Florinsky, Igor 
Turkey appeared from the satellite images to be 60% larger than from the secondary data collected 
from governmental statistics. Another example of dubious secondary data is from Pakistan, where 
different soil salinity surveys resulted in more than 500 % between the lowest and the highest estimate 
of soil salinity occurrence in Pakistan. It is obvious that if such type of secondary data is used in 
establishing intra-basin water cooperations, disputes and conflicts can potentially worsen and trust 
will fade away. 
The spatial resolutions of satellites can be divided roughly into 3 categories. Low resolution satellites 
have a spatial resolution of typical 1 km, and this category is most promising for surveying large 
basins. More candidate sensors will be launched in the future, and a summary is presented in Table 1. 
High resolution satellites have a spatial resolution in the range between 20 to 30 m. They give a high 
degree of spatial detail, but their return period is with 15 to 25 days not suitable for concurrent 
monitoring. Cloud formation can wipe out acquisitions easily, so that data is not acquired for 
elongated periods. More recently, there is a third category of earth observing satellites that is 
operational with a spatial resolution of 1 to 5 m. These fleet of satellites is particular useful for 
sensing cartographical features and civil works. 
  
  
  
  
  
  
  
  
  
  
Satellite | Radiometer | Spatial resolution | Temporal resolution | Total bands Spectral region 
NOAA AVHRR 1.1 km 0.5 days S VIS, NIR, TIR 
Envisat AATSR 1.0 km 1 day 18 VIR, NIR, TIR 
Envisat MERIS 1.0 km 3 days 15 VIS, NIR 
TERRA | MODIS 250 m to 1.0 km 1 to 2 days 36 VIS, NIR, TIR 
  
  
  
  
Table 1: Operational low resolution satellites and radiometers suitable for monitoring hydrological 
processes in vast international river basins 
The public character of satellite data entitles different user categories to use this data. With raw 
satellite data on the Internet, states are no longer be able to conceal field conditions to their fellow 
basin states. Several space agencies are now opening international and freely accessible databases 
with raw or first order processes satellite images. Data from an international fleet of sensors can be 
found in the Earth Observing System Data and Information System (EOSDIS). Eight Data Active 
Archive Centres (DAAC's) representing a wide range of Earth science disciplines are operational 
under NASA to process, archive and distribute EOSDIS data. The Earth Resources Observation 
System (EROS) Data Center of the USGS provides in addition access to land processes data from 
both satellite and aircraft platforms. A WWW interface enables you to search for, browse and order 
earth science data. It is a new policy to keep prices of images low, so that satellite information 
becomes everybody’s business. Some examples of internationally opened satellite databases can be 
found at http://www.saa.noaa.gov, http://daac.gsfc.nasa.gov or http://modis@nsidcdaac, to mention a 
few. There are no restrictions on the use, reprocessing or redistribution of the satellite data made 
available through the USGS and NASA. Some satellite data are entirely free, for others preprocessing 
costs have to be covered from purchases. 
This opens complete new opportunities to study the hydrological process, water resources depletion, 
food security and environmental development in international river basins. It opens a new protocol 
where central governmental bodies and internationally controlling agencies get united information. 
Remotely sensed information has a public domain status, and everybody listed in Fig. 2 can have 
access to raw satellite information. Federal Governments and the UN can inspect land and water 
resources management issues, either by hiring their own experts or by involving commercial 
consultants. 
  
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 443