Land use impacts on water resources of the Manacás Lake Basin, Minas Gerais, Brazil

The 134.68 ha campus of the Federal University of Juiz de Fora (UFJF) is in urban area impacted by new developments. The population of 27,600 consumers causes the loss of green areas and generates increasing waste and sewage water. This study evaluated the impact of UFJF Campus activities on water quality, emphasizing the Manacás Lake Basin (MLB). The evaluation was based on five monitoring points: a spring (P1) and the four mouths of the streams that flow into Manacás Lake (P2 to P5). Water samples were collected monthly between November 2013 and October 2014, and pH, DO, COD, Conductivity and Turbidity were analyzed. The results showed that the DO increases from the spring (P1) to the mouth (P2), with low values at the other points, and a median of 1.3 mg L-1 at P5. COD does not follow a pattern, registering medians higher than 6 mgO2 L-1 at all points, highlighting P4 with 25.5 mgO2 L-1, the sub-basin which contains most of the Labs. Worse turbidity was found at P5, with 39.42 UNT, coinciding with the sub-basin most affected by construction. Conductivity gradually increased from P1 to P2, and medians were not statically different for P3, P4, and P5. Manacá Lake is Class 2 according to CONAMA resolution Nº 357/2005, but the results showed that the DO at P4 and P5 has values of Class 4 water, with frequent anaerobiosis.O Campus da Universidade Federal de Juiz de Fora, com 134,68 ha, está inserido em área urbana com grande crescimento imobiliário e com uma população de 27.600 usuários, acarretando a perda de áreas verdes, aumentando a geração de resíduos e efluentes. O objetivo desse artigo foi avaliar os impactos das atividades do Campus da UFJF na qualidade da água da Bacia de Contribuição do Lago dos Manacás (BCLM). Foram escolhidos cinco pontos para o monitoramento, considerando uma nascente (P1) e as fozes dos quatro córregos que deságuam no Lago dos Manacás (P2 a P5). As amostras foram coletadas mensalmente, durante o período de novembro de 2013 a outubro de 2014. Foram medidos pH, Oxigênio Dissolvido (OD), Demanda Química de Oxigênio (DQO), Condutividade Específica e Turbidez. Os resultados mostraram que o OD aumenta da nascente de um córrego (P1) para sua foz (P2) com valores baixos nas demais fozes, destacando uma mediana de 1,3 mg L-1 no P5; a DQO não segue um padrão, ficando com as medianas maiores que 6 mg O2 L-1 em todos os pontos, com destaque para o P4 com 25,5 mg O2 L-1, sub-bacia na qual estão localizados a maioria dos laboratórios da universidade; a Turbidez ficou pior no P5 com 39,42 UNT, coincidindo com a sub-bacia mais afetada por obras e movimentação de terra; a Condutividade Específica aumentou gradativamente de P1 até P2, não diferenciando estatisticamente as medianas entre P3, P4 e P5. O Lago dos Manacás enquadra-se na Classe 2 e, de acordo com a Resolução CONAMA nº 357/2005, há uma desconformidade entre os padrões estabelecidos e os resultados encontrados, com destaque para o OD nas seções 4 e 5, com valores atuais compatíveis com a Classe 4 de frequente anaerobiose

Dinâmica de parâmetros limnológicos e uso e cobertura da terra nas bacias hidrográficas das represas Dr. João Penido e São Pedro, Juiz de Fora (MG)

Esta pesquisa teve por objetivo correlacionar os parâmetros limnológicos dos principais tributários das represas Dr. João Penido e São Pedro no município de Juiz de Fora com o uso da terra nas bacias hidrográficas destes mananciais. As amostras foram coletadas mensalmente no período de 2012 até 2013, escolhendo-se seções na nascente, foz e captação, contemplando quatro pontos na bacia da Represa de São Pedro e seis pontos na bacia da Represa Dr. João Penido. Através de uma Sonda Multiparamétrica, foram verificados em campo, os parâmetros: OD, pH, temperatura, condutividade, STD e salinidade. Em cada ponto amostral, foram coletados três litros de água para análise dos parâmetros: DBO5,20, OD, cloreto, turbidez, sólidos totais, pH, fósforo total, nitrogênio total, nitrato, nitrito, amônia e uma amostra de 100ml para análise de coliformes termotolerantes e/ou E-coli. Tais parâmetros foram analisados no LADINAA, Ecologia e outros laboratórios, seguindo as metodologias do Standard Methods for Examination of Water and Waste water (APHA, 2012). As cartas de uso e cobertura da terra foram elaboradas utilizando as Ortofotos Digitais da Prefeitura de Juiz de Fora e adotando a classificada supervisionada MAXVER no software ArcGIS 10.2. Estes dados foram tratados utilizando correlação monótona, relacionando as porcentagens de cada classe de uso da terra até cada seção de monitoramento com os parâmetros citados. Foi utilizado o coeficiente de correlação “” de Spearman com os seguintes resultados: a classe Mata Atlântica aumentou o OD e diminuiu Nitrato, Fósforo e ST; o Eucalipto reduziu o OD e aumentou o Nitrato; a Pastagem Degradada (possivelmente abandonada) reduziu Nitrato e Fósforo; a Pastagem aumentou Coliformes, Fósforo e ST e; finalmente, a Classe Urbanização aumentou Coliformes, Turbidez e Condutividade. Vale ressaltar o fato de as classes de uso da terra não serem independentes: o aumento da porcentagem de “Eucalipto” provoca espacialmente uma diminuição das demais classes. Estes resultados, ainda que parciais, apontam para a necessidade de estudos que orientem o poder público sobre os usos menos impactantes em bacias de mananciais

Represas de abastecimento público de Juiz de Fora: mananciais da vida

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Influence de l’organisation spatiale du paysage sur les transferts hydriques de Carbone, d'Azote et de Phosphore dans un bassin versant agricole de méso-échelle

Nitrogen (N) and phosphorus (P) enrichment of aquatic ecosystems results in their eutrophication and impacts the carbon (C) cycle. In agricultural catchments, most of the hydrologic flux of N and P originates from agricultural areas. The high spatial and temporal variability of C-N-P fluxes in headwaters (<15 km2) complicates the management and protection of water resources, but offers opportunities for optimisation of localised agro-environmental measures. A fortnightly monitoring conducted over 17 months (March 2018-July 2019) of C-N-P concentrations at 32 points, including 23 headwaters, captured this spatio-temporal variability in an agricultural catchment (Yvel River, 375 km2 - Brittany, France). The persistence of spatial patterns of water quality was demonstrated: occasional sampling allowed the ranking of sub-catchments according to their hydric exports of N and P. The link between the landscape spatial organisation and C-N-P fluxes was then investigated across two levels of organisation. Using a stochastic approach, it was shown that the proportion and type of agricultural areas on hillslopes influence N water exports, while the spatial configuration of agricultural areas is critical for P exports. The C-N-P hydrochemical signal from the hillslope is modulated in the river network. A mass balance between modelled hillslope fluxes and the measured mesoscale outlet fluxes showed that these modulations influence the temporal variability of mesoscale concentrations, but have little impact on annual fluxes.L’enrichissement en azote (N) et phosphore (P) des milieux aquatiques provoque leur eutrophisation et impacte le cycle du carbone (C). Dans les bassins versants agricoles, l’essentiel du flux hydrique de N et P provient des surfaces agricoles. La forte variabilité spatio-temporelle des flux de C-N-P à l’échelle de la tête de bassin versant (<15 km²) complique la gestion et la protection de la ressource en eau, mais offre des opportunités d’optimisation pour la localisation de mesures agro-environnementales. Un suivi bimensuel pendant 17 mois (Mars 2018-juillet 2019) des concentrations en C-N-P en 32 points dont 23 têtes de bassin versant a permis de capter cette variabilité spatio-temporelle dans un bassin versant agricole (L’Yvel, 375 km² - Bretagne, France). La persistance des motifs spatiaux de la qualité d’eau a été montrée : un échantillonnage synoptique permet de hiérarchiser les sous bassins versants selon leurs exports hydriques de N et P. Le lien entre l’organisation spatiale et les flux de C-N-P est ensuite fait pour deux niveaux d’organisation. Il est montré, via une approche stochastique, que la proportion et le type des surfaces agricoles dans les versants influence les exports de N, tandis que la configuration spatiale de celles-ci est critique pour ceux de P. Le signal hydrochimique C-N-P issus des versants est modulé dans le réseau hydrographique. Un bilan de masse entre les flux issus des versants et ceux à l’exutoire de méso-échelle a montré que ces modulations influencent la variabilité temporelle des concentrations à la méso-échelle, mais que l’impact sur les flux annuels est faible

The influence of landscape spatial organization on hydric transferts of Carbon, Nitrogen and Phosphorus in a mesoscale agricultural catchment

L’enrichissement en azote (N) et phosphore (P) des milieux aquatiques provoque leur eutrophisation et impacte le cycle du carbone (C). Dans les bassins versants agricoles, l’essentiel du flux hydrique de N et P provient des surfaces agricoles. La forte variabilité spatio-temporelle des flux de C-N-P à l’échelle de la tête de bassin versant (<15 km²) complique la gestion et la protection de la ressource en eau, mais offre des opportunités d’optimisation pour la localisation de mesures agro-environnementales. Un suivi bimensuel pendant 17 mois (Mars 2018-juillet 2019) des concentrations en C-N-P en 32 points dont 23 têtes de bassin versant a permis de capter cette variabilité spatio-temporelle dans un bassin versant agricole (L’Yvel, 375 km² - Bretagne, France). La persistance des motifs spatiaux de la qualité d’eau a été montrée : un échantillonnage synoptique permet de hiérarchiser les sous bassins versants selon leurs exports hydriques de N et P. Le lien entre l’organisation spatiale et les flux de C-N-P est ensuite fait pour deux niveaux d’organisation. Il est montré, via une approche stochastique, que la proportion et le type des surfaces agricoles dans les versants influence les exports de N, tandis que la configuration spatiale de celles-ci est critique pour ceux de P. Le signal hydrochimique C-N-P issus des versants est modulé dans le réseau hydrographique. Un bilan de masse entre les flux issus des versants et ceux à l’exutoire de méso-échelle a montré que ces modulations influencent la variabilité temporelle des concentrations à la méso-échelle, mais que l’impact sur les flux annuels est faible.Nitrogen (N) and phosphorus (P) enrichment of aquatic ecosystems results in their eutrophication and impacts the carbon (C) cycle. In agricultural catchments, most of the hydrologic flux of N and P originates from agricultural areas. The high spatial and temporal variability of C-N-P fluxes in headwaters (<15 km2) complicates the management and protection of water resources, but offers opportunities for optimisation of localised agro-environmental measures. A fortnightly monitoring conducted over 17 months (March 2018-July 2019) of C-N-P concentrations at 32 points, including 23 headwaters, captured this spatio-temporal variability in an agricultural catchment (Yvel River, 375 km2 - Brittany, France). The persistence of spatial patterns of water quality was demonstrated: occasional sampling allowed the ranking of sub-catchments according to their hydric exports of N and P. The link between the landscape spatial organisation and C-N-P fluxes was then investigated across two levels of organisation. Using a stochastic approach, it was shown that the proportion and type of agricultural areas on hillslopes influence N water exports, while the spatial configuration of agricultural areas is critical for P exports. The C-N-P hydrochemical signal from the hillslope is modulated in the river network. A mass balance between modelled hillslope fluxes and the measured mesoscale outlet fluxes showed that these modulations influence the temporal variability of mesoscale concentrations, but have little impact on annual fluxes

Fatores determinantes da qualidade da água na Bacia Hidrográfica do Rio Preto (MG/RJ)

Le bassin hydrographique du la rivière Preto (BHRP) est un bassin stratégique représentant 15% de la surface du bassin hydrographique de la rivière Paraíba do Sul. La BHRP est aussi un territoire où vivent 700.000 habitants, dont plus de 500 000 concentrés dans la zone urbaine de Juiz de Fora. De petites villes et des fragments de forêts au milieu de vastes pâturages composent le paysage. Les sols sont généralement pauvres et sensibles à l'érosion, en plus des pentes raides. La qualité de l'eau est altérée par des sources ponctuelles (industries, décharges, incinérateur) et des sources diffuses plus difficiles à identifier. Cette étude a eu pour objectif de relier la qualité de l'eau dans BHRP à des facteurs physiques (topographie, sols, morphométries et précipitations) et anthropiques (occupation et utilisation du sol et densité de population). Ces facteurs ont été déterminés à travers l’utilisation de la géomatique pour les 17 sous-bassins de la BHRP couvrant ses quatre principaux fleuves : le rio Preto, le rio do Peixe, le rio Paraibuna et le rio Cágado. Ces sous-bassins correspondent aux points de contrôle de la qualité de l’eau de IGAM (Institut de Gestion des Eaux du Minas Gerais). L'évolution spatiale de la qualité de l’eau suivant un axe Paraibuna-Peixe-Preto a été étudiée de la traversée de la zone urbaine de Juiz de Fora et jusqu’aux dilutions en aval par les principales rivières de ce bassin. Cette première étape a permis de déterminer que les paramètres OD et de DBO ont été les plus touchés par la zone urbaine de Juiz de Fora et que les paramètres « fer dissous », « manganèse total », « phosphore total » et « Escherechia Coli » subissent des altérations chroniques dans la globalité de la BHRP, classifiant ainsi ses eaux comme incompatibles avec l'utilisation prévue par la législation. Des contaminations aux métaux (cadmium, plomb et zinc) ont été détectées en amont et en aval de Juiz de Fora, indiquant l’impact ponctuel des industries. Des corrélations non paramétriques ont été calculées entre les caractéristiques naturels et anthropiques des sousbassins (facteurs) et les paramètres de qualité de l’eau. Une grande interdépendance des facteurs physiques et humains a été constatée. L'analyse des corrélations entre les facteurs et les paramètres de la qualité de l'eau a montré occupation et utilisation du sol a été le facteur le plus déterminant de la qualité de l’eau de la BHRP. Des concentrations élevées de manganèse, de plomb et de cyanure libre ont été trouvés dans BHRP sans pouvoir être expliqués par les caractéristiques de leurs sous-bassins. La classe «aire urbaine dense" a empiré presque tous les paramètres et la classe "végétation arborée ou arbustive" classe les a presque tous améliorée. La classe "pâturage" a empiré les paramètres relatifs à la contamination fécale et augmenté les concentrations de macronutriments (azote et phosphore), en particulier pendant la saison des pluies. Ces résultats indiquent que la contamination ponctuelle et particulièrement la contamination diffuse de l'eau doit être étudiée et surveillée de manière plus efficace dans la BHRP, et qu'au minimum, les lois de conservation et de protection des ressources hydriques doivent être appliquées.A Bacia Hidrográfica do rio Preto (BHRP) é uma bacia estratégica por representar 15% em superfície da bacia hidrográfica do rio Paraíba do Sul. A BHRP também é um território onde vivem 700.000 habitantes, sendo mais de 500.000 concentrados na área urbana de Juiz de Fora. As pequenas cidades e as florestas muito fragmentadas se destacam no meio das pastagens que dominam a paisagem. Os solos são em geral pobres e susceptíveis a erosão, além das declividades acentuadas. A qualidade da água é alterada por fontes pontuais (indústrias, lixões, aterros, incineradores) e fontes difusas mais difíceis de identificar. Essa pesquisa teve como objetivo relacionar a qualidade da água na BHRP com fatores físicos (relevo, solos, morfometria e pluviometria) e antrópicos (uso e cobertura da terra e densidade de população). Esses fatores foram quantificados com o emprego do Geoprocessamento para as 17 sub-bacias da BHRP, cobrindo seus quatros rios principais: rio Preto, rio do Peixe, rio Paraibuna e rio Cágado. Essas sub-bacias correspondem aos pontos de monitoramento de qualidade da água do IGAM. A evolução espacial da qualidade da água do Eixo Paraibuna-Peixe-Preto foi avaliada ao atravessar a área urbana de Juiz de Fora e ao ser diluída a jusante pelos rios principais dessa Bacia. Essa primeira etapa permitiu determinar que os parâmetros OD e DBO foram os mais impactados pela área urbana de Juiz de Fora e que os parâmetros Ferro Dissolvido, Manganês Total, Fósforo Total e Escherechia Coli sofriam alterações crónicas na globalidade da BHRP, classificando assim a suas águas como incompatíveis com os usos pretendidos. Contaminações com metais (cádmio, chumbo e zinco) foram detectadas a montante e a jusante de Juiz de Fora, indicando o impacto pontual de indústrias nesses parâmetros. Correlações não paramétricas foram calculadas entre os fatores e as variáveis. Observou-se uma grande interdependência dos fatores físicos e antrópicos. A análise das correlações entre os fatores e as variáveis de qualidade da água apontou que o uso e cobertura da terra foi o fator mais determinante da qualidade da água da BHRP. Concentrações altas de manganês, de chumbo e de cianetos livres foram encontradas na BHRP sem explicação pelas características das suas sub-bacias. A classe “área urbana densa” piorou quase todos os parâmetros e a classe “vegetação arbórea e arbustiva” melhorou em quase todos. A classe “vegetação rasteira” piorou os parâmetros relativos a contaminação fecal e os nutrientes, sobretudo na estação chuvosa. Esses resultados indicam que as contaminações pontuais e difusas da água devem ser investigadas e fiscalizadas com mais efetividade na BHRP, com destaque para a difusa, e que, no mínimo, as leis de preservação e proteção dos recursos hídricos devem ser aplicadas.CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superio

The influence of landscape organized heterogeneity on riverine nitrate dynamics

International audienceLandscape organized (or structured) heterogeneity is often assumed to influence hydrological and biogeochemical patterns across space and time. In this study, we quantified landscape organized heterogeneity with two indices describing the spatial configuration of nitrogen sources or sinks regarding 1) their hydrological distance to the nearest stream (i.e. upslope/downslope heterogeneity: in the lateral dimension) and 2) their hydrological distance to the outlet in the river network (i.e. upstream/downstream heterogeneity: in the longitudinal dimension). The nitrogen sources considered are agricultural fields, defined from interpretation of satellite images, and the sinks are riparian wetland, defined from a topoclimatic index. Using public nitrate concentration and discharge data from 180 catchments in western France (5-150km&amp;#178;), we tested whether landscape organized heterogeneity influenced riverine nitrate concentration and dynamics. The metrics computed to characterize nitrate concentration and dynamics were the flow-weighted concentration (FWNO3), the slope of the log(C)-log(Q) relationship (slope b) and the ratio of the coefficients of variation of concentration and discharge (CVratio). Results showed a high positive correlation between slope b and the CVratio, but no correlation between the later and FWNO3. 43% of the catchment exhibited a positive b slope, indicating maximum nitrate during the winter high flow period and 17% exhibited a negative b slope, indicating maximum nitrate during the summer/fall low flow period; the remaining 40% exhibited a near-zero slope. Landscape organized heterogeneity was larger in the lateral dimension for both nitrogen source and sinks than in the longitudinal dimension. In the lateral dimension, nitrogen sources were primarily located upslope and nitrate sinks downslope. In the longitudinal dimension, no general trend was observed for nitrogen sources and nitrate sinks were rather located upstream. Heterogeneity in the lateral dimension was highly variable among catchments for the smaller catchments and less variable for the larger ones. Heterogeneity in the longitudinal dimension did not exhibit a visible relationship with catchment size. No relationship was found between indices of landscape heterogeneity and FWNO3, arguably because other primary factors (such as the nitrogen surplus or runoff) control most of the regional variability in FWNO3. We found non-linear relationships between our indices of nitrogen sink organization and the b-slope or the CVratio, both in the lateral and longitudinal dimensions. The catchments with a negative b-slope (maximum nitrate during low-flow season) had their wetlands located more upstream and/or more upslope than the average. The relationship with nitrogen sources were opposite by construction (agricultural fields are often located outside wetland areas) but less clear. Further work is ongoing to explore the influence of landscape spatial organization on phosphorus concentration and dynamics

Landscape spatial configuration influences phosphorus but not nitrate concentrations in agricultural headwater catchments

International audienceLandscape organized (or structured) heterogeneity influences hydrological and biogeochemical patterns across space and time. We developed landscape indices that describe the spatial configuration of nutrient sources and sinks as a function of their hydrological distance to the stream (lateral dimension) or to the outlet (longitudinal dimension) and their intersection with flow-accumulation areas. Using monthly nitrate, total phosphorus (TP), soluble reactive phosphorus (SRP) and daily discharge (Q) data from 221 rural catchments (1-300 km²) from 2010-2020, we observed higher variability in flow-weighted mean concentrations in smaller catchments than in larger ones. The variability in landscape configurations also decreased with increasing catchment size. A landscape configuration index, calculated as mean arable land use weighted by spatial data on hydrological distance and flow accumulation, improved prediction of TP and SRP, but not nitrate, compared to the unweighted mean arable land use. We conclude that landscape configuration influences phosphorus transfer more than nitrate transfer, and that flow-accumulation zones and riparian areas are critical source areas for TP and SRP, respectively. By contrast, landscape spatial configuration in the lateral (upslope-downslope) and longitudinal (upstreamdownstream) dimensions did not have an identifiable influence on nutrients temporal dynamics. The indices developed in this study can help design landscapes that minimize diffuse phosphorus losses to streams and show that landscape management is not a first order control for nitrate losses

Conventional soil test phosphorus failed to accurately predict dissolved phosphorus release in agricultural hydromorphic soils in Brittany, Western France

Researches have proved that agricultural phosphorus (P) loss contributes significantly to surface water eutrophication. Various soil test P (STP) methods have been developed to assess the P loss risk from agricultural soils. In the intensively-cultivated Brittany region of Western France, hydromorphic soils in wetland domains exhibit high risks of leaching and transferring dissolved P - the most bio-available form of P - to surface waters. It remains unclear whether STP conventionally developed for well-drained soils can accurately predict the risk of dissolved P release from these hydromorphic soils. In this study, we measured the dissolved reactive P (DRP) concentrations in soil solutions sampled in situ from 26 hydromorphic soils in the Brittany region and examined their relationship with several STPs available on the corresponding soils, such as the degree of soil P saturation, the equilibrium soil P concentration, or the soil Olsen P, Dyer P, and water extractable P contents. DRP concentrations ranged from 0.01 to 0.310 mg P l−1 (mean = 0.075 mg P l−1), highlighting the potential of hydromorphic soils as hotspots for DRP release in agricultural landscapes. Correlations between DRP concentrations and STPs were relatively weak (0.09 < r2 < 0.64), indicating that conventional STPs are generally unable to accurately predict the DRP release risks in hydromorphic soils. Tentatively, Olsen P showed promises as a useful risk indicator, with a relatively high r2 value of 0.6 and wide inclusion in the current STP database, especially in the Brittany region. Nevertheless, this hypothesis requires further evaluation with additional data. This study confirms the high risk of dissolved P release from hydromorphic soils in agricultural wetland domains and emphasizes the need for developing specific risk assessment tools to these hydromorphic soils

Correlations chart: Tool to analyse the dynamics of water quality parameters

ABSTRACT The search for statistical techniques and forms of graphical representation that can explain the most relevant correlations among limnological variables can help interpret phenomena in a body of water. The objective of the article was to propose a graphical representation of the correlations among limnological variables applied in the contributing basin of the Dr. João Penido reservoir, in Juiz de Fora, Minas Gerais state, Brazil. Six sections were monitored monthly from May 2012 to April 2014, analysing 15 water quality parameters and their statistical correlations. The correlations were represented graphically with the program Gephi 0.8.2-beta. The influence of organic matter (of natural and anthropogenic origin resulting from pasture runoff and sewage) on water quality was verified, with an observed increase in water quality parameters especially nitrogen and phosphorous, oxygen consumed, chemical oxygen demand, turbidity and total suspended solids. It is concluded that the correlation chart assists in the understanding of the dynamics of the water quality parameters at the different sites analysed