The environmental pollution of Kandy Lake: A case study from Sri Lanka

The water pollution levels of Kandy Lake in Sri Lanka were monitored to probe the impacts and influences of urban environment in a developing country. Although Kandy Lake is a source of drinking water for the town, it was observed that a large number of effluent channels drained in to it, carrying a continuous flow of contaminated water. The hydrogeochemistry, pH, and bacterial levels were studied using lake and drain water samples. A high coliform count and a high degree of faecal contamination was observed in all water samples obtained from the lake and drains. The Cu²⁺ and F^? concentrations were relatively low and did not reach harmful levels, but were higher than that in the background. The pH of water remained almost neutral and provided ideal conditions for bacterial growth. All laboratory and field experiments indicated eutrophic conditions in the lake and the unsuitability of water in the unpurified state for drinking purposes. The purified water had a zero coliform count, but the chlorine content added was relatively high and may also prove to be a health hazard. On the whole, the polluted water in Kandy Lake indicated the adversities of human involvements with nature and provided a good case study for human influence on water pollution in a developing country.     

Microbial pollution of the blue and white Niles at Khartoum

The total coliform and fecal coliform bacterial load of the Blue and White Niles at Khartoum has been determined in the period of January–July 1984. The Blue Nile has been found to be more contaminated than the White Nile. The east bank of the White Nile was found to be more contaminated than the west bank. The microbial load of the rivers increased conspucuously as they passed through the city of Khartoum.     

Effect of Nile River water quality on algal distribution at Cairo,Egypt

Changes of phytoplankton density and their relation to physicochemical characteristics along the Nile River have been noted in the Cairo district between 1976 and 1982. Three major phytoplankton groups were found to dominate the river Nile: green algae, blue-green algae, and diatoms. Diatoms represent the most dominant group and comprised from 42% to 96% of the phytoplankton community during the investigated period. Blue-green algae comprised from 0.7% to 48% of total cell number. Green algae represent the low percentage group, which ranges from 0.2% to 41% of Nile water algae. High species diversity (H′) was detected in green algae (1.22) followed by diatoms (0.84); the lowest diversity was in blue-green algae (0.45). The density of total phytoplankton count fluctuated between 10⁶ and 10⁷ organism/L. The concentration of chlorophyll-a ranged from 5 to 37 mg/m³. Primary production rates in the Nile River ranged from 8.5 to 52 mg O₂/m³h. Statistical analysis revealed significant positive correlations between chlorophyll-a content, and concentrations of phosphoruss and nitrate. Phytoplankton diversity, primary production, ammonia, and nitrite content revealed that there is no indication of pollution in the Nile.     

Chemical tracers as indicator of human fecal coliforms at storm water outfalls

Indicators to distinguish between fecal coliforms of human and animal origin were investigated in water from storm sewer outfalls to a coastal lake during wet and dry weather. The ratio of fecal coliform relative to fecal streptococci count was used as the microbiological indicator. Concentrations of human-activities originated caffeine, anionic surfactant, fluoride, and fluorescence whitening agent (FWA) were used as chemical indicators. The ratio of fecal coliform to fecal streptococci ranged from 0.2 to 3.0, during wet weather making it difficult to interpret the origin of fecal pollution. However, concentrations of caffeine, anionic surfactant, fluoride, and FWA in storm water outflow during wet weather were much higher than those in the lake water during dry weather, indicating the presence of human waste at storm water outfall. Strong correlation between fecal coliform counts and chemical parameter values further indicated the human contribution to the fecal coliform count. In addition, a strong correlation among the chemical parameters suggested that only one of them is needed as chemical tracer to detect the presence of human input.     

Bacterial removal by anaerobic digestion

The impact of anaerobic digestion and post composting of the digested slurry on total bacterial counts, total coliform, fecal coliform, and fecal streptococci was investigated. Anaerobic digestion removed up to 99% of the bacterial parameters; however, the residual numbers present in the digested slurry were still high. The residuals ranged from 10⁵/g to 10¹³/g for total bacterial counts, 10²/g to 10⁸/g for total coliform, 10⁴/g to 10⁸/g for fecal coliform, and 10²/g to 10⁸/g for fecal streptococci. The digested slurry was mixed with soil for one week and then for two months, but the density of bacterial parameters was not reduced. There was an increase in numbers during the two composting steps.     

Assessment of groundwater contamination in a suburban area of Chennai,Tamil Nadu,India

Groundwater source is the major source of drinking water in most of the suburban areas of India. Groundwater quality was analyzed for pH, TDS, hardness, chloride, fluoride, nitrate, ammonia, phosphate, total coliform and E. coli for the period of January–December 2013. Samples were collected from 10 locations that include 10 shallow wells and 10 deep wells in each location. The quality variation between both shallow and deep wells during pre- and post-monsoon was analyzed. The improper disposal of solid waste and the distance of septic tank were pronounced on E. coli count. The analysis reveals that groundwater contamination is influenced by seasonal changes, environmental condition of the well and maintenance of the well. The high contamination was observed in the wells which are near to the Pallikaranai marsh, and during post-monsoon season, the total dissolved solids and nitrite parameters are slightly increased, whereas chloride increases during pre-monsoon season. Correlation analysis reveals that the chloride and nitrite have a significant relation. The results suggested that the groundwater immediately needs broader protection.     

Mineral content of drinking water in lowland papua

This study presents concentration of nine minerals (Na, K, Mg, Ca, Cl, Mn, Zn, Cd, Pb) in 31 drinking water samples collected in the Papua New Guinea lowland, where coastal villagers draw water from artificial wells blended with sea water, riverside villagers utilize brackish river water, and inland villagers fetch creek or swamp water whose chemical composition is close to rain water. During the dry season, the coastal well water contains 500 mgL⁻¹ of sodium and 50–90 μgL⁻¹ of lead. The inland creek or swamp water contains very small amount of minerals; on the average, for instance, 0.64 mgL⁻¹ of magnesium, 0.84 mgL⁻¹ of calcium, and 4.78 mgL⁻¹ of water hardness (as CaCO₃). From some epidemiological evidence in industrialized countries, these mineral concentrations are judged to be indicative of high risk of cardiovascular disorders.     

Anthropogenic influence on the water quality in Guanabara Bay, Rio de Janeiro, Brazil

Guanabara Bay is a 384-km² coastal bay with 70% of the population of the metropolitan area of Rio de Janeiro located within its drainage basin. The water quality of the Bay is impacted by domestic and industrial runoff, of which only 15% has been adequately treated. However, based on a 14-year monitoring program, the water quality for most of Guanabara Bay remains acceptable because of intense tidal flushing, and we failed to find a worsening of conditions during the 14-year study. The inner shallow regions of the Bay, the western and northwestern parts, receive most of the drainage from metropolitan Rio de Janeiro. It is here that the water quality is alarmingly poor, characterized by hypertrophic conditions and occasional hypoxic events. Fecal coliform counts in these inner reaches of the Bay are 4–100 times higher than the maximum acceptable count for recreational waters. Hypertrophic conditions prevail in Guanabara Bay, which is characterized by low dissolved oxygen, high biochemical oxygen demand, peaks in fecal coliform, and extremely high chlorophyll-a concentrations, which reflect high quantities of nutrients entering the system. These anthropogenic pressures are a threat to planktonic and benthic communities and are reminiscent of San Francisco Bay 30 years ago. The Guanabara Bay water quality could be returned to pre-1950 conditions, but it would require sufficient political will and economic investment to ensure that at least 80–90% of the domestic and industrial sewage were treated adequately. Electronic Publication     

Greenhouse gas emissions from a semi-arid tropical reservoir in northeastern Brazil

We estimated carbon dioxide (CO₂) and methane (CH₄) emissions by diffusion, ebullition, and degassing in turbines from a semi-arid hydropower reservoir in northeastern Brazil. Sampling sites were allocated within the littoral and deeper waters of one embayment, the main-stream, and at turbines. Annual carbon emissions were estimated at 2.3?×?10⁵?±?7.45?×?10⁴ t C year^?1, or in CO₂-equivalents (CO₂-eq) at 1.33?×?10⁶?±?4.5?×?10⁵ t CO₂-eq year^?1. Diffusion across the water surface was the main pathway accounting for 96% of total carbon emissions. Ebullition was limited to littoral areas. A slight accumulation of CO₂, but not of CH₄, in bottom waters close to the turbines inlet led to degassing emissions about 8?×?10³ t C year^?1. Emissions in littoral areas were higher than in main-stream and contribute to 40% of the total carbon. Carbon (C) emissions per electricity generated, at 60% of installed capacity, is 0.05 t C-CO₂-eq MWh^?1. The ratio increases to 0.09 t C-CO₂ MWh^?1, equating 80% of the emissions from natural gas and 40% of diesel or coal power plants. Retention time and benthic metabolism were identified as main drivers for carbon emissions in littoral areas, while water column mixing and rapid water flow are important factors preventing CH₄ accumulation and loss by degassing. Our results indicate that Itaparica Reservoir, located in the semi-arid region of Northeastern Brazil, acts as a source of GHGs. Management measurements are needed to prevent emissions to raise in the future.     

Taxonomy of groundwater quality using multivariate and spatial analyses in the Tuticorin District,Tamil Nadu,India

A holistic appraisal of the quality of groundwater from the Tuticorin District has been conducted using multivariate statistical and spatial analyses. The objectives of the study were to delineate the spatial and temporal variabilities in groundwater quality and to understand its suitability for human uses. A total of 100 groundwater samples were collected and analyzed for major cations and anions during pre-monsoon and post-monsoon. Water quality index rating was calculated to quantify overall water quality for human consumption. The PRM samples exhibit poor quality in greater percentage when compared with POM due to the dilution after rainfall. Correlation, factor analysis, and plot of the factor scores reflect the seawater intrusion and weathering process. The mineral stability diagrams indicated that the groundwater is in equilibrium with kaolinite and Ca-montmorillonite, whereas Gibbs plot showed that the chemical composition of groundwater in both districts is controlled by the natural weathering processes irrespective of seasons. The major water type identified in this study is the Ca²⁺–Mg²⁺–HCO₃ ^? type, which degrades into predominantly Na⁺–Cl^?–SO₄ ^2? more saline groundwater toward the coast.     

Microorganisms: Indicators of pollution in integrated livestock-fish farming systems

Twelve fishponds each measuring 1,000 m² stocked with 2,000 fish consisting of 85% Oreochromis niloticus, 14% Cyprinus carpio and 1% Ophicephalus striatus were used to determine the level of fecal coliforms in the pondwater and fish flesh and the presence of Salmonella in the pondwater. Water samples for coliforms were collected at weekly intervals while those for Salmonella were done biweekly from three pond sites. Fish were randomly sampled by seining the pond over a three-month period. Both water and fish samples were analyzed for coliforms with the multiple-tube fermentation technique and for Salmonella using the swab technique. Results showed coliform counts with mean concentrations varying from 29,700/L of water in the middle of the pond to 18,100/L farthest from the manure dumping site. Differences in concentration between collection sites were not significant (P > 0.05) but mean values obtained weekly differed significantly (P < 0.05). Tilapia had coliform counts of 1.7 while carp had 1.1/g flesh. Differences among fish samples of the same species were not significant (P > 0.05) but were significant between species (P < 0.05). Biochemical tests revealed the presence of E. coli and Klebsiella sp. and more commonly S. cholerasuis.     

Radioecological consequences of radioactive discharges into the Techa River on the Southern Urals

The sources and levels of radioactive contamination of the Techa River are analyzed. Dose assessments are made for humams and biota. The highest radionuclide concentrations in the river water were observed in the period 1950–1951. In 1951, at a distance of 78 km from the site of radioactive discharges, the content of ⁹⁰Sr in the water was 2.7 × 10⁴ Bq l⁻¹ and that of ¹³⁷Cs was 7.5 × 10³ Bq l⁻¹. Subsequently, the radionuclide activity in the river water decreased considerably. In the period 1991–1994, the average annual content of ⁹⁰Sr in the water varied between 6 and 20 Bq l⁻¹. The average annual content of ¹³⁷Cs in the river water varied from 0.06 to 0.23 Bq l⁻¹, i.e. was lower than that of ⁹⁰Sr approximately by two orders of magnitude. The concentration of ^239,240Pu in the water varied between 0.004 and 0.019 Bq l⁻¹. The radioactive contamination of the Techa floodplain is highly nonuniform. With increasing distance from the river sources, the contamination density of the floodplain decreases, remaining, however, considerably higher than the background values.At present, the average annual dose rates in contaminated areas are (0.1–2) × 10⁻³ Sv year⁻¹, which is considerably lower than in the periods of ‘acute’ exposure (1950–1951). The doses to aquatic biota were much higher than those to humans.     

Monitoring and evaluation of shallow well water quality near a waste disposal site

This study identifies shallow well water contamination sources near the Mae-Hia waste disposal site and the clarification of the extent of well water contamination caused by leachate generated from the disposal site. The water of 40 shallow wells around the Mae-Hia disposal site, where three potential sources of groundwater pollution exist, was sampled and analyzed for physical, chemical, and biological characteristics. Water samples were taken every month from June 1989 to May 1990 along with a measurement of well water levels in order to estimate the groundwater flow direction. Comparison with the drinking water standards/guidelines showed that well water in the study area was not suitable for drinking due to the high contamination of total and fecal coliforms and moderate contamination by nitrate and manganese. It was found that the level of conductivity, total solids, color, chloride, chemical oxygen demand, sodium, copper, and lead in the groundwater of wells located adjacent to the disposal site were higher than in other areas. In addition, higher concentrations of sodium, chloride, calcium, and magnesium in the wells located downstream of the groundwater flow were recorded. Estimation of a leachate plume using chloride as an indicator showed that the wells located in the eastern part of the disposal site, a dominant direction of groundwater flow, were contaminated by leachate generated from the waste disposal site.     

Hydrogeomorphic variability due to dam constructions and emerging problems: a case study of Damodar River,West Bengal,India

In the first multipurpose river valley planning of India, the vast resources of Damodar River Basin (DRB) (eastern India) are not only to be envisioned in their entirety but also to be developed in a unified manner where the water, land, and people are simultaneously bounded in a seamless web. Four large dams (Konar, Tilaiya, Maithon, and Panchet), Durgapur barrage, and Tenughat reservoir are built to tamp the flood-prone Damodar River using water resource in an integrated method. The functionality of Damodar fluvial system is controlled by dams, barrage, weirs, sluices, embankments, and canals, maintaining a dynamic equilibrium between fluvial processes and anthropogenic processes. Carrying more than 50 years of legacy, the existing drainage and flood control system of Damodar Valley Corporation has aggravated a number of hydrogeomorphic problems especially in lower DRB, viz. siltation of river bed and reservoirs, uncontrolled monsoonal stream flow, declining carrying capacity of lower course, drainage congestion, low-magnitude annual floods, channel shifting, de-functioned canals, decay of paleochannels, decline of ground water level, and less replenishing of soils with fresh silts. The present paper is mainly tried to investigate the pre-dam and post-dam hydrogeomorphic variability in relation to flood risk and drawbacks of Damodar Valley Multipurpose Project. Specifically, the annual peak flow of Damodar shifts from August to September due to dam construction and reservoir storage. Applying the annual flood series of log Pearson type III distribution, we have estimated post-dam 5-year peak discharge of above 5,300 m³ s^?1 and 100-year flood of above 11,000 m³ s^?1. Due to siltation, the bankfull discharges of sample segments are gradually declined up to 4,011 m³ s^?1, 2,366 m³ s^?1, and 1,542 m³ s^?1, respectively, having recurrence interval of 1.18–3.18 years only. With the regulation of monsoon flow, the standard sinuosity index is gradually increased downstream, having high dominance of hydraulic factors in respect of topographic factors. The upstream section of study area (Rhondia to Paikpara) now shows the dominance of aggradational landforms, braiding, avulsion, high width–depth ratio, breaching of right bank, and valley widening, but downstream of Barsul the phenomena of bank erosion, confined sinuosity, low width–depth ratio, and narrowness are more pronounced.     

21,000 Years of Ethiopian African monsoon variability recorded in sediments of the western Nile deep-sea fan

The Nile delta sedimentation constitutes a continuous high-resolution record of Ethiopian African monsoon (EAM) regime intensity. Multi-proxy analyses performed on hemipelagic sediments deposited on the Nile deep-sea fan allow the quantification of the Saharan aeolian dust and the Blue/White Nile River suspended matter frequency fluctuations during the last 21,000 years. The radiogenic strontium and neodymium isotopes, clay mineralogy, elemental composition and preliminary palynological analyses reveal large changes in source components, oscillating between a dominant aeolian Saharan contribution during the Last Glacial Maximum (LGM) and the late Holocene (~4,000–2,000 years), a dominant Blue/Atbara Nile River contribution during the early Holocene (15,000–8,000 years) and a probable White Nile River contribution during the middle Holocene (8,000–4,000 years). The following main features are highlighted: (1) The rapid shift from the LGM arid conditions to the African Humid Period (AHP) started at about 15,000 years. The AHP extends until 8,000 years, and we suggest that the EAM maximum between 15,000 and 8,000 years is responsible for a larger Blue/Atbara Nile sediment load and freshwater input into the eastern Mediterranean Sea. (2) The transition between the AHP and the arid late Holocene is gradual and occurs in two main phases between 8,400–6,500 years and 6,500–3,200 years. We suggest that the main rain belt shifted southward from 8,000 to ~4,000 years and was responsible for progressively reduced sediment load and freshwater input into the eastern Mediterranean Sea. (3) The aridification along the Nile catchments occurred from ~4,000 to 2,000 years. This dry period, which culminates at 3,200 year, seems to coincide with a re-establishment of increased oceanic primary productivity in the western Mediterranean Sea. Such a pattern imposes a large and rapid northward shift of the rain belt over the Ethiopian highlands (5–15°N) since 15,000 years. Precipitation over Ethiopia increased from 15,000 to 8,000 years. It was followed by a gradual southward shift of the rain belt over the equator from 8,000 to 4,000 years and finally a large shift of the rain belt south the equator between 4,000 and 2,000 years inducing North African aridification. We postulate that the decrease in thermohaline water Mediterranean circulation could be part of a response to huge volumes of freshwater delivered principally by the Nile River from 15,000 to 8,000 years in the eastern Mediterranean.     

Cleaning the river Damodar (India): impact of COVID-19 lockdown on water quality and future rejuvenation strategies

Globally, it is established that the partial lockdown system assists to improve the health of the total environment due to inadequate anthropogenic actions in different economic sectors. The ample research on fitness of environment has been proved that the strict imposition of lockdown was the blessings of environment. The river Damodar has historical significance and lifeline for huge population of Jharkhand and West Bengal state of India but in the recent years the water quality has been deteriorated due to untreated industrial effluents and urban sewage. The main objective of this study is to examine the water quality of river Damodar during and prelockdown phase for domestic use and restoration of river ecosystem. A total of eleven (11) effluent discharge sites were selected in prelockdown and during lockdown phase. A new approach of water quality assessment, i.e., water pollution index (WPI) has been applied in this study. WPI is weightage free, unbiased method to analysis of water quality. The result shows that the physical, chemical and heavy elements were found beyond the standard limit in prelockdown period. The cation and anion were arranged in an order of Na²⁺ ?>?K⁺ ?>?Ca²⁺ ?>?Mg²⁺ and Cl^??>?So₄^??>?No₃^??>?F^? in both the sessions. WPI of prelockdown showed that about 100% water samples are of highly polluted. WPI of lockdown period showed that around 90.90% samples improved to ‘good quality’ and 9.10% of samples are of ‘moderately polluted.’ Hypothesis testing by ‘t’ test proved that there was a significant difference (ρ?=?0.05%) in values of each parameter between two periods. Null hypothesis was rejected and indicated the improvement of river water quality statistically. Spatial mapping using Arc GIS 10.4 interpolation (IDW) helps to understand spatial intensity of pollution load in two periods. This research study should be helpful for further management and spatial diagnosis of water resource of river Damodar.

     

Transport and distribution of artificial gamma-emitting radionuclides in the River Yenisei and its sediment

Discharges from the Krasnoyarsk Mining and Chemical Industrial Complex (KMCIC) near Krasnoyarsk resulted in radioactive contamination of sediments of the River Yenisei. Between 1999 and 2006, 16 sediment cores were collected at different positions 15-1500 km downstream from the discharge point. The concentration of artificial gamma-emitting radionuclides (¹³⁷Cs, ⁶⁰Co, ¹⁵²Eu, and ²⁴¹Am) was determined with the objective to analyze the migration processes leading to the transport of these radionuclides along the river and to their vertical distribution within the sediment. In cores taken in the vicinity of the reactors, the average activity concentration of ¹³⁷Cs, ¹⁵²Eu, and ⁶⁰Co was about 1000 Bq kg⁻¹, and the activity concentration of ²⁴¹Am was about 20 Bq kg⁻¹. Contamination levels of artificial radionuclides were decreasing with increasing distance downstream the KMCIC: The fastest decrease of average activity by a factor of 10 over a distance of 300 km was observed for ²⁴¹Am, whereas for ¹³⁷Cs this decrease occurred over a distance of 1100 km. Sequential extraction experiments revealed that in all depths and at all distances the studied radionuclides were tightly bound to the sediment.To investigate the mechanisms of transport of the ¹³⁷Cs and ⁶⁰Co contamination, mathematical models have been used to describe the contamination in the river water and within the sediments.     

Modelling changes in nitrogen emissions into the Oder River System 1875–1944

Studies of nutrient emissions into surface waters are usually only performed for years in recent decades. However, estimating nutrient emissions for the more distant past enables us to identify the main factors responsible for the increasing nutrient contamination since the end of the nineteenth century. We focussed on the Oder River System for 1875–1944, divided into 10-year periods. Nutrient emissions into surface waters were calculated with the model MONERIS (MOdelling Nutrient Emissions in RIver Systems). For seven different pathways and eight sources, the total nitrogen (TN) emissions were quantified. The TN-emissions into the surface waters for 1880 amounted to 25,300 t?year^?1, and by 1940, this value had almost doubled to 46,600?t?year^?1. In 1880, 57% of TN-emissions into the surface waters derived from urban systems, due to the high amount of untreated waste water. In 1940, only 34% of TN-emissions into surface waters derived from urban systems, despite a population growth of about 27% since 1880; point sources via newly constructed waste water treatment plants (WWTPs) increased from 4% (1880) to 26% (1940). During the study period, the main changes in diffuse TN-emissions from agriculture were caused by inorganic fertilizer application and nitrogen deposition, while TN-emissions via urban sources were shifted to point sources due to population growth and the construction of new WWTPs. Furthermore, estimated TN-concentrations could make a contribution to construct benchmarks for nutrient concentrations according to the physiochemical properties to implement the European Water Framework Directive (WFD 2000).     

14C and 210Pb in NE atlantic sediments: Evidence of biological reworking in the context of radioactive waste disposal

Scavenging by the seabed and by sedimentary particles in the deep ocean may have a significant effect on the removal of artificial radionuclides released to the water column as a result of radioactive waste disposal operations. Biological activity in the upper layers of the sediment column will enhance the rate of removal for those particle-reactive radionuclides with a short half-life relative to the turnover time of the upper mixed layer. For longer-lived radionuclides the rate of sediment accumulation will determine the ultimate rate of removal.The rate of sediment accumulation and extent of biological mixing of deep-sea sediment from three areas of the NE Atlantic Ocean have been investigated using ¹⁴C and ²¹⁰Pb data. Treatment of the radiocarbon with a simple box model provided estimates of sedimentation rate (ω), mixed layer depth (L), mixed layer age (T_ML) and the age of material arriving at the surface (T₀), which were broadly similar to previously published values from other ocean basins. Box cores from the Iberia Abyssal Plain, Madeira Abyssal Plain and from the NEA low-level radioactive waste dumpsite yielded sedimentation rates in the range 0.8 to 2.2 cm ky^?1 over the upper 16–25 cm. Continuous particle mixing appears to be taking place to a depth of 4 to 6 cm below the present sediment-water interface. Closely spaced vertical sampling of core 161-2 for ²¹⁰Pb allowed a biodiffusion coefficient (D_B) to be calculated (4 × 10^?9cm²s^?1), treating bioturbations as a diffusive term and sedimentations as an advective term in a simple mathematical model. In general, values of D_B in deep ocean sediments fall within the range 1–10 × 10^?9cm²s^?1, two orders of magnitude lower than nearshore values. From a review of published data it is concluded that biological mixing takes place extensively in the deep ocean; it appears to be fairly constant on a basin-wide scale and amenable to incorporation in mathematical models of radionuclide behaviour in the water column.     

Water management and aquatic ecosystem services of a tropical reservoir (Itaparica,São Francisco,Brazil)

Reservoirs have a wide variety of uses that have led to frequent conflicts over ecological conservation and contamination, especially as land management has intensified. Oligotrophication must be implemented in numerous tropical reservoirs that experience advanced eutrophication to maintain aquatic ecosystem functions. To quantify impacts on ecosystem functions and to develop an adaptive management policy, multiple studies have been conducted on the Itaparica Reservoir, São Francisco River, in the semi-arid north-eastern region of Brazil. Here, we add to that existing body of knowledge through investigating how nutrient accumulation is affected by water exchange between the main river flow and Icó-Mandantes Bay. Operational water-level fluctuations in the reservoir create large desiccated littoral areas that release high amounts of nutrients when they are rewetted. In particular, water-level variation promotes proliferation of Egeria densa, a noxious weed, thus elevating trophic levels of the Itaparica Reservoir and Icó-Mandantes Bay. Analysis with a P efficiency model determined 25 μg P L^?1 to be the critical concentration and further indicated that the critical load in both bodies of water have been exceeded. Moreover, intensive fish aquaculture using net cages has led to further overtaxing of the reservoir. We conclude that an effective ecological reservoir management policy must involve oligotrophication, harvesting of noxious water weeds for use as soil amendment in agriculture or biogas production, “blue” aquaculture, and limiting hydroelectric power production based on current water availability.