Salinity Intrusion in the Panama Canal

Abstract

Abstract : The Panama Canal connects the Atlantic and Pacific Oceans for purposes of navigation. On its way it crosses Miraflores Lake and Gatun Lake. Three navigation locks at each end of the Canal lift ships from the ocean to Gatun Lake through a height of 26 m (83 feet) above sea level and then lower them through three locks, bringing them back to the ocean level. Fresh water from Gatun Lake used for filling the locks is eventually lost to the sea while transferring ships from the lake to the sea. The net loss of fresh water is about 32 million gallons per lockage operation. Salt water from the ocean gets added to the lake during transit of ships from the ocean to the lake. Currently about 38 ships transit the Canal daily. The Panama Canal Commission (PCC) is considering engineering options for increasing the number of vessels transiting each day. It is feared that increased saltwater intrusion may occur and the Gatun Lake water may also become unsuitable for drinking. The Coastal and Hydraulics Laboratory of the U.S. Army Engineer Research and Development Center (ERDC), Waterways Experiment Station, (WES), Vicksburg made preliminary computations for the extent of salt intrusion and a feasibility-level evaluation of mitigation measures. The work consisted of the following: (a) Examination of field data, (b) Review of literature on prevention of salt water intrusion in navigation locks, (c) Mass balance model for Miraflores and Gatun lakes. (d) Evaluation of salinity intrusion and freshwater consumption mitigation alternatives. The following numerical tools were developed: (a) A simple mixing analysis coded in spreadsheet form that provides zero-dimensional models for the salinity of individual locks and the two lakes plus a freshwater consumption model for Gatun Lake. (b) A depth-integrated two-dimensional numerical model for dispersive transport of salt water into Gatun Lake.