A Straight-Line Method for Analyzing Residual Drawdowns at an Observation Well

Determination of the hydraulic parameters (transmissivity and storage coefficients) of a confined aquifer is important for effective groundwater resources. For this purpose, the residual drawdowns have been in use to estimate the aquifer parameters by the classical Theis recovery method. The proposed method of this paper depends on a straight-line through the field data and it helps to calculate the parameters quickly without any need for long-term pumping data. It is based on the expansion series of the Theis well function by consideration of three terms, and this approach is valid for the dimensionless time factor u ′ = S ′ r 2 / 4 T t ′ ≤ 0.2 . The method can be applied reliably to extensive and homogeneous confined aquifers resulting in different storage coefficients during the pumping and recovery periods S ≠ S ′ . It presents a strength methodology for the parameters decision making from the residual data in the groundwater field of civil engineering.