WESTERN STATES WATER NEWSLETTER 8/13/04
WATER RESOURCES
Drought
According to the August 10 Drought Monitor, scattered summer
thunderstorms have brought little or no relief from the drought in the
Western Rockies and Far West. Here are some excerpts from the report:
“The so far anemic monsoon season continued across most of Arizona,
western New Mexico, Utah, and western Colorado last week. A small part of
north central Arizona and adjacent Utah were the only exception. In this
area, fairly widespread rains of 1 to 4 inches were reported, resulting in
an improvement to [severe hydrological drought] conditions. The only other
area experiencing some improvement last week was the northern tier of
Washington, where unseasonably heavy rains of 1 to 3 inches...” raised
the assessment from moderate to abnormally dry agricultural and
hydrological drought conditions east of the Cascades.
“Across the southern tier of the West, scattered 1 to 3 inch rains fell
on the higher elevations of central Arizona and in adjacent parts of
southeastern Arizona and southwestern New Mexico. These rains, however,
were insufficient to improve the abnormally dry to extreme drought
conditions assessed last week, given that this is typically a relatively
wet time of year, and considering the magnitude of the region’s multi
year precipitation deficits. In fact, a small area of deterioration (to
extreme drought) was assessed in south central Arizona.”
“Rainfall was sparse across the remainder of the West, with little or
none falling on areas from the lower northern Intermountain West southward
through the Great Basin and southwestward across most of California. While
dry weeks during summer in these regions are quite common, the persistence
of low relative humidity, somewhat above normal temperatures, only spotty
rains, and slow but consistent surface moisture loss for the last few
months has led to increased fire danger and a westward expansion of
abnormally dry to extreme drought conditions across California, southern
Oregon, and Nevada.”
“Multi year precipitation deficits are very large in most locations from
the Rockies westward to the southern California coast, the Sierra Nevada,
and the Cascades. Only 64 to 75 percent of normal precipitation has fallen
on a vast majority of this large region since early August 1999. This
represents at least one typical year’s worth of precipitation missing
over the course of the last 5 years, with deficits approaching typical 2
year totals in much of the Intermountain West and desert Southwest. The
relatively recent persistence of below normal precipitation and humidity
combined with above normal temperatures has not helped the situation, with
reservoir storages declining at a rate exceeding the typical
climatological decline since May 1, even considering the dry summers
typically observed in most of the region, according to the Natural
Resources Conservation Service.”
East of the Rockies, heavy rains (4 to 6 inches) doused parts of central
and northeastern Colorado while moderate amounts (1 to 4 inches) were
fairly widespread across southeastern Montana, areas near and north of the
Black Hills, most of eastern and parts of central Colorado, and portions
of northern and eastern New Mexico. Most of these areas experienced a
significant improvement in drought classification, which now range from
abnormally dry to severe. In addition, drought conditions were eliminated
in part of extreme eastern New Mexico, southeastern Colorado, and extreme
southwestern Kansas. Other sections in the High Plains and eastern Rockies
did not receive as much precipitation, thus drought classifications were
unchanged from last week.
Across the Great Plains, drought conditions in North Dakota, most of
Nebraska, and adjacent parts of Kansas generally remained unchanged, but
moderate rains of 1 to 3 inches brought some localized improvements and
similar amounts led to measurable improvements in a large part of central
South Dakota, where such totals occur less frequently than they do farther
south. In contrast, significant rains again evaded southcentral Nebraska,
where drought classifications generally worsened. The 3 month rainfall
deficits in the Great Plains region total 1-4 inches less than normal for
the southwestern quarter of North Dakota, southcentral South Dakota, and
parts of northcentral and southeastern Nebraska, and long term deficits
remain substantial in much of the area. Over the last 5 years, between 10
and 20 inches less than normal precipitation has fallen from south central
South Dakota southward through northern Kansas, with 20 to 30 inch
deficits observed in central Nebraska and adjacent areas. For the central
tier of Nebraska and parts of northern Kansas, this represents more than a
typical year’s worth of precipitation missed since early August 1999.
Farther south, widespread moderate to heavy rains (1 to 4 inches)
eliminated abnormally dry conditions across the Texas Panhandle and most
of western Oklahoma, but abnormally dry conditions remain in central
Oklahoma, where only light rains fell last week.
The current issue of Time Magazine carries an article entitled, “Why the
West is Burning.” It notes the drought could “...easily turn 2004 into
one of the West’s worst fire years on record.” The August 16 issue
also states, “And no one knows when the drought will end. Scientists
believe this dry spell, which has plagued a broad swath of the West since
1999, is more typical of the region than its 60 million inhabitants would
care to admit.... Consider, for example, the 1922 compact that determines
the allocation of water from the Colorado River. Scientists have shown, by
studying tree rings and other historical evidence, that the allocation was
based on water flows that were the highest they had been for more than 475
years. By contrast, the flows since 1999 rank among the lowest. As a
result, Lake Powell, the giant reservoir created...by the Glen Canyon Dam,
stands some 60% below capacity and seems destined to fall even lower. No
wonder that states like Colorado -- whose rights to that water are trumped
by the rights of California, Nevada and Arizona -- are anxiously bracing
for a crisis.”
The article continues, “Caught off guard, political leaders and
water-resource managers have been turning to scientists for help. What do
researchers know about patterns of drought in North America? What do they
think occurred in the mid-1990s when a big chunk of the West abruptly
veered from wet to dry? And do they believe that the current shortfall in
precipitation is just a temporary dry spell or an ominous realignment of
the earth’s climate system?” The article goes on to discuss tree ring
and paleoclimatology research, sea surface temperatures, El Niño, La Niña,
climate models, global warming and future climate variability. Professor
Douglas Kenney, University of Colorado, observes, “Everyone’s pretty
clear that the earth’s getting warmer, but it’s unclear just what that
means. It might mean a wetter future or a dryer future. It might even mean
a wetter future with no net gain.” Dr. Philip Mote, a University of
Washington climatologist states, “Drought is more than a precipitation
deficit.” The problem is that “...you don’t have as much water as
you’d like at a given point in time.” The article concludes, “The
past is an imperfect lens through which to peer into the future, but
looking backward provides a glimpse, at least, of the sorts of extended
dry spells that those who live in this drought-prone region today should
be prepared to endure.” (J. Madeleine Nash/Sage, Time Magazine, August
16, 2004)....
