Upconing of Fresh Water—Sea Water Interface Below Pumping Wells, Field Study

Field investigations on the upconing mechanism of interface under the influence of pumping were carried out to check the validity of the existing theoretical formulas, to study the salinization of pumped water as related to the position and characteristics of the interface, and to provide some analytic design procedures for skimming fresh water from above saline water bodies. It was found that the existing theoretical formulas describing the upconing interface are in agreement with field results up to some critical rise of the interface, which seems to be approximately half the distance between the bottom of the well and the undisturbed interface. In addition, the use of the linear approximation for the dispersion pattern was justified as a first approximation of the resultant transition zone. The salinization of the pumped water is probably caused by the intrusion of saline water above a certain critical depth. From correlation analysis, the salinity increase of pumped water is about 5 to 8% of the average salinity of the saline water intruded above the critical depth. The average salinity above the critical depth is determined by the existing formulas corrected for dispersion. Design procedures based both on theoretical formulas and field investigations are summarized in the form of nomograms. These nomograms were constructed on the assumption that the mixing mechanism for other geometries is similar to the observed one.