Study on Effects of Land Use Change. on Hydrological Characteristic of Watersheds ADB. IN THE 6 CI's RIVER BASIN TERRITORY - PACKAGE B DRAFT REPORT

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1 ADB TA 7189-INO: INSTITUTIONAL STRENGTHENING FOR INTEGRATED WATER RESOURCES MANAGEMENT (IWRM) IN THE 6 CI's RIVER BASIN TERRITORY - PACKAGE B DRAFT REPORT Study on Effects of Land Use Change on Hydrological Characteristic of Watersheds November 212 Prepared by: CENTER FOR WATER RESOURCES RESEARCH AND DEVELOPMENT

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3 FINAL REPORT STUDY ON EFFECTS OF LAND USE CHANGES ON HYDROLOGICAL CHARACTERISTICS OF WATERSHEDS IN THE 6 CIS RIVER BASIN TERITORY Research Center for Water Resources i

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5 TABLE OF CONTENTS 1 INTRODUCTION Background Objectives Expected Results (outputs/outcomes): Methodology CALIBRATION OF THE MODEL Sacramento Model Data Availability for Callibration Ciujung River Ciliwung River Calibration for Low Flow Time-Series Calibration for Flood Event Citarum River LOW FLOW ANALYSIS Ciujung River Ciliwung River Citarum River FLOOD ANALYSIS Simulation for the year of 22 and Recalibrating the deforestation case CONCLUDING REMARKS REFERENCES Research Center for Water Resources 2

6 TABLE OF FIGURES Figure 1 Concept of Sacramento Model (Burnash, 1973)... 8 Figure 2 Model Component (Burnash, 1973)... 9 Figure 3 Availability of half-monthly river discharges data Figure 4 Ciujung-Kragilan using BTA-155 Sacramento parameter Figure 5 Ciujung-Kragilan using modified Sacramento parameter Figure 6 Sacramento parameter from BTA-155 study Figure 7 Improved Sacramento parameter modified in this study Figure 8 Ciujung-Rangkasbitung using Sacramento parameter from BTA-155 Study Figure 9 Ciujung-Rangkasbitung using improved Sacramento parameter Figure 1 Land use change of forest and urban area in Ciliwung-Katulampa catchment area Figure 11 Ciliwung-Katulampa using Sacramento parameter from BTA Figure 12 Ciliwung-Katulampa using improved Sacramento parameter Figure 13 Ciliwung Katulampa calibrated for around the year of Figure 14 Ciliwung-Katulampa calibrated for around the year of Figure 15 Ciliwung-Katulampa calibrated for around the year of Figure 16 Hourly rainfall at Citeko and river discharge Ciliwung at Katulampa Figure 17 Katulampa Calibration February Figure 18 Sacramento Parameter for February Figure 19 Land use change of forest and urban area in Citarum River Basin Figure 2 Cigulung-Maribaya using the BTA-155 parameter for the year of Figure 21 Cigulung-Maribaya calibrated for the year of Figure 22 Sacramento parameter for Cigulung-Maribaya Figure 23 Ciujung-Kragilan using improved parameter for Figure 24 Ciujung Rangkasbitung using improved parameters for Figure 25 Simulation of Ciliwung-Katulampa using BTA-155 parameter for the year of Figure 26 Simulation of Ciliwung-Katulampa using improved parameter for the year of Figure 27 Cigulung Maribaya simulation for the year of Figure 28 Simulation of Ciliwung-Katulampa 19 January 15 February 22 using parameter of Figure 29 Simulation of Ciliwung-Katulampa 8 January 26 February 26 using parameter of Figure 3 Ciliwung-Katulampa 19 January 15 February 22 recalibrated Figure 31 Ciliwung-Katulampa 8 January 26 February 26 recalibrated... 3 Research Center for Water Resources 3

7 TABLE OF TABLES Table 1 Sacramento Parameter... 1 Table 2 List of Discharge Stations for Sacramento Calibration Research Center for Water Resources 4

8 GLOSSARY 6 Cis RBT River Basin territory covering Cidanau, Ciujung, Cidurian + Ciliwung, Cisadane + Citarum Balai PDAS Regional Board for management of River Basins (under Ministry of Forestry) Balai PSDA Provincial River Basin Management Board BBWS Greater River Basin Territory Board (Balai Besar Wilayah Sungai), at MPW level BTA 155 Cisadane - Cimanuk Integrated Water Resources Development project Strategic WRM Planning project in Indonesia ( ) BWRMP 1) Basin Water Resources Management Plan (Rencana) 2) Project for formulation of BWRMP (21 24) BWRP Basin Water Resources Planning ( , later changed to BWRMP) DGWR Directorate General for Water Resources at MPW DMI Domestic, Municipal and Industrial (water demand) FEWS\HYMOS Hydrological data processing system based on Flood Early Warning System FHM Flood Hazard Mapping, component under Jakarta Flood Management (27 21) GIS Geographic Information System GOI Government of Indonesia IWRM Integrated Water Resources Management JABOTABEK Area comprising Jakarta, Bogor, Tangerang, Bekasi. Later extended with Depok to become JABODETABEK and later also included Puncak and Cianjur in JABODETABEKPUNJUR JWRMS JABOTABEK WRM Study MIS Management Information System MPW Ministry of Public Works PSDA WRM PTPA Present form of Water Resources Council at Provincial Level PusAir Agency for Research and Development in Water Resources, under MPW RBT River Basin Territory (Wilayah Sungai, WS) RIBASIM River Basin Simulation Model, Decision Support System for WR planning /management Research Center for Water Resources 5

9 1 INTRODUCTION 1.1 Background The effect of changes in land use on hydrological characteristics of low and high discharges have been widely assumed to imply that decreasing vegetative cover would result in lower base flow during dry season and increasing flood discharges after storms. However, no quantitative data have been collected to confirm these assumptions, and information that correlates the land use change and the changing of hydrological properties is still based on hypotheses. Adequate water resources management requires confirmation of this kind of relationships to assess the relative benefit of various conservation strategies. In component B.2 of the 6 Cis Project, various strategies for zoning will be assessed. Therefore it is considered necessary to verify the assumed effect of changing land use, especially the change from rural to urban area and its related decrease in vegetative cover, concerning low flows and flood discharges. The RIBASIM model uses the Sacramento model for establishment of rainfall-runoff relationships. However, the model assumes values for several parameters based on experience from the past, and the effect of changes from a rural area to an urban area are not yet verified. Therefore one or two areas with sufficient data to simulate flows based on sufficient time series to re-calibrate the rainfall runoff relationship is needed. After assessment of the new values for the parameters to reflect the changes in land use, one can extrapolate this relationship with the specific factors for the other basins in 6 Cis. This is part of the standard practice when simulating with RIBASIM. This has also been discussed in the 6 Cis Inception Report on page 29, under point 2, and in the paragraph starting with " The Sacramento rainfall-run-off...". There are two stations in the 6 Cis area with sufficient time series for hourly and daily discharges: Katulampa in the Ciliwung river just upstream Bogor and Nanjung in the Citarum river just upstream Saguling. The catchment of Katulampa (app 15 km2) represents a good example of changes in land use from rural to urban area. The catchment of Nanjung is much larger (app 15 km2), and therefore it is not realistic to relate the changes to changes in land use, since also river normalization has taken place, and many other factors may have an influence. Therefore Nanjung is not proposed for this study. In order to have a comparison from another basin it is necessary to look for in data base for other suitable areas, and there might be from hourly discharge data for Brantas and Bengawan Solo. Using a second site with sufficient data a more reliable estimation can be made of the land use - runoff relationship, which will improve the accuracy of extrapolation to other catchments. The extra costs for the extra site are not much, because the main problem is to develop the methodology. Data collection and validation for rainfall data and discharges has been done, and they are ready for use. Data for land use changes are also available through available land use mapping (Geocover 199, 2, 27). What has to be done now is to identify the land use changes for the Katulampa catchment, and relate this to various series of rainfall and discharge data, in order to assess the most likely changes for the applicable rainfall-runoff parameters. Only in this way we can get a better idea about the correlation between the land use and the runoff data, which can be extrapolated to other areas. Research Center for Water Resources 6

10 1.2 Objectives Determine quantitatively the effect of land use changes on low flow and flood discharge for some hydrological stations in the area of 6 Cis. This will be done by selecting two suitable river discharge gauging stations with adequate information concerning river discharges and simultaneous changes in land use for the catchment upstream of the river gauging station. 1.3 Expected Results (outputs/outcomes): Correlation between the land use change and the change in low flow and flood discharge. Model parameter changes best reflecting the changes in condition of land use. 1.4 Methodology The methodology is as follows: - Rainfall-runoff analysis using Sacramento model and other methodologies applied in HYMOS and RIBASIM, - Comparing the measured discharges with the results of rainfall-runoff analysis using the same parameter for the present condition, and examine the differences of the low flow and the flood discharge before and after the land use change. - Assess the parameters that better reflect the measured values - Another approach is to calibrate the present condition and examine the parameters that have to be changed to fit the present condition. Research Center for Water Resources 7

11 2 CALIBRATION OF THE MODEL 2.1 Sacramento Model In the simulation of the runoff process by the Sacramento model a distinction is made between the land phase and the channel phase. The land phase is represented by an explicit moisture accounting lumped parameter model. The catchment area is divided into one or more segments discharging to the main channels. Within every segment areal homogeneity with respect to rainfall and basin characteristics is assumed. The distance is not explicitly treated in the simulation process as is time. In this respect the lumped approach deviates from the distributed catchment models. The concept of the Sacramento model with the major storages and flow components is shown in Figure 1 (Burnash et al, 1973). The components of the model are shown in Figure 2. In this figure also the names of the components used in the menu are indicated. The components of the model, their working and their interaction are elaborated below. Note that for the storages a distinction is made between capacity (indicated with the letter M at the end of the name) and actual content (indicated with a C at the end). Figure 1 Concept of Sacramento Model (Burnash, 1973) Research Center for Water Resources 8

12 Figure 2 Model Component (Burnash, 1973) There are 17 Sacramento parameters, which can be classified as direct runoff parameter, upper soil moisture parameter, percolation parameter, and lower zone parameter. Direct Runoff Parameter PCTIM: permanent impervious fraction ADIMP: additional impervious fraction SARVA: fraction covered by streams, lakes, etc. Upper Soil Moisture Zone Parameter UZTWM: Upper Zone Tension Water reservoir capacity UZFWM: Upper Zone Free Water reservoir capacity UZK: Upper Zone lateral drainage rate Percolation Parameter ZPERC: proportional increase percolation from saturated to dry condition REXP: exponent in percolation demand equation Lower Zone Parameter LZTWM: Lower Zone Tension Water reservoir capacity LZFPM: Lower Zone Free Primary reservoir capacity LZFSM: Lower Zone Free Supplementary reservoir capacity LZPK: drainage rate of Lower Zone Primary reservoir LZSK: drainage rate of Lower Zone Supplementary reservoir PFREE: fraction percolation water directly to lower zone free RSERV: fraction of lower zone free not available for transpiration) SIDE: ratio of unobserved to observed base-flow SSOUT: fixed rate of flow lost from channel Research Center for Water Resources 9

13 In the BTA-155 Project (Cisadane-Cimanuk Integrated Water Resources Development), Sacramento model has been calibrated, resulting one set of parameter for the all river basins in the Northern part of West Java. Using this parameter, half-monthly runoff is generated from rainfall time-series for all water districts. It should be noted that this parameter is recalibrated for Bengawan Solo River Basin in the study of BTA-155 Phase II. The lists of parameters are as follows. Table 1 Sacramento Parameter Parameter BTA-155 Bengawan Solo Suggested Storage parameters 1. UZTWM : UZFWM : LZTWM : LZFSM : LZFPM : 3 3 Initial storage: 6. UZTWC : UZFWC : LZTWC : LZFWC : LZFPC : Other parameters: 11. UZK : LZSK : LZPK : ZPERC : 1 3 >> REXP : PFREE : RSERV : PCTIM : 19. ADIMP : 2. SARVA : 21. SIDE : 22. SSOUT : Research Center for Water Resources 1

14 Discharge historical [m3/s] Effects of Land Use Changes 2.2 Data Availability for Callibration In the 6 Cis River Basin Territory, effort has been made to collect catchment area having pairs of rainfall and runoff data, preferably small catchment area, and has been calibrated from the BTA-155 Project (Puslitbang Pengairan and Delft Hydraulics, 1989). Ciujung river at Rangkasbitung and Kragilan are river discharge stations that were used in the BTA-155 Project to calibrate the Sacramento parameter. Two additional stations having small catchments in this study: Ciliwung-Katulampa and Cigulung-Maribaya are listed in the following table, while the availability of the river discharge data is presented in the bar chart in Figure 3. Table 2 List of Discharge Stations for Sacramento Calibration Station Name Station Code CA (km2) BTA-155 Water Districts / Period of Data Rainfall Stations Ciujung-Kragilan ,562.7 D11, 12, 13, 14, 15, Ciujung-Rangkasbitung ,363.9 D11, 12, 13, 14, 15, Ciliwung-Katulampa Citeko Cigulung-Maribaya D31 (Upper Citarum) Graph of Discharge historical CigMaribaya QH Katulampa QH Kragilan QH Rangjasbt QH Figure 3 Availability of half-monthly river discharges data Using the same river discharges and rainfall data in the BTA-155 Project (Delft Hydraulics and Puslitbang Pengairan, 1989), in this study, the parameter of Sacramento Model is recalibrated using the same rainfall and runoff data in the BTA-155 Project which halfmonthly data is available from the year of 1951 until The parameter obtained in the calibration phase will be applied in the rainfall-runoff simulation of the recent rainfall and runoff data. Research Center for Water Resources 11

15 2.3 Ciujung River In Ciujung River, there are two river gauging stations calibrated in the BTA-155 project: Kragilan and Rangkasbitung (Figure 4 and Figure 8). This study recalibrated the parameter, and produces better results in Figure 5 and Figure 9. The Sacramento parameter has been modified from Figure 6 into Figure Dec 13 :: 1971 Dec 13 :: 1973 Dec 12 :: 1975 Dec 12 :: 1969 Jan 1 : Dec 1 : QS_Segment_1 QM_Segment_ Dec 11 :: Figure 4 Ciujung-Kragilan using BTA-155 Sacramento parameter Dec 13 :: 1971 Dec 13 :: 1973 Dec 12 :: 1975 Dec 12 :: 1969 Jan 1 : Dec 1 : QS_Segment_1 QM_Segment_ Dec 11 :: Figure 5 Ciujung-Kragilan using modified Sacramento parameter Research Center for Water Resources 12

16 Figure 6 Sacramento parameter from BTA-155 study Figure 7 Improved Sacramento parameter modified in this study Research Center for Water Resources 13

17 Good low flow modeling Dec 13 :: 1971 Dec 13 :: 1973 Dec 12 :: 1975 Dec 12 :: 1969 Jan 1 : Dec 1 : QS_Segment_1 QM_Segment_ Dec 11 :: Figure 8 Ciujung-Rangkasbitung using Sacramento parameter from BTA-155 Study Good low flow modeling Dec 13 :: 1971 Dec 13 :: 1973 Dec 12 :: 1975 Dec 12 :: 1969 Jan 1 : Dec 1 : QS_Segment_1 QM_Segment_ Dec 11 :: Figure 9 Ciujung-Rangkasbitung using improved Sacramento parameter From Figure 8 and Figure 9, indicate that there is no reason to change the parameters for the new situation. Both set of BTA-155 parameter and improved parameter produce the same good result for present condition. Research Center for Water Resources 14

18 2.4 Ciliwung River Ciliwung River is flowing through West Java Province and Jakarta Special Province. Katulampa river gauging station is situated at the upper part of Ciliwung River, having catchment area of 15 km 2. An automatic rainfall station Citeko is situated in the catchment area of Katulampa River Gauging Station. Daily river discharges and daily rainfall data from the year of are obtained from Research Center for Water Resources. Rating curve of the river discharges is based on the work of Ogink (27) and Ogink (28). The land use change of forest and urban area in the upper Katulampa river gauging station is obtained from satellite image interpretation by Institutional Strengthening for IWRM in the 6 Ci's River Basin Territory (package B) Project, for the year of 2, 23, 27 and 29 as shown in Figure 1. This figure present the percentage of forest that is decreasing from 58.8% in the year of 2 to 18.2% in 27, but little increase to 22.4% in the last two years of 29. On the other hand the urban area is increasing from.2% in the year of 2 to 7.2% in 29 7.% 6.% 58.8% 5.% 4.% 3.% 2.% 21.5% 18.2% 22.4% 1.% 5.3% 5.8% 7.2%.2%.% Year Forest Urban Figure 1 Land use change of forest and urban area in Ciliwung-Katulampa catchment area Research Center for Water Resources 15

19 2.4.1 Calibration for Low Flow Time-Series Calibration for Ciliwung-Katulampa is carried out from the year of 199 to The calibration using the BTA-155 parameter and rainfall station Citeko is presented in Figure 11 shows good fit between the model and the observed data, especially around the year of Dec 8 :: 1991 Dec 8 :: Good fit of low flow 1992 Dec 7 :: 1993 Dec 7 :: 1994 Dec 7 :: 1995 Dec 7 :: 199 Jan 1 : Dec 1 : QS_Segment_1 QM_Segment_ Dec 6 :: 1997 Dec 6 :: Figure 11 Ciliwung-Katulampa using Sacramento parameter from BTA-155 Using the same set of Katulampa discharge and Citeko rainfall station, calibraton using improved Sacramento parameter, presented in Figure 12 is also give good fit, especially for around the year of Good fit of low flow 199 Dec 8 :: 1991 Dec 8 :: 1992 Dec 7 :: 1993 Dec 7 :: 1994 Dec 7 :: 1995 Dec 7 :: 199 Jan 1 : Dec 1 : QS_Segment_1 QM_Segment_ Dec 6 :: 1997 Dec 6 :: Figure 12 Ciliwung-Katulampa using improved Sacramento parameter This fact shows that the BTA-155 parameter is good for calibration in the period of BTA- 155 ( ) while the improved parameter is for more recent period. Research Center for Water Resources 16

20 Discharge historical [m3/s] Discharge historical [m3/s] Effects of Land Use Changes Figure 13 show the result of calibration for the period of , give fit for this period as well as period of 23-26, and over estimate for the period of This means that in the period of , parameter of the model related to land use and land cover has changed. This set of changed parameter that fit in this period can be used for the scenario of decreasing forest and increasing urban area. As a logical consequence this set of urban parameter would give under estimate for forest land cover condition QS_Segment_1 QM_Segment_1 Figure 13 Ciliwung Katulampa calibrated for around the year of QS_Segment_1 QM_Segment_1 Figure 14 Ciliwung-Katulampa calibrated for around the year of 1997 Research Center for Water Resources 17

21 Discharge historical [m3/s] Effects of Land Use Changes 7 Graph of Discharge historical QS_Segment_1 QM_Segment_1 Figure 15 Ciliwung-Katulampa calibrated for around the year of 23 Research Center for Water Resources 18

22 2.4.2 Calibration for Flood Event The hourly time step should be applied for analysing the effect of land use change to flood hydrograph. Until now it is found that only Ciliwung-Katulampa gauging station has relatively small catchment area, and sufficient hourly rainfall and corresponding discharge data. The hourly available discharge of Ciliwung River at Katulampa is from the year of 1996 to 28, while the hourly rainfall is from Citeko from the year of Both data was obtained from FHM Project, and verified by Ogink (27) and Ogink (28). There are also hourly discharge data from Tideda database Pusair from the year of 1996 until Feb 2 :: 1996 Feb 5 :: 1996 Feb 8 :: 1996 Feb 11 :: 1996 Feb 14 :: 1996 Feb 17 :: 1996 Feb 2 :: 1996 Feb 2 : Feb 26 22:58 CITEKO PH KATULAMPA1 QH 1996 Feb 23 :: 1996 Feb 26 :: Figure 16 Hourly rainfall at Citeko and river discharge Ciliwung at Katulampa The hourly rainfall at Citeko and river discharges of Ciliwung at Katulampa for February 1996 presented in Figure 16 shows timing error. The rainfall appear about 24 hours after the flooding happened. To overcome this problem, a backward shifting of 24 hours is applied for rainfall of Citeko in February The calibration results for Katulampa has been carried on for flood event on February 1996, and presented in the following figure. It shows relatively good fit between model and the observation data, especially in the peak flow. The next figure shows the Sacramento parameters for this calibration process, Research Center for Water Resources 19

23 Feb 2 :: 1996 Feb 5 :: 1996 Feb 8 :: 1996 Feb 11 :: 1996 Feb 14 :: 1996 Feb 17 :: 1996 Feb 2 :: 1996 Feb 2 : Feb 25 22:58 QS_Segment_1 QM_Segment_ Feb 23 :: Figure 17 Katulampa Calibration February 1996 Figure 18 Sacramento Parameter for February 1996 Research Center for Water Resources 2

24 2.5 Citarum River Cigulung River is a tributary of Citarum River, and river gauging station Cigulung- Maribaya is having small catchment area of 26 km2, situated near tourism object of Maribaya waterfall, which its upper catchment suffering land use changes into human settlement. There is no data available on the rate of change in this region, but data for the whole Citarum river basin might give impression on the land use change in this site. In Citarum basin, the land use change data from Bappeda Jawa Barat is presented in following figure. The forest cover is decreasing from 32.4 % in the year of 1994 to 9.3% in 29, conversely the urban area increasing from 1.9% in 1994 to 26.1% in 29. The decreasing forest is high during period in the year % 32.4% 3.% 26.1% 25.% 2.% 15.% 12.1% 11.3% 1.% 9.3% 5.% 1.9% 2.4% 2.7%.% Year Forest Urban Figure 19 Land use change of forest and urban area in Citarum River Basin In Cigulung-Maribaya river gauging station, if the BTA-155 parameter is applied, the model gives underestimate low flow and over estimated peak flow (Figure 2). This means that the model expect the catchment area which is worse than in reality, drought in the dry season and flooding in the wet season. Therefore the Sacramento parameter can not be generalized for all catchment area in the 6 Cis. The calibrated model for the periode of during high decrease of forest in year of is presented in Figure 21. It shows good fit, much better than BTA-155 parameter. Research Center for Water Resources 21

25 Dec 9 :: 1987 Dec 9 :: 1989 Dec 8 :: 1991 Dec 8 :: 1993 Dec 7 :: 1995 Dec 7 :: 1985 Jan 1 : - 2 Nov 1 : QS_Segment_1 QM_Segment_ Dec 6 :: 1999 Dec 6 :: Figure 2 Cigulung-Maribaya using the BTA-155 parameter for the year of Dec 9 :: 1987 Dec 9 :: 1989 Dec 8 :: 1991 Dec 8 :: 1993 Dec 7 :: 1995 Dec 7 :: 1985 Jan 1 : - 2 Nov 1 : QS_Segment_1 QM_Segment_ Dec 6 :: 1999 Dec 6 :: Figure 21 Cigulung-Maribaya calibrated for the year of Research Center for Water Resources 22

26 Figure 22 Sacramento parameter for Cigulung-Maribaya Research Center for Water Resources 23

27 Time series Effects of Land Use Changes 3 LOW FLOW ANALYSIS The main purpose of the low flow analysis in this study is to provide the rainfall-runoff parameter for input of simulation model Ribasim, and if necessary improve the parameter of the BTA-155 period from the year of , to accommodate the land use change effect. Based on the irrigation cycle, the time-step for simulation is half-monthly. 3.1 Ciujung River The following two figures are showing the Sacramento simulation of Ciujung-Kragilan and Ciujung-Rangkasbitung for the year of Kragilan station in Figure 23 shows that the past Sacramento parameter still gives good fit to the recent data. The same result also applied to Rangkasbitung station, although the model gives underestimate discharges for some years. 1,5 1, 95 9 Time Series Time QS_Segment_1 QM_Segment_1 Figure 23 Ciujung-Kragilan using improved parameter for Research Center for Water Resources 24

28 Time series Effects of Land Use Changes Time Series Time QS_Segment_1 QM_Segment_1 Figure 24 Ciujung Rangkasbitung using improved parameters for Research Center for Water Resources 25

29 3.2 Ciliwung River The low flow simulation for Ciliwung-Katulampa is carried out for the year of 1999 to 26, a period with low forest fraction. The result of simulation using BTA-155 parameter is presented in Figure 25. No general pattern exists. It shows over estimate of low flow for the year of 2 but under estimate for the year of 24 and Dec 6 :: 2 Dec 5 :: 21 Dec 5 :: 22 Dec 5 :: 23 Dec 5 :: QS_Segment_1 QM_Segment_1 24 Dec 4 :: 25 Dec 4 :: Figure 25 Simulation of Ciliwung-Katulampa using BTA-155 parameter for the year of The simulation using improved parameter, presented in Figure 26 shows similar result with the simulation using BTA-155 parameter as in previous figure. The difference is so not clear, however the simulation result using improved parameter seems to be a little lower than using BTA-155 parameter Dec 6 :: 2 Dec 5 :: 21 Dec 5 :: 22 Dec 5 :: 23 Dec 5 :: 1999 Jan 1 : - 26 Dec 1 : QS_Segment_1 QM_Segment_1 24 Dec 4 :: 25 Dec 4 :: Figure 26 Simulation of Ciliwung-Katulampa using improved parameter for the year of Research Center for Water Resources 26

30 3.3 Citarum River Simulation result of Cigulung River at Maribaya for the year of using the calibrated parameter for the year of is presented in Figure 27. It shows consistently that the low flow of the simulated model is always higher than the observed, in line with the high deforestation. In other word, the model expect the observed data to be higher than in reality. The magnitude of decreasing low flow is in between (in 24) to 75% (in 23), with the average decreasing is around 25% Dec 5 :: 22 Dec 5 :: 23 Dec 5 :: 24 Dec 4 :: 21 Jan 1 : - 26 Nov 1 : QS_Segment_1 QM_Segment_1 25 Dec 4 :: Figure 27 Cigulung Maribaya simulation for the year of Research Center for Water Resources 27

31 4 FLOOD ANALYSIS Using the same Hymos Sacramento parameter calibrated in the Chapter 2, the model is run using the observed rainfall and discharge in the year 22 and 26. If the model and observed can be fitted using this parameter, it means that no change in catchment characteristic from 1996 to 22 and 26. If it doesn t fit then it is caused by land use change. 4.1 Simulation for the year of 22 and 26 For the year of 22, 19 January 15 February, in Figure 28 the Sacramento model simulated using 1996 parameter only expecting flood of about 6 m3/s and 4 m3/s. However in reality the observed flood peaks are much higher, 17 m3/s and 24 m3/s, It is about 4 times higher Jan 19 :: 22 Jan 22 :: 22 Jan 25 :: 22 Jan 28 :: 22 Jan 31 :: 22 Feb 3 :: 22 Feb 6 :: 22 Feb 9 :: 22 Jan 19 : - 22 Feb 14 22:58 QS_Segment_1 QM_Segment_1 22 Feb 12 :: Figure 28 Simulation of Ciliwung-Katulampa 19 January 15 February 22 using parameter of 1996 For the year of 26, 8 January to 26 February, in Figure 29 the Sacramento model using 1996 parameter only expect flood of about 7 m3/s and 12 m3/s. However in reality the observed flood peaks are much higher than expected in the model, as high as 13 m3/s and 27 m3/s, or about twice higher. Both simulation cases for the year of 22 and 26 give consistent result, that the observed high flow is higher than expected, by a factor of around twice to 4 times. It is noted that the forest fraction in 1996 is 6%, and deforestation leaves remaining forest fraction of only 2% for the year of 22 and 26. At the same time the urban area is increasing from only.2% in the year of 1996 to about 5% in the year of 22 and 26. Research Center for Water Resources 28

32 Jan 14 :: 26 Jan 21 :: 26 Jan 28 :: 26 Feb 4 :: 26 Feb 11 :: 26 Jan 8 : - 26 Feb 26 22:58 QS_Segment_1 QM_Segment_1 26 Feb 18 :: 26 Feb 25 :: Figure 29 Simulation of Ciliwung-Katulampa 8 January 26 February 26 using parameter of Recalibrating the deforestation case Figure 3 and Figure 31 showing an attempt to fit the model with the observed flow for the year of 22 and 26 respectively. The Sacramento parameter to be changed is LZTW (Lower Zone Tension Water) from 3 to 3, which means lowering the capacity of soil to hold the water Jan 19 :: 22 Jan 22 :: 22 Jan 25 :: 22 Jan 28 :: 22 Jan 31 :: 22 Feb 3 :: 22 Feb 6 :: 22 Feb 9 :: 22 Feb 12 :: 22 Feb 15 :: 22 Jan 19 : - 22 Feb 15 22:58 QS_Segment_1 QM_Segment_1 Figure 3 Ciliwung-Katulampa 19 January 15 February 22 recalibrated Research Center for Water Resources 29

33 Jan 14 :: 26 Jan 21 :: 26 Jan 28 :: 26 Feb 4 :: 26 Feb 11 :: 26 Jan 8 : - 26 Feb 26 22:58 QS_Segment_1 QM_Segment_1 26 Feb 18 :: 26 Feb 25 :: Figure 31 Ciliwung-Katulampa 8 January 26 February 26 recalibrated Research Center for Water Resources 3

34 5 CONCLUDING REMARKS 1) This study has developed an improved parameter from BTA-155 parameter for input of DSS-Ribasim. 2) No differences in low flow for Ciujung, and Ciliwung River. The parameter from the BTA-155 from , can be used for the recent year in 25. In other words, generally we can use old parameter resulting from BTA-155 study, or the improved parameter in this study for generating flows in the 6 Ci river basin territory. 3) For Citarum, in small catchment tributary Cigulung-Maribaya, the BTA-155 parameter cannot be applied, the possible cause is because the condition of the catchment is better than expected, or better than the average catchment area in the 6 Cis area. A new parameter for Cigulung-Maribaya for the year of , representing good catchment is developed. The application of this parameter for recent year in 2-28 gives over estimate low flow by 25%, to be suspected in line with the deforestation in its catchment area. 4) Concerning flood flow analysis, land use change in the upstream catchment of Katulampa, forest change from 58% in the year of 2 into 22% in the year of 29, and at the same time increasing urban area from 58% in the year of 2 into 22% in the year of 29, has made increase of peak flow in the year of 22 and 26, at about 4 times compared with peak flow in ) Due to the limitation of the data availability, only Ciliwung-Katulampa for flood, and Ciliwung-Katulampa and Cigulung-Maribaya for low flow, we cannot yet generalize the predicted Sacramento parameter value for the deforestation catchment area. 6) To provide time-series of half-monthly runoff for all water district in 6 Cis area to DSS-Ribasim, it is recommended to make calibrations for some representative river gauging stations in each rivers, using the starting parameter value of BTA- 155 or the improved parameter developed in this study. REFERENCES 1. Burnash, R. J. C., Ferral, R. L., and R. A. McGuire, A Generalized Streamflow Simulation System, Conceptual Modeling for Digital Computers, United States Department of Commerce, National Weather Services. 2. Delft Hydraulics and Pusat Litbang Pengairan, BTA-155, Cisadane-Cimanuk Integrated Water Resources Development Study, Ministry of Public Works. 3. Ogink, H.J.M. (27), Discharge measuring stations, Jakarta Flood Hazard Management, Delft Hydraulics. 4. Ogink, H.J.M. (28), Hydrological data processing, floods of 27 and 28, Partner for Water and Deltares. 5. Van der Weert, Hydrological Condition in Indonesia, Delft Hydraulics. Research Center for Water Resources 31