Laserfiche WebLink
1 <br /> means there is a greater amount of leakage through the aquitard and a slower decline in the <br /> drawdown <br /> Manual type-curve matching of pumping test data can be time consuming, each time a match is <br />' attempted, tedious calculations must be performed For this reason, a computer program was used <br /> to assure the best possible match was obtained in a reasonable time frame Groundwater <br /> ' drawdown over time for each well was analyzed using the graphical computer software "Graphical <br /> Well Analysis Package" (GWAP), written by David Dansby of Groundwater Graphics (1986) The <br /> program employs the graphical curve matching technique to obtain the aquifer characteristics of <br /> transmissivay and storativity for a confined, leaky aquifer The curve was manually matched on the <br /> computer screen to data collected at each well Values of transmissivity and storativity are <br />' generated by the program essentially using the aforementioned relationships from the solution of the <br /> basic equation <br /> An alternate method of estimating the aquifer transmissivity (T) uses an approximation of the Theis <br /> equations The Jacob simplification of the Theis equations is applicable wherever u is less than 0 05 <br /> Jacob's equation shows that the relationship between drawdown (s) and log (r) is linear The slope <br /> of the semi-log plot showing the relationship between drawdown and distance from the pumping <br /> well can be used to calculate the transmissivity using Equation (6) derived from the Jacob <br /> simpinccation of the Theis equations <br /> T A 528Q [6] <br /> where AS <br /> T = coefficient of transmissivity (gpd per ft) <br /> Q = pumping rate (gpm) <br /> es - change to drawdown over one distance log cycle (feet) <br /> The groundwater capture zone of a pumping well is bounded in the downgradient direction by the <br />' stagnation point and laterally by the maximum width of the inflow zone Keely (1986) has shown <br /> that these distances can be calculated using Equations (7), (8) and (9) <br /> D = Q [7] <br />' 2nbv <br />' 2879ao34 opo <br /> GROUNDWATER <br />' TECHNOLOGY, INC <br />