Transcript Madison

Ogallala Formation (containing High Plains Aquifer):
Deposited over 10 million years ago
Coarse-grained sand, gravel, fine clay, silt, and sand
174,000 square miles and 3.270 billion acre-feet of water as of 1990
(65% NE, 12% TX, 10% KA, 4% CO, 3.5% OK, 2%SD, 2% WY, 1.5% NM)
Source: High Plains Water District #1
• X% of aquifer showing water
level changes.
• More in southern half because
farmers started using
groundwater for irrigation in
Texas in 1940’s, and trend
moved north.
• Average water level decline from
1940-1980: 0.25 feet/year.
Source: USGS, 1996
Decrease in rate of water level
decline from 0.25 ft/yr to 0.11 ft/yr
after 1980.
• Precipitation amounts above
average
• More efficient irrigation
technology
• Regulations on groundwater
withdrawals
• Decline of agricultural commodity
prices and increased production
costs leading to less agricultural
production
Source: USGS, 1997
Source: USGS, 1996
These maps from 1980 data show a relationship between irrigated land and
aquifer water level declines in the southern part of the High Plains Aquifer.
Percentage of irrigated land in 1980
Source: USGS, 2001c
Source: USGS, 1996
These maps from 1997 data show a relationship between saturated thickness
and depth to the water table, especially in the northern part of the High Plains
Aquifer.
Depth to water table in 1997
Saturated thickness in 1996--97
Source: USGS, 2001c
Source: USGS, 2000
• Projected well yields for
High Plains Aquifer for
1980-2020.
• Based on current
economic trends and
government policies –no
new conservation
measures.
Source: USGS, 1988
High Plains Aquifer Recharge
Precipitation is the primary cause of recharge to the High Plains Aquifer
Source: USGS, 1999
Source: USGS, 2000b
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High Plains Aquifer Recharge
PRECIPITATION
Seepage from streams, canals, and reservoirs, and irrigation return flow.
Rate (from precipitation and irrigation) is 0.25-0.50 inch/yr in the western portion of
the High Plains region to 4-6 inches in the eastern portion of the High Plains region.
High Plains Aquifer Discharge
• Evapotranspiration where the water table is near the land surface.
• Seepage where the water table intersects the land surface.
Chart source: USGS, 2002
Discharge > Recharge: because of human-induced discharge from
wells for irrigation, leading to water table level decreases.
Source: USGS, 1997
This graph shows the ages of the rocks that make up the High Plains and Madison
Aquifers.
About 10 MYA
About 340 MYA
Source: http://seaborg.nmu.edu/earth/Life.html
Chart source: USGS, 2001
Madison Limestone
Black Hills, South Dakota
• Madison limestone deposited about
300 mya as the bottom of a great
inland sea.
Source: USGS, 2001
• Black Hills uplift 50 mya, erosion
eventually exposing older igneous rocks
in center.
• Now Madison limestone is exposed
around the perimeter of the Black Hills.
•The thickness if the Madison
Formation increases from south to
north and ranges from 0-1,000 feet.
(USGS, 2001b)
Madison Aquifer Potentiometric Surface
Figure 26, USGS, 1984
Potentiometric surface
• Madison Aquifer extends 210,000 square miles into ND, NE, WY, MT
and SD.
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Confined
A significant amount of recharge to
the Madison Aquifer comes from stream
flow losses over limestone outcroppings.
Source: Journal of Hydrology, 1999
The Madison Aquifer is confined above and below by layers of rock with much
lower hydraulic conductivity. Below the Madison Aquifer there is one other aquifer and
there are three above it. These aquifers are composed of sandstone and/or limestone
and they were deposited roughly 530-130 mya (http://seaborg.nmu.edu/earth/Life.html). Below all the
aquifers are confining layers of impermeable igneous and metamorphic rocks.
Source: USGS, 2001
Madison Aquifer Flow Paths, Recharge Areas and Discharge Areas
Source: USGS, 2001
The Madison Limestone is hydraulically connected to the Minnelusa Formation in the
eastern most part of the Madison Aquifer, in the Dakotas. Here groundwater
discharges from the Madison to recharge the Minnelusa Aquifer. (USGS, 1984)
Hydrologic Budget for Madison Aquifer
Source: USGS, 2001
Madison Aquifer Recharge
• Stream flow losses and precipitation at limestone outcroppings
• Leakage from adjacent aquifers
• Ground water inflows
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Total:
Madison Aquifer Discharge
Artesian and headwater spring flow
Leakage to adjacent aquifers
Ground water outflows
Well withdrawal for municipal and personal consumptive uses
Source: USGS, 2001b
Source: USGS, 2001
Water levels in the Madison Aquifer were falling from 1987-1992, but they have been
rising since about 1993 all over the Black Hills. (USGS, 2001)
Major differences between High Plains and Madison
Aquifers
High Plains
Madison
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Unconfined
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Confined
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Recharge through infiltration and
groundwater flow
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Rate:
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Recharge through stream flow
losses and precipitation at
limestone outcroppings
Rate:
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Used primarily for agricultural
irrigation
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Used primarily for municipal and
private consumption
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Water level falling
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Storage level stable and rising
locally