Hydrological consequences of land use changes on a dammed urban basin

Anthropic interventions on a territory tend to affect the hydrological dynamics and the surface runoff process. This work was aimed to analyse the spatial and temporal changes in land use and land cover (LULC) as well as their incidence on surface runoff in Lago del Fuerte reservoir basin (Argentina). This basin is located in the main tourist area of the region. In recent years it has experienced a significant population increase, which has not been accompanied by water and sewer services and lacks territorial planning. This situation can alter the hydrological dynamics of the lake’s contribution basin and of the reservoir itself. Geographic Information Systems tools were used for the morphometric characterization of the basin, LULC mapping, and for the identification of the hydrological soil groups. Curve Number (CN) method was applied to estimate the surface runoff for the years 2003 and 2020. Rock outcrops (30%) remained unchanged. In 2003, brush-forbs-grass dominated (30%), followed by grassland (12%), and open spaces (8%). However, grassland and open spaces were the most affected LULC by 2020, because their areas were partially replaced by high (7%) and low density (2%) residential uses. The study evidenced that replacement of vegetation by urbanisation increased the CN values, while CN decreased in renatured lands. Therefore, the average CN values in the basin were similar due to the compensation between zones. This work contributes to the integrated water resource management of the basin in order to protect its environmental quality and the functionality of the reservoir.