nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand

EVALUATION OF THE SALINITY OF GROUNDWATER USED FOR IRRIGATION AND RISKS OF SOIL DEGRADATION: CASE STUDY OF THE ISSEN PERIMETER IN THE SOUSS-MASSA,

Kaoutar EL OUMLOUKI1,2*, Rachid MOUSSADEK2, Ahmed DOUAIK2,Hamza IAAICH2, Houria DAKAK2, Mohamed Taoufiq CHATI 3, Ahmed GHANIMI4, Azzedine El MIDAOUI1,Mahacine EL AMRANI1, Abdelmjid ZOUAHRI2

ABSTRACT

In the Issen irrigated perimeter from Souss-Massa, under a semi-arid climate, irrigation is essential for most crops. Therefore, groundwater is being increasingly used. Hydro-chemical and statistical studies have been conducted to find the major and secondary elements of the ground waters. Sampling was done over two years (2013 and 2014) spread over three seasons from thirty six wells spread across the studied plain. The values recorded during the sampling period showed that the majority of analyzed wells are highly saline with an average salinity of 2 dS/m. Chemical analyses reveal a wide variety of chemical compositions; samples are divided between two facies: Sulfated calcium and Magnesian facies and sodic chlorinated facies. Then, statistical analyses of the studied parameters show great variability and the results of analyses were used to establish maps of salinity and SAR risk of irrigation water.

Keywords: Morocco, hydrochemistry, statistics, irrigation, salinization, Issen irrigated perimeter.

1. INTRODUCTION

Agriculture represents 15% of Gross Domestic Product (GDP) of Morocco where 93% of the total area is arid, making irrigation indispensable for growing crops (Debbarh and Badraoui, 2003). In countries with arid and semi-arid climate, irrigation with salty waters can cause the fixing of sodium by the soil adsorbent complex and causes an increase in the concentration of soluble salts in shallow horizons and disrupt crop development (Essington, 2004; Zouahri et al, 2015). They deeply transform the physical and chemical properties of soil (Lambers, 2003) and when the salt concentrations exceed a certain threshold, they cause a significant drop in crop yields and a tendency to the dispersion of clays, the degradation of the structure, the loss of permeability and the asphyxia of plants (Katerji et al., 2003; Asgari et al, 2012). The intensity of the salinization process is not only due to climatic conditions, but also to the human activity which, for economic reasons, has developed an often uncontrolled and intensive agriculture that depends on the soil characteristics that we want to

1 Ibn Tofail University, Faculty of Sciences, Department of Chemistry, Laboratory of Processes and Separation, PO Box 133, 14000 Kenitra, Morocco; E-mail:[email protected]; E-mail: [email protected]; E-mail: [email protected] 2 National Institute of Agricultural Research, Regional Center of Rabat, (INRA),CRRAR, Research Unit on Environment and Conservation of Natural Resources, PO Box 6356, 10101 Rabat, Morocco. E-mail:[email protected]; E-mail:[email protected]; E-mail:[email protected]; E-mail:[email protected]; E-mail:[email protected]; E-mail:[email protected] 3 Ministry of Agriculture and Fisheries, Direction of Irrigation and Development of Agricultural Land, Service of Monitoring and Market Regulation, PO Box 1069, Rabat, Morocco: E-mail:[email protected] 4 Mohamed V University, Faculty of Sciences, Department of Chemistry, Avenue Ibn Battouta, PO Box 1014, Rabat, Morocco. E-mail:[email protected]

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nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand irrigate, the water quality, the conditions of their employment and particularly the efficiency of the drainage system (Dakak et al., 2014). However these irrigation practices increase the risk of salinization in Morocco since about 160 000 ha (16%) of irrigated land are already affected by salinisation to varying degrees (Badraoui, 2006).

The Issen perimeter of the Souss-Massa plain is characterized by semi-arid climate with high evapotranspiration and high salinity of groundwater. Drought and scarce rains have forced farmers to irrigate with brackish waters. Continuous use of such waters can have adverse effects on soil quality. The objective of this work is the evaluation of the quality of the groundwater used in irrigation and possible risks of degradation of soil of the Issen perimeter and to identify possible origins of salinity.

2. METHODS

2.1 Presentation of the study area

2.1.1 Geographic location

The Souss-Massa region is located in the geographical center of Morocco; it is limited by the Atlantic Ocean to the West, the mountains of the High-Atlas to the East and the Anti-Atlas to the South. Three watersheds characterize the water system of the region: Oued Souss, Massa-Chtouka, and the watershed of Tamraght and rivers. This region covers a total area of 23 950 km2 with 13 000 ha for the Issen perimeter, our study area. The latter is composed of two areas: the modern Issen irrigated perimeter (Issen left bank) and the traditional Issen irrigated perimeter (Issen right bank) belonging administratively to the two provinces of and Taroudant and three communes (Issen and Eddir from the Province of Taroudant and Amskroud from the Province of Agadir), it is comes under the Regional Office of Agricultural Development of Souss-Massa (the ORMVASM) by the subdivision Oulad Teima and CMV 803 (Figure. 1; Buchs, 2012).

Figure 1. Presentation of the Issen perimeter from the Sous-Massa region.

2.1.2 Geology

The Issen perimeter is part of the Souss plain which is located in the South Atlas groove belonging to the domain of the plains separating the Haut-Atlas and the Anti- Atlas Mountains. It was formed during the orogenic phases of Neogene and Quaternary. It is occupied by Cenozoic land represented by limestone and sub-

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nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand horizontal clastic spreadings from the Plio-quaternary which forms the Souss plain. Structurally, the Souss plain is a narrow steep-sided rift zone between the High-Atlas and the Anti-Atlas. Clastic and calcareous marl formations of Plio-quaternary filling cover the Cretaceous-Eocene East-West oriented syncline. The northern flank of this syncline flushes widely but discontinuously, along the High-Atlas. Its southern side is characterized by a line of hills formed by Turonian limestone in the axis of the Souss plain. At Oued Issen, the Permo-Triassic clastic-dominant is represented by conglomerates, sandstones, sandstone clays, and red marl (1000 m thick), this basal succession is topped by gypsiferous and salt-bearing clays of 500 m of thickness (Hssaisoune et al, 2012).

2.1.3 Climate

The climate of the Souss plain is arid and experiences low rainfall, high temperatures, and strong evaporation during about 10 months/year. In January, the weather is cold with a monthly average temperature of 16.3 °C and an average minimum of 1.1 °C. July and August are the hottest months with monthly average temperatures of 27 °C and 27.1 °C. The average maxima of those months are 43.3 and 40.0 °C, respectively. December and January are the wettest months with rainfall of approximately 37% of the annual precipitation. May, June, July, August and September are the driest months with rainfall below 4.7 mm.

2.1.4 Water resources

2.1.4.1 Surface water resources

The Issen perimeter began to be irrigated in 1986-1987 and is fed from the Dkhila diversion dam whose waters come from Abdelmoumen dam located 27 km upstream. It is composed of a sprinkler modern sector of 8.560 ha, which is equipped with pressurized dispensing systems supplying irrigation terminals and another traditional gravity sector of 4.440 ha which is supplied by self-supported channels. This perimeter has an annual water budget of 65 million m3, of which 54 million m3 for the sprinkler modern sector (Baroud, 2002).

2.1.4.2 Groundwater resources

At the Issen perimeter, the groundwater is the most exploited. Presently available at depths of 25-50 m, but can decline to 120 m in some places due to overexploitation to support agricultural activities, under severe conditions of water stress and with a continuous waste of water resources. The importance of irrigation by groundwater to supplement irrigation water needs of crops mainly depends on the salinity of the water and the ability of farmers to equip and operate their wells.

2.1.5 Land use

The dominant crops in this perimeter are arboriculture (olive and citrus fruit), cereal crops (wheat) and market gardening (squash and gourd).

2.2 Sampling and analysis

A sampling network of 36 water points was chosen to allow acquiring representative data on the spatial variability of groundwater quality in the study area. The sampling was done three times: in March and May 2013, and April 2014. The sampling is based on a well-developed mesh using a topographical map of 1/50000 of the study area and a GPS (Figure.2).

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nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand

Figure 2. Location of the groundwater sampling sites from the Issen perimeter

2.3 Statistical analysis and mapping

The statistical parameters (minimum, maximum, and average) were determined for the 11 observed and calculated water quality parameters (EC, Ca2+, pH, Mg2+, Na+, + - 2- - 2- K , Cl , SO4 , HCO3 , CO3 , and turbidity) of the 36 samples. These statistical computations were performed using the SAS software (SAS, 2000). Then, thematic maps of salinity and SAR were established using the ArcGIS Geographical Information System (GIS) software Version 9.3.

3. RESULTS AND DISCUSSION

3.1 Descriptive statistical parameters

The main descriptive statistics of the quality parameters of the analyzed water (EC, pH, cations and anions, turbidity, and SAR) are graphically illustrated in the figure 3. These parameters are highly variability of the constituents in the different samples. The high constituent is the turbidity with the 130 (NTU) and 39% of these groundwater analyzed are slightly disorders, there is the content of insoluble materials (solid particles, colloidal particles, bacteria, micro-algae), it’s influence on the irrigation of crops, it can generate a clogging of irrigation systems, more particularly the systems drop by drop (Grasso,2011), the second parameters are the Cl and Na Respectively to 37 meq/l and 33 meq/l, and Many other constituents (Ca Mg,) values ranging between the (26 and 21 meq/l).

The maximum EC value is 5190 μS/cm whereas, the criteria of EC for irrigation water as suggested in literature (Khan, 1997) that the EC of water < 2 mS/cm is excellent for irrigation and crops production. Whereas, 4.0 mS/cm shows adverse effects on the health of the crops as less water is available to plants, which lead to the physiological drought (Hassan, 1999) and the pH of ground water ranged from 6.55 to 8.25.

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nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand

Figure 3. Descriptive statistics of water quality parameters

3.2 Salinity classes and map

Based on the average value of the EC (2.02 dS/m) in figure 4 and from Table 1, irrigation water is highly saline and normally not suitable for irrigation, the latter is due to the very dry climatic conditions producing high evaporation, which concentrates the soil solution (Cheverry and Robert, 1998). With this level of salinity, there is a strong negative effect on the availability of water for the plant (Ayers and Westcot, 1985).

Table 1. Salinity classes of irrigation water of the Issen perimeter following the USSL norms (1954)

Water quality Salinity class EC (dS/m) Number of wells % of wells

Non saline C1 EC<0,25 0 0

Averagely saline C2 0,25≤EC<0,75 0 0

Highly saline C3 0,75≤EC<2,25 22 61

Very highly saline C4 2,25≤EC<5 13 36

Extremely saline C5 EC>5 1 3

The map shown in Figure 4 shows the spatial distribution of the water salinity of the analyzed wells. This map shows that the majority of these wells have high salinity especially at traditional Issen perimeter next to the Issen River. This can be explained by the presence of Triassic evaporites which are the origin of the anomaly of the salinity of the Souss water table at Issen (Boutaleb et al., 2000; Hsissou et al., 2002; Bouchaou et al. 2008).

3.3 Alkalinity classes and map

The alkalinity of irrigation water is evaluated using the SAR. The higher the SAR is, the higher the water presents a risk of soil sodality due to the exchange that will operate in the balance between Na+ in soil solution and Ca2+/Mg2+ of the absorbent complex. Sodium acts on the DE flocculation of the clay soil resulting in a decrease in the macro porosity (air) and the infiltration rate of water (Arveti et al.2011).

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nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand

Figure 4. Spatial map of salinity of irrigation water of the Issen perimeter

The higher the salinity is, the higher the SAR could cause infiltration problems. However, lower the salinity is, and infiltration problems will bein dependent of the SAR value.

Table 2 and Figure 5 show that the majority of analyzed wells have low alkali.

Table 2. Alkalinity classes (SAR) of irrigation water of the Issen perimeter following the USSL norms (1954)

Alkalinity Number of Water quality SAR (mole ½.l-1/2) % of wells class wells

Non alkaline S1 <10 35 97

Slightly alkaline S2 10-18 1 3

Highly Alkaline S3 18-26 0 0

Very highly alkaline S4 26-32 0 0

Figure 5. Spatial map of alkalinity (SAR) of irrigation water of the Issen perimeter.

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nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand

3.4 Combined salinity and alkalinity classes

To understand the relation between salinization and alkalization, we use the American classification chart (USSL, 1954) (Figure.6) that allows the allocation of each water quality in terms of the risk of salinization and alkalization when this water is used for irrigation. Note the dominance of four classes of water quality: C4S3, C4S2, C4S1, and C3S1. It follows that irrigation water of the Issen perimeter has a high risk of salinization and low to medium risk of alkalization (Table 3).

Figure 6. Compiled diagram of salinity and alkalinity of irrigation water of the Issen perimeter.

Table 3. Salinity and alkalinity classes of irrigation water of the Issen perimeter

Class of salinity (C) Number % of Water quality Interpretation and alkalinity (S) of wells wells class Has used that in exceptional C4S3 5 14 circumstances

To use, with great caution that in light soils and well drained and for of C4S2 2 5 Poor quality resistant plants. High risk. Leaching and contribution of gypses indispensable.

Exclude the sensitive plants and heavy soils. C4S1 6 17 Quality at Fair Usable with many precautions in light or Poor soils, well drained with dose of leaching and /or inputs of gypses

Average Has used with caution. Requires C3S1 23 64 quality to drainage with dose of leaching and/or poor contribution of gypsum

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nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand

3.5 Geochemical facies

Another hydro chemical study is used to characterize the geochemical facies of the analyzed water using the Piper diagram. This characterization is based on the calculations of proportions concerning different cationic and anioni canalized species (Figure. 6).

The predominant cations are Na and Mg while the predominant anions are Cl and SO4. Piper trilinear diagram interpretation reveals that there is only a sodic chlorinated (Na + Cl) facies, whereas the latter it's Sulfated calcium and Magnesian (Mg + SO4). The origin of these different facies is very varied it’s can due to change in the hydro climatologically cycles; this variation is dependent on the prevalence of tributaries between traditional and modern irrigated perimeters (Boutalebet al., 2000).

The sodic chlorinated facies is very frequent in this tablecloth, there is generally the result of a concentration by dissolution or of seawater intrusion into the groundwater, and they are characterized by a high concentration of sodium ions and chlorides. The plants supporting poorly saturated soils in sodium. as well as when the concentration of chloride ions in irrigation water is higher than 4 meq/l, toxicity problems can occur, especially for sensitive crops, (Bigak and Nielsen ,1972). The sulfated facies either calcium or magnesium, very recognized in the whole perimeter studied, he may have as origin the dissolution or the concentration by evaporation in the areas of outcrop or sub-flush fitting of the tablecloths. In effect, the ions SO4 can have as origin, the dissolution of the shales pyritic or diffuse gypses in alluvia essentially of silty Soltanien whose deposits have a probable origin of clay licks Triassic of the basin of Issen

Figure 6. Piper diagram of irrigation water of the Issen perimeter

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nd 2 World Irrigation Forum (WIF2) W.3.3.13 6-8 November 2016, Chiang Mai, Thailand

CONCLUSIONS

The quality of groundwater used for irrigation was assessed in the Issen perimeter, Souss-Massa plain (south of Morocco), during the 2013-2014 period. The necessity of this research is due to the problems experienced by the region as drought and non- availability of water and the high demand for water from agricultural activities. The analysis of all parameters characterizing salinity throughout the observation period has allowed evaluating the quality of these waters by hydro chemical and statistical methods. This evaluation revealed that water has a high salinity, in particular the traditional Issen perimeter.

Various factors have led to this salinity, namely:

-The aquifer material, where it is found a heterogeneous lithology consisting mainly of Triassic and Upper Lias silt, clay, gypsiferous marl and evaporate rich in gypsum and halite, is increasing the mineralization of waters of the Issen River towards the Abdelmoumen dam.

(a) The climatic conditions characterized by low rainfall and high temperatures which prevail during the summer are the cause of a significant evapotranspiration responsible for an increase in salinity. (b) Changes in hydro climatological cycles: this variation is dependent on the prevalence of tributaries between traditional and modern irrigated perimeters.

According to the relationship between the SAR and salinity, irrigation water of the Issen perimeter has a high risk of salinization and a low to medium risk of alkalization; the dominant classes in the region are C4S3, C4S2, C4S1, and C3S1.

Finally, the origin of mineralization and salinity of the analyzed water in the Issen perimeter remains difficult to determine using only ion ratios. This determination requires the appeal to isotope hydrology techniques including stable isotopes of the water molecule.

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