Modeling thermal structure variations in a stratified reservoir

In this work the effects of hydrologic and atmospheric conditions changes in the thermalstructure of the Alqueva reservoir are investigated. Reservoir water temperatures andthermal stratification have a strong influence on ecological processes; therefore a goodunderstanding of their dynamics is of major importance when studying eutrophicatedreservoirs. A finite element model (RMA10) was used to simulate flow and temperature inthe Alqueva reservoir, the largest western European lake. Survey and monitoring data fordifferent years were used to calibrate and validate the model. Simulated temperaturescompared well with observations at different monitoring stations. Model results showedthat the reservoir has a stable thermal stratification during summer. A sensitivity analysiswas performed to determine the relative importance of environmental factors, such astributary inflows and wind, affecting water temperatures and heat fluxes in this stratifiedreservoir. Model results show that the Guadiana river inflow dynamics has an impact in theupper part of the reservoir. Inflow rate variations affect water temperatures and thedistributions of dissolved oxygen and nutrients in that area. Consequently Guadiana inflowchanges can shift in time and location phytoplankton populations.