Hydrological Regime Variability between the Tien and Hau Rivers under the Impact of Anthropogenic Activities and Climate Change

The distribution of flow discharge between the Tien and Hau Rivers in the Vietnamese Mekong Delta (VMD) plays an important role in Vietnam’s agricultural and aquaculture production activities. However, recent variations in water levels and flow patterns, driven by both human activities and climate change (CC), have posed significant challenges for water resource management. This study evaluates the impacts of unsustainable exploitation and CC on the hydrological regime of the Tien and Hau Rivers using non-parametric statistical methods. Long-term water level data (1978–2023) from Tan Chau, Chau Doc, and Vam Nao observation stations were analyzed using the Mann-Kendall test (MK), Sen’s Slope (SS) estimator, and Pettitt’s test to detect trends, quantify change magnitudes, and identify abrupt shifts. The results indicate a significant decline in flood-season water levels, with annual decrease rates ranging from 41.5 to 72.9 mm in September and November. Conversely, a slight increasing trend in water levels was observed in the dry season (DS) during the studied time. Additionally, findings reveal that the upstream Tien River exerts greater control over the hydrological regime in the Vam Nao River. These insights contribute to disaster risk assessment, sustainable water resource planning, and ecological risk evaluation. Furthermore, the results contribute to providing a foundation for applying hydrological and hydraulic models to forecast hydrodynamics, thereby supporting effective water management strategies and mitigating flood and dry risks in the VMD.