Subsurface leaching is a major pathway of phosphorus (P) loss from agricultural landscapes and soil P indices (SPIs) have been developed to assess P leaching risk. However, most SPIs are developed for well-drained agricultural soils, their ability to predict P leaching risk in hydromorphic soils remains underexplored. Using soil water P concentration data from a 3-year field monitoring (weekly or biweekly) and the SPIs from the same hydromorphic soils in an agricultural catchment in Western France, we tested the ability (Pearson r2) of SPIs to predict soil water P concentrations and assessed the influence of hydrological conditions on these relationships. Eight SPIs were tested including Dyer P, Olsen P, total P, water-extractable P (WEP), equilibrium soil P concentration (ECPo), and three degree of P saturation indices (DPS_Dyer, DPS_Olsen, and DPS_Pöthig). Results showed high temporal variations in the positive correlations between the SPIs and molybdate-reactive P (MRP) and total dissolved P (TDP), with mean r2 ranging 0.36-0.64 for MRP and 0.34-0.58 for TDP. The prediction effectiveness of most SPIs showed no significant difference among hydrological years, while those of Olsen P, ECPo, DPS_Olsen, DPS_Pöthig, and TP were significantly lower in winter waterlogging seasons compared to rewetting/drying seasons. This suggests a greater influence of intra-annual hydrological conditions on SPIs' prediction effectiveness, particularly for MRP. This study highlights the need to consider the resilience of SPIs to hydrological variations and proposes that aggressive indicators like Dyer P and DPS_Dyer should be prioritized when developing P leaching risk indicators for hydromorphic agricultural soils.

Most downstream compartments of the continental hydrological network, estuaries are the last biogeochemical filter of the Land-Ocean Aquatic Continuum before the oceanic realm. As such, they receive substantial amounts of carbon and nutrients from rivers and their intense biogeochemical processing allows the removal of part of those inputs, hence potentially contributing to the prevention of coastal eutrophication. Indeed, eutrophication resulting from enhanced nutrients loads from rivers is a pressing global issue, affecting numerous coastal areas and regional seas worldwide. However, simulating ecosystems as intricate as estuaries, characterized by numerous biogeochemical gradients, an intense benthic-pelagic coupling and controlled by complex hydrodynamics is a challenge often associated with intensive computation and data requirements. As a result, the development of numerical models suitable to quantify the filtering function of estuaries is often limited to scarce well studied systems. This highlights the still unresolved challenge of designing and applying a generic modeling strategy able to capture the complexity and intensity of biogeochemical processes for a diversity of often data-limited estuaries along a continuous coastal stretch.In this study, we present the first spatially explicit, regional, fully transient simulation of the estuarine biogeochemical filter over a multi annual period. This application to 40 estuaries of the Atlantic coast of France from its southern border with Spain to Belgium was performed in the context of the nuts-STeauRY project which aims at illustrating the interest of integrated land-sea modelling approaches to better design spatialized scenarios of agriculture and land-use practice to limit coastal eutrophication in France. The simulations were performed using the proven generic estuarine model C-GEM coupled with the OMEN_SED sediment module and constrained, upstream by the pyNuts-Riverstrahler model, which describes the transfer of nutrients and carbon from the headwaters streams to the outlets of river hydrosystems. In its current version, C-GEM resolves tidally induced transport within the estuary along its longitudinal axis and its biogeochemical module includes all the main processes involving carbon and nutrients (i.e. production, remineralization, nitrification, denitrification…). The addition of a new explicit benthic module allows simulating sediments processes and burial which are essential to properly quantify carbon and nutrient retention. The strategy to simulate estuaries devoid of measurements relies on Monte Carlo simulations performed by varying the model’s parameterization constrained by an extensive literature survey and thoroughly validated on well monitored reference systems. Our results over the 2014-2019 period provide an insight into the parameters controlling the temporal and spatial variability of carbon and nutrient retention within a large set of estuaries with varying riverine nutrients loads and ranging from very small (

Nitrous oxide (N2O) emissions from agricultural soil were studied during 6 consecutive years on three plots of two real farms. We analyzed a total of 37 agricultural sequences: 20 sequences with crops including wheat, maize, and legumes and 17 fallow sequences with cover crops, volunteers or bare fallow soils. Controlling factors of N2O emissions were disentangled by using three approaches: (i) applying a random forest algorithm then extracting the most important predictors; (ii) analyzing all sequences separately as a function of the rain and soil mineral nitrate (SMN) content in soils; and (iii) experimentally, by watering soils with different SMN contents. The results showed that rainfall (and hence soil moisture) exerted the greatest control over N2O emissions, followed by daily maximum temperature and SMN. Regarding crop sequences, 6-year N2O cumulative emissions rates (g N2O-N ha(-1)) ranked as follows: legumes (967) < maize (1192) < cereals (1375). Lowest cumulative N2O emissions at the Derrier conventional, no-till, farming plot (similar to 6000 kg N ha(-1)) was observed compared to similar to 15000 kg N2O-N ha(-1) measured at the tilled organic farming Chantemerle and Barrie`re plots. Further, cumulative N2O emissions were rather important during fallow periods with or without cover crops. This study thus supports that N2O emissions need to be measured all year round, including both cropping and fallow periods to grasp the full rotation cycles. This long-term study of N2O emissions gathered a large number of data on N2O emissions over a variety of crops and fallow management and helped to initiate a typology of N2O emissions by crop.

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.

Landscape 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 km(2)) 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 (upstream-downstream) 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.

Increasing concerns over water eutrophication due to agricultural phosphorus (P) loss have led to the development of indicators to assess the risk of P release from agricultural soils. Recently, a logarithmic equation linking the degree of phosphorus saturation (DPS) to the simple water-soluble P (WSP) content of soils has been proposed as a universal method to assess this risk based, however, mainly on the analysis of well-drained soils. Here, we studied the P sorption properties and DPS values of 69 hydromorphic soils from cultivated and uncultivated wetland zones located in Brittany, Western France, to test whether the method could also apply to poorly-drained soils. The bulk soil analysis showed that P contents of the studied hydromorphic soils were 30% to 80% higher than P contents normally found in Brittany soils, evidencing a possible P enrichment process. Adsorption isotherms revealed a surprisingly high variability in the P sorption properties as a function of the location of the soil (maximum P adsorption capacity ranging from 500 to 1850 mg kg(-1)), which is caused by variations in the phases controlling P sorption in soil (from clay to organic matter and/or iron and aluminium oxides, depending on the soil location). Distinct relationships between DPS and WSP values were also obtained depending on the location of the soils. The obtained DPS versus WSP relationships showed that the P saturation threshold above which the risk of dissolved P release increases markedly is 30% lower on average for hydromorphic soils than for well-drained soils. Hydromorphic soils appear to be more at risk of releasing dissolved P at the same DPS values than well-drained soils. The present study indicates an underestimation of the P release risk from hydromorphic soils by the existing method developed for well-drained soils and calls for the development of specific risk assessment tools for hydromorphic soils, especially given on the strong spatial heterogeneity of their P sorption properties.

In excess compared to the other major nutrients, nitrogen (N) ­-transported mainly in the form of nitrates- from land surfaces to coastal areas, is responsible for harmful algal blooms in coastal areas. In France, most of the water loads of N transferred to the sea comes from fertilization on agricultural surfaces and their highly leached surpluses. The distance between the sources of nutrients and the manifestations of eutrophication is one of the difficulties encountered in reducing coastal eutrophication. The present study, which aims to model the N cascade at a national scale, for the current situation and according to different agricultural/dietary scenarios, is a basis for discussion with river-basin managers, who are required to enforce the Marine Strategy Framework Directive that sets the conditions for good status of marine environments. Current N surpluses (2015-2018) are calculated via the GRAFS (Generalized Representation of the Agro-Food System), method (Le Noe et al. 2017), at the NUTS-2 scale (French regions) for arable land, permanent grassland and permanent crops. An approach based on yearly run-off coupled with a riparian denitrification routine allows linking these surpluses to average baseflow/quickflow concentrations in elementary catchments (average size: 5.8 km2). These diffuse lateral inputs, plus point-source inputs, are then integrated into the pyNuts-Riverstrahler modelling platform (Billen et al. 1994, Raimonet et al. 2019), which calculates nitrogen transformations and transfers along the river network. The model outputs have a kilometric spatial resolution and a 10 days temporal resolution, making it possible to finely represent the spatio-temporal variability of N concentrations and loads on the French territory. Different plausible scenarios for the future of the agro-food system in France, with a gradient of territorial specialisation/N intensities, are then modelled within the GRAFS-pyNuts-Riverstrahler approach to assess their impacts on the N cascade at the national scale. This study is part of the Nuts-STeauRY project (funded by the OFB: https://nuts-steaury.cnrs.fr/), which aims to demonstrate the contribution of integrated land-sea modelling to the realisation of spatialized scenarios to limit coastal eutrophication in France. Carbon, phosphorus and dissolved silica will also be modelled for this project. Billen2014:10.1007/BF00007414 LeNoë2017:10.1016/j.scitotenv.2017.02.040 Raimonet2019:10.3389/fmars.2018.00136

Landscape 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 (5-150km²), 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.

Protecting water quality at catchment scales is complicated by the high spatiotemporal variability in water chemistry. Consequently, determining pollutant sources requires costly monitoring strategies to diagnose causes and guide management solutions. However, recent studies have shown that spatial patterns in water chemistry can be persistent at catchment scales, potentially allowing identification of pollution sources and sinks with just a few sampling campaigns. Here, we tested a new method to quantify spatial persistence (SP) of water chemistry patterns with data from synoptic samplings in 22 headwater subcatchments within a 375 km 2 catchment in western France (March 2018 to July 2019). This new method to quantify SP reduces dependence on long‐term metrics such as flow‐weighted concentrations, which are usually uncertain or unavailable. We applied the method to 16 ecologically relevant water quality parameters, including soluble reactive phosphorus, nitrate, and dissolved organic carbon. The results showed an average SP of 0.68 among parameters during the study period. For most parameters, SP was higher during the high‐flow winter period but lower and more variable during the low‐flow summer period. We found that the SP ultimately depended on the ratio between the temporal and spatial coefficients of variation (variance explained: 70%) rather than the temporal synchrony among subcatchments (variance explained: 4%). These results demonstrate that in these temperate catchments, synoptic sampling during the high‐flow winter period allows efficient identification of source and sink subcatchments, while more frequent samplings are needed to characterize ecological conditions at low flow.

Nitrogen (N) and phosphorus (P) exports from rural landscapes can cause eutrophication of inland and coastal waters. Few studies have investigated the influence of the spatial configuration of nutrient sources—i.e. the spatial arrangement of agricultural fields in headwater catchments—on N and P exports. This study aimed to (1) assess the influence of the spatial configuration of nutrient sources on nitrate (NO3−) and total phosphorus (TP) exports at the catchment scale, and (2) investigate how relationships between landscape composition (% agricultural land-use) and landscape configuration vary depending on catchment size. We analysed NO3− and TP in 19 headwaters (1–14 km², Western France) every two weeks for 17 months. The headwater catchments had similar soil types, climate, and farming systems but differed in landscape composition and spatial configuration. We developed a landscape configuration index (LCI) describing the spatial organisation of nutrient sources as a function of their hydrological distance to streams and flow accumulation zones. We calibrated the LCI’s two parameters to maximise the rank correlation with median concentrations of TP and NO3−. We found that landscape composition controlled NO3− exports, whereas landscape configuration controlled TP exports. For a given landscape composition, landscape spatial configuration was highly heterogeneous at small scales (< 10 km2) but became homogeneous at larger scales (> 50 km2). The spatial configuration of nutrient sources influences TP but not NO3− exports. An ideal placement of mitigation measures to limit diffuse TP export should consider both the hydrological distance to streams and flow accumulation zones.

Characterizing and understanding spatial variability in water quality for a variety of chemical elements is an issue for present and future water resource management. However, most studies of spatial variability in water quality focus on a single element and rarely consider headwater catchments. Moreover, they assess few catchments and focus on annual means without considering seasonal variations. To overcome these limitations, we studied spatial variability and seasonal variation in dissolved C, N, and P concentrations at the scale of an intensively farmed region of France (Brittany). We analysed 185 headwater catchments (from 5–179 km2) for which 10-year time series of monthly concentrations and daily stream flow were available from public databases. We calculated interannual loads, concentration percentiles, and seasonal metrics for each element to assess their spatial patterns and correlations. We then performed rank correlation analyses between water quality, human pressures, and soil and climate features. Results show that nitrate (NO3) concentrations increased with increasing agricultural pressures and base flow contribution; dissolved organic carbon (DOC) concentrations decreased with increasing rainfall, base flow contribution, and topography; and soluble reactive phosphorus (SRP) concentrations showed weaker positive correlations with diffuse and point sources, rainfall and topography. An opposite pattern was found between DOC and NO3: spatially, between their median concentrations, and temporally, according to their seasonal cycles. In addition, the quality of annual maximum NO3 concentration was in phase with maximum flow when the base flow index was low, but this synchrony disappeared when flow flashiness was lower. These DOC–NO3 seasonal cycle types were related to the mixing of flow paths combined with the spatial variability of their respective sources and to local biogeochemical processes. The annual maximum SRP concentration occurred during the low-flow period in nearly all catchments. This likely resulted from the dominance of P point sources. The approach shows that despite the relatively low frequency of public water quality data, such databases can provide consistent pictures of the spatio-temporal variability of water quality and of its drivers as soon as they contain a large number of catchments to compare and a sufficient length of concentration time series.

The majority of freshwater ecosystems worldwide suffer from eutrophication, particularly because of agriculture-derived nutrient sources. In the European Union, a discrepancy exists between the scale of regulatory assessment and the size of research catchments. The Water Framework Directive sets water quality objectives at the mesoscale (50-500 km2), a scale at which both hillslope and in-stream processes influence carbon (C), nitrogen (N) and phosphorus (P) dynamics. Conversely, research catchments focus on headwaters to investigate hillslope processes while minimising the influence of river processes on C-N-P dynamics. Because hillslope and river processes have common hydro-climatic drivers, the relative influence of each on C-N-P dynamics is difficult to disentangle at the mesoscale. In the present study, we used repeated synoptic sampling throughout the river network of a 300 km2 intensively farmed catchment, spatial stochastic modelling and mass balance calculations to analyse this mesoscale conundrum. The main objective was to quantify how river processes altered C-N-P hydrochemical dynamics in different flow, concentration and temperature conditions. Our results show that flow was the main control of alterations of C-N-P dynamics in the river network, while temperature and source concentration had little or no influence. The influence of river processes peaked during low flow, with up to 50% of dissolved organic carbon (DOC) production, up to 100% of nitrate (NO3) retention and up to 50% of total phosphorus (TP) retention. Despite high percentages of river processes at low flow, their influence on annual loads was low for NO3 (median of -10%) and DOC (median of +25%) but too variable to draw conclusions for TP. Because of the differing river alteration rates among carbon and nutrients, stoichiometric ratios varied greatly from headwaters to the outlet, especially during the eutrophication-sensitive low-flow season.

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 “r” 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.

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.

Este artigo discutiu os conflitos de uso da terra nas áreas de preservação permanente (APPs) hídricas da Bacia de Contribuição da Represa Dr. João Penido em Juiz de Fora, MG, Brasil. Esta Represa pode abastecer até 65% do município na estação seca. A ênfase na APP hídrica justifica-se por cumprir diversos serviços ambientais, pela maior facilidade de ocupação e pela tendência histórica de urbanização sobre estas áreas. A metodologia constou de revisão conceitual, busca das legislações associadas e elaboração de base de dados através do Programa ArcGIS 10.2. Os resultados mostraram que mais de 40% das APPs hídricas estão ocupadas com pastagem e pastagem degradada. Cerca de apenas 20% estão ocupadas com Mata Atlântica, algo preocupante para uma bacia de manancial de abastecimento. O retrocesso nas legislações ambientais resultou em perdas da ordem de 12% entre o NCF e a Lei municipal e 8,3% entre o NCF e as leis florestais revogadas, prevendo-se o agravamento da ocupação das APPs com prejuízo para a quantidade e qualidade da água dessa Bacia.

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.