PARENT SESSION
Poster Session #72: Water Relations II.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC
134
Quantification of the effects of deforestation on hydrological services in the watersheds of Veracruz, Mexico.
Manson, Robert*,1, 1 Instituto de Ecología, A.C., Xalapa, Veracruz, Mexico
ABSTRACT- Veracruz receives 12% of the precipitation and 24% of the overland flow of water in Mexico. Extensive deforestation in Veracruz has resulted in a 22% loss of forests in the last 7 years alone with forests covering only 18% of this state. Such deforestation may drastically alter the hydrological services provided by watersheds in the region. For example, over the last decade flood frequency and severity in Veracruz and several other neighboring states has increased and resulted in several $US billions in losses. Little information is available concerning the nature of the relationships between flood risk and deforestation in these states, which might assist efforts to mitigate flood risk. Vegetation and land use maps derived from aerial photos and Landsat ETM images (scale 1:250,000) in 1987 and 2000 were used to calculate deforestation rates over a 13-year period in 14 watersheds of the state of Veracruz. These rates were then compared with hydrological and climatological data from permanent monitoring stations of the National Water Commission located in each watershed. Forest cover in some of these watersheds increased 10-20% while the vast majority exhibited losses of up to 70% during the study period. After controlling for effects of watershed size, average rainfall, soil type, slope, and other land uses, deforestation was strongly associated with changes in total yield and flow regime in study watersheds. Total yield was positively related to deforestation, whereas rainy season and dry season flows were found to increase and decrease, respectively, as deforestation progressed. These results, combined with activities designed to increase awareness about ecosystem services, are being used to promote forest and biodiversity conservation in the region.
KEY WORDS: ecosystem services, flooding, deforestation, watershed