Impact Assessment of Non-Point Source Pollution with the L-THIA Model

Abstract

In the present study, the L-THIA (Long-Term Hydrologic Impact Assessment) model was used for preliminary assessment of the long-term hydrologic impacts of land use changes in the Mineirinho watershed (Sao Carlos, Brazil). Thus, considering the occupation policies defined by the municipal master plan, two land use scenarios were constructed (2009 and 2025), which allowed estimation of the annual runoff volume and pollutant loads. The urbanization may increase runoff volume and decrease the groundwater recharge and evapotranspiration. Moreover, the changes in human activities in a watershed influence the amount and type of pollutants that are disposed of on the surface and then conveyed by runoff during precipitation. This paper aims to analyze the impacts of urbanization in the Mineirinho basin on the runoff and on the associated non-point source pollution. It was concluded that the land use changes in the Mineirinho watershed will occur in moderate proportions. In the future, 68% of the annual runoff will be generated by residential land use. In 2009, this use accounted for 36% of the total water that flowed over the surface. The nutrients increase between the two scenarios was 4.47% and 10.86% for nitrogen and phosphorus, respectively.