Water balance in a tropical rainforest at Los Tuxtlas, Mexico

Background/Question/Methods Water controls by far the ecosystems dynamics, and is also indispensable resource for the social and economic development. So the hydrological functioning of ecosystems is an appropriate pathway to determine physical, ecological and social challenges involved in a given area. With these considerations, the Mexican Network of Long-Term Ecological Research (MEX-LTER Network) has a research proposal in which, from an ecosystem perspective, using watersheds as units of study, water balance will be estimated for analyze resources condition. Los Tuxtlas region is located in the coastal plain of the Gulf of Mexico, southern Veracruz State. The Tropical Biology Station at the Universidad Nacional Autónoma de México is located in the influence area of the selected watershed. This is defined as a morphographic and means the dividing line between two drainage basins where surface water drains towards the same point. The watershed at this point of Los Tuxtlas, is formed by volcanic soils with evergreen vegetation (tropical rain forest) and abundant rainfall which is a constant input of water to the ecosystem. The Water Balance will provide us the inputs and water loss for this place in a time period. The main objective of this work was to define the watershed in Los Tuxtlas region with an Information of Geographic System, and to estimate the hydrological parameters for water balance determination using the Thornthwaite–Mather method (1955).

Results/Conclusions The physical and hydrological parameters with information from the basin, were obtained from databases of weather stations located in the area. Calculation of the water balance got to count the profits of water by precipitation: 4725 mm annually; evaporation losses (actual and potential): 1439 mm annually; runoff, which becomes annually from 3158 mm (deep drainage). The results of the water balance show moisture in the soil almost constant throughout the year (400 mm). That ensures a positive water balance in the region. However, due to intensive land use changes at our study area due mainly to cultures and livestock-farming, it is necessary to analyze most complete form the basin to conduct a new assessment of the condition of water resources in the region.