Authors : Revodius Bishanga Stanslaus; Edmund Mutayoba; Livingstone Swilla

Volume/Issue : Volume 11 - 2026, Issue 5 - May

Google Scholar : https://tinyurl.com/349svcnu

Scribd : https://tinyurl.com/4p48nsdz

DOI : https://doi.org/10.38124/ijisrt/26May357

Note : A published paper may take 4-5 working days from the publication date to appear in PlumX Metrics, Semantic Scholar, and ResearchGate.

Abstract : Reliable forecasting of reservoir inflows and accurate prediction of flood events are crucial for ensuring dam safety and maintaining water supply reliability. This study assesses the adequacy of the spillway at Mindu Dam, located in Morogoro, Tanzania, by combining hydrological modelling with a performance-based assessment. A rainfall–runoff model was developed using the HEC-HMS platform. It was calibrated using basin-average precipitation from the Mondo, Hobwe and Mlali rainfall stations and observed discharge data from the Konga gauging station on the Ngerengere River. The model was validated from 2005 to 2019 to ensure it represents catchment hydrological processes well. Model performance was evaluated using statistical indicators, including the Nash–Sutcliffe Efficiency (NSE), the coefficient of determination (R²), and Percent Bias (PBIAS). The results show model performance. During calibration, NSE was 0.72 and R² was 0.76, while during validation NSE was 0.68 and R² was 0.71. These values demonstrate agreement between simulated and observed flows, confirming the model’s suitability for analysis in the study area. Simulated flood hydrographs were used to estimate peak inflows and to assess the spillway’s capacity to safely convey flood events. The analysis reveals that the existing spillway performs under moderate flood conditions but may be insufficient during flood scenarios. This limitation introduces a risk of overtopping, particularly under conditions of increased variability and uncertainty. The findings highlight the importance of integrating modelling with hydraulic design and evaluation in dam safety assessments. In the context of climate change, which brings increasing rainfall intensity and event frequency, such integrated approaches are essential. They help develop infrastructure and inform adaptive water resources management strategies. The Mindu Dam spillway assessment shows that combining modelling with performance-based evaluation can identify potential risks and inform strategies to mitigate them, ensuring dam safety.

Keywords : Rainfall–Runoff Modelling; HEC-HMS; Spillway Adequacy; Flood Hydrograph; Dam Safety; Peak Discharge.

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