Ana Célia Maia Meireles

A new proposal of the classification of irrigation water.

A study on surface water quality in the Acarau Basin, in the North of the state of Ceara, Brazil was performed. Qualitative dynamics of water flowing to the Acarau River that supplies water to the irrigation project in the area was evaluated. Multivariate Factor Analysis/Principal Component Analysis was used for evaluation of water quality in order to develop a water quality index (WQI) that reflects soil salinity and sodicity risks and water toxicity to plants. From April/2003 to September/2005 water were sampled from ten sampling sites covering the basin, where physical and chemical parameters that contribute to the WQI were evaluated. The results showed that the use of water for irrigation in the Acarau basin, according to the proposed WQI, are potentially prone to cause toxicity (crop cycle) and sodicity problem in the long run, if the soil-water-plant is not carefully monitored.

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

Water body eutrophication process has been a serious problem around the world, especially in semiarid and arid region where main approach to storage water is reservoir. The aim of this work was to investigate the spatial and seasonal variability in water quality of a reservoir in a semi-arid tropical region with regards to its trophic state, and to identify the sources of nutrient input to the reservoir. Essa pesquisa foi realizada no reservatorio Oros, segundo maior do estado do Ceara-Brasil. This research was developed in the Oros reservoir, the second one most important reservoir in Ceara State, Brazil. Samples were collected bimonthly during the period April 2008 to April 2010, from sex sampling points representing the outlet of tributaries, and one point down of the dam. The study included the following variables: total phosphorus, transparency and chlorophyll-a. Trophic state was evaluated by application of the Carlson modified Trophic State Index (TSI). Maps of the spatial and seasonal dynamics of the water quality in the reservoir were constructed using GIS soft. According to the average values of total phosphorus (> 0.050 mg L -1 ), the waters can be classified as eutrophic. The highest concentrations of chlorophyll-a were found during the dry season, with values ranging from 3.8 to 26.5 µg L -1 , showing high temporal and spatial variations. The waters presented as eutrophic regarding average TSI, at all points sampled. The results indicate a deterioration in water quality and the need for intervention to reduce the release of waste, and thus improve the trophic state of the waters of the Oros reservoir.Water body eutrophication process has been a serious problem around the world, especially in semiarid and arid region where main approach to storage water is reservoir. The aim of this work was to investigate the spatial and seasonal variability in water quality of a reservoir in a semi-arid tropical region with regards to its trophic state, and to identify the sources of nutrient input to the reservoir. Essa pesquisa foi realizada no reservatorio Oros, segundo maior do estado do Ceara-Brasil. This research was developed in the Oros reservoir, the second one most important reservoir in Ceara State, Brazil. Samples were collected bimonthly during the period April 2008 to April 2010, from sex sampling points representing the outlet of tributaries, and one point down of the dam. The study included the following variables: total phosphorus, transparency and chlorophyll-a. Trophic state was evaluated by application of the Carlson modified Trophic State Index (TSI). Maps of the spatial and seasonal dynamics of the water quality in the reservoir were constructed using GIS soft. According to the average values of total phosphorus (> 0.050 mg L -1 ), the waters can be classified as eutrophic. The highest concentrations of chlorophyll-a were found during the dry season, with values ranging from 3.8 to 26.5 µg L -1 , showing high temporal and spatial variations. The waters presented as eutrophic regarding average TSI, at all points sampled. The results indicate a deterioration in water quality and the need for intervention to reduce the release of waste, and thus improve the trophic state of the waters of the Oros reservoir.

Runoff and soil and nutrient losses in semiarid uncultivated fields

Although water erosion is the principle agent responsible for soil degradation, field data on the impacts of erosion, due to high operational costs and measurement difficulties, are scarce, especially in semiarid regions. In this context, the aim of this study was to evaluate runoff and soil and nutrient losses in uncultivated areas in the semiarid region of the state of Ceara in Brazil. The experiment was conducted in a 20 m2 erosion plot that was uncultivated and populated with herbaceous plants. Data were collected during the rainy season from January to May 2009. Monthly water losses from overland flow ranged from 3.4 to 168.9 mm, representing 1.8 to 42.3% of the total monthly rainfall for January and April, respectively. Soil loss from erosion totaled 2,166.6 kg ha-1. In February, soil losses were 834.3 kg ha-1, corresponding to 38.5% of the total value. The rainfall erosivity index (EI30) was 5,716.4 MJ mm ha-1 h-1. The observed high variability of soil losses in individual events was influenced mainly by the antecedent soil water content. Although this study used only one year of observations, the findings are important for land use planning, especially in the semiarid region of Brazil, where datasets are scarce.

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

The aim of this study was to identify spatial and temporal variations in water quality of Oros reservoir, Ceara, Brazil, as well as the sources of contamination. To get this information the Principal Component Analysis (PCA) and Cluster Analysis (CA) was used. Water samples were collected at seven (geo-referenced) points, from April 2008 to March 2011, totalling 4,032 samples. The following attributes of the waters were analysed: temperature, pH, CE, Ca2+, Mg2+, Na+, K+, Cl-, HCO3-, SO4--, turbidity, colour, Sechi transparency, TS, TVS, TFS, TSS, VSS, FSS, TDS, DO, BO5D, total phosphorus, soluble orthophosphate, EC, TTC, total ammonia, TKN, nitrate, SAR and chlorophyll-a. The PCA promoted the reduction from the 32 initial variables to 14, accounting for 84.39% of the total variance. The major factors responsible for water quality composition are: the natural weathering of geological soil components; the entrainment of suspended solids through surface runoff from agricultural areas; and anthropogenic action in the Upper Jaguaribe basin in Ceara. The similarity of the water of the Oros reservoir allows a reduction in the number of sampling points, which may result in significant cost savings without sacrificing the water quality monitoring. The similarity of the waters was influenced by anthropic activities being carried out near the reservoir and all along the watershed.

Similaridade e fatores determinantes na salinidade das águas superficiais do Ceará, por técnicas multivariadas

Tecnicas de estatistica multivariada foram empregadas com o objetivo de identificar a similaridade dos reservatorios superficiais do Ceara, com relacao a salinidade das aguas e identificar os fatores determinantes da qualidade das aguas. Os dados utilizados foram provenientes do banco de dados da Companhia de Gestao dos Recursos Hidricos do Ceara, no periodo de 1998/2009, no total de 807 amostras de 48 reservatorios. Os parâmetros considerados foram: Cl-, Ca2+, Mg2+, Na+, HCO3 -, CE e RAS. A analise de agrupamento hierarquico formou quatro grupos distintos, sendo determinantes os tipos e concentracoes dos sais analisados. Nos grupos 1 e 2 a salinidade da agua e definida principalmente pelas condicoes naturais de solo e clima da regiao e nos grupos 3 e 4, alem desses fatores, a influencia antropica. O emprego da analise de fator/analise de componente principal promoveu a reducao de sete caracteristicas das aguas superficiais do Estado Ceara, para dois componentes, sendo que o primeiro componente explicou 57,28% e o segundo, 26,77% da variância contida nas sete variaveis. Os parâmetros mais representativos na variabilidade da salinidade das aguas foram Cl-, CE, Na+ e Mg2+, relacionados com a solubilidade dos sais.

Importância relativa dos íons na salinidade de um cambissolo na Chapada do Apodi, Ceará

The main objective of this study was to develop and to evaluate models in order to identify the influence of ions on the values of electrical conductivity of saturation extracts (CEes). The samples were colleted in areas under irrigated banana trees (with subsurface and surface water) and native forest areas. Samples were taken in two areas in the Apodi Plateau, State of Ceara. One area was in Quixere County and the other was at the Jaguaribe Apodi Irrigation District - DIJA, in Limoeiro do Norte County. Research was done during two periods, one from December 1999 to December 2000 and the other from September to December 2001. The 312 soil samples were taken to the laboratory for analyses of extract saturation for determination of CE and the ions Na+, Cl-, Ca2++Mg2+ and K+. A stepwise regression analysis model was tested, using CEes as the dependent variable and analyzed ions as the independent variables in all tested models. Results obtained through statistical models showed that the ion Cl- had greater influence in the elevation of the CEs values followed by the ions Ca2++Mg2+ in Quixere. In the soil of the DIJA area, for layers of 30-60 cm, the most important ion was Na+ followed by Cl-.The linear models for the several layers, for both areas, presented a good accuracy, as the simulated values were very close to those observed.

Adapting the National Sanitation Foundation water quality index to the Brazilian semiarid

Knowledge of the water quality of a reservoir used for human consumption is important. Water quality indices are used to facilitate understanding of this quality. This study aimed to adapt and compare the water quality index of the National Sanitation Foundation to the physical, chemical and biological conditions of artificial reservoirs in regions with tropical semiarid climate and its spatio-temporal variability. Twelve water samples were taken between April 2008 to April 2010 in seven sampling points distributed in Oros reservoir in the southern of Ceara. Water quality attributes that were monitored and used for calculation and adjustment of the index were: pH, temperature, dissolved oxygen, biochemical oxygen demand, total phosphorus, nitrate, total solids, turbidity and fecal coliform. From them, we used the Principal Component Analysis to determine the weights to be associated with the parameters of the water quality index and adapt it to reservoirs of semiarid climates. The water quality of the reservoir was classified as regular for most of the study period. Although varying with rainfall, there was effect of seasonality on water quality. It was observed that the index adapted to semiarid climate regions is statistically different from indices from other regions. However, the difference is observed only in sensitivity and weigths of determining attributes quality.

Investigação de mudanças do status salino do solo pelo emprego de análise multivariada

This work was carried out to investigate the multivariable statistics/cluster analysis as a tool to identify the similarity of irrigated fields. The investigation was conducted in three areas. One was an undisturbed native area (MN) and the others, two irrigated field in the Irrigated District of Jaguaribe-Apodi (DIJA) situated in the municipality of Limoeiro do Norte and Quixere, Ceara State, Brazil. Soil was sampled monthly, from December/1999 to December/2000, and also from September to December of 2001 in the depths of 0-30, 30-60 cm. The attributes considered in this study were: EC (electric conductivity of soil solution), Ca2+ + Mg2+, Cl-, Na+ and k+ and SAR (sodium adsorption ratio). The Cluster Analysis application identified the similarity of studied attributes and three homogeneous groups were identified. The studied attributes values from MN were statistically different (p < 0.001) from those of irrigated fields. According to the results, Cluster Analysis showed up as a suitable tool to define the similarity independent of sample position in time and space. This fact expresses that Cluster Analysis technique can be applied to identify the similarity in areas with high or little salinization risk.

Evaluation of Spectral Similarity of Water in Urban and Rural Reservoirs Using Cluster Analysis

The objective of the study was to compare the spectra of two reservoirs: a urban reservoir (Santo Anastacio) and a rural reservoir (Oros) and to measure their similarity by means of cluster analyses. Sixteen radiometric measures were carried out in each reservoir, using the FieldSpec®3 Hi-Res spectroradiometer. Water samples were taken at 30cm depth, concurrently with spectral measurements, for analytical determination of chlorophyll-a (Chl-a) and total suspended solids (TSS). Electrical conductivity (EC), pH, and Secchi depth transparency (SD), were also measured. Cluster analysis, based in the agglomerative hierarchical method of the spectra resulted in three groups. Group 1 was characterized by high concentrations of Chl-a, ranging from 61.97 to 171.91 µg/L. Group 2 by Chl-a, ranging from 14.79 to 57.19 µg/L and Group 3 where the opticall active component controlling the water reflectance was the SST with concentration varying between 15.25 to 99.00 mg/L. All spectra from Santo Anastacio (Urban) reservoir were classified in the group1, whereas the spectra from Oros were included in Groups 2 and 3. The results show that the cluster-analysis technique of the water spectra can be used to discriminate water masses of urban reservoirs from those of rural reservoirs provided that their optically active components are different.