Huisman Method I Transmissivity
Huisman Method I Transmissivity Calculation
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This method calculates the transmissivity of a confined aquifer where both the pumping well and the observation well may not fully penetrate the aquifer. Steady state drawdown measurements are required from both the pumping well and the observation well. The calculation method follows that described in Kruseman and de Ridder (1991). The radial distance to the observation well should be less than twice the thickness of the aquifer.
The Huisman Method I uses the equation:
where:
Spartial = observed steady state drawdown
Sfull = steady state drawdown that would have occurred if the well had been fully penetrating
Zw = distance from the bottom of the well screen to the underlying aquiclude
b = distance from the top of the well screen to the underlying aquiclude
Z = distance from the middle of the observation well screen to the underlying aquiclude
d = length of the well screen
D = aquifer thickness
Q = pumping rate
K = aquifer hydraulic conductivity
r = radial distance from the pumping well to the observation well
The summation is continued until n = 6.
Implementation:
1. The procedure first estimates the transmissivity (KD) of the aquifer using the Thiem confined aquifer steady state equation and S(partial) from the observation well, which is the actual measured drawdown.
2. This KD value is substituted into the Huisman I equation above and a corrected drawdown in the observation well is calculated S(full).
3. The newly calculated S(full) is used in the Thiem equation to calculate a corrected KD.
Thiem Equation:
4. The new KD is compared to the old KD and if the difference is greater than 0.001 m2/day, the process is repeated starting at step 2.
By checking Create a File of Calculations, a text file will be created to a filename specified by the user, summarizing results of each iteration of the calculations.