I. INTRODUCTION 1.1. Background Droughts are normal recurring climatic phenomena that vary in space, time, and intensity. They may affect people and agriculture at local scales for short periods or cover broad regions or have impacts that are felt for years (Brown, et. al., 2002). Traditional methods of drought monitoring rely on rainfall data, which are limited in the network of stations and incomplete climate data, often inaccurate caused by human error or unworking instrumentation. Most importantly, data in near real time either spatially or temporally is available but not accessible. In this sense, remote sensing technology has greatly enhanced our ability to monitor and manage the natural resources, especially in the areas real time spatial and temporal data are recorded continuously and has been used extensively for water resources management (Runtunuwu, 2005). Remote sensing data can be used in regional monitoring and management in two main ways. The first is to monitor changes in land cover type and condition. This land cover type (forest, crop, grassland, etc) and condition (green or dry) as well as the temporal series of greening of crops can be monitored using a variety of satellite borne instruments (such as Landsat TM, ASTER, SPOT and AVHRR) at a range of spatial and temporal scales. The second use involves converting the remotely sensed data to physical measurements of the earth and using them to derive environmental parameters. This may lead to estimates for parameters of the cover (such as leaf area index or LAI, cover fraction and reflectivity) as well as geophysical parameters such as the surface radiometric temperature and albedo (Jupp, et. al., 1998). The dynamic nature of droughts causes challenges in 1
agricultural planning, predicting of drought occurrence, monitoring, and providing relief to drought-stricken areas. Because of the variability and significant multiple impacts of droughts, we need to improve the available tools to capture their spatial and temporal dimensions (Brown, et. al., 2002). Despite the restricted availability of long time series of adequate remote sensing data, their advantage of high spatial resolution, together with a satisfying sampling rate of relevant surface parameters, should be taken into consideration for drought monitoring. In order to derive spatially resolved information on the water stress of vegetation, different data source have to be combined. In general, remote sensing data provide a high spatial resolution, but few physical parameters, while point data from surface measurements show high accuracy, but not spatially resolved. Thematic data like landuse classification give qualitative information of the surface cover, but remain static in time. In the present study, the moisture status of the land surface is monitored using the daily evolution of the evaporative fraction (EF). Among the various flux ratios using energy balance modeling, EF has received special interest. EF is defined as the part of the available energy used for evapotranspiration. This quantity is an indicator of the moisture status of the land surface, mainly consisting of natural vegetation and agriculture. Water irrigation for agriculture in Karawang is mainly from Jatiluhur, and have problem of water distribution during drought season. The height of water level of Jatiluhur dam on November 15, 2006 is 81.59 meter. Normal condition is usually indicated by water level of 89.81-92.06 meter (Pikiran Rakyat, 2006). Water volume of Jatiluhur dam on January 24, 2007 is below normal level. Consequences, only 50% or 115,000 hectare from 230,000 hectare of irrigated 2
paddy fields in Karawang, Subang, Bekasi and Indramayu area get supply of water. In Karawang target for paddy field area is 101,830 hectare, but only 47,637 hectare is being realized. It occurred due to lack of water supply for irrigation from Jatiluhur dam (Kompas, 2007). The water supply from Jatiluhur dam for irrigation is very limited since the allocation of water supply is divided for industry and domestic use in Jakarta, Bekasi, and Karawang. In environmental analysis, spatial data is one of the important factors that need to be considered. Many researches, decision-makers, planners, and corporate executives use this data to help them in making some critical decisions. One of the common tools is geographic information system (GIS) which runs on PC s or workstations used to store, to analyze, and display multiple layers of geographic information. The unique advantage of GIS is the ability to relate locational map data or spatial data to relevant non-locational data, which is called attribute. Remote sensing information produced by satellite must be interpreted before used in a GIS. In GIS environment, the expansion of computer network, including internet and World Wide Web (www), creates a new opportunity to develop a system for distribution of spatial information. Web-based geographical data services involved management of spatial and non-spatial data introduced to publish information of drought indictor. The development of a web-based system by integrating GIS and DBMS could serve two crucial purposes. Firstly, it could allow user to operate the system without having to grapple with the underlying intricacies of GIS and DBMS technology. Secondly, it could allow sharing of information and technical expertise among a wide range of users. The rapid 3
growth of the Internet and World Wide Web (WWW) provides highly customized, accessible, and interactive sources of information. The purpose of this research is to detect drought indicator using energy balance and evaporative fraction with combine climate and remote sensing data in Karawang district, West Java. Furthermore develop a web-based GIS application to visualize and disseminate research results. 1.2. Objectives The research objectives are: 1. to analyze energy balance and evaporative fraction such as drought indicator in Karawang district; 2. to asses the potential use of remote sensing capability in identifying the surface cover parameter of image and visualization using Remote Sensing and Geographic Information System; 3. to develop a web-based GIS application to visualize and disseminate research results. 1.3. Scope Research site is Karawang district, which is geographically located between 107 o 05 11-107 o 38 32 East and 05 o 55 58-06 o 38 28 South. The research area is dominated by paddy fields and unirrigated land. Karawang district covers an area of 1,737.30 km 2 consisting of 30 sub districts. Administratively, Karawang district is bounded by Java Sea in the northern part, Subang district in the eastern part, Bekasi districts in the western part and Bogor and Purwakarta districts in the southern part. Figure 1 shows Karawang district, West Java Province. 4
Figure 1. The area of study in Karawang district, West Java Province. 5