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¶ Introduction
Contains survey statistics of laboratory results from water samples submitted to ServiTech Laboratories during 2011 to 2022, inclusive, for analysis of irrigation water suitability. The results are grouped by National Agricultural Statistics Service (USDA-NASS) reporting districts.
¶ Figure 1. Texas Plains USDA-NASS Districts
Interpretation of survey results:
- Median = 50th percentile
- Typical range = 25th and 75th percentiles
- Low - High = 5th and 95th percentiles
¶ Table 1. Electrical Conductivity, EC mmho/cm |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 0.66 | 0.54 – 0.99 | 0.40 – 3.09 |
| Southern High Plains | 1.56 | 1.09 – 2.40 | 0.63 – 5.29 |
| Northern Low Plains | 2.58 | 0.85 – 3.63 | 0.49 – 8.11 |
| Southern Low Plains | 1.68 | 1.19 – 2.91 | 0.60 – 6.01 |
| Trans-Pecos | 3.50 | 2.96 – 3.67 | ---- |
| Edwards Plateau | 2.26 | 1.52 – 2.87 | 0.55 – 5.43 |
| Texas Plains Region | 1.13 | 0.64 – 2.02 | 0.46 – 4.70 |
¶ Table 2. Sodium Adsorption Ratio, Adjusted (SARa) |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 2.3 | 1.4 – 4.9 | 0.6 – 24.6 |
| Southern High Plains | 4.5 | 2.9 – 7.4 | 1.7 – 16.9 |
| Northern Low Plains | 3.3 | 1.6 – 6.8 | 0.5 – 23.8 |
| Southern Low Plains | 6.5 | 3.1 – 10.1 | 0.6 – 19.8 |
| Trans-Pecos | 9.7 | 7.7 – 18.8 | ---- |
| Edwards Plateau | 6.8 | 4.7 – 9.8 | 0.8 – 17.0 |
| Texas Plains Region | 3.6 | 2.0 – 6.9 | 0.8 – 20.1 |
¶ Table 3. Chloride, Cl mg/L |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 30 | 15 – 73 | 8 – 480 |
| Southern High Plains | 200 | 100 – 370 | 27 – 1080 |
| Northern Low Plains | 130 | 34 – 453 | 10 – 1700 |
| Southern Low Plains | 175 | 93 – 450 | 24 – 957 |
| Trans-Pecos | 705 | 358 – 790 | ---- |
| Edwards Plateau | 240 | 77 – 490 | 26 – 1460 |
| Texas Plains Region | 98 | 27 – 270 | 10 – 840 |
¶ Table 4. Sodium, Na mg/L |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 45 | 30 – 100 | 17 – 420 |
| Southern High Plains | 110 | 66 – 200 | 33 – 558 |
| Northern Low Plains | 99 | 42 – 343 | 16 – 1060 |
| Southern Low Plains | 150 | 84 – 243 | 34 – 749 |
| Trans-Pecos | 461 | 285 – 513 | ---- |
| Edwards Plateau | 200 | 120 – 273 | 16 – 564 |
| Texas Plains Region | 79 | 40 – 178 | 21 – 530 |
¶ Table 5. Calcium, Ca mg/L |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 45 | 37 – 60 | 9 – 200 |
| Southern High Plains | 88 | 61 – 130 | 39 – 310 |
| Northern Low Plains | 369 | 81 – 600 | 51 – 757 |
| Southern Low Plains | 110 | 80 – 232 | 27 – 590 |
| Trans-Pecos | 227 | 209 – 274 | ---- |
| Edwards Plateau | 190 | 120 – 280 | 60 – 494 |
| Texas Plains Region | 64 | 43 – 114 | 24 – 391 |
¶ Table 6. Magnesium, Mg lb/ac-ft |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 84 | 68 – 112 | 3 – 250 |
| Southern High Plains | 223 | 122 – 337 | 57 – 598 |
| Northern Low Plains | 269 | 82 – 419 | 32 – 890 |
| Southern Low Plains | 147 | 95 – 272 | 33 – 517 |
| Trans-Pecos | 245 | 169 – 279 | ---- |
| Edwards Plateau | 207 | 136 – 272 | 57 – 428 |
| Texas Plains Region | 117 | 79 – 250 | 22 – 509 |
¶ Table 7. Potassium, K as lb/ac-ft |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 16 | 11 – 22 | 5 – 38 |
| Southern High Plains | 33 | 22 – 49 | 8 – 79 |
| Northern Low Plains | 12 | 8 – 17 | 5 – 37 |
| Southern Low Plains | 14 | 10 – 16 | 5 – 69 |
| Trans-Pecos | 44 | 21 – 49 | ---- |
| Edwards Plateau | 16 | 11 – 27 | 5 – 37 |
| Texas Plains Region | 19 | 14 – 33 | 5 – 68 |
¶ Table 8. Sulfate-sulfur, SO4-S as lb/ac-ft |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 44 | 27 – 90 | 11 – 680 |
| Southern High Plains | 234 | 122 – 435 | 27 – 1197 |
| Northern Low Plains | 1102 | 65 – 1666 | 17 – 2216 |
| Southern Low Plains | 197 | 106 – 775 | 33 – 1791 |
| Trans-Pecos | 666 | 510 – 721 | ---- |
| Edwards Plateau | 408 | 215 – 816 | 29 – 1409 |
| Texas Plains Region | 117 | 35 – 326 | 17 – 1306 |
¶ Table 9. Boron, B as lb/ac-ft |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 0.49 | 0.35 – 0.71 | 0.16 – 1.93 |
| Southern High Plains | 1.09 | 0.68 – 1.69 | 0.38 – 2.99 |
| Northern Low Plains | 0.87 | 0.46 – 1.67 | 0.14 – 3.72 |
| Southern Low Plains | 1.16 | 0.75 – 1.67 | 0.33 – 3.77 |
| Trans-Pecos | 1.06 | 0.78 – 1.13 | ---- |
| Edwards Plateau | 1.63 | 0.73 – 2.99 | 0.22 – 5.44 |
| Texas Plains Region | 0.73 | 0.44 – 1.33 | 0.24 – 2.99 |
¶ Table 10. Nitrate-nitrogen, NO3-N mg/L |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 1.9 | 1.2 – 2.9 | 0.2 – 10.6 |
| Southern High Plains | 6.6 | 3.3 – 11.9 | 1.0 – 26.0 |
| Northern Low Plains | 4.5 | 1.6 – 10.0 | 0.3 – 22.9 |
| Southern Low Plains | 9.2 | 1.2 – 20.1 | 0.1 – 31.3 |
| Trans-Pecos | 5.7 | 2.1 – 10.0 | ---- |
| Edwards Plateau | 10.0 | 5.0 – 21.7 | 1.0 – 41.7 |
| Texas Plains Region | 3.2 | 1.7 – 8.9 | 0.4 – 24.0 |
¶ Table 11. Bicarbonate, HCO3, lime equivalent as lb/ac-ft |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 600 | 515 – 735 | 245 – 1050 |
| Southern High Plains | 600 | 515 – 690 | 425 – 850 |
| Northern Low Plains | 515 | 425 – 600 | 245 – 870 |
| Southern Low Plains | 735 | 600 – 850 | 290 – 1110 |
| Trans-Pecos | 600 | 505 – 680 | ---- |
| Edwards Plateau | 515 | 470 – 600 | 375 – 760 |
| Texas Plains Region | 600 | 515 – 715 | 335 – 940 |
¶ Table 12. Iron, Fe mg/L |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 0.05 | 0.05 – 0.16 | 0.05 – 2.06 |
| Southern High Plains | 0.05 | 0.05 – 0.08 | 0.05 – 0.96 |
| Northern Low Plains | 0.10 | 0.05 – 0.37 | 0.05 – 2.93 |
| Southern Low Plains | 0.05 | 0.05 – 0.17 | 0.05 – 1.76 |
| Trans-Pecos | 0.06 | 0.05 – 0.25 | ---- |
| Edwards Plateau | 0.05 | 0.05 – 0.07 | 0.05 – 0.82 |
| Texas Plains Region | 0.05 | 0.05 – 0.11 | 0.05 – 1.70 |
¶ Table 13. Manganese, Mn mg/L |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 0.005 | 0.005 – 0.010 | 0.005 – 0.180 |
| Southern High Plains | 0.005 | 0.005 – 0.005 | 0.005 – 0.120 |
| Northern Low Plains | 0.005 | 0.005 – 0.041 | 0.005 – 0.242 |
| Southern Low Plains | 0.005 | 0.005 – 0.020 | 0.005 – 0.107 |
| Trans-Pecos | 0.005 | 0.005 – 0.009 | ---- |
| Edwards Plateau | 0.005 | 0.005 – 0.005 | 0.005 – 0.062 |
| Texas Plains Region | 0.005 | 0.005 – 0.008 | 0.005 – 0.148 |
¶ Table 14. Water pH |
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| Texas Plains Districts | Median | Typical range | Low - High |
| Northern High Plains | 8.1 | 7.9 – 8.3 | 7.6 – 8.6 |
| Southern High Plains | 7.9 | 7.8 – 8.1 | 7.5 – 8.3 |
| Northern Low Plains | 7.9 | 7.6 – 8.0 | 7.3 – 8.2 |
| Southern Low Plains | 7.6 | 7.4 – 7.9 | 7.1 – 8.3 |
| Trans-Pecos | 7.8 | 7.7 – 8.2 | ---- |
| Edwards Plateau | 7.7 | 7.5 – 8.0 | 7.1 – 8.3 |
| Texas Plains Region | 8.0 | 7.8 – 8.2 | 7.5 – 8.5 |
¶ Table 15. Conversion Factors |
| 1 mg/L ≈ 1 ppm |
| 1 mg/L = 1,000 µg/L |
| 1 mmho/cm = 1 dS/m |
| 1 mmho/cm = 1,000 µmho/cm lb/ac-in = mg/L x 0.2267 lb/ac-ft = mg/L x 2.7204 |
| lime equivalent, lb/ac-ft = HCO3 mg/L x 2.2304 |
| 1 acre-inch = 27,154 gallons |
| 1 acre-foot = 325,848 gallons |
¶ Table 16. Sample Count |
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| Northern High Plains | 1619 |
| Southern High Plains | 1503 |
| Northern Low Plains | 90 |
| Southern Low Plains | 142 |
| Trans-Pecos | 14 |
| Edwards Plateau | 107 |
| Texas Plains Region | 3475 |