Hey Larry, thanks for the videos. They are really making me understand hydrogeology better. I have a question about your draw-down value and subsequent efficiency calculation. Based on the graphs and the data table, draw-down at 1000 minutes is 20 ft not 90 ft, which would make the efficiency over 1. Could you elaborate on where the 90 ft came from?
Excellent Example. Thanks for filling my knowledge gap as a Sanitary Engineer who needed hydrology to meet the water need challenges. But how do we calculate S where there is no monitoring well?
Good question, Andrew. If you use the method in the video with r=well radius, you typically get a non-physical result--S>1. This is because storage in the well is not included in the solution. There are other solutions that include the well bore itself, and they should give you better results for S, but I have not tried doing this so I am not sure how well it will work. I have always used data from a monitoring well (or measurements of deformation) when estimating S. Larry
HI Salah, The calculated drawdown should be 65 ft. The observed drawdown is 90 ft. The observed drawdown is greater than the calculated drawdown because of head losses in the vicinity of the well. This causes the well efficiency to be less than 1 because it is the ratio of the calculated to the actual drawdown. Hope that helps. Larry
