CLIMATE CHANGE CHARACTERIZATION IN THE SEMI-ARID ABDA PLAIN IN WESTERN CENTRAL MOROCCO

Alahiane Kamal 1,2 , El Mzouri El Houssine 2 , El Hani Sliman 3 and Koulali Yahya 1 . 1. Laboratory of Eco-design, Energy, Environment and Innovation, University Hassan 1, Faculty of Sciences and Technology, Settat, Morocco. 2. Department Of Agronomy, Regional Center for Agronomic Research, Settat, Morocco. 3. Department Of Agronomy, Regional Center for Agronomic Research, Tanger, Morocco. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

The Abda plain is part of the semi-arid areas of Morocco, which are subject to the effects of climate change. Agricultural activities are strongly affected by the repeated droughts in this part of Morocco. There is need for an agro-climatic characterization in order to better help farmers adapt. The objective of this work is to study the evolution pattern and to characterize agro-climatic tendencies in the dryland area of Abda, plain of Morocco. Results of this study show a continuous and significant decline of the total amount of rainfall received by this area, with 108 mm rainfall decrease over the last 43 years. The average Martonne index calculated during the two distinct period 1975-1996 and 1997-2017 are, respectively 13.9 and 9.4. Indeed, the Standardized Precipitation Index calculated confirm the tendency of droughts period with about 71%, the years were normal and that 29 % were moderately or severe dry years but no wet years during the last two decades. For the length of growth period, a decrease reported during the two last 20 years with a decline from 192 days during the first period to only 138 days during the second period. The year 1996 is the break point for all calculated average indices. In conclusion, this work shows that the rainfall pattern in the dryland area of Abda, plain of Morocco is decreasing with erratic rainfall, high frequencies of severe droughts and reduced crop growth period.

…………………………………………………………………………………………………….... Introduction:-
Climate change and its impact on agriculture is one of the greatest challenges facing humanity in the 21 st century. Morocco by its geographical position dominated by the semi-arid bioclimatic zones (more than 85 % of cultivated areas) has shown signs of climate variability during the last decades (Huebener and Kerschgens, 2007). The extension of dry periods became a reality in this part of the globe. Indeed, many investigators reported high frequencies of severe droughts (Sebbar and al., 2012;Sebbar and al., 2011;Meddi, 2009). These droughts are affecting agricultural productivity, activities and sustainability in the dryland semi-arid areas of Morocco. The objective of this work is to study the evolution pattern and to characterize agro-climatic tendencies in the dryland area of Abda, plain of Morocco.

Materials and Methods:-
The area covered by this study (Fig.1) is located at the western Morocco (Latitude 32° 17' 57, Longitude -9° 14' 13). Its climate a Mediterranean climate with hot and dry summers and cold and rainy winters. The agricultural activities are dominated by rain-fed small grain production (wheat and barley) associated with mixed animal husbandry (sheep and cattle).
The climate data (daily rainfall and temperatures were provided by the National Department of Meteorology (DMN). These data covered the period from 1975 to 2017 for Jemâa Shaïm climatic station. The variables generated from this database are: -Annual rainfall evolution -Martonne Index (I) -Standardized Precipitation Index (SPI) -Length of growth period (LGP) Figure 1:-Localization of study area (in green), Safi province, Morocco Rainfall evolution:-The interannual rainfall evolution were calculated by a yearly data series during the period between 1975 and 2017. These data have been organized, processed and analyzed by using no-parametric Pettit method, Bayesian method of Lee and Heghinian, and the segmentation of Hubert (Lubès and al., 1994). We used the statistical software: Khronostat (1998) developed by the Institute of Research for Development (Lubes-Niel and al., 1998), to analyze the time series and to characterize the evolution, ruptures and the extreme events marked the study area during the period.

Martonne Index:-
The annual aridity index allows you to define the type of climate of a given area based on the data of rainfall and thermal. This index established by De Martonne, (1923) is calculated by the following equation: I = P/ (T+10) With: P: The annual total precipitation (mm) T: The annual average temperature (°C) The interpretation of I values is as follows: • If I < 10, the climate is arid • If 10 < I <20, the climate is semi-arid • If 20 < I < 50, the climate is cold, temperate or tropical • If I > 50, the climate is equatorial or mountain Similarly, to the rainfall pattern, we used no-parametric Pettit method, Bayesian method of Lee and Heghinian, and the segmentation of Hubert (Lubès and al., 1994).   (Fig.  3). These results show a clear shift of Abda area from semi-arid climatic zone to an arid one. This trend toward more aridity was reported by Driouech, (2010) and Sebbar & al., (2012) and demonstrated that aridity is moving northward in Morocco during the last 30 years.  (Fig. 4). In fact, during the period 1975-1996, Abda area had 63% of the years that were normal; 27 % were moderately or extremely wet years, and that only 10 % that were moderately or extremely dry years. However, during the second period from 1997 to 2017, about 71%, the years were normal and that 29 % were moderately or severe dry years but no wet years. Results from this study confirm what was reported by other studies in Morocco (Lachgar and al., 2016;El Bouqdaoui and al., 2006), and demonstrate that rainfall is more erratic with more and more severe droughts that leads to crop failure and loss.

Length of growth period (LGP):-
The length growth period (LGP) declined from 192 days during the period 1975-1996 to only 138 days during the period 1997-2017 (Fig. 5), confirming therefore the previous results. Indeed, with the decrease the total amount of rainfall received, and increased aridity with less favorable years, the crop canopy is facing more abiotic stresses (water and heat stresses). This significant decrease of LGP impacts negatively farm activities and farming practices and management currently adopted by local farmers. Among the practices that are the most vulnerable to this LGP changes we cite species and varieties choices, soil tillage, crop rotation, fertilizer management weed and pest management, etc… All this changes will force farmers to find ways to adapt to insure better crop production and stability and therefore more farming sustainability under the dryland semi-arid and arid areas (El Mzouri and al.,  (2), El Niño Southern Oscillation (ENSO) that carries a certain influence on the Moroccan precipitation. The warm phase (positive) of the ENSO phenomenon would lead to a reduction of spring precipitation Ward and al., 1999).

Conclusion:-
The characterization of the agro-climatic conditions in the dryland area of Abda, Morocco shows a continuous and significant decline of the total amount of rainfall received by this area, with 108 mm rainfall decrease over the last 43 years. The year 1996 is the break point for all calculated average indices. Indeed, before 1996 the Martonne index and the LGP were, respectively 13.9 and 192 days but after this year both variables were respectively, 9.4 and 138 days. We concluded from this work that the rainfall pattern in the dryland area of Abda, plain of Morocco is decreasing with more erratic rainfall, more severe droughts frequencies and reduced crop growth period.