ABSTRACT

The Sechura desert, in the northern part of Peru, represents a unique system characterized by minimum precipitation and therefore all the surface water input is regulated by the two rivers, the Chira and the Piura, draining water from the Andean part of their catchments. Water inflow in these two rivers is controlled by seasonal precipitation changes typical for the dry and wet seasons. Once in every decade, this relatively steady system is affected by a phenomenon that is known as the El Niño/Southern Oscillation (ENSO). The wet weather conditions normally present over the western Pacific move to the east and bring heavy rainfalls that, as a consequence, bring enormous water inflow for the Chira and Piura rivers. River fluvial systems respond to these extremes by unpredictable changes in the geometry and positions of the river channels. The present study covers a total area of 20 000 km2 and combines various mapping techniques while utilizing diverse Earth Observation data: (a) multitemporal Landsat scenes from 1973, 1984, 1985 and 2000- 2001; (b) 6 scenes of ASTER acquired during 2006-2007. Multitemporal Landsat scenes were used to reconstruct the fluvial networks of the Chira and Piura Rivers and to classify surface material in the desert environment. Analysis of ASTER TIR scenes allowed creation of a mineral abundance map of quartz-rich, carbonate-rich and gypsum-rich sediments. The results derived from a study utilizing diverse and multitemporal Earth Observation data provided key information that enabled a synoptic change detection assessment of the lower-catchments areas of the Chira and Piura Rivers in the Sechura desert during the past three decades.

MOTS CLÉS

Multitemporal analysis, emissivity ratios, land cover, Sechura desert, NW Peru, Landsat, ASTER TIR, ENSO.