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Freshwater blue spaces (FBS), such as ponds, are key elements of the urban landscape and are under strong anthropogenic pressure. Land-use types and diversity may exert a negative or positive impact on FBS' water quality depending on their nature and arrangement. The information available in this respect is remarkably scarcer for water bodies in the Global South than for the north. Thus, we aim to identify and quantify the land-use types in a 500-m buffer zone of urban ponds in the Pampean region (Argentina) to assess their impact on water quality. We based our study on 15 FBS located in neighborhoods of Buenos Aires province during cold and warm seasons. We analyzed physical, chemical, and biological variables, and estimated water conditions by means of water quality indexes (WQIs) and quality guidelines. We quantified the dominant land-use type and the diversity of uses in the ponds' buffer zones, and evaluated their relationships with WQIs. Our results showed that WQIs were negatively related to a high proportion of residential areas in the adjacent zone, while positively to recreational ones. The diversity of land uses did not influence the water quality. We propose a new WQIpond with fewer key response variables, and as sensitive as the currently used WQIobjetive. We conclude that water quality from urban ponds in the Pampean region can be affected by dominant land-use type in the adjacent area but also the quality of their water supply sources (superficial and/or underground), clandestine wastewater discharges, and non-point pollution.

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Impact of natural phenomena and anthropogenic activities on water quality is closely related with temperature increase and global warming. In this study, the effects of climate change scenarios on water quality forecasts were assessed through correlations, prediction algorithms, and water quality index (WQI) for tropical reservoirs. The expected trends for different water quality parameters were estimated for the 2030-2100 period in association with temperature trends to estimate water quality using historical data from a dam in Mexico. The WQI scenarios were obtained using algorithms supported by global models of representative concentration pathways (RCPs) adopted by the Intergovernmental Panel on Climate Change (IPCC). The RPCs were used to estimate water and air temperature values and extrapolate future WQI values for the water reservoir. The proposed algorithms were validated using historical information collected from 2012 to 2019 and four temperature variation intervals from 3.2 to 5.4 °C (worst forecast) to 0.9-2.3 °C (best forecast) were used for each trajectory using 0.1 °C increases to obtain the trend for each WQI parameter. Variations in the concentration (±30, ±70, and +100) of parameters related to anthropogenic activity (e.g., total suspended solids, fecal coliforms, and chemical oxygen demand) were simulated to obtain water quality scenarios for future health diagnosis of the reservoir. The results projected in the RCP models showed increasing WQI variation for lower temperature values (best forecast WQI = 74; worst forecast WQI = 71). This study offers a novel approach that integrates multiparametric statistical and WQI to help decision making on sustainable water resources management for tropical reservoirs impacted by climate change.

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Water quality indices (WQIs) are numerical measures used by researchers and water managers to communicate water quality status to the public. This study analyzes the official databases from the CONAGUA monitoring network of the main tributary rivers in the middle basin of the San Pedro-Mezquital River in Durango, Mexico, for a 6-year period (2013-2018). We applied three WQIs to 432 data (18 sampling sites, four samples per year, 6 years): Canadian Council of Ministers of the Environment (CCME) WQI, National Sanitation Foundation (NSF) WQI, and Secretariat of Urban Development and Ecology (SEDUE) WQI. The Canadian index proved to be a flexible, appropriate, and rigorous methodology for assessing water quality based on its use. Results classify the water quality in the studied reservoirs as good, while river water was rated for public use, as marginal to very poor. No statistical significant differences in the quality of water between the rainy (June-October) and dry (November-May) seasons were found. However, tendency shows that in the rainy season the water quality was lower, mainly attributed to agricultural runoffs and bank erosion. The main contamination problem was the presence of fecal coliforms in high concentrations, which is associated to the high population density in the area, low sanitation efficiency, and multiple non-point discharges.

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Anthropic activities performed in a river basin, especially those that promote changes in the soil surface, have great effect on the quality of the waters in the basin. Thus, the objective of this study was to evaluate water quality by applying the Water Quality Index (WQI) in springs and watercourses located in an area with different land use and occupation characteristics, as well as to compare the analyzed variables with the standards established for class 2 of the National Environmental Council (CONAMA, for its acronym in Portuguese) Resolution No. 357/2005. Seven sampling points located in the rural area of the municipality of Jacutinga, Minas Gerais State (MG), were monitored. The water samples were collected from October 2018 to July 2019. Comparison with the resolution showed that the quality condition was lower than the standard established for class 2 in most campaigns conducted. Regarding the mean WQI, the water quality at points S1, WC1, WC2, and WC3 was classified as "average," while the water quality at points S2, S3, and S4 was classified as "good." There was seasonal variation in the WQI only at point WC1. Overall, thermotolerant coliforms (TC), nitrate, and phosphorus are the main factors deteriorating water quality, and it may be directly related to the agricultural activities practiced in the monitored areas.

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Managing water resources in regions with scarce data, like most developing countries, is still one of the major challenges around the world. Analysis of water quality parameters can provide important information for understanding the current status of water resources and their surroundings, including the changes that have occurred over time. This study aims to evaluate the influence of preservation areas on surface water quality in the Atlantic Forest biome. For this purpose, water quality monitoring sites with a greater number of parameters and longer monitoring time, located in six basins in the Atlantic Forest region of Brazil near preservation areas, were selected. This study employs seven statistical methods, such as cluster and principal component analysis (PCA), and promotes a robust analysis of the pollution of water resources in the Atlantic Forest. The most preserved basins, with more than 87% preservation area, have lower levels of pollution. The second most degraded basin, with 56% preservation area, presents intermediate pollution levels. The most degraded basin has the highest level of pollution. The basin with the lowest area of native vegetation is considered a degraded basin. Finally, non-point sources of pollution from agricultural activities were identified as the main sources of pollution in the region. The cophenetic correlation of 0.97 indicates a good performance of the cluster analysis. In addition, the pre-tests of PCA showed the suitability of the data for performing the test (Bartlett test, < 2.2e-16 and KMO, P= 0.7). The first principal component in the PCA, which accounts for 31.4% of the total variation, is associated with strong ammonia nitrogen and total Kjeldahl nitrogen loads, and moderate biological oxygen demand and nitrite loads. The second component, representing 13.6% of the total variation, indicates periods of self-cleaning of water resources after contamination. The results indicate the importance of maintaining preservation areas in the watershed contribution areas for the improvement of surface water quality in the Atlantic Forest.

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Pollution incidents cause transient water quality alterations during the passage of contaminants' plume along watercourses, with plume passage period and contaminants' concentrations modelled by advection-dispersion equations. Despite being transient, water quality alterations can impose many impacts on the streamwater ecosystem services. This study proposes two frameworks based on Habitat Equivalency Analysis to be applied during assessments of streamwaters' pollution incidents and respective compensation panoramas: (1) Streamwater interim loss framework, to calculate interim loss debits caused by transient alterations in the streamwater quality; (2) Total credit framework, to calculate streamwater credits generated by improvements in selected watercourse's streamwater quality, produced by wastewater treatment plants in this study. The amount of credits calculated in the selected watercourses assists in the proposal of suitable compensatory remediation projects to offset interim losses. Frameworks' calculations are founded on IVA, a water quality index for protection of aquatic life and aquatic communities. Frameworks' calculations depend on three parameters: IVA, watercourses fluxes and the present value multiplier. The frameworks were calculated in ΔIVAxL, unit defined by multiplying sensed alterations in streamwater quality (as ΔIVA) and streamwater flux, in liters (L). The frameworks were applied to two major streamwater pollution incidents in Brazil, caused by the dam collapses of Mariana and Brumadinho, suggesting suitable compensatory remediations' projects for the respective streamwater interim losses. Depending on the selected project, Brumadinho compensation period varied from 2 to 5 years, with estimated costs in the 2020 Int.$ 5.7-18.7M range; Mariana compensation period varied from 8 to 20 years, with estimated costs in the 2020 Int.$ 16.7-58.1M range. Based on Brumadinho compensatory remediation projects, an average water pollution environmental damage value per interim loss was calculated, 1.17E-4 2020 Int.$/ΔIVAxL, which might be useful in comparing streamwater pollution evaluations around the world.

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This paper presents a new aggregation method to calculate the WQI-CCME, named stepwise aggregation method, to communicate the water quality of the São Francisco River, Brazil, a river of national expression, with more than 2700 km long. Differently from the original proposal for the WQI-CCME, the new aggregation method uses data from a single monitoring campaign, to avoid the loss of data, as many variables are not systematically measured in all monitoring campaigns. The stepwise aggregation method also requires to combine data from a minimum of four monitoring locations per section of the river, to attend the statistical requirement, a proposal already presented in the literature. After using the first four points, the next calculation requires to abandon the first point (upstream) and to include the next point (downstream), and the sequential calculation will generate the results to build the river water quality profile. In the present work, with 31 monitoring points, the stepwise aggregation method allowed to calculate the WQI-CCME for 25 sections. The stepwise method has the advantage of multiplying the number of index calculations, allowing to construct a more uniform water quality profile for a long river. The choice of using the WQI-CCME in this work, is because this index has many successful applications all over the world, favored by its flexibility of parameter selection, ease of calculation, adaptability to legal requirements of different locations and different water uses. The WQI-CCME profiles were compared with those for the WQI-CETESB, an index derived from the WQI-NSF and extensively used by the Brazilian Monitoring Programs. The comparison demonstrated similarity, only if the same number of parameters were used, but WQI-CETESB gives better water quality, similarly reported for the WQI-NSF, which systematically classify the water quality in the superior range. In this paper, the calculation of the WQI-CCME, with 38 and 20 parameters, confirmed the dependence of the WQI-CCME factors (F1, F2) on the number of variables considered. The calculation with more variables (38) gave better results for the water quality than the calculation with less variable (20). Thus, while the application of the WQI-CCME has a variety of advantages, it requires careful evaluation about the variables to use, and the objectives for the index calculation, as considered by many authors.

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A monitoring study was carried out in two micro-catchments in the Reventazón basin, in Northern Cartago, Costa Rica; pesticide occurrence and water quality were analyzed. Twelve pesticides were detected, five insecticides (chlorpyrifos, carbofuran, cypermethrin, imidacloprid, and oxamyl), four fungicides (carbendazim, imazalil, metalaxyl, and thiabendazole), and three herbicides (diuron, linuron, and terbutryn); eight of them presented risk quotients RQ >1, which implies a high risk for the environment. The water quality evaluation included fourteen physicochemical and microbiological parameters, out of which thermotolerant coliforms, nitrate, and total phosphorus exceeded a selected threshold value in every sample. Five metals were also included in the evaluation, Pb was the most frequent, followed by few detections of Cd, Cu, and Cr. Four water quality indexes (WQIs) were applied, two of them, the CCME WQI, based on physicochemical parameters, and the BMWP-CR WQI, based on benthic macroinvertebrate recount adapted to Costa Rican species, categorized all the sampling points as "bad" and "very bad" quality. This work of monitoring is important in the Latin American region, where there is a lack of information for regulation improvement and management decisions. These results showed poor management of the micro-catchments in this agricultural rural area.

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RESUMO A urbanização conduz ao acréscimo de superfícies de baixa permeabilidade nas bacias hidrográficas, o que resulta em aumento no volume de água pluvial escoado superficialmente nos terrenos e, consequentemente, na ampliação de poluentes carreados aos cursos de água receptores, o que pode prejudicar a qualidade de suas águas. O objetivo principal da presente pesquisa foi analisar a variação da qualidade da água ao longo do dia em um córrego impactado por área urbana por meio do índice de qualidade das águas (IQACETESB) e dos parâmetros envolvidos no seu cálculo. A coleta de amostras foi realizada uma vez ao mês, durante o período de sete meses, nos seguintes horários: 8h, 14h e 19h. No geral, foram encontradas baixas concentrações de oxigênio dissolvido e altos teores de matéria orgânica e nutrientes no córrego avaliado. A amostragem em diferentes períodos do dia foi eficiente em relação ao entendimento dos processos antrópicos que acontecem na sub-bacia estudada (e.g., lançamento de esgoto doméstico in natura e aporte intenso de fósforo no período da manhã). Além disso, foi observada uma oscilação significativa no valor do IQACETESB entre os três períodos do dia, tal como em junho de 2018: 52 (manhã) e 23 (noite). Dessa forma, a avaliação do IQACETESB conduzida em apenas um horário do dia pode deixar passar informações essenciais para os gestores ambientais, resultando em uma visão errônea do problema.

ABSTRACT Urbanization leads to the addition of areas of low permeability in watersheds, which results in an increase in the volume of rainwater drained superficially and, consequently, in the expansion of pollutants carried to the receiving watercourses, which may impair the quality of their waters. The main objective of this research was to analyze the variation in water quality throughout the day in a stream impacted by urban areas through the water quality index (WQICETESB) and the parameters involved in its calculation. Sample collection was performed once a month, for a period of seven months, at the following times: 8:00 am, 2:00 pm, and 7:00 pm. In general, low concentrations of dissolved oxygen and high levels of organic matter and nutrients were found in the stream evaluated. Sampling at different times of the day was efficient in terms of understanding the anthropic processes that take place in the studied sub-basin (e.g., the release of fresh domestic sewage and intense phosphorus input in the morning). In addition, a significant fluctuation in the value of the WQICETESB was observed between the three periods of the day, as in June 2018: 52 (morning) and 23 (night). Thus, the evaluation of the WQICETESB conducted in only one hour of the day can pass on essential information for environmental managers, resulting in an erroneous view of the problem.

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RESUMEN La microcuenca de la quebrada Jui, enmarcada dentro de la cuenca alta del río Sinú, región Caribe de Colombia, es uno de los recursos hídricos utilizados por la población rural para consumo, riego y saneamiento; sin embargo, recibe cargas contaminadas de centros poblados en su área de influencia, que corresponden al vertimiento de aguas residuales, afluentes de laguna de oxidación, actividades ganaderas, extracción de arena, agricultura de pancoger y cultivos no formales. El objetivo de este estudio fue determinar el índice de calidad del agua (ICA) y establecer la relación entre los parámetros fisicoquímicos y microbiológicos con las diferentes fuentes antropogénicas, para establecer origen común de contaminación. Además, el análisis de plaguicidas organoclorados y organofosforados, para conocer la influencia de las actividades agrícolas. Se tomaron muestras en seis estaciones, en el periodo seco y húmedo del 2018. Las concentraciones de los parámetros fisicoquímicos y microbiológicos, se analizaron empleando los métodos estandarizados de la American Public Health Association. Los plaguicidas, se cuantificaron por el método cromatografía de gases con espectrometría de masas (GC-MS). En promedio, el ICA fue 74,1, clasificando la fuente hídrica con buena calidad, exceptuando las estaciones (E4 y E5), en el periodo húmedo, cuya clasificación fue media, debido al aporte de coliformes fecales y turbidez. La concentración de plaguicidas, se presentó por debajo del límite de detección del método. En general, el análisis estadístico multivariado indica que las fuentes de contaminación derivan de aguas residuales domésticas, escorrentía agrícola, excretas del ganado porcino y minería de arena.

ABSTRACT The micro-base of the Jui creek, framed within the upper Sinú River basin, Colombia Caribbean region, is one of the water resources used by the rural population for consumption, irrigation and sanitation. However, it receives contaminated loads from urban centers in its area of influence that correspond to the discharge wastewater, oxidation lagoon tributaries, livestock activities, sand extraction, agriculture and non-formal crops. The objective of this study was to determine the water quality index (ICA) and establish the relationship between the physical-chemical and microbiological parameters with the different anthropogenic sources to establish a common source of contamination. In addition, the analysis of organochlorinated and organophosphate pesticides to understand the influence of agricultural activities. Samples were taken in six seasons, in the dry and humid period of 2018. Concentrations of physical-chemical and microbiological parameters were analyzed using the American Public Health Association's standardized methods. The pesticides were quantified by the gas chromatography method with mass spectrometry (GC-MS). On average the WQI was 74.1 classifying the water source with good quality, except the seasons (E4 and E5) in the wet period, the classification of which was average, due to the contribution of fecal coliforms and turbidity. The concentration of pesticides was below the detection limit of the method. In general, multivariate statistical analysis indicates that sources of pollution are from domestic wastewater, agricultural runoff, pig excretions and sand mining.

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A monitoring study was carried out in three agriculturally influenced microcatchments in Costa Rica during 2012-2014, for pesticides and water quality parameters. A total of 42 pesticides were analyzed, detecting the following in water samples: two herbicides (oxyfluorfen, diuron), four insecticides (carbofuran, chlorpyrifos, oxamyl, ethion), and two fungicides (thiabendazole, carbendazim); while in sediment samples only the insecticides, chlorpyrifos and cypermethrin were found. Water quality was also assessed by the Canadian Council of Ministers of the Environment Water Quality Index and the National Sanitation Water Quality Index, the first one classified most of the sampling point as marginal and poor quality while the second one classified most of them as good quality, the most affected parameters were nitrate, phosphorous, suspended solids and organic matter content. The results suggest that the water quality in the microcatchments seems to be affected by the nearby agricultural and urban activities in the region.

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Poor water quality in urban streams places at risk the health of urban residents and the integrity of urban environments, ultimately leading to the "urban stream syndrome." In response to growing concerns regarding urban streams in Uruguay, we evaluated the spatiotemporal variation in water quality parameters in two urban streams, the Ceibal and La Curtiembre streams, over 12-18 months. A proposal for an Urban Water Quality Index (UWQI) was developed based on national water quality standards for two stream classes to assess variability in overall stream condition over time. Both streams displayed extremely high levels of fecal coliform concentrations in mid-downstream sites and relatively high levels of total dissolved phosphorus and ammonia well above the national standards of 0.025 mg/L and 0.02 mg/L, respectively. Nitrate was consistently below the national maximum of 44.3 mg/L, calling to question the adequacy of this standard for designated uses. Over 40% of samples had oxygen levels below the national standard of 5 mg/L, and a dead zone (average 1.5 mg/L) was detected in the downstream reach of the La Curtiembre stream. Despite differences in land use and urban context, monthly observations of nutrients and coliforms indicated high levels of contamination in mid-downstream reaches, which could present a health risk for the populations in Paysandú and Salto. This study highlights the degradation of urban streams in two major cities in Uruguay and the need for a comparative diagnosis of stream condition as a basis for decision-making regarding urban development and water resources.

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Minas Gerais is one of the 27 federative units of Brazil; it is the fourth state with the largest territorial area and the second in number of inhabitants. Since 1997, the monitoring of the surface water quality of the State of Minas Gerais has been carried out. In this study, generalized regression models were constructed to determine the correlation between the Water Quality Index (WQI) and the sanitary and socioeconomic variables: Municipal Population, Human Development Index (HDI), Gini Index, Percentage of Vulnerables to Poverty (Poverty), Monthly Per Capita Income, Percentage of Inadequate or Poor Sanitation. In addition to the sanitary and socioeconomic variables listed, it also used year of water quality monitoring, altitude of the monitoring point, and distance from the monitoring point to the urban center of the municipality. The results from the generalized models showed that the variables year, altitude, Gini Index, monthly per capita income, and poor sanitation variables were positively associated with WQI. In other words, high values of each variable increased WQI, while population variables HDI and poverty were negatively related to WQI, that is, a high population value, HDI, or poverty implies a low WQI value. Socioeconomic variables such as HDI, Gini Index, poorness, or poor sanitation percentage present the coefficients with the largest modulus. Thus, among the socioeconomic variables studied, these are the ones that most contribute to the variability of WQI. The year and altitude variables have positive regression coefficients, indicating that when these variables increase, WQI also increases. The positive correlation with the year shows that the surface water quality of Minas Gerais improved during the monitoring years.

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A Water Quality Index (WQI) is a formulation that enables the estimation of the overall quality of a water body based on significant parameters. One example of this is the well-known and widely accepted NSF-WQI, which is frequently used to assess chemical, physical, and microbiologic features of waterbodies in temperate latitudes. In this work, a well-structured method, completely based on multivariate statistical methods and historical data distributions, was used to develop an ecosystem specific water quality index (ES-WQI). Lake Cajititlán, a subtropical Mexican lake located in Tlajomulco de Zúñiga, was selected as a case of study because it is an endorheic shallow lake that shows signs of high levels of eutrophication due to anthropogenic contamination. As a result of the contamination, and its sensibility to changes in the water level, it undergoes important changes in its water features, such as turbidity and intense green color, and experiences massive events of fish mortality. The proposed ES-WQI describes the changes in water quality over the year well and correlates with the capability of the lake to support aquatic life, as the lowest estimated values coincide with the biggest events of massive fish mortality in the lake. Furthermore, the ES-WQI clearly differentiates between typical cyclic behaviors and actual deteriorating trends and is capable of tracking incremental changes all over the range of the possible concentration values of the water quality parameters.

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Canadian Water Quality Index (CWQI) provides protection for freshwater life promoting healthy ecosystems and safeguarding human health. Biological Diatom Index (BDI) was developed to indicate the ecological status and water quality of freshwater systems. This paper evaluates the relations between the two different indices. During rising and falling, water samples were taken in the Curuai Floodplain, Brazil. CWQI was calculated using 14 physicochemical parameters and 1 microbiological parameter. The limits were established according to freshwater quality conditions and standards based on water use classes 1 and 2 determined in CONAMA 357 legislation and British Columbia. Canadian Water Quality Index categorization ranged from "marginal" to "excellent," most sampling units were "good" (71%), followed by "fair" (12%) and "excellent" (12%) water quality. Total phosphorus (38 times), chlorophyll a (20), dissolved oxygen (10), and total organic carbon (10) were the parameters that presented the most non-compliance values. Encyonema silesiacum (14%), Gomphonema parvulum (13%), and Navicula cryptotenella (12%) were the main taxa in the rising period, while G. lagenula, E. silesiacum, and Fragilaria capucina were the main taxa during the falling period. BDI ranges from I to V water quality classes. We observed "poor" to "very good" ecological status, with most sampling units "moderate" (52%) and "good" (29%). Water quality for class 2 was better than water quality for class 1, as the limits of the parameters evaluated were more restrictive in class 1 than in class 2 and the predominant uses of water require a higher degree of water purity. The biological index based on diatoms was the most restrictive index whose water classes and categorizations have shown an ecological status that could threaten the protection of aquatic communities on the Curuai floodplain. We suggest the combined use of both indices-physicochemical and biological for water quality assessment in this type of environment.

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RESUMO A divulgação de informações sobre qualidade das águas para um público não especialista é fundamental para subsidiar ações políticas e institucionais de gestão dos ambientes aquáticos. Para tanto, índices de qualidade de água têm sido propostos por serem capazes de sintetizar em um único valor ou categoria a informação, normalmente descrita a partir de um conjunto extenso de variáveis de qualidade de água. Este trabalho propõe um novo índice de qualidade de água, IQAFAL, baseado em lógica nebulosa, direcionado para o ambiente lótico, desenvolvido com a colaboração do quadro de especialistas da área de qualidade de água do Instituto Estadual do Ambiente (INEA). O índice proposto foi aplicado a dados de qualidade de água do Rio Paraíba do Sul, obtidos pelo INEA, nos anos de 2002 a 2009. Os resultados do IQAFAL mostraram que esse índice foi capaz de descrever a qualidade da água desse trecho do Rio Paraíba do Sul, correspondendo satisfatoriamente às avaliações de qualidade de água contidas nos relatórios disponíveis. Verificou-se também que com essa metodologia foi possível evitar que a influência de uma variável em condições críticas fosse atenuada pela influência das outras variáveis em condições favoráveis, produzindo um resultado impreciso no índice final.

ABSTRACT The dissemination of information on water quality for a non-specialist audience is essential to support political and institutional actions for the management of aquatic environments. Therefore, water quality indices have been proposed since they are able to synthesize into a single value or category information, usually described from an extensive set of water quality variables. This research proposes a new water quality index, based on fuzzy logic, aimed at lotic environments, developed through the collaboration of experts in water quality of the Rio de Janeiro Environmental Agency (Instituto Estadual do Ambiente - INEA). The proposed index was applied to water quality data from the Paraíba do Sul River, obtained by INEA, in the years 2002 to 2009. The results of IQAFAL showed that the index was able to synthesize the water quality of this stretch of the Paraíba do Sul, satisfactorily matching the assessments of the water quality assessments contained in the reports available. It was also noticed that with this methodology it was possible to avoid the attenuation of the influence of a variable in critical condition was attenuated by the influence of other variables in favorable conditions, producing an inaccurate result in the final index.

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The externalities generated by disorderly urbanization and lack of proper planning becomes one of the main factors that must be considered in water resource management. To address the multiple uses of water and avoid conflicts among users, decision-making must integrate these factors into quality and quantity aspects. The water quality index (WQI), using the correlation matrix and the multivariate principal component analysis (PCA) and cluster analysis (CA) techniques were used to analyze the surface water quality, considering urban, rural, and industrial regions in an integrated way, even with data gaps. The results showed that the main parameters that impacted the water quality index were dissolved oxygen, elevation, and total phosphorus. The results of PCA analysis showed 86.25% of the variance in the data set, using physicochemical and topographic parameters. In the cluster analysis, the dissolved oxygen, elevation, total coliforms, E. coli, total phosphorus, total nitrogen, and temperature parameters showed a significant correlation between the data's dimensions. In the industrial region, the characteristic parameter was the organic load, in the rural region were nutrients (phosphorus and nitrogen), and in the urban region was E. coli (an indicator of the pathogenic organisms' presence). In the classification of the samples, there was a predominance of "Good" quality, however, samples classified as "Acceptable" and "Bad" occurred during the winter and spring months (dry season) in the rural and industrial regions. Water pollution is linked to inadequate land use and occupation and population density in certain regions without access to sanitation services.

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The environmental protection area of Lageado was created in 2001 in Campo Grande, Mato Grosso do Sul's State capital, and it constitutes a conservation unit that belongs to the Sustainable Use Group. The environmental protection area of Lageado is located in an urban area and provides approximately 12% of the water supplied to the municipality. Knowing the relationship between soil occupancy and population density, which may cause harmful effects to the quality of surface water and water resources, is fundamental. The present study aims to analyse the physical-chemical parameters of water samples collected at three different times and in six distinct points in Lageado. To verify whether the transformation of this watershed into a conservation unit resulted in the maintenance of water quality, the statistical analyses considered the significance and correlation among the following parameters: water quality index (WQI); dissolved aluminium, iron and copper; Escherichia coli; nitrate; ammoniacal nitrogen; Kjeldahl nitrogen; chemical oxygen demand; and chlorophyll α. The results show that the formal creation of the environmental protection area of Lageado did not provide the effective improvement or maintenance of its environmental conditions. Statistically, there were decreases in the WQI over the studied period, which demonstrates that the creation of a conservation unit is, in itself, not sufficient and it lacks the implementation of effective programmes and actions related to the soil use, occupancy and water quality.

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Agricultural systems have experienced rapid expansion and intensification in the last several decades. In Uruguay, since the beginning of 2000, the most common cropping systems have included soybeans. Currently, this crop is expanding towards lowlands traditionally occupied by rice in rotation with pastures. However, the environmental effects of agricultural intensification and diversification are not well known. Thus, some indices have been proposed to quantify the changes in agricultural production systems and assess water quality. The main goal of this study was to develop a water quality index (WQI) to assess the impacts of the diversification of rice production systems in northwest Uruguay. The study was carried out in an agricultural basin where other summer crops have been incorporated in the rice-pasture sequence. Agriculture intensification and crop diversification indices were calculated using information provided by farmers. Water samples were collected downstream of the production area before crop sowing and after crop harvest (2008-2009 to 2010-2011 and 2016-2017 to 2017-2018). Biochemical oxygen demand, nitrates, total phosphorus, fecal coliforms, and total suspended solids were the variables that mainly explained the effects of the agricultural activities on water quality. The proposed water quality index included these unweighted variables, which allowed for the pre-sowing and post-harvest to be differentiated, as well as the degree of diversification. Therefore, the proposed WQI constitutes a tool that can be used to evaluate the water quality in an agricultural basin. Likewise, it can be used to select agricultural sequences that generate the least possible impacts on the associated water resources.

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RESUMO O objetivo deste estudo foi desenvolver um índice de qualidade de água modificado (IQAMod), por meio de análises multivariadas, e comparar com o índice utilizado pela Companhia Ambiental do Estado de São Paulo (Cetesb) (IQACETESB), para ser aplicado no Arroio Pelotas, Rio Grande do Sul, Brasil. Foram usados dados secundários de qualidade da água superficial do Arroio Pelotas, para o sítio de amostragem GER 48, localizado no município de Pelotas, monitorados e disponibilizados pela Fundação Estadual de Proteção Ambiental Henrique Luís Roessler (FEPAM), no período entre 1997 e 2013. Entre as análises multivariadas, empregou-se a análise fatorial (AF)/análise de componentes principais (ACP). Os resultados indicaram que a ACP extraiu duas componentes principais que explicaram 100% da variância total dos dados na matriz de correlação, enquanto os escores fatoriais para o cálculo do IQAMod foram extraídos do primeiro fator, que explicou 70,6% da variância total. Concluímos que o IQAMod mostrou demanda bioquímica de oxigênio (DBO5), turbidez (TH) e sólidos totais (ST) como as variáveis de mais importância na construção do índice, diferindo do IQACETESB, que apresentou as variáveis oxigênio dissolvido (OD), coliformes termotolerantes (CT) e potencial hidrogeniônico (pH) como as de mais relevância, demonstrando assim a necessidade da calibração do IQACETESB para aplicação nesse ecossistema específico.

ABSTRACT This research aimed at developing a modified water quality index (WQIMod) by using multivariate analysis, from a comparison with the WQI used by the Environmental Company of São Paulo (Companhia Ambiental do Estado de São Paulo-Cetesb) (IQACETESB), to be applied in the Pelotas Stream, RS, Brazil. Secondary data from Pelotas Stream surface water quality were used, collected in the sampling site GER 48, located in the municipality of Pelotas, where they were monitored and provided by the State Foundation of Environmental Protection Henrique Luís Roessler (Fundação Estadual de Proteção Ambiental Henrique Luís Roessler-FEPAM) between 1997 and 2013. Among the multivariate analyses, the factor analysis/principal component analysis (PCA) was used. The results indicated that the PCA extracted two principal components, which explained 100% of the total data variance in the correlation matrix, while the factorial scores for WQIMod calculation were extracted from the first factor, which explained 70.6% of the total data variance. We concluded that the WQIMod exhibits biochemical oxygen demand (BOD5), turbidity (TH) and total solids (TS) as the most important variables for the index construction, differing from the WQICETESB, which shows the variables dissolved oxygen (DO), thermotolerant coliforms (TC) and hydrogenionic potential (pH) as the most relevant ones, indicating the need of WQICETESB calibration for applying in this specific ecosystem.