Laserfiche WebLink
1 <br />1 <br />[I <br />1 <br />1 <br />1� <br />�l <br />17 <br />RELATIONSHIPS BETWEEN PRECIPITATION, <br />RIVER STAGE, AND GROUND WATER LEVELS <br />Examining the data to determine these relationships among precipitation, ground water <br />levels, and river levels took several forms. Eventually, two approaches were judged to be <br />the most technically supportable: <br />• Daily analysis. —A critical day -by -day analysis of the fluctuations at individual wells <br />superimposed on the river elevations at the well transect location. <br />• Statistical analysis.— Correlation of rises and falls in the water levels at the wells <br />and at the river gauges. <br />RESULTS OF DAILY ANALYSIS <br />Hydrographs of several wells in the Minden transects and in the Alda transects were <br />superimposed on the river hydrograph and the relative gains and losses on a day -by -day <br />basis were examined. The wells were selected to represent various distances from the <br />river. Precipitation data was also displayed. Each significant change in ground water <br />level was studied to determine whether the water table was responding to changes in the <br />river, to precipitation, or to some other factor. <br />This analysis also looked at the correlation factor between the water level in the well and <br />the river stage (water level) and at the bank storage analysis of how the well would <br />respond to the actual changes that occurred in the river elevation. This analysis is <br />provided in appendix B. <br />Several patterns developed in the course of this analysis: <br />• The correlation factor consistently decreased as the distance from the well to the <br />river increased. <br />The water table is far <br />more responsive to <br />precipitation than to <br />changes in the river <br />stage at all wells located <br />more than one half mile <br />from the river. <br />• The bank storage analysis accurately predicted the water <br />table changes resulting from river stage changes in many <br />instances. There were no instances where the bank <br />storage analysis was found to be in error. <br />• The water level in all wells responded to precipitation in <br />a fairly predictable pattern, although the magnitude of <br />change was sometimes out of proportion to the <br />precipitation amount. <br />Ground Water and River Flow Analyses <br />