Quality assessment of ground water for irrigation 149 QUALITY ASSESSMENT OF GROUND WATER FOR IRRIGATION IN DISTRICT JHANG Muhammad Shafiq and Muhammad Saleem* ABSTRACT A study was conducted in the Directorate of Land Reclamation, Lower Chenab Canal Circle, Faisalabad, Pakistan to assess the suitability of ground water of 106 villages of district Jhang for irrigation. Water sampling, one sample from each village, was done four times i.e. pre-monsoon 2009, post-monsoon 2009, pre-monsoon 2010 and post-monsoon 2010. Chemical analysis was done for electrical conductivity (EC), sodium adsorption ratio (SAR) and residual sodium carbonate (RSC). According to results, 30 samples (28.3% of total samples) were found unfit while remaining 76 samples (71.7%) were observed as fit for irrigation purposes. Eighteen samples (16.98%) had electrical conductivity higher than permissible limit (≥1.50 dS/ m), 7 samples (6.6%) were found having high SAR (>10m mol/L)0.05 and 19 samples (17.92%) had high RSC (≥2.5 me/L). It can be inferred from data that quality of available ground water in some of the villages is not suitable for sustainable crop production and soil health. Installation of private tubewells in the area under study must be site- specific, keeping in view the groundwater quality data. Also farmers of locality may be aware of the existing situation of groundwater for irrigation purpose. KEYWORDS: Ground water, irrigation quality; electric conductivity; sodium adsorption ratio; residual sodium carbonate; Jhang; Pakistan. INTRODUCTION Pakistan is basically an agricultural country but most of its agriculturally productive area falls in the arid and semi-arid climate. The rainfall varies considerably ranging from less than 10 mm per annum in some parts of the country to more than 500 mm in other parts (5). Most of the rainfall is received during July to September (monsoon). So, potential production cannot be achieved without ensured irrigation supplies. Determination of water quality through analysis is pre-requisite for its better utilization by crops as it is essential for the maintenance of turgidity, absorption of nutrients and metabolic processes of plants. (11). *Directorate of Land Reclamation, Lower Chenab Canal Circle, Faisalabad, Pakistan. J. Agric. Res., 2013, 51(2) 150 M. Shafiq and M. Saleem Due to change in climate and thereby extended drought, surface-water resources of Pakistan were reduced by about 70 percent in 2003, compared with normal years (8). Unfortunately, canal water is not sufficient to exploit the potential of soil and crop cultivars under intensive cropping system. The scarcity of good quality surface water is becoming more acute day by day. So one has to rely on irrigation through tubewells. Irrigation through tubewells has advantage over rainfall as it is under control with respect to time and amount of water application. A study (8) has shown that out of 560,000 tubewells in Indus Basin, about 70 percent are pumping sodic water which in turn is affecting the soil health and crop yields. According to Hussain et al. (7) two third of underground water of Punjab is unfit for irrigation and requires prior amendment or scientific management. Ayers and Westcot (4) have stated that water used for irrigation can vary greatly in quality depending upon type and quantity of dissolved salts. Salts are present in irrigation water in relatively small but significant amounts. These salts originate from dissolution of weathering of the rocks and soil, including dissolution of lime, gypsum and other slowly dissolved soil minerals. The suitability of water for irrigation is determined not only by the total amount of salts present but also by the kind of salts. Water quality or suitability for use is judged on the severity of problems that can be expected to develop during long-term use. The problems that result vary in both kind and degree and are modified by soil, climate and crop, as well as by the skill and knowledge of water user. The soil problems most commonly encountered and used as a basis to evaluate water quality relate to salinity, water infiltration rate, specific ion toxicity and a group of other miscellaneous problems. According to Shakir et al. (14), 64 water samples were collected from new tubewell bores from various locations of district Kasur to check the quality of underground water for irrigation purpose. In these samples electrical conductivity varied from 524 to 5700 µS/cm, sodium adsorption ratio from 0.49 to 26.00 while residual sodium carbonate ranged from zero to 17.00 me/ L. Out of 64 samples, 26 were found fit, 8 were marginally fit and 30 samples were found unfit for irrigation. Zahid et al. (16) tested 680 water samples, of which 33 percent were found fit, 19 percent marginally fit and rest of 48 percent were observed as unfit. Rizwan et al. (13) evaluated ground water quality (96 samples) for irrigation in Rawalpindi district. They noted that 71 percent samples were fit, 9 marginally fit and 20 percent were found unfit for irrigation. J. Agric. Res., 2013, 51(2) Quality assessment of ground water for irrigation 151 For successful crops production on sustainable basis without deteriorating soils, quality of groundwater is of main concern. Present study was carried out to assess the ground water quality in Jhang district of Pakistan for its irrigation suitability. MATERIALS AND METHODS This study was conducted in the Directorate of Land Reclamation, Lower Chenab Canal Circle, Faisalabad, Pakistan during the year 2009-10. In all 106 villages of district Jhang were selected. Water samples from tubewells of each village were collected four times i.e. pre-monsoon 2009, post-monsoon 2009, pre-monsoon 2010 and post-monsoon 2010 in plastic bottles after 30 minutes of tubewell operation. Tubewell selection was made at random and depth of bores ranged from 80 to 100 feet. Analytical work was carried out at Soil and Water Testing Laboratory, Directorate of Land Reclamation Punjab, Lahore. These samples were analyzed for anions (CO3--, HCO3-,), cations (Na+, Ca++ + Mg++), pH and EC. Sodium adsorption ratio (SAR) and residual sodium carbonate (RSC) were calculated with following equations: 1/2 SAR= Na {(Ca + Mg)/2} -- - ++ ++ RSC (me/L) = (CO + HCO ) – (Ca + Mg ) 3 3 Here the concentrations are expressed in milli equivalents per liter (me/L) (12). Water quality was assessed according to criteria given by Malik et al. (9) (Table 1), while others are for comparison purpose. The data were analyzed statistically for mean, standard deviation and percentage following the procedure described by Steel and Torrie (15). The parameters TSS, SAR and RSC were calculated from primary data (EC, Ca + Mg, CO , HCO and 3 3 Na). Table 1. Irrigation water quality criteria. Richards WAPDA Muhammad Malik et al. Parameter Status (1954) (1981) (1996) (1984) Suitable <0.75 <1.5 <1.5 <1.5 EC (dS/m) Unsuitable >2.25 >3 >2.7 >1.5 Suitable <10 <10 <7.5 <10 SAR Unsuitable >18 >18 >15 >10 Suitable <1.25 <2.5 <2.0 <2.5 RSC(me/L) Unsuitable >2.5 >5.0 >4.0 >2.5 J. Agric. Res., 2013, 51(2) 152 M. Shafiq and M. Saleem Soil characteristics Healthy soil consists of roughly 40 percent mineral, 23 percent water, 23 percent air, 6 percent organic material and 8 percent living organisms. Soil texture is concerned with the relative proportions of mineral particles of various sizes in a given soil. These particles are grouped into three basic categories: sand, silt and clay. Sand particles are the largest ones in soil other than gravel or other rocks. Intermediate sized particles are called silt. The very smallest particles in soil are clay. Twenty soil samples were collected from the selected study area (Table 2) at the depth of 0-15cm. These samples were analyzed for EC, pH, organic matter (%), available phosphorus (mg/kg), available potassium (mg/kg), saturation percentage, soil texture and for gypsum requirement (tons/acre). RESULTS AND DISCUSSION Soil analysis (Table 2) showed that EC of soil saturation extract ranged from 1.43 dS/m of Ghanwan village to 5.44 dS/m in Chak No. 462 JB, soil pH Table 2. Soil characteristics of some selected sites Village/ Depth EC Soil Orga- Available Available Saturation Texture Gypsum Chak No. (cm) dS/m pH nic phosphorus potassium (%) required matter (mg/kg) (mg/kg) (tons/acre (%) ) 29/JB 0-15 2.03 8.0 0.26 2.15 150 34 Loam Nil Clay 216/JB 0-15 3.99 7.8 0.10 1.75 110 32 Loam 2.4 448/JB 0-15 4.02 7.8 1.29 2.37 90 36 Loam 1.8 447/JB, 0-15 3.00 7.8 1.03 1.05 70 34 Loam 2.0 Clay 452/JB 0-15 3.77 7.9 0.78 3.18 90 46 Loam 0.9 466/JB 0-15 1.86 7.8 0.52 2.85 170 46 Loam Nil 255/JB 0-15 1.89 8.0 0.78 3.21 100 40 Loam Nil Moza Thattha 0-15 1.90 8.0 0.52 2.75 190 38 Loam Nil Basti Sadiqabad 0-15 1.99 7.9 0.36 3.35 180 42 Loam Nil 270/JB 0-15 2.02 7.8 0.26 2.85 70 38 Loam Nil 268/JB 0-15 2.06 7.9 0.52 3.47 50 40 Loam Nil Silt 450/JB 0-15 4.19 7.9 0.41 2.98 40 37 Loam 1.5 385/JB 0-15 5.42 7.9 0-36 3.56 180 38 Loam 3.1 462/JB 0-15 5.44 7.8 0.26 3.11 160 38 Silty 4.2 461/JB 0-15 5.41 7.8 0.36 2.84 130 36 Loam 2.2 Ghanwan 0-15 1.43 7.8 0.26 2.52 110 34 Loam Nil Hasnana 31/3 0-15 1.66 7.7 1.03 10.72 100 37 Silty Nil Vajlana, 81/20 0-15 1.95 7.7 0.93 9.85 90 34 Loam Nil Kot Mirza 0-15 1.82 7.7 0.52 11.85 110 38 Loam Nil Kot Hayder 8/8 0-15 2.12 7.6 0.26 10.61 100 35 Loam Nil J.