Vol.:(0123456789) 1 3 Acta Geophysica https://doi.org/10.1007/s11600-020-00466-5 RESEARCH ARTICLE - HYDROLOGY The use of hybrid methods for change points and trends detection in rainfall series of northern Algeria Bilel Zerouali 1  · Mohamed Chettih 1  · Zaki Abda 1  · Mohamed Mesbah 2  · Mohammed Djemai 3 Received: 4 February 2020 / Accepted: 29 July 2020 © Institute of Geophysics, Polish Academy of Sciences & Polish Academy of Sciences 2020 Abstract The aim of this research is to assess relatively new hybrid methods for changes points and trends detection on rainfall series: Dynamic Programming Bayesian Change Point Approach (BA), Şen’s innovative trend method (ITM) and its double (D-ITM) and triple (T-ITM) version using the multi-scale analysis of the discrete wavelet transform (DWT) as a coupling method. Three representatives rainfall stations of northern Algeria were analysed at annual scale during the period 1920–2011. Moreover, correlation and spectral analysis (CSA) was applied for periodicity analysis. The CSA indicates the dominance of interannual to multidecadal rainfall periodicity fuctuations (2-years, 5-years and 20-years) characterising long term structured processes. Moreover, an abrupt downward trend with signifcant probability was detected from the 1970s with a relatively wet period between the periods 1950–1970 and 2001–2011. The latter is observed in particular in the central and eastern stations, well-explained by the BA-DWT. The results showed that the comparison results from diferent modelling approaches found that the hybrid models (BA-DWT, ITM-DWT, D-ITM-DWT, T-ITM-DWT) often perform better than the conventional approach (BA, ITM, D-ITM, T-ITM), where the computation time is very reasonable. The analysis revealed that information stemming from discrete wavelet spectrums signifcantly increased the accuracy of the methods for detect- ing hidden change points and trends. Keywords Changes points · Trends · Hybrid methods · Discrete wavelet transform · Algeria Introduction Precipitation is the ultimate source of water resources and a key element in climate characterization at a particular loca- tion. From the beginning of the twentieth century and based on negative human impacts on environment, the character- istics of precipitation on a global level have been marked by a signifcant change on a spatial and temporal scale (Hallouz et al. 2020; Oroud 2018; Rashid and Beecham 2019; Mrad et al. 2019; Pandey et al. 2017; Almazroui et al. 2018; Santos et al. 2018; Spinoni et al. 2018; Zerouali et al. 2018; Par- tal 2017; Chakraborty et al. 2017; Rashid et al. 2015; Kisi 2015; Nourani et al. 2015; Şen 2012; Nalley et al. 2012; Meddi et al. 2010). This change in water cycle components is the greatest environmental, technological, economic and socio-political threat ever faced by humanity and the biggest challenge. This problem is one of the most discussed topics in the 5th report of the Intergovernmental Panel on Climate Change (IPCC 2014). The analysis of the precipitation evolution and trends that can be detected, there are of the greatest interest for a region, where the water resources constitute one of the key aspects of environmental management. After the birth of computer revolution in the 1960s, the hydrologic modelling took a giant leap forward (Singh 2018), where signifcant increase in hydrology and climatology research subjects in several parts of the world, are oriented towards analysis and assessment studies of trends and changes in hydrometeoro- logical parameters (Da Silva et al. 2015, 2020; Mellak and * Bilel Zerouali b.zerouali@lagh-univ.dz 1 Research Laboratory of Water Resources, Soil and Environment, Department of Civil Engineering, Faculty of Civil Engineering and Architecture, Amar Telidji University, P. O. Box 37.G, 03000 Laghouat, Algeria 2 LGBO, Laboratory, Earth Sciences Faculty, University of Science and Technology Houari Boumediene, BP 32, 16311 Bab Ezzouar, Algeria 3 LGEA, Laboratory of Geomaterials, Environment and Development, Department of Civil Engineering, Mouloud Mammeri University, BP no 10.RP, Hasnaoua, Tizi-Ouzou, Algeria