Coupling meteorological forecasts with hydrologic and hydraulic models: The Itaipu Dam ensemble inflow forecasting system

<p>This work presents the development of the inflow ensemble forecasting system for Itaipu Dam. The system is based on combination of twelve Quantitative Precipitation Forecast (QPF) with three hydrological models and one hydrodynamic one-dimensional model. The QPF are provided by different meteorological institutions based in the results of the global Numerical Weather Prediction (NWP) models GFS and ECMWF, as well as of the regional NWP models WRF and COSMO executed by the Brazilian and Paraguay meteorological services (SIMEPAR, INMET and DINAC). The semi-distributed model MGB – Large Basin Model, the lumped models SMAP and HEC-HMS are considered as the hydrological models. Furthermore, the computed flows are propagated in a HEC-RAS scheme designed with extensive field data from bathymetry of Parana River and tributaries. The daily results are presented as fifteen inflow scenarios that are considered for the definition of a unique flow forecast. Finally, that forecast is used for the electric generation scheduling of the power plant. Each of these fifteen methods performance was evaluated as well as the suitability of the system for it purposes. For a short-term forecast horizon (less than 4 days), the performances of the hydrological models forced by the different rain forecast are quite similar. However, it is remarkable the difference between the results of the three hydrological models for the same horizon. On the other hand, for medium-term horizon (more than 4 days) both hydrological and meteorological models have diverse behavior and contribute for a wide representation of the possible scenarios. Overall, it has been showed that the simulations are complementary and provides to the forecaster a general overview of the hydrologic situation. Nevertheless, at this moment, further analysis of accuracy and reliability of the prediction have not been realized, so the forecaster needs to appeal to its own expertise to assure the consistence of the scenarios for decision-making.</p>

Comprehensive Assessment for the Potential Environmental Impacts of the Grand Ethiopian Renaissance Dam on the Downstream Countries: Itaipu Dam in the Rearview Mirror

This article provides a comparative environmental assessment for the Grand Ethiopian Renaissance Dam (GERD) learning from Itaipu dam experience. The article gives a full insight about the potential political and technical concerns that may affect the downstream countries as a result of the construction of GERD and proposed a solution and way forward for the negotiation based on joint collaboration perspective. Based on the analytical comparison conducted between GERD and Itaipu, the results showed that the total annual carbon dioxide (CO2) emissions expected to be released from the GERD during the operation is 3,927 tCO2eq, while other secondary emissions were estimated to be 16.17 tons, mainly of carbon monoxide and nitrogen oxides. Also, the ratio of power generation to reservoir capacity of the GERD was questionable, since Ethiopia has announced that the dam is built only for power generation and that there is no intention to utilize water from the dam reservoir. On the other side, the water quality - represented in turbidity, total suspended solids (TSS), dissolved oxygen (DO), total phosphorus (TP), and chemical oxygen demand (COD) - behind the GERD is expected to deteriorate dramatically. Also, an increase in total nitrogen (TN) is expected to occur depending on human activities. Accordingly, the article discussed thoughtfully the potential adverse impacts of the GERD on downstream countries and the possible mitigation options. The article also extended to discuss proposals for practical solutions that pave the road for joint collaboration between the three countries to achieve a transparent resolution and a fair resources utilization.