Texas Underground 2026: which formation wells draw from, county by county

One line per county

• Andrews County: the median well is 114 ft deep; most (71%) draw from the Ogallala Aquifer, with a median of 110 ft in that layer.
• Armstrong County: the median well is 270 ft deep and no layer dominates; the largest share, 50%, draws from the Ogallala Aquifer.
• Austin County: the median well is 207 ft deep; most (59%) draw from the Evangeline Aquifer, with a median of 220 ft in that layer. The split between the Chicot and the Evangeline is approximate.
• Bailey County: the median well is 238 ft deep and nearly all (88%) draw from the Ogallala Aquifer.
• Bandera County: the median well is 510 ft deep; most (75%) draw from the Middle Trinity, with a median of 500 ft in that layer.
• Bastrop County: the median well is 328 ft deep and all draw from younger formations above the Woodbine. The model covers only 33% of its 874 wells.
• Bell County: the median well is 560 ft deep and no layer dominates; the largest share, 50%, draws from the lower Trinity (Twin Mountains and Travis Peak).
• Bexar County: the median well is 500 ft deep and nearly all (89%) draw from the Middle Trinity. The model covers only 49% of its 810 wells.
• Blanco County: the median well is 410 ft deep; most (70%) draw from the Middle Trinity, with a median of 443 ft in that layer. The model covers only 66% of its 1,172 wells.
• Borden County: the median well is 104 ft deep and 75% end at or just below the base of the Ogallala, in the top of the Dockum. Most of these reports do not say where the water enters, so the formation is a rough guide.
• Bosque County: the median well is 480 ft deep and no layer dominates; the largest share, 53%, draws from the lower Trinity (Twin Mountains and Travis Peak).
• Bowie County: the median well is 80 ft deep and all draw from younger formations above the Woodbine.
• Brazoria County: the median well is 363 ft deep and all draw from the Chicot Aquifer.
• Briscoe County: the median well is 200 ft deep and 55% end at or just below the base of the Ogallala, in the top of the Dockum. Most of these reports do not say where the water enters, so the formation is a rough guide. The model covers only 57% of its 51 wells.
• Brown County: the median well is 198 ft deep and most (76%) draw from the Trinity, which the state maps there as one undivided unit (Antlers).
• Burnet County: the median well is 350 ft deep; most (72%) draw from the lower Trinity (Twin Mountains and Travis Peak), with a median of 380 ft in that layer.
• Calhoun County: the median well is 225 ft deep and all draw from the Chicot Aquifer. The model covers only 17% of its 315 wells.
• Callahan County: the median well is 70 ft deep and nearly all (99%) draw from the Trinity, which the state maps there as one undivided unit (Antlers).
• Carson County: the median well is 400 ft deep; most (75%) draw from the Ogallala Aquifer, with a median of 455 ft in that layer.
• Castro County: the median well is 378 ft deep and nearly all (95%) draw from the Ogallala Aquifer.
• Chambers County: the median well is 200 ft deep and all draw from the Chicot Aquifer.
• Cochran County: the median well is 205 ft deep; most (58%) draw from the Edwards-Trinity (High Plains) Aquifer, with a median of 210 ft in that layer. Most of these reports do not say where the water enters, so the formation is a rough guide.
• Collin County: the median well is 1,020 ft deep and nearly all (86%) draw from the Woodbine Aquifer.
• Colorado County: the median well is 165 ft deep; most (65%) draw from the Evangeline Aquifer, with a median of 185 ft in that layer. The split between the Chicot and the Evangeline is approximate.
• Comal County: the median well is 484 ft deep; most (62%) draw from the Middle Trinity, with a median of 480 ft in that layer.
• Comanche County: the median well is 158 ft deep and nearly all (96%) draw from the Trinity, which the state maps there as one undivided unit (Antlers).
• Cooke County: the median well is 500 ft deep and nearly all (91%) draw from the Trinity, which the state maps there as one undivided unit (Antlers); by depth, roughly 62% in its upper part and 30% in its lower part, an approximate split.
• Coryell County: the median well is 480 ft deep and nearly all (88%) draw from the lower Trinity (Twin Mountains and Travis Peak).
• Crane County: the median well is 240 ft deep and 87% end at or just below the base of the Ogallala, in the top of the Dockum.
• Crockett County: the median well is 410 ft deep and all draw from the Edwards-Trinity (Plateau) Aquifer. The model covers only 49% of its 33 wells.
• Crosby County: the median well is 344 ft deep and nearly all (86%) draw from the Ogallala Aquifer.
• Dallam County: the median well is 515 ft deep and 52% end at or just below the base of the Ogallala, in the top of the Dockum.
• Dallas County: the median well is 55 ft deep; most (82%) draw from younger formations above the Woodbine, with a median of 50 ft in that layer.
• Dawson County: the median well is 168 ft deep; most (77%) draw from the Ogallala Aquifer, with a median of 160 ft in that layer.
• Deaf Smith County: the median well is 330 ft deep and nearly all (91%) draw from the Ogallala Aquifer.
• Denton County: the median well is 440 ft deep and nearly all (86%) draw from the upper Trinity (Paluxy and Glen Rose).
• Dickens County: the median well is 117 ft deep and 49% end near or below the base of the Dockum, or of the Ogallala where there is no Dockum. Most of these reports do not say where the water enters, so the formation is a rough guide. The model covers only 44% of its 107 wells.
• Donley County: the median well is 160 ft deep; most (61%) draw from the Ogallala Aquifer, with a median of 150 ft in that layer.
• Eastland County: the median well is 115 ft deep and nearly all (91%) draw from the Trinity, which the state maps there as one undivided unit (Antlers). The model covers only 64% of its 207 wells.
• Ector County: the median well is 140 ft deep and 57% end at or just below the base of the Ogallala, in the top of the Dockum.
• Ellis County: the median well is 420 ft deep; most (62%) draw from the Woodbine Aquifer, with a median of 520 ft in that layer.
• Erath County: the median well is 375 ft deep and nearly all (97%) draw from the Trinity, which the state maps there as one undivided unit (Antlers); by depth, roughly 9% in its upper part and 88% in its lower part, an approximate split.
• Falls County: the median well is 65 ft deep and all draw from younger formations above the Woodbine.
• Fannin County: the median well is 62 ft deep; most (57%) draw from younger formations above the Woodbine, with a median of 63 ft in that layer.
• Fayette County: the median well is 265 ft deep and nearly all (91%) draw from the Jasper and Catahoula aquifers, with the Burkeville.
• Floyd County: the median well is 363 ft deep; most (69%) draw from the Ogallala Aquifer, with a median of 363 ft in that layer.
• Fort Bend County: the median well is 260 ft deep and all draw from the Chicot Aquifer.
• Gaines County: the median well is 200 ft deep; most (56%) draw from the Ogallala Aquifer, with a median of 184 ft in that layer.
• Galveston County: the median well is 424 ft deep and all draw from the Chicot Aquifer.
• Garza County: the median well is 106 ft deep and 73% end at or just below the base of the Ogallala, in the top of the Dockum.
• Gillespie County: the median well is 240 ft deep and no layer dominates; the largest share, 51%, draws from the Middle Trinity. The model covers only 68% of its 1,959 wells.
• Glasscock County: the median well is 265 ft deep; most (81%) draw from the Edwards-Trinity (Plateau) Aquifer, with a median of 288 ft in that layer.
• Gonzales County: the median well is 360 ft deep; most (67%) draw from the Jasper and Catahoula aquifers, with the Burkeville, with a median of 254 ft in that layer. The model covers only 12% of its 518 wells.
• Gray County: the median well is 450 ft deep; most (70%) draw from the Ogallala Aquifer, with a median of 480 ft in that layer.
• Grayson County: the median well is 340 ft deep and no layer dominates; the largest share, 48%, draws from the Woodbine Aquifer. The state maps the Trinity there as undivided (Antlers), so the split is approximate.
• Grimes County: the median well is 295 ft deep; most (57%) draw from the Jasper and Catahoula aquifers, with the Burkeville, with a median of 300 ft in that layer.
• Hale County: the median well is 304 ft deep and no layer dominates; the largest share, 50%, draws from the Ogallala Aquifer.
• Hamilton County: the median well is 475 ft deep and nearly all (92%) draw from the Trinity, which the state maps there as one undivided unit (Antlers); by depth, roughly 6% in its upper part and 86% in its lower part, an approximate split.
• Hansford County: the median well is 485 ft deep; most (74%) draw from the Ogallala Aquifer, with a median of 480 ft in that layer.
• Hardin County: the median well is 255 ft deep and all draw from the Chicot Aquifer.
• Harris County: the median well is 260 ft deep and all draw from the Chicot Aquifer. In this county the state records many of the deeper wells in the Evangeline, so read the Chicot as the most likely layer, not a certain one.
• Hartley County: the median well is 554 ft deep and no layer dominates; the largest share, 52%, draws from the Ogallala Aquifer.
• Hays County: the median well is 510 ft deep; most (57%) draw from the Middle Trinity, with a median of 500 ft in that layer.
• Hemphill County: the median well is 290 ft deep; most (67%) draw from the Ogallala Aquifer, with a median of 260 ft in that layer.
• Henderson County: the median well is 460 ft deep and all draw from younger formations above the Woodbine. The model covers only 2% of its 603 wells.
• Hill County: the median well is 360 ft deep and no layer dominates; the largest share, 48%, draws from the Woodbine Aquifer.
• Hockley County: the median well is 155 ft deep and nearly all (87%) draw from the Ogallala Aquifer.
• Hood County: the median well is 360 ft deep and nearly all (94%) draw from the Trinity, which the state maps there as one undivided unit (Antlers); by depth, roughly 12% in its upper part and 82% in its lower part, an approximate split.
• Howard County: the median well is 110 ft deep and 44% end at or just below the base of the Ogallala, in the top of the Dockum.
• Hunt County: the median well is 216 ft deep and all draw from younger formations above the Woodbine. The model covers only 66% of its 244 wells.
• Hutchinson County: the median well is 400 ft deep and 60% end near or below the base of the Dockum, or of the Ogallala where there is no Dockum.
• Irion County: the median well is 160 ft deep and nearly all (92%) draw from the Edwards-Trinity (Plateau) Aquifer. The model covers only 41% of its 91 wells.
• Jack County: the median well is 220 ft deep and 55% end near or below the base of the Trinity. The state maps the Trinity there as undivided (Antlers), so the split is approximate. The model covers only 26% of its 760 wells.
• Jackson County: the median well is 160 ft deep and all draw from the Chicot Aquifer.
• Jasper County: the median well is 185 ft deep and no layer dominates; the largest share, 52%, draws from the Chicot Aquifer. The split between the Chicot and the Evangeline is approximate.
• Jefferson County: the median well is 210 ft deep and all draw from the Chicot Aquifer.
• Johnson County: the median well is 400 ft deep and no layer dominates; the largest share, 51%, draws from the upper Trinity (Paluxy and Glen Rose).
• Kaufman County: the median well is 100 ft deep and all draw from younger formations above the Woodbine.
• Kendall County: the median well is 413 ft deep; most (75%) draw from the Middle Trinity, with a median of 380 ft in that layer.
• Kerr County: the median well is 540 ft deep; most (58%) draw from the Middle Trinity, with a median of 600 ft in that layer.
• Lamar County: the median well is 100 ft deep and nearly all (91%) draw from younger formations above the Woodbine.
• Lamb County: the median well is 223 ft deep; most (67%) draw from the Ogallala Aquifer, with a median of 238 ft in that layer.
• Lampasas County: the median well is 346 ft deep; most (68%) draw from the lower Trinity (Twin Mountains and Travis Peak), with a median of 310 ft in that layer.
• Lavaca County: the median well is 185 ft deep; most (55%) draw from the Jasper and Catahoula aquifers, with the Burkeville, with a median of 200 ft in that layer. The split between the Chicot and the Evangeline is approximate.
• Lee County: the median well is 458 ft deep and all draw from younger formations above the Woodbine. The model covers only 39% of its 284 wells.
• Liberty County: the median well is 250 ft deep and all draw from the Chicot Aquifer. In this county the state records many of the deeper wells in the Evangeline, so read the Chicot as the most likely layer, not a certain one.
• Limestone County: the median well is 360 ft deep and all draw from younger formations above the Woodbine. The model covers only 7% of its 375 wells.
• Lipscomb County: the median well is 305 ft deep; most (74%) draw from the Ogallala Aquifer, with a median of 295 ft in that layer. Most of these reports do not say where the water enters, so the formation is a rough guide.
• Lubbock County: the median well is 172 ft deep; most (72%) draw from the Ogallala Aquifer, with a median of 162 ft in that layer.
• Lynn County: the median well is 141 ft deep; most (70%) draw from the Ogallala Aquifer, with a median of 140 ft in that layer.
• Martin County: the median well is 86 ft deep; most (58%) draw from the Ogallala Aquifer, with a median of 80 ft in that layer.
• Matagorda County: the median well is 410 ft deep and all draw from the Chicot Aquifer.
• McLennan County: the median well is 1,100 ft deep and no layer dominates; the largest share, 50%, draws from the lower Trinity (Twin Mountains and Travis Peak).
• Medina County: the median well is 535 ft deep; most (77%) draw from the Middle Trinity, with a median of 730 ft in that layer. The model covers only 18% of its 800 wells.
• Midland County: the median well is 100 ft deep; most (59%) draw from the Ogallala Aquifer, with a median of 96 ft in that layer.
• Milam County: the median well is 422 ft deep and all draw from younger formations above the Woodbine. The model covers only 64% of its 328 wells.
• Mills County: the median well is 300 ft deep and nearly all (88%) draw from the lower Trinity (Twin Mountains and Travis Peak).
• Mitchell County: the median well is 160 ft deep and 87% end at or just below the base of the Ogallala, in the top of the Dockum.
• Montague County: the median well is 220 ft deep and most (73%) draw from the Trinity, which the state maps there as one undivided unit (Antlers); by depth, roughly 13% in its upper part and 60% in its lower part, an approximate split. The model covers only 63% of its 1,162 wells.
• Montgomery County: the median well is 215 ft deep; most (61%) draw from the Chicot Aquifer, with a median of 200 ft in that layer. The split between the Chicot and the Evangeline is approximate.
• Moore County: the median well is 475 ft deep; most (76%) draw from the Ogallala Aquifer, with a median of 431 ft in that layer.
• Navarro County: the median well is 107 ft deep and nearly all (91%) draw from younger formations above the Woodbine. The model covers only 47% of its 47 wells.
• Newton County: the median well is 150 ft deep and no layer dominates; the largest share, 52%, draws from the Chicot Aquifer. The split between the Chicot and the Evangeline is approximate.
• Nolan County: the median well is 200 ft deep and 65% end at or just below the base of the Ogallala, in the top of the Dockum. The model covers only 24% of its 95 wells.
• Ochiltree County: the median well is 420 ft deep and nearly all (98%) draw from the Ogallala Aquifer.
• Oldham County: the median well is 322 ft deep; most (76%) draw from the Ogallala Aquifer, with a median of 323 ft in that layer.
• Orange County: the median well is 405 ft deep and all draw from the Chicot Aquifer.
• Palo Pinto County: the median well is 200 ft deep; most (55%) draw from the lower Trinity (Twin Mountains and Travis Peak), with a median of 120 ft in that layer. The model covers only 7% of its 847 wells.
• Parker County: the median well is 240 ft deep and nearly all (90%) draw from the Trinity, which the state maps there as one undivided unit (Antlers); by depth, roughly 54% in its upper part and 36% in its lower part, an approximate split.
• Parmer County: the median well is 406 ft deep and nearly all (96%) draw from the Ogallala Aquifer.
• Pecos County: the median well is 261 ft deep and no layer dominates; the largest share, 39%, draws from the Edwards-Trinity (Plateau) Aquifer. The model covers only 14% of its 92 wells.
• Polk County: the median well is 205 ft deep; most (76%) draw from the Jasper and Catahoula aquifers, with the Burkeville, with a median of 210 ft in that layer. The split between the Chicot and the Evangeline is approximate.
• Potter County: the median well is 297 ft deep; most (60%) draw from the Ogallala Aquifer, with a median of 300 ft in that layer.
• Randall County: the median well is 344 ft deep and 62% end at or just below the base of the Ogallala, in the top of the Dockum.
• Reagan County: the median well is 380 ft deep; most (77%) draw from the Edwards-Trinity (Plateau) Aquifer, with a median of 370 ft in that layer. Most of these reports do not say where the water enters, so the formation is a rough guide.
• Red River County: the median well is 90 ft deep and nearly all (92%) draw from younger formations above the Woodbine.
• Reeves County: the median well is 260 ft deep and nearly all (93%) draw from the Pecos Valley Aquifer. The model covers only 50% of its 90 wells.
• Roberts County: the median well is 470 ft deep; most (81%) draw from the Ogallala Aquifer, with a median of 480 ft in that layer. Most of these reports do not say where the water enters, so the formation is a rough guide.
• Robertson County: the median well is 438 ft deep and all draw from younger formations above the Woodbine. The model covers only 4% of its 372 wells.
• San Jacinto County: the median well is 209 ft deep and no layer dominates; the largest share, 43%, draws from the Chicot Aquifer. The split between the Chicot and the Evangeline is approximate.
• Scurry County: the median well is 240 ft deep and 80% end at or just below the base of the Ogallala, in the top of the Dockum.
• Sherman County: the median well is 450 ft deep; most (75%) draw from the Ogallala Aquifer, with a median of 444 ft in that layer.
• Somervell County: the median well is 460 ft deep and nearly all (98%) draw from the Trinity, which the state maps there as one undivided unit (Antlers); by depth, roughly 18% in its upper part and 80% in its lower part, an approximate split.
• Sterling County: the median well is 120 ft deep and 75% end at or just below the base of the Ogallala, in the top of the Dockum. Most of these reports do not say where the water enters, so the formation is a rough guide.
• Swisher County: the median well is 204 ft deep and nearly all (93%) draw from the Ogallala Aquifer.
• Tarrant County: the median well is 340 ft deep and nearly all (87%) draw from the upper Trinity (Paluxy and Glen Rose).
• Terry County: the median well is 145 ft deep; most (64%) draw from the Ogallala Aquifer, with a median of 140 ft in that layer.
• Travis County: the median well is 445 ft deep and no layer dominates; the largest share, 46%, draws from the Lower Trinity.
• Trinity County: the median well is 274 ft deep; most (63%) draw from the Jasper and Catahoula aquifers, with the Burkeville, with a median of 185 ft in that layer. The model covers only 20% of its 136 wells.
• Tyler County: the median well is 160 ft deep and no layer dominates; the largest share, 38%, draws from the Evangeline Aquifer. The split between the Chicot and the Evangeline is approximate.
• Upton County: the median well is 300 ft deep; most (66%) draw from the Edwards-Trinity (Plateau) Aquifer, with a median of 315 ft in that layer.
• Walker County: the median well is 260 ft deep and nearly all (88%) draw from the Jasper and Catahoula aquifers, with the Burkeville.
• Waller County: the median well is 240 ft deep; most (57%) draw from the Chicot Aquifer, with a median of 226 ft in that layer. The split between the Chicot and the Evangeline is approximate.
• Ward County: the median well is 135 ft deep and 74% end at or just below the base of the Ogallala, in the top of the Dockum. Most of these reports do not say where the water enters, so the formation is a rough guide.
• Washington County: the median well is 236 ft deep; most (66%) draw from the Jasper and Catahoula aquifers, with the Burkeville, with a median of 245 ft in that layer.
• Wharton County: the median well is 200 ft deep and all draw from the Chicot Aquifer.
• Wheeler County: the median well is 160 ft deep; most (65%) draw from the Ogallala Aquifer, with a median of 152 ft in that layer. The model covers only 53% of its 70 wells.
• Williamson County: the median well is 553 ft deep; most (60%) draw from the lower Trinity (Twin Mountains and Travis Peak), with a median of 550 ft in that layer.
• Winkler County: the median well is 200 ft deep; most (60%) draw from the Pecos Valley Aquifer, with a median of 179 ft in that layer.
• Wise County: the median well is 220 ft deep and nearly all (90%) draw from the Trinity, which the state maps there as one undivided unit (Antlers); by depth, roughly 36% in its upper part and 54% in its lower part, an approximate split.
• Yoakum County: the median well is 180 ft deep; most (61%) draw from the Ogallala Aquifer, with a median of 171 ft in that layer.