Status of Heavy Metal Concentration in Water of Citarum River at Selected Sites in Bandung Residence
2. Materials and Methods
The study was conducted in the watershed of Krueng Peusangan which had 12 sub watersheds. Part of the area is situated within the administrative area of Central Aceh District on the upstream, in the middle of Bener Meuriah District, and Bireuen District downstream. Geographically, the watershed of Krueng Peusangan is in the top position (Upper) 5o16'34'' NL - 96o27'12 "E, and the bottom (Lower) 4o30'38"N-97o02'40"L, with an area of 2557.80 km2 (Fig. 1).
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Page | 123 Precipitation data for the upstream and downstream areas were derived from Stations of Meteorology and Climatology of Lhokseumawe and Bebesan Takengon. Although Krueng Peusangan watershed consists of 12 sub watershed, they are available and operated only at (two) river water monitoring stations called Teumbo (04o59’6.9” NL and 96o4’46.6”
EL) and Nareh Stations ( 04o34’34.8” NL and 96o48’52.8”EL), for the period of 2008-2012. Whereas, three other stations are now no longer functioned so that the available data were only from the year of 1987-1996.9 ( Kr. Seumpo (5o04’04’’
North Longitude (NL) and 96o42’46’’ East Longitude (EL) , (B) Kp. Simpang Jaya (05o07’04’’ NL and 96o40’54’’
EL) , (C) Ds. Beukah (05o10’ NL and 96o48’04” EL).
River flow was a sensitive parameter to the changes of watershed components. In this research, daily flow data were necessary to establish river flow hydrograph. The data were obtained from the equation that described the relationship between discharge with the water level. The data as used in this study were stream flow data issued by the Office of Water Resources and Headquarter of Krueng Aceh Watershed, Aceh Province (NAD).
Figure 1. Watershed and Sub Watershed of Krueng Peusangan
2.1. Water Yield based Mock Model
Mock models transformed the rain-flow follows the principle of water balance to estimate the discharge a river.
This method assumes the rain that fell in the watershed will be partially lost as evapotranspiration; some will direct run-off and some will go into the ground as infiltration. If the capacity of soil moisture is exceeded, the water will flow downward due to the force of gravity as percolation to the saturated aquifer as ground water which is going out to the river as base flow. Precipitation will be transformed by the watershed system. Discharge in the river is the number of streams directly and low base flow [7]. The basic equation used in the model equations Mock was the water balance in the soil and ground water storage equation. The total structure of the Model Mock is shown in fig.
2 ([8]. Mock Model that the rate of water production at a watershed was found through the equation of
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Page | 124
𝐵𝐹 = 𝐼 − ∆𝑆 (1)
𝐷𝑅𝑂 = 𝑊𝑆 − 𝐼 (2)
𝑊𝑆 = 𝑃 − 𝐸𝑎 (3)
𝐼 = 𝑊𝑆. 𝐼𝑓 (4)
𝐼𝐺𝑊𝑆 = 𝐺𝑊𝑆𝐼−1 (5)
𝐺𝑊𝑆 = 𝐾(𝐼𝐺𝑊𝑆) + 0.5(1 + 𝐾)𝐼 (6)
∆𝑆 = 𝐺𝑊𝑆 − 𝐼𝐺𝑊𝑆 (7)
𝑄 = (𝐷𝑅𝑂 + 𝐵)𝐴 (8)
Figure 2. A representation of the Model Mock
2.2. Water Yield based Integrated NRCS and Base flow Model
Figure 3. Scheme of the Model Integrated NRCS and baseflow
NRCS could calculate runoff by introducing procedures with the curve number technique [9]. The determination of curve number value was based on the characteristics of land (kind of vegetation, land management, soil types (texture and infiltration rate). In addition to it, the value of CN (curve number) was also related to the condition of rainfall in which normal rainfall condition (condition II); if the rainfall was below normal condition, the
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Page | 125 factor of conversion for Condition I and if the rainfall condition was, the factor of condition III was used. The value of CN presented the condition of soil hydrology group, land cover, land management and hydrologic condition [10]. The determination of surface runoff based on SCS (Soil Conservation Service) method [11].
[12] …. has calculated that groundwater recharge by presenting the procedure to estimate groundwater recharge based on the modified soil moisture balance approach. A large number of streams and rivers that have base flow hydrographwere modeled by an exponential relation [13], [14] was as follow Fig. 3.
2.3. Validation Test
The accuracy/validation of measured discharge and simulated discharge the model formed was tested through the formula : [15], [16]
𝑅 = ∑𝑛𝑖=1(𝑄𝑖𝑜𝑏𝑠−𝑄𝑜𝑏𝑠𝑚𝑒𝑎𝑛)(𝑄𝑖𝑠𝑖𝑚−𝑄𝑠𝑖𝑚𝑚𝑒𝑎𝑛)
√∑𝑛𝑖=1(𝑄𝑖𝑜𝑏𝑠−𝑄𝑜𝑏𝑠𝑚𝑒𝑎𝑛)2(𝑄𝑖𝑠𝑖𝑚−𝑄𝑠𝑖𝑚𝑚𝑒𝑎𝑛)2
(9)
𝑅𝑆𝑅 =𝑆𝑇𝐷𝐸𝑉𝑅𝑀𝑆𝐸
𝑜𝑏𝑠= √∑ (𝑄𝑖𝑜𝑏𝑠−𝑄𝑖𝑠𝑖𝑚)
𝑛 2 𝑖=1
√∑𝑛𝑖−1(𝑄𝑖𝑜𝑏𝑠−𝑄𝑜𝑏𝑠𝑚𝑒𝑎𝑛)2
(10)
𝑁𝑆𝐸 = 1 − ∑ (𝑄𝑖𝑜𝑏𝑠−𝑄𝑖𝑠𝑖𝑚)
𝑛 2 𝑖=1
∑𝑛𝑖=1(𝑄𝑖𝑜𝑏𝑠−𝑄𝑖𝑚𝑒𝑎𝑛)2 (11)
3. Results and discussion
Year Month
1996 1995
1994 1993
1992
Jul Jan Jul
Jan Jul
Jan Jul
Jan Jul
Jan 160 140 120 100 80 60 40 20 0
Discharge (m3/s)
Simulated of discharge with ET Penman Simulated of disharge with ET elevation observed of discharge
Legend
Fig. 4 Comparison of Observed and Simulated discharge with Mock Model
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Page | 126 Land use with diverse vegetation and the amount of evaporation that differ between vegetation with the other watershed. Based on the method of Penman, potential evapotranspiration was influenced by the magnitude of the reflection coefficient. This coefficient depends on the existing vegetation in an area and has very close relation to land use in a watershed; all land use gives different reflection coefficient. In addition, discharge stimulated with Mock Model was also calculated based on evapotranspiration due to the difference in height (topography).
Simulated of discharge using Mock Model has been done to get parameters of model that was suitable with discharge observed. Discharge simulated at watershed of Krueng Peusangan was Krueng Beukah because this location was at downstream position. Comparison of discharge measurement values can be seen in fig. 4.
NRCS and base flow Integration Model is a model of daily discharge based on the application of simplified water balance model. Discharge is the volume of water generated in a watershed over time. Daily runoff calculations generated using the NRCS based on the condition of the area. This calculation was based on the retention parameter, initial abstraction, surface storage, interception, and infiltration prior to runoff, and daily rainfall (mm). Parameters are variables due to changes in soil type, land use, and soil moisture. [17] … showed that the 0.2 was a retention parameter which was not always the most suitable for the initial abstraction. However, for the location of this study, Curve number taken on the condition II that showed normal conditions.
In 1993, the annual rainfall at Krueng Peusangan watershed was 853.48 mm. After being measured, this 1993 rainfall provided the average daily river debit of 99.7 m3/second. The value of potential maximum retention (S) was 103.7 mm. The simulated debit obtained after the input data of rainfall, direct runoff, percolation, groundwater reserves, base flow was 130.41 m3/s. The result of simulation of estimating the debit of Krueng Peusangan watershed using the NRCS and Baseflow Integrated Model for 1993 is seen in Fig. 5.
Figure 5. Comparison of observed and simulated discharge using Integrated NRCS and Base flow Model in 1993
The simulated debit was taken at the measurement point of Kp. Beukah which is downstream of Krueng Peusangan watershed. The value of CN taken was belonged to the normal condition (II) for the simulation of its debit estimation. In 1993, The CN value was 71.This value was obtained in accordance with the condition of land use at Krueng Peusangan watershed. The increase of CN value showed that land conversion has occurred.
Therefore, it is necessary to make an effort to prepare a spatial concept emphasizing the integration of eco-hydrology, conservation of forest area in the upstream of Krueng Peusangan watershed, and conservation of water catchments areas in the centre and downstream of Krueng Peusangan watershed. This concept is useful as a synthesis review to support the sustainable watershed management planning beside the ability of this model to perform simulations based on mathematical approaches and physical assumptions.
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Page | 127 Model validation test has been done using (NSE) Nash-Sutcliffe efficiency, R (correlation coefficient), and RSR for point discharge measurements in Kp Beukah. Model validation results are shown in Table 2. NSE measures goodness of fit and close to unity if the simulations represent satisfactory observation. NSE clarified the picture of the difference of the observed values from time to time are counted for by the model [18]. If the efficiency was negative, the model predictions were worse than predictions made using the average of all observations. If close to one (1), then, the model was perfectly formed. Correlation the coefficient of variation values of the model was evaluated. It could reveal the strength and direction of a linear relationship between simulation and observation.
The square of the correlation coefficient (R) obtained coefficient of determination (r2). Difference between NSE and r2 was that the NSE could interpret the model in replicating the performance of the individual against the value generated models, while r2 did not explain it [17]. High values of r2 indicated less error variance, and typically values greater than 0.5 were considered acceptable [19], [20]. It was considered good if the validation criteria or limit the suitability of the result set has been reached. Overall, the result of validation test of the model showed that its performance was very good and satisfactory.
Table 2 Reported performance ratings
Model Year Model Validation
NSE performance RSR performance R r2
Mock with Penman Evapotranspiration
1992 0.840 very good 0.400 very good 0.740 0.548 1993 0.880 very good 0.210 very good 0.857 0.734
1994 0.740 good 0.420 very good 0.946 0.895
1995 0.830 very good 0.304 very good 0.730 0.533 1996 0.950 very good 0.320 very good 0.640 0.410
Mock with
topography evapotranspiration
1992 0.630 satisfactory 0.500 very good 0.800 0.640
1993 0.880 very good 0.600 good 0.873 0.762
1994 0.500 satisfactory 0.520 good 0.320 0.102 1995 0.790 very good 0.350 very good 0.700 0.490 1996 0.820 very good 0.480 very good 0.630 0.397
Integrated NRCS and base flow
1992 0.800 very good 0.220 very good 0.896 0.803 1993 0.590 satisfactory 0.320 very good 0.840 0.706 1994 0.580 satisfactory 0.330 very good 0.784 0.615 1995 0.630 satisfactory 0.310 very good 0.792 0.627
1996 0.670 good 0.210 very good 0.950 0.903
4. Conclusions
The results obtained for the availability of water by using a mock model evapotranspiration from the Penman formula was 804,192,989.26 m3/year. While the availability of water using NRCS integration model and base flow was 2,559,231,717.61 m3/year. Water availability of measurements is 911,510,715.74 m3/year. NRCS method can provide the accuracy of information on the process of land use runoff, evaporation and infiltration. While Mock models can calculate the value of the monthly direct runoff from precipitation, evapotranspiration, soil moisture and soil water storage. The result of validation test of the model showed that its performance was very good and satisfactory. But the results of the model validation test were Mock model that has better value than the NRCS integration with Base flow model.
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Page | 128 Acknoledgement
The research reported in this paper has been supported by Anugerah Sobat Bumi, Indonesia and DIKTI (Director General of Higher Education ministry of National Education Indonesia).
References
1. Li HP, Yang GS, Jin Y. Simulation of hydrological response of land use change in Taihu basin, Journal of Lake Sciences 2007; 19 (5):
537–543.
2. Price K. Effects of Watershed Topography, Soils, Land Use, And Climate on Base flow Hydrology in humid regions: A review, Progress in Physical Geography 2011; 35(4):465-492.
3. Cui X, Liu S, Wei X. Impacts of forest changes on hydrology: a case study of large watersheds in the upper reach of Yangtze River Basin Hydro. Earth Syst. Sci.2012; Discuss9-6507–6531.www.hydrol-earth-syst-sci-discuss.net/9/6507/2012/doi: 10. 5194 /hessd-9-6507-2012.
4. Lao YL, Lu XG, Wang L. A review on study methods of effect of land use and cover change on watershed hydrology. Wetland Science 2009;
7(1): 83–88.
5. INWRDAM. Decision Support System in the Field of Water Resources Planning And Management. Published on line in http://www.nic.gov.jo/
inwrdam/dss.htm1. March 12; 2001.
6. Pavoni, B, Voinov, A and Zhavora, N. Basin (Watershed) Approach As AMethodological Basis for Regional Decision Making And Management in the EX USSR.Published on line inhttp://helios.unive.it/%7Eintas/gaboart.htm1. March 12; 2001.
7. Mock FJ. Land Capability Apprasial Indonesia. United Nation Development Programmed, Food and Agriculture Organization the United Nations, Bogor, Indonesia; 1973.
8. Susanto S and Setyawan C. Assesment Model of Water Resources Conservation measures case study at upper watershed of Sempor and Wadaslintang .
9. Natural Resources Conservation Service (NRCS). Conservation Engineering Division, Technical Release 55 : Urban Hidrologi for Small Watershed, US Departement of Agriculture, Washington; 1986.
10. Chow VT, Maidment DR, Mays LW. Applied Hydrology. McGraw-Hill. International Edition: p.572; 1988.
11. Schwab GO, Frevert RK, Edminster TW, Barnes KK. Soil and water conservation engineering : (3rd Edition). John Wiley and Sons, New York, NY. 525. ISBN 0-471-03078-3; 1981.
12. Kumar CP. Estimation of ground water recharge due to rainfall by modelling of soil moisture movement. National Institute of Hydrology.
Technical Report No. TR-142. 1992;93: 66.
13. Martin GN. Characterization of simple exponential base flow recessions. Journal of Hydrology 1973; 12(1), p. 57-62.
14. Fetter CW. Applied hydrogeology. 4th. ed. Prentice Hall Publishing Company; 2001.
15. Nash JE, and Suteliffe JV, 1970 River flow forecasting through conceptual Models 1, a Discussion of Prnciples, J. Hydrol. 1970; 10(1):
282-290.
16. Moriasi DN, Arnold JG, Van Liew MW, Bingner RL, Harmel RD and Veith TL. Model Evaluation Guidelines for Systematic Quantification of Accuracy in Watershed Simulations, Jurnal American Society of Agricultural and Biological Engineers 2007; 50 (3): 885-900 ISSN 0001-2351.
17. Ponce VM and Hawkins RH.Runoff curve number: Has it reached maturity?Journal of Hydrology Engineering 1996;©ASCE ISSN 1084-0699/96/0001-0011-0019 ; vol 1(1):11-12.
18. Green CH, Tomer MD, Di Luzio M, Arnold JG. Hydrologic evaluation of the Soil and Water Assessment Tool for a large tile-drained watershed in Iowa. Transactions of ASABE 2006; 49(2):413-422.
19. Santhi C, Arnold JG, Williams JR, Dugas WA, Srinivasan R and Hauck LM. Validation of the SWAT model on a large river basin with point and nonpoint sources. J. American Water Resources Assoc. 2001; 37(5): 1169-1188
20. Van Liew MW, Veith TL, Bosch DD and Arnold JG. Suitability of SWAT for the conservation effects assessment project: A comparison on USDA-ARS experimental watersheds. J. Hydrologic Eng. 2007; 12(2): 173-189.
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