Hydraulic properties and uncertainty analysis for an unconfined alluvial aquifer

An inverse computational method was used to analyze pumping and recovery tests conducted in an unconfined alluvial aquifer along the Republican River valley in Nebraska, At each test site, a high-capacity irrigation well was used as a pumping well, and eight observation wells were constructed to measure drawdown during the pumping and recovery tests. The test data were analyzed for four hydraulic parameters: the vertical (K(z)) and the radial (K(r)) hydraulic conductivity, the storage coefficient (S), and specific yield (S(y)), This method provides not only the average values but also estimated standard errors, confidence intervals, and correlation for the aquifer parameters. The standard error and confidence interval indicate the quality of the parameter estimates, and the correlation coefficients are useful in the evaluation of the relationship among the four parameters. High pumping rates seemed to reduce the effects of well borehole storage on drawdown, Because of the significant amount of early-time data collected, the tests gave high-quality S values, K(r) values for most observation locations range from 90 to 120 m/d, It was found that K(r) and S(y) had a higher correlation and the ratio of K(r)/K(z) varied from approximately 10 to 30.