Lakes and Reservoirs: Research and Management最新文献

With increasing urbanization, urban lakes are becoming more common and serve as important flood control infrastructure, recreational uses, as well as habitat for a variety of biota. However, given their construction, function and location, urban lakes are susceptible to disturbances including stormwater runoff from metropolitan catchment areas. For example, nutrient loading from stormwater runoff can cause eutrophication. Chlorophyll-a concentration is an important water quality parameter because it is used to assess water quality and determine trophic state. Chlorophyll-a is known to be impacted by a number of environmental factors including precipitation and associated runoff. Previous studies indicate that the relationship between precipitation and chlorophyll-a is complex and often site-specific. In this study, we examined the relationship between chlorophyll-a and precipitation in an urban, tropical lake located in East Kalimantan Province, Indonesia. From October through December 2022, chlorophyll-a, turbidity, phosphate (PO₄), pH, dissolved oxygen, temperature, total dissolved solids and conductivity were measured at five sampling sites in Air Hitam Lake, and precipitation was measured adjacent to the lake. These data indicated that chlorophyll-a concentrations were negatively correlated with recent precipitation (r² = .71, p < .05). This relationship was likely a result of dilution from increased lake volume. Although urban runoff is expected to increase nutrient loading, our monitoring indicated that dilution can mediate this process in the short-term. Our findings suggest that timing matters when monitoring water quality in tropical, urban lakes. Sampling immediately following heavy precipitation and stormwater runoff can lead to an underestimation of normal chlorophyll-a concentrations due to dilution. As a result, dilution effects should be examined when studying and managing urban lentic ecosystems with strong precipitation dynamics. Further studies are necessary to better understand these urban aquatic ecosystems to continue to improve future management efforts.

Water hyacinth (Eichhornia crassipes (Mart) solms), a widely distributed invasive aquatic plant in Sri Lanka, has invaded the Diyawannawa wetland lake located in Colombo city, which is the first Ramsar wetland city in South Asia. The present study was conducted to assess the water quality parameters that influence the distribution of water hyacinth and to identify the environmental, economic, and social consequences of its invasion of the Diyawannawa wetland. Five sampling sites were selected from the Diyawannawa lake, and the water pH, temperature, conductivity, total dissolved solids (TDS), salinity, dissolved oxygen concentration (DO), nitrate concentration, and total phosphorus concentration were measured at monthly intervals in the rainy and dry seasons of 2020. The abundance of water hyacinth was recorded at each site at each sampling event. Interviews and focus group discussions (FGDs) were conducted with the representatives of the community associated with the wetland to assess the ecological, economic and social effects of water hyacinth invasion. Principal component analysis of the water quality parameters revealed that phosphorus and nitrate concentrations in water significantly influenced the abundance of water hyacinth. Further, the water quality index (WQI) indicated poor water quality in the sites invaded by water hyacinth. The interviews and FGDs revealed that water hyacinth invasion has adversely affected the lake's fisheries and navigation pathways and increased the frequency of flooding, resulting in an increased mosquito population. The results of the present study highlighted the importance of implementing water quality management programmes in the Diyawannawa wetland to control the invasion of water hyacinth. Further, we recommend increasing community participation in water hyacinth control programmes and providing opportunities for the community to engage in self-employment activities associated with the uses of water hyacinth.

Coastal freshwater lakes are distinctive landscape features in South America, and benthic macroinvertebrates are key to their ecological functioning. Identifying the main factors driving the assemblage structure of benthic macroinvertebrate is thus important for the development of management strategies in these ecosystems. However, studies on the drivers of macroinvertebrate assemblages are scarce in subtropical coastal lakes of the Neotropical region. Here, we evaluated the role of environmental (morphometric and water chemistry variables) and spatial factors in the assemblage structure of benthic macroinvertebrates in 36 coastal freshwater lakes in Brazil from 2008 to 2015. Macroinvertebrate family richness increased with ammonium, pH and water transparency, and decreased with nitrate content (slope ≈1 for all significant variables). Environmental factors explained most of the variation in macroinvertebrate composition (16%) compared to spatial ones (3.4%). In specific, Dugesiidae, Hydrobiidae, Corbiculidae, Sphaeromatidae, Noteridae, Hydropsychidae, Culicidae and Ceratopogonidae predominated in lakes with lower conductivity (<100 μS/cm) and higher water transparency (>1 m). Spatial factors summarized differences in macroinvertebrate assemblages between isolated and connected lakes. Although none of the lakes studied are directly impacted by organic pollution, our results suggest that benthic macroinvertebrate assemblages in subtropical coastal lakes are mostly structured by water chemistry, likely reflecting the major trends in land use along the study region (transition from agriculture to urban areas). We recommend that the conservation of macroinvertebrate biodiversity in southern Brazilian coastal lakes focus on the monitoring of water chemistry factors associated with human-based land use.

The Akosombo Hydroelectric Power Plant (AHPP) is one of the largest man-made lakes in the world. The impact of the dam after its construction on living organisms and people is not known. This paper offers new insights into our understanding of how the lake affects water quality for living organisms and people living downstream of its tailrace at different spatial levels. Water samples were collected to determine physicochemical and bacteriological parameters at fifteen strategically chosen sampling points. The data were analysed in the laboratory for certain physicochemical and biological parameters. About 95 questionnaires were also administered at Abume to households to ascertain their concerns with the water from the dam. The results indicated that the operation of AHPP has statistically significant effects on pH, Dissolved Oxygen (DO), faecal coliform and total coliform. The DO and total coliform did not rejuvenate by the 1km tailrace distance of the study. However, pH rejuvenated at a distance of 750 meters. The people also point out that the quality of the river at Abume is not safe for drinking and living organisms. The study concludes that water from the AHPP downstream is a satisfactory source of raw water that can be treated for domestic use. The water can also not support large fish species like tilapia. The study recommends that cage fishing should not take place close to the tailrace. The Volta River Authority and the government should provide potable drinking water to the communities affected by the construction of the dam and new sustainable turbines should be employed to manage the dam.

A cyprinid, Opsarius dogarsinghi (Hora, 1921) was recorded for the first time in September 2021 from the Kodalbasti section of the river Torsa, Jaldapara National Park complex. In September 2021, gill nets with a mesh size of 30 mm were used to catch a total of three specimens of O. dogarsinghi from the flowing water in the Kodalbasti section of the river Torsa. The species is endemic and has only been reported from a few north-eastern regions of India. The current research widens the species' geographical range from its original habitat in the river Torsa of West Bengal, India. The physicochemical properties of their riverine habitat were also described.

This study demonstrates the use of a multi-metric Fish Index of Biotic Integrity (FIBI) for assessment of ecological health of a medium-sized river, under a gradient of human disturbances in the Kenyan side of the Lake Victoria Basin (LVB). Development of the index is based on water quality, river habitat quality and fish community attributes. The river was sampled from 2019 to 2020 during wet and dry seasons of the year at nine selected sites along its length based on the level of human disturbance. A total of nine metrics representing the structural and functional organization of fish communities were qualified using the separation power of Mann–Whitney U test (p < .05). Metric values at unimpaired, intermediate, impaired and no-fish sites were used to establish the scoring criteria using inter-quartile ranges. A 1, 3, 5 scoring system representing high, fair and slight deviation from the best site, respectively, was used in the final FIBI development. River mouth station had the highest FIBI score of 43, with extensive natural riparian buffer vegetation (>20 m) and 18 fish species implying least human disturbance. The midstream section had intermediate FIBI scores of 34–36, with wide natural riparian buffer vegetation (10–20 m) and 6–9 fish species that represented moderate human disturbance. The upstream section had the least FIBI score of 0, with no fish and narrow riparian buffer vegetation (<5 m) that indicated notable degradation. This study presents the preliminary results of using fish and habitat metrics for development of an Index of Biotic Integrity (IBI) for a medium-sized river in a lake basin, as a decision-making support tool for effective management and conservation of water resources. The study recommends restoration of river habitat quality for improved ecological integrity of rivers in the Lake Victoria Basin.

Dal Lake is not only the centre of tourist attraction, but also an important livelihood source for the local population. The economic activities over the years in and around the lake have intensified, resulting in pollution, eutrophication and encroachment of the lake. The present study examined the multiple economic activities carried out on Dal Lake, estimated the net welfare generated, and subsequently developed a solution focusing on establishing an optimal trade-off between the economic activities and pollution abatement expenditures incurred by the government. Employing optimization techniques, needed modifications in the configuration of the enterprises and the pollution abatement costs that could maximize the net welfare from Dal Lake were identified. The economic welfare of the three enterprises was maximized at the optimal level of INR 5684.85 million, with a pollution-abating investment of INR 13.21 million.

Reproductive success for crustaceans depends on the transition from juvenile to adult, which can be estimated by analysing relative growth. To this end, the present study focused on the relative growth of appendix masculina length (AML), hatchery chamber width (HCW), body length (BL) and body weight (BW) in relation to carapace length (CL) of Macrobrachium villosimanus to estimate the morphological sexual maturity using the least squares method. Data for each relationship were repeatedly partitioned into two size-delimited subsets (juvenile and adult stages), considering a CL value as a hypothesized transition point. Analysis of the residuals sum of squares indicated two separate linear regressions fit the data better than a single linear regression. The study results indicated a discontinuity in allometry at 17.9 mm CL for CL versus AML, and at 15.6 mm CL for CL versus HCW relationships. These observed transition points could be associated with morphological sexual maturity of M. villosimanus. The BL and BW growth rate in relation to CL significantly decreased in males, but increased in females after reaching the morphological sexual maturity, demonstrating the existence of dimorphic growth. The increased growth rate after reaching sexual maturity in females probably corresponds to more space for the eggs and subsequent increased fertility. Accordingly, the present study indicated the secondary sexual characters (e.g. AML and HCW) play roles in attaining the morphological sexual maturity necessary for reproductive success and for ensuring the life cycle of this species.

The present study is a review of photochemical processes that occur in surface water bodies and which can affect the chemical composition of water. It is expected that water bodies with a slow rate of water exchange, including lakes, reservoirs, estuaries and ponds with significant areas of shallow water will be most vulnerable to the impacts of these processes. It involves natural organic compounds and xenobiotics of organic origin that enter water bodies from anthropogenic sources or are formed in water bodies because of the development of cyanobacteria and other algae species. Photodegradation of dissolved organic matter (DOM) occurs as a result of both direct photolysis and photosensitized cleavage involving inorganic and organic compounds, which are characterized by chromophore properties, such as humic substances. Photolysis is accompanied by the transformation of high molecular weight organic compounds into lower molecular weight compounds that can become bioavailable to, and promote the development of, microorganisms. Photodegradation results in bioavailable forms of nitrogen and phosphorus being released into the water column. Accordingly, the present study presents the results of analysis of the photochemical destruction of humic substances, such as the most widespread group of the surface water body DOM under the influence of artificial UV irradiation and solar radiation. The results provide data on the products of humic substances photolysis, as well as the influence of the latter on the destruction of a number of organic substances, including xenobiotics (herbicides, pesticides, etc.). Photolysis of algotoxins, which are mainly concentrated in the water of highly trophic reservoirs and lakes during the period of water “blooming,” is among the main concerns being addressed, noting photochemical destruction of these dangerous toxicants can be considered an important means of removing them from drinking water. Also emphasized is that photochemical processes in surface water will likely intensify in the future amid the recent climate changes, also affecting the chemical composition of water.

Wular Lake, one of the largest wetlands in Asia (13,000 ha in Kashmir Valley) is a biodiversity-rich Ramsar site supporting nearly 32,000 rural people involved in harvesting fish, water chestnuts, lotus stems and fodder. With 2914 active fishers, Wular Lake contributes 54% of Kashmir's total fish catch. Large-scale land-use changes and global warming have resulted in siltation, reduced lake area and alterations in the water flow regime, threatening lake ecology and human livelihoods. A novel census-based multi-criteria Socio-Economic Vulnerability Index (SEVI) was used to assess the vulnerability status of 23 fishing and 115 non-fishing adjacent villages. All the fishing villages exhibited ‘low’ (0.21–0.40) vulnerability levels, except Kunas village (0.42). Interestingly, no significant differences could be found in vulnerability levels between fishing (23) and non-fishing (115) villages, although the former exhibited relatively higher social sensitivity. A graphical decision matrix based on sensitivity and adaptive capacity scores provided a snapshot of vulnerability status for each village. Using SEVI scores, drivers (i.e., key indicators responsible for high sensitivity & low adaptive capacity) were identified and corresponding village-specific development interventions are suggested with Kunas as an illustrative case village. Improving education levels, strengthening community and rural infrastructure, and expanding livelihood options were key short-term strategies for improving resilience in Kashmir's Wular region.