Veronika Kopackova, Czech Geological Survey (Czech Republic)
Michal Rajchl, Czech Geological Survey (Czech Republic)
Daniel Nývlt , Czech Geological Survey (Czech Republic)
Jiří Šebesta, Czech Geological Survey (Czech Republic)
Tomá? Hroch, Czech Geological Survey (Czech Republic)
Jan Vít, Czech Geological Survey (Czech Republic)
Sechua desert, the northern part of Peru, represents a unique system characteristic for minimum precipitation, therefore all the surface water income is regulated by the two rivers, Chira and Piura, draining water from the Andean part of their catchments. Water inflow of those two rivers is controlled by seasonal precipitation changes typical for a dry and wet season. Every decade is this relatively steady system affected by a phenomenon that is known as the El Niño/Southern Oscillation (ENSO). El Niño is the occasional development of a warm ocean current along the Peru Coast as temporary replacement of the cold Peru Current, which normally flows in this region.
As this happens, the easterly trade winds, typical for this part, collapse or even reverse due to a change in air pressure caused by the temporary warm current.
The wet weather conditions normally present over the western Pacific moves to the east and bring heavy waterfalls that in the end bring enormous water inflow for the Chira and Piura rivers. In such a case regular river network respond to those extremes with unpredictable changes in directions of river channels. Presented study covers the total area of 22 600 km2 and combines different spatial and spectral mapping techniques while utilizing diverse Earth Observation data: (a) multitemporal LANDSAT scenes from the 70ties, 90ties and 2000; (b) 12 scenes of ASTER acquired during 2006-2007; (c) SRTM 90-m DEM (level 3). The SRTM data were used to analyze geomorphological landforms while employing the spatial analyses to classify variations in slope and degree of convexity/concavity in the study area. Multitemporal LANDSAT scenes were used to classify general land cover and analysis of ASTER scenes in combination with laboratory spectral measurements (ASD Fieldspec spectroradiometer) of the mineral/rock field samples allowed creating mineral abundance map of silicate, carbonate and clay component of different sedimentary formations and mapping distribution of evaporites in the desert. Results coming from the classifications of diverse and multitemporal Earth Observation data brought key information that enabled a global change detection assessment of the lower-catchments areas of Chira and Piura rivers in the Sechua desert during the last three decades.