.gov
/products/predictions/30day/

90 Day Outlook:

http://www.cpc.ncep.noaa.gov/products
/predictions/long_range/seasonal.php?lead=01

Questions or Comments:

If you have any questions or comments about this information
please contact:

w-psr.webmaster@noaa.gov

Acknowledgements:

The Drought Monitor is a multi-agency effort involving NOAA’s National
Weather Service and National Centers for Environmental Information, 
the USDA, state and regional center climatologists and the national
drought mitigation center. Information for this statement has been gathered
from NWS and FAA observation sites, cooperative and volunteer observations,
USDAFS, the USDA and USGS.

Related Websites :

NWS - http://www.weather.gov/phoenix

CPC - http://www.cpc.ncep.noaa.gov

Drought Monitor - http://droughtmonitor.unl.edu/

USGS - http://waterwatch.usgs.gov/

COE - http://www.spk.usace.army.mil/