Rainfall patterns have become less predictable, especially in densely populated Java. This has reduced water reliability for both irrigation and urban supply.
Changes in Water Supply Over the Last 30 Years
Over the past three decades, Indonesia has experienced increasing climate variability, linked to El Niño–Southern Oscillation (ENSO) events. El Niño years bring droughts and reduced rainfall, while La Niña events often trigger floods and infrastructure disruption. These climate extremes are widely documented as key drivers of hydrological variability in Indonesia’s water systems. Research suggests that the frequency and intensity of ENSO events are likely to increase as climate change accelerates, further portraying a water-insecure future for Indonesia.
Rainfall patterns have become less predictable, especially in densely populated Java. This has reduced water reliability for both irrigation and urban supply. Groundwater extraction has increased significantly, especially in urban centres such as Jakarta, contributing to land subsidence and saltwater intrusion in coastal aquifers.
Deforestation and watershed degradation have also reduced natural water retention capacity, increasing runoff during rainy seasons and reducing dry-season availability.
Water Supply Needs: Agriculture and Domestic Use
Indonesia’s water demand is dominated by agriculture, which accounts for approximately 80% of total freshwater use, particularly for rice cultivation.
Agricultural production is highly dependent on monsoon rainfall and irrigation infrastructure, which remains uneven in efficiency and coverage. Many irrigation systems are aging or degraded, leading to water losses and inefficiencies.
Domestic water demand is rising rapidly due to urbanisation and population growth. Large cities such as Jakarta, Surabaya, and Bandung face increasing stress on piped water systems. In many areas, households still rely heavily on groundwater due to insufficient coverage of the piped water supply.
Sources of Water Supply
Indonesia’s water supply is derived from multiple sources:
- Surface water (rivers, lakes, reservoirs): primary source for agriculture and urban supply
- Groundwater: widely used for domestic and industrial purposes, especially in cities
- Rainwater harvesting: locally used but not widely scaled
- Small island systems: dependent on rainfall and freshwater lenses
Indonesia has high overall renewable water availability, but distribution is highly uneven across regions. For example, Java, which supports over 57% of the population but has only about 4–5% of the country’s surface water resources, faces chronic local scarcity.
Pressures on Water Supply
Several interconnected pressures affect Indonesia’s water systems:
- Climate change: Increasing droughts, floods, and sea-level rise are affecting both quantity and quality of water
- Urbanization: Rapid growth increases demand and stresses infrastructure
- Land-use change: Deforestation reduces watershed stability
- Pollution: Over half of Indonesia’s rivers are heavily polluted due to untreated wastewater and agricultural runoff (OECD)
- Groundwater over-extraction: leading to subsidence and saltwater intrusion, especially in coastal cities
Indonesia is also among the most disaster-prone countries globally, with floods, droughts, and landslides increasingly affecting the reliability of water infrastructure.
Government Actions and Adaptation Measures
Indonesia has introduced several responses to strengthen water security:
- Expansion of dams and reservoirs for irrigation and flood control
- Watershed rehabilitation and reforestation programs
- Community-based rural water supply programs (PAMSIMAS)
- Regulation of groundwater extraction in major cities
- Integrated Water Resources Management (IWRM) approaches
The government is also increasingly focusing on integrated urban water management to address fragmented governance in cities and improve coordination across sectors (World Bank Urban Water Management Framework)
To What Extent Can Climate Action Improve Water Supply?
Addressing climate change is critical for stabilising Indonesia’s water systems. Reduced global emissions would help moderate rainfall extremes, reducing both drought frequency and flood intensity. At the national level, adaptation measures such as forest restoration, improved irrigation efficiency, and groundwater regulation can significantly improve water availability and quality.
Strengthening climate resilience also reduces pressure on groundwater systems, protects coastal aquifers from salinisation, and enhances agricultural productivity. However, because Indonesia’s water challenges are also driven by governance, land-use change, and infrastructure gaps, climate action alone is necessary but not sufficient. Integrated water governance and infrastructure investment must accompany climate strategies.
Learn More Resources
OECD (Water Financing and Disaster Risk Reduction in Indonesia)
https://www.oecd.org/en/publications/water-financing-and-disaster-risk-reduction-in-indonesia_3205b20a-en.html
This post is submitted by Climate Scorecard Indonesia Country Manager, Netra Naik.