Assessing the potential impacts of dam operation on daily flow at ungauged river reaches

Abstract

Study Region: The study region is the Southern Quebec river network. Dataset on dams as well as daily flow recorded at stations were used. Study Focus: Dam construction and operation can have significant impacts on hydrological regimes. If dam construction induces some basic alterations to basin hydrology, dam operation can introduce dynamic alterations in streamflow. Assessing the impacts of dam operation can be crucial for many applications where recorded flow series are used as a proxy for flow at nearby ungauged basins in regional flood frequency analysis or for hydrological modelling. The potential influence of dam operation on recorded flows was assessed through statistical testing that verified the unimodality of the daily flow distribution. The Degree of Regulation (DOR) index was then used to relate the potential influences of dam operation to basic physiographic and dam characteristics. New Hydrological Insights for the Region: Application of a unimodality test to daily flow series recorded at stations located in the study region confirms that dam operation can result in non-unimodal daily flow distribution. Estimation of DOR values for all reaches of the study region shows that regulated river reaches could be potentially influenced by dam operation when DOR > 8. Of the 29% regulated river reaches (i.e. with one or more upstream dams), approximately 30% could be potentially influenced (DOR > 8) by dam operation. Keywords: Dam operation, Daily flow distribution, Unimodality, Degree of regulation index, Southern Quebec