Musandji Fuamba

This study assesses the potential impact of climate change on hydropower generation, focusing on the Grand Inga hydropower project on the Congo River in the Democratic Republic of Congo. Utilizing a multi-input approach with a conceptual HEC-HMS hydrologic model, this research incorporates a new bias-corrected high-resolution daily downscaled dataset, NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP CMIP6), and its predecessor (CMIP5) under various climate scenarios. The hydropower generation at Inga Falls is simulated using a hydropower model, considering observed and simulated daily flows for different climate models and emission scenarios. The results suggest that the Grand Inga project will be resilient to negative climate impacts during its initial phases (1–5). The system demonstrates security and insensitivity to adverse changes, both for existing (Phase 1–2) and planned (Phase 3–5) hydropower components. This study indicates that climate change effects become apparent only in later phases (6–8), with predominantly positive impacts, potentially increasing the generation potential of the hydropower system. Overall, the Grand Inga hydropower project appears robust against adverse climate influences throughout the majority of its development phases.

The Congo River Basin is the second-largest watershed globally, flowing through nine countries before reaching the Atlantic Ocean. The Kasai River Basin (KARB), containing about one-fourth of Congo’s freshwater resources, plays a strategic role in sustaining navigation, food production, and hydroelectricity generation in Central Africa. This study applies a multi-model framework suited for data-scarce regions to assess climate change impacts on water availability in the KARB. Using two conceptual hydrological models calibrated with four reanalysis datasets and fed with bias-corrected outputs from 19 climate models under two representative climate pathways (RCPs), we project changes in the mean annual discharge ranging from −18% to +3%, highlighting the sensitivity of impact assessments to model and input data choices. Additionally, streamflow signatures (Q10, Q50, Q90) are projected to decline by approximately 9%, 18%, and 13%, respectively, under RCP 8.5. Annual hydropower potential is estimated to decrease by 14% and 5% under RCPs 4.5 and 8.5, respectively. These findings provide actionable insights for water management practices in the KARB, including guiding the development of adaptive strategies to optimize water allocation, mitigate risks of scarcity, and support sustainable agricultural and industrial activities in the region.

Results suggest that the Grand Inga project will be resilient to negative climate impacts during its initial phases (1-5). The system demonstrates security and insensitivity to adverse changes, both for existing (Phase 1-2) and planned (Phase 3-5) hydropower components. The study indicates that climate change effects become apparent only in later phases (6-8), with predominantly positive impacts, potentially increasing the generation potential of the hydropower system. Overall, the Grand Inga hydropower project appears robust against adverse climate influences throughout the majority of its development phases.

This study assesses the impact of climate change on streamflow characteristics in the Lualaba River Basin (LRB), an important yet ungauged watershed in the Congo River Basin. Two conceptual hydrological models, HBV-MTL and GR4J, were calibrated using the reanalysis datasets and outputs of Generalized Circulation Models (GCMs) under CMIP6 during the historical period. The hydrological models were fed with outputs of GCMs under shared socioeconomic pathways (SSPs) 2-45 and 5-85, moderate- and high-radiative future scenarios. The results demonstrate that hydrological models successfully simulate observed streamflow, but their performance varies significantly with the choice of climate data and model structure. Interannual streamflow (Q) percentiles (10, 50, 90) were used to describe flow conditions under future climate. Q10 is projected to increase by 33% under SSP2-45 and 44% under SSP5-85, suggesting higher flow conditions that are exceeded 90% of the time. Q50 is also expected to rise by almost the same rate. However, a considerably higher Q90 is projected to increase by 56% under the moderate- and 80% under the high-radiative scenario. These indicate the overall higher water availability in this watershed to be used for energy and food production and the need for flood risk management.

The Congo River Basin is the second-largest watershed globally, flowing through nine countries before reaching the Atlantic Ocean. The Kasai River Basin (KARB), containing about one-fourth of Congo’s freshwater resources, plays a strategic role in sustaining navigation, food production, and hydroelectricity generation in Central Africa. A multi-model framework suited for data scarce regions is applied for climate change impacts on water availability in the KARB to propose effective development plans in the future. This includes consideration of two conceptual hydrological models calibrated using four reanalysis datasets and fed with bias-corrected outputs of 19 climate models under two future Representative Climate Pathways (RCPs). Changes in mean annual discharge in the KARB from -18% to +3% are projected depending on the considered modeling configuration. This shows the sensitivity of impact assessment to the choice of models as well as input data. Moreover, about 9%, 18%, and 13% decline in streamflow signatures (Q10, Q50 and Q90) are projected based on the ensemble of models under RCP 8.5. A decrease of 14% and 5% in annual hydropower potential of the mainstream is estimated under RCPs 4.5 and 8.5, respectively. These changes in flows conditions should be considered in decision-making around constructing reservoirs and hydroelectricity generation.

In regions characterized by continuous permafrost, hydrological modeling remains a complex activity, primarily due to constraints related to the prevailing climatic conditions and the specific behavior of the active layer. High-latitude regions receive less solar radiation; thus, most creeks are active only during summertime and stay frozen in the winter. To realistically simulate watersheds underlain by continuous permafrost, the heat transfer through the soil needs to be accounted for in the modeling process. In this study, a watershed located in a continuous permafrost zone in Russia is investigated. A model is proposed to integrate this heat transfer into an existing conceptual rain-flow transformation model, Hydrologiska Byråns Vattenbalansavdelning (HBV), to calculate the seasonal thaw depth and determine the components of water balance. The proposed integration is a novelty compared to the standard model, as it enables the physical and thermal properties of the soil to be taken into account. It was found that the proposed model, HBV-Heat, performs better than the stand-alone HBV model. Specifically, the average Nash–Sutcliffe efficiency (NSE) increases by 30% for the whole calibration period. In terms of the water balance components, the results are consistent with previous studies, showing that surface runoff represents 64% of the observed precipitation.

The present paper proposes an iterative implicit numerical method for simulating the thaw depth of permafrost soil. For this purpose, the enthalpy-porosity model was used for the phase change process, and the finite difference scheme FTCS (Forward Time Centered Space) was used for discretization. An artificial mushy zone was maintained with the same thickness by keeping the regularization parameter proportional to the temperature gradient. In doing so, we made the scheme more stable and convergence occurred faster. The model accuracy was validated by comparing the numerical results with the analytical Stefan solution and with the results of a derived numerical model, based on an explicit scheme. The model performance was also tested against observation data collected on four different landscapes with different soil profiles and located on a basin underlain by continuous permafrost. It was found that the proposed model matched noticeably well the analytical solution for a volumetric liquid fraction (phi) equal to 0.5 regardless of the grid resolution. Furthermore, compared with the observation data, the model reproduced the annual maximum thaw depth with an absolute error lying between 0.7 and 7.7%. In addition, the designed algorithm allowed the model to converge after a maximum of eight iterations, reducing the computational time by around 75% compared to the explicit model. The results were so encouraging that the model can be included in a hydrological modeling of permafrost watersheds or cold regions in general.

First, the Authors are to be congratulated on their paper, in which the depressurization process in a drainage system has been analysed experimentally and numerically. The drainage system contains ...

This paper studies the air pressurization problem caused by a partially pressurized transient flow in a reservoir-pipe system. The purpose of this study is to analyze the performance of the rigid column model in predicting the attenuation of the air pressure distribution. In this regard, an analytic formula for the amplitude and frequency will be derived, in which the influential parameters, particularly, the driving pressure and the air and water lengths, on the damping can be seen. The direct effect of the driving pressure and inverse effect of the product of the air and water lengths on the damping will be numerically examined. In addition, these numerical observations will be examined by solving different test cases and by comparing to available experimental data to show that the rigid column model is able to predict the damping. However, due to simplified assumptions associated with the rigid column model, the energy dissipation, as well as the damping, is underestimated. In this regard, using the backward Euler implicit time integration scheme, instead of the classical fourth order explicit Runge–Kutta scheme, will be proposed so that the numerical dissipation of the backward Euler implicit scheme represents the physical dissipation. In addition, a formula will be derived to calculate the appropriate time step size, by which the dissipation of the heat transfer can be compensated.