Upper and Middle Tiete River Basin dam-hydraulic system, travel time and temperature modeling

Abstract

Summary Tiete River System in the State of Sao Paolo, Brazil is characterized by complex hydraulics and operational problems due to series of dams and point and diffuse inflows along the river. A one dimension Lagrangian river model was developed and applied to the 313 km reach of the Upper and Middle Tiete River Basin from the Penha Dam to the head water of Bara Bonita Reservoir, a stretch of river that includes six small to medium size dams (3.4–22 m high) including the Pirapora Reservoir and 26 inflows into the river (11 tributaries, 9 diffuse source areas, and discharges of 4 cities stormwater and 2 wastewater treatment plants. The conservative tracer transport and temperature model that accounts for the short and long wave radiation and heat transfers at the free surface was included and solved using the Crank–Nicholson scheme. The time variable catchment input to the model was the simulated output of the external hydrological model called Runoff Load Model which results were provided by CETESB. The numerical treatment of series of dams and spillway (that included uncontrolled overflow spillway, gate-controlled ogee spillway; and underflow gates and tunnels) and parameterisation of hydraulic jumps are described. Special attention was focused on the high spatial and temporal variation of flows in Tiete River Basin, a result of the large variation in catchment inflows and channel geometry due to dams and reservoirs along the river. Predicted and measured spatial and seasonal variation of flow and temperature profiles along the river show good agreement. The simulated travel time of conservative tracer is compared against the CETESB’s 1982 and 1984 field study data in a 254 km reach of the Middle Tiete River that again shows good agreement. Being Lagrangian in construction, this new model is computationally efficient making it an ideal tool for long term simulation for water resource planning, management and operation decision making in a large and complex river basin system.