Navone, Stella Maris 
Introduction 
Desertification increases in 650000 hectareas year by year in Argentine Republic .( 
Regional Workshops on Desertification - Program of National Action to Fight against 
Desertification (FAO, PNUMA, Secretariat for Natural Resources and Human Environment, 
1995. 
) According to the FAO-UNEP definition (1984) “desertification is the general expression of 
the economic and social problems,in conjuction with natural and induced processes,that lead to 
the destruction of the balance of the environment'thus ,the need of an integrated approach of 
socio-economic and biophysical factors for a proper assesment. 
Vegetation cover , water and wind erosion ,salinization,animal and human pressure 
(FAO,1984) were studied 
There are several similar valleys in the Northwest region .while in some of them 
desertification has been galloping during the last thirty years (Igarzábal, 1974; Navone et al, 
1996), turning them into vast deserts, Santa Maria valley presents the first symptoms of the 
processes.To avoid this problem it is very important to make a proper diagnosis of actual 
status of desertification in order to allow the monitoring of processes. In this region is logistical 
difficulty in obtaining ground data quickly,cheaply,and with an appropriate level of accuracy.That's 
why we need a tool like remote sensing data. The usefulness of the integration of optical and radar 
data was demostrated by Kierein Young (1997) in geology and Shimabukuro et al.(1998)in land 
cover. 
The objective of this research was to determine how useful could be the integration 
of radar and Landsat Thematic Mapper images mapping the earlier stages of 
desertification . 
Study area description: 
The region of the Arid Valleys of the Argentine Northwest, considering its basins, has an 
approximate area of 14,000,000 ha. It is characterized by its valleys and “bolsones” (*) found 
between high mountain ranges. Agricultural systems are exclusively under irrigation and cattle 
rearing is generally extensive, even in mountain slopes. 
The Santa María Valley, in Catamarca, is inside this system. This region is located 
between 25 and 26 15 Southern latitude and 65 to 66 Western longitude The climate is semi-arid 
(Thornwaite,1948) showing wide temperature fluctuations between day and night. Winter is the 
cold and almost dry season, with a mean rainfall of 10 mm; while summer is relatively warm and 
rainy (290 mm) The floor of the Valley is between 1000 and 1500 m. and various microclimates 
can be observed therein. 
The Torriorthent are the predominant soils in the alluvial fans and in the highest section of the 
upper terraces.The soils of the lower terrace of the Santa Maria river and its flood plain are 
Torrifluvents ,and Torrifluvents, associated with Torripsament.(Navone et al, 1995). Flora is 
typical of the “ Monte” formation .It is a shrub formation of 1 to 1.8 m height.Agriculture in the 
region is concentrated in irrigated oases The 66% of forest has been cut or has been 
overgrazing. 
RADARSat data 
.Three RADARSAT Standard mode images from wet season (January) and dry season 
(august ) were used in this study. RADARSAT sensor has been described in detail by 
Luscombe et al (1993) and their products by Denyer et al (1993) 
The images were obtained in the ascending pass from January 17”, 1998 and August 10",1997 
and May 20" 1998. 
Landsat Themathic mapper data: 
Three sets of Landsat Thematic Mapper (TM) data with six bands each were used in this study 
.Two of them from rainy season (March,1993 and January,1998) and one for dry season 
(august, 1997) 
Three bands (3,4 and 5) with full resolution (30 metres) were considered for the digital analysis. 
  
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000.