Journal of Environmental Research And Development Vol. 5 No. 3A, January-March 2011

Transcription

1 COMBINED EVALUATION OF GROUND WATER OF KHUNWADE AND BORDI OF DAHANU TALUKA, MAHARASHTRA, INDIA ON THE BASIS OF ELECTRICAL CONDUCTIVIEY AND SODIUM ADSORPTION RATIO Gogari P. K. 1, Chaudhari V. S.* 2 and Save S. N Department of Botany, N. B. Mehta Sc. College, Bordi, Thane, Maharashtra (INDIA) 2. Department of Bio-technology, N. B. Mehta Sc. College, Bordi, Thane, Maharashtra (INDIA) 3. Department of Chemistry, N. B. Mehta Sc. College, Bordi, Thane, Maharashtra (INDIA) Received September 23, 2010 Accepted February 17, 2011 ABSTRACT The study area Dahanu is last surviving green zone between Mumbai and Surat. Its 47% of area is under forest cover. The economy of area depends on its Sapota plantation as seven out of ten chikoos of the country grow here. Water samples were collected from 26 locations during pre and post monsoon period of The study aims to classify ground water on the basis of combined effect of Electrical Conductivity (EC) and Sodium Adsorption Ratio (SAR) to check its suitability for irrigation. The ground water is rated by a semi logarithmatic diagram published by United States Salinity Laboratory (USSL). Key Words : Ground water quality, Salinity, Sodium Adsorpt Ratio (SAR), Electrical Conductivity (E.C.), USSL. INTRODUCTION Water is the most useful natural resource on earth economically, culturally and biologically. Though water is seemingly abundant, uneven distribution of usable water creates a serious conservation problem in many places where it is vitally needed. Total replenish able ground water in India is estimated at 43.1 Mha-m (Mega hectare meter) per year. It is estimated that about Mha-m is available for irrigation 1. India, though, developing fast in the field of technology and industry, still remains an agricultural country. Agriculture is a dominant sector in economic development of India as it is the source of sustenance for majority of the population. About 70% of Indian economy is based on agriculture, directly or indirectly. Irrigated agriculture depends on an adequate water supply of usable quality. *Author for correspondence 779 These quality parameters are many times neglected as good quality water supplies had been plentiful and readily available. But the situation has now changed in many areas at an alarmingly fast rate. It was observed that the criteria used in classification of water for a particular purpose may not find suitability standards for other purposes and better results can be obtained considering the combined chemistry of all the ions rather than individual or paired ions characters 2. Suitability of ground water for irrigation purposes depends upon its mineral constituents. Wilcox 3 classified ground water for irrigation on the basis of percent sodium and electrical conductivity. Water can also be classified based on hardness 4. Eaton 5 recommended use of concentration of residual sodium carbonate to determine suitability of water for irrigation purpose. United States Salinity Laboratory of the Department of Agriculture has classified water samples based

2 on combined Sodium Adsorption Ratio (SAR) and Electrical Conductivity (EC) values 2,6. Piper developed a form of a trilinear diagram which is an effective tool in segregating analysis data 7,8. Water which fits in the suitability standards by one method of classification can be unsuitable by the other method of classification. Dahanu is the last surviving green zone between Mumbai and Surat. Its 47% area is under forest cover. As per 2001 census, the population of Dahanu taluka is 3,31,829 of which 55% is tribal. Till date, the economy of Dahanu, Gholwad and Bordi survives on its sapota (chikoo) plantations as seven out of ten chikoos of the country grow here. About 37 thousand tonnes of chikoo are produced per month 9. Since it is declared as Ecologically Fragile area by Central Government notification dated June 20, 1991, there are no industries here. But a thermal power station is set up at Dahanu Road, about 20 km south of Bordi. In North, there is an Industrial Estate of Umbergaon (GIDC) about 15 km from Bordi 10. An attempt is made to study the physical and chemical parameters of the ground waters in Khunwade and Bordi area of Dahanu taluka to check its suitability for irrigation. The area under investigation is situated between N latitude and E longitude (Fig. 1). Fig. 1 : Geographic position of Bordi, Dahanu, Thane, Maharashtra, (India) MATERIAL AND METHODS 26 samples were collected from Bor di - Khunwade area during pre-monsoon period (April 2008) and post-monsoon period (October 2008). Locations for collection of ground water samples were kept same during both periods. The distance between the locations was maintained more than 50 m. The texture of soil changes from loamy to sandy as coastal area approaches. The samples were collected from bore wells of depth of 60 to 120 feet. The water is irrigated to the plants by motor pump. The pump is run for about 10 minutes prior to sampling. The water is collected into pre-cleaned (and rinsed with water 780 sample) polythene containers for analysis. Each sample was properly labelled. The analysis was done by standard methods 11,12. RESULTS AND DISCUSSION Salinity Hazard The most influential water quality guideline on crop productivity is Water Salinity Hazard as measured by Electrical Conductivity (EC). Total concentration of soluble salts is the single most important criterion which has been used conventionally for determining quality of irrigation water 1. Table 1 gives the classification of pre-monsoon and postmonsoon samples based on salinity hazard.

3 Table 1 : Electrical conductivity of pre and post monsoon water samples Pre Monsoon Post Monsoon Sample Electrical Salinity Hazard Class Electrical Salinity Hazard Class No. conductivity Conductivity µ Scm -1 µ Scm Medium C2 277 Medium C Medium C2 342 Medium C Medium C2 530 Medium C Medium C2 370 Medium C Medium C2 546 Medium C Medium C2 908 High C High C3 639 Medium C Medium C2 685 Medium C Medium C2 581 Medium C Medium C2 507 Medium C High C3 850 High C High C3 866 High C High C High C High C High C Very High C Very High C High C High C High C High C High C High C High C High C High C High C High C High C High C High C High C High C High C3 850 High C High C High C High C3 959 High C3 Sodium Adsorption Ratio (SAR) Apart from the total salinity, the next important consideration is whether the use of irrigation water of given quality will cause sodicity in the soil. Water which might be considered suitable for irrigation on the basis of electrical conductivity may not be suitable if sodium predominates 1. A sodic soil is defined as the one, SAR of which is greater than 15. Irrigation water, which dose not increase SAR of the soil beyond 15, is considered to be of good quality. Sodium hazard has been expressed as per cent sodium of total cations. A better measure of the sodium hazard for irrigation is the SAR which is used to express reactions with the soil 1. SAR is computed as SAR Ca 2 Na Mg 2 2 1/ 2 where all ionic concentrations are expressed in epm (milli equivalents per litre). Table 2 gives the classification of the pre-monsoon and postmonsoon water samples with respect to SAR. 781

4 Table 2 : Classification of pre and post monsoon water samples based on SAR Pre Monsoon Post Monsoon Sample SAR epm Class Sodium SAR epm Class Sodium No. Hazard Hazard S1 Low S1 Low S2 Medium S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S2 Medium S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S1 Low S4 Very High S1 Low S2 Medium S1 Low S2 Medium S1 Low S4 Very High S2 Medium S4 Very High S1 Low S4 Very High S2 Medium S4 Very High S2 Medium S4 Very High S1 Medium S4 Very High S1 Low S2 Medium S1 Low S2 Medium S1 Low S1 Low S1 Low Combined evaluation on the basis of EC and SAR United States Salinity Laboratory(USSL) 6 has published a semi logarithmic diagram, which rated waters with respect to EC and SAR. Fig. 2 and Fig. 3 show the positioning of pre-monsoon and post-monsoon samples in the USSL diagram, respectively. SAR becomes very high for the water samples as we go away from the mountain. SAR values for samples collected nearest to the sea shore (sample no. 24, 25, 26) were low to medium. The calcium contents of these samples were higher than the water sample with high SAR values (Sample no 18 23). This should be taken into account in the use of S4 class waters. The sodium status of such waters may be improved by the addition of gypsum to the water. Application of potassium oxide can reduce considerably the negative effects of salinity and can reduce the amount of accumulation of sodium 13,14. Synchronized application of potassium and gypsum can be suggested. Considering USSL diagram, percentage of samples in C2S1 Class were 23.08% in pre monsoon and 34.62% in post monsoon Fig. 2 and Fig. 3. Only 11.54% samples from pre monsoon were in C2S2 class. 3.85% pre monsoon samples 782

5 Fig. 2 : Pre-monsoon positioning of samples in USSL diagram Fig. 3 : Post-monsoon positioning of samples in USSL diagram 783

6 and 42.31% post monsoon samples were in C3S1 class. The percentage of samples in C3S2 class was 23.08% for pre monsoon and 3.85% for post monsoon % pre monsoon and 7.69% post monsoon water samples accommodated C3S3 class. The percentage in C3S4 class was 23.08% for pre and 7.69% for post monsoon. Only 3.85% post monsoon samples were from C4S3 class while 3.85% pre monsoon samples were from C4S4 class. In addition to water quality, other factors like soil type, crop pattern, frequency and recharge (rainfall), climate etc. have an important role in determining the suitability of water 2. CONCLUSION Amongst fruit trees, Sapota and Guava have potential for development in all the saline coastal areas. Judging by the quality of water, it may not affect the quality and quantity of these major fruit crops in Dahanu Taluka. Satisfactory crop growth can be obtained under good management and favourable drainage conditions, but saline conditions might develop if leaching and drainage are inadequate. According to a report on development of costal areas affected by salinity, made by National committee on development of backward areas 14, in Gujrat state along Saurashtra coast, acute problem of salinity hazard has manifested itself. Ground water quality in the belt has been progressively getting more saline. One of the principal causes attributed is over exploitation of ground water. Sample no have high values of SAR. It was observed that these sites are located in the area more populated compared to other sites. The area is well developed from horticulture point of view. The farmers have been taking intercrops like brinjal (egg plants), bottle gourd, tomato, bhindi (lady finger), banana, and lily for last years. These crops require continuous supply of water and use of fertilizers and pesticides. The soil in the area is clay loamy which has high water retention capacity (inadequate drainage). These could be some of the factors attributing to high SAR values. 784 RECOMMENDATIONS It is necessary to carry out extension activities by scientific institutions or officers to make the farmers and tribal people aware of gravity of situation and inform them about suitable control measures such as : Reducing the excessive pumping out of water Decreasing the use of chemical fertilizers and pesticides Employing organic farming practices Use of gypsum and potassium Use of cow dung manure as soil conditioner to improve drainage characteristics of soil. Care should be taken at least to maintain the of ground water quality Ground water should also be monitored regularly. REFERENCES 1. Gupta I. C. and Gupta S.K., Use of saline water in agriculture, Jodhpur, India, 308, (2003). 2. Kumaresan M. and Riyazuddin P., Major ion chemistry of environmental samples around sub-urban of Chennai, Ind. Curr. Sc., 91(12), , (2006). 3. Wilcox L.V., Classification and use of irrigation waters, U.S. Department of Agri. Circ. 969, as cited in Walton, 2401, (1955). 4. Sawyer G. N. and McCarthy D. L., Chemistry of Sanitary Engineers, New York, McGrew Hill, 2 nd Ed, (1967). 5. Eaton E. M., Significance of Carbonate in Irrigation Waters, Soil Science, 69, , (1950). 6. U.S. Salinity Laboratory Staff, Diagnosis and improvement of saline and Alkali soils, U.S. Department of Agriculture Handbook, 60(5), 69-82, (1954). 7. Piper A. M., A Graphic procedure I, The Geochemical Interpretation of Water Analysis, USGS ground water note no.12, as cited in Walton, 243, (1953).

7 8. Walton W. C., Ground Water Resource Evaluation, New York, McGraw- Hill Book Company, 4th Ed , (1970) talk-economy html, (2008) (2008). 11. Gupta P. K., Methods in environmental analysis- water, soil and air, Agrobios Jodhpur, India, (2000). 12. De A. K., Environmental Chemistry, New Delhi, New Age Publications, (2007). 13. Bahmaniar M. A., Interactive effects of saline irrigation water-k and gypsum on mineral nutrient accumulation and grain protein content of wheat, J. Agrono., 5(2), , (2006). 14. National committee on development of backward areas, Report on development of costal areas affected by salinity, Planning Commission, Govt. of India, New Delhi, (1981). 785