Télédétection et ressources en eau/Remote sensing and water resources
17
One paper (Aouni) described the analog interpretation of LANDSAT images followed by
the analysis of SPOT images as a tool for the inventory of surface water in Tunisia: waters
surfaces, dams, hydrologic network, boundaries of watersheds, wetlands, agricultural resources.
In humid tropics, to compensate for the continuous presence of cloud cover, the use of radar
images appears to be more appropriate, notwithstanding the rather poor information included in a
single image. This solution can be integrated with temporal methods.
The importance of satellite images can be measured by comparing the contribution of the
images and of all other material available. In the case of tropical zones for which low-quality
maps exist, satellite data, even of low resolution, quickly attain a much higher level of interest
than other existing data. For areas that have unclear or variable boundaries (such as tropical
wetlands), it is difficult to carry out proper classifications and field checks become essential
(Lointier).
The utilization of GIS for the description of regional information in order to obtain
improved knowledge and better management (including conflicts in the case of limited resources)
was also the subject of several presentations (Bousquet et al., Faurès, Killmayer). The following
were presented:
• the use of data obtained from remote sensing or of data from the intersection of multiple
overlays within a GIS;
• the relation between hydrological and territorial units (administrative or political boundaries of
the land), and the hydraulic exchanges between territorial units
• the integration in a GIS of data from different sources, including remote sensing data. A
practical example is given for Senegal (Killmayer). This describes the updating of maps of
rice paddies with the objective of large scale monitoring of cropping and management. The
approach is simple, operational and proposes a methodology that is now widely used in remote
sensing: classification and integration into a GIS for the annual monitoring of crops. What is
shown, can be considered to be a first step in the management of water resources, through the
elaboration on an annual basis of a monitoring and information tool for rice crops. In the
specific case, the cost of remote sensing represents only 10% of the global cost of the
monitoring system, which makes it easy to integrate it into the project.
Local approach
Several local level application were included in the presentations:
The detection of water surfaces
The detection of water surfaces on an optical satellite image (SPOT, Landsat, etc.) is one of the
easiest applications of remote sensing: the very weak radiometry of open water surfaces,
particularly in the near infrared, gives them a high level of separability if compared to the other
themes of the image. One presentation (Ousmane) gives an example of this type of detection in
areas with poor cartographic information. There are two main ideas:
-
remote sensing can be a powerful tool, on condition that it is used in conjunction with other
local topographic and hydrological data: in the example provided, the combination of remote
sensing information (SPOT), climatic data (ground station) and a good knowledge of the
17
One paper (Aouni) described the analog interpretation of LANDSAT images followed by
the analysis of SPOT images as a tool for the inventory of surface water in Tunisia: waters
surfaces, dams, hydrologic network, boundaries of watersheds, wetlands, agricultural resources.
In humid tropics, to compensate for the continuous presence of cloud cover, the use of radar
images appears to be more appropriate, notwithstanding the rather poor information included in a
single image. This solution can be integrated with temporal methods.
The importance of satellite images can be measured by comparing the contribution of the
images and of all other material available. In the case of tropical zones for which low-quality
maps exist, satellite data, even of low resolution, quickly attain a much higher level of interest
than other existing data. For areas that have unclear or variable boundaries (such as tropical
wetlands), it is difficult to carry out proper classifications and field checks become essential
(Lointier).
The utilization of GIS for the description of regional information in order to obtain
improved knowledge and better management (including conflicts in the case of limited resources)
was also the subject of several presentations (Bousquet et al., Faurès, Killmayer). The following
were presented:
• the use of data obtained from remote sensing or of data from the intersection of multiple
overlays within a GIS;
• the relation between hydrological and territorial units (administrative or political boundaries of
the land), and the hydraulic exchanges between territorial units
• the integration in a GIS of data from different sources, including remote sensing data. A
practical example is given for Senegal (Killmayer). This describes the updating of maps of
rice paddies with the objective of large scale monitoring of cropping and management. The
approach is simple, operational and proposes a methodology that is now widely used in remote
sensing: classification and integration into a GIS for the annual monitoring of crops. What is
shown, can be considered to be a first step in the management of water resources, through the
elaboration on an annual basis of a monitoring and information tool for rice crops. In the
specific case, the cost of remote sensing represents only 10% of the global cost of the
monitoring system, which makes it easy to integrate it into the project.
Local approach
Several local level application were included in the presentations:
The detection of water surfaces
The detection of water surfaces on an optical satellite image (SPOT, Landsat, etc.) is one of the
easiest applications of remote sensing: the very weak radiometry of open water surfaces,
particularly in the near infrared, gives them a high level of separability if compared to the other
themes of the image. One presentation (Ousmane) gives an example of this type of detection in
areas with poor cartographic information. There are two main ideas:
-
remote sensing can be a powerful tool, on condition that it is used in conjunction with other
local topographic and hydrological data: in the example provided, the combination of remote
sensing information (SPOT), climatic data (ground station) and a good knowledge of the