ORIGINAL PAPER Rainfall irregularity and its impact on the sediment yield in Wadi Sebdou watershed, Algeria Abdesselam Megnounif 1 & Abderrahmane Nekkache Ghenim 1 Received: 22 June 2015 /Accepted: 18 December 2015 # Saudi Society for Geosciences 2016 Abstract The impact of changes in rainfall can be studied by means of the sediment transport in the rivers. The link be- tween rainfall irregularity and sediment rating parameters was investigated in the Wadi Sebdou watershed of 256 km 2 located in northwest Algeria. The data set includes rainfall records and cover the period from September 1939 to August 2009. Hydrometric records consist of instantaneous measurements flow discharge, Q, and suspended sediment concentration, C, based on a monitoring program from September 1973 to August 2003. In neighboring gauging sta- tions, the periods of record were either short or discontinuous and may not be representative to assess the potential causes of the suspended-sediment changes. The time evolution of sedi- ment rating parameters was used to improve understanding of the interaction between sediment delivery supplied from inter- nal and external sources to the wadi channel. Our findings indicate that the rating parameters varied by many orders of magnitude, suggesting significant temporal change in both potential of sediment yield and sediment sources. High b- parameter (≅1.12) and low a-parameter values (≅0.018) were observed during the time interval of change from wet to dry period occurred in the mid of 1970s. The growth of vegetation and the well-developed organic soil horizons have reduced runoff and prevented particle detachment and transport. So, the functioning of sediment sources external to the channel was comparable to that of temperate regions. After that tran- sition, the prolonged dryness has led to a higher risk of desert- ification and critical soil erosion. Therefore, the functioning of sediment sources external to the wadi-flow becomes similar to that observed in arid river systems, while the fluctuation of sediment contribution supplied from hydrographic network suggests a watershed functioning as semi-arid streams. The watershed ability to sediment yield was high toward the mid of the dry period and sediment delivery supplied from sources both internal and external to the wadi channel was copious suggesting a large amount of stored sediment at the beginning of a runoff season and an increased transport capacity of the river. Keywords Sedimentload . Sediment ratingcurve . Semiarid . Water discharge . Wadi Sebdou . Algeria Introduction, terminology, and literature review The amount of suspended sediment transported by a stream is supplied from both external and internal sources to the stream channel. Internal sources include material attributed to weathering of bed material or gullies, while external sources include surface erosion on slopes (Guy 1978). Thus, rivers confer a major role as a key pathway of material transfer on Earth connecting land to the ocean (Gregor 1970). Many is- sues concern sediment transfer since they act as a vector for a wide variety of organic and inorganic chemical constituents (Ludwig and Probst 1998; Syvitski et al. 2003; Horowitz 2008). Suspended sediment dynamic has important influences on physical and biological processes in watershed systems such as the denudation of the continents, reservoir sedimenta- tion, channel, estuary and harbor silting, as well as the func- tioning of coastal ecosystems and the evolution of deltas * Abdesselam Megnounif megnounif_aslam@yahoo.fr Abderrahmane Nekkache Ghenim anghenim@yahoo.fr 1 BEau et Ouvrage dans Leur Environnement^ Laboratory, Tlemcen University, BP 230, Tlemcen 13000, Algeria Arab J Geosci (2016) 9:267 DOI 10.1007/s12517-015-2280-y