Reservoir Water Quality Research Articles

Spatio-Temporal Dynamics in Physico-Chemical Properties, Phytoplankton and Bacterial Diversity as an Indication of the Bovan Reservoir Water Quality

The study aimed to investigate the physico-chemical properties as well as phytoplankton and bacterial community diversity of Bovan Lake reservoir in Serbia to gain insight into the seasonal dynamic of water quality. All analyses were performed at three localities and water depths in spring, summer, autumn, and winter 2019. Seven phytoplankton phyla comprising 139 taxa were detected at all three localities (Chlorophyta 58%, Bacillariophyta 14%, Cyanobacteria 9%, Chrysophyta 5%, Dinophyta 5%, Euglenophyta 5%, and Cryptophyta 4%). Winter 2019 was characterized by the presence of 36 unique species in all phyla except Euglenophyta. Bacterial diversity analyses showed that Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, and Verrucomicrobia dominated the water intake locality at all three water depths (0.5, 10, and 20 m below the surface). In general, the physico-chemical parameters, phytoplankton, and bacterial community composition depended on the season and the water depth and showed that Bovan Lake was of satisfactory ecological status and water quality at all localities, and meets the needs for all intended purposes.

Introduction of manual on water quality of dam reservoir.

Introduction of manual on water quality of dam reservoir.

Інтерактивна система моніторингу поверхневих вод технологіями IoT

The article considers the possibility and priority of using the Internet of Things, especially its implementation in the surface water monitoring system. The feasibility of developing a complex system of interactive monitoring of surface water using IoT technologies has been substantiated, such a system will significantly improve water monitoring in real-time and ensure the gradual implementation of new sensor capabilities, such as collecting data on the deviation of parameters from the specified normative indicators of water quality in natural reservoirs. An interactive system for intelligent monitoring of water quality in natural reservoirs using Internet of Things technologies and tools has been developed, among others, the Node MCU 1.0 Wi-Fi microcontroller based on the ESP8266 microcontroller was used, as well as PH4502s analog sensor, the DHT-11 water and environmental temperature sensor, the DFRobot water turbidity and signal conversion board V2. The results were displayed on a 2.2- inch QVGA TFT LCD. The microcontroller unit (MCU) is connected to the sensors and further processing is performed on the server unit. The choice of a cloud server was justified, and the transfer of received data was transferred to the cloud using IoT-based ThingSpeak open-source software for water quality monitoring. The computer design environment Autodesk was used to increase the efficiency of design, in particular, the arrangement of elements, ensuring functionality, and ergonomics. The software and hardware of the device were designed with open-source software Fritzing and Arduino (IDE). Based on the obtained statistical data about the quality of water in natural reservoirs, a modern network of smart devices was implemented, such a network is a monitoring and notification system, which considers the linking of data to the time and place of positioning. Features of obtaining data on the results of water quality monitoring in natural reservoirs in real time for consumers were presented, with such monitoring, it is possible to predict and take the necessary measures to prevent possible negative impacts.

Hybrid Control Architecture of an Unmanned Surface Vehicle Used for Water Quality Monitoring

The study of water quality in reservoirs, lakes, and coasts is an activity that mainly uses human-crewed marine vehicles to obtain site parameters such as temperature, conductivity, salinity, pH, and others. This task is facilitated by unmanned vehicles, which improve data quality in hazardous areas and minimize human exposure. This work presents a novel methodology based on systems engineering concepts and hybrid control architecture for a catamaran-class unmanned surface vehicle (USV) named EDSON-J, for remote water quality monitoring activities with payload instrumentation. Critical aspects of the project development are considered, such as requirements, risk management, design flexibility, logical decomposition, functional classification, verification, integration and validation, and technological plan. The applied methodology proposes the main components for the vehicle, a main computer running robotic operating system (ROS) with deliberative control architecture for high-level tasks and a secondary computer running finite state machine (FSM) with hierarchical control architecture for low-level tasks, executing control and navigation algorithms. The results are given through missions of water quality monitoring, attaching a multiparameter payload sonde. Manual and automatic mode controls are suitable for circular and zig-zag maneuvers and show better performance for the proposed platform, guaranteeing the specifications and requirements of the vehicle design and validating the proposed hybrid control architecture.

Eutrophication risk assessment of a large reservoir in the Brazilian semiarid region under climate change scenarios.

The present study assesses the risk of eutrophication of a large semiarid reservoir under SSP2-4.5 and SSP5-8.5 scenarios for three future periods and different conditions of influent total phosphorus (TP) concentration and reservoir withdrawal. An integrated approach coupling climate, hydrological and water quality models was proposed for forecasting the climate change impacts on the trophic condition of the reservoir. The projected TP concentrations were organized as probability-based cumulative distribution functions to quantify the risk of eutrophication. The results indicated changes of eutrophication status in the three future periods, with the end of the 21st century experiencing the highest impacts on water quality. On the other hand, major reductions both in the inlet TP concentration and the reservoir withdrawal are necessary to significantly improve the trophic status and minimize the risk of eutrophication. The results also showed that the dry period is more susceptible to eutrophication than the rainy period, suggesting that tropical semiarid reservoirs are more vulnerable to eutrophication under climate change than reservoirs in other regions of the world. The proposed approach and model results are important to better understand the impact of climate change on reservoir water quality and improve water resources management in tropical semiarid regions.

Aportes naturais e antrópicos de nutrientes em bacias hidrográficas de reservatórios do semiárido brasileiro

Abstract: Aim Estimate the input of loads of N and P emitted by natural (atmospheric deposition and soil denudation) and anthropogenic (agriculture, livestock and sewage) factors for the hydrographic basins of two reservoirs in the Brazilian semiarid region (Mendubim and Umari). Methods In the present work, we use georeferenced data provided by official agencies, data presented in academic papers, field samples and laboratory analysis of emission factors in the estimates of nitrogen and phosphorus inputs in reservoir basins of Brazilian semiarid region. Results Soil denudation was identified as the main natural source of N and atmospheric deposition as the main source of P in both basins. Among the anthropogenic sources, the main source of N and P, for the two basins, was livestock. The total loads (natural and anthropogenic) of N (579.01 tonne. year-1) and P (136.35 tonne. year-1) received by the Umari basin was, respectively, 43.90% and 22.10% higher than those received by Mendubim, with a predominance of anthropogenic sources in both nitrogen and phosphorus emission. Conclusions The results showed the importance of monitoring human activities that can enhance nutrient inputs, such as nitrogen and phosphorus, in basins of the Brazilian semiarid region. The quantification of the emission factors analyzed here can be a tool in the development of strategies to mitigate the problems that high concentrations of N and P can bring to the quality and use of water in semiarid reservoirs.

Modeling the Effect of Climate Change Scenarios on Water Quality for Tropical Reservoirs: A Case Study in Mexico

Modeling the Effect of Climate Change Scenarios on Water Quality for Tropical Reservoirs: A Case Study in Mexico

The Influence and Implications of Climate Change on Water Quality in a Large Water Reservoir in the Southwest, USA

Maintaining water quality in large reservoirs is crucial to ensure continued delivery of high-quality water to consumers for municipal and agricultural needs. Lake Mead, a large reservoir in the desert southwest, USA, is projected to be affected by both loss of volume and rising air temperatures through the end of the 21st century. In this study, reductions in lake volume, coupled with downscaled climate projections for rising air temperatures through the end of the 21st century, are incorporated into the 3D hydrodynamic and water quality model for Lake Mead. If current management practices continue in the future, simulations indicate water temperatures will increase in all scenarios and could increase by as much 2℃ under the most pessimistic scenarios, but nutrient loads would not increase to concerning levels. Releases from the dam to downstream users are projected to be much warmer, and warmer water temperatures and significant dissolved oxygen in the water column are expected to cause challenges for ecosystem and recreation in the future. Surprisingly, during the Winter and Autumn, retention of heat in Lake Mead is more pronounced at higher surface elevations than the lower elevations as expected. The effects of these projections on the lake water quality and consequently, lake management decisions, are discussed.

An Assessment of Water Quality Parameters at the Cerrillos Reservoir, Ponce, Puerto Rico in the Aftermath of Hurricane Maria

Maintaining the water quality of lakes and reservoirs is part of the 2030 Agenda for Sustainable Development, an initiative promoted by the United Nations, including anthropogenic and natural factors that may influence water quality. The water reservoirs of Puerto Rico were built in watersheds to provide runoff control and for primary uses. The Cerrillos Reservoir is one of the largest water reservoirs in southern Puerto Rico, and is used as a source of potable water and for recreational activities. After hurricane Maria, in September 2017, many communities were without public water service and have obtained their drinking water from local rivers or their tributaries, without filtration or purification treatment. This research explored the physical-chemical parameters of Cerrillos Reservoir’s surface water from May 2018 to January 2019. The objective of the present study is to assess seasonal variations in surface water quality with respect to physical (temperature, turbidity, and conductivity), chemical (nutrient concentrations: (Phosphorus (P) (Soluble Reactive Phosphorus, phosphate, or orthophosphate) and Nitrogen (N) (nitrate, nitrite, and ammonia)), pH, and dissolved oxygen), and biological (total coliforms and Escherichia coli) parameters. Results suggest that Cerrillos Reservoir did not exceed the parameters of temperature, turbidity, conductivity, pH and DO, established by the Puerto Rico Department of Natural and Environmental Resources (PRDNER). The reservoir showed a stable trophic state in relation to inorganic phosphorus and nitrogen as N and P concentrations did not increase sufficiently to disrupt this ecosystem. However, total coliforms exceeded the maximum parameter (23 MPN/100mL - 994 MPN/100mL) established for the Puerto Rico Department of Natural and Environmental Resources and are likely to be the results of the disruption caused by hurricane Maria.

Structural evolution of soil aggregates in a karst rocky desertification area.

Desertification and karst landforms are widespread in the water source area of the middle route project of south-to-north water diversion in China. Soil erosion processes directly influence water quality in the water source area and contribute sediments to the bottom of the water reservoir. This study investigates soil evolution over time by sampling a slope surface and discusses associated changes in soil structure, physical and chemical properties, and mineral associations. Changes in soil aggregate structures with slope surface direction and mineral association evolution are observed. The compositions of the main soil minerals and elements are determined using scanning electron microscopy, and X-ray energy spectrum and X-ray diffraction analyses. The results reveal that (1) the evolution of soil aggregates is consistent with evolutionary trends in soil elements and mineral associations. (2) The ultra-microstructure of soil aggregate indicates the soil development stage and condition, while mineral associations indicate the soil development stage along the soil chronosequence. This study increases the understanding of land surface processes in the study area and the soil development, forming and biogeochemical processes in karst rocky desertification areas.

Analysis of physicochemical parameters and selected potentially toxic elements to assess the water quality of Kattakaduwa reservoir in Hambanthota district, Sri Lanka

Ruhuna Journal of Science (RJS) is a multidisciplinary Science Journal published by the Faculty of Science, University of Ruhuna. It welcomes articles resulting from original research work covering many areas in Pure and Applied Sciences, and Technology, and scientific articles with interdisciplinary focus.Ruhuna Journal of Science is indexed in Web of Science (Master Journal List/ Zoological Records), and included on DOAJ and World Catalogue of Scientific Journals (WCOSJ).To submit your manuscript please go to http://rjs.ruh.ac.lk/index.php/rjs/index

Peculiarities of formation of water quality of surface sources of water supply as a factor of a choice of a method of water treatment

The current state and formation of water quality in reservoirs that serve as sources of drinking water supply were considered. It was revealed that phytoplankton becomes one of the main factors influencing the formation of water quality in reservoirs in the warm period from June to November, especially during the period of reservoirs “blooming”. Mostly these processes are triggered by the explosive development of blue-green algae (cyanobacteria). The factors accompanying this phenomenon are shown. The characteristic of the influence of global climate change and new composition of wastewater on water quality in surface water supply sources is given. If earlier the sewage contained significant volumes of heavy metals, oil products, phenols, etc., now they are observed to decrease at several times and vice versa - an increase in the volume of biogenic compounds, especially phosphates is observed. The emergence of phosphates is caused both by the ingress of phosphate fertilizers into water bodies, and by household reasons - the massive distribution of phosphate-based detergents and the inability of existing sewage treatment plants to efficiently process them. Screening monitoring of the Dnieper river basin showed extremely high levels of the predicted safe concentration of herbicides, insecticides, fungicides, as well as pharmaceutical substances such as carbomazepine, lopinavir, diclofenac, efavirenz, etc. in water.
 That is, among organic pollutants, the focus changes from classic petrochemical products to the products related to agricultural and pharmaceutical production, which, in certain concentrations, can stimulate the development of phytoplankton.
 The effective methods for treating surface water in modern conditions are as follows:
 - physical retention of coarse fractions of phytoplankton using new designs of water intake structures;
 - the use of new filter materials that effectively trap finely dispersed phytoplankton fractions at the main treatment facilities and are capable of regenerating the filter media;
 - the use of new oxidizing agents-disinfectants that do not form toxic organochlorine compounds, with preliminary extraction of phytoplankton masses;

Assessment of Water Quality Based on Trophic Status and Nutrients-Chlorophyll Empirical Models of Different Elevation Reservoirs

Water quality degradation is one of the most pressing environmental challenges in reservoirs around the world and makes the trophic status assessment of reservoirs essential for their restoration and sustainable use. The main aims of this study were to determine the spatial variations in water quality and trophic state of 204 South Korean reservoirs at different altitude levels. The results demonstrated mean total phosphorus (TP), chlorophyll-a (CHL-a), total suspended solids (TSS), organic matter indicators (chemical oxygen demand: COD; total organic carbon: TOC), water temperature (WT), and electrical conductivity (EC) remain consistently higher in the very lowland reservoirs (VLLR) than those in other altitudes, due to sedimentary or alluvial watersheds. The average TP and CHL-a levels in VLLR crossed the limit of the eutrophic water, symptomizing a moderate risk of cyanobacterial blooms. Empirical models were developed to identify critical variables controlling algal biomass and water clarity in reservoirs. The empirical analyses of all reservoir categories illustrated TP as a better predictor of CHL-a (R2 = 0.44, p < 0.01) than TN (R2 = 0.02, p < 0.05) as well as showed strong P-limitation based on TN:TP ratios. The algal productivity of VLLR (R2 = 0.61, p < 0.01) was limited by phosphorus, while highland reservoirs (HLR) were phosphorus (R2 = 0.23, p < 0.03) and light-limited (R2 = 0.31, p < 0.01). However, TSS showed a highly significant influence on water clarity compared to TP and algal CHL-a in all reservoirs. TP and TSS explained 47% and 34% of the variance in non-algal turbidity (NAT) in HLR. In contrast, the TP and TSS variances were 18% and 29% in midland reservoirs (MLR) and 32% and 20% in LLR. The trophic state index (TSI) of selected reservoirs varied between mesotrophic to eutrophic states as per TSI (TP), TSI (CHL-a), and TSI (SD). Mean TSI (CHL-a) indicated all reservoirs as eutrophic. Trophic state index deviation (TSID) assessment also complemented the phosphorus limitation characterized by the blue-green algae (BGA) domination in all reservoirs. Overall, reservoirs at varying altitudes reflect the multiplying impacts of anthropogenic factors on water quality, which can provide valuable insights into reservoir water quality management.

Climate change impact on water quality in the integrated Mahabad Dam watershed-reservoir system

Climate change, besides global warming, is expected to intensify the hydrological cycle, which can impact watershed nutrient yields and affect water quality in the receiving water bodies. The Mahabad Dam Reservoir in northwest Iran is a eutrophic reservoir due to excessive watershed nutrient input, which could be exacerbated due to climate change. In this regard, a holistic approach was employed by linking a climate model (CanESM2), watershed-scale model (SWAT), and reservoir water quality model (CE-QUAL-W2). The triple model investigates the cumulative climate change effects on hydrological parameters, watershed yields, and the reservoir’s water quality. The SDSM model downscaled the output of the climate model under moderate (RCP4.5) and extreme (RCP8.5) scenarios for the periods of 2021–2040 and 2041–2060. The impact of future climate conditions was investigated on the watershed runoff and total phosphorus (TP) load, and consequently, water quality status in the dam’s reservoir. The results of comparing future conditions (2021–2060) with observed present values under moderate to extreme climate scenarios showed a 4–7% temperature increase and a 6–11% precipitation decrease. Moreover, the SWAT model showed a 9–16% decline in streamflow and a 12–18% decline in the watershed TP load for the same comparative period. Finally, CE-QUAL-W2 model results showed a 3–8% increase in the reservoir water temperature and a 10–16% increase in TP concentration. It indicates that climate change would intensify the thermal stratification and eutrophication level in the reservoir, especially during the year’s warm months. This finding specifies an alarming condition that demands serious preventive and corrective measures.

Applicability of a Combined DAF-MF Process to Respond to Changes in Reservoir Water Quality through a Two-Year Pilot Plant Operation

The optimal operating conditions of a combined dissolved air flotation (DAF)-microfiltration (MF) process to respond to changes in raw water quality were investigated by operating a pilot plant for two years. Without DAF pre-treatment (i.e., MF alone), MF operated stably with a transmembrane pressure (TMP) increase of 0.24 kPa/d when the turbidity of raw water was low and stable (max. 13.4 NTU). However, as the raw water quality deteriorated (max. 76.9 NTU), the rate of TMP increase reached 43.5 kPa/d. When DAF pre-treatment was applied (i.e., the combined DAF-MF process), the MF process operated somewhat stably; however, the rate of TMP increase was relatively high (i.e., 0.64 kPa/d). Residual coagulants and small flocs were not efficiently separated by the DAF process, exacerbating membrane fouling. Based on the particle count analysis of the DAF effluent, the DAF process was optimised based on the coagulant dose and hydraulic loading rate. After optimisation, the rate of TMP increase for the MF process stabilised at 0.17 kPa/d. This study demonstrates that the combined DAF-MF process responded well to substantial changes in raw water quality. In addition, it was suggested that the DAF process must be optimised to avoid excessive membrane fouling.

Jatiluhur Reservoir Water Quality Analysis at Various Depths

The Jatiluhur Reservoir is an important building in West Java Province whose dams the Citarum River. The location of the Jatiluhur Reservoir, which is the most downstream of the Saguling and Cirata Reservoirs, is where domestic, industrial, and agricultural wastewater pollution is accommodated from water catchment areas so that water quality decreases. This study aims to analyze the water quality in this reservoir at various depths. The study was conducted in September 2020 at 16 sampling points at a depth of 0-8 meters. The water quality parameters analyzed were Temperature, Dissolved Residue (TDS), pH, Dissolved Oxygen (DO), Fluoride (F - ), Nitrate (NO 3 - N), Sulfate (SO 4 2- ), BOD 5 , COD, and Escherichia coli. Based on the study results, it was found that the concentrations of DO, BOD 5 and COD at the monitoring location of the Jatiluhur Reservoir did not meet the quality standards. The concentrations of DO, BOD 5 and COD respectively 1.00-3.99 mg/L; 3.10-17.00 mg/L; and 28.00-59.00 mg/L. These three parameters contribute to the decline in water quality. The status of water quality using the IP method is categorized as lightly polluted so that it affects the utilization of this reservoir, especially as raw water for drinking water. The highest level of contamination was at the floating net cages sampling location at a depth of 8 m. The decline in water quality in the Jatiluhur Reservoir is caused by organic substances originating from floating net cages waste.

Jatiluhur Reservoir Water Quality Analysis at Various Depths

The Jatiluhur Reservoir is an important building in West Java Province whose dams the Citarum River. The location of the Jatiluhur Reservoir, which is the most downstream of the Saguling and Cirata Reservoirs, is where domestic, industrial, and agricultural wastewater pollution is accommodated from water catchment areas so that water quality decreases. This study aims to analyze the water quality in this reservoir at various depths. The study was conducted in September 2020 at 16 sampling points at a depth of 0-8 meters. The water quality parameters analyzed were Temperature, Dissolved Residue (TDS), pH, Dissolved Oxygen (DO), Fluoride (F-), Nitrate (NO3-N), Sulfate (SO42-), BOD5, COD, and Escherichia coli. Based on the study results, it was found that the concentrations of DO, BOD5 and COD at the monitoring location of the Jatiluhur Reservoir did not meet the quality standards. The concentrations of DO, BOD5 and COD respectively 1.00-3.99 mg/L; 3.10-17.00 mg/L; and 28.00-59.00 mg/L. These three parameters contribute to the decline in water quality. The status of water quality using the IP method is categorized as lightly polluted so that it affects the utilization of this reservoir, especially as raw water for drinking water. The highest level of contamination was at the floating net cages sampling location at a depth of 8 m. The decline in water quality in the Jatiluhur Reservoir is caused by organic substances originating from floating net cages waste.

Long-Term Water Quality Patterns in an Estuarine Reservoir and the Functional Changes in Relations of Trophic State Variables Depending on the Construction of Serial Weirs in Upstream Reaches.

Water quality degradation is one of the major problems with artificial lakes in estuaries. Long-term spatiotemporal patterns of water quality in a South Korean estuarine reservoir were analyzed using seasonal datasets from 2002 to 2020, and some functional changes in relations of trophic state variables due to the construction of serial weirs in the upper river were also investigated. A total of 19 water quality parameters were used for the study, including indicators of organic matter, nutrients, suspended solids, water clarity, and fecal pollution. In addition, chlorophyll-a (CHL-a) was used to assess algal biomass. An empirical regression model, trophic state index deviation (TSID), and principal component analysis (PCA) were applied. Longitudinal fluctuations in nutrients, organic matter, sestonic CHL-a, and suspended solids were found along the axis of the riverine (Rz), transition (Tz), and lacustrine zones (Lz). The degradation of water quality was seasonally caused by resuspension of sediments, monsoon input due to rainfall inflow, and intensity of Asian monsoon, and was also related to intensive anthropic activities within the catchment. The empirical model and PCA showed that light availability was directly controlled by non-algal turbidity, which was a more important regulator of CHL-a than total nitrogen (TN) and total phosphorus (TP). The TSID supported our hypothesis on the non-algal turbidity. We also found that the construction of serial upper weirs influenced nutrient regime, TSS, CHL-a level, and trophic state in the estuarine reservoir, resulting in lower TP and TN but high CHL-a and high TN/TP ratios. The proportions of both dissolved color clay particles and blue-green algae in the TSID additionally increased. Overall, the long-term patterns of nutrients, suspended solids, and algal biomass changed due to seasonal runoff, turnover time, and reservoir zones along with anthropic impacts of the upper weir constructions, resulting in changes in trophic state variables and their mutual relations in the estuarine reservoir.

Hydrochemical water quality monitoring of natural water bodies of the Ural river basin

A general characteristic of the river basin of the interstate Ural river and information on the economic use of the Ural river in its upper, middle and lower reaches are given. Information on the hydrology of the liquid and solid flow of the Ural river is presented. Hydrochemical monitoring of water bodies of the Ural river basin was conducted during the flood period, during the summer low water period and during the autumn low water period of 2017–2018. The hydrochemical monitoring of the water quality in natural reservoirs of the Ural drainage basin made it possible to identify an excess of the MPCs for residential use and for fishery of heavy metal ions in the water of the examined reservoirs. An excess of cadmium ions by (1.2–1.4) MPC for residential use was found in the Ilek river during its low water as well as in the Ural river near the border with the Russian Federation during the flood period in the amount of (3.1–3.4) MPC for residential use and near the village Zharsuat in the period of summer and autumn low water in the amount of (1.5–2.6) MAC for residential use. An excessive concentration of lead ions by (1.2–1.4) of MPC for fresh water fisheries in the middle and lower reaches of the Ural river at different times of the year was found. Excessive concentrations of ions of different heavy metals in comparison with their MPC for fresh water fisheries were found in all water bodies in different periods of the year. The greatest excess of zinc ions in comparison with its MPC for fresh water fisheries was observed during low water.

Spatiotemporal Variation on Water Quality and Trophic State of a Tropical Urban Reservoir: A Case Study of the Lake Paranoá-DF, Brazil

Nutrient enrichment and eutrophication are among the main problems that lead to the deterioration of water quality in lakes and reservoirs. In this study, spatial and temporal variations in the concentrations of organic and inorganic species of nitrogen and phosphorus in the water column of Lake Paranoá-DF (Brazil) were evaluated between 2016 and 2017. Seasonality was the main factor in the variations in concentrations of the investigated parameters. Additionally, we found differences in behavior for different nutrients and other variables that indicate different main sources of each nutrient as well as different biogeochemical processes predominating in each season. For example, the electrical conductivity (EC), dissolved silicon, PO43−, and NO3− showed mean concentrations significantly higher in the rainy season, indicating greater inputs in these periods (which is in part related to increasing soil leaching and runoff). Agricultural activities were the main source of NO3− and wastewater treatment plants (WWTP) proved to be the main source of nutrients, mainly NH4+ and all forms of phosphorus. These two allochthonous sources are also the determining factors of the trophic state and the degradation of the water quality of Lake Paranoá. The lake is in the transition process from a mesotrophic to a eutrophic condition.