andrei verdeanu - high plains ground water depletion

8/3/2019 Andrei Verdeanu - High Plains Ground Water Depletion

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Ground WaterDepletion

-The High Plains Aquifer

(Ogallala Aquifer)-

Verdeanu Andrei


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Objectives I have tried to achieve in presenting this project:

Introduction:

- Presenting the geographical location and bioclimatic characteristics of the area;- The aquifers general geological characteristics;

Main contents:

- The water regime recharge and discharge;- Economical aspects of the issue agricultural impact of the problems;- Depletion and pollution of the aquifer;

Conclusions.


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Ground Water Depletion

-The High Plains Aquifer (Ogallala Aquifer)-

The High Plains are a subregion of the Great Plains, located mostly in the Western

United States, but also partly in the Midwest states of Nebraska, Kansas, and South Dakota,

generally encompassing the western part of the Great Plains before the region reaches the

Rocky Mountains. The High Plains are lying in southeastern Wyoming, southwestern South

Dakota, western Nebraska, eastern Colorado, western Kansas, eastern New Mexico, western

Oklahoma and northwestern Texas. From east to west, the High Plains rise in elevation from

around 1,160 feet (350 m) to over

7,800 feet (2,400 m).

The Great Plains area

location and the High Plains

Aquifer and the states

containing it, figures 1 and 2.

Figure 1

The High Plains are characterised by

a semi-arid climate, receiving between

1020 inches (250510 mm) of

precipitation annually. The vegetation

coverage is generaly represented by

shortgrass prairie, prickly pear cacti and

scrub formations, with occasional buttes

or other rocky outcrops.

Figure 2


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The High Plains aquifer system underlies 111.4 million acres (460,000 square

kilometers) of surface, being the leading geologic formation in the aquifer system. Although

there are several other minor geologic formations in the High Plains Aquifer System, such as

the Tertiary Brule and Arikaree and the Dakota formations of the Cretaceous, these several

units are often referred to as the Ogallala

Aquifer.

Tipical aspect from the Great

Plains Area, part of the North American

Prairies Province, figure 3

Figure 3

The Ogallala is composed

primarily of unconsolidated,

poorly sorted clay, silt, sand, and

gravel with groundwater filling

the spaces between grains below

the water table . The aquifer was

laid down about 10 million years

ago by fluvial deposition from

streams that flowed eastward

from the Rocky Mountains

during the Pliocene epoch. It is an

unconfined aquifer, and virtually

all recharge comes from

rainwater and snowmelt. As the

High Plains has a semiarid

climate, recharge is minimal.

Figure 4


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Recharge varies by amount of precipitation, soil type, and vegetational cover and averages

less than 25 millimeters (1 inch) annually for the region as a whole. We can observe in figure 4 that

the aquifer would overlap over the 35 up until 100 mm of mean annual precipitations range, thus

passing through arid to mild conditions, west to east.

In a few areas, recharge from surface water diversions has occurred. Groundwater does flow

through the High Plains Aquifer, but at an average rate of only 300 millimeters (12 inches) per day.

Hypsometric map and satellite image of the aquifer area, figures 5 and 6.

Figure 5. Figure 6.


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The depth to the water table of the Ogallala Aquifer varies from actual surface discharge to

over 150 meters (500 feet). Generally, the aquifer is found from 15 to 90 meters (50 to 300 feet) below

the land surface. The saturated thickness - figure 7, also varies greatly. Although the average

saturated thickness is about 60 meters (200 feet), it exceeds 300 meters (1,000 feet) in west-central

Nebraska and is only one-tenth that in much of western Texas. Because both the saturated thicknessand the areal extent of the Ogallala Aquifer is greater in Nebraska, the state accounts for two-thirds of

the volume of Ogallala groundwater, followed by Texas and Kansas, each with about 10 percent.

The Ogallala

Aquifer, whose total

water storage is about

equal to that of Lake

Huron in the Midwest, is

the single most

important source of

water in the High Plains

region, providing nearly

all the water for

residential, industrial,

and agricultural use.

Because of widespread

irrigation, farming

accounts for 94 percent

of the groundwater use.

Irrigated agriculture

forms the base of the

regional economy. It

supports nearly one-fifth

of the wheat, corn,

cotton, and cattle

produced in the United

States. Crops provide

grains and hay for

confined feeding of cattle

and hogs and for dairies.

Figure 7


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The cattle feedlots support a large meatpacking industry. Without irrigation from the

Ogallala Aquifer, there would be a much smaller regional population and far less economic

activity.

Crop Circles in Kansas

Photo courtesy of NASA Earth Observatory

Because of the Ogallala, the High Plains is the leading irrigation area in the Western

Hemisphere. Overall, 5.5 million hectares (nearly 13.6 million acres) are irrigated in the Ogallala

region. The leading state irrigating from the Ogallala is Nebraska (46%), followed by Texas (30%) and

Kansas (14%).

The Depletion Process

The Ogallala Aquifer is being both depleted and polluted. Irrigation withdraws much

groundwater, yet little of it is replaced by recharge. Since large-scale irrigation began in the 1940s,

water levels have declined more than 30 meters (100 feet) in parts of Kansas, New Mexico, Oklahoma,

and Texas. In the 1980s and 1990s, the rate of groundwater mining , or overdraft, lessened, but still


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averaged approximately 82 centimeters (2.7 feet) per year. Increased efficiency in irrigation continues

to slow the rate of water level decline. State governments and local water districts throughout the

region have developed policies to promote groundwater conservation and slow or eliminate the

expansion of irrigation. Generally, management has emphasized planned and orderly depletion, not

sustainable yield. Depletion results in reduced irrigation in areas with limited saturated thickness andincreased energy cost in all areas as the depth to water increases. Center-pivot sprinklers are among

the irrigation methods used in the High Plains. Large quantities of groundwater pumped from the

Ogallala Aquifer allows these semiarid western lands to yield abundant harvests.

In parts of the area,

farmers began using groundwater for irrigation

extensively in the 1930s and

1940s. Estimated irrigated

acreage in the area overlying

the High Plains aquifer

increased rapidly from 1940

to 1980 and changed slightly

from 1980 to 2002: 19492.1

million acres, 198013.7



million acres. Irrigated acres

in 2002 were 12 percent of

the aquifer area, not

including the areas with little

or no saturated thickness.

Water withdrawal, figure 8

and water-level changes

related to the irrigated

surface evolution, figure 9

Figure 8


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Figure 9

Water-level changes in the aquifer figure 10, result from an imbalance between discharge

and recharge. Discharge is primarily ground-water withdrawals for irrigation. Discharge also

includes evapotranspiration, where the water table is near the land surface, and seepage to streams

and springs, where the water table intersects with the land surface. Recharge is primarily from

precipitation. Other sources of recharge are irrigation return flow and seepage from streams, canals,

and reservoirs.


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Figure 10


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The average specific yield for the High Plains Aquifer is about 0.15. This means that only 15

percent of all the water available in the aquifer can be recovered using irrigation pumps, while the

rest remains unused and locked up in the unsaturated zone . Groundwater depletion problems could

be forestalled if this presently nonrecoverable water could be forced to the saturated zone . One

experimental means of accomplishing this is by injecting air into the unsaturated zone, which breaksdown capillary action and permits the movement of water down to the saturated zone. Air injection

experiments have shown positive results for very localized areas. However, the widespread

applicability of this technology has not yet proven effective.

Figure 11


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The map is based on water levels from 3,682 wells, which were measured in the agricultural

predevelopment period and in 2005, and other previously published data in areas with few

predevelopment water levels.

The areas with few predevelopment water levels are in the central part of the Nebraska

Panhandle, west-central Nebraska, and southeastern Wyoming. The water-level changes from

predevelopment to 2005 ranged between a rise of 84 feet and a decline of 277 feet. Area-weighted,

average water-level change from predevelopment to 2005 was a decline of 12.8 feet. Approximately

25 percent of the aquifer area had more than 10 feet of water-level decline from predevelopment to

2005; 17 percent had more than 25 feet of water-level decline, and 9 percent had more than 50 feet of

water-level decline. Approximately 2 percent of the aquifer area had more than 10 feet of water-level

rise from predevelopment to 2005.

In response to these water-level declines, the U.S. Geological Survey (USGS), in cooperation

with numerous Federal, State, and local water-resources agencies, began monitoring more than 7,000

wells in 1988 to assess annual water-level change in the aquifer. A report by the USGS, Water-Level

Changes in the High Plains Aquifer, Predevelopment to 2005 and 2003 to 2005 (McGuire, 2007),

shows the areas of substantial water-level changes in the aquifer from the time prior to substantial

ground-water irrigation development (predevelopment or about 1950) to 2005. Ground-water

withdrawals for irrigation and other uses are compiled and reported by the USGS and agencies in

each State about every 5 years. Ground-water withdrawals from the High Plains aquifer for irrigation

increased from 4 to 19 million acre-feet from 1949 to 1974. Ground-water withdrawals for irrigation in

1980, 1985, 1990, and 1995 were from 4 to 18 percent less than withdrawals for irrigation in 1974.

Ground-water withdrawals from the aquifer for irrigation in 2000 were 21 million acre-feet (McGuire,

2007).

In addition to the water withdrawal and depletion, pollutants and contamination is another

important issue. Groundwater contamination in the Ogallala became an issue in the 1990s. In its

natural state, the High Plains Aquifer is, for the most part, of high quality. The water is generallysuitable for domestic use, stock watering, and irrigation without filtration or treatment. Surveys of

groundwater samples have detected traces of pesticides and nitrates. Sources include irrigated

agriculture and confined livestock feeding operations. The percolation rates of contaminants from the

surface to the water table have not been established in the areas where polluted water has been

found, but a map refering to the aquifers susceptibility of chemical compounds transit to the water

table has been made figure 12


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Analysing the

resulting distribution of

the areas into the

aquifer, tells us that the

coverage area and the

possible recharge areas

at surface are mostly safe

from the reach of

pollutants, at least in thenearby future. The most

prone areas are those

where the water table

meets the topographic

surface through high

piezometric levels,

surfacing or even rises

over the surface, areas

where direct contact

between the phreatic

level and the

topographical surface

are appearing (river

beds, alluvial plains and

areas presenting

advanced errosion

processes).

Figure 12


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Conclusions:

First of all, there should be acknowledged that the aquifer and the related resourcess health

status can still be improved, even saved, in time. Not everything is lost, yet. But action must be taken

quickly. One could say that these times are the last chance available to restore the balance that has

been deply shaken.

The importance of protecting the water resources in this area is even more significant,

considering the geographical location and the climatic characteristics of the aquifer area. Being

situated in an arid area, makes things even more difficult. As stated above, the replenishing and

recharge given by nature are minimal in this area. Relying only on the pluvial input and the even

weaker nival recharge is not an option. From a more religious perspective, people who have settled

around these areas should much appreciate the miracle that has been given to them, in the greatexpanse of these plains. This aquifer represents an unexpected chance for social development,

practically binding the population to the areas inhabited and giving a special character to the lifestyle

and nature of the people.

The future economy of the High Plains and the United States for that matter, depends

heavily on the Ogallala Aquifer, the main source of water for all uses. Economically speaking, the

importance of the water supplied by the aquifer is critical. Even medium variations of the supply, on

mid-term can profoundly affect the countrys economy and agricultural production. A critical balance

point has been achieved. This point was met because once the water was made accessible to industry,agriculture and large scale use, the principle of high production efficency but severe consumption of

the resources has been blindly applied. Until recent years, the depletion was not given the much

needed attention and care. Sensing that the depletion has rised over a certain level, some measures

started to be taken. This is a good thing, but are these measures taken in the context of the same

principle of mass production mass consumption of the resources? Or things have been revised?

Some could be curious to know the answer, but lets hope that the people managing these important

resources know the answer themselves and have chosen the right way... Otherwise, they will realise

too late what serious damage has been done to this valuable resource... Maybe the deadline will raise

some heads, for changing the plans. Who knows...

Otherwise said, the Ogallala will continue to be the lifeblood of the region only if it is managed

properly to limit both depletion and contamination.


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Sources:

- Alley, W.M., Reilly, T.E., and Franke, O.L., 1999, Sustainability of ground-water resources:U.S. Geological Survey Circular 1186;

- Kromm, David E., and Stephen E. White, eds. Groundwater Exploitation in the High Plains.Lawrence: University Press of Kansas, 1992;

- White, Stephen E., and David E. Kromm. "Local Groundwater Management Effectiveness inColorado and Kansas Ogallala Region." Natural Resources Journal 35 (1995);

- McGuire, V.L., 2007, Water-level changes in the High Plains aquifer, predevelopment to 2005and 2003 to 2005: U.S. Geological Survey Scientific Investigations Report 20065324;

- United States Geological Survey -http://ne.water.usgs.gov;- Geology -http://geology.com;- Water Encylopedia -http://www.waterencyclopedia.com;- American Society of Agronomy -https://www.agronomy.org/;- Kansas Department of Agriculture -http://www.ksda.gov/;- University of Nebraska Lincoln -http://www.unl.edu/;- NASA Earth Observatory -http://earthobservatory.nasa.gov/.
http://ne.water.usgs.gov/http://ne.water.usgs.gov/http://ne.water.usgs.gov/http://geology.com/http://geology.com/http://geology.com/http://www.waterencyclopedia.com/http://www.waterencyclopedia.com/http://www.waterencyclopedia.com/https://www.agronomy.org/https://www.agronomy.org/https://www.agronomy.org/http://www.ksda.gov/http://www.ksda.gov/http://www.ksda.gov/http://www.unl.edu/http://www.unl.edu/http://www.unl.edu/http://earthobservatory.nasa.gov/http://earthobservatory.nasa.gov/http://earthobservatory.nasa.gov/http://earthobservatory.nasa.gov/http://www.unl.edu/http://www.ksda.gov/https://www.agronomy.org/http://www.waterencyclopedia.com/http://geology.com/http://ne.water.usgs.gov/

andrei verdeanu - high plains ground water depletion

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