During wet weather periods and during the spring thaw in colder regions, more fresh water enters the estuary, so salinity is lower at these times. On the other hand, dry weather periods mean less fresh water entering the estuary, so higher salinity levels may be found. Another way the seasons influence an estuary's salinity involves the mixing of fresh water and salt water. Seasonal storms help mix estuarine waters and serve to decrease the vertical temperature gradients in the estuary. Choosing a Sampling Method Salinity can be measured either by physical or chemical methods.
Physical methods use conductivity, density, or refractivity.
The physical methods are quicker and more convenient than the chemical methods. Conductivity Conductivity is a measure of the ability of water to pass an electrical current. As the concentration of salts in the water increases, electrical conductivity rises-the greater the salinity, the higher the conductivity. 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 measured with a probe and a meter.