EFFECT OF DEFORESTATION ON RUNOFF OF A SMALL WATERSHED NEARBY MEXICO CITY, DURING 1977 TO 2001

摘要

Time series analysis of an area of 1,739 km2 for the 1973-2002 period using Landsat images (MSS and ETM), existing maps, orthophotos, and ground truth data (Garcia, et al., 2005) helped to select a representative small watershed to study the effect of deforestation on runoff. Cartographic modeling helped to simulate runoff of a small watershed (ca. 3,000 Ha) within Mexico City. Manipulation of land cover - land use, geomorphology, relief and soil maps allowed for watershed characterization. The infiltration map was obtained by crossing land cover - land use with the soil hydrologic condition type map. Watershed runoff estimation was performed with infiltration map and with precipitation map and both in IDRISI, Andes software. Results were similar in all scenarios (about 0.7 m~3 s~(-1)). Comparison of this result with available data of annual average, compiled over a 25-year span by CNA (Comision Nacional del Agua) indicates a very good correlation (0.63 m~3 s~(-1)) validating the watershed runoff modeling procedure performed in here. This analysis may be performed in other smaller or medium size watersheds leading to the better understanding of the hydrologic processes of the region and therefore to the more appropriate use and administration of this vital resource.