Eunice Maia de Andrade

Seleção dos indicadores da qualidade das águas superficiais pelo emprego da análise multivariada

Multivariate statistical technique, factor analysis/principal component analysis (FA/PCA), was applied to identify the human activity effects and natural processes on surface water quality in Low Acarau basin, Ceara, Brazil. Water samples were collected in four different campaigns from Feb/2003 to Mar/2004, at seven sampling stations sited in low Acarau watershed. Twenty-five physical, chemical and bacteriological parameters were examined in this study. The FA/PCA allowed the identification of the total variance. The best model was adjusted with four components, explaining 82.1% of the data variance. The first factor was mainly associated with suspended solids defining the erosion process and runoff; that is, a suspended solids component. The second factor was mainly associated with sewage, agricultural runoff and others non-pontual pollution; the third one was defined as an organic component and represents the anthropogenic activites; while the fourth was mainly correlated with soluble salt, expressing the weathering and leaching. Besides, the factorial analysis did not result in data reduction, since 18 of the 25 parameters have been kept to explain 82% of the data variance.

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.

Biophysics variables seasonality on surface in semiarid regions by using remote sensing

To investigate the rainfall regime effects over the albedo, NDVI (normalized difference vegetation index), net radiation and soil heat flux in a semiarid region (Northeast of Brazil), a study in the Trussu watershed was developed by using remote sensing. The study focuses on two images (Landsat 7 ETM+) provided by Instituto Nacional de Pesquisas Espaciais (INPE), from October 25, 2000 and July 24, 2001, each of them having a different rainfall regime (dry and wet seasons). The images were analyzed by using the SEBAL algorithm (surface energy balance algorithm for land). The results showed that the amount of rainfall affected the investigated variables, and the highest values of albedo were registered during the dry season. The NDVI presented high sensibility to rainfall regime, pointing out a high vegetation potential recover during the rainfall season. The NDVI along the Trussu River was up to 0.39, expressing the repair zone preservation. The watershed vegetation showed a high resilience power expressed by NDVI values in the year of 2001. Net radiation and soil heat flux were greater in the dry season, in this way expressing the effect of humidity on the energy balance.

Impacto da lixiviação de nitrato e cloreto no lençol freático sob condições de cultivo irrigado

Environmental impacts of nitrogenous fertilizers, pesticides and salts contained in irrigation are becoming an increasing concern, because they may move with soil water from root zone to groundwater. The aim of this research was to identify the irrigation management and the rainfall depth influence over nitrate and chloride concentration in the soil profiles, as well as the risk of water table pollution in the Irrigated District of Baixo Acarau (DIBAU), Ceara, Brazil. Soil samples were taken each 50cm deep soil profiles until to saturated zone (7m) in two different types of land use: irrigated area (S1) and native area (S2). Samples occurred during irrigation activities (Nov/06) and rainfall season (May/07). The water table was measured, monthly, from Dec/2003 to Nov/2005, Nov/2006, Mar and April/2007 in four shallow wells, two located in irrigated fields and the others in native. The greatest chloride concentration in the soil profiles was registered during rainfall season, suggesting the effect of sea-salt aerosols influence on chloride soil content. The greatest nitrate concentration occurred under irrigation period. Also, the results show that irrigation caused the groundwater concentration of NO3-N to increase from 1.52 to 19.3mgL-1, thereby, exceeding the standards on Regulation MS number 518/2004 and 357/2005 Resolution.

Fatores determinantes da qualidade das águas superficiais na bacia do Alto Acaraú, Ceará, Brasil

Factor analysis/Principal Component Analysis (FA/PCA) were applied to the data set on water quality in upper Acarau River basin (Brazil) to study the effects caused by human activities on water. Variables were measured at six key sampling sites (villages and agricultural areas) in four campaigns from February/2003 to March/2004. The samples were analyzed for pH, temperature, color, electrical conductivity, turbidity, nitrate, ammonia, sodium, chloride, potassium, sulfate, total hardness, calcium, magnesium, total alkalinity, alkalinity bicarbonate, total suspended solids, dissolved oxygen (DO), 5-days biochemical oxygen demand (BOD5), total phosphate, orthophosphate, chlorophyll-a, and feacal coliform. Multivariate statistical techniques, (FA/PCA), allowed the identification of variables that explain the major percent of total variance. Three components were identified as responsible for the data structure, explaining 88% of the total variance of the data set. Model showed that the first factor (39.81% of variance) assigned as mineralization factor. The second one (29.22% of variance) represented as nutrients group. The third factor (19.16% variance) assigned as a combination of agricultural area runoff and weathering. Varimax rotation showed that the mainly water quality parameters were related to mineralization (natural process) and non-point pollution (anthropogenic activities).

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.

Avaliação hidráulica de um sistema de irrigação localizada de baixa pressão, projetado pelo software "bubbler"

This work was done with the objective of evaluating a low-pressure irrigation system (bubbler system), under field conditions. This evaluation consisted of a study divided in two phases: in the first, the hydraulic design of the irrigation system was elaborated with the use of the software named Bubbler version 1.1; while, in the second phase the installation and the field tests were done. Volumetric tests were accomplished in each emission hose to determine: the flow variation, the coefficients of uniformity, and the application efficiency. It was established the heights of the emitter hose exit at 0.77; 0.71; 0.68 and 0.67 m, on the field, following the recommendation of the software. The tests showed a Christiansens Uniformity Coefficient (CUC) of 96.64%, a Distribution Uniformity (DU) of 95.85% and an Application Efficiency (AE) of 86.98%. The system in the field provided a medium sewage of 64.8 L h-1 against 79.2 L h-1 established by the program. The found values for sewage differed from the values designed by the software, due to variation on pipe diameters and head losses (longitudinal and local), resulting in a standard deviation of 0.23 m.

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.

Produção de sedimentos em microbacias hidrográficas semiáridas sobre manejos diferenciados

The aim of this study was to evaluate and compare the sedimentological behavior in two small rural watersheds in the semiarid Northeast of Brazil, examining the influence of human activity on the sediment yields. The studied area is sited in the Alto Jaguaribe basin, more precisely in the Iguatu County, Ceara State. The experimental area was composed of two small watersheds denominated B1 and B2. In watershed B1 a treatment (thinning) was applied, eliminating the plant species with diameters lower than 10 cm. The results showed that the Caatinga clearing practice did have an influence in changing the sediment yield during the first events. It was also found that the magnitude of previous events contributed to an increase in the sediment yields by the subsequent events as a consequence of the sediment deposit in the drainage network. The accumulated sediment yields reached at the end of the 2009 rainfall season values of 1.45 and 1.39 tons ha -1 year -1 for B1 and B2, respectively, with no significant difference at 5%. It was concluded that, even when the effect of treatment on the sediment yields at the beginning of the rainy season is measured, the total sediment yields was not changed by the adoption of clearing. Therefore, it is a management system that can be employed in the land use at semiarid regions.