This page provides guidance for using an Excel spreadsheet designed to estimate contributions of chloride to shallow groundwater from nine different sources. The calculator allows the user to adjust inputs for each source and produces an estimate, in pounds per acre or kilograms per hectare, from each source and cumulatively for all sources. The nine sources, described in greater detail below, include the following.
Before using the calculator, we strongly recommend reading the following.
This input includes leakage from water distribution systems. There is always some leakage from these systems since they are under pressure.
The default annual infiltration rate (I) is based on the following equation
\( I = P * F_{precipitation} * L \)
where
L is the leakage rate from the piped infrastructure, as a fraction of total piped inflow.
The term Fprecipitation is used because most literature expresses the volume of piped inflow as a percentage of precipitation. For example, studies suggest that a typical volume of piped inflow is about 50% the value of annual precipitation volume. Leakage represents an annual average value. For example, if 15% of the annual piped inflow is lost through leakage, the value for F is 0.15. The terms Fprecipitation and L are thus unitless.
Users who have data for the volume of piped inflow should use that data. In this case, the formula in cell B12 would be rewritten as L times the annual volume of piped inflow divided by the area with piped inflow. For example, if the leakage rate is 0.15 the annual piped inflow is 1000 ft3, and the area with piped inflow is 100 ft2, the annual infiltration rate (I) equals 0.15 * 1000 / 10 or 1.5 inches per year.