Land use and water quality in two sub-basins
Abstract
The study evaluated the effects of land use and occupation in water quality in two sub-basins located in the State of Paraná, Brazil. The first sub-basin has 69.8% of native vegetation (natural) and the other has 54.1% of the land cultivated (anthropic). Samples were collected from April to December 2015, analyzing the following parameters: dissolved oxygen, temperature, electrical conductivity, pH, total dissolved solids, turbidity, color, biochemical oxygen demand, total nitrogen, total phosphorus and fecal coliforms. The natural sub-basin presented, significantly, better water quality. Total phosphorus, biochemical oxygen demand and fecal coliforms exceeded the legal limits on the anthropic sub-basin. At this sub-basin correlation was found between cumulative rainfall of five days with turbidity and fecal coliforms, two days cumulative rainfall and total nitrogen, as well as between air and water temperature, affecting the dissolved oxygen, pH, electrical conductivity and fecal coliforms. In the natural sub-basin correlation was found between cumulative rainfall of two days and turbidity, total dissolved solids and electrical conductivity.
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Introduction
Water is a fundamental substance and its peculiarities are important indicators of environmental quality because, during its course, it acquires characteristics derived from the environment.
The characteristics of a watershed have an important influence on water quality, such as landscape and spatial configuration (Bateni et al, 2013) as well as land use (Kamjunke et al, 2013; Wang et al, 2014; Meneses et al, 2015; Valle Junior et al, 2015; Durło et al, 2016). The watershed is the territorial unit chosen for the study and management of water resources, where the systemic view is fundamental for understanding the relative phenomena.
The removal of natural vegetation to give place to human activities affects the quantity and quality of water, since the vegetation influences the hydrological cycle, the water availability and the biogeochemical cycles. Importance has been directed to riparian vegetation that acts as a "filter", retaining substances and sediments that can be carried to water bodies (Sweeney and Newbold, 2014).
Despite the economic benefits provided by changes in land use, there is, simultaneously, a decrease in the ability of the environment to sustain human activities (Foley et al, 2005). In this context, public supply sources must receive special attention for their social and economic importance.
The objective of this study was to analyze the water quality in two sub-basins, with different land uses, which are part of the São João watershed-PR, used as the supply source for the city of Carambeí – PR, in southern Brazil.
Conclusion
The natural sub-basin presented better water quality than the anthropic sub-basin. Upstream farms and the lack of Permanent Preservation Area in springs contribute to fecal contamination and high values of total phosphorus, total nitrogen and biochemical oxygen demand in the natural sub-basin. The predominant use of agriculture, the absence of riparian vegetation and the use of synthetic and natural fertilizers degrade water quality in the anthropic sub-basin. Precipitation and atmospheric temperature tended to influence the analyzed parameters.