The effects of afforestation on Uruguay's water resources

Abstract

The development of industrial afforestation in Uruguay leaded to the substitution of natural grasslands mainly used for cattle grazing by Eucalyptus and Pinus plantations. This land use modification caused concern regarding its effects on the country’s natural resources, particularly water and soils. Therefore, research studies were undertaken in order to find hydro-environmental indicators of sustainable forest management. This paper shows the progress and current state of knowledge regarding the effects of afforestation on Uruguay’s water resources, based on investigations carried out by the University Net on Agricultural Engineering. The paper describes studies in a macro-basin of 2.097 km² , with a forestry surface of about 540 km² and two experimental micro-basins with different land cover, located in the same region, under similar hydrological conditions. Available results allows to quantify trends related to: 1) the effects on hydrographs (runoff volumes and maximum peaks); 2) the effect of the Eucalyptus and Pinus plantations on the macro-basin’s runoff, distinguishing between annual and seasonal behavior, for the period before afforestation (1975-1993), where the cattle use prevailed, and the period after afforestation (1994-2002); 3) the amount of direct rainfall and stemflow, two of the three components of rainfall redistribution in forests; 4) the relationship between soil humidity and field capacity.