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4.1.2 Soil Characteristics
Generally, soil type in the study area was developed from volcanic material resulting from volcanic eruption. There are four soil characteristics that determine
erodibility level; texture, organic content, structure and permeability. The values of the characterizing parameters were determined from samplings in undisturbed and
disturbed area. Aside from that, the slope of the area was also measured. Figure 4.4 shows soil sampling and slope measurement. The site of soil sampling was
determined based on soil type map and elevation. The distribution of soil type and location of soil sampling is shown in figure 4.5.
Figure 4.4 Measurement and soil sampling
Figure 4.5 Soil map and location of soil sampling
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4.1.3 Climatology condition
Climatologic condition was derived from averaged monthly data from 2004 to 2008 on Nariwatie climate gauge. The gauge is located in the eastern of study
area and belongs to a plantation Company. This gauge recorded climatic parameters, such as temperature, rainfall, solar radiation, humidity, and wind
velocity. Table 4.1 shows monthly averaged data of climate condition in study area.
Based on daily climate data during 2004 - 2008, air temperature in Upper Cimanuk Catchment Area ranged from 14.4
C to 33.8
o
C, humidity ranged from 83.2 to 90.2, wind velocity ranged from 1.2 to 7.5 msecond, while Solar
radiation ranged from 12.49 to 50.4 mjm
-2
day. Table 4.1 Average climate during 2004 to 2008 in Upper Cimanuk
Catchment Area
Month Average
daily rainfall
mm Temperature
o
C Humidity
Wind Velocity
msec Solar
Radiation mjm
- 2
day January 17.6 25.0 87.2 3.1 22.6
February 21.2 24.5
87.0 3.1 21.6 March 21.4 25.0 88.1 2.6 30.8
April 21.4 25.1 88.6
2.7 31.9
May 16.2 24.9
87.9 2.2
32.5 June 11.2
24.0 87.8
2.3 41.2
July 10.4 23.3
86.9 3.6
40.2 August 6.4 23.2 85.6 4.2 44.1
September 14.0 23.9
86.3 4.9
39.5 October 17.0 24.6 86.8 4.6 39.1
November 16.0 25.4
88.2 3.5
26.1 December 22.8
24.8 89.4
2.6 25.6
Based on Schmidt and Fergusson classification, climate types of the study area belongs to B, C and D types. Type B is relatively wet area and can be found
in the southern region of UCCA. Type C is rather wet area and located in the middle part of study area. Type D, which is characterized by moderate condition,
is located in northern part of study area.
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Rainfall There are 13 rain gauges found around the study area. The gauges are
mostly located at downstream area and belong to The Public Works Department. The rainfall data is also mostly discontinuous as shown in Table 4.2. Several
gauges have continuous data such as Bayongbong 1990-2007, Chinchona and Paseh 1990-2004, Leles 1998-2008, and Tarogong 1997-2006. Figure 4.6
shows distribution of rain gauge location in study area. Considering the availability of precipitation and landuse data, the simulation was done using the data from year
2005. Table 4.2 Availability of precipitation data in UCCA.
No Gauge
90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 Qty
1 Bayongbong
1 1
1 1
1 1
1 1
1 1
1 1
1 1
1 1
1 1
18 2
Leuwidaun 1
1 2
3 Dayehmanggung
1 1
4 Sindanglaya
1 1
5 Malongbong
1 1
1 1
1 1
1 7
6 Cibeureum
1 1
1 1
1 1
1 7
7 Cikajang
1 1
1 1
1 1
6 8
Garut 1
1 1
1 4
10 Chinchona
1 1
1 1
1 1
1 1
1 1
1 1
1 1
1 15
11 Paseh
1 1
1 1
1 1
1 1
1 1
1 1
1 1
1 15
12 Leles
1 1
1 1
1 1
1 1
1 1
1 11
13 Tarogong
1 1
1 1
1 1
1 1
1 9
Generally, rainfall intensity in the study area is high whereas its duration is short. This intensity is caused by increasing temperature leaving land surface in the
afternoon. Aside from that condition, rainfall in UCCA is influenced by global climate which is identified by low intensity and long duration. Mostly, rainy season
happens in November to April or during west monsoon wind season. Figure 4.7 shows average precipitation at four rain gauges in UCCA; Tarogong located in
downstream of catchment area, Bayongbong located in midstream area and Nariwate and Cikajang in upstream area. The location of all rain gauges is shown
in Figure 4.6. The figure shows that Tarogong and Bayongbong have similar data but Cikajang and Nariwate is higher. All of the four rain gauges show that the rainy
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season occurs from October to April, whereas according to the research of Gandasasmita in 2001 the rainy season occurred from November to April. This
difference is caused by different outlets of catchment area.
Figure 4.6 Distribution of Rain gauge, climate and discharge gauge
Figure 4.7 Average daily precipitations each month in Upper Cimanuk Catchment Area.
0.00 5.00
10.00 15.00
20.00
Jan Feb Mar Apr May Jun
Jul Aug Sep
Oct Nov Dec
P mm
Tarogong Bayongbong
Cikajang Nariwate
Average
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Figure 4.8 shows monthly precipitation in Bayongbong rainfall gauge where total of rainfall in year 2005 is 2,106 mm this number will compared with
result of SWAT simulation. Figure 4.9 shows daily precipitation in Bayongbong rainfall gauge, the figure present stability of rainfall data during 1990 to 2006.
Figure 4.8 Monthly precipitations in Bayongbong Rain Gauge
Figure 4.9 Daily precipitations in Bayongbong Rain Gauge.
0.0 50.0
100.0 150.0
200.0 250.0
300.0 350.0
400.0 450.0
P mm
20 40
60 80
100 120
140
P mm
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4.1.4 Hydrologic condition