APPLICATION OF SPACE-BASED REMOTE SENSING TO WATER MANAGEMENT
Paper Presented by:Dr. Harinder P. S. Ahluwalia, Eng.
President, Info-Electronics Systems Inc. Montreal Canada
1Introduction
Other than Air, Water is the second most important element for sustaining life on the planet. Despite being apparently in abundance, fresh water is available in a very limited quantity. According to the UNEP Report, out of a total volume of about 1.4 billion km3wateron Earth, the volume of freshwater resources is around 35 million km3, or about 2.5 percent of the total volume. Of these freshwater resources, about 24 million km3 or 70 percent is in the form of ice and permanent snow cover in mountainous regions, the Antarctic and Arctic regions. Around 27 percent of the world’s freshwater is stored underground in the form of groundwater (shallow and deep groundwater basins up to 2,000 metres, soil moisture, swamp water and permafrost). This constitutes about 97 percent of all the freshwater that is potentially available for human use. Freshwater lakes and rivers contain an estimated 105,000 km3 or around 0.3 percent of the world's freshwater. The Earth's atmosphere contains approximately 13,000 km3 of water.
The total usable freshwater supply for ecosystems and humans is about 200,000 km3 of water - less than 1 percent of all freshwater resources.
The world’s fresh water supply is critically stresseddue to growing population especially in environmentally sensitive areas along the coasts. The supply of water is spread around the world inconsistently. A very large percentage of population faces critical shortages of water supply and by 2030 approximately 47% of the population will be in that position. Therefore, the effective management of water resources is of paramount importance.
2Need for Water Management
Water management is a very complex issue and it requires large amounts of diverse accurate data in a timely manner. Collection of data by traditional means (e.g. field work) can be quite difficult at times, especially in remote areas, as well as costly and resource intensive. Many organizations have supplemented their ground-based monitoring with the use of Earth Observation (EO) technologies such as satellite based monitoring which can be veryuseful as it can provide a cost-effective means of replacing or complimenting field datacollection. The fact that EO can provide coverage overlarge and remote areas with systematic, repetitive data captures makes it doubly attractive. EO data can also be integrated with the in-situ collected data (i.e. real-time)to produce effective up-to-date predictive and analytical products.
3Space-based Technologies for Water Management
Whereas,US Landsat satellites and French SPOT satellites have been commonly used for water related applications, the introduction of Synthetic Aperture Radar (SAR) based satellites – especially the ones in the last decade with high resolution and dual polarization – have revolutionized the work in water mapping and management, marine surveillance, ice monitoring, disaster management, environmental monitoring, resource management, etc. Accurate Digital Elevation Models (DEM) are being developed to assist in determining water flows and flooding potential. Land cover and land usage mapping, wetland mapping, snow extent mapping, water quality monitoring, etc. are the other areas where remote sensing is a great tool.
One of the interesting experiments being conducted by NASA in water management is known as GRACE (Gravity Recovery and Climate Experiment). GRACE refers to a pair of NASA satellites that have flown in low-Earth orbit since 2002. The data collected by these satellites is used to determine surface mass, total water storage, and derived variables. The surface mass signal largely reflects total water storage (TWS); over the ocean TWS is interpreted as ocean bottom pressure and on land it is the sum of groundwater, soil moisture, surface water, snow and ice.
4Some Examples of Space-based Techniques
Our company, Info-Electronics Systems Inc. (IES),has also made some interesting contributions in the field of water management using in-situ data and remote sensing techniques. We summarize some of the applications below.
4.1Mapping of Water Bodies
The National Topographic Database of NRCan(Natural Resources Canada) covers more than 10 million square kilometres. The hydrographic information of the database contains more than 60% of the entities to be updated. The current manual update of this database by visually comparing the vectors of the CanVec Database to SPOT orthoimages is too cumbersome. In 2009, CRIM(Centre de RechercheInformatique de Montréal) issued recommendations to CTI-S(Centre for Topographic Information – Sherbrooke) and developed a prototype for the automatic updating of water bodies from SPOT-5 imagery (CRIM, 2009). In the second phase, this prototype was improved in order to be integrated in the production process within the CTI-S.
Our project which was executed under anEOADP (Earth Observation Application Development Program) contract fromCSA (Canadian Space Agency), implements innovative solutions to exploit the capabilities of RADARSAT-2 data for the mapping of water bodies. IES, in collaboration with the CRIM, has developed a system to improve and update the existing mapping of inland water bodies as well as find new objects using RADARSAT-2 data in the context of updating the hydrological information within the CanVec database of NRCan. The developed system contains advanced image processing algorithms specifically tuned for optimal performance for an application in water mapping. Due to its high resolution and polarimetric data, the use of SAR imagery provides a more complete and accurate description of the scene compare to the use of SPOT imagery. The system is being tested on data provided by the CTI-S.
The use of open source libraries for a large segment of this project provides our team with an extensive set of algorithms some of which are currently not available in commercial software. Also, the project covers a quantitative as well as qualitative assessment of the capabilities of RADARSAT-2 data, applied to water body extraction and mapping. This will result in recommendations for optimal image acquisition for the generation of information products that will fulfil the user information needs in the context of cartography.
To the best of our knowledge, there was a need for a high level information extraction tool in remote sensing due to the increasing number of commercial sensors and the tremendous amount of data they can provide. Furthermore, the use of automatic or semi-automatic tools is an aspect which is crucial for the development of an operational solution to meet the information needs of our end-user partner -NRCan.
The RS2-CHIM system is composed of the following subsystems: (1) An image processing subsystem responsible for producing raw updated shapes for each valid water body. (2) A post-processing subsystem responsible for quality control, simplifications and report generation. (3) A web interface that enables the user to view and consult the results.
Our next step will be to find some means of doing bottom profiles of water bodies using Remote Sensing. This will allow us to determine the amount of surface water available in a given area.
4.2Water Resource Management and Prospecting in Morocco
Another project we executed under the EOADP Program of CSA is the implementation of an IDSS (Integrated Decision Support System)designed specifically for the AHBSM (Souss-Massa Hydraulic Basin Agency). This system provides AHBSM with an updated spatial database, the appropriate tools andthe know-how for better support in the management and arbitration of precarious waterresources. The conceptual model of the database has been designed to consider the water agency’sentirerole and mission. The application developed proposed a solution to fourproblems identified with the heads of the Agency: ground water availability, reservoir management, soil erosion and flood risk mapping.
Using EO products, with the help of the Morocco Royal Center for RemoteSensing, the development of the IDSS was successfully completed by providing to the wateragency a spatial geo-database with an updated and high resolution DEM, land cover map andmodeling tools. These tools developed by the implementation and integration of applicationsmeet specific requirements of the agency. These applications have been designed with the four global orlocal objectives stated above. Beyond the technical and methodological components, the realization of IDSShighlighted the importance, in a project of this kind, of a strong partnership with localstakeholders and staff training.
4.3Space-based Remote Sensing in Disaster Management
We have also developed a model for an IDFMS (Integrated Disaster Forecasting and Management System). In this model, space-based remote sensing is used for rainfall forecasting, determining DEM, and flood water cover and after-disaster assessment.
5Conclusions
As has been illustrated above, because of its various advantages related to area coverage, timeliness, measurement frequency, etc,.space-based technologies can be applied fruitfully to the important field of Water Management. As new satellites with more precise polarimetric sensors become available along with new application software, much improvement can be expected in this field.
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