REVISIONS MADE TO THE MAJOR AQUIFERS FOR THE 2007 STATE WATER PLAN: The Edwards aquifer southern boundary has been updated based on new geochemical data. The boundary of the 1,000-mg/L line of equal dissolved solids concentration has been revised and moved both to the north and south of the previous boundary. More information on the new aquifer boundary can be found in the Texas 2007 State Water plan at <http://www.twdb.state.tx.us/home/index.asp>. In general, the Pecos Valley aquifer is defined by: (1) the occurrence of structural highs that have the potential to form barriers to groundwater flow and (2) the spatial extent of the Pecos Valley sediment. The Pecos Valley aquifer boundary differs from its former boundary in two ways. First, we revised the aquifer boundary, extending the aquifer into New Mexico to coincide with perceived hydrologic boundaries. Second, the old aquifer boundary excluded parts of Loving, Winkler, Ward, Pecos, and Crane counties where the alluvium is thin. This presents a problem to modeling groundwater flow because it incorrectly restricts access to the Pecos River, the main discharge zone. The new aquifer boundary better represent the geology as indicated by the 1:250,000 maps of the Geologic Atlas of Texas by including these areas of thinner alluvium. More information on the new aquifer boundary can be found in the Texas 2007 State Water plan at <http://www.twdb.state.tx.us/home/index.asp>. Aware of reports that not all of the mapped Seymour Aquifer held water, TWDB reviewed well information to determine which parts of the aquifer hold water and which parts do not. This review was done prior to developing the groundwater availability model for the Seymour Aquifer. In the process of developing the model, additional changes were made to the aquifer’s extent. Therefore, TWDB has changed the boundary so that only those sediments that are known to hold groundwater are part of the Seymour Aquifer More information on the new aquifer boundary can be found in the Texas 2007 State Water plan at <http://www.twdb.state.tx.us/home/index.asp>. The Trinity Aquifer extends beneath the Edwards (Balcones Fault Zone) Aquifer ending in the subsurface toward the west in eastern Uvalde County. This subsurface boundary in Uvalde County appears to coincide with the Sabinal River and, therefore, has a great amount of sinuosity and detail. Groundwater in the Trinity Aquifer in Uvalde County presumably flows beneath the Edwards (Balcones Fault Zone) Aquifer toward the south, in the same direction of the Sabinal River, which is probably why TWDB chose the river as the subsurface boundary of the aquifer. However, the boundary has much greater detail than what is known about the groundwater flow line. Therefore, TWDB has smoothed the shape of this line to better reflect the knowledge of its position. More information on the new aquifer boundary can be found in the Texas 2007 State Water plan at <http://www.twdb.state.tx.us/home/index.asp>. * The Edwards-Trinity Aquifer (outcrop) lines in West Texas were adjusted to lie adjacent to the updated Pecos Valley aquifer lines. Also, a small part of the outcrop was reclassified to subcrop in order to show the adjusted outcrop of the Pecos Valley aquifer which lies on top of the Edwards-Trinity in northern Pecos County. Also, a small part of the Ogallala aquifer in West Texas (specifically Andrews and Ector counties) was adjusted to lie adjacent to the updated Pecos Valley and Edwards-Trinity aquifer lines.
Texas Water Development Board, 19970800, SDETrims.DBO.Hydro_MajAquifer: Texas Water Development Board, Austin, Texas.Online Links:
- Service=sde:sqlserver:CHUCKNORRIS; Database=SDETrims; Version=dbo.DEFAULT
This is a Vector data set. It contains the following vector data types (SDTS terminology):
Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.000000. Longitudes are given to the nearest 0.000000. Latitude and longitude values are specified in Decimal degrees.
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.000000.
The flattening of the ellipsoid used is 1/298.257222.
Coordinates defining the features.
Sequential unique whole numbers that are automatically generated.
Mark Hayes, GISP (9 original aquifers) 1990 Peter George and Dr. Robert Mace, Geologists (Trinity aquifer revisions) 11/2006 Mark Hayes, GISP (Edwards and Edwards-Trinity aquifers revision) 11/2006 Ian Jones, Hydrologist (Pecos Valley aquifer revision) 11/2006 Cindy Ridgeway, Hydrologist (Seymour aquifer revision) 11/2006
(512) 936-0828 (voice)
(512) 936-0812 (FAX)
Mark.Hayes@twdb.state.tx.us
To update the delineations for the major aquifers of Texas for the purpose of adding them to the 1991 Water Plan.
Bureau of Economic Geology (BEG, Austin, Texas, Major Aquifers: Geologic Atlas Sheets (GAT), Bureau of Economic Geology, University of Texas, Austin, Texas, Austin, Texas.
Person who carried out this activity:
(512) 936-0828 (voice)
(512) 036-0812 (FAX)
Mark.Hayes@twdb.state.tx.us
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Data sources used in this process:
Horizontal positional accuracy is tested by visual comparison of hard copy check plots to the source materials and verifying the location of the data on-screen relative to other data layers in the same geographic area.
The Texas Water Development Board (TWDB) has identified and characterized 9 major and 21 minor aquifers in the state based on the quantity of water supplied by each. A major aquifer is generally defined as supplying large quantities of water in large areas of the state. Minor aquifers typically supply large quantities of water in small areas or relatively small quantities in large areas. The major and minor aquifers, as presently defined, underlie approximately 81 percent of the state. Lesser quantities of water may also be found in the remainder of the state.
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- Access_Constraints:
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(512) 936-0828 (voice)
mark.hayes@twdb.state.tx.us
Downloadable Data
| Data format: | SHP Size: 13.741 |
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| Network links: |
(512) 936-0828 (voice)
(512) 936-0812 (FAX)
Mark.Hayes@twdb.state.tx.us