Spatial ecological evaluation of water conservation in Jabotabek Area, Indonesia using GIS

According to the United Nations, only 30% of the world`s population lived in cities in 1950. This proportion increased to nearly 50% in 2000, and is projected to reach 60% in 2025. The escalation of urbanization is dramatic in the developing world, where the number of urban dwellers has increased more than fourfold since 1950. This phenomenon is also evident in countries of Southeast Asia, which are the most populous among tropical countries. By the end of the 20th century, the urban population in Indonesia was increasing rapidly particularly in the largest urban agglomeration, the Jakarta Metropolitan Region, also known as Jabotabek (Jakarta, Bogor,Tanggerang, Bekasi). In 1990, more than 75% of the Jabotabek population resided in urban areas. The population growth here, in the center of economic growth and national development since the beginning og the 20th century, has led to the expansion of urbanization in Jakarta and adjacent areas. This unprecedented escalation in the place of urban development has significantly affected humanity`s relationship with urban green space and nature. It is obvious from some studies that for a long time cities have been perceived as unnatural places with no rewarding ecological features. Human activity has a marked impact on the development of the urban landscape. Rapid urbanization and industrialization in Jabotabek has caused serious environmental problems, including land use conversion, decreasing water quality, increasing urban temperature, water and air pollution, intrusion of sea water, flooding, and much more. These problems have become serious as the urban green space (trees, shrubs, and groundcovers), which directly benefit the urban environment, has decreased rapidly with the urbanization process. Besides the rapid land use change problems, the condition of water resources in Jabotabek has become an important environmental issue that needs to be addressed. Study by Dharmapatni and Firman (1995) showed that ground water and surface water in Jabotabek area are in critically short supply. Groundwater has been withdrawn at an alarming rate and seawater intrusion has taken place as far as 12 km inland of Jakarta. As a consequence, there is now problem of supply adequate water. The ecological evaluation of water conservation function within Jabotabek has become an urgent task, especially to identify the spatial distribution of areas, which should be preserved for water conservation. Based on this perspective in mind, we conducted an integrated analysis of ecological functions in Jabotabek area by using GIS, to evaluate the role of urban green space in the ecological functions of water conservation. We carried out this study in three stages. First, we evaluated water conservation function. This is evaluated by the superiority of condition of land surface and water retention on land (Hamazaki-Gesite, 1993). In water conservation model, we slightly modified the original model and used the environmental information on annual precipitation, land use, slope, soil type and geology as parameters. Second, by using landsat image data, we predicted the urbanization and development of built-up areas trends with time series data. Third, we analyzed the water condition in the future based on simulations in the year of 2025, as a base of land use parameter in the modeling for water conservation. The research result showed spatial distribution of water condition within Jabotabek area. By using landsat data we created the model of urbanization of Jabotabek. The model is Y=0.5411 x + 1050.5, while Y is ratio of built up areas and x is years. We used this model for predicting urbanization condition in the year of 2005 and 2025, and used it for simulation of evaluation the water condition of Jabotabek in yhe year of 2005 and 2025. The result showed that urbanization caused decreasing of water condition within Jabotabek areas, especially in the north part areas.