Spatial Patterns of Water Quality in the Cuiabá River Basin, Central Brazil

Abstract

This study evaluates the spatial patterns of land occupation and their relationship to water quality in the Cuiabá River watershed, one of the main affluents of the Pantanal floodplain. The impact of farming and other land occupation forms were studied using a three year time series. Monitoring included 15 parameters at 21 stations with a total of 1266 different samples. Ten stations along the Cuiabá River were ordinated by Principal Component Analysis (PCA). For an exploratory analysis in the spatial domain, sub-basins of the Cuiabá watershed were classified according to mean concentrations of selected water quality parameters. Supervised classification of digital Landsat ETM imagery and standard GIS techniques were applied to parameterize land use and occupation according to a watershed scale. Redundancy Analysis (RDA) was then used to evaluate impacts of environmental and socio-economic factors on water quality. A Cuiabá headwater station only shows slightly elevated total coliform counts and concentrations of nutrients in the river after it passes regions of extensive cattle farming. After the confluence with the Manso River, nutrient and COD concentrations increase significantly, receiving loads from sub-basins under intensive agricultural land use, with mean annual concentrations up to 1.74 mg/L of total nitrogen (Kjedahl). Sub-watersheds with intensive fishing culture activities were shown to have significant impact on nitrogen concentrations, reaching mean concentrations of 2.66 mg/L of total nitrogen in the affluents. Most serious biological and chemical water pollution can be observed at stream outlets in the urban agglomeration of Cuiabá/Várzea Grande. Affluent pollution is reflected in the water quality of the Cuiabá River: subsequent monitoring stations in the urban area are ordinated on a gradient of increasing degradation of chemical and biological water quality. The auto-depuration capacity of the Cuiabá River is intact, but elevated concentrations of Phosphorous and Chemical Oxygen Demand can be observed as far away as the Pantanal floodplain, about 120 km downstream from the urban agglomeration.

Quality of surface water related to land use: a case study in a catchment with small farms and intensive vegetable crop production in southern Brazil

“…In addition, in both, 71 % of the agricultural area is on greater than 13 % slope (Table 4). Zeilhofer et al (2006), studying water quality in the Cuibá River Basin, central Brazil, for three years in 21 monitoring sites, observed that total N (Kjeldahl) concentration increased significantly in the sub-basin devoted to intense agricultural land use. However, the total N (Kjeldahl) mean annual concentration (1.74 mg L -1 ) of that study was much lower than the mean annual value from the Campestre catchment (6.85 mg L -1 ), which was explained by heavy N fertilization (organic and mineral fertilizers).…”

“…Soil use and management, according to their capacity, as well as the adoption of conservation techniques are fundamental for preserving water quality (Zeilhofer et al, 2006;Diebel et al, 2009). Preservation of native vegetation prevents water pollution (Yang & Zang, 2003;Mehaffey et al, 2005;Yang et al, 2007), especially in the riparian zone, which acts as a filter.…”

Metais potencialmente tóxicos em rios a montante do Pantanal Norte

“…Apesar de existirem vários programas de monitoramento de qualidade de água nas bacias dos rios Cuiabá e São Lourenço sob a responsabilidade de instituições governamentais ou universidades, poucos destes programas avaliaram a presença de metais (Thomé Filho et al, 2006a;2006b;2010;Zeilhofer et al, 2006;Gonçalves et al, 2015;Lima et al, 2015).…”

Analysis of thermal conductivity in a seasonal flooded forest in the northern Pantanal

“…Extensive cattle farming, adapted to the flooding cycles, is the predominant land use inside the Pantanal. Human activity in its contributing watersheds, however, endangers the floodplain environmental integrity, increasing, for example, the sediment (Wantzen, 2006), nutrient (Zeilhofer et al, 2006).…”