Use of the water quality index and dissolved oxygen deficit as simple indicators of watersheds pollution

The use of the water quality index (WQI) and the dissolved oxygen deficit (D) as simple indicators of the watersheds pollution was investigated and compared in the Municipality of Las Rozas (north-west of Madrid, Spain). The quality of the water in Guadarrama and Manzanares rivers and Paris Park ponds, the main watersheds of this area was investigated during 2 years (from September 2001 to September 2003). It was found that the WQI was very useful for the classification of the waters monitored. The WQI was 70, which corresponds to “good” quality water at the sampling point 1 (entrance of Las Rozas) and decreased to around 64 (medium quality) at the sampling point 6 (outlet of Las Rozas) in the case of Guadarrama River. The WQI was around 65 in the influents of Manzanares River. Finally, in Paris Park the WQI ranged from around 72–55, which corresponded to a classification from “good” to “medium” quality, respectively. A high linear relationship between the WQI and the dissolved oxygen deficit (D) was found. Therefore, a fast determination of WQI may be carried out knowing the values of D, which are easily obtainable by field measurements. It was found an influence of the climate conditions on the values of WQI and D.     

Comment on “Assessing water quality of five typical reservoirs in lower reaches of Yellow River,China: Using a water quality index method” by Wei Hou,Shaohua Sun,Mingquan Wang,Xiang Li,Nuo Zhang,Xiaodong Xin,Li Sun,Wei Li,and Ruibao Jia (2016) [Ecological Indicators, 61, 309–316]

Hou et al. (2016) recently developed a water quality index (WQI) for assessing water quality of five typical reservoirs. Despite all the merits of the practical WQI, it suffers from lack of uncertainty consideration; a fact that motivated the present discussion focusing on mitigation of uncertainty in water quality assessment. In this regard, superiority of employing fuzzy WQI (FWQI) rather than crisp WQI is emphasized. Due to robustness of FWQI in handling uncertainties surrounding data acquisition, employment of fuzzy concept can improve water quality assessment and monitoring to generate results which are more consistent with real world conditions.     

Assessing water quality of five typical reservoirs in lower reaches of Yellow River,China: Using a water quality index method

To assess water quality of reservoirs in lower reaches of Yellow River using the water quality index (WQI) method and try to compare water quality and main contaminations of mountain and Yellow River reservoirs, water samples were carried out over 6 years. Nine water variables were selected to participate WQI calculation by Principal Component Analysis (PCA). WQI values ranged from 17.8 to 77.8 in five reservoirs, which indicated “good” to “very poor” water quality of reservoirs. No significant differences in WQIs were found between mountain and Yellow River reservoirs. A major finding from our study is that mercury was the main contamination in 5 reservoirs, while TP (total phosphorus) and SO₄ were another main contaminations in mountain and Yellow River reservoirs, respectively. Application of the WQI is suggested to be a helpful tool that enables the public and decision makers to evaluate water quality of drinking reservoirs in lower reaches of Yellow River.     

A modified drinking water quality index (DWQI) for assessing drinking source water quality in rural communities of Khuzestan Province,Iran

We reconsidered the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) to achieve an efficient drinking water quality index (DWQI) for assessment of drinking source water quality in rural communities of Khuzestan Province, Iran in 2009–2013. In contribution with a panel of water quality experts, the CCME WQI was mainly modified by four changes: (1 and 2) assigning weight factors for input parameters and index factors, (3) modifying excursion concept for carcinogens and bioaccumulative pollutants and (4) removing effect of unequal measurements of input parameters. The DWQI characterizes the drinking source water quality through comparing the measured values of input parameters with relevant benchmarks. The DWQI score (from 0 to 100) classifies the water quality in five categories as poor (0–54.9), marginal (55.0–69.9), fair (70.0–84.9), good (85.0–94.9) and excellent (95.0–100). Based on the DWQI, the temporal changes of the rural drinking source water quality were not significant; while the spatial variations of the water quality were considerable across the province, so the DWQI scores in the northern counties were higher than that in the southern ones. At the county level, the highest and lowest average scores of the DWQI (±standard deviation: SD) were observed in Izeh and Shadegan to be 90 ± 5 and 69 ± 10, respectively. Based on the DWQI, proportions of the drinking water sources with the excellent, good, fair, marginal and poor qualities were determined to be 6.7, 59.1, 26.2, 7.8 and 0.1%, respectively. Turbidity and Ryznar Index (RI) were introduced respectively as the health-based and esthetic parameters with the most violations (22.7 and 63.2%, respectively). The results of the case study and sensitivity analysis indicated that the DWQI is a simple, flexible, stable and reliable index and could be used as an effective tool to characterize drinking source water quality.     

River quality analysis using fuzzy water quality index: Ribeira do Iguape river watershed, Brazil

Intrinsic uncertainties and subjectivities of environmental problems have been increasingly dealt by using computation methods based on artificial intelligence. In order to evaluate this tool's applicability, this study proposed the creation of a new water quality index based on fuzzy logic, the fuzzy water quality index (FWQI). The performance of the index proposed in the present work is assessed through a comparison with several water quality indices (WQIs) suggested in the literature, using data from hydrographic surveys of the Ribeira de Iguape River, in the southwestern part do São Paulo State, Brazil, from 2004 to 2006. The index was reasonably close to the other indices and showed a good correlation with the WQI traditionally calculated in Brazil. This new index may also be used as an alternative tool for decision-making in environmental management.     

Water quality assessment of Tal Chhapar Wildlife Sanctuary using water quality index (CCME WQI)

The present study was undertaken from June 2015 to May 2017 in Tal Chhapar Wildlife Sanctuary (TWS), Churu, Rajasthan that represents one of the unique and important grassland ecosystems in the Thar desert of India but has not been assessed ecologically. In this work the water quality assessment of the area is carried out in terms of physicochemical parameters and water quality index to fill this gap. The surface water samples were collected from the water surface with two replicates per sampling occasion for the summer, monsoon, and post-monsoon seasons. The physicochemical analysis for eight parameters were carried out following prescribed methods, viz., pH-by pH meter, total dissolved solids (TDS) -gravimetric analysis and filtration, chloride- silver nitrate titration, sulphate- turbidimetric, phosphate-stannous chloride, nitrate-brucine, calcium- EDTA titration, and iron- calorimetric methods. The relationship between the parameters was analyzed using Pearson's correlation analysis, and the Canadian Council of Ministers of the Environment Water Quality Index (CCME WQI) was calculated from these parameters. The study revealed water to be slightly alkaline (7.27–7.63) in the area. Most of the physicochemical parameters of water were found to be within the acceptable limits of the Bureau of Indian Standards (BIS) except for TDS and phosphate. The TDS showed a very strong to moderate correlation with chloride (r = 0.97), iron (r = 0.79), sulphate (r = 0.58), and calcium (r = 0.52) that revealed these ions were the major components in the makeup of the dissolved solids in the water sample. The CCME WQI indicated the water quality was fair and suitable for drinking purposes for wildlife in the area. In absence of any such prior study in the area, the overall findings of the present work is highly significant that can be used by the management authorities for future environmental monitoring and holistic development of the area.     

Water quality index,Labeo rohita,and Eichhornia crassipes: Suitable bio-indicators of river water pollution

The present study investigated the water quality index (WQI) of the Kshipra river at Dewas, Madhya Pradesh, India, using native fish Labeo rohita, and plant Eichhornia crassipes. The temperature, pH, dissolved oxygen, alkalinity, turbidity, and dissolved solids were found to be within the prescribed limits. However, heavy metals concentration exceeded the limit except for Cu and Zn. Their occurrence in river water was as follows: Ni > Fe > Cd > Cr > Mn > Zn > Cu. Among these heavy metals, Cd was found to be highly bioavailable, whereas Zn was the least bioavailable metal. Based on WQI, the water was found to be unfit for drinking, and the high WQI value was due to the presence of Cr and Cd. In fish tissues (muscle, liver, gut, gills, and kidney), the highest and lowest metal pollution index was found in gills (45.03) and kidneys (12.21), respectively. Bioaccumulation of these metals resulted in significant depletion of energy reserves (protein, glucose, and glycogen) and also altered hematological parameters. Moreover, liver function tests showed hepatic damage in the exposed fish. In-plant, both the bioaccumulation and mobility factor exceeded 1 for all these metals. On the other hand, the translocation factor was found to be beyond 1 for Fe, Ni, and Zn. These high values make this plant fit for phytoextraction of Mn, Fe, Cu, Zn, and Cd and phytostabilization of Cr in water. Moreover, consumption of L. rohita from the Kshipra River does not pose a non-cancer risk as the target hazard quotient was below 1, but it may pose cancer risk because of the presence of Cr in the range of 1.402 × 10^?3 to 1.599 × 10^?3.     

Fuzzy evaluation of water quality classification

Traditional classification methods of the water quality parameters use crisp set, and the concentrations values which are close or far from the limits are considered in same classes. Moreover, usually, several parameters are considered in quality determination; therefore, differences of the classes of the parameters may be vagueness, especially, in public consideration.In this study, an index model for quality evaluation of surface water quality classification using fuzzy logic is proposed. In the method, traditional quality classes are transformed into continuous form and then the concentration values of the different quality parameters are summed using fuzzy rules, finally, defuzzyfication of this summed values develops the index. An application of this proposed index model for physical and inorganic chemical parameters in the Eber Lake water (in Turkey) are studied to demonstrate the practical application and feasibility of this index.     

Macroinvertebrates as bioindicators of water quality in the Mkondoa River,Tanzania, in an agricultural area

The suitability of using macroinvertebrates as bioindicators of stream water quality was tested in the Mkondoa River in an agricultural area at Kilosa, using the rapid bioassessment protocol. The family biotic index (FBI) showed marked variation in water quality along the stream from values ranging from 4.1 to 5.0 in the upstream reaches, indicating good water quality, 5.3 to 5.5 in the mid-reaches and 6.0 to 6.5 in the lower reaches. The water quality index (WQI) indicated that water quality was fair (77 ± 0.98) in the upstream reach of the Mkondoa, marginal (55 ± 0.86) in the midstream reach and poor (33 ± 0.45) in the downstream reach. There were significant relationships between biological oxygen demand and dissolved oxygen and the occurrence of specific taxa, mainly Chironomus and Caenis. Significant changes in macroinvertebrate abundance were mostly related to changes in water quality. As in other parts of the world, macroinvertebrate communities proved to be good biological indicators of water quality and they should be used as bioindicators in long-term monitoring of this river.     

Physico-chemical and Water Quality Index analysis of the Okhuaihe River,Edo State,Nigeria

The water quality of the Okhuaihe River, Edo State, Nigeria was investigated from February to June 2016 to determine its suitability for drinking and other domestic purposes. Water samples collected from three stations were tested for fifteen physico-chemical parameters using standard analytical procedures. Biochemical oxygen demand and sodium were significantly different across the three stations. Except for calcium and iron, all other parameters were within the permissible limits recommended by the Nigerian Standard for Drinking Water Quality (NSDWQ) and World Health Organization (WHO). Water Quality Index (WQI) values ranged from 9.17 to 10.40, indicating excellent water quality. Although the quality of the water from the Okhuaihe River is suitable for drinking and domestic usage, regular monitoring of human activities along the water front and control of effluents discharged into the river is recommended to sustain and improve water quality.     

Water quality assessment of the Siluko River,southern Nigeria

The water quality of the Siluko River, Edo State, Nigeria was investigated from March to August 2015 to determine its suitability for drinking and usage for domestic purposes. Water samples collected from three stations were tested for thirteen physico-chemical parameters using standard analytical procedures. Temperature, phosphate and chloride were significantly different across the three stations. All other parameters, with the exception of turbidity, dissolved oxygen and phosphate, were within the permissible limits recommended by the Nigerian Standard for Drinking Water Quality (NSDWQ) and World Health Organization (WHO). Water Quality Index (WQI) values ranged from 11.24 to 16.15, indicating excellent water quality. While the quality of the water from the Siluko River is suitable for drinking and domestic usage, to prevent future deterioration of the water, it is recommended that the regulating authorities monitor effluents discharged into the river from human activities.     

两类水质综合评价方法的特点及其在河流水环境管理中的作用

河流水质恶化已成为严峻的环境问题,针对河流开展水质综合评价对河流水环境管理具有重要意义。依据不同的评价目标,选择合理的综合评价的评估标准成为河流水质评价中重要的问题之一。通过基于期望值和阈值的水质健康综合评估法(ETI)和水质质量指数(WQI)两种水质综合评价方法对"引滦入津"工程重要水源地伊逊河水质进行评价,结果显示:1)伊逊河水质ETI评估结果为良好等级,WQI评估结果为一般等级;2)伊逊河采样点水质在ETI评价中分布于4个等级,WQI仅分布于2个等级;3)伊逊河自上游至下游水质显著降低,特别是ETI评估中由优秀等级转变为差等级;4)ETI和WQI评估结果显示极显著相关性(R=0.951,P0.01);5)通过逐步多元回归,ETI评估结果的主导因子是DO、EC、SS、BOD_5和TP(P0.05),WQI评估结果的主导因子是DO、SS、BOD_5、TP、TN和NH_3-N(P0.05)。进一步分析表明伊逊河水质恶化与其流域内土地利用情况密切相关。在河流水环境管理中,ETI作为一种水质相对值评估方法,能更好体现流域内水质差异的区分度,便于管理者迅速定位流域内亟需治理的河流或河段,同时能够根据河流自身特征制定管理目标,可作为河流管理绩效评估的有效手段;而WQI作为一种水质绝对值评估方法,更适用于河流水质时间变化评估,对河流经长期治理后的管理效果评价起到重要作用。     

Water quality index as a simple indicator of aquaculture effects on aquatic bodies

This paper proposes a water quality index (WQI) to subsidize management actions in the Médio Paranapanema Watershed in São Paulo State, Brazil, as a simple pollution indicator for aquaculture activity. Water quality of the Macuco and Queixada rivers was investigated for 2 years (from May 2003 to May 2005). The index proposed in this work is composed of three measurable environmental parameters—turbidity, total phosphorus and dissolved oxygen. Concentrations of these three variables were normalized on a scale from 0 to 100 and translated into statements of water quality (excellent, good, regular, fair and poor). The index was applied to seventeen monitoring points in the aquatic bodies described above and compared to others, one being that used by the Environmental Protection Agency of United States and proposed for the National Sanitation Foundation, other employing minimal index and the last one considering the minimum operator concept. The results show that the degradation in this watershed from aquaculture activity can be easily inferred with this index, which is more restricted than the others routinely used to infer water quality.     

Evaluation of potable groundwater zones identification based on WQI and GIS techniques in Adyar River basin,Chennai, Tamilnadu,India

The main objective of this study is to identify the potable groundwater zones in Adyar River Basin (ARB) that forms the major river of Chennai metropolitan and significantly contributes to the demands of this big city's water supply. Twenty eight groundwater samples were collected during postmonsoon and premonsoon seasons in 2016 from the wells of ARB which is downstream of Chembarambakkam Lake, which supplies drinking water to Chennai metropolitan city. All the water samples were analyzed using Portable meter and Ion Chromatography for physico-chemical parameters and major ions such as pH, TDS, Ca, Mg, Na, K, Cl, HCO₃, SO₄ and NO₃. The analytical results were compared with the WHO, USEPA & BIS guideline values and reported that some of the samples exceeds these guideline values for drinking water quality. Spatial distribution maps were prepared to identify the potable groundwater available regions based on these water quality parameters. Piper and Gibbs plots are generated to identify the nature and type of groundwater with processes controls the groundwater chemistry. Principal component analysis was done to interpret the possible sources of chemical compounds present in the groundwater. To precisely delineate the potable groundwater region in ARB, Water Quality Index (WQI) approach is employed with the basic water quality parameters and spatial distribution maps were prepared using GIS for the obtained indexes. It is found that only 10.71% and 17.86% of the study area groundwater is within the excellent water quality for drinking during postmonsoon and premonsoon respectively, whereas 42.86% in postmonsoon and 14.29% in premonsoon is found as poor quality groundwater for drinking. The groundwater of the northwestern and western part of ARB is under very poor and unsuitable category for drinking in both the seasons. This region of ARB is recommended for implementation of artificial groundwater recharging to improve the groundwater quality and make it suitable for drinking.     

A dynamic water quality index model based on functional data analysis

A water quality index (WQI) incorporates two shortcomings in the dynamic assessment of water quality, namely: (1) the sampling time series must be identical for each indicator and no missing data should occur, and (2) stationary weights cannot represent the changes in the pollutant importance. To solve these problems, the present study introduces the functional data analysis method into WQI research and establishes a dynamic WQI (D-WQI) model. D-WQI is a generalization of the conventional WQI. In the D-WQI model, the changes of water quality and pollutant importance are represented in the form of dynamic functional curves. The generation methods of the concentration curves, sub-index curves, dynamic weight curves, and WQI curves are discussed. As an illustration, the D-WQI model is applied in the water quality assessment of the Changjiang River in Sanjiangying in 2012. Result shows that the river can be classified as II (good) throughout the year, which can satisfy the requirement of the Chinese South-to-North Water Diversion Project.     

Dynamic Quality Index for agricultural soils based on fuzzy logic

The increasing number of successful applications of fuzzy logic and fuzzy sets theory to dealing with the uncertainty, imprecision and subjectivity inherent to environmental quality assessments, and the recent development of new procedures based on fuzzy logic for the design of environmental quality indexes open new ways to carry out more rigorous and realistic estimations of soil quality. With these considerations in mind, the aim of this work is to design an index based on fuzzy logic, which is especially addressed to assess the dynamic quality of agricultural soils – Soil Dynamic Quality Index (S-DQI). This index is described by a group of three indexes (S-DQI_PHYS, S-DQI_CHEM, S-DQI_BIOL), each one designed to evaluate the dynamic quality of agricultural soils with regard to their physical, chemical and biological characteristics, respectively. Each index is determined from the joint opinion of a panel of experts, which decides: (i) the attributes or properties of soil which determine its dynamic quality for farming; (ii) the most suitable indicator for quantifying each of them; (iii) the influence of the values taken by these indicators on the quality of agricultural soils, which is expressed by means of membership functions, and (iv) the relative importance of the attributes in the respective index, which is expressed by means of normalized priority vectors. The value of each of these indexes is finally obtained as a result of a fuzzy inference procedure, which is a crisp value ranging from 0 to 1. This procedure allows us to express the values taken by the indicators in a particular agroecosystem by means of both crisp values and fuzzy numbers, the latter being frequently a more rigorous and realistic way of representing the estimations of the soil properties in any emplacement. Verification tests show the satisfactory response capability of the index to changes in the soil properties. The use of the designed S-DQI for routine monitoring of the quality of farming soil allows the estimation of the changes induced in the soil due to use, which is helpful to assess systematically the sustainability of the agricultural practices.     

Assessing water quality and classifying trophic status for scientifically based managing the water resources of the Lake Timsah,the lake with salinity stratification along the Suez Canal

Lake Timsah is considered as the biggest water body at Ismailia City with a surface area of 14?km². It is a saline shallow water basin lies approximately mid-way between the south city of Suez and the north city of Port Said at 30^o35′46.55“N and 32^o19′30.54″E. Because it receives water with high and low salinities, salinity stratification is producing in the Lake Timsah, with values of 14–40‰ for the surface water and over 40‰ for the bottom water. The temperature of the lake water decreased to below 19 °C in the winter and rose to above 29?°C in the summer; the concentration of dissolved oxygen ranged between 6.5 and 12.2?l^?1 and the pH fluctuated between 7.9 in its lower value and 8.2 in its higher value. Water transparency was very low as indicated by Secchi disc readings recorded during this study and varied between 0.3 and 2.7?m. The main chemical nutrient (phosphorus) reached its highest levels of 96?µg?l^?1 in winter and their lowest values of 24?µg?l^?1 during summer. This nutrient concentration is high especially by comparing with those of unpolluted marine waters, but is typical of the more eutrophic coastal waters worldwide. The composition and abundance of phytoplankton with dominancy of diatoms and increased population density (20,986 cell l^?1) reflect the eutrophic condition of the lake. The intensive growth of phytoplankton was enriched by high concentration of chlorophyll a with annual values ranged between 6.5 and 56?µg?l^?1. The objective of the present work was quantitative assessment of the quality of the water of the Lake Timsah using different approaches. During the present study, three different approaches were applied for the quantitative assessment of Lake Timsah water quality: the trophic state index (TST); trophic level index (TLI) and water quality index (WQI). Application of the trophic state and trophic level indices (TSI & TLI) revealed that the Lake Timsah has trophic indices of 60 and 5.2 for TSI and TLI, respectively. Both indices reflected the eutrophic condition of the lake waters and confirmed that the eutrophication is a major threat in the Lake Timsah. On the other hand, the WQI calculated for the Lake Timsah during the present study with an average of 49 demonstrated that the water of the Lake Timsah is bad and unsuitable for main and/or several uses. Moreover, WQI allows accounting for several water resource uses and can serve a more robust than TSI and/or TLI and can be used effectively as a comprehensive tool for water quality quantification. In conclusion, the three subjective indices used for the assessment process for the lake water are more suitable and effective for needs of the sustainable water resources protection and management of the Lake Timsah.     

Comparative study of ecological indices for assessing human-induced disturbance in coastal wetlands of the Laurentian Great Lakes

Several ecological indices have been developed to evaluate the wetland quality in the Laurentian Great Lakes. One index, the water quality index (WQI) can be widely applied to wetlands and produces accurate measurements of wetland condition. The WQI measures the degree of water quality degradation as a result of nutrient enrichment and road runoff. The wetland fish index (WFI), wetland zooplankton index (WZI), and the wetland macrophyte index (WMI), are all derived from the statistical relationships of biotic communities along a gradient of deteriorating water quality. Compared to the WQI, these indices are less labor-intensive, cost less, and have the potential to produce immediate results. We tested the relative sensitivity of each biotic index for 32 Great Lakes wetlands relative to the WQI and to each other. The WMI (r² = 0.84) and WFI (r² = 0.75) had significant positive relationships (P < 0.0001) with the WQI in a linear and polynomial fashion. Slopes of the WMI and WFI were similar when comparing the polynomial regressions (ANCOVA; P = 0.117) but intercepts were significantly different (P = 0.004). The WZI had a positive relationship with the WQI in degraded wetlands and a negative relationship in minimally impacted wetlands. The strengths and weaknesses of each index can be explained by the interactions among fish, zooplankton, aquatic plants and water chemistry. The distribution of different species indicative of low and high quality in each index provides insight into the relative wetland community composition in different parts of the Great Lakes and helps to explain the differences in index scores when different organisms are used. Our findings suggest that the WMI and WFI produce comparable results but the WZI should not be used in the minimally impacted wetlands without further study.     

Assessment of water quality and health risks for toxic trace elements in urban Phewa and remote Gosainkunda lakes,Nepal

The concentration of 13 metals (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Cd, Pb, and Hg) and their associated health risk assessment was performed for two Himalayan lakes, urban Phewa and remote Gosainkunda, from Nepal. Water Quality Index (WQI), Metal Index (MI), Hazard Quotient (HQ), Hazard Index, and Cancer Risk were calculated in order to evaluate the water quality of these lakes. Correlation analysis revealed that Mn and Fe were derived from natural geological weathering processes and Pb, V, Cr, Co, Ni, Cu, Zn, and Cd might have originated from anthropogenic sources. The results revealed that WQI of the remote lake fell into excellent water quality and urban lake fell into poor water quality, which is also supported by the MI calculation. Moreover, the HQ of Mn in urban lake showed values greater than unity suggesting its health risk to the local inhabitants. The cancer index values indicated “high” risk due to Cr, whereas Cd possesses “very low” cancer risk on local population residing nearby areas. This study provides the useful database and suggests for the regular assessment and policy formulation for safeguarding the natural water bodies in the region.     

Assessing environmental conditions of the Río Champotón (México) using diverse indices and biomarkers in the fish Astyanax aeneus (Günther, 1860)

The upper reaches of the Río Champotón in southwestern Mexico are largely unknown to science. This river is sustaining anthropogenic and natural disturbances by deforestation, substitution of natural vegetation, and agricultural non-point source pollution. Furthermore, hurricanes provoke flooding of these areas, exposing the aquatic biota to pollutants. Several approaches were used to assess the effects of environmental conditions along the freshwater portion of the Río Champotón in the native fish Astyanax aeneus and to determine the feasibility of extrapolating responses between levels of organization, and to link spatial and seasonal fish responses with water quality features. A water quality index (WQI) was employed as an indicator of environmental conditions, a set of sub-organismal biomarkers in A. aeneus (lipid peroxidation, glutathione S-transferase, ethoxyresorufin-O-deethylase and lactate dehydrogenase) was monitored to determine the integrated biomarker response (IBR), and somatic indices (individual and population-level responses; gonadosomatic, hepatosomatic, and condition factor) were characterized. Canonical correspondence analysis revealed spatial and seasonal variations in all the approaches. The dry and the wet season (April and July) exhibited low WQI scores, but decreased hardness and conductivity values as well as increased WQI values occurred during the post-hurricane season when crop fields adjacent to the riverbed were inundated. Although the WQI suggested low levels of contamination, the biomarkers did not remain static; wide fluctuations reflected fish exposure to seasonal stressors that provoked impairments in biological responses. All biomarker values were high, mainly in the post-hurricane season (November). The IBR exhibited two peaks that may be related to stress periods (April and November), with decreasing post-stress values suggesting the existence of homeostatic processes in the fish. The somatic indices reflected some seasonal and spatial differences at the population level – the gonadosomatic and hepatosomatic indices peaked in the middle of July and November, respectively – but the condition factor remained constant among sites and study periods. Future studies are needed to explore the link between the fish biomarker responses and possible causal stressors (natural or anthropogenic).