Analysis of land use change and soil erosion in an Andean watershed

The analysis of past land use change and the projection of land use change scenarios into the future have been an integral core in the Nanegal study site during Phase I of SANREM Andes. A similar methodology is now being applied to the Cotacachi region in the temperate inter-Andean valley of northern Ecuador. Indigenous populations have lived in this area for thousands of years and have employed farming practices well-suited to the climate and topography of the region during much of that time. Spanish colonization and the introduction of the hacienda system resulted in marked changes in the agricultural context, and the land reform of the 1960s and the arrival of the Green Revolution in the 1970s produced further impacts on land use and land management in the area. Stereo pairs of aerial photographs of the years 1963, 1978, 1993, and 2000 are being interpreted to analyze land use change over the past 40 years. Initial results indicate a marked decline in agricultural production in the high zone (above 3,000 m.a.s.l.) and an increasing urbanization in the low zone (around 2,500 m.a.s.l.). Based on the land use change analysis, soil erosion and sedimentation are estimated over the 40 year study period and its impact on water quality is evaluated using WaTEM (Water and Tillage Erosion Model).