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Water Test Interpretation

Ca ++ Na +. Cl - SO 4 =. NO 3 -. Water Test Interpretation. Mike Kizer OSU Extension Irrigation Specialist. HCO 3 - CO 3 =. K + Mg ++. Measures of Water Quality. Electrical Conductivity (EC) Total Dissolved Solids (TDS) Individual mineral concentrations

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Water Test Interpretation

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  1. Ca++ Na+ Cl- SO4= NO3- Water Test Interpretation Mike Kizer OSU Extension Irrigation Specialist HCO3- CO3= K+ Mg++

  2. Measures of Water Quality • Electrical Conductivity (EC) • Total Dissolved Solids (TDS) • Individual mineral concentrations • Calculated salinity products (Hardness, SAR, Na%, etc.)

  3. Electrical Conductivity(EC) • Pure water will not conduct electric current • The more minerals dissolved in water, the more current it conducts • EC is a good estimator of total mineral content (TSS)

  4. Units - EC • mmho/cm = (millimho per centimeter) • mmho/cm = (micromho per centimeter) • dS/m = (deciSiemen/meter) • mS/cm = (milliSiemen per centimeter) • 1 mmho/cm = 1 dS/m = 1mS/cm • 1 mmho/cm = 1000 mmho/cm

  5. Total Dissolved Solids(TDS) • TDS is calculated by adding all measured mineral concentrations as determined by chemical analyses • TSS is an estimate of TDS based on EC • EC (mmho/cm) x 640  TSS mg/l • This equivalence is approximate and depends on the ions causing the salinity (High levels of CO3 and HCO3 affect the ratio)

  6. Units - TDS / TSS mg/l = milligrams/liter ppm = parts per million mg/l = micrograms/liter ppb = parts per billion • 1 mg/l = 1 ppm in water chemistry (1 liter of water weighs 1,000,000 mg) • 1 mg/l = 1000 mg /l • 1 mg /l = 1 ppb in water chemistry

  7. SWFAL Water Quality Tests The OSU Soil Water & Forage Analytical Laboratory (Room 048 Ag. Hall) offers three water tests: • Livestock Water Test • Household Water Test • Irrigation Water Test (All tests require a 1 pint water sample)

  8. Livestock Water Test • Price: $6.00 • Analytes: • pH • Total Soluble Salts (TSS) • Electrical Conductivity (EC) • Nitrate-Nitrogen (NO3-N)

  9. Livestock Water QualityTotal Soluble Salts -TSS TSS (ppm)Interpretation • < 1000: Excellent • 1000 – 3000: Satisfactory for all animals • 3000 – 5000: Unsatisfactory for poultry • 5000 – 7000: Can be used except for pregnant, lactating or immature livestock • 10,000+: Unsatisfactory for all animals

  10. Livestock Water QualityNitrate- Nitrogen –NO3-N NO3-N (ppm)Interpretation • < 100: Satisfactory for all animals • 100 – 290: Use with care when given in combination with high nitrate feeds (especially forages in times of drought) • 290 +: Unsatisfactory for all animals

  11. Livestock Water Quality • Sulfate (SO4): If most of the soluble salts are sulfates the acceptable TSS levels are reduced • pH: The preferred range is 6.0-8.5. Animals can tolerate water outside this range.

  12. Household Water Test • Price: $10.00 • Analytes: • Sodium (Na) Chloride (Cl) • Calcium (Ca) Sulfate (SO4) • Magnesium (Mg) Nitrate-Nitrogen (NO3-N) • Potassium (K) Electrical Conductivity (EC) • pH Total soluble Salts (TSS) • Hardness

  13. Household Water TestNitrate-Nitrogen – (NO3-N) • NO3-N is the only analyte on the test with a Federal SDWA Standard • The NO3-N standard is 10 mg/l • Newborn infants (less than 9 months) and pregnant women are “at-risk” consumers • NO3-N affects the blood’s ability to carry oxygen, causing methemoglobenemia

  14. Household Water TestSecondary Contaminants • Other regulated analytes on the Household Water Test are Secondary Contaminants that have Federal SDWA Guidelines • Exceeding SDWA Guidelines is not a primary health risk • Secondary contaminants affect aesthetic quality of water (taste, odor, etc.) or damage the water system (hardness, corrosion, etc.)

  15. Household Water TestSecondary Contaminants Secondary contaminants can indirectly affect health: • High sulfates can cause diarrhea which could result in dehydration • Corrosion due to low pH can leach lead from plumbing fixtures which could cause lead toxicity

  16. Corrosiveness of WaterpH – Alkalinity Balance

  17. Household Water TestHardness Hardness is caused by calcium and magnesium (iron also contributes to hardness)

  18. Irrigation Water Test • Price: $12.00 • Analytes: • Sodium (Na) —Chloride (Cl) • Calcium (Ca) —Sulfate (SO4) • Magnesium (Mg) —Nitrate-Nitrogen (NO3-N) • Potassium (K) —Carbonate (CO3) • Boron (B) —Bicarbonate (HCO3) • pH —Electrical Conductivity (EC) • Hardness —Total Soluble Salts (TSS) • Residual Carbonates —Sodium Adsorption Ratio (SAR)

  19. Irrigation Water QualityImportant Analytes •EC (or TSS): determines soil osmotic potential •SAR (or Na%): rates infiltration problem potential •Boron: toxic at very low concentrations •Residual Carbonates (RSC): raises effective SAR/Na%

  20. The Effect of Salinity of Soil Water Availability Salt Concentrations 0.4% = 4000 mg/l 0.2% = 2000 mg/l 0.1% = 1000 mg/l

  21. Irrigation Water QualitySodium (Na) Hazard • Na generally creates soil infiltration problems before becoming toxic to plants • In hot, dry weather conditions sprinkling can lead to leaf burning due to Na toxicity • Na reduces soil permeability by dispersing clay particles which seal larger pore spaces • Na hazard is greater high clay content soils • Na hazard is greater in expanding clays than in non-expanding clays

  22. Infiltration Problem Potential From High Na+ Water EC = 1305 mmho/cm SAR = 19.0 EC = 1769 mmho/cm SAR = 8.5

  23. Irrigation Water QualityBoron (B) • Crops are very sensitive to boron • Threshold soil concentration for yield reduction: 0.3 – 10 mg/l • Toxic to all vegetation: 30 mg/l • Typical Boron toxicity symptoms are spotting, yellowing and/or drying at tips and edges of older leaves

  24. Irrigation Water QualityResidual Carbonates (RSC) • Excessive residual bicarbonate and carbonate in irrigation water will combine with Ca and Mg ions in soil • This effectively increases the SAR and leads to greater risk of infiltration problems RSC = (CO3 + HCO3) - (Ca + Mg)

  25. Salinity Units and Terms(Electrical Conductivity) 1 mmho/cm = 1 dS/m 1 mmho/m = 1000 mmho/cm 1 dS/m = 1 mS/cm EC = electrical conductivity of water ECe = electrical conductivity of saturated extract

  26. Water Quality Units and Terms(Concentrations) 1 mg/l = 1 ppm 1 mg/l = 1000 mg/l 1mg/l = 1 ppb TSS = Total Soluble Salts TDS = Total Dissolved Solids TSS  TDS TSS, (mg/l)  640 x EC, (mmho/cm)

  27. Water Quality Units and Terms(Concentrations) meq/l = milliequivalents per liter epm = equivalents per million 1 meq/l = 1 epm Ion ppm per meq/l Ion ppm per meq/l Ca 20 CO3 30 Mg 12 HCO3 61 Na 23 SO4 48 K 39 Cl 35.5

  28. Derived Water Quality Terms SAR = Sodium Adsorption Ratio SAR = Na (Ca+Mg)/2 Na% = Sodium Percentage Na% = (Na x 100) (Ca+Mg+K+Na) RSC = Residual Sodium Carbonates RSC = (CO3 + HCO3) - (Ca + Mg) (the 3 calculations on this page are in meq/l)

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