Irrigation Water Quality Assessment for Water Resources used in Irrigation of Agricultural Fields in Mezitli Town of Mersin Province

Electrical conductivity (EC) is the most significant indicator of irrigation water quality. It is a measure of salinity with great impacts on crop productivity. Waters with high ECvalues reduce crop yields through reducing plant competition for water with the ions of soil solution. The greater the EC is, the less the water available for plants despite moist appearance of the soil [1].

Besides irrigation water quantity, irrigation timing and irrigation methods, irrigation water quality is also a significant parameter in modern irrigation systems [2]. When the sufficient quantity and quality irrigation water is not available, improper water resources are used in irrigations. Such waters then alleviate salinity problem. In a previous study, water samples were taken from 10 irrigation ponds in June, July, August and September to assess water quality of the ponds used for irrigation water supply in Hakkari province of Turkey. Samples were analyzed for EC, pH, anion and cations (Ca+2, Mg+2, K+, Na+, SO-2, NO-2, CO-2, HCO-and CI-). Resultant values were used to calculate sodium adsorption ratio (SAR), 4 3 3 3 residual sodium carbonate (RSC) and percent sodium (% Na) values. Research findings revealed that pH, EC, SAR, RSC and % Navalues of irrigation ponds did not exceed threshold values, but Mg+2 and K+ values of the pond waters in Akçalı Village – Kanatlı locality and K+ values in Kırıkdağ Village-Şişer locality exceeded threshold values [2]. Total salt quantity of irrigation waters is expressed as electrical conductivity (EC x 106) in μmhos/cm (1000μmhos/cm=1mmhos/cm=1dS/m). Majority of waters used successfully in irrigated farming has a total salt concentration of less than 2250 μmhos/cm. In terms only of total salt concentration, electrical conductivity of irrigation waters should be less than 750 μmhos/cm. However, irrigation waters with electrical conductivity of between 750-2250 μmhos/cm are largely used. Such waters may offer sufficient yield levels under proper drainage and operational conditions, but salinity problem may emerge if the sufficient leaching was not provided under improper drainage conditions [3]. Yeter and Yurtseven [4] investigated the effects of different quality irrigation waters on alfalfa plants and reported recessed growth, reduced yield and quality in alfalfa plant irrigated with saline waters. On the other hand, it was indicated that when sufficient leaching was provided and excess salt was removed from the rootzone, plant growth and development returned to normal levels. Researchers finally concluded that for high yield levels in alfalfa farming, irrigation water salinity should be less than 1.5 dSm-1.

Salinity and alkalinity problems are largely encountered in irrigated farming lands of arid and semi-arid regions of the world. Low precipitation levels, poor-quality irrigation waters and high evaporation rates aggravate salinity and alkalinity problems of these regions. Such problems also destruct structural characteristics of the soils [5-6].

Gürcan [7] conducted a study to assess the water quality in irrigation district of Ankara Haymana Soğulca Village irrigation cooperative and classified irrigation water samples as C (highly saline) and indicated that these waters could not be used in 3 fields with limited drainage facilities. It was also indicated that despite salinity problems in water resources of the irrigation district, salinity was not encountered in agricultural fields irrigated with these waters. However, it was recommended that closed or open drainage facilities should be constructed to prevent potential salinity problems in the future. Topçu and Taş [8] conducted a study on Çanakkale Biga Plain and investigated electrical conductivity (EC), pH, potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), carbonate (CO ), bicarbonate (HCO ), chlorine (Cl), sulphate (SO ), 3 3 4 nitrate (NO ) and boron (B) of water samples taken from 20 groundwater wells. Considering the classification system of 3 Water Pollution Control Regulation (SKKY) and salinity parameters, 11 of 20 samples were classified as the second-class and the rest was classified as the first-class. Apart from nitrate pollution in groundwaters, a distinctive problem was not encountered in the research site overall.

Demer and Hepdeniz [9] investigated groundwater quality with the use of water samples taken from 21 groundwater wells in Isparta Plain and reported water quality class of some wells as C S (highly saline – slightly alkaline) and the rest as C S 3 1 2 1 (moderately saline – slightly alkaline).

Dorak and Çelik [10] conducted a study to determine the effects of domestic and industrial wastewater effluents on Nilüfer Creek and took water samples from treated wastewater effluents of 5 treatment facilities and from the creeks to which treated wastewater effluents were discharged at 4 different sampling periods between August 2013 – May 2014. It was reported that water quality of Nilufer Creek and treatment facilities varied with the sampling periods, quality classes of water samples based on ECand SAR were identified as between C S-C Sand discharged effluents negatively influenced especially pH, 2 1 4 4 EC, ammonium, sulphate, boron and chlorine values of Nilfer Creek.

Akaroğlu and Seferoğlu [11] conducted a study in Sultanhisar town of Aydın province to assess irrigation water quality and reported that water quality classes varied between C S-C S , canal water quality influenced fruit quality and boron content 2 1 3 1 of plants irrigated with these waters was greater than the boron content of control plants.

Aregahegn and Zerihun [12] took water samples from 17 sampling sites along the Awash River in four different sampling periods to assess the water quality of Awash River and tributaries. General water quality and suitability for irrigation were assessed with the use of several water quality parameters including pH, EC, SAR, RSC, Na +, K +, Ca++ + Mg++, CO 2−, 3 HCO − and Cl−. It was reported that entire quality parameters in Beseka Lake exceeded maximum allowable limits for 3 irrigation, physicochemical characteristics of Awash River varied with the sampling sites and water quality parameters, pH and SAR values only of Beseka Lake and Meteka hot spring waters exceeded the allowable limits, Mojo, Wonji, Beseka, Melkasedi, Werer, Ambash, Meteka and Meteka hot spring waters had moderate-high salinity (EC) levels and very high RSC levels. It was recommended that industrial wastewater treatment facilities should be constructed to improve water quality of Awash River and tributaries.