2). The greenhouse effect has led to a significant year-on-year increase in the Earth's global air temperature. This phenomenon is known as global warming.

Global warming caused by greenhouse gases clearly has and will continue to affect the world's climate. WWF Indonesia and IPCC (1999) have reported that the annual temperature in Indonesia has increased by 0.30C since 1990. A climate change scenario (WWF Indonesia and IPCC, 1999) estimates that the temperature will increase between 1.30C to 4.60C by 2100 with a trend of 0.10C-0.40C per year. Furthermore, Susandi (2006) projected that Indonesia's temperature increase will reach 3.50C in 2100, while the earth's global temperature will reach a maximum of 6.20C in that year. The implication of the temperature increase will raise the sea level by 100 cm by 2100. The accumulation of these events will affect current and future infrastructure, buildings, and human activities.

One of the human needs issues affected as a result of global warming is water availability. Water availability is an important issue related to climate change. Vörösmarty et al. (2000) showed that water problems occur due to an increase in the earth's population, which increases the demand for water. Increased demand will put more pressure on the global water system, which is related to the effects of global warming. Increased population and economy are the main drivers of water demand, while its availability is affected by increased evaporation due to an increase in the earth's surface temperature. This correlates to the need for integrated management of water resources, which if not done will result in the destruction of water resources physically, institutionally, and subsequently with socioeconomic implications.

The current state of water management in Indonesia is categorized as poor. If left unchecked this will cause unfortunate problems, hence the need for systematic and planned prevention. A half-hearted approach to solving the problem will not result in a comprehensive and environmentally sustainable solution. Decision-makers and authorities need a study that can bridge the scientific backgrounds between them so that they can formulate a decision that is balanced and harmonious between the social, environmental and economic functions of water resources.

This study was made to analyze the impact of climate change on water availability in watersheds. This study provides answers to the needs of climate change analysis related to temperature, precipitation and will further affect the variables associated with the water balance system and water management in an integrated manner. The study area in this research is the Citarum Watershed, West Java. The results of this study are expected to provide an overview of water body management as a result of climate change, which can then be used to recommend sustainable development plans.