Abstract In this thesis two techniques have been developed for the measurement of both the magnitude and the direction of groundwater flow under some natural gradient. These have the advantage that in spite of being single well techniques; it is not necessary to radioactive tracers for direction measurements. Consequently no health hazards, no costly equipment and, therefore, no foreign exchange component is involved in their operation. Both these component is involved I n their operation. Both these techniques have been published in the international journal of repute viz: journal of hydrology (Netherlands) in its different issues (see references). In the first technique, the groundwater flow has been considered as a vector quantity, consequently by introducing another vector quantity, of known magnitude and direction, both the direction as well as the magnitude of the unknown vector quantity can be easily determined. The new known vector quantity, in groundwater hydrology, can be introduced by installing a small pumped well in the vicinity of an observation well (hence forth called master well ). All flow measurements are carried out in this master well when the tubewell is in operation and when it is not in operation. A non radioactive solution of potassium bromide is injected in the master well at horizon where flow measurements are desired. Dilution of this tracer (potassium bromide) takes place due to the groundwater flow. The dilution rates are computed by measuring, at different time intervals, the electrical conductivities (reciprocal of resistances) by using a wheatstone bridge arrangement energized with low voltage alternating current. Using the mathematical formulae developed in this thesis and the data so collected the magnitude of the groundwater flow can be easily determined. After this the tubewell is started at a discharge such that the velocity, due to pump age, introduced at the master well is in comparison to the velocity of the groundwater flow already measured. The magnitude of the resultant is again determined in the same master well in the some manner as for the case of groundwater flow in the absence of the tubewell. These observations help in determining the direction of the flow of groundwater. Instead of one discrete direction of flow, the mathematical formulae give four directions of flow. For further differentiation among these four directions, to get the true direction of flow, a simple experiment in also described. In the second technique, which strictly a single well technique, no additional tubewell is required. All flow measurements are carried out in the same observation well both for determining the magnitude as well as direction of flow and no radioactive tracers are needed. The observation well, this time, is specially prepared, over short lengths, at those horizons where flow measurements are required. The remaining length of the bore is quite identical with that used in the previous technique. Thus at the selected points, the well screen, instead of being uniformly perforated (slotted) all round, is such that it is slotted over 180o while the remaining half is all blind. The dilution rates of the injected salt, if computed in this type of bore hole, are a function of the relative orientation of the slotted segment with respect to the direction flow which can, therefore, be easily determined. Apart from the measurement of magnitude and direction of flow, the formulas developed in this thesis have also practical side applications in determining (1) seepage losses from big irrigation channels and (2) the rate and amount of incrustation in tubewells at different horizons. Apart from these two applications, it is also possible to determine the permeability coefficient of a complicated strainer material like coir string (coconut fibre string). A strainer prepared with such a has a permeability which cannot ordinarily be determined. The reason being that apart from the fine slits of irregular widths between two consecutive string windings, the string in itself is porous, the measurement of these strainer permeabilities are necessary to determine the head loss through the strainer. This head loss has a great impact on the incrustation of the strainer. Both the formulae as well as the technique for determining these permeabilities are also described in this thesis.
