Hydro-meteorology of Lake Chapala

Abstract

The purpose of this work is to examine fluctuations of the hydrometeorological characteristics of Lake Chapala, such as air temperature, precipitation, evaporation, atmospheric pressure, wind, water level in the lake and volume of flow of the rivers in the Lake Chapala region. Linear and nonlinear (maximum likelihood) methods of spectral analysis were used to investigate these phenomena. The main periods were identified in the range from hours to decades, obtaining estimates of the mean square amplitudes. The thermodynamic mode of Lake Chapala was also investigated, particularly the vertical-horizontal distribution of temperature of the water and currents. For this purpose, measurements of the distributions of currents and temperatures were performed. Measurements show that Lake Chapala has a quite complex thermodynamic regime and a significant vertical stratification. The differences in temperatures detected between the surface and bottom in the center of the lake were between 0.5 and 1°C and in the eastern part, from 2 to 3°C. The warmest water was located in the lake’s eastern shallow part. The temperature of the water in the central and southern parts of the lake was 1–2°C lower than that of the water at the northern shore. In all the cross-sections, ordinary spatial variations of 3°C on a distance of just 100 to 500 m were registered with a towed device. A buoy station registered the movements of the internal thermal front with a temperature fluctuation of 2°C. The advanced part of the front was accompanied by intense internal waves. The measurements show that the currents in the lake depend strongly on the intensity of the daytime breeze, which enhances wind velocities up to 10 cm s⁻¹ resulting in increases of the water levels of up to 10–30 mm near the shoreline.