Specific Conductance (COND)Status and TrendsSpecific Conductance (COND) is a measure of how well water can conduct an electrical current. Conductivity increases with increasing amount and mobility of ions. These ions, which come from the breakdown of compounds, conduct electricity because they are negatively or positively charged when dissolved in water. Therefore, COND is an indirect measure of the presence of dissolved solids such as chloride, nitrate, sulfate, phosphate, sodium, magnesium, calcium, and iron, and can be used as an indicator of water pollution. |
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Median specific conductance (COND) exceeded 292.9 µmhos/cm at 46% of all stations and occurred in all tributary basins except Ohio River Basin (the Youghiogheny River watershed is part of the Ohio River Basin) and Choptank River. The most downstream station of the Gunpowder River (Upper Western Shore Tributary Basin) and the Patuxent Basin were among the highest median conductivity. Median conductivity ranged from 101 umhos/cm at the Youghiogheny River station at Friendsville to 1012 umhos/cm at Braddock Run. Stations with lowest median conductivity (24% of all stations) were located in the upper Patuxent Basin, the Upper Gunpowder, the Choptank, the Ohio Basin drainage and in tributaries to the Upper Potomac (Savage River and Town Creek).. Increasing trends occurred at 67% of the stations and decreasing trends occurred at 4%. Stations with decreasing trends were on the Potomac River at Point of Rocks and Whites Ferry. There seemed to be no relationship between median concentration and increasing trends. Significant positive correlation occurred with SO4 at stations in the upper Potomac (above Hancock) and North Branch Potomac and is probably related to acid mine drainage. Positive correlations with PO4 at Catoctin Creek (at MD17), on the Monocacy River at Reels Mill Road and at MD 28, Seneca Creek and the Little Youghiogheny River. Conductance data for sampled locations are summarized in these plots. |
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