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In Honduras, as well as in many other developing countries, less than 60% of the population in Honduras has reasonable access to safe drinking water and its quality is decreasing at an accelerated rate. This study consists of assessing the stream flow patterns after land use changes in the 4,200-ha Rio Calan Watershed of Central Honduras. Streamflow modelling was conducted using SWAT (Soil and Water Assessment Tool), a computer-based program developed by University of Texas to predict the impact of land management practices on discharge and water quality at the watershed scale. This constitutes the first attempt to use SWAT under tropical conditions in Honduras.

To study the land use dynamics, three temporal land use covers: 1993, 1998 and 2000, were developed from Landsat images. Additionally, three hypothetical land use covers were also modelled: pine trees, grass land and agriculture. As a first step, the model was calibrated with data collected for 1 year in the field. Latter, the data bases containing: land use, soils, and climate data were adapted with field data and information collected from local agencies.

As a result, we obtained a 10-year hydrograph for each real and hypothetical land use covers. Around 600 ha of tropical broad leaf and pine forests (15% of the watershed area) were converted to subsistence agriculture from 1993 to 2000. SWAT simulations, showed that land use conversion caused a slight increase in streamflow values in the 10-year-hydrographs. The agricultural cover, a hypothetical scenario, showed the highest value on streamflow during the predicted time. The predicted stream values (SWAT outcomes) and one-year field measurements were compared and a small disparity was observed. SWAT proved to be a powerful tool for modelling streamflow patterns. Work is still in progress to improve SWATs data bases to Honduran-tropical conditions.