irrigation. On the contrary in 2006 there is a potential for drought in several locations of Karawang.
4.1.13. Irrigation
The source for water irrigation from PJT II Jatiluhur is divided into 3 locations that is Curug dam for southern and eastern areas and Walahar dam for
northern area. Northern area receives the much water supply from irrigation. The water debit in Walahar dam during period January-September 2006 is shown in
Table 12 and for irrigation network is shown in Figure 16. Table 12. Discharge of water in Walahar dam m
3
s and Volume m
3
Period Water
Use Q1
Available Water
Q2 Water volume of
Q1 Water volume of
Q2
1-15 January 90.48 257.10
117,268,300.80 333,202,636.80
16-31 January 65.52
290.36 84,916,593.00
376,311,420.00 1-15 February 57.00 163.90
73,868,630.40 212,414,486.40
16-28 February 63.86
183.13 82,764,952.62
237,341,763.69 1-15 March
59.86 125.88 77,582,348.31
163,140,579.69 16-31 March
61.24 69.36
79,369,921.11 89,884,777.85
1-15 April 76.75
92.04 99,466,006.15
119,285,036.31 16-30 April
82.19 103.91
106,522,825.85 134,673,341.54
1-15 May 75.24
76.28 97,515,725.54
98,864,363.08 16-31 May
76.92 81.40
99,690,831.00 105,488,730.00
1-15 June 84.01
87.67 108,870,480.00
113,623,171.20 16-30 June
66.82 67.24
86,599,411.20 87,141,657.60
1-15 July 75.61
79.59 97,985,289.60
103,154,083.20 16-31 July
71.80 78.22
93,055,149.00 101,372,472.00
1-15 August 53.20
57.56 68,953,248.00
74,595,686.40 16-31 August
54.46 54.49
70,581,196.80 70,625,347.20
1-15 September 40.16 64.67
52,045,027.20 83,809,641.60
16-30 September 48.15 91.61
62,396,092.80 118,732,694.40
The water of Walahar dam is distributed to irrigation network in Karawang district. This area belongs to Division 2 of PJT-II Jatiluhur. Based on the data
48
mentioned above, available water supply is higher than water utilized January to September 2006.
North Tarum Networks
West Tarum Networks East Tarum
Networks
Figure 16. Irrigation Network Map Source: PJT II Jatiluhur
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4.1.14. Drought Indicator
Rain is the main source of water in the land for lives of crop, animal, and human. Decrease of land water can be identified by condition of surface cover and
open surface. Based on evaporation fraction as indicator of drought level it could be concluded that actual rainfall data for Karawang district differed from time to
time. For dry months the accumulation of rainfall is 100 mm or less per month. Actual occurrence of rainfall in several locations in Karawang is shown in Figure
17. Monthly average data from 1971 until 2000 are used. Monthly average rainfall data for 30 years indicate that the dry season in Karawang district occurs
from May to September and rainy season from October to April.
Rainfall in Batujaya
50 100
150 200
250 300
350 400
450 500
550
1 2
3 4
5 6
7 8
9 10
11 12
Month R
a in
fa ll
m m
Rainfall in Karaw ang
50 100
150 200
250 300
350 400
1 2
3 4
5 6
7 8
9 10
11 12
Month R
a in
fa ll
m m
50
Rainfall in Jatisari
50 100
150 200
250 300
1 2
3 4
5 6
7 8
9 10
11 12
Month Ra
in fa
ll m
m
Figure 17. Monthly average rainfall pattern in Karawang district period from 1971 to 2000 Source: BMG
According to the rainfall pattern the Landsat data used in this research can be grouped based on season as shown in Table 13.
Table 13. Acquisition data base on condition of season
Date Season
3-Jun-2003 Dry Season 18-Apr-2004 Wet Season
5-Jun-2004 Dry Season 23-Jul-2004 Dry Season
21-Apr-2005 Wet Season 10-Jul-2005 Dry Season
11-Aug-2005 Dry Season 1-Oct-2006 Dry Season
Based on average rainfall condition the irrigation capacity decreases as shown, the decrease in ability of soil to save water, the leaves vegetation become
yellowish adjusting to the long dry months. The decrease of irrigated water is correlated with increase of wide areas of drought vulnerability in Karawang
district. Nevertheless, irrigation water supply from PJT II Jatiluhur especially in division II Karawang provides enough water and decreases drought potential
areas. Result analysis for drought vulnerability in Karawang district by using
satellite image Landsat ETM 7+ indicates that in the dry month only a small area is vulnerable of drought. Relatively wider areas of drought potential is detected at
the beginning of rain season i.e. acquisition Landsat image in October 1, 2006.
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Evaporative fraction EF values used to determine area of drought vulnerability range from 0 – 0.4.
Landsat data June 3, 2003 analysis indicates potential of drought vulnerability is 2,746 Ha. Water availability in soil for June is adequate.
Indicator of water availability can be seen by land cover condition with relatively green vegetation index and high energy used for evaporation that indicates water
for evapotranspiration from soil and crop is available in the soil, only a small area in Karawang is potential of drought, which means most energy is used for sensible
heat flux. The same result is shown from Landsat image analysis for 2004 and 2005.
In 2004 there is increase of drought vulnerability from 1,074 Ha in June to 2,965 Ha in July. The same trend is observed for analysis in 2005 where increased area
of drought is from 322 Ha in July to 1,229 Ha in August. Similar increase of drought vulnerability area is shown for result analysis in 2006. The analysis is
based on data acquisition at the start of the rainy season, but climate conditions i.e. delay of the start of rainy season i.e. October is still the dry season. About
77,057 Ha areas in Karawang indicated drought vulnerability. The analysis results cover all areas of Karawang i.e. irrigated and non
irrigated lands. Data of paddy filed areas obtained from the Department of Agriculture for Karawang district and after being overlaid between paddy fields as
irrigated land and drought vulnerability area showed that the total area indicating drought vulnerability for irrigated land in June 2003, June 2004, July 2004, July
2005, August 2005 and October 2006 are 640 ha, 524 ha, 572 ha, 21 ha, 126 ha and 41,893 ha, respectively.
52
Figure 18. Paddy field areas in Karawang District Source: Department of Agriculture
Based on statistical data as shown in Table 14 it indicates that area of drought vulnerability which could not be recovered by irrigation water from 2003
until 2006 has increased from 915 Ha in 2003 to 1,142 Ha in 2006.
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Table 14. Drought vulnerability data in Karawang district
Year Criteria
2003 2004 2005 2006
Prediction Drought Vulnerability in Ha
- - 3,895
6,512 Drought
Vulnerability in Ha 915 975
- 1,142 - : no data
Details of predicted area of drought vulnerability in Karawang district are shown in Table 15.
Table 15. Prediction of drought vulnerability Year
No Sub District
2005 2006 1
2 3
4 5
6 7
8 9
10 11
12 13
14 Tempuran
Cileber Telagasari
Lemah Abang Cilamaya Kulon
Cilamaya Wetan Pedes
Cibuaya Pakisjaya
Batujaya Tirtajaya
Pangkalan Rawamerta
Jayakerta 345
235 115
250 260
1,350 648
380 175
45 100
1,274 625
460 1,030
470 1,350
200 785
318
Total 3,895 6,512
Source: PJT II Jatiluhur and Department Agriculture Karawang district Areas of drought vulnerability detected from analysis result of satellite
data and predicted by the Department of Agriculture and PJT II Jatiluhur are different. The analysis result from satellite data in 2005 covered areas of
Cikampek 63 ha, Jatisari 15 ha, and Klari 40 ha. In 2006, analysis result of satellite data of drought vulnerability areas covers all areas that are predicted
drought vulnerability; however satellite detects wider areas of drought vulnerability.
Referring to planting season and irrigation from PJT II Jatiluhur, in September all irrigated areas in Karawang already harvest their crop; so many
paddy field areas are bare and intentionally let dry waiting for the next planting season. In October it is the start of the rainy season, but on October 1, 2006 no
54
rain is detected so there is still drought vulnerability. This matter is caused by planting pattern that is not based on group irrigation. Details of planting season,
prediction of harvest and irrigation is presented in Table 16. Table 16. Schedule for planting season, prediction of harvest and watering
irrigation.
55
According to statistical data in 2006, the total paddy field areas in Karawang is 94,385 ha, of which 91,063 ha is irrigated and 3,322 ha non irrigated
lands. Details of paddy field areas from 2003 to 2006 are shown in Table 17. Irrigation system in Karawang leads to significant decrease of vulnerability
drought areas. Water irrigation becomes an important factor in decreasing drought vulnerability areas in Karawang.
Tabel 17. Paddy field area in Karawang district. Paddy
Field 2003 2004 2005 2006
Irrigation 89,630 89,614
87,952 91,063
Non Irrigation
3,167 3,172
3,163 3,322
Total 92,797 92,786
91,115 94,385
Source : BPS Karawang Based on debit data and volume of water in 2006 in Walahar dam the
water supply is higher than the water needed. Walahar dam itself regulates amount of water supplied to paddy field in irrigated lands in Karawang. Water
flow rate ranges from 50-300 m
3
s, but consumption is about 40-90 m
3
s. Furthermore, water required for industrial and household PDAM in Karawang
district is relatively low i.e. is 2.11 m
3
s and for agriculture during planting season is about 50-75 m
3
s. In September 2006 irrigation water used is relatively low and most of paddy field areas become dry till the next planting season. This condition
causes areas of drought vulnerability detected become wider, not because of water deficit. Generally irrigation water is enough for agriculture during planting during
the rainy rendeng and dry seasons gadu. Time for planting and harvesting in Karawang is different depending on
paddy field classification based on irrigation. There are five paddy field classifications based on watering, planting and harvest seasons. Watering starts
from group I and ends in group V. Almost all paddy field areas in Karawang depend on irrigation water. Group I is paddy field areas located near main
irrigation channel, while group V is farther located with this pattern it is expected that all paddy field area need of water irrigation can be fulfilled.
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In fact several paddy field areas in Karawang are still potential for drought vulnerability. Generally, areas suffer from drought vulnerability are located
farthest from main irrigation channel and it is included in group V for watering. Based on field information there are three main causes of drought i.e.:
1. Water flows especially during dry season gadu cannot reach the paddy field area located farthest from main irrigation channel.
2. Irregular planting pattern that is in appropriate with watering classification of paddy field.
3. Irrigation infrastructure damage. Principally irrigation water is aimed to reduce discrepancy water supply during
rainy and dry seasons. Inefficient use of water especially by farmers at the upper course near main irrigation channel causes difficulties for paddy fields located at
the lower course to obtain water. The motivation factors are disobedience to planting time of appropriate
classification of paddy field; inefficient water use that is allocated for other paddy field classification and infrastructure damage. Therefore, government
involvement to prevent problems by repairing infrastructure and improving farmer knowledge about the importance of water distribution should be done. It is
expected to minimize paddy field areas in Karawang district suffering from drought vulnerability as Karawang is one of the rice barns in Indonesia.
4.2. Web Development
Kategori