Assessing the Impacts of Climate Scenarios over Lakes Through a 1dv Model

Lakes are water bodies that offer several environmental services and support to human activities. Water quality in lakes are influenced by a long list of driving forces that include atmospheric and hydrologic variables, land use in the catchment area and water demands. Climate conditions, sediment loads, and pollutants play expressive roles in the hydrodynamic behavior of lakes, affecting the thermal stratification and mixing regime standards that affect directly the water quality. Numerical models can simulate the thermal regime of lakes and reservoirs considering different boundary conditions as solar radiation, water in and out fluxes and constituent concentrations but often require a full extensive set of 3D information to produce accurate results. This paper intends to evaluate the capability of a 1D vertical transport model – GLM, with automatic calibration routines, to access the impacts of different climate scenarios that can affect the thermal regime and pollutants concentrations. The GLM model is a very practical tool that requires less topology information and process parameters than 2D or 3D models. Associated to automatic calibration routines and a good set of observed data it is possible to obtention fast and efficient responses to different scenarios. The reservoir used as case study is formed by Hedberg Dam, located about 90 km from Sao Paulo city in Brazil and is a 0,2 km²-4.5m depth pond built in the beginnings of the 19^th century. The hydrological catchment area is partially protected with some sparse urban occupations. Water temperature profiles were monitored in high resolution as well as atmospheric variables. Nutrients concentrations and Secchi depth were taken monthly along a full year. The GLM model was calibrated considering the observed period and used to simulate projected climate scenarios considering changes in solar radiation, temperature, air humidity, wind and precipitation. Results show important changes over lake thermal regime and phytoplankton concentrations.