Texas Private Well Water Risk: Arsenic & Nitrate

These figures are USGS statistical estimates for private (domestic) wells in Texas. They describe the area's modeled risk — not any single well.

This is a modeled probability for the area, not a measurement of your well. USGS statistical models estimate how many private wells in this area are likely to exceed the federal limit — they cannot tell you what is in your water. Two neighbors can have very different results. The only way to know your well is to test it.

Nitrate

2.5%

of the private-well population is modeled above the 10 mg/L nitrate limit

~40,800

people on wells estimated above the limit

~1,650,000

total residents on private wells statewide

Source: USGS machine-learning nitrate model, Ransom et al. (2022), domestic-well depth zone.

Arsenic

Across Texas, an estimated ~95,453 people rely on private wells with modeled arsenic above the 10 µg/L EPA limit. The highest modeled exposure is in Lubbock County (~11,642 people).

Counties with the highest modeled arsenic exposure

CountyEst. well residents over arsenic limit90% range
Lubbock County~11,64210,02313,432
Midland County~7,3066,3808,317
Harris County~6,3964,3819,270
Ector County~5,4494,6956,317
Montgomery County~3,7202,6125,286
Bee County~3,4122,4484,584
Jim Wells County~2,6511,9593,470
Randall County~2,6492,1793,227
Fort Bend County~2,6431,8193,807
Starr County~2,4781,8583,177
El Paso County~2,3532,0112,729
Gaines County~2,2811,9542,632
Brazoria County~1,8071,2292,657
San Patricio County~1,6731,1692,291
Potter County~1,6291,3241,999
Victoria County~1,2638771,794
Nueces County~1,2028681,620
Howard County~1,0408301,284
Andrews County~1,0328741,209
Hockley County~9848441,139
Dawson County~9328061,067
Wharton County~689478986
Live Oak County~686471944
Scurry County~648512813
Galveston County~635423942
Duval County~630466819
Hale County~625529733
Deaf Smith County~618519733
Yoakum County~605521697
Goliad County~595413837
Lavaca County~567380837
Parmer County~558476652
Wise County~553441705
Tom Green County~547450674
Liberty County~543365803
Parker County~541431681
Waller County~517385687
Martin County~513428607
Travis County~505363701
DeWitt County~503341728
Terry County~493426564
Austin County~486336702
Bailey County~432367503
Colorado County~427293615
Bexar County~406318524
Burnet County~395253688
Hidalgo County~387301487
Maverick County~374308455
Walker County~341226514
Hays County~339258448
Hartley County~335290384
Orange County~327214498
Castro County~325276383
Leon County~317172550
Gray County~308255370
Matagorda County~305209433
Lamb County~289248335
Calhoun County~286197410
Washington County~276177431
Swisher County~265222316
Denton County~251191331
Hutchinson County~244201294
Jones County~241196295
Brooks County~240185304
Madison County~228172306
Lynn County~220188256
Dallam County~208180238
Erath County~204161258
Jasper County~204136308
Floyd County~203168244
Refugio County~202145275
Jackson County~199136290
Cameron County~191157231
Van Zandt County~188150237
Comanche County~187151231
Ochiltree County~184154220
Chambers County~178119269
San Jacinto County~175121250
Val Verde County~169122232
Tarrant County~164117229
Fayette County~163107247
Hardin County~161110238
Garza County~160115218
Montague County~157125195
Williamson County~155122203
Llano County~14386220
Pecos County~140109181
Tyler County~14094211
Gillespie County~13696199
Newton County~13489200
Bowie County~129100167
Hood County~12899170
Aransas County~12687177
Glasscock County~124104148
Henderson County~12396160
Grimes County~12285175
Jefferson County~12180182
Wheeler County~11996146
Eastland County~11594141
Atascosa County~11391142
Bandera County~11385168
Blanco County~10574150
Nacogdoches County~10461177
Anderson County~10378136
Burleson County~10381131
Hemphill County~10283126
Polk County~10168151
Kendall County~10077129

146 additional Texas counties have lower modeled arsenic exposure (fewer than 100 estimated well residents over the limit).

Source: USGS domestic-well arsenic model, Lombard et al. (2021); county population product (2017).

Treating arsenic in Texas

Arsenic is not removed by carbon pitchers or faucet filters. Reverse osmosis is the treatment that brings it below the federal limit at your tap.

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