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
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Introduction
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 km3 water on 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 stressed due 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.
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Need 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 very useful as it can provide a cost-effective means
of replacing or complimenting field data collection. The fact that EO can provide coverage over
large 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-todate predictive and analytical products.
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Space-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.
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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.
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Some 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.
4.1
Mapping 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
Recherche Informatique 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 an EOADP (Earth Observation Application Development
Program) contract from CSA (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
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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.
4.2
Water 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
and the know-how for better support in the management and arbitration of precarious water
resources. The conceptual model of the database has been designed to consider the water agency’s
entire role and mission. The application developed proposed a solution to four problems 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 Remote Sensing, the development
of the IDSS was successfully completed by providing to the water agency a spatial geo-database with
an updated and high resolution DEM, land cover map and modeling tools. These tools developed by
the implementation and integration of applications meet specific requirements of the agency. These
applications have been designed with the four global or local objectives stated above. Beyond the
technical and methodological components, the realization of IDSS highlighted the importance, in a
project of this kind, of a strong partnership with local stakeholders and staff training.
4.3
Space-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.
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Conclusions
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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