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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. Colorado 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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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 0.69 | 0.40 – 1.31 | 0.16 – 2.93 |
| Northeast | 1.49 | 1.23 – 1.90 | 0.43 – 3.54 |
| East Central | 0.95 | 0.38 – 1.52 | 0.14 – 3.39 |
| Southwest | 1.34 | 0.78 – 2.54 | 0.23 – 5.25 |
| San Luis Valley | 0.44 | 0.30 – 0.67 | 0.19 – 1.16 |
| Southeast | 2.10 | 0.70 – 4.39 | 0.40 – 5.26 |
| Statewide | 0.54 | 0.34 – 1.07 | 0.19 – 2.69 |
¶ Table 2. Sodium Adsorption Ratio, Adjusted (SARa) |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 2.1 | 0.3 – 15.1 | 0.1 – 52.6 |
| Northeast | 5.8 | 4.7 – 6.5 | 0.5 – 12.3 |
| East Central | 4.7 | 0.8 – 9.5 | 0.3 – 16.9 |
| Southwest | 2.2 | 0.6 – 9.6 | 0.2 – 152.3 |
| San Luis Valley | 1.2 | 0.8 – 2.1 | 0.4 – 5.1 |
| Southeast | 6.1 | 1.5 – 8.6 | 0.5 – 18.5 |
| Statewide | 1.5 | 0.8 – 4.6 | 0.3 – 14.6 |
¶ Table 3. Chloride, Cl mg/L |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 8 | 3 – 33 | 1 – 232 |
| Northeast | 91 | 58 – 110 | 7 – 214 |
| East Central | 63 | 9 – 175 | 2 – 525 |
| Southwest | 10 | 4 – 28 | 2 – 746 |
| San Luis Valley | 10 | 10 – 17 | 4 – 67 |
| Southeast | 58 | 16 – 150 | 7 – 180 |
| Statewide | 11 | 10 – 45 | 2 – 170 |
¶ Table 4. Sodium, Na mg/L |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 73 | 8 – 209 | 4 – 559 |
| Northeast | 130 | 105 – 150 | 11 – 370 |
| East Central | 87 | 15 – 180 | 5 – 392 |
| Southwest | 63 | 19 – 239 | 5 – 1210 |
| San Luis Valley | 22 | 14 – 41 | 8 – 84 |
| Southeast | 162 | 31 – 623 | 10 – 703 |
| Statewide | 28 | 14 – 84 | 7 – 360 |
¶ Table 5. Calcium, Ca mg/L |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 38 | 8 – 80 | 1 – 274 |
| Northeast | 150 | 111 – 200 | 33 – 360 |
| East Central | 58 | 36 – 82 | 9 – 305 |
| Southwest | 122 | 55 – 186 | 7 – 3565 |
| San Luis Valley | 50 | 34 – 77 | 21 – 150 |
| Southeast | 150 | 59 – 403 | 34 – 443 |
| Statewide | 56 | 34 – 100 | 9 – 250 |
¶ Table 6. Magnesium, Mg lb/ac-ft |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 7 | 1 – 21 | 1 – 131 |
| Northeast | 41 | 34 – 48 | 9 – 120 |
| East Central | 16 | 10 – 25 | 3 – 122 |
| Southwest | 32 | 12 – 74 | 2 – 171 |
| San Luis Valley | 9 | 6 – 14 | 3 – 26 |
| Southeast | 51 | 21 – 150 | 11 – 224 |
| Statewide | 11 | 6 – 22 | 2 – 83 |
¶ Table 7. Potassium, K as lb/ac-ft |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 2 | 1 – 5 | 1 – 19 |
| Northeast | 9 | 8 – 13 | 3 – 185 |
| East Central | 6 | 2 – 15 | 1 – 39 |
| Southwest | 3 | 2 – 5 | 1 – 35 |
| San Luis Valley | 6 | 4 – 9 | 2 – 13 |
| Southeast | 6 | 4 – 8 | 3 – 13 |
| Statewide | 6 | 4 – 9 | 1 – 16 |
¶ Table 8. Sulfate-sulfur, SO4-S as lb/ac-ft |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 10 | 3 – 58 | 1 – 330 |
| Northeast | 130 | 110 – 170 | 11 – 448 |
| East Central | 35 | 6 – 73 | 1 – 397 |
| Southwest | 110 | 30 – 220 | 3 – 534 |
| San Luis Valley | 21 | 11 – 42 | 4 – 100 |
| Southeast | 300 | 48 – 730 | 4 – 990 |
| Statewide | 25 | 11 – 68 | 2 – 304 |
¶ Table 9. Boron, B as lb/ac-ft |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 0.35 | 0.14 – 0.90 | 0.05 – 4.39 |
| Northeast | 0.68 | 0.49 – 0.87 | 0.11 – 3.65 |
| East Central | 0.33 | 0.12 – 0.97 | 0.05 – 1.90 |
| Southwest | 0.26 | 0.19 – 0.89 | 0.05 – 5.30 |
| San Luis Valley | 0.11 | 0.05 – 0.16 | 0.05 – 0.71 |
| Southeast | 0.57 | 0.33 – 2.18 | 0.16 – 4.00 |
| Statewide | 0.14 | 0.08 – 0.41 | 0.05 – 1.99 |
¶ Table 10. Nitrate-nitrogen, NO3-N mg/L |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 0.2 | 0.1 – 0.4 | 0.1 – 3.1 |
| Northeast | 4.2 | 1.7 – 10.0 | 0.2 – 67.3 |
| East Central | 1.8 | 0.3 – 5.7 | 0.1 – 11.9 |
| Southwest | 0.2 | 0.1 – 0.8 | 0.1 – 11.9 |
| San Luis Valley | 7.1 | 3.3 – 11.9 | 1.0 – 24.6 |
| Southeast | 3.3 | 0.9 – 10.0 | 0.1 – 10.0 |
| Statewide | 4.8 | 1.0 – 10.0 | 0.1 – 21.1 |
¶ Table 11. Bicarbonate, HCO3, lime equivalent as lb/ac-ft |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 600 | 355 – 1105 | 140 – 2310 |
| Northeast | 660 | 540 – 760 | 185 – 915 |
| East Central | 470 | 355 – 625 | 135 – 1455 |
| Southwest | 670 | 545 – 1015 | 275 – 9435 |
| San Luis Valley | 290 | 225 – 400 | 170 – 560 |
| Southeast | 600 | 470 – 980 | 335 – 1005 |
| Statewide | 380 | 270 – 560 | 170 – 1050 |
¶ Table 12. Iron, Fe mg/L |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 0.06 | 0.05 – 0.30 | 0.05 – 1.96 |
| Northeast | 0.12 | 0.05 – 0.40 | 0.05 – 3.68 |
| East Central | 0.05 | 0.05 – 0.14 | 0.05 – 1.90 |
| Southwest | 0.10 | 0.05 – 0.32 | 0.05 – 441.87 |
| San Luis Valley | 0.05 | 0.05 – 0.05 | 0.05 – 0.26 |
| Southeast | 0.05 | 0.05 – 0.77 | 0.05 – 4.30 |
| Statewide | 0.05 | 0.05 – 0.07 | 0.05 – 1.05 |
¶ Table 13. Manganese, Mn mg/L |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 8.1 | 7.7 – 8.4 | 7.3 – 9.0 |
| Northeast | 7.9 | 7.6 – 8.1 | 6.6 – 8.3 |
| East Central | 7.7 | 7.4 – 8.0 | 6.8 – 8.3 |
| Southwest | 7.9 | 7.7 – 8.1 | 7.0 – 8.4 |
| San Luis Valley | 7.9 | 7.7 – 8.0 | 7.5 – 8.3 |
| Southeast | 7.5 | 7.3 – 7.7 | 7.0 – 8.2 |
| Statewide | 7.9 | 7.7 – 8.1 | 7.3 – 8.4 |
¶ Table 14. Water pH |
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| Colorado Districts | Median | Typical range | Low - High |
| Northwest & Mountain | 8.1 | 7.7 – 8.4 | 7.3 – 9.0 |
| Northeast | 7.9 | 7.6 – 8.1 | 6.6 – 8.3 |
| East Central | 7.7 | 7.4 – 8.0 | 6.8 – 8.3 |
| Southwest | 7.9 | 7.7 – 8.1 | 7.0 – 8.4 |
| San Luis Valley | 7.9 | 7.7 – 8.0 | 7.5 – 8.3 |
| Southeast | 7.5 | 7.3 – 7.7 | 7.0 – 8.2 |
| Statewide | 7.9 | 7.7 – 8.1 | 7.3 – 8.4 |
¶ 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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| Northwest & Mtn. | 172 |
| Northeast | 144 |
| East Central | 133 |
| Southwest | 25 |
| San Luis Valley | 844 |
| Southeast | 59 |
| State-wide | 1382 |