A simple method of ground water direction measurement in a single bore hole

Abstract

A simple technique to find both the magnitude and direction of ground water flow in a single bore hole, sited in a pervious water bearing medium, is described. The experiment may be performed with tracers which may not be radioactive (like inactive potassium bromide). At any given horizon where velocity measurements are required, the strainer of the bore-hole is divided into three regions, each about 10 cm long. The central region has slits all round as is usually the case for a strainer. The top region consists of two equal semicircular halves, each subtending an angle of 180 degrees at the axis of the strainer, such that one half has slits cut in it as usual while the second half is kept all blind during manufacture. The horizontal line separating the perforated and the blind segments is taken as the reference line. The lower region is similarly constructed as the top one except that its reference line leads or lags behind the reference line of the top region by an angle of 45 degrees. For proper separation of the above three regions, there are buffer zones between any two consecutive regions. Inactive potassium bromide solution is injected in all the three regions. Using three independent brass electrodes, one in each of the three regions, electrical conductivities at regular intervals of time are carried out by using low frequency and low voltage alternating current, the common electro de being the strainer itself. The magnitude of flow can be determined from the information collected from the central region; whereas the data from the top and lower regions give the direction of flow.