Monitoring and modeling of water quality in a semiarid watershed

ABSTRACT This paper aimed at presenting a methodology for evaluating the water quality at the Acarape do Meio catchment, in the Brazilian semiarid. The land use mapping and monitoring of water quality parameters enabled the identification of main polluting sources and the construction of a catchment diagnosis. According to the water quality modelling, a stretch of 37 km along the Pacoti River was classified as class 4, except for those ones located at the catchment headwater, which was classified as class 2. The main polluting sources contributing to the water degradation were the inefficient Sewage Treatment Plants, the lack of basic sanitation in rural areas, livestock and agriculture activities. The QUAL-UFMG model estimated an affluent phosphorous load at the reservoir entrance of 13.7 ton.year-1 for the concentration of 0.56 mg.L-1 and mean water discharge of 1.48 m³.s-1. The K1, Ks, Kd, Kb, Kspo, Koi and K2 coefficients were 0.45, 0.29, 0.68, 0.65, 0.1, 0.01 and 5.4 d-1, respectively. The impacts of political and infrastructural measures over the catchment were evaluated taking into account two scenarios: improvement of efficiency at Sewage Treatment Plants and implementation of effective public policies, which reduced significantly the affluent phosphorous load into the reservoir.