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  • From: "Tradingpost" <tradingpost@gilanet.com>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] Western Aquifers Under Stress
  • Date: Thu, 26 Aug 2004 08:57:00 -0600

Western Aquifers Under Stress
http://www.geotimes.org/may04/feature_westernaq.html

Although the rate of water consumption in the United States has not increased
over the past five years, according to a recently released U.S. Geological
Survey report, water problems are prevalent across the country. On both
coasts, saltwater is intruding into coastal groundwater. And with widespread
urbanization and population growth, water is becoming scarcer everywhere in
the United States and particularly in the West, where irrigation and
groundwater mining are essential to meet demand.

As communities become more dependent on groundwater, they are facing a number
of scientific and policy challenges. Here, we highlight only two hotspots,
both in the West: the Denver Basin and the High Plains aquifer.

The Dwindling Denver Basin
State of the High Plains Aquifer

The Dwindling Denver Basin
In 1970, 12,000 people lived in Douglas County, Colo., just south of Denver.
Today, more than 200,000 people reside there, with the population expected to
double in the next 25 years. Like other counties in the Denver area, Douglas
relies on 10,000-year-old groundwater from bedrock aquifers located in the
Denver Basin for its water supply. The rapidly growing population, however,
is sucking the supply dry.

Aquifers that sustain suburban Denver, Colo., are dwindling at rates of 30
feet per year due to exponential population growth over the past few decades.
Highlands Ranch, pictured here, is an example of the growth of subdivisions
in Douglas County, south of Denver. Photo by Kirk Johnson.

In Castle Pines North, in Douglas County, water in wells is dropping an
average of 34 feet per year. In nearby Parker, water is dropping 30 feet per
year. And the story is similar in other municipalities. With well yields
already considerably reduced on many properties, the citizens face a dire
reality: “There is a finite amount of groundwater in this aquifer system,”
says Robert Raynolds, a geologist at the Denver Museum of Nature & Science.
At this rate, the south metropolitan area could run out of water — or at
least affordable water — in the next few decades. “We will have to find
alternate sources of water,” Raynolds says.

The 6,700-square-mile Denver Basin encompasses the entire Denver metropolitan
area as well as rural farmland along the eastern front of the Rocky
Mountains, says John Moore, a retired U.S. Geological Survey (USGS)
hydrologist. Four thick, predominantly sandstone aquifers comprise the
semi-arid basin and are, for the most part, hydraulically isolated from the
rivers (surface water) that drain from the mountains, Moore says. The four
aquifers, stacked atop one another, are also largely isolated from one
another by confining layers. And water moves very slowly through each
aquifer. These factors make recharge very difficult.

Together, the four aquifers contain an estimated 467 million acre-feet of
water (one acre-foot equals about 326,000 gallons of water), of which 269
million acre-feet are recoverable. The Arapahoe aquifer, at 400 to 700 feet
thick, is the most productive and most used aquifer in the region, extending
throughout two-thirds of the Denver Basin aquifer system. In 1985, 12,000
wells withdrew water from the Arapahoe, Dawson and Denver aquifers in Douglas
County. In 2001, that number reached 33,700, Moore says.

Ever since Denver residents drilled the first Arapahoe well in 1883,
withdrawal has exceeded recharge. But until the population began to explode,
having enough water was not a daily concern. While Denver itself does not
withdraw water from the underlying aquifers today (the city uses surface
water, which is recharged with snowmelt from the Rockies and rain), the
outlying areas rely mainly on the deep aquifers, especially the Arapahoe. And
with only 11 to 18 inches of annual precipitation, natural recharge of the
aquifer is not possible at the current rate of extraction, Moore says.

Researchers still do not fully understand the aquifer system, Raynolds says.
Private consultants, USGS, the state of Colorado and the Museum of Nature &
Science have all undertaken studies to better understand the stratigraphy of
the aquifers, to learn how long well levels can continue dropping at 30 feet
per year and what will happen next. “Part of the problem is that we’re facing
a lack of monitoring well data. And furthermore, we don’t know who is doing
what research in the Denver Basin,” Moore says. Thus, he and Raynolds
sponsored a workshop at the 2002 Geological Society of America (GSA) annual
meeting in Denver, and will again host one at the GSA meeting in Denver this
November to bring together various lines of research.

However, with water yield dropping from 500 gallons per minute to 100 gallons
per minute in individual wells (leaving bathroom showers with barely a
trickle), Moore says, time is of the essence for some metropolitan Denver
residents. Thus, city water planners are already moving forward with a plan,
based on previous studies and current information as it comes in from
geologists.

“All of us recognize that the water shortage is a problem,” says David
Little, who is in charge of planning and development for Denver Water, the
provider for the city of Denver. “It’s important to see if and how we can
help.”

As a first step, the municipalities have implemented conservation measures,
says Pat Mulhern, a water consultant and director of the South Metro Water
Supply Study Board. Some areas, he says, have based their conservation
measures from lessons learned in California, such as limiting days and times
of lawn-watering and heavily fining citizens who use significantly more water
than average; they then use those funds for additional conservation measures
(such as better irrigation systems).

The supply study board in a report released in January has also proposed a
plan to import water from Denver in years when the city has a surplus of
surface water (“wet years”). According to the report, a combination of
conservation and water-sharing is the best and most cost-effective option.

The board estimates that their plan, which would involve building pipelines
between Denver and the south metropolitan area to transport water and
reservoirs in which to store it, will cost around $3 billion between now and
2050. However, they estimate that the alternative — drilling more and deeper
wells — will cost closer to $4 billion by 2050. The plan suggests that these
costs would largely be passed along to consumers. Average tap fees (the price
levied on new service lines or wells) could rise as much as 100 to 500
percent with the water-sharing plan. However, drilling more and deeper wells
could increase tap fees by as much as 700 percent.

Even now, water costs in Douglas County are rising exponentially. Tap fees on
new homes have doubled over the past six years in some areas and keep rising
as development continues. And as much of the undeveloped land in the county
has already been sold and zoned, it is unlikely that development will slow
anytime soon.

The geosciences community, Raynolds says, needs to get more involved to help
the Denver metro area community at large. “We can draw from our experience
working in oil and gas reservoirs to help the water community here,” he says,
by figuring out just how much recoverable water is in the aquifers, best
extraction methods and so on. “This is a geological issue,” Raynolds stresses.

Megan Sever

Back to top State of the High Plains Aquifer

The High Plains aquifer spreads below 111 million acres of land, encompassing
eight states, and waters the nation’s breadbasket. Since the 1940s,
widespread groundwater pumping from the aquifer for irrigation has led to the
annual production of millions of tons of corn, winter wheat, sorghum and
other crops that feed cows and people around the world. But the water
resource is rapidly dwindling, threatening the livelihood of the western
states that rely on the High Plains aquifer for domestic, agricultural and
ecosystem water.

This irrigation system in Dundy County, Neb., is run on a center pivot with
tubes that drop down to the crop. More than 5 million acres of land were
irrigated in Nebraska in the late 1990s, out of almost 14 million irrigated
acres in the High Plains region. Photo by M.K. Landon, USGS.

The states — Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota,
Texas and Wyoming — have been working on the groundwater depletion problem
for half a century. Regulation of the aquifer, however, has been
controversial. Last October, the U.S. House of Representatives heard from
critics and supporters of a bill that would provide resources for joint
research between the states and the federal government (Geotimes, December
2003).

“One of the frustrations has been that every state is different, because of
state rights and so forth,” says Bill Hargrove, director of the Kansas Center
for Sustainable Agriculture and Alternative Crops (CSAAC) at Kansas State
University. “So far there hasn’t been much effort to work together,” Hargrove
says.

To aid the states in assessing the High Plains aquifer, the U.S. Geological
Survey recently released a report detailing depletion rates across the
aquifer and general reviews of what each state is doing to protect the
resource. Overall, the report says, the aquifer has lost 6 percent of its
stored water since the 1940s, with higher losses in many large swaths and
slight increases in a few small pockets of the aquifer. Some regions of the
aquifer may soon contain no economically recoverable groundwater at all.

Across the aquifer, composed mostly of the Ogallala Formation, annual pumping
from 1949 to 1974 increased from 4 to 19 million acre-feet. After 1974, the
amount of water pumped annually out of the High Plains aquifer stabilized,
according to the report. Nevertheless, over the past half century or so, the
High Plains aquifer declined by about 200 million acre-feet (equivalent to
approximately 65.2 trillion gallons — about as much as California’s annual
rainfall).

“There’s been a tremendous amount of change in water-use technology on the
High Plains from the time that development began,” says Bob Hirsch, associate
director for water at USGS. The changes generally do not stem from
regulations but are “basically economic,” he says. The cost of pumping is
proportional to how high water users have to lift the groundwater. “In the
1970s, they faced high energy costs and economized by changing technology,
and to some extent took some land out of irrigation.”

Other changes led to higher efficiency in applying water to crops, Hirsch
says. High-pressure sprinklers, which had upward-facing heads that sprayed
water up and out over fields, also resulted in water loss through
evaporation. These gave way to downward-facing sprinklers at lower pressures,
as well as to conservation measures. In some places, farmers water according
to different crops’ needs and have introduced technology such as drip
irrigation, says Tom Huntzinger, chief of water appropriations in the Kansas
Division of Water Resources (DWR).

Such shifts are clear from the data collected by state, local and federal
agencies (including USGS), compiled by USGS, to compare the “predevelopment”
aquifer to its current state. Using records from some 20,000 wells, some of
which extend back to 1920, the new USGS report summarizes groundwater storage
from the beginning of high impact irrigation in the 1940s through 2000. The
water-use data also come from flowmeter measurements and estimates of the
amount of irrigation water required by certain crops.

The largest losses of groundwater took place in Texas and Kansas, where the
aquifer is thinner and deeper below the surface, and where surface recharge
from rain or from the return flow of irrigation water is less. In Texas, the
aquifer stores 27 percent less water than it did 50 years ago; Kansas’
portion now stores 16 percent less.

Considering the extensive use of the aquifer, the overall decrease of only 6
percent of its volume is encouraging, says Jim Conkwright, manager of the
High Plains Underground Water Conservation District No.1, in Lubbock, Texas.
However, according to water district estimates, he says, the Lubbock region —
where a large portion of the economy is based on agriculture — has used at
least half of the aquifer’s local groundwater during the past 50 years.

The Lubbock-based water district is working to quantify recent decreases in
irrigation water use. However, sustainability in this southernmost portion of
the aquifer may be unattainable, Conkwright says. Some regional farmers are
returning to dryland farming methods, he says, but even if crop irrigation
were significantly curtailed, local municipal water use would still exceed
recharge rates to the aquifer. The district is sponsoring research by local
agricultural research stations and universities to develop crops that require
less water, and it continues to improve efficiency for water delivery.

Despite similar activities in Kansas, Huntzinger says, “many areas in
west-central Kansas are approaching depletion. Large-scale irrigation as in
the past is no longer applicable.” Because the Kansas DWR regulates the
state’s water use — and USGS uses the state’s detailed data on the High
Plains aquifer — the report is not a surprise from a local point of view,
Huntzinger says, but the multistate perspective is useful. “Obviously we’re
going to consider what’s going on across our borders; we need to know where
the water is flowing,” he says.

Some slight groundwater level increases took place mostly in Nebraska, says
Virginia McGuire of the USGS in Lincoln, Neb., and the report’s lead author.
But these increases were partly due to losses from leaking irrigation canals
that recharged shallow portions of the aquifer, or from irrigation runoff
that fed back into the aquifer near rivers and streams. Other possible
explanations include less intensive irrigation in those areas and higher
rates of precipitation over the past few years.

These regional differences have made regulation of the aquifer challenging,
says Hargrove of the CSAAC. In Kansas, he says, some places are basically
dry, others have a 20- to 50-year water supply, and still other areas could
yield groundwater for a century or more at current use rates. “Coming up with
policy that fits everybody has been the frustration,” he says.

Different levels of drawdown on the aquifer may also lead to varying effects
on water quality, says Kevin Dennehy, USGS project manager of the High Plains
Regional Ground Water Quality study, under the National Water Quality
Assessment program. Declining water levels, he says, “have the potential to
adversely affect water quality of the High Plains aquifer, and that’s
something I don’t think is being adequately explored.”

Wells ideally draw water from the cleanest and most productive zones, which
in the High Plains aquifer is usually the midpoint, Dennehy says. But
decreasing an aquifer’s saturated thickness might affect the water likely to
be mined. “Water that did not previously discharge from deeper units might do
so,” he says, and that deeper groundwater might contain more dissolved
chemicals or salts. And, he continues, “the upper part of the aquifer is
vulnerable to the effects of human activities,” such as the application of
pesticides or other chemicals that travel to the aquifer via recharge.

Dennehy also says that the need remains for an update to the previous
in-depth assessment of the aquifer. The last full USGS report dates to 1978,
and the legislation currently under consideration by Congress would
contribute to extensive and detailed geologic and hydrologic characterization
of the aquifer.

No matter what happens with that legislation, the most recent USGS report is
helpful, says Huntzinger of Kansas DWR. “I hope that this will allow people
outside the Ogallala to realize how important this aquifer is to this part of
the country.”




  • [Livingontheland] Western Aquifers Under Stress, Tradingpost, 08/26/2004

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