STUDY OF FLOW ANALYSIS IN SEMI-CONFINED AQUIFER USING A SAND TANK MODEL

Under field conditions the aquifer geometry rarely confirms to the concept of one aquifer system. In a borehole it is common to find number of aquifers. When the aquifers are separated by aquicludes, interaction between the aquifers is only through the well screens. However, when aquifer is separated by aquitards, the intersection between the aquifers takes place through the aquitards besides the well screens. In general, a tubewell has a strainer length of the aquifer depth. To curtail some cost of installation a partially penetrating well may be good provided the discharge does not drop down significantly due to partial penetration. But the hydraulics of a partially penetrating well in a leaky aquifer is different from that of confined aquifers. A well in a leaky aquifer withdraws water not only from the aquifer but also from the overlying semi- pervious layer. Steady case is possible in such case because o frecharge through the semi- pervious layer. During unsteady conditions the head varies with time. To study the relationships between drawdown-discharge of the well and radial distance, a sand tank model was developed. The experiements have been carried out in the sand tank model where a leaky aquifer environment was created. The results so obtained for five different degrees of penetration have been analysed for varying discharge conditions.