Seasonal and Long‐Term Variations of Dissolved Solids in Lakes and Reservoirs

Abstract

The seasonal and long‐term variations of dissolved solids in lakes and reservoirs are analyzed in accordance with the hydrologic‐ and mass‐balance equations. The volume and surface area are expressed as power functions of depth that yield analytical solutions for the long‐term analysis. The equation defining the water elevation and volume may be approximated by exponential functions that simplify the solution of the mass‐balance equation of the dissolved solids. For the intermediate and seasonal time scales, periodic and exponential functions define the hydrologic components, providing the forcing functions for the dissolved solids equations. For both cases, an exponential residence time transforms the mass‐balance equation, leading to analytical solutions. Given the mass and volume, the concentration follows. The temporal variations of dissolved solids, calculated by the associated mass and volumetric equations, are compared to the observed change in salinity in lakes and reservoirs of various geophysical and hydrological characteristics.