International Archives of Photogrammetry and Remote Sensing. Vol XXXII Part 7C2, UNISPACE III, Vienna 1999 
39 
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I5PR5 
UNISPACE III - ISPRS Workshop on 
“Resource Mapping from Space” 
9:00 am -12:00 pm, 22 July 1999, VIC Room B 
Vienna, Austria 
I5PR5 
productivity of the diverted water that is physically consumed 
be either, that intended process (e.g. evaporation of crops) or 
other processes (e.g. evaporation of wetlands), see Perry (1999) 
for more details. The data requirement for these water 
accounting procedures comprises the type of agro-ecosystem, 
the type of crop, the water requirements of each ecosystem to 
obtain maximum biomass production, the water requirements to 
get the maximum return of water resources, water consumption 
through actual evaporation, irrigated area, crop yield etc. Water 
use and land use needs to be linked in order to determine the 
productivity of water used in catchments and river basins (e.g. 
Bandara, 1998). 
The objective of this paper is to make water mid environmental 
policy makers alert of the global water scarcity and the current 
data crisis in land and water resources management. It also aims 
at making space agencies aware that their sensors should be 
dedicated to monitor water management practices in river basins 
applying low resolution and frequently acquired images. 
sources of water (Seckler et al., 1999); runoff being the 
difference between annual precipitation minus actual 
evaporation, net inflow from rivers and aquifers, desalinization 
and changes of water stored in snow, ice, reservoirs, lakes, 
aquifers and soil moisture. Remote sensing can help in mapping 
out precipitation (e.g. Petty and Krajewski, 1996), evaporation 
(e.g. Choudhuiy and DiGirolamo. 1998), irrigated area (e.g. 
Williamson, 1989), crop type (e.g. Jewell, 1989), reservoirs 
(e.g. Thimvengadachari et al., 1980) and snow and glacier 
covered area (e.g. Kite and Kouwen. 1992). Bio-physical 
properties such as vegetation cover, leaf area index, albedo, 
temperature of soil and canopy, absorbed photosynthetical 
active radiation, surface resistance to evaporation and soil 
moisture conditions can also be determined from remote sensing 
data to help describe how vegetation interacts with water and 
soil (Bastiaanssen, 1998). With this earth observation 
information on water resources and vegetative properties. 
PUWR can be assessed with a higher level of confidence. 
2. INFORMATION NEEDS 
The insufficient understanding of the spatio-temporal variations 
of the processes in the soil-water-vegetation-atmosphere 
continuum limits the possibilities to evaluate the productivity' of 
resources: water, solar radiation, soils and C0 2 . The annually 
Potential Utilizable Water Resources (PUWR) consists of four 
Diagnosis of water management practices can help to keep the 
managers responsible for water diversions alert. Information on 
time accumulated water consumption and crop yield is a 
cornerstone for evaluating productive use of land and water 
resources (Wolff and Stein. 1998; Sakthivadivel et al., 1999). 
One example of experimental results on wheat yield per unit 
evaporation collected from internationally published data is 
15 n 
Yield/evaporation (kg/m3) 
Fig. 1 Return of wheat (grain yield) to water consumption (evaporation) compiled from 87 international publications