Spatial data for Eurycea salamander habitats associated With three aquifers in south-central Texas


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Spatial data for Eurycea salamander habitats associated With three aquifers in south-central Texas

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Title:
Spatial data for Eurycea salamander habitats associated With three aquifers in south-central Texas
Series Title:
Data Series
Creator:
Heitmuller, Franklin T.
Reece, Brian D.
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U.S. Geological Survey
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Language:
English

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serial ( sobekcm )

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Eurycea salamander taxa comprise 12 known species that inhabit springs and caves in south-central Texas. Many of these are threatened or endangered species, and some are found only at one location. A number of the neotenic salamanders might be at risk from habitat loss associated with declines in ground-water levels. Eurycea salamander habitats are associated with three aquifers in south-central Texas: (1) the Edwards-Trinity (Plateau) aquifer, (2) the Edwards (Balcones Fault Zone) aquifer, and (3) the Trinity aquifer. The Edwards (Balcones fault zone) aquifer is commonly separated into three segments: from southwest to northeast, the San Antonio segment, the Barton Springs segment, and the northern segment. The Trinity aquifer south of the Colorado River can be divided into three permeable zones, the upper, middle, and lower zone. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, developed this report (geodatabase) to aggregate the spatial data necessary to assess the potential effects of ground-water declines on known Eurycea habitat locations in south-central Texas. The geodatabase provides information about spring habitats, spring flow, cave habitats, aquifers, and projected water levels.
Original Version:
Data Series, Vol. 243 (2006).

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University of South Florida Library
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University of South Florida
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This object is protected by copyright, and is made available here for research and educational purposes. Permission to reuse, publish, or reproduce the object beyond the bounds of Fair Use or other exemptions to copyright law must be obtained from the copyright holder.
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K26-05187 ( USFLDC: LOCAL DOI )
k26.5187 ( USFLDC: LOCAL Handle )

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Data Series 243 Spatial Data for Eurycea Salamander Habitats Associated with Three Aquifers in South-Central Texas By Franklin T. Heitmuller and Brian D. Reece Introduction Eurycea salamander taxa comprise 12 known species that inhabit springs and caves in south-central Texas (Chippinda le and others, 2000). Many of these are threatened or endangered species, and some are found only at one location. A number of the neotenic salamanders might be at risk fr om habitat loss associated with declines in ground-water levels. Eurycea salamander habitats are associated w ith three aquifers in south-central Texas: (1) the Edwards-Trinity (Plateau) aquifer, (2) the Edwards (Balcones Fault Zone) aquifer, and (3) the Trinity aquifer. The Ed wards (Balcones fault zone) aquifer (Ashworth and Hopkins, 1995) is commonly separated in to three segments: from southwest to northeast, the San Antonio segment, the Barton Springs segment, and the northern segment. The San Antonio segment is hydrol ogically separated from the Barton Springs segment by a ground-water divide near Ky le in Hays County. The Barton Springs segment is hydrologically separated from the northern segment by the Colorado River. The Trinity aquifer south of the Colorado Ri ver can be divided into three permeable zones. Barker and Ardis (1996) referred to these zones as the upper, middle, and lower zone. North of the Colorado River, permeable units of the Trinity aquifer commonly are referred to by their geologic-unit name. A prin ciple geologic unit of the Trinity aquifer in this area is the Glen Rose Limestone, which was referred to as the Glen Rose aquifer in the USGS Source Water Assessment Program (SWAP) (N.A. Houston, U.S. Geological Survey, unpub. data, 2005). Purpose and Scope The U.S. Geological Survey (USGS), in cooperation with the U.S. Fish and Wildlife Service (USFWS), developed this repor t (geodatabase) to aggregate the spatial data necessary to assess the potential effects of ground-wate r declines on known Eurycea habitat locations in south-central Texas. The geodatabase provid es information about spring habitats, spring flow, cave habitats, a quifers, and projected water levels for the middle zone of the Trinity aquifer in south-cen tral Texas. Projected water levels are only for the middle zone of the Trinity aquifer because that zone is the focus of a threedimensional, numerical ground-water-flow model of the Trinity aquife r in south-central Texas (Mace and others, 2000). The geodatabase does not address the issue of whether Eurycea habitats will be adve rsely affected by ground-wate r withdrawals nor does it assign vulnerability to particular habitat locat ions. These data were produced or extracted in a geographic information system (GIS). Approach Eurycea spring and cave habitat locations were provided to the USGS by the USFWS in shapefile format. These locations and associated tabular data were organized 1

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in a geodatabase. Spring habita t locations were compared to known spring locations in a GIS (Heitmuller and Reece, 2003), and data for those that matched were added to the geodatabase. A 60-meter digital elevation model was used to assign an elevation to spring and cave orifices. Recent (late 1990s) and proj ected (to 2050) water-level data for the middle zone of the Trinity aquifer (Mace and others, 2000) were obtained from the Texas Water Development Board (TWDB) in tabular and shapefile format, and these data were imported into the geodatabase. Existing GIS da tasets of aquifer structure and properties were obtained from the SWAP (N.A. Houston, U.S. Geological Survey, unpub. data, 2005), and these were used to identify th e source of water to spring habitats. The sources of water to spring habitats were identified in a GIS using spring orifice elevations, an arbitrarily assign ed spring-orifice depth, and SWAP aquifer datasets. First, spring-orifice depth was arbitr arily set at 100 feet. This value is expected to adequately represent the maximum depth of springs in the re gion, although several of the largest springs might exceed this depth. Second, SWAP GIS datasets were used to detect (1) all aquifers encountered between the land-surface and the 100-foot depth of the spring, (2) the vertical order of the aquifers, and (3) the percentage of spring-orifice depth accounted for by each aquifer encountered. Prec edence was given in assigning an aquifer as water source to the aquifer closest to land surface or to aquifers that accounted for the largest percentage of springorifice depth. Most aquifers were automatically selected during the computational proced ure; however, a few were manually selected to ensure appropriate designation. Quantitative values characterizing aquifer structure and properties extracted from the SWAP datasets were added to the geodatabase. Finally, using the TWDB dataset derived from the Trinity aquifer ground-water-flow model of Mace and others (2000), recent (late 1990s) a nd projected (to 2050) ground-water levels were extracted for spring habitats associated with the middle zone of the Trinity aquifer. Spatial Data One-hundred eighty-one springs a nd 36 caves were identified as Eurycea habitats in south-central Texas (fig. 1). Using the SWAP aquifer datasets and nomenclature, 68 springs flow from the Edwards-Trinity (Plateau) aquifer, 53 springs flow from the upper zone of the Trinity aquifer, 24 springs flow from the Edwards (Balcones fault zone) aquifer—north (northern segment), 19 springs flow from the middle zone of the Trinity aquifer, 8 springs flow from the Edwards (Balcones fault zone) aquifer—south (San Antonio and Barton Springs segments combined), 8 springs flow from the Glen Rose aquifer, and 1 spring was of indeterminate source. For those springs flowing from the middle zone of the Trinity aquifer, projected water levels for both average recharge conditions and drought-of-record conditions (Mace and others, 2000) show drawdown at every spring. In 2050 under average recharge co nditions, aquifer water levels at 15 of 19 springs are projected to decline from recen t (late 1990s) water leve ls by more than 10 feet; in 2050 under drought-of-re cord conditions, aquifer water levels at 12 of 19 springs are projected to decline from current (late 1990s) by more than 50 feet. Projected water levels for each decade from 2010 to 2050 are in the geodatabase for springs flowing from the middle zone of the Trinity aquifer. 2

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101W 101W 100W 100W 99W 99W 98W 98W 97W 97W 29N 29N 30N 30N 31N 31N San Antonio Austin TEXAS 03 06 09 01 2 0 M I L E S 0306090120KILOMETERS Spring (habitat) Cave (habitat) Glen Rose aquifer Upper zone of the Trinity aquifer Middle zone of the Trinity aquifer Edwards (Balcones fault zone) aquifer south Edwards (Balcones fault zone) aquifer north Edwards-Trinity (Plateau) aquifer Base modified from Texas Natural Resources Information System (TNRIS) digital data at 1:24,000 (2005) Albers equal area projection parameters Central meridian: -100.0 Standard parallel 1: 34.91666667 Standard parallel 2: 27.41666667 Latitude of origin: 31.16666667KyleC olorado Riv e r Figure 1. Eurycea salamander habitats in south-central Texas. References Ashworth, J.B., and Hopkins, J., 1995, Aquifers of Texas: Texas Water Development Board Report 345, 69 p. Barker, R.A., and Ardis, A.F., 1996, Hydrogeol ogic framework of the Edwards-Trinity aquifer system, west-central Texas, in Regional Aquifer-System Analysis— Edwards-Trinity aquifer system: U.S. Geological Survey Professional Paper 1421–B, 61 p. Chippindale, P.T., Price, A.H., Weins, J.J., and Hillis, D.M., 2000, Phylogenetic relationships and systematic revision of central Texa s hemidactyliine plethodontid salamanders: Herpetological Monographs, v. 14, p. 1. Heitmuller, F.T., and Reece, B.D., 2003, Database of historically documented springs and spring flow measurements in Texas: U. S. Geological Survey Open-File Report 03, CD-ROM. Mace, R.E., Chowdhury, A.H., Anaya, R., and Way, Shao-Chih, 2000, Groundwater availability of the Trinity aquifer, Hill Country area, Texas—Numerical simulations through 2050: Texas Wate r Development Board Report 353, 117 p. 3


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