Analysis of land use and occupation in the water quality at two sub-basins of Caxias do Sul City

Abstract

The use and land cover can directly influence in the quality and in the availability of water resources, whether by accelerated urbanization, by the removal of vegetation and the agricultural use. The impacts may vary according the use, the organic load supply, metal nutrients and contaminants and the drag of sediment affecting the water quality and the balance of aquatic ecosystems. This research was aimed to evaluated the influence of use and land use on water quality of river basins of the rivers Piaí and Tega, in Caxias do Sul-RS. Analyzed for such the Water Quality Index (WQI) and Toxicity (TI) in 5 points from River Piaí (P1 to P5) and 12 from River Tega (T1 to T12). Were realized 12 campaigns between September / 2012 to July / 2014. To develop the maps the use and occupation land were used Landsat 8 satellite images combined with the supervised classification with the maximum likelihood algorithm and Gaussian screen scanning in trouble spots. For the classification of maps were defined 7 classes of use, as follows: native forest, field, forestry, agriculture, bare soil, urban and water depth. For the classification of maps were defined 7 classes of use, as follows: native forest, field, forestry, agriculture, bare soil, urban area and water depth. It was concluded that the low water quality of points as P3 and P4 from River Piaí and points T1 to T9 from River Tega is the reflection the use and occupation of the soil, the release of effluents from point sources, such as homes and industries that do not have effluent treatment plant or whose treatment is not sufficient to meet the discharge standards prescribed by the laws.

http://dx.doi.org/10.18226/23185279.v4iss1p1