CHAPTER ONE
INTRODUCTION
1.1 Background of Study
Conductivity is a measure of the ability of water to pass an electrical current. Conductivity in water is affected by presence of inorganic dissolved solids such as chloride, nitrate, sulfate and phosphate anions (ions that carry a negative charge) or sodium, magnesium, calcium iron and aluminiumcations (ions that carry a positive charge). Organic compounds like oil, phenol, alcohol and sugar do not conduct electrical current very well and therefore, have a low conductivity when in water. Conductivity is also affected by temperature: the warmer the water, the higher the conductivity. For this reason, conductivity in streams and rivers is affected primarily by the geology of the area through which the water flows. Streams that run through areas with granite bedrock tends to have lower conductivity because granite is composed of most inert materials that do not ionize (dissolve into ionic components) when washed into the water. On the other hand, streams that run through areas with clay soils tend to have bugler conductivity because of the presence of materials that ionized when washed into the water. Ground water in flows can have the same effects depending on the bed rock they flow through.
Discharge to streams can change the conductivity depending on their make-up. A failing sewage system would raise the conductivity because of the presence of chloride phosphate and nitrate; an oil spill would lower the conductivity. The basic unit of measurement of conductivity is the mio or siemens. Conductivity is measured in michrombo per centimeter (Nmhos/cm) or merociemens per centimeter (Ns/cm). distilled water has a conductivity in the range of 0.5 to 3 Nmhos/cm. the conductivity of rivers in the United States generally ranges from 50 to 1500 Vintios/cm. Studies of inland fresh waters indicate that streams supporting good mixed fisheries, have a range between 150 and 500Ntios/cm. conductivity outside this range could indicate that the water is not suitable for certain species of fish or macroinvertebrates. Industrial waters can range as high as 10,000 Nmtios/cm.