Java is being most heavily populated but having a small percentage of the Indonesia’s water, the island is predicted to face a clean water crisis. Java has less than 10 percent of the country's water, whereas more than 140 million people live on the island, nearly 60 percent of the country's population. The 2015 estimation by Robert Wahyudi Triweko, an expert on engineering and the management of water resources, disclosed that water demand on Java reached 164.672 million cubic meters per year, while the availability of water was only 30.569 million cubic meters per year, leaving a big deficit gap of 134.103 million cubic meters per year. Meanwhile, Kalimantan has 30 percent of Indonesia's water and only inhabited by six percent of Indonesia's population.
Water demand increase is triggered by urbanization. At the same time, it is also affected by climate change. It is started from sea level rise and increasing rainfall, as well as higher peak flood runoff which affected by urbanization. Those occurences increase flood volume in wider risk area. Finally, it becomes new problem which is increasing flood damage in more houses which builded due to urbanization. Therefore, improvements in water management and related infrastructure are important for solving the problems which threatening future economic success.
Stakeholders need to do assessment as an integrating process to find the interface of physical and social science and public policy. It will be a vulnerability assessments (VAs) which are central to shaping climate change adaptation decisions regarding water sector.
Water resource is a critical sector in vulnerability and adaptation (V&A) discourse. It must consider both managed and natural systems. Both systems are influenced by human activity. For instance in agriculture, external pressure such as flood affects managed system and it has consequence on process control which involves product and good or service.
Integrated water resources management (IWRM) can be a V&A framework. It is a systematic approach which considers both demand and supply processes and actions. It also facilitates adaptive management through continuous monitoring, review and improvement. Stakeholders are closely involved in this approach. There should be proper seasonality of flow regulation for water quantity and quality. It is useful for agriculture, domestic needs, industry, nature and recreation.
IWRM integrates all forms and phases of the water cycle, as well as all water-related sectors. It works on optimal water allocation to different water users through cooperation and coordination among users. IWRM demands integrated project formulation, the empowerment of partner country agencies, policy and institutional development, and stakeholder involvement.
Water use sector is connected with current water demand and supply situation. It is influenced by socioeconomic and climate change development. Each city has different priority water use sector from agriculture, fishery, industry until hydropower. In oder to link supply with demand issues, it is important to know about the hydrologic linkages and the current and future implications of these linkages. A main watershed and main tributary watershed can be shared for hydropower, industry, agriculture and two cities, by using wastewater treatment.
IWRM uses robust decision support method which involves policy makers, planners, investors, implementers, water users, affected stakeholders, researchers and civil societies. There are four stages in method cycle. Starting with participatory scoping dialogue, it will result scenarios and strategies which consist of uncertainties, options, performance metrics and relationship among water use sector. The second stage is system evaluation analysis which produces outcomes for vulnerability assessment in the next stage. The assessment brings leading strategies for creating risk management. It will be a robust strategy and also new insights for future scoping dialogue and make the method sustainable.
There are several tools in water resource V&A studies in some sectoral models. Hydrological model can help to do supply analysis. The critical questions will be how does rainfall on a catchment translate into flow in a river, what pathways does water follow as it moves through a catchment and how does movement along these pathways impact the magnitude, timing, duration, and frequency of river flows. Afterwards, we analize demand through planning model. Water should be allocated to various uses in time of shortage. These operations can be constrained to protect the services provided by the river. Infrastructure in the system (e.g., dams, diversion works) should be operated to achieve maximum benefit. As a result, allocation, operations, and operating constraints will change when new management strategies are introduced into the system.
Another analysis is needed is risk analysis. Hydraulic Model can identify how fast, deep is river flowing (flooding effects), risk factor and exposure to flooding that might affect the economical, social/infrastructural and environmental activities of a community. It is also able to find out changes to flow and channel morphology impact sediment transport and services provided (fish habitats, recreation, etc).
Result of the analysis will help stakeholders to choose effective adaptation actions. Construction/modification of physical infrastructure like integrating separate reservoirs into a single system can support water supply. Another option is adaptive management of existing water supply systems such using conjunctive surface/groundwater supply. Adaptation can also be done regarding water demand. It should be through policy, conservation, efficiency, and technology, for instance; rainwater collection for domestic non-potable uses, high value/low water use crops for agriculture, water re-use and recycling for industry and reservoir re-operation for energy (hydropower).