impact of agricultural activities on groundwater quality and its suitability for drinking in...
TRANSCRIPT
IMPACT OF AGRICULTURAL
ACTIVITIES ON GROUNDWATER
QUALITY AND
ITS SUITABILITY FOR DRINKING
IN VALIKAMAM AREA,
JAFFNA PENINSULAA. Sutharsiny
S. Pathmarajah
M. Thushyanthy
V. Meththika
H. Manthrithilake
INTRODUCTION...
INTRODUCTION
Vadamaradchi
aquifer
Thenmaradchi
aquifer
Kayts
aquifer
Chunnakam
aquifer
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
METHODOLOGY
Selection of wells
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
RESULT AND DISCUSSION
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.
General:
Electrical Conductivity (EC)
0
1000
2000
3000
4000
5000
January March April July October
EC
(µ
S/c
m)
Public wells
10
11
12
13
14
15
16
17
18
Max Per
Max Des
0
200
400
600
800
1000
1200
1400
1600
1800
2000
January March April July October
EC
(µ
S/c
m)
Farm wells (highland)
26
27
28
29
30
31
32
33
34
35
Max Des
0
500
1000
1500
2000
2500
January March April July October
EC
(µ
S/c
m)
Farm wells (highland)
36
37
38
39
40
41
42
43
44
Max Des
0
1000
2000
3000
4000
5000
6000
7000
8000
January March April July October
EC
(µ
S/c
m)
Domestic & Domestic + homegarden wells1
2
3
4
5
6
7
8
9
Max Des
Max Per
0
500
1000
1500
2000
2500
3000
3500
4000
January March April July October
EC
(µ
S/c
m)
Farm wells (paddy & banana)
19
20
21
22
23
24
25Max Des
Max Per
Fluoride
Nitrate –N
0
10
20
30
40
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
NO
3-N
(m
g/L
)
well noJan March April
Max Des
Mixed HighlandBananaPaddy
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
Crop
Crop
stage Kc
ET0
March ET-crop
Irrigation
(mm/day)
Excess irrigation
(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
Excess irrigation for each crop in studied area
Excess amount of nitrogen application for each crop
Crop Avg. nitrogen
applied (kg/ha)
Recommended
nitrogen (kg/ ha)
Excess nitrogen
(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
-
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
- use of large quantities of inorganic fertilizers
- with excessive irrigation
were considered to be responsible for
the high nitrate content.
Based on analysis of CWR and amount of N- application
for each crop,
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.
THANK YOU…
Acknowledgement…
- International Water Management Institute (IWMI)
- CB project, PGIA, University of Peradeniya