The water quality investigation using GIS and multivariable analysis in a semiarid region reservoir

Abstract

-This study was carried out in the Serrote reservoir, sited in the Groaíras watershed at the northeastern region of Ceará State, Brazil. The aim was to investigate the temporal and spatial variability of water quality. Data investigation was processed using multivariate analysis/cluster analysis and GIS techniques. Samples were taken in four stations spreading out over the water body during five campaigns of collection (February, May, August/2007 and May, August/2008). The water quality parameters analyzed were: Electric Conductivity (EC), pH, Dissolved Oxygen (DO), temperature, chlorophyll 'a' concentration and Total Phosphorus (TP). Two homogeneous groups were identified, which expressed the inter-annual seasonality influence in the water quality. The highest concentration of investigated attributes occurred in 2008. At that year, the depth of the annual rainfall was 53% above the annual average. Chlorophyll 'a' and total phosphorus defined the dissimilarity between the two groups. Group 1 was composed with the better water quality and concentrations of attributes were close to the recommended limit defined by resolution 357/05 of CONAMA. Whereas Group 2 presented average concentrations of chlorophyll 'a' and total phosphorus two times greater than the ones registered in Group 1, there for been above the limit established by CONAMA (357/05) for human consumption. The reservoir presents characteristics that point toward eutrophization due to the use and management of the soil around said reservoir.Key words -Water quality. Cluster Analysis. Eutrophization.Resumo -Este estudo foi conduzido no açude Serrote (barragem Edson Queiroz), localizado na bacia do rio Groaíras, no norte do estado do Ceará, objetivando-se investigar a variabilidade espaço-temporal da qualidade da água. Foram coletadas amostras de água em quatro pontos do corpo hídrico, durante os meses de fevereiro, maio e agosto de 2007 e maio e agosto de 2008, totalizando cinco campanhas. Os parâmetros considerados neste estudo foram Condutividade Elétrica da água (CE), potencial hidrogeniônico (pH), oxigênio dissolvido (OD), temperatura (T), fósforo total (P) e clorofila 'a'. As investigações dos dados foram realizadas pelo emprego de análise multivariada (análise de agrupamento) e técnicas de geoprocessamento. Dois grupos homogêneos foram formados independentes do ponto de amostragem, expressando assim, a maior influência da sazonalidade interanual. O estudo mostrou que as maiores concentrações dos elementos investigados foram registrados no ano de 2008, que apresentou totais pluviométricos superiores a média normal em 53%. A dissimilaridade entre os dois grupos foi definida pela clorofila 'a' e o fósforo total. O grupo 1 apresentou águas de melhor qualidade, com concentrações em torno dos limites estabelecidos pelo CONAMA (357/05). Já o grupo 2 apresentou concentrações médias da clorofila 'a' e do fósforo total duas vezes superiores as registradas no grupo 1, estando as mesmas sempre superiores aos limites estabelecidos pelo CONAMA (357/05) p...

Assessment of the water quality in a large reservoir in semiarid region of Brazil

“…The dynamics of sodium, calcium, magnesium and potassium (Table 4) in the surface waters of the Orós reservoir present low spatial variation; similar behaviour was found by (Meireles et al, 2007;Alexandre et al, 2010) in studies of the quality of surface water.…”

“…Two of the main artificial sources of phosphorus are domestic sewage and agricultural fertilizers (Alexandre et al, 2010;Shrestha & Kazama, 2007). In the areas of land usage and occupation around the Orós reservoir, 59.83% of the total usage has already undergone change (natural pasture and land management, poultry farming and rice crops) (Soares et al, 2009), and only 11.22% of households are connected to the sewage network in the Upper Jaguaribe basin (IPECE, 2010).…”

“…As the demand for water resources in the world increases, the likelihood of providing fresh water decreases. As an aggravating factor, in recent decades water quality has been deteriorating rapidly, which prevents the use of important reservoirs (Alexandre et al, 2010;Palácio et al;, Li et al, 2011Guedes et al, 2012). These studies demonstrate the tendency of water resources to become ever scarcer, both quantitatively and qualitatively, should no clear action be taken which is aimed at improving the management of the supply and demand of water for different uses.…”

“…It therefore becomes necessary to use tools which allow the reduction and grouping of the large amount of information (historical data) arising from studies of the varying quality and quantity of water resources, involving a multivariate function of several aspects in such a way as to allow the interpretation and recognition of trends over time and in space (Alexandre et al, 2010;Li et al, 2011;Zhang et al, 2011).…”

Land use and trophic state dynamics in a tropical semi-arid reservoir

“…The process of eutrophication of the water in reservoirs, especially when intended for multiple-usage, has often been studied by researchers in different parts of the globe (ALEXANDRE et al, 2010;KAGALOUA;PAPASTERGIADOUB;LEONARDOSA, 2008;KARADŽI et al , The enrichment of bodies of water is associated with increased primary production and the occurrence of episodes of excessive development of algae or aquatic macrophytes, which may affect the use of the water for supply, for energy production, for recreation and for the protection of aquatic life (FERREIRA, 2004;LACERDA et al, 2004). In reservoirs with a slowed water velocity, prolonged presence and high nutrient concentration increase the tendency to eutrophication of the water bodies (SPERLING;GOMES, 2008;ZENG et al, 2006).…”