5.1.1 Basic equation of ground-water flow
It has been shown by Jacob in 1947 that the drawdown in the
vicinity of an artesian well varies according to the following equation:
s = [264 Q/T] log [0.3 T t/r2S] (1)
Q = discharge of the well [gpm]
T = aquifer Transmissivity [gpd/ ft] = K b
t = length of time pumping [days]
r = distance away from the pumping well [ft]
S = aquifer Storage coefficient
Aquifer Transmissivity (T) is defined as the product of the
Hydraulic Conductivity (K) times the saturated thickness (b). An estimate of the
aquifer Transmissivity in the Pleasant Valley area can be made by applying the
following relation (Theis et. al.1963):
T = 2000 Q/s (2)
where: T = aquifer Transmissivity [gpd/ ft]
Q/s = specific capacity of the well
after 1 day [gpm/ ft]
5.1.2 Estimation of Aquifer Hydraulic Conductivity
Due to interlayering of aquifers and aquitards in the Pleasant
Valley area, it is safe to assume that the length of the well screen installed in the
Pleasant Valley wells is equivalent to the total saturated aquifer thickness penetrated
by the well (ie. Saturated thickness (b) = sum of installed screen lengths).
Knowing the saturated aquifer thickness in each well, Hydraulic
Conductivity (K) can be calculated from the estimate of Transmissivity (T) as follows:
