The human influence on the river ecosystem has increased in recent years to feed the growing demand for water to communities by constructing different water structures. It is essential to understand the potential impacts of water structures on river hydrologic regimes. Thus, this study investigates the influence of the cascade dams located upstream of the Three Gorges Dam on the Yangtze River on the river ecosystem. The study was carried out for the period 2003–2015 for both Cuntan and Miaohe stations. The analysis was conducted considering two periods, pre-impact; before the dam construction and post-impact; after the dam construction. The assessment was carried out using “Indicators of Hydrologic Alteration.” The results of this study revealed that the cascade dams built upstream of Three Gorges Dam has both positive and negative impacts at both stations. Flows were found to have positive impacts in July while low in October for both stations. The 1-day minimum flows were found to decrease by 7% over Miaohe Station while the 1-day maximum was decreased up to 2% in Cuntan. Overall, the results of the study indicate that there are undesirable impacts which should be adjusted to maintain the river ecosystem at an acceptable level compared to its natural state. It is expected that the findings of the study can guide water managers to adjust the hydropower operation sustainably.
Hydrologic Alteration Associated with Dam Construction in a Medium-Sized Coastal Watershed of Southeast China