Flow Duration Curve a Tool for Assessing the Intensity and Seasonal Patterns of Low-Flow Periods: Case Study of Tassaout River Basin Within the Upstream of Moulay Youssef Dam (1978–2016) (Morocco)

Flow duration curve combines in one curve the flow characteristics of a stream throughout the range of discharge. It can also facilitate the assessment of both the severity and seasonal fluctuations of low-flow periods. This curve offers a valuable tool for comprehensively understanding the dynamics of water scarcity over time. The purpose of this study is to evaluate the intensity and seasonal patterns of low flow in the Tassaout River basin, upstream of the Moulay Youssef dam. This basin experiences a semi-arid climate characterized by limited rainfall. Furthermore, alongside the constrained distribution of water resources, the region faces growing demands due to ongoing climate change. Low-flow events are recurrent on a seasonal basis, and their severity can be influenced by annual variations in rainfall. This article aims to contribute to the examination of low-flow period severity and seasonality through the analysis of recorded water deficits during these periods. For this purpose, the Sequent Peak Algorithm (SPA) method was employed to extract water deficit volumes. The low-flow threshold was determined using the Q75 indicator derived from the flow duration curve, which was constructed from daily discharge data collected at the Ait Tamlil and Tamsemat gauging stations, spanning the period from 1978 to 2016.