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Regionally, the top surface of the saturated zone is visualized as flat as the top of a table and hence this surface is referred to as the water table. The regional water table is not as flat as we presume. The water table tends to follow the shape of the topography. Therefore, the water table is not quite flat in an undulating area but tends to take shape akin to the topography.

For example, if the static water level in a well is found to be at 10 ft below ground level (bgl), the water level in another nearby well located at a ground elevation of 20 ft higher than the other, will not show water level at 10 ft + 20 ft = 30 ft bgl, but considerably higher. Had the water table been flat, the second well water table should have been 30 ft bgl. For this reason, it is not true that the shallower the depth of the water table more is the yield of the well. In other words, the depth of the water table is not always a good indication of the yield of the well.

The property of the aquifer, called permeability (ease of flow) determines the yield of a well. The aquifer’s permeability also influences the shape of the water table. Water table would tend to rise higher in that part of the aquifer where aquifer permeability is relatively low and vice versa. As mentioned earlier, a shallow water table encountered in a dug well is not necessarily an indication of a higher yield. Another well in the vicinity with a deeper water table can yield a higher quantity of water due to the better permeability of the aquifer.

Seasonal fluctuation of the water table is also relatively high within an aquifer of poor permeability than in a more permeable aquifer. Indeed, the better yielding dug wells are usually found at depressions and valleys rather than on a ridge or high ground. The formation at the depression or valley is more weathered (permeable) and receives more recharge.

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