Sodization, a Threat to Coastal Irrigated Areas Case of M
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id18496187 pdfMachine by Broadgun Software - a great PDF writer! - a great PDF creator! - http://www.pdfmachine.com http://www.broadgun.com EEFebrnunaryv v20i1i0rroonnImSmSN : e0e97nn4 - 7tt45aa1 ll SScciVioleeumnne 5 Iccssueee 1 An Indian Journal Trade Science Inc. Current Research Paper ESAIJ, 5(1), 2010 [46-50] ’nasra (Morocco) Sodization, a threat to coastal irrigated areas case of M I.Idrissi Alami1, A.Rhidouani2, M.Zeraouli3, A.Haidar4, A.Echchelh*4, M.Addou1 1Laboratory of Optoelectronics and of Physical Chemistry of Materials (Faculty of Sciences Kenitra), (MOROCCO) 2Regional Laboratory of the National Office of Drinkable Water, (MOROCCO) 3Laboratory of the Agro-Pedology of the Regional Office of Agricultural Development (ROAGD), (MOROCCO) Faculty of Science BP133, 4Laboratory for Electrical Engineering and Energy System, Ibn Tofail University Kenitra, (MOROCCO) E-mail: [email protected] Received: 18th January, 2010 ; Accepted: 28th January, 2010 ABSTRACT KEYWORDS ’nasra zone which has an agricultural land area that represents 70% The M Sodium; of the total area and its agricultural production reach 12% of the national Grounds water; production is threatened by a sodization of underground waters. We know Salinity; that this water table is the only ground water source available for this Irrigation water. region. Thereby, researches that have been carried out on the field have confirmed the salinization of this water-table due to sea water intrusion and to intensive fertilization (salts) and pesticides. Sodium (Na+) is one of the most undesirable elements in irrigation water because of its negative effects and even toxic effects on sensitive crops of the region such as carrots, beans, strawberries etc. In this view, this work aims to study the spatial and temporal evolution of sodium absorption ratio (SAR), according ’nasra to campaign period of 1993 and 2008 and in different places of M region. The spatial analysis has confirmed a sodization of an area of 19,800 Ha representing 37% of the total area, between 1993 and 2008. The confor- mity of sodium concentration is compared to Moroccan and Canadian stan- dards. 2010 Trade Science Inc. - INDIA INTRODUCTION ground water resources) and to soils (soils have less than 6% of clay and more than 82% of sand[6]), the coastal ’nasra has known an increase of the area of The overexploitation of water tables affects a lot of zone of M countries, industrialized or not (Bahrain, Greece, Spain, irrigated zones that used to reach 5,766 ha in 1998 to France, Maghreb, Egypt, India, China, USA etc.). It 39,686 ha in 2005. Today, the irrigated zone is facing to causes degradation due to see water intrusion in the an important diversification of vegetable crops (pepper, case of coastal ground waters that is to say: the water potato, tomato, aubergine, watermelon, cabbage, car- …) and exotic crops (banana, strawberry, avo- table of El Jadida[1], the Souss plain, located at the east rot, turnip ’nasra …). This crop diversity is unfortunately associated of Agadir[2], M [3], Chaouia[4], the water table of cado the oasis of Fatnassa (Tunisia)[5], etc. with an over-use of fertilizers and pesticides that cause a ’nasra’s water table Thanks to assets due to water quality (plenty of nitric pollution of M [7-10]. ESAIJ, 5(1) February 2010 A.Echchelh et al. 47 Current Research Paper It is important to notice that the water table of on two criterions: the intensification of crops and the ’nasra is also confronted to other kinds of pollution M depth of the water table. due to sea water intrusion and to crop intensification, especially the sodization of ground waters. According to Peterson[11], the main problem with a big quantity of sodium is its effect on soil permeability and on water infiltration. Sodium also directly contrib- ’s total salinity and can be toxic for sensi- utes to water tive crops such as carrots, beans, strawberries, rasp- berries, onions etc[12,13]. The sodization of ground wa- ters of irrigated areas has generated a particular atten- tion at the international scale and in different region of the world like in China[14], in Pakistan[15], in Niger and in Mali[16], in Uzbekistan[17]. In this way, this work has the objective of firstly, evaluating the sodization of the ’nasra’s water table used for irrigation, and water of M secondly the study of spatial and temporal evolution of this water table. To do so, 59 wells have been observed between 1993 and 2008. Figure 1 : Localization of the 159 studied wells within the ’nasra MATERIAL AND METHOD zone of M Sampling Zone of study ’nasra is located in the west part of For the sampling, water is taking directly from the The zone of M irrigation water supply network for the wells that are the Gharb plain and is the zone where the ORMVA of equipped of pushback pumps. For those that are not the Gharb works. The area is delimited by the Atlantic equipped, the sampling is done thanks to a metallic Ocean at the west along more than 80 km, at the south ballasted container. All the samples have been prepared by the mouth of Oued Sebou and the city of Kenitra, at in flask made of polyethylene or in borosilicate glasses. the east by rural towns of Mograne, Sidi Allal Tazi and The samples have been carefully identified and stored °C, until their reception at the laboratory. Souk Tlet du Gharb and at the north by the zone of the at +4 ORMVAG of loukous. This zone is controlled by two ’nasra and Agricultural Development Centers (ADC): M Measure of SAR ’nasra is char- Sidi Mohamed Lahmar. The zone of M SAR (sodium, calcium, and magnesium are stated acterized by a superficial water table, it is surrounded in meq/L) is calculated according to the following equa- by low depth soils with a slightly stoned texture with a tion[11]: high potential of production. Sandy soils which occu- Na pied around 50% of lands are not really fertile, very SAR permeable and confronted to erosion through wind. They 2 2 Ca Mg / 2 are adapted to vegetable crops and to peanut. Hydro- is realized by flame pho- morphic soils represent 20% of lands. These soils do The dosage of sodium (Na+) not fit to arboriculture, only few vegetable crops are tometry. Calcium ions (Ca2+) and magnesium (Mg2+) grown in this kind of soils[18]. are dosed by volumetric method[19]. SAMPLING AND MEASUREMENT RESULTS AND DISCUSSIONS METHODOLOGY In order to assess the concentration of excessive Choice of wells sodium comparing to calcium cations and magnesium The choice of these wells has essentially been based of water from our wells used for irrigation, we have Environmental Science An Indian Journal ’ 48 Sodization, a threat to coastal irriga.ted areas case of M nasra (Morocco) ESAIJ, 5(1) February 2010 Current Research Paper done 59 campaigns of measurement in two different good quality i.e. diminution of (-44%) and good i.e. periods of time: 1993 and 2008. diminution of (-5%). Punctual analysis * An increase (+12%) of the percentage of wells that have a medium quality, and an increase of (+37%) for To avoid negative impact on crop behavior, the in- those who have a bad quality. ternational standards (such as: Canadian and Moroc- can) precise that the sodium absorption ratio (SAR) should be inferior to 3-4 ppm. The results related to SAR measures of waters of the years 1993 and 2008 are shown on the TABLE 1. TABLE 1 : The average level of SAR (ppm) in water of four ’nasra’s wells in 1993 and 2008. classes of M 1993 2008 Classe SAR SAR of SAR in Number Number Quality average average (ppm) of wells of wells ppm ppm 0 - 1 33 0,55 7 0,86 Very good Figure 3 : Comparison of the percentage of wells in accor- 1 - 2 19 1,35 16 1,35 Good dance to the SAR value between 1993 and 2008 2 - 3 4 2,34 11 2,55 Average We notice a sodization of 37% of the wells be- Bad and > 3 3 4,9 25 6,65 not usable tween the years 1993 and 2008. General - 1,15 - 3,76 mean Statistical analysis We have plotted the results of the TABLE 1 in a The TABLE 2 shows the Min and Max values, bar chart represented in the figure 2: Means and Standard deviations of SAR in 1993 and in 2008: TABLE 2 : Max levels, min levels, means and standard devia- tions of SAR in 1993 and in 2008. SAR/Year 1993 2008 Max Value 7,04 29,46 Min Value 0,07 0,76 Standard deviation 1,11 5,09 Mean 1,15 3,76 Number of samples 59 59 Moroccan standards 3 ppm 3 Ppm à 4 ppm à 4 Figure 2 : Comparison of SAR average levels between 1993 Canadian standards 0 0 Ppm and 2008 We have noticed an increase in SAR average lev- els for all the classes between 1993 and 2008. We high- light the fact that the number of wells has increased for the class 2, even if their SAR average levels remains constant. Thus, the percentages of wells in each SAR class between 1993 and 2008 are reported in the figure 3: The comparison between the percentages of wells of each SAR class between 1993 and 2008, allows us to draw the following conclusions: * A decrease in the percentage of wells that have a very Figure 4 : Average SAR levels in 1993 and in 2008 Environmental Science An Indian Journal ESAIJ, 5(1) February 2010 A.Echchelh et al. 49 Current Research Paper We have presented the results in a bar chart, see the TABLE 2: The variance analysis of the results confirms a very significant difference of SAR between 1993 and 2008.