Impact of Agricultural Activities on Groundwater Quality and its Suitability for Drinking in Valikamam Area, Jaffna Peninsula
IMPACT OF AGRICULTURALACTIVITIES ON GROUNDWATER QUALITY ANDITS SUITABILITY FOR DRINKING IN VALIKAMAM AREA, JAFFNA PENINSULA A. Sutharsiny S. Pathmarajah M. Thushyanthy V. Meththika H. Manthrithilake
OBJECTIVES Assess the impact of agricultural activities ongroundwater quality and its suitability for drinking in Valikamam area, Jaffna Peninsula Characterize the chemical quality Map the spatial variation of water quality Find out the effect of land use under different cropping systems, irrigation practices and fertilizer application on chemical quality of groundwater
Collection of water samples sampling was carried out in mid of January, early part of March and mid of April 2011Analytical techniques pH, EC, chloride, nitrate- N, fluoride, calcium, magnesium, carbonate, bicarbonate, sodi um and potassium concentration Spatial distribution maps for different parameters CROPWAT 8.0 Questionnaire survey
RESULT AND DISCUSSIONGeneral: Size of the farm lands : 0.1 – 1.5 ha. The depths of the wells: 2.5 - 10 m. Most of the farmers keep the land fallow for two months (August and September) In intensified agricultural areas, year round cultivation without fallowing the land Timing of crop, irrigation, fertilizer application and all the cultivation practices are decided by the farmer with their experience.
Electrical Conductivity (EC) Domestic & Domestic + homegarden wells 5000 Public wells 1 8000 10 2 7000 4000 11 3 Max Per 6000 12 EC (µS/cm) 4 EC (µS/cm) 5000 3000 13 5 4000 Max Per 14 6 2000 15 3000 7 16 2000 8 Max Des 1000 Max Des 17 1000 9 18 0 0 January March April July October January March April July October 2000 2500 Farm wells (paddy & banana) Farm wells (highland) Farm wells (highland) 4000 1800 3500 2000 1600 36 Max Per 26 19 37 3000 1400 27 EC (µS/cm) 1500 38 28EC (µS/cm) 20 1200 39 EC (µS/cm) 2500 21 29 30 40 22 1000 1000 Max Des 2000 31 41 23 800 32 42 1500 24 33 43 600 Max Des 500 25 34 44 1000 Max Des 35 400 0 500 200 January March April July October 0 0 January March April July October January March April July October
40NO3- N (mg/L) 30 20 Max Des 10 0 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 Jan March April well no Paddy Banana Highland Mixed general decreasing trend - from January to March 35mg/L was observed at Thirunelvely and Neervely (highland and mixed crop)
Effect of land use High nitrate –N was observed at high land crops land use followed by banana and paddy. Concentration of nitrate-N in paddy and banana land use had less than the recommended level Cultivation of banana is normally under basin irrigation with organic fertilizers Organic manure increases nitrogen retentions capacity and reduces nitrate loss by leaching in sandy soils (Premanandarajah et al.,2003)
Influence of agronomic practices on concentration of nitrate-N in agricultural areas Excess irrigation for each crop in studied area Crop ET0 Irrigation Excess irrigationCrop stage Kc March ET-crop (mm/day) (mm/day) (%)Banana mid 1.1 4.5 4.98 11.86 6.88 138Cabbage mid 1.05 4.5 4.76 15.65 10.89 229Cassava mid 0.8 4.5 3.62 9.45 5.82 161Onion late 1 4.5 4.53 11.25 6.72 148Tobacco late 0.9 4.5 4.08 9.41 5.33 131
Excess amount of nitrogen application for each cropCrop Avg. nitrogen Recommended Excess nitrogen applied (kg/ha) nitrogen (kg/ ha) (kg/ha)Onion 178.1 70 108.1Carrot 230 150 80.0Cabbage 142.6 150 -7.4Beetroot 246 180 66.0Tobacco 262.9 No - recommendation
Based on analysis of CWR and amount of N- application for each crop, - use of large quantities of inorganic fertilizers - with excessive irrigation were considered to be responsible for the high nitrate content. Inorganic fertilizer application practices were decided by the farmers farmers have been using organic materials such as biomass and cattle and goat excreta which are rich in nitrogen 66.7 % of farmers practiced paddock system
CONCLUSION Wells located in coastal area indicated high values of EC, sodium and chloride. Most of the farm wells are located interior, their water quality is generally superior to domestic and public wells. Farm wells contain nitrate-N levels above the acceptable level for drinking purposes. The level of nitrate-N was influenced by cropping system Excess irrigation and excess amount of nitrogen as inorganic fertilizer application were found at Valikamam area.
SUGGESTIONS Awareness should be created on the hazards due to the excessive use of chemical fertilizers in agriculture. Efficient irrigation water management practices should be introduced to prevent leaching of chemicals to the groundwater. Recommendations should be made based on continuous monitoring.
Acknowledgement…- International Water Management Institute (IWMI)- CB project, PGIA, University of Peradeniya THANK YOU…