The 4 th GEOSS Asia Pacific Symposium: Hydrometeorological and Related Disaster and Water Resources Management, March 10 12, 2010, Bali Global climate change and recent changes in Indonesia water resources Hidayat PAWITAN Bogor Agricultural University, Bogor 16680, Indonesian Hydrology Society (MHI) hpawitan@ipb.ac.id
Introduction Floods, Droughts, and Forest fires are common natural disasters that occurred frequently in many parts of Indonesia and have caused substantial physical, financial and human losses. It is also well known now that ENSO phenomena as one of the major factors related to these extreme events Many economic sectors are influenced severely by these recurrent disasters, including in agriculture, forestry and the environment Therefore, any possible initiatives and explanation of these cause-effect disasters would be of much value to minimize the negative impacts Strategy, programs and activities are on-going to overcome these, also in relation to Climate Change Adaptation and Mitigation Program
Past and on going study For the purpose of study, extensive monthly rainfall and river discharge data were collected, especially for Java Island simple hydrologic balance relating rainfall to river discharge were employed. Calculate dependable flows defined as 80% exceeding probability were calculated, and future water availability was projected considering climate change scenarios
Locations of hydrometric stations at major river basins on Java
Study results: 1. Dependable flows 2. Long term change of hydrological water balance on Java Island 3. Sign of Climate Change 4. Implication to water resources management
Figure 2. Daily discharge of Ciujung-Kragilan, 1994-2000 Figure 3. Daily discharge of Cisadane Batu beulah, 1996 2000 Water Cycle and Flow Trends of Java Major Rivers Figure 4. Daily discharge of Citarum Nanjung, 1999 2003
Dependable flows for some major rivers in Java island No. River-Station name Basin area [km 2 ] Qmean [m 3 /s] Q80% [m 3 /s] Q90% [m 3 /s] 1 Ciujung-Kragilan 1563 90.3 27.9 13.2 2 Citarum-Nanjung 1675 70.7 24.8 14.2 3 Cimanuk-Monjot 2788 133.3 17.5 5.1 4 Citanduy-Petaruman 1163 117.8 53.2 20.4 5 K.Progo-Bantar 2008 79.0 18.0 5.4 6 B.Solo-Babat 16266 670.1 44.2 22.9 7 Brantas-Mojokerto 11195 246.5 57.3 32.1
Trends of rainfall and river discharges in Java Sungai-stasiun Luas DAS [km 2 ] Tren Curah Hujan [mm/tahun] Tren Debit Sungai [m 3 /s/tahun] Ciujung-Kragilan 1.563 - -0,120 Citarum-Tanjungpura 5.970-4,772-0, 396 Cimanuk-Jatibarang 3.322-7,087-0,290 B.Solo-Babat 16.286-1,908-0,286 K.Brantas - Mojokerto 9.834 +0,214 0,060 K.Progo-Duwet 1.712-8,517-0,168 K. Serayu-Rawalo 3.130-2,459-0,110 Citanduy-Karangsari 2682-6,362-0,310
Projection of monthly discharge of Java rivers, 2030 2050 No Sungai Stasiun Area (m 3 /s) (Km 2 ) 2000 2030 [%] 2050 [%] 1 Ciujung Kragilan 1.563 90.38 86.78 4.0 84.38 6.6 2 Citarum Tanjungpura 5.970 144,00 115.11 8.3 95.85 13.8 3 Cimanuk Jatibarang 3.322 122.33 113.63 7.1 107.83 11.9 4 B.Solo Babat 16.286 414.11 405.53 2.1 399.81 3.5 5 Brantas Mojokerto 9.834 226.77 228.57 0.8 229.77 1.3 6 Progo Duwet 1.712 61.86 56.82 8.1 53.46 13.6 7 Serayu Rawalo 3.130 276.65 273.35 1.2 271.15 2.0 8 Citanduy Karangsari 2.682 136.47 127.17 6.8 120.97 11.4 Catatan: proyeksi 2030 dan 2050 mengasumsikan tren linier.
Trend analysis and long term hydrologic balance for Citarum Upper Catchment 1896-1994 4000 Trend Curah Hujan, Limpasan, dan Sisa Limpasan Tahunan Tinggi/Jeluk (mm) 3500 3000 2500 2000 1500 1000 y 1 = 0,0482x 2-10,53x + 2894,7 y 2 = 0,0142x 2-3,1063x + 1386,4 500 0 y 3 = 0,034x 2-7,4236x + 1508,3 1896 1901 1906 1911 1916 1921 1926 1931 1936 1941 1946 1951 1956 1961 1966 1971 1976 1981 1986 1991 Curah Hujan Limpasan Sisa Limpasan Tahun
Trend analysis and long term hydrologic balance for Bengawan Solo Basin 1916-2001 3000 2500 y = 1.616x + 5220 2000 mm 1500 1000 500 P Q P Q y = 0.476x + 1737 0 1911 1921 1931 1941 1951 1961 1971 1981 1991 2001 2011
Summary of trends of river flow patterns according to basin sections No. River Name Trends of Flow patterns Upstream Middle Downstream 1 Ciujung 2 Cisadane 3 Citanduy Very decreasing Moderately decreasing Moderately increasing decreasing Highly increasing Increasing 4 Citarum Normal - 5 Cimanuk 6 Serayu 7 Bengawan Solo Very decreasing Decreasing Highly increasing Moderately decreasing Moderately decreasing Moderately decreasing Decreasing - Decreasing Decerately decreasing Normal Decreasing Moderately decreasing
Indication of climate changes on Java major river basins No River basin Rainfall trend* River discharge trend* Before 1960 After 1960 Before 1960 After 1960 1 Citarum 2 Cimanuk 3 Bengawan Solo 4 Brantas 5 Progo 6 Serayu 7 Citanduy
LIKELY TRENDS It is believed that at present conditions, the specific discharges of Java s rivers are somewhat lower than those of historical conditions Significant changes had occurred dominated with decreasing trends in the downstream river sections Though decreasing regional rainfall in Java island is very much attributed to ENSO and Indian Ocean Dipole Mode, but the disappearing of Java forest cover in the past century also played significant role.
FACTORS AFFECTING REGIONAL WATER RESOURCES Anthropogenic influences due to population pressures with land hungry Land use changes and forest conversion Sedimentation, water pollution and eutrophication of water bodies Climate variability and likely changes Uncertainties generated to quality of available data
NEED OF ACTIONS: Proposed Activities Proper water resources management at regional level to fulfill the different water uses Monitoring of climate variability and water related disasters based on best available technologies to determine climate variability, regional surface water availability, and water related disasters Encourage collaborative researches and information exchanges among scientists in Asian Pacific region
Concluding Remarks Java rainfall indicates decreasing trend that implies lower river discharges that varies between +0,8 8,3% by 2030 and between +1,3 13,8% by 2050, which is equivalent to rainfall projection due to climate change scenarios. Indonesia certainly has serious problems in water resources management, partly due to serious uncertainties to fulfill the different water uses. Better monitoring and researches initiatives taking advantage geo environmental satellite and remote sensing technology are required. Future collaborative researches and information exchanges among scientists in Asian Pacific region certainly can contribute to better understanding of our nature and can enhance the environmental betterment that support better living conditions.
TERIMA KASIH