Research paper: Water Resources Management Small reservoir water dynamics modeling

Abstract

Abstract Small reservoirs play a key role in agricultural development in the Brazilian Savannah (Cerrado) region. They contribute to diminish rural communities’ vulnerability to drought and improve the livelihood of rural populations. Thousands of small reservoirs have been built in the last few decades in the Cerrado, but efficient water management and sound planning are hindered by inadequate knowledge of their water dynamics. Studies related to small reservoir water dynamics are generally scarce in the world hydrological literature. The main objective of this study was to develop a dynamic simulation model based on the system dynamics model to evaluate the water dynamics in small reservoirs over time, and the risk of not meeting the predicted water demand. Daily data on reservoir inflows were obtained for the period from October 2009 to September 2011, and extended to June 2015 through modeling. The developed model was calibrated and validated with historical data. The main variables which have impact on the water volume were evaluated through sensitivity analysis. The results indicated that reservoir inflow was the variable which had the highest impact on water volume in the reservoir, followed by the reservoir surface area and by evaporation and infiltration, which together represented 14.4% of reservoir inflow. The risk assessment of not meeting the predicted water demand showed that the water in the reservoir was above the critical level 85.9% of the time and that 81.6% of the reservoir water was available to meet water demand. Small dams pose a risk of not meeting the community’s water demand at least 18% of the time.