Some unreliable types of ground-water observation wells

Several primary requirements must be fulfilled by any observation well that is to be used as an indicator of ground-water levels over considerable distances. First of all, the water level inside the well must be the same as that outside of the well. the water level inside the well must be able to adjust to water -level fluctuations in the aquifer within a certain period of time, that time dependent upon the type of study for which the observations are to be used. Finally, to be of value in most areal studies, the water level outside the well must be representative of the level throughout the aquifer, and not reflect merely some speical local condition. Should any of these requirements remain unsatisfied, the derived data may be misleading.