A. Sutharsiny S. Pathmarajah M. Thushyanthy V. Meththika H. Manthrithilake

1. IMPACT OF AGRICULTURAL
ACTIVITIES ON GROUNDWATER
QUALITY AND
ITS SUITABILITY FOR DRINKING
IN VALIKAMAM AREA,
JAFFNA PENINSULA
A. Sutharsiny
S. Pathmarajah
M. Thushyanthy
V. Meththika
H. Manthrithilake

2. INTRODUCTION...
INTRODUCTION
Chunnakam
aquifer Vadamaradchi
aquifer
Kayts
aquifer
Thenmaradchi
aquifer

3. OBJECTIVES
Assess the impact of agricultural activities on
groundwater 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

4. METHODOLOGY
Selection of wells

5. Collection of water samples
 sampling was carried out in mid of January, early part of
March and mid of April 2011
Analytical 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

6. RESULT AND DISCUSSION
General:
 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.

7. 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
28
EC (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

11. Fluoride

12. Nitrate –N

13. 40
NO3- 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)

14. 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)

15. Influence of agronomic practices on concentration
of nitrate-N in agricultural areas
 Excess irrigation for each crop in studied area
Crop ET0 Irrigation Excess irrigation
Crop stage Kc March ET-crop (mm/day) (mm/day) (%)
Banana mid 1.1 4.5 4.98 11.86 6.88 138
Cabbage mid 1.05 4.5 4.76 15.65 10.89 229
Cassava mid 0.8 4.5 3.62 9.45 5.82 161
Onion late 1 4.5 4.53 11.25 6.72 148
Tobacco late 0.9 4.5 4.08 9.41 5.33 131

16.  Excess amount of nitrogen application for each crop
Crop Avg. nitrogen Recommended Excess nitrogen
applied (kg/ha) nitrogen (kg/ ha) (kg/ha)
Onion 178.1 70 108.1
Carrot 230 150 80.0
Cabbage 142.6 150 -7.4
Beetroot 246 180 66.0
Tobacco 262.9 No -
recommendation

17.  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

19. 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.

20. 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.

21. Acknowledgement…
- International Water Management Institute (IWMI)
- CB project, PGIA, University of Peradeniya
THANK YOU…