Water quality predictions through linear regression - A brute force algorithm approach.

Linear regression is one of the oldest statistical modeling approaches. Still, it is a valuable tool, particularly when it is necessary to create forecast models with low sample sizes. When researchers use this method and have numerous potential regressors, choosing the group of regressors for a model that fulfills all the required assumptions can be challenging. In this sense, the authors developed an open-source Python script that automatically tests all the combinations of regressors under a brute-force approach. The output displays the best linear regression models, regarding the thresholds set by users for the required assumptions: statistical significance of the estimations, multicollinearity, error normality, and homoscedasticity. Further, the script allows the selection of linear regressions with regression coefficients according to the user's expectations. This script was tested with an environmental dataset to predict surface water quality parameters based on landscape metrics and contaminant loads. Among millions of possible combinations, less than 0.1 % of the regressor combinations fulfilled the requirements. The resulting combinations were also tested in geographically weighted regression, with similar results to linear regression. The model's performance was higher for pH and total nitrate and lower for total alkalinity and electrical conductivity.•A Python script was developed to find the best linear regressions within a dataset.•Output regressions are automatically selected based on regression coefficient expectations set by the user and the linear regression assumptions.•The algorithm was successfully validated through an environmental dataset.

A combined GIS-MCDA approach to prioritize stream water quality interventions, based on the contamination risk and intervention complexity.

Water management decisions are complex ever since they are dependent on adopted politics, social objectives, environmental impacts, and economic determinants. To adequately address hydric resources issues, it is crucial to rely on scientific data and models guiding decision-makers. The present study brings a new methodology, consisting of a combined GIS-MCDA, to prioritize catchments that require environmental interventions to improve surface water quality. A Portuguese catchment, Ave River Basin, was selected to test this methodology due to the low water quality. First, it was calculated the contamination risk of each catchment, based on a GIS-MCDA using point source pressures, landscape metrics, and diffuse emissions as criteria. This analysis was compared to local data of ecological and chemical status through ANOVA and the Tukey test. The results showed the efficiency of the method since the contamination risk was lower for catchments under a good status and higher in catchments with a lower classification. In a second task, it was calculated the intervention complexity using a different GIS-MCDA. For this approach, it was chosen five criteria that condition environmental interventions, population density, slope, percentage of burned areas, Strahler order, and the number of effluent discharge sites. Both multicriteria methods were combined in a graphical analysis to rank the catchments intervention priority, subdividing the prioritization into four categories from 1st to 4th, giving a higher preference for catchments with high contamination risk and low intervention complexity. As a result, catchments with a good status were dominantly placed under low intervention priority, and catchments with a lower ecological status were classified as a high priority, 1st and 2nd. In total, 248 catchments were spatially ranked, which is an essential finding for decision-makers, that are willing to safeguard the catchment water quality.

Integrating ecosystem services into sustainable landscape management: A collaborative approach.

The Paiva River is considered one of the least polluted rivers in Europe and its watershed has a high conservation value. However, the Paiva River basin suffers pressures related with recurrent disturbances in land use, such as forest fires, agricultural activities, urbanization and pressures that affect the natural hydromorphological conditions and the continuity of watercourses. Blue and Green Infrastructures (BGINs) emerge to improve biodiversity, sustainability and the supply of ecosystem services while improving socioeconomic aspects. Thus, this article aims to identify priority areas in the basin, for intervention with these infrastructures. For that, a spatial multicriteria decision analysis (MDCA) was carried out according to several data related to the Paiva River Basin. As local politicians and responsible entities for the natural resources management are the main experts on the problems and their possible solutions at the local level, they were involved in this decision-making model. Therefore, these specialized stakeholders did the weighting assignment according to the most or least importance of the same for the work. The map of priority locations to implement BGINs was obtained in the sequel. To the top 5 priority areas, stakeholders attributed the best solutions based on nature. The most recommended BGINs were recovery/maintenance of riparian vegetation and conservation and reforestation of the native forest, both presented in four of the five areas, and introduction of fuel management strips presented in three of the five areas. Thus, we concluded that it is extremely important to include the communities and the competent entities of nature and environment management in scientific projects related to conservation, forming a synergy that makes it possible to combine scientific knowledge with local experience acquired in the field. This project uses a very flexible methodology of local data and can be a great example to be implemented in other hydrographic basins anywhere in the world.

Is it safe to remove a dam at the risk of a sprawl by exotic fish species?

The longitudinal dimension of river connectivity has been significantly disrupted by barriers to compensate for water demand in the long periods of water scarcity in the Iberian Peninsula. The scale of this modification is widespread in the Portuguese part of Douro River network where, side to side with agriculture water demand, there is a constant increase in hydropower production. Thus, native species in Iberian freshwater systems, performing reproductive migrations along the rivers, are strongly affected by the amplification of fragmentation caused by the tremendous density of transversal obstacles in this river basin. We aimed to prioritize dam removal in the Portuguese part of Douro River, mainly considering obsolete barriers (small dams, weirs) based on a spatial multicriteria decision analysis (GIS-MCDA) based on a prioritization procedure. A diversity of parameters were used to prioritize (rank) the dam's suitability for removal, considering the losses of connectivity and fish biodiversity, habitat degradation, negative effects on water quality and ecological conditions, and socio-economic factors. Different weights were assigned to the different attributes in each criterion according to their importance. The analysis also included a significant constraint: the potential spreading of exotic invasive fish species if connection was reestablished through dam removal. This procedure started with the georeferencing of 1201 transversal obstacles that were further characterized for their relative permeability to fish migration. In conclusion the model used allowed to identify 158 priority barriers, as well as the 5 most fragmented tributaries, which means the most impacted by river regulation. In 8 cases the barriers were big dams (> 15 m), whereas in the remaining 150 were weirs. From a final rank of 20 most impacting structures, the MCDA results also identified two cases where potential removal could trigger the additional impact to native fish species related to the sprawl of alien populations.

Seasonal effect of land use management on gill histopathology of Barbel and Douro Nase in a Portuguese watershed.

The Vilariça River (located in the northeast of Portugal) is inserted in an agricultural basin and it was chosen to replace the spawning grounds for fish, that was lost due to the construction of dams in the Sabor River. Thus, it is essential to study the effect of agricultural practices on water quality and in the health status of fish. The barbel (Luciobarbus bocagei) and Douro nase (Pseudochondrostoma duriense) were the selected species and the work was developed in two seasons (Summer 2016 and Winter 2017). For that, the histopathological changes of fish gill were used as biomarkers, through a semi-quantitative approach that considers the injuries severity. And the water quality assessment criteria followed the methodologies proposed for classifying the status of surface water bodies from Portugal. The current study showed severe histopathological changes in both species and both seasons, and the water was classified as polluted and extremely polluted in Summer and Winter respectively. The pollution in Summer was due to high temperatures, low dissolved oxygen and major concentration of As and Mn, and in Winter is due to the high concentration of Total Suspended Solids, nitrites and Cd. The increase of values of physico-chemical parameters on the water was caused by the less streamflow and excessive agricultural fertilization in Summer which arrive the river by irrigation, and by the erosion of soil particles with heavy metals associated in Winter. Also, the canonical analysis showed that physico-chemical parameters concentrations in Summer justify the major prevalence of aneurism in barbel and exudate in nase and Winter the major prevalence of hypertrophy in barbel. In conclusion, the study showed that the gill injuries of barbel and Douro nase was correlated with the water quality and it is influenced by seasonal agricultural practices and the flow regime.

First record of Neobenedenia melleni (Monogenea: Capsalidae) in dog snapper (Lutjanus jocu) in the western South Atlantic / Primeiro registro de Neobenedenia melleni (Monogenea: Capsalidae) em dentão (Lutjanus jocu) no oeste do Atlântico Sul

Neobenedenia melleni (MacCallum, 1927) (Monogenea) é um patógeno amplamente distribuído em cultivo de teleósteos marinhos no mundo. Com o crescimento da piscicultura marinha no Brasil, faz-se necessário um maior cuidado em relação à identificação e ao tratamento das principais patologias nesse tipo de cultivo. Este estudo relata a primeira ocorrência de Neobenedenia melleni em dentão (Lutjanus jocu) no oeste do Atlântico Sul. Também são sugeridos procedimentos adotados para eliminação desse parasito em peixes cultivados em laboratório.(AU)

Flood risk attenuation in critical zones of continental Portugal using sustainable detention basins.

According to the Floods Directive (Directive 60/2007/EC), the management of floods represents an obligation of each EU member state to defend human lives as well as the economic well-being of societies, especially in areas defined as critical. The purpose of this study was to develop a flood attenuation model based on detention basins in the 23 critical flood risk zones of continental Portugal, capable to eliminate the high and very high flood risk areas instead of attempting to ensure full control of the flood in all potentially threatened areas. The model workflow comprised the sequential use of engineering formulae based on historical peak flows and a zoning algorithm embedded in a Geographic Information System. The formulas allowed to set up the volume of river water to retain in a detention basin during a flood, as well as the smallest catchment area (A) producing this volume. The results were divided into sustainable (h ≤ 8 m) or non-sustainable (h > 8 m) detention basins. Thus, these results indicated the possibility to install 27 sustainable and 75 non-sustainable detention basins in specific catchments within the critical zones contributing watersheds. The number of sustainable detention basins is reduced by about 30% when the full flood control model is used. Because the construction of non-sustainable (engineered) dams is extremely costly, the only possible way to mitigate flood risk in these critical zones would be to couple flood attenuation with hydroelectric use, or through the implementation of an extensive reforestation program in the catchment with the purpose to increase evapotranspiration and reduce runoff.

A new radon prediction approach for an assessment of radiological potential in drinking water.

Inhaled radon from groundwater used for domestic purposes is one of the sources of natural radioactivity into indoor air. Due to uranium-bearing minerals occurrences, hydrogeochemical conditions, tectonic structures, and hydraulic circuits, the radon pathway from rocks to groundwater is quite unpredictable. High radon potential from bedrocks is not always associated with high radon levels in groundwater. Besides, inhaled radon from domestic use may also increase the exposure toindoor radon levels. This innovative methodology using hydrogeochemical conditions and groundwater flow transport was used for radon predictions in the underground to ensure safe drinking water ingestion and inhalation. This innovative radon prediction methodology is based on classic hydrogeochemical analyses (Eh-pH, Piper, Schöeller and Gibb's diagrams) and multivariate statistical analyses (Principal Component Analysis and Pearson's correlation). High dissolution of major ions does not imply high radon mobilization from rocks to groundwater. The travel time was estimated to developed a flow transport of contaminated groundwater. Radiological results show that of the 25 sampled springs, five of them contained radon concentrations above the Portuguese imposed limit (222Rn = 500 Bq·L-1), and 16 of them with values above the WHO recommended limit (222Rn = 100 Bq·L-1). Overall, this new approach of radon prediction showed that uranium enrichment in rocks at ideal hydrochemical conditions and emanation coefficient, and shallow circuits, are responsible for radon increasing in drinking water. The proposed approach allow to predict the areas with high radon potential groundwaters, being a tool to be used by water planners and policy makers for corrective and preventive measures in shallow groundwater flows. To safeguard clean water within the predefined deadline of Sustainable Development Goals (2030) and to ensure human health in compliance with WHO guidelines for safe drinking water, should be established priority water protection policies to reduced radon in this contaminated springs (n = 16).

A structural equation model to predict macroinvertebrate-based ecological status in catchments influenced by anthropogenic pressures.

A Partial Least Squares-Path Model (PLS-PM) was developed for the Ave River Basin (North of Portugal), and the results used in a scenario analysis. The data for PLS-PM comprised a set of anthropogenic pressures, water quality parameters, and a macroinvertebrate-based biodiversity index (IPtIN) used to assess the ecological status of streams. These groups of measured parameters (called latent variables) were given the names "Pressures", "Contamination" and "Ecological Integrity". Besides, latent variables were connected through path coefficients representing potential causal effects among them. In a large portion of Ave the ecological status of streams is currently bad or poor. Nitrate and coliforms were the most weighted measured variables of latent variable "Contamination", with w ≈ 0.7 and w ≈ 0.2, respectively. The highest "Pressures" weights were ascribed to livestock farming (0.7) and population density (0.4). The connections "Pressures"-"Contamination" and "Contamination" - "Ecological Integrity" exposed a sequence of direct negative effects between the three variables, expressed in the corresponding path coefficients (pc = 0.87 and pc = -1.11). Paradoxically, a direct negative effect of "Pressures" over "Ecological Integrity" was absent (pc = 0.29). Therefore, the poor ecological status of local stream waters might not be directly related to the presence of potentially threatening contaminant sources (the "Pressures"), but to ineffective monitoring of livestock farming and wastewater treatment activities that potentiate (accidental) releases of contaminants into the streams. The lack of a direct link "Pressures" - "Ecological Integrity" supported the results of pressure change versus IPtIN change scenarios. Regardless of some significant reductions of anthropogenic activity and population density until 2027, announced by the Portuguese Environmental Agency, the scenarios could not predict improvement of ecological status beyond the "moderate" category. The study recommendations were therefore to prevent contamination through proper implementation and monitoring of existing watershed management plans. The adequate treatment of domestic effluents and the control of livestock farming residues are urgent.

An approach to validate groundwater contamination risk in rural mountainous catchments: the role of lateral groundwater flows.

Computer models dedicated to the validation of groundwater contamination risk in the rural environment, namely the risk of contamination by nitrate leachates from agriculture fertilizers, are frequently based on direct comparison of risky areas (e.g., cropland, pastures used for livestock production) and spatial distributions of contaminant (nitrate) plumes. These methods are fated to fail where lateral flows dominate in the landscape (mountainous catchments) displacing the nitrate plumes downhill and from the risky spots. In these cases, there is no connection between the spatial location of risky areas and nitrate plumes, unless the two locations can be linked by a contaminant transport model. The main purpose of this paper is therefore to introduce a method whereby spatio-temporal links can be demonstrated between risky areas (contaminant sources), actual nitrate plumes (contaminant sinks) and modeled nitrate distributions at specific groundwater travel times, thereby validating the risk assessment. The method assembles a couple of well known algorithms, namely the DRASTIC model [1,2] and the Processing Modflow software (https://www.simcore.com), but their combination as risk validation method is original and proved efficient in its initial application, the companion paper of Pacheco et al. [3].

A partial least squares - Path modeling analysis for the understanding of biodiversity loss in rural and urban watersheds in Portugal.

The main purpose of this study was to use Partial Least Squares - Path Modeling (PLS-PM) to quantify the contributions of natural and human-induced threats to biodiversity loss in rural and urban watersheds. The study area comprised the Sabor and Ave river basins, located in northern Portugal. The Sabor is rural and sparsely populated while the Ave is urbanized, industrialized and densely populated. Within PLS-PM, threats are called exogenous latent variables while the ultimate environmental consequence (biodiversity loss) is termed endogenous latent variable. Latent variables are concepts represented by numerical parameters called formative variables. The selected latent variables were given the names "pressures", "contamination" and "ecological integrity". The most important "pressures" were the wildfire risk, the percentage of urban area in sub-catchments, the diffuse emissions of livestock nitrogen (N) and agriculture/forest phosphorus (P), and the point source emissions of urban N, P and biochemical oxygen demand, as well as of industrial N. The latent variable called "contamination" was primarily represented by stream water concentrations of phosphate, suspended solids and dissolved oxygen. And finally, the "ecological integrity" was represented by the he North Invertebrate Portuguese Index. The results unequivocally showed that point source emissions in the Sabor (except industrial N) and stream water contamination in the Ave determine biodiversity loss. These contrasting influences suggest that Ave basin has evolved from a catchment where man once produced localized negative effects on stream ecological integrity (a condition still observed in the Sabor basin) to a catchment where the dense human occupation has covered the entire area with urban contaminant sources, somewhat generalizing the local effects. The attribution of local effects to biodiversity loss in the rural catchment and of regional effects in the urban catchment is confirmed by the results of a study covering the entire planet.

Rainwater harvesting in catchments for agro-forestry uses: A study focused on the balance between sustainability values and storage capacity.

Rainwater harvesting (RWH) is used to support small-scale agriculture and handle seasonal water availability, especially in regions where populations are scattered or the costs to develop surface or groundwater resources are high. However, questions may arise as whether this technique can support larger-scale irrigation projects and in complement help the struggle against wildfires in agro-forested watersheds. The issue is relevant because harvested rainwater in catchments is usually accumulated in small-capacity reservoirs created by small-height dams. In this study, a RWH site allocation method was improved from a previous model, by introducing the dam wall height as evaluation parameter. The studied watershed (Sabor River basin) is mostly located in the Northeast of Portugal. This is a rural watershed where agriculture and forestry uses are dominant and where ecologically relevant regions (e.g., Montezinho natural park) need to be protected from wildfires. The study aimed at ranking 384 rainfall collection sub-catchments as regards installation of RWH sites for crop irrigation and forest fire combat. The height parameter was set to 3m because this value is a reference to detention basins that hold sustainability values (e.g., landscape integration, environmental protection), but the irrigation capacity under these settings was smaller than 10ha in 50% of cases, while continuous arable lands in the Sabor basin cover on average 222ha. Besides, the number of sub-catchments capable to irrigate the average arable land was solely 7. When the dam wall height increased to 6 and 12m, the irrigation capacity increased to 46 and 124 sub-catchments, respectively, meaning that more engineered dams may not always ensure all sustainability values but warrant much better storage. The limiting parameter was the dam wall height because 217 sub-catchments were found to drain enough water for irrigation and capable to store it if proper dam wall heights were used.

Integrative assessment of river damming impacts on aquatic fauna in a Portuguese reservoir.

The impacts of river damming on aquatic fauna are assessed and then integrated across hierarchical scales, portrayed as nested circles. The outer circles characterize the studied site for habitat disturbance and hydrologic regime during the construction and filling phases. The inner circles characterize the construction and filling phase zones for water quality parameters and aquatic fauna. The procedure for integrating the impacts comprises two consecutive stages: in the task stage, inner circles are characterized through field and laboratory work involving sampling and analyses of water aliquots and aquatic fauna; in the impact assessment stage, circle data are processed in ecological and statistical algorithms, which allow identification of changes in abundance and composition of aquatic fauna communities and their integration with changes in water quality parameters across the construction and filling phase zones. The integrative assessment of river damming impacts on aquatic fauna was carried out in the Sabor River dam (Portugal). This dam created two reservoirs: primary and secondary. Changes in water quality caused by dam construction and stream water impoundment were significant, marked by increases in temperature and electric conductivity downstream, accumulation of phosphorus and nitrogen in the reservoirs triggering the growth of algae and the increase of chlorophyll a, and drop of transparency. These changes were aggravated in the secondary reservoir. The consequences of water deterioration for aquatic fauna were severe, marked by abrupt declines of native fish species and invasion of exotic species even upwards the reservoirs. The ecological status determined from ecological quality ratios of benthic macroinvertebrate assemblages were also affected, changing from good-fair in the unaffected watercourses to fair-poor in the lakes.

The impact of freshwater metal concentrations on the severity of histopathological changes in fish gills: A statistical perspective.

The purpose of this study was to relate the severity of histopathological changes in fish gills with changes in metal concentrations of freshwater samples, and to use the relationships as premature warnings of impairment in aquatic fauna populations. The investigated species were the native barbel (Luciobarbus bocagei) and boga (Pseudochondrostoma sp.), and the introduced trout (Oncorhynchus mykiss), collected from 6 northern Portuguese rivers in a total of 249 individuals. The sampling sites have been linked to different ecological status by the official authorities. The sampling has been repeated 4 times to cover different hydrologic and environmental conditions. The analyzed metals were aluminum, arsenic, cadmium, cobalt, chromium, copper, manganese, nickel, lead and zinc. For each fish, 30 filaments of a gill arch were observed in a light microscope, and the histopathological changes evaluated according to a 6-degree gradation scale that combines the extent and severity of each lesion. The relationships between the histopathological and the chemical results were investigated by the non-parametric Goodman Kruskal gamma correlation and Partial Least Squares regression (PLS). The statistical results highlighted the importance of filament epithelium proliferation (FEP) as key biomarker to the toxicity of sub lethal concentrations of metals, because FEP was significantly correlated with all analyzed metals and explained through PLS regression by concentration changes of Cu, Zn, Mn, Cr and As. A refined regression analysis, where histopathological data on the 3 species were processed in separate, revealed that FEP severity is especially sensitive to changes in metal concentrations in boga. Thus, monitoring studies on the ecological status of northern Portuguese rivers would benefit in time and cost if FEP is used as biomarker and boga as species. Naturally, the option for this species depends on the availability of boga individuals along the stream reaches selected for the monitoring programs.

Assessing anthropogenic impacts on riverine ecosystems using nested partial least squares regression.

The results of three Partial Least Squares (PLS) regression models were used to gain a holistic view on the consequences of natural processes and anthropogenic pressures for water quality degradation and biodiversity decline in a multi-use watershed. The processes were soil erosion and wildfire risk; the pressures comprised land use conflicts, leachates from domestic and industrial waste, arable farming intensity and livestock density. Water quality was characterized for concentrations of nutrients (nitrate, phosphate), oxygen demands (Biochemical Oxygen Demand - BOD5, Chemical Oxygen Demand - COD) and various metals (e.g., As, Cr). Ecological integrity was assessed by the recently developed MELI (Multiple Ecological Level Index). In total, 18 variables were processed in the regression models. Two models were called "nested models" because they dealt with initial (pressures), intermediate (water quality) and final (MELI) environmental descriptors, used as dependent (MELI, quality) or independent (quality, pressures) variables. The third was called "bypass model" because it dealt solely with initial and final descriptors. Overall, the results of PLS regression linked the ineffective treatment of domestic sewage to water quality and ecological integrity declines in the studied watershed. Put another way, all models recurrently affirmed the major role of local factors, meaning of point source pollution, in determining the quality of stream water and the integrity of freshwater ecosystems. Sources of diffuse pollution were accounted for as contributing factors in the PLS regressions, but their influence was scarcely perceptible in the results. The poor treatment of domestic effluents is a public concern. In their strategic plans for mitigating this problem in the forthcoming years, administrative authorities are concentrated on management initiatives to improve the quality of provided services, instead of considering the construction of new wastewater treatment plants.

Characterization and molecular epidemiology of extensively prevalent nosocomial isolates of drug-resistant Acinetobacter spp.

Acinetobacter sp isolates deserve special attention once they have emerged globally in healthcare institutions because they display numerous intrinsic and acquired drug-resistance mechanisms. This study assessed the antibiotic susceptibility profile, the presence of the genetic marker blaOXA-23, and the clonal relationship among 34 nosocomial isolates of Acinetobacter spp obtained at a hospital in southeastern Brazil. Antibiotic sensitivity analysis was performed by the standard disc-diffusion method. All isolates were found to be extensively resistant to several drugs, but sensitive to polymyxin B. A polymerase chain reaction (PCR) assay was used to detect the blaOXA-23 gene, which is associated with carbapenem resistance. The genetic profile and the clonal relationship among isolates were analyzed via enterobacterial repetitive intergenic consensus (ERIC)-PCR. The Acinetobacter spp were divided into four groups with 22 distinct genetic subgroups. ERIC-PCR analysis revealed the genetic diversity among isolates, which, despite having a heterogeneous profile, displayed 100% clonality among 56% (19/34) of them.