Stream Flow fluctuations and Land Use Changes in Bandung Basin

1. Ida Narulita Research Center for Geotechnology Indonesian Institutes of Sciences (LIPI) Stream Flow fluctuations and Land Use Changes in Bandung Basin

2. Introduction • Study area • Methods • Results • Analyses • conclusion

3. Background Within several last decades floods and droughts happened almost every year, and getting more and more severe. On the other hand, some areas pose the problems of water scarcity. CHANGE IN HYDROLOGIC REGIME OF THE WATER SHED Causes: Rainfall pattern change Land Use / Land Cover Change FOTO: SOBIRIN 2005

4. Research objectives: • To gain a better understanding on the impact significance of changes of rainfall and land Use/land cover patterns on the watershed hydrologic regime.

5. Correlation analysis between rainfall depth and land use/land cover density to hydrologic regime • Rainfall: monthly depth (mm) • Land use/Land cover density: indexed by run off coefficient for each type of Land use/Land cover according to CN-NRCS methode • Hydrologic regime: Baseflow and highflow discharges changes Principal methods: Parameters

6. Data • Monthly Rainfall Data from 19 stations spread over the study area (Bandung Basin) for the period of 1986-2010 (25 years). • Hydrograph for the period 1980 - 2009 recorded at Nanjung AWLR station, the outlet of the Upper Citarum watershed. • Land use map of 1976, 1994, 1999, 2001, 2004 and 2008 of Bandung basin derived from satellite imageries (Landsat MSS, ETM satellite images +7 and Aster).

7. Study Area : Bandung Basin

8. Distribution of rainfall stations and discharge station at Bandung Basin

9. Methods • Monthly Isohyet Mapping: • Daily rainfall data collection • Data series correction by Double Mass Curve. • Selection of representative stations to determine regression equations between rainfall and elevation • isohyet map construction using the obtained regression equations Method

10. Regression Equation between Monthly Rainfall and Elevation of Northern Slope of Bandung Basin Method

11. Digital Topography Map Method

12. Satellite Imagery Processing for land cover mapping: case studi Bandung Basin 4 Scene Satellite Imagery covering Bandung Basin Administration Boundary Watershed Boundary Method

13. Landcover density index: Land use types area * Run off coeff icient • Run Off Coefficient derived from CN-NRCS graph Method

14. Stream Flow Separation • Recursive digital filter equation: q1 = αqi-1+ β (1 + α) (Qi –Qi-1) And : qB1 = Q1 – q1 Q1 = TF (Total Flow) series q1 = HF (high flow) series qB1 = BF (base flow) series i = time index (day) α, β, = separator parameters (α = 0.95; β = 0.5) Method

15. Result Curve of Base Flow - High Flow Separation at Nanjung 1980 Method

16. Result Result

17. Monthly Isohyet Maps Pebruari 1986 Mei 1986 Januari 1986 Juli 1986 Nopember 1986 Desember 1986 Result

18. Variability of Average Monthly Rainfall at Bandung Basin (1986 -2010) Result

19. Landuse Changes in Bandung Basin 1976 1994 1999 2001 2008 The Changes of forest area pattern in Bandung Basin occurred in 1976, 1994, 1999, 2001 and 2008 Result

20. Landuse Changes in Bandung Basin 1976 1994 1999 2001 2008 The Changes pattern of plantation area in Bandung Basin occurred in 1976, 1994, 1999, 2001 and 2008 Result

21. Landuse Changes in Bandung Basin 1976 1994 1999 2001 2008 The Changes pattern of upland field in Bandung Basin occurred in 1976, 1994, 1999, 2001 and 2008 Result

22. Landuse Changes in Bandung Basin 1976 1994 1999 2001 2008 The Changes pattern of settlements in Bandung Basin occurred in 1976, 1994, 1999, 2001 and 2008 Result

23. Landuse Changes in Bandung Basin 1976 1994 1999 2001 2008 The Changes pattern of paddy field in Bandung Basin occurred in 1976, 1994, 1999, 2001 and 2008 Result

24. Landuse (Land Cover) at Bandung Basin (1976 – 2008) Result

25. Total Landuse/Landcover Index of Bandung Basin (1976 – 2008) Fast rate Slow rate Sharp rate Result

26. Recapitulation of Streamflow separation result Result

27. Stream Flow Separation Result

28. Streamflow discharge Result

29. The Diagram of Landuse /Landcover Index, High Flow, Base Flow and Average Monthly Rainfall Depth Result

31. Conclusion • Landuse/landcover changes appear since 1994 with maximum decrease of vegetation cover density rate happened in the period of 1998 to 2001. In the period of 2001 to 2008, vegetation cover density continuously decreased at a fast rate. During 1976 – 2008, land use changes in Bandung basin were decreasing forests (16 %), plantations (8%) and paddy fields (13.4%) and increasing upland fields (17 %) and settlements (21%). • Annual rainfall fluctuation is relatively constant, with 6 – 10 yearly variation. Monthly rainfall fluctuation shows strong increase in amplitude, especially after 2004. • Prior to 2003, base flow and high flow curves fluctuated according to the rainfall, however since 2003 the base flow curve shows a decreasing trend while the high flow curve shows an increasing trend. • Constant Base Flow decrease and/or High Flow increase appear after rapidly changes of the vegetational cover at 2003. This indicates that the hydrologic regime is influenced by the landuse change rather than by the rainfall fluctuation. More significant BF decrease and HF increase appear after 2006, likely enhanced by rainfall intensity increase Conclusion

32. Research Question • Does land use changes influence rainfall pattern? • Which one, between land cover and rainfall fluctuation , affects more hydrologic regime? Next Question

33. Thank You