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<br />*~\ <br /> <br />-rs- J~.-'~""'" <br /> <br />( <br /> <br />..... <br />-.] <br />IV <br />I-' <br /> <br />Oiscussion of Flow-Weighted Salinity and Sa~pling <br />Stations Used in the Monthly Water Reports of the <br />Colorado River Board of California <br /> <br />Salinity is a measure of the total dissolved matter, or <br /> <br />total dissolved solids (TDS), contained in a water sample and <br /> <br />is reported in terms of concentration, generally as either <br /> <br />milligrams per liter (mg/l) or its equivalent, parts per million <br /> <br />~ <br />" <br /> <br />(ppm) . <br /> <br />TDS is determined by making a complete chemical analysis <br /> <br />of a water sample, identifying all constituents present and <br /> <br />summing them. <br /> <br />In the Board's monthly water report, this method <br /> <br />is referred to as "sum of constituents". <br /> <br />A quick, inexpensive and convenient way of approximating TDS <br /> <br />is to measure the electrical conductance (EC) of water. Elec- <br /> <br />trical conductance is the ability of water to conduct an <br /> <br />electrical current and is measured in micromhos. Chemically <br /> <br />pure water has little conductivity. As TDS increases, the water <br /> <br />becomes more conductive and the EC becomes higher. EC is not a <br /> <br />(.,. <br />J....~~.. <br />"I): <br />~... <br />,,"0 <br />1-:: <br />~ <br />if <br />^ <br /><,.." <br />r I <br />r, <br /> <br />direct measure of TDS. The EC must be multiplied by a convers~on <br /> <br />factor which generally ranges from 0.55 to 0.75. This factor is <br /> <br /> <br />determined by dividing TDS, calculated as the sum of the con- <br /> <br /> <br />stituents, by EC. The factor for Colorado River water is in the <br /> <br />0.62 to 0.~4 range. <br /> <br />..- <br />Another inexpensive means for approximating TDS is to <br /> <br />evaporate a water sarnple at 180 degrees Celsius and weigh the <br /> <br />residual. . The value determined by the residue method may differ <br /> <br />from the sum of constituents as gases are drive~ off, some com- <br /> <br />, <br /> <br />pounds are changed! and others are hydrated or volatilized at <br /> <br />.~-._--_.. .~------,--_._--- -....- -. ._-~- <br /> <br />,',c., ~'oJ;, .. ~J' <br /> <br />