Abstract
This study aims to evaluate longitudinal trends of flow regime and the degrees of its alteration by dams and weirs in Sagami River focusing on the major confluence. We simulated river flow and then evaluated flow regimes statistically under three scenarios. As a result, significant alterations by dams and weirs on the natural flow were detected particularly on the median flows, minimum flow, low pulse duration as increments, and high pulse count as decrement. The magnitudes of discharge, the numbers of high and low pulses, and the rate of change were amplified strongly at the confluence in the scenarios assuming natural tributary, indicating that tributaries have potentials to mitigate the altered flow regime. The release from a dam on the tributary mitigated the alteration on the mainstream more positively than the natural tributary in several aspects, though the tributary streamflow was distorted. Overall, our results contribute to shape an integrated operation scheme of dams within a stream network for the conservation of flow regime in rivers.
