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Ogallala Formation (containing High Plains Aquifer): Deposited over 10 million years agoCoarse-grained sand, gravel, fine clay, silt, and sand174,000 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
Source: USGS, 1997
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, 1996
Source: USGS, 2001c 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, 2000
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
• 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
Source: USGS, 2000b Source: USGS, 1999
Precipitation is the primary cause of recharge to the High Plains Aquifer
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.
Discharge > Recharge: because of human-induced discharge from wells for irrigation, leading to water table level decreases.
Source: USGS, 1997
Chart source: USGS, 2002
Chart source: USGS, 2001
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
Source: USGS, 2001
Madison LimestoneBlack Hills, South Dakota
• Madison limestone deposited about 300 mya as the bottom of a great inland sea.
• 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
• Madison Aquifer extends 210,000 square miles into ND, NE, WY, MT and SD.
• Confined
Figure 26, USGS, 1984Potentiometric surface
Source: USGS, 2001
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.
A significant amount of recharge tothe Madison Aquifer comes from streamflow losses over limestone outcroppings.Source: Journal of Hydrology, 1999
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)
Source: USGS, 2001
Madison Aquifer Flow Paths, Recharge Areas and Discharge Areas
Hydrologic Budget for Madison Aquifer
Madison Aquifer Recharge• Stream flow losses and precipitation at limestone outcroppings• Leakage from adjacent aquifers• Ground water inflows
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, 2001
Source: USGS, 2001b
Total:
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• Unconfined
• Recharge through infiltration and groundwater flow
• Rate:
• Used primarily for agricultural irrigation
• Water level falling
Madison• Confined
• Recharge through stream flow losses and precipitation at limestone outcroppings
• Rate:
• Used primarily for municipal and private consumption
• Storage level stable and rising locally