Global climate change and recent changes in Indonesia water resources

Hidayat PAWITANBogor Agricultural University, Bogor 16680, 

Indonesian Hydrology Society  (MHI)hpawitan@ipb.ac.id

The 4‐th GEOSS Asia Pacific Symposium: Hydrometeorological and Related Disaster and Water Resources Management, March 10‐12, 2010, Bali

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 flows2.  Long term change of hydrological water balance on Java Island3.  Sign of Climate Change4. Implication to water resources management

Figure 2. Daily discharge of Ciujung-Kragilan, 1994-2000

Figure 3.  Daily discharge of Cisadane‐ Batu beulah, 1996‐2000

Figure 4.  Daily discharge of Citarum – Nanjung, 1999‐2003

Water Cycle and Flow

 Trends of Java Major Rivers

Dependable flows for some major rivers in Java island

No. River-Station name Basin area

[km2]Qmean[m3/s]

Q80%[m3/s]

Q90%[m3/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

[km2]

Tren Curah Hujan [mm/tahun]

Tren Debit Sungai [m3/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

(Km2) (m3/s)

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. 

Tren d Curah Hu jan , L imp asan , dan S isa L imp asan Tahunan

y 1 = 0,0482x 2 - 10,53x + 2894,7

y 2 = 0,0142x 2 - 3,1063x + 1386,4

y 3 = 0,034x 2 - 7,4236x + 1508,3

0

500

1000

1500

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2500

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1896

1901

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1911

1916

1921

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T ahun

Ting

gi/J

eluk

(m

m)

C urah Hujan Lim pasan Sisa Lim pasan

Trend analysis and long term hydrologic balance for Citarum Upper Catchment 1896-1994

y = ‐1.616x + 5220

y = ‐0.476x + 1737

0

500

1000

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1911 1921 1931 1941 1951 1961 1971 1981 1991 2001 2011

mm

P Q P‐Q

Trend analysis and long term hydrologic balance for Bengawan Solo Basin 1916-2001

Summary of trends of river flow patterns according to basin sections

No. River NameTrends of Flow patterns

Upstream Middle Downstream

1 Ciujung Very decreasing decreasing Decreasing

2 Cisadane Moderately decreasing

Highly increasing -

3 Citanduy Moderately increasing Increasing Decreasing

4 Citarum Normal - Decerately decreasing

5 Cimanuk Very decreasing

Moderately decreasing Normal

6 Serayu Decreasing Moderately decreasing

Decreasing

7 Bengawan Solo Highly increasing

Moderately 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 lowerriver discharges that varies between +0,8‐8,3% by 2030 and between +1,3 ‐ 13,8% by 2050, which is equivalent torainfall 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 exchangesamong scientists in Asian Pacific region certainly can contribute to better understanding of our nature and can enhance the environmental betterment that support betterliving conditions.

TERIMA KASIH