ABSTRACT

Sea level, salinity, tidal flow and river discharge data are examined for Lake Calcasieu estuary, southwest Louisiana, using data collected between 1938 and 1990. Lake levels in Calcasieu are rising at an average rate of 0.62 cm/yr and are in accord with regional sea level trends for the northern Gulf of Mexico. The rate of sea level rise is slightly higher toward the estuary mouth, though a clear seaward sloping gradient exists from the upper lake to the tidal inlet. Freshwater inflow is the most likely cause of the hydraulic gradient. Despite rising lake levels, mean annual salinity is not increasing. Rather, lake salinity is strongly correlated with discharge of the Calcasieu River. In addition, trends in lake levels between 1938 and 1988 are independent of variations in mean annual freshwater input. Extreme events, notably hurricanes and river floods, have a catastrophic short term impact upon lake levels but are less significant than long term sea level rise. The hydrologic character of Lake Calcasieu conforms to the general model describing energy distribution in wave-dominated estuaries.