Interpreting well water analyses in Indiana karst (limestone) terranes
The quality of your livestock water source can adversely affect horse health, particularly in rural areas, or barns, with private groundwater wells, which are not regulated by the Safe Water Drinking Act. In this case, it is your responsibility to test the water and monitor groundwater quality.
Examples of groundwater contaminants include potentially toxic minerals (lead, arsenic, cadmium), volatile organics (solvents, fuel components, such as benzene and toluene), inorganic salts (sulfates, nitrates), agricultural chemicals (pesticide and herbicide residues from runoff) and pathogenic organisms from septic systems and manure piles. Refer to the contaminant table published by U.S. Geological Survey for more information on sources and potential health effects of specific contaminants.
In terms of horse nutrition, high concentrations of dissolved minerals in groundwater, such as iron, calcium, magnesium and sulfate (sulfur as SO4) can be important in balancing your horse’s diet.
In this section, we discuss results from a recent analysis of our farm water, which is drawn from a limestone aquifer (St. Louis Limestone, Blue River Group) in the Mitchell Plain (Plateau) near Corydon, Indiana. The Mitchell Plain is one of two important karst terranes in southern Indiana. Read more about karst at the Indiana Geological Survey web site.
Water samples were collected in August 2014 as part of the Indiana State Ground Water Monitoring Network (Indiana Department of Environmental Management, IDEM). Concentrations of over 400 chemical substances were measured at no cost to homeowners and included in a statewide database on groundwater aquifers, which are very susceptible to surface pollution in karst terranes (Unterreiner, 2006, Bulletin 40, Indiana Department of Natural Resources, Water Division).
Sample results are listed below in Table 1. Only those chemical substances above detectable levels are tabulated. No organic compounds, or toxic minerals, were detected. The table is divided into two sections: General Chemistry, which includes Alkalinity, Chloride and Sulfate, and Metals and Minerals. Results are reported in units of milligrams per liter (mg/L), or micrograms per liter (ug/L). For water, 1 mg/L and 1 ug/L are approximately equivalent to one part per million (ppm) and 1 part per billion (ppb), respectively.
Since this well also provides our domestic water supply, we normally test our water on an annual basis. Results as 06.2014 are: bacterial contamination (negative), nitrates (< 0.01 mg/L) and sulfates (13 mg/L).
The property Alkalinity listed under General Chemistry is a measure of the capacity of water to neutralize acids. Groundwater in contact with limestone (a carbonate rock) is concentrated in alkaline compounds such as bicarbonate (baking soda is a type of bicarbonate) and carbonate (CaCO3). These compounds remove hydrogen ions (H+) from the water, neutralizing acids and preventing large changes in pH (measure of H ion concentration; pH = 7 neutral, pH < 7 acidic, pH > 7 alkaline). This is the reason why the pH of lakes and ponds in this area is near neutral (pH = 7) in spite of acidic pollution from rainfall.
Alkalinity in limestone areas is closely related to water hardness because calcium and magnesium, the two minerals that make water “hard”, form carbonate compounds (CaCO3 and MgCO3) in limestone. When limestone comes in contact with groundwater, these compounds are dissolved, concentrating calcium and magnesium in the water. Water hardness is generally expressed in terms of CaCO3 concentration and is considered “very hard” in this area (297 mg/L, or ppm, CaCO3).
Contaminant levels in Table 1 (human standards) are given as either Maximum Contaminant Levels (MCLs), or Secondary Maximum Contaminant Levels (SMCLs). The former is associated with adverse health effects whereas the latter is based on aesthetics, such as color and odor, and does not pose a health risk. The Environmental Protection Agency (EPA) establishes both levels.
Livestock drinking standards are compared to human standards and summarized in this table (Summary Recommendations Oetzel) published by the School of Veterinary Medicine, University of Wisconsin.
Examples of groundwater contaminants include potentially toxic minerals (lead, arsenic, cadmium), volatile organics (solvents, fuel components, such as benzene and toluene), inorganic salts (sulfates, nitrates), agricultural chemicals (pesticide and herbicide residues from runoff) and pathogenic organisms from septic systems and manure piles. Refer to the contaminant table published by U.S. Geological Survey for more information on sources and potential health effects of specific contaminants.
In terms of horse nutrition, high concentrations of dissolved minerals in groundwater, such as iron, calcium, magnesium and sulfate (sulfur as SO4) can be important in balancing your horse’s diet.
In this section, we discuss results from a recent analysis of our farm water, which is drawn from a limestone aquifer (St. Louis Limestone, Blue River Group) in the Mitchell Plain (Plateau) near Corydon, Indiana. The Mitchell Plain is one of two important karst terranes in southern Indiana. Read more about karst at the Indiana Geological Survey web site.
Water samples were collected in August 2014 as part of the Indiana State Ground Water Monitoring Network (Indiana Department of Environmental Management, IDEM). Concentrations of over 400 chemical substances were measured at no cost to homeowners and included in a statewide database on groundwater aquifers, which are very susceptible to surface pollution in karst terranes (Unterreiner, 2006, Bulletin 40, Indiana Department of Natural Resources, Water Division).
Sample results are listed below in Table 1. Only those chemical substances above detectable levels are tabulated. No organic compounds, or toxic minerals, were detected. The table is divided into two sections: General Chemistry, which includes Alkalinity, Chloride and Sulfate, and Metals and Minerals. Results are reported in units of milligrams per liter (mg/L), or micrograms per liter (ug/L). For water, 1 mg/L and 1 ug/L are approximately equivalent to one part per million (ppm) and 1 part per billion (ppb), respectively.
Since this well also provides our domestic water supply, we normally test our water on an annual basis. Results as 06.2014 are: bacterial contamination (negative), nitrates (< 0.01 mg/L) and sulfates (13 mg/L).
The property Alkalinity listed under General Chemistry is a measure of the capacity of water to neutralize acids. Groundwater in contact with limestone (a carbonate rock) is concentrated in alkaline compounds such as bicarbonate (baking soda is a type of bicarbonate) and carbonate (CaCO3). These compounds remove hydrogen ions (H+) from the water, neutralizing acids and preventing large changes in pH (measure of H ion concentration; pH = 7 neutral, pH < 7 acidic, pH > 7 alkaline). This is the reason why the pH of lakes and ponds in this area is near neutral (pH = 7) in spite of acidic pollution from rainfall.
Alkalinity in limestone areas is closely related to water hardness because calcium and magnesium, the two minerals that make water “hard”, form carbonate compounds (CaCO3 and MgCO3) in limestone. When limestone comes in contact with groundwater, these compounds are dissolved, concentrating calcium and magnesium in the water. Water hardness is generally expressed in terms of CaCO3 concentration and is considered “very hard” in this area (297 mg/L, or ppm, CaCO3).
Contaminant levels in Table 1 (human standards) are given as either Maximum Contaminant Levels (MCLs), or Secondary Maximum Contaminant Levels (SMCLs). The former is associated with adverse health effects whereas the latter is based on aesthetics, such as color and odor, and does not pose a health risk. The Environmental Protection Agency (EPA) establishes both levels.
Livestock drinking standards are compared to human standards and summarized in this table (Summary Recommendations Oetzel) published by the School of Veterinary Medicine, University of Wisconsin.
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The iron and sulfate concentrations in our well water are very low, which is good news because these substances have a negative (antagonistic) effect on the absorption and bioavailability of other minerals in your horse feed. We mentioned earlier that iron limits the absorption of both copper and zinc and sulfate can interfere with the absorption of copper.
The relatively high concentrations of calcium and magnesium will add a small but significant amount of these minerals to your horse’s diet. To find out how much, let’s assume that your horse drinks on average about 7 gallons of water per day (26 liters). For calcium, 58 mg/L x 26 L = 1508 mg = 1.5 g. For magnesium, 37 mg/L x 26 L = 962 mg ~ 1 g. Adding these amounts to your diet calculation will account for the mineral contribution from drinking water.
The take-home message from all of this is that you need to test your water source as well as your forage. In karst terranes, it is particularly important to sample at different times of the year to evaluate seasonal changes in groundwater quality.
For Indiana horse owners, we recommend that you take advantage of the groundwater monitoring program offered by IDEM. It’s free and you can obtain valuable information about water chemistry and how it might affect horse health and nutrition.
The relatively high concentrations of calcium and magnesium will add a small but significant amount of these minerals to your horse’s diet. To find out how much, let’s assume that your horse drinks on average about 7 gallons of water per day (26 liters). For calcium, 58 mg/L x 26 L = 1508 mg = 1.5 g. For magnesium, 37 mg/L x 26 L = 962 mg ~ 1 g. Adding these amounts to your diet calculation will account for the mineral contribution from drinking water.
The take-home message from all of this is that you need to test your water source as well as your forage. In karst terranes, it is particularly important to sample at different times of the year to evaluate seasonal changes in groundwater quality.
For Indiana horse owners, we recommend that you take advantage of the groundwater monitoring program offered by IDEM. It’s free and you can obtain valuable information about water chemistry and how it might affect horse health and nutrition.
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