water Article Analysis of the Spatiotemporal Annual Rainfall Variability in the Wadi Cheliff Basin (Algeria) over the Period 1970 to 2018 Mohammed Achite 1,2 , Tommaso Caloiero 3 , Andrzej Wal˛ ega 4, * , Nir Krakauer 5 and Tarek Hartani 6   Citation: Achite, M.; Caloiero, T.; Wal ˛ ega, A.; Krakauer, N.; Hartani, T. Analysis of the Spatiotemporal Annual Rainfall Variability in the Wadi Cheliff Basin (Algeria) over the Period 1970 to 2018. Water 2021, 13, 1477. https://doi.org/10.3390/ w13111477 Academic Editor: Matthew Therrell Received: 2 May 2021 Accepted: 22 May 2021 Published: 25 May 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Faculty of Nature and Life Sciences, Laboratory of Water & Environment, University Hassiba Benboual of Chlef, Chlef 02180, Algeria; m.achite@univ-chlef.dz 2 National Higher School of Agronomy, ENSA, Hassan Badi 16200, El Harrach, Algiers 16004, Algeria 3 National Research Council-Institute for Agricultural and Forest Systems in Mediterranean (CNR-ISAFOM), 87036 Rende, Italy; tommaso.caloiero@cnr.it 4 Department of Sanitary Engineering and Water Management, University of Agriculture in Krakow, Mickiewicza 24/28 Street, 30-059 Krakow, Poland 5 Department of Civil Engineering and NOAA-CREST, The City College of New York, New York, NY 10031, USA; nkrakauer@ccny.cuny.edu 6 Laboratory Management and Valorization of Agricultural and Aquatic Ecosystems, Morsli Abdellah Tipaza University Center, Oued Merzoug, Tipaza 42000, Algeria; rik_hartani@yahoo.fr * Correspondence: andrzej.walega@urk.edu.pl Abstract: In the context of climate variability and hydrological extremes, especially in arid and semi-arid zones, the issue of natural risks and more particularly the risks related to rainfall is a topical subject in Algeria and worldwide. In this direction, the spatiotemporal variability of precipitation in the Wadi Cheliff basin (Algeria) has been evaluated by means of annual time series of precipitation observed on 150 rain gauges in the period 1970–2018. First, in order to identify the natural year-to- year variability of precipitation, for each series, the coefficient of variation (CV) has been evaluated and spatially distributed. Then, the precipitation trend at annual scale has been analyzed using two nonparametric tests. Finally, the presence of possible change points in the data has been investigated. The results showed an inverse spatial pattern between CV and the annual rainfall, with a spatial gradient between the southern and the northern sides of the basin. Results of the trend analysis evidenced a marked negative trend of the annual rainfall (22% of the rain gauges for a significant level equal to 95%) involving mainly the northern and the western-central area of the basin. Finally, possible change points have been identified between 1980 and 1985. Keywords: precipitation; climate change; Sen’s estimator; Mann-Kendall; Wadi Cheliff basin 1. Introduction The Mediterranean basin is climatically affected by the interaction between mid- latitude and tropical processes, being located in a transition zone between the arid climate of North Africa and the temperate and rainy climate of Europe. For this reason, it is considered a major hotspot of climate change, subject to strong warming and drying, with increasing consequences on spatial and temporal precipitation distribution [1]. Within this context, spatial and temporal precipitation analyses with different methodologies has been recently performed in the Mediterranean basin [2] and, especially, in Northern Africa [3]. The majority of these studies were principally based on non-parametric tests, which are better suited than parametric ones to deal with non-normally distributed data in hydrometeorology [4]. In particular, different results have been obtained between the eastern and western side of the region. In effect, the west-central part is characterized by a negative rainfall trend [5], albeit irregular and high variable across the decades. By contrast, the eastern side presents positive rainfall tendencies in some areas [6,7], and negative trends in others such as Israel [8,9]. In the Middle East and North Africa (MENA) region, which includes North Africa, Donat et al. [10] detected an opposite behavior in the period Water 2021, 13, 1477. https://doi.org/10.3390/w13111477 https://www.mdpi.com/journal/water