Water Resources Studies by
Remote Sensing Techniques in Bangladesh Dr. M.A H. Pramanik Babgladesh Space Research and Remote Sensing Organization (SPARRSO) Agargaon, Sher- e Bangla Nagar Dhaka, Bangladesh Abstract Remote sensing by satellites and airborne surveys provides and authentic sources of information for surveying, identifying, Classifying , mapping and monitoring of natural resources in general and water resources in particular. Mutiband and multidate satellite imagery and aerial photographs ( both black and white and colors infrared ) have been extensively used in Bangladesh for water resources studies and management including flood studies Since 1968 the meteorological satellite ground station has been operational in Bangladesh and has been periodically upgraded. The meteorological Satellite imagery / data of 1 km resolution is in operation but the high resolution resources satellite imagery/ data (30 m and 10 m ) reception is yet to be made operational. Satellite information/ data have limitation of resolution and cloud penetration capability. In the present paper attempts have beenmade to highlight to highlight various activities done in Bangladeshin the water resources sectors using remote sensing techniques. The study includes water bodies survey, river course monitoring, drainage pattern mapping, flood studies, monitoring of Kaptai lake and coastal morphology etc. Efforts are being made to up-date the technology including procurement of software, development of models for quantization of rainfall estimate, studies of snow melting from satellite imagery, indroduction of a Geographic Information System (GIS) , arrangements of making high resolution satellite data ( Landsat/SPOT ground station) operational and procurement of survey aircraft with necessary accessories. A combination of satellite and airborne remote sensing information/data will help in water resources management including flood studies, river course monitoring, mapping, resource management and disaster warning as well as assessment in the country. 1. Introduction Water is life. But in Bangladesh it is both life and death The country has a large network of rivers, dominated by the Ganges-Brahmaputra-Meghna (GBM), channels and depressions such as beels, haors, boars and ponds. The GBM originates in the number of rivers, channels and stream in Bangladesh is about 230 with a total length of about 24,000 km which occupy a riverine area of about 9000 sq km. The country comprises the eastern portion of the Ganges delta which is characterized by flat terrain interlaced with an intricate system of rivers and tidal channels which carry downstreem an enormus amount of sediment laden water to the Bay of Bengal which is to the south of the country. The Bay acts as both the source and sink of water. During the southwest monsoon period, the country has excess water leading to catastrophic ravages like flood. The floods of 1984, 1987 and 1988 are the living examples. On the other hand, during the winter the country faces the acute shortage of water leading to drought like situations. Such opposing situations call for proper management of water resources of the country minimizing the effects of both the extremes (flood and drought) and maximizing the uses of the water resources in the country and regular Monitoring of water conditions both inside and outside the country. Towards this, the application of remote sensing has great potential. SPARRSO operates an Advanced Meteorological satellites (NOAA, GSM) and from a few Data Collection Platforms (DCPs) located in different parts of the country. The installation of SPOT/Landsat Ground Station with the complete facility for real time reception, archiving, preprocessing and analysing of data from U.S. Landsat and French SPOT resource satellites is yet to be complete. Digital image analysis systems and visual photo interpretation equipment are available to support the application-oriented resource management and environmental studies, SPARRSO has highly trained resource scientists, computer engineers and other technical personnel. The research activities of SPARRSO are carried out in different fields for solving the practical resource inventory and environmental problems confronting Bangladesh. SPARRSO provides its research: results and remote sensing data/information to the user agencies in the country. The future programmes of SPARRSO include the strengthening of its technical facilities, creating a resource data bank including Geographic Information System at national level, training of manower and development of aerial photographic capability. SPARRSO also envisages to cooperate with the countries in the region and supports international collaboration in space research and remote sensing activities. Regarding water resource studies, continued use of satellite imagery and aerial photographs is being made for studying surface water distribution, river course monitoring, seasonal variations of water levels, dry season conditions of water pools, upstream conditions of water including those outside the country, discharge conditions in the estuaries, turbnidity levels in waters, water temperature both within the rivers and in the Bay of Bangal. The future studies are likely to include snow melting in the Himalayas, quantitative assessment of perceptible water in clouds, flood area mapping development of GIS-etc. The remote sensing technique has been found quite useful in water resources studies. 2- A few case studies on Water Resources SPARRSO has conducted a number of studies relating to water resources. Some of them are project works for other user agencies and some are SPARRSO’s own regular R & D and operational activities. A few examples of these studies are given below: 2.1 Water Bodies Survey Under a contract with the Fisheries Department of Bangladesh, SPARRSO conducted a study on the total available water bodies in the country, both small (less than 25 ha) and large (greater than 25 ha). For the study both satellite imagery and aerial photographs were used. The study, among other things, showed that (Based on statistical sampling basis) the total no of ponds in Bangladesh is 1.30 million covering an area of 1,44,000 ha. For large water bodies maps have been prepared at 1:50,000 scale. This study was later on used by SPARRSO to prepare catchmentwise water resource map of the country for the Master Plan Organization (MPO). 2.2 River Course Monitoring Rivers in Bangladesh are constantly changing their courses. It is important to monitor these changes for flood protection and management. Remote sensing techniques provide an important tool for such monitoring and identification. Several studies have been conducted in SPARRSO on river course changes by using multidate and multiband satellite imagery and this is one of the regular activities in SPARRSO. The findings have been used by several organizations/agencies. 2-3 Drainage Pattern Map of Bangladesh A drainage pattern map of Bangladesh has been prepared using Landsat imagery. This map provides information for all the major channels in the country. The map can be updated from time to time. This type of map provides an important piece of information for flood protection and management. 2.4 Kaptai Lake Study A study on surface water conditions of the Kaptai lake was done under an IDRC project. The area of the lake at three different seasons was estimated using remotely sensed data. 2.5 Coastal Morphology Regular studies are done on the coastal morphology of Bangladesh. The main focus is on the mapping of accreted and eroded loand. The change-detection maps are updated almost every year. Among the several usefulness, this type of studies provides information on the rate/course of disposal of flood water into the Bay of Bangal. It can also help plan dredging of river courses at appropriate places and help in straightening the river courses. 2.6 River Flood Hydrology Using the NOAA meterological satellite data, investigations on flood and the associated hydrological conditions in Bangladesh and the surrounding areas are don on a regular basis. Such studies provide information of turbidity levels of rivers, estimation of surface water temperature, etc. The NOAA AVHRR imagery are regularly used to monitoring the over all flood situation in and around the country. 2.7 Flood Control and Drainage Pattern Mapping SPARRSO is technically involved with execution of the Flood Control and Drainage Pattern Mapping project of Bangladesh water development Board (BWDB). ASPARRSO coordinated the acquisition of aerial photography data and is providing technical supervision and quality checking of land resources maps that are being prepared for the project for three selected location. 3. Future Potential The remote sensing technology has a promising future in Bangladesh. The types of studies that have been mentioned earlier can be continued/updated on a regular basis and improvements can be made on the results/findings (i) by carried out further research and (ii) with the continued improvements in technique itself, such as sensor resolution and cloud penetrability. Further areas of investigation will include:
The remote sensing technique provides a powerful tool for studying water resources in the country. The combination of satellite imagery, aerial photographs and conventional as well as ground truth information/data constitutes one of the best ways to study and monitor water resources in Bangladesh. This will allow better planning and management of water resources in the country. The proper use of water resources and mitigation of the effects of floods will promise a better life for the people. |