Water Surface Area Research Articles

Google Earth Engine Based Spatio-Temporal Changes of Bafa Lake from 1984 to 2022

The water resource management is crucial to protect environment and ecological cycle. The detection of temporal and spatial changes in the lake's water extent is important for sustainable land planning. Therefore, the areal changes over the wetlands must be well monitored. Bafa Lake is an essential downstream water in the Büyük Menderes Basin which is the largest river basin of the Aegean Region. Google Earth Engine (GEE) is an easy-to-use online remote sensing data processing platform based on cloud computing. In this study, the long-term spatio-temporal changes of Bafa Lake between 1984-2022 have been analyzed using Landsat-5/8 satellite images on the GEE platform. A total of 1093 Landsat images were processed. The annual water areas were computed through composite images per year. The water area extraction was done using the normalized water difference index (NDWI). The minimum and maximum lake water areas in 38 years were detected as 5474 ha and 6789 ha in 1990 and 2006, respectively. In the accuracy assessment according to random sampling points, the Overall Accuracy (OA) was calculated as 98% and the kappa coefficient as 0.96. The water surface area was increased by 3.9% from 1984 to 2022. Between 2015-2022, the maximum increase or decrease in the lake area compared to the previous year observed as less than 1%. Therefore, there has not been a notable variation in the water area of Bafa Lake in the past few years.

Automatic detection of water surfaces using K-means++ clustering algorithm with Landsat-9 and Sentinel-2 images on the Google Earth Engine Platform

Water is the most essential requirement for sustaining the life cycle on Earth. These resources are constantly dynamic due to anthropogenic and climatological effects. Therefore, management and consistent water policies are necessary to be followed for the proper management of water resources. Monitoring water resources is possible by accurately determining the water surface boundaries and determining the change in water surface areas. In this context, the normalized difference water index (NDWI) and modified normalized difference water index (MNDWI) were computed using JavaScript on the Google Earth Engine through Landsat-9 and Sentinel-2 satellite images. Water pixels were extracted d from other details using the K-means++ cluster algorithm based on the calculated indices. The water surfaces were determined using the Otsu thresholding method, which is the most preferred method for the NDWI and MNDWI indices calculated from the Sentinel images and was used as verification data. The K-means++ clustering algorithm yielded successful results in detecting water surfaces. In the two indices used, the NDWI index was found to be more successful than the MNDWI index. For Landsat-9 images, OA, Kappa, and F1-scores in the NDWI index were calculated as 99.72%, 0.994, and 99.57%, respectively. The OA, Kappa, and F1-scores in the NDWI index for Sentinel-2 images were calculated as 99.39%, 0.986, and 99.04%, respectively. This study demonstrated that clustering algorithms can be successfully applied to automatically detect water surfaces.

PERANCANGAN PLTS TERAPUNG UNTUK MENDUKUNG WISATA HIJAU DI BENDUNGAN TAMBLANG, DESA SAWAN, KABUPATEN BULELENG

The Province of Bali have many dams, one of it is the Tamblang Dam, which is located in Sawan Village, Sawan District, Buleleng Regency. The Government of Buleleng Regency is planning to make Tamblang Dam as a new Tourist Destination Area (Daerah Tujuan Wisata or (DTW) in order to improve the existing tourism conditions in North Bali. It is planned to utilizing Renewable Energy (Energi Baru Terbarukan or EBT) sources to support the needs of DTW and to support government programs to reaching the Bali's clean energy target on 2050. The Renewable Energy Power Plant that will be designed is a Floating Solar Photovoltaic (PV) Power Plant, as it the potential source of energy considering that Indonesia is located on the equator. The Solar PV Power Plant is designed using the tool from website by utilizing 5% of the surface area of the dam water which is 4,561.97 m2, based on Kementrian PUPR no 6 Tahun 2020 regulation. So that a Floating Solar PV Power Plant capacity of 0.6 MW is obtained by using 1,533 solar modules and produce energy reaching of 926,539 kWh in a year. The designed Floating PV need an initial investment cost of IDR 13,551,481,157, with the result of economic analysis, obtained value of each parameter including the NPV value is IDR 7,470,053,884, BCR is 2.66, and PP is less than 25 years.

Estimation of Variation of Surface Area and Volume of Water in Fishing Bays of Lake Baikal

The research estimated the water surface area and volume of the bay Proval and Posol'skiy sor in Lake Baikal by using the QGIS geographic information system. The research indicated that the bays in question were very sensitive to changes in the water level of Lake Baikal. Surface area has been found to be more sensitive to changes in water level than volume. These indicators are important for the estimation of the receiving capacity of an area and can be used to predict the quantity of receiving capacity in low water periods. The results obtained may be useful in taking measures to stabilize the population of Baikal omul and its rational use.

Dust in Western Iran: the emergence of new sources in response to shrinking water bodies

We detected sources of dust in the Middle East that contribute to dust events in Western Iran in different seasons. By the analysis of the synoptic data, we identified 309 dusty days in Western Iran during the period 2000–2016. A dusty day is diagnosed if under low horizontal visibility (< 1 km), the dust in suspension is reported at least once a day in at least three synoptic stations. We identified dust sources in the Middle East based on the analysis of the MOD04L2 data from MODIS, the backward HYSPLIT trajectory model, and synoptic conditions. The most influential sources affecting Western Iran are located on the shore and northwest of Lake Tharthar, Hour-al-Azim Marsh, the shore of Razzaza, Habbaniyah Lakes, and West Hammar Marsh, which contributed to 110, 79, 59, 56, and 51 dusty days, respectively. The fluctuation of the surface water area largely contributes to the variability of dusty days in Western Iran. Indeed, the peak dust activity in Western Iran was during the period 2008–2012 in response to the substantial shrinkage of the main water bodies in Iraq. The main sources of dust influencing Western Iran are located in northern and eastern Saudi Arabia in spring, Deir ez-Zur in Syria’s Aleppo and Raqqa in summer, and Syria’s Homs and Al-Hasakah in winter and spring. Sources of dust in Western Iraq and in most parts of entire Iraq have, respectively, led to the formation of summer and spring dust events in Western Iran. Decreased precipitation in the Middle East from autumn 2007 to 2012 and the occurrence of severe droughts have also contributed to the shrinkage of lakes and wetlands, as well as the reduced agricultural productivity in the Middle East, all of which contributed to the intensification of dust activity in Western Iran in recent decades.

Methods for virus recovery from environmental surfaces to monitor infectious viral contamination

Accurate quantification of infectious contaminants on environmental surfaces, particularly infectious viruses, is essential for contact transmission risk assessment; however, difficulties in recovering viruses from surfaces using swabs complicates this quantification process. Herein, we identified the factors that significantly affected virus recovery rates and developed an ideal swab method that yielded the highest rate of virus recovery. We comprehensively analyzed the effects of swab type (cotton/polyester), swab water content (wet/dry conditions), surface material, and surface area on the rates of viral RNA and infectious virus recovery.The virus recovery rate was significantly lower than the viral RNA recovery rate (P < 0.01), indicating difficulty in the quantification of infectious viruses. The virus recovery rate was significantly higher under wet conditions than that under dry conditions (P < 0.006), and the virus recovery rate obtained using cotton swabs was significantly higher than that using polyester swabs (P < 0.0001). Furthermore, the virus recovery rate had a strong negative correlation (correlation coefficient >0.8) with the target surface area. The maximum surface area where the virus recovery rate was ≥10% (MSA-10%) was identified as the maximum quantifiable area. For influenza virus recovery, MSA-10% on polyvinyl chloride (PVC) sheet, PVC leather, stainless steel, silicone, glass, and polycarbonate surfaces was 66.7, 193, 60.2, 144, 105, and 15.6 cm2, respectively. For feline calicivirus recovery, MSA-10% on PVC sheet, PVC leather, stainless steel, silicone, glass, and polycarbonate surfaces was 210, 111, 2120, 250, 322, and 180 cm2, respectively.The most accurate and ideal method for quantifying infectious viruses on environmental surfaces with the highest recovery rates meets three specifications: “wet conditions,” “the use of cotton swabs,” and “a target surface area of approximately 10 cm2.

Investigation of Meteorological Effects on Çivril Lake, Turkey, with Sentinel-2 Data on Google Earth Engine Platform

Lakes and reservoirs, comprising surface water bodies that vary significantly seasonally, play an essential role in the global water cycle due to their ability to hold, store, and clean water. They are crucial to our planet’s ecology and climate systems. This study analyzed Harmonized Sentinel-2 images using the Google Earth Engine (GEE) cloud platform to examine the short-term changes in the surface water bodies of Çivril Lake from March 2018 to March 2023 with meteorological data and lake surface water temperature (LSWT). This study used the Sentinel-2 Level-2A archive, a cloud filter, the NDVI (normalized difference vegetation index), NDWI (normalized difference water index), MNDWI (modified NDWI), and SWI (Sentinel water index) methods on lake surfaces utilizing the GEE platform and the random forests (RFs) method to calculate the water surface areas. The information on the water surfaces collected between March 2018 and March 2023 was used to track the trend of changes in the lake’s area. The seasonal (spring, summer, autumn, and winter) yearly and monthly changes in water areas were identified. Precipitation, evaporation, and temperature are gathered meteorological parameters that impact the observed variation in surface water bodies for the same area. The correlations between the lake area reduction and the chosen meteorological parameters revealed a strong positive or negative significant association. Meteorological parameters and human activities selected during different seasons, months, and years have directly affected the shrinkage of the lake area.

Spatial-temporal variations of surface water area during 1986–2018 in Qinghai Province, northwestern China based on Google Earth Engine

ABSTRACT Called the “Water Tower”, the water resource in Qinghai Province plays a vital role in the ecological environment of northwestern China. However, significant uncertainty exists regarding its spatial-temporal variations. In this study, the data on the surface water of Qinghai Province from 1986 to 2018 was extracted and a systemic analysis of its spatial-temporal variations and responses to climate change was conducted using the Google Earth Engine (GEE) cloud processing platform. Our findings revealed that the surface water in Qinghai Province was primarily concentrated in the Qaidam Basin, the Hoh Xil Nature Reserve, and Qinghai Lake. The surface water area in Qinghai Province exhibited an overall increasing trend, with the temperature and precipitation being the primary drivers of this expansion. These results provide crucial insights into the variations of surface water variations in Qinghai Province, northwestern China, under the influence of climate change.

Dynamic monitoring of surface water areas of nine plateau lakes in Yunnan Province using long time-series Landsat imagery based on the Google Earth Engine platform

Lakes are sensitive to both climate change and human activities, especially in the Yungui Plateau zone. As the main supply of water sources, surface water has a significant impact on environment, ecological balance and socioeconomic development. However, it is unclear how the surface water areas (SWAs) of the nine Yunnan Plateau lakes (NYPLs) have changed over previous decades. In this study, the SWAs of the NYPLs were first extracted using the optimal water index (WI) based on Landsat remote sensing images and the Google Earth Engine (GEE). Then, a spatiotemporal variation analysis of the SWAs was carried out for the NYPLs from 1988 to 2021. Finally, the correlations between the SWA changes in each lake, climatic factors and human activities were analysed. We found that the total SWAs of the NYPL have remained stable over the past 30 years, reaching a maximum of 1,012.51 km2 in 2000 and a minimum of 972.94 km2 in 2015. From 1988 to 2015, the overall SWAs of the NYPLs fluctuated steadily within 1%. However, Lakes Qilu and Yilong shrunk significantly in 2015. Generally, the SWAs of the NYPLs during the rainy season were larger than during the dry season; however, there were some differences between each period. The seasonal change in the SWAs was approximately 10 km2 in 1991, 1994, and 2003, but was relatively less in other years. Precipitation was a direct factor, whereas temperature and evaporation were indirect factors influencing the intra- and inter-annual SWAs of the NYPLs. The changes in the SWAs of the NYPLs were consistent with the precipitation trend and were negatively correlated with changes in temperature and evaporation. Evaporation had more of an influence on shallow lakes than on deep-water lakes. Human activities led to significant changes in individual lakes (such as lakes Dianchi, Yilong, and Qilu). The NYPLs had a spatially heterogeneous response to regional climate change caused by both global climate change and human activities. The results of this study can provide a data reference and decision support for the scientific management of the ecological environment of the Yunnan Plateau lakes.

Assessment of UAS Photogrammetry and Planet Imagery for Monitoring Water Levels around Railway Tracks

High water levels near railway tracks can be a major factor affecting the safety of train passage. Water conditions near the tracks are normally monitored through visual inspections. However, this method is limited in spatial coverage and may not provide comparable information over time. We evaluated the utility of satellite imagery (Planet Dove constellation at 3 m pixel size) at the landscape level to assess overall water surface area along railway tracks. Comparatively, we evaluated the use of Structure- from-Motion 3D point clouds and high spatial detail orthomosaics (3 cm) generated from a commercial off-the-shelf Unmanned Aerial System (UAS) (DJI M300 RTK) for measuring vertical water level changes and extent of surface water, respectively, within the right-of-way of a railway line in Ontario, Canada, in areas prone to high water level and flooding. Test sites of varied lengths (~180 m to 500 m), were assessed four times between June and October 2021. Our results indicate that the satellite imagery provides a large-scale overview regarding the extent of open water in wetlands at long distances from the railway tracks. Analysis of the UAS derived 3D point cloud indicates that changes in water level can be determined at the centimeter scale. Furthermore, the spatial error (horizontal and vertical alignments) between the multi-temporal UAS data collections between sites was less than 3 cm. Our research highlights the importance of using consistent UAS data collection protocols, and the significant potential of commercial off-the-shelf UAS systems for water level monitoring along railway tracks.

Modelling analysis of the potential impact of large reservoir on heatwave events

The impact of large reservoirs on regional climate extremes, such as heatwaves, is not yet well understood, primarily due to the complex interactions of heat, moisture, and momentum over mountainous terrains and the dynamic nature of water surfaces. In this study, we investigate the role of the Miyun Reservoir (MYR), one of the largest reservoirs in northern China, covering an extensive water surface area of 180 km2, in influencing a severe heatwave event that occurred southwest of MYR from 2nd to 6th July 2010. Using high-resolution simulations from the Weather Research and Forecasting Model, our findings reveal contrasting thermodynamic effects of MYR on near-surface air temperatures, with up to three degrees of warming during night-time and up to five degrees of cooling during daytime, with a spatial extent of impact reaching up to 20 km away from the reservoir. These impacts are attributed to a combination of synergized land-lake breeze and mountain-valley winds during the night, leading to the transport of warm air plumes downwind towards the plain and intensifying the heatwave. Furthermore, we observe an increase in surface water vapor brought to higher atmospheric levels due to strong vertical mixing, resulting in lowered surface-specific humidity. Our study emphasizes the dual role of large reservoirs in exacerbating remote heatwaves while providing cooling effects in their proximity. Gaining a comprehensive understanding of the intricate interactions between reservoirs, topography, and regional climate extremes is of paramount importance for accurate climate risk assessments and the formulation of effective mitigation strategies..

Reconstruction of long-term high-resolution lake variability: Algorithm improvement and applications in China

Temporal monitoring of inland water bodies using remote sensing images is often impeded by missing data caused by clouds and other adverse conditions. To date, various data recovery algorithms have been developed based on the water occurrence threshold (WOT), where the contaminated pixels are recovered by using long-term historical water distribution information. Here, we propose an improved algorithm, enhanced WOT (EWOT), which addresses the issue of mismatch between the water occurrence product and the actual historical water presence that has been neglected by previous WOT algorithms. The EWOT algorithm achieved an overall high accuracy (with a mean absolute percentage error (MAPE) = 5.1%) and prevailed against a representative WOT algorithm. The accuracy could be further reduced (MAPE = 1.6%) after the application of a novel quality control process. In addition, the temporal coverage of the high-quality surface water area time series was improved by an average of 26.2%, and the percent count and percent area of lakes with high-quality reconstructed data reached as high as 84.5% and 94.7%, respectively, facilitating the utilization of these data in further time series analysis. In general, the improvement was closely associated with the extent of the contamination before recovery. We evaluated the algorithm's ability to be implemented on a large scale in China, and the results generally were in line with previous studies. Nonetheless, our high-quality annual-based dataset presented a more comprehensive and continuous representation of the changes in lake area spanning from 2000 to 2019. The significance of improving the existing WOT algorithms is highlighted in this study, and the proposed method can be readily extended to lakes worldwide, thus providing a valuable data source to examine the causes and possible impacts of lake dynamics.

Spatiotemporal patterns of water hyacinth dynamics as a response to seasonal climate variability in Lake Tana, Ethiopia

Lake Tana, which is the largest Lake in Ethiopia, has been invaded by water hyacinths since 2011. Although the government and the community have devoted considerable time and energy over a long period to removing the invasive weed mechanically and manually, the weed has been increasing significantly. Accurate, reliable, and timely information on the spatiotemporal distribution and extent of water hyacinth is crucial to determine its evolution, propagation, and potentially vulnerable areas of the Lake. Therefore, comprehensive information on the spatial distribution of water hyacinths and their annual and seasonal variability is essential for Lake Tana’s water resource planning, development, and management. This study aims to evaluate the spatiotemporal pattern of water hyacinth and its dynamics with seasonal climate variability and impact on evapotranspiration. Landsat 7 ETM+, Landsat 8 OLI, and Sentinel 2 and meteorological datasets were employed. Supervised and manual digitization image classification methods were applied to prepare Land-use/ Land-cover in the Lake. The Mann–Kendall trend test and Pearson correlation coefficient were used to evaluate the trend of water hyacinth and the impact of climate variability on water hyacinth distribution respectively. Besides, the evapotranspiration and water losses were estimated using the FAO-56 Penman–Monteith method. The surface extent of the water hyacinth in Lake Tana has increased by 96% in 2019 from 2011. However, the surface area of the Lake has declined. That means 1603 ha of water surface area has been changed to land surface from 2011 to 2019. The average volume of water loss in Lake Tana was 0.21% of the volume of the Lake from September 2016 to December 2018.

Spatial Analysis of Intra-Annual Reed Ecosystem Dynamics at Lake Neusiedl Using RGB Drone Imagery and Deep Learning

The reed belt of Lake Neusiedl, covering half the size of the lake, is subject to massive changes due to the strong decline of the water level over the last several years, especially in 2021. In this study, we investigated the spatial and temporal variations within a long-term ecosystem research (LTER) site in a reed ecosystem at Lake Neusiedl in Austria under intense drought conditions. Spatio-temporal data sets from May to November 2021 were produced to analyze and detect changes in the wetland ecosystem over a single vegetation period. High-resolution orthomosaics processed from RGB imagery taken with an unmanned aerial vehicle (UAV) served as the basis for land cover classification and phenological analysis. An image annotation workflow was developed, and deep learning techniques using semantic image segmentation were applied to map land cover changes. The trained models delivered highly favorable results in terms of the assessed performance metrics. When considering the region between their minima and maxima, the water surface area decreased by 26.9%, the sediment area increased by 23.1%, and the vegetation area increased successively by 10.1% over the investigation period. Phenocam data for lateral phenological monitoring of the vegetation development of Phragmites australis was directly compared with phenological analysis from aerial imagery. This study reveals the enormous dynamics of the reed ecosystem of Lake Neusiedl, and additionally confirms the importance of remote sensing via drone and the strengths of deep learning for wetland classification.

THE BOTTOM RELIEF OF VYZYRKA POND (ODESSA REGION, ODESSA DISTRICT)

Problem Statement and Purpose. For arid conditions of southern Ukraine, the problem of preservation and use of the local water resources has been relevant for a long time. One of the types of adaptation of economic activity to the natural conditions of the area is artificial water bodies’ creation. Operation of ponds without repair work led to reduction of the water surface area of most of them, siltation, reduction of depths, overgrowth, as a result of which the ponds from water accumulators turned into evaporators. The publications review devoted to ponds and artificial reservoirs showed that their hydrochemical, hydrobiological regime, hydrological elements and ecological condition are mainly studying. The purpose of the research is to establish the regularities of the relief structure of the bottom of the pond in the village of Vyzyrka. Data &amp; Methods. Field research was conducted in July 2021–2022. From two reservoirs, located within the village of Vyzyrka, the larger one was investigated. Work in the water area was carried out from the rowing boat Kolibri. The depths were determined with a Garmin Echo 200 echo sounder a geodetic rail. The use of the echo sounder made it possible to visually trace the relief of the bottom changes on the tacks and choose typical underwater points during relief measurements (ND31– 7.002.-2005). The depths were determined at 60 points, located evenly across the water area. The coordinates of measurement points were determined using a Garmin GPS72H GPS receiver. The journal of points was exported to Garmin Base Camp software. Results. Vyzyrska Pond has existed as an artificial reservoir since 1923. The relief has a trough-like shape inherited from the beam relief. Three areas are distinguished in the structure of the bottom relief: flat bottom of the northern part; underwater continuation of concave coastal slopes; the central depression stretches along the axis of the reservoir from southeast to northwest. The creation and use of artificial reservoirs leads to the development of geomorphological processes associated with the interaction of the native relief, which was formed in other physical and geographical conditions, with the water environment. Further studies of the pond are aimed at establishing the spatial distribution of hydrological elements in the water area of the pond in order to establish patterns of their change, which are important for the aquatic biota development.

Passive Microwave Radiometry at Different Frequency Bands for River Discharge Retrievals

AbstractThe present era of climate change and expanding population requires major improvements in sustained observation of global river discharge. Floods and droughts are affecting food supplies, and suspected long‐term trends require appropriate data for evaluation. Orbital remote sensing can address this observational need. Here we use satellite Ka‐ (36.5 GHz) and L‐band (1–2 GHz) passive microwave radiometry (PMR) to monitor river discharge changes and determine what size rivers can be measured and the frequencies and polarization configurations that yield the most robust results. Selected satellite gauging reaches (SGRs) can be measured at near‐daily intervals from 1998 to present (Ka‐band) and 2010 to present (L‐band). The SGRs are 10–36 km in length; the dynamic proportion of water surface area within each varies with river discharge. Due to contrasting dielectric properties, water and land emit different intensities of microwave radiation; thus emission from a mixed water/land pixel decreases as the proportion of water within the pixel increases. Depending on the river and floodplain morphology, water flow area can be a robust indicator of discharge and the microwave sensors can retrieve daily discharge to ±20%. Instead of spatial resolution, it is the sensor measurement precision, geolocation accuracy, and channel and floodplain morphology that most strongly affect accuracy. Calibration of flow area signals to discharge can be performed using nearby ground stations (even if now discontinued) or by comparison to hydrologic modeling.

Suitable water surface area of the tail lake under the constraint of water diversion scheme in arid areas based on emergy theory

Study regionThe East Juyan Sea (Inner Mongolia, China) Study focusMaintaining a certain water surface area in the East Juyan Sea is the main sign of the success of the Heihe River water diversion. However, under the realistic constraint of limited water resources, the maintenance of the lake's water surface area and the oasis ecological water are in conflict. Through comprehensively considering various factors such as ecology, economy, and water resources, this study focused on the relationship between the East Juyan Sea's ecological service value and water surface area, which was investigated with emergy theory. Meanwhile, based on the status of local water resources and the principle of water diversion, the suitable water surface area of the East Juyan Sea's was given. New hydrological insights for the regionThe results indicated the optimal water surface area of the East Juyan Sea is approximately 40 km2. In addition, we can observe that the value of ecological services of a specified area increases infinitely with the expansion of its water surface area. But, within a certain threshold value, the amount of its value will become stabilize. Below or beyond this threshold, the value of regional ecological services will increase at a faster rate. However, the larger is not always better. The larger the water surface area, the easier it is to create competition for water with the oasis vegetation, which will be detrimental to the ecological health and stability of this region. Thus, the appropriate water surface area needs to be determined comprehensively by considering various factors such as ecology, economy, and water resources.

Status of aquatic organisms resources and their environments in Yangtze River system (2017–2021)

The Yangtze River is the mother river of China. To promote the aquatic ecosystem protection of the great river, the Project of Yangtze Fisheries Resources and Environment Investigation (2017–2021) supported by the Ministry of Agriculture and Rural Affairs, P. R. China carried out by 24 institutes and universities that located in the Yangtze River basin surveys the status of (1) fish species composition and spatial distribution, (2) current fish abundance, (3) endangered fishes, (4) Yangtze finless porpoise, (5) aquatic eco-environments, (6) water-level fluctuation areas, (7) capture fisheries and recreational fisheries of the Yangtze River mainstream and 10 of its main tributaries, including Yalong River, Heng River, Min River (including Dadu River), Chishui River, Tuo River, Jialing River, Wu River, Han River, Dongting Lake and Poyang Lake. The results showed that there were 443 fish species (belonging to 163 genus, 37 families, and 18 orders) before 2017, but only 323 fish species (including 15 new recorded exotic species) were recorded in the project of 2017–2021. Among them, Cyprinus carpio, Carassius auratus, Hypophthalmichthys molitrix, Pelteobagrus fulvidraco, Coilia brachygnathus, Silurus asotus, Saurogobio dabryi, Ctenopharyngodon idellus, Pelteobagrus nitidus, Hemiculter leucisculus, Siniperca chuatsi, Coreius heterodon, Culter alburnus, Parabramis pekinensis, and Aristichthys nobilis were the dominant species across the whole Yangtze River system. It is estimated that there were 886 million individuals weighing 124.8 million kg, merely equivalent to 27.3% of the resources in 1950s, 30.9% of the resources in 1960s, or 58.7% of the resources in 1980s. In the new list of protected fishes that recorded in the Yangtze River system, only 15 of 29 were collected in this project of 2017–2021. Psephurus gladius has been affirmed to be Extinct by International Union for Conservation of Nature (IUCN). The wild individuals of Tenualosa reevesii and Luciobrama macrocephalus have disappeared for many years and maybe have been extinct already. Acipenser dabryanus has been affirmed to be Extinct in the Wild by IUCN. The natural propagations of A. sinensis, Myxocyprinus asiaticus and Trachidermus fasciatus have been interrupted for many years. The populations of Yangtze finless porpoise in the Yangtze River mainstream, Dongting Lake and Poyang Lake have steadily rising sizes and expanding distributions in 2017–2021. Parts of them migrate from one region to another with the seasons, which would result in the fluctuation of Yangtze finless porpoise population within some regions. The conventional indicators of water quality in the Yangtze River system were good and conformed to the water quality criteria of fishery in 2017–2021. In the last 40 years, the maximum surface water area in the Yangtze River basin extended to approximately 63,360 km2, the minimum surface water area covered approximately 26,396 km2, and the seasonal water-level fluctuation areas occupied approximately 36,964 km2. Compared with 1984–2000 period, the 2001–2020 period witnessed an overall decreasing trend in the frequency of surface water occurrence within about 25,869 km2 of aquatic areas. From 1984 to 2000 period to 2001–2020 period, permanent surface water has decreased by nearly 8,750 km2. In 2017, the fishermen were mainly 40–60 years old and their educational levels were mainly lower than junior high school. In 2017, most anglers were older than 40 and used hand rod and/or sea rod. Their average catch of each time was mainly less than 1 kg. Results suggested that the fishing ban in key waters of the Yangtze River basin is not only an ecological project of aquatic ecosystem conservation, but also a livelihood project for the fisherman to embrace industrial transformation and improve their living conditions. After the implementation of the fishing ban, the fisheries resources would gradually recover, and the Yangtze finless porpoise population size would also see a steady increase. However, the endangered species would remain threatened for a long time. The degraded waterbodies and water-level fluctuation areas would be the key restrictive factors for future aquatic ecosystem recovery in the Yangtze River basin. Since this survey was carried out before the fishing ban, the current results could provide a baseline for future evaluation of the effect of the Yangtze River fishing ban.

Abating eutrophication on urban lakes: a case study of Kabaka's Lake, Uganda

Abstract Eutrophication of water bodies is a challenge in many urban areas. This study measured and modelled quantitatively the pollutant nutrient load of an urban lake (80,596 m2), and assessed both external (constructed wetland) and internal (dredging) eutrophication extenuation measures. For the past 25 years, there has been redistribution (p &amp;lt; 0.005) of the lake's catchment land use, with built-up area increasing by 78.5%, and a reduction in vegetated (37.2%) and water surface (1.8%) areas. A 92.2% reduction in the lakes receiving wetland footprint (p = 0.000003) was noted, with increased nutrient load. The lake's light attenuation was found to be dominated by algae, limited by nitrogen and classified under the oligotrophic class (Trophic State Index &amp;lt; 40), with a threat of eutrophication in an estimated 25 years. Scenario analyses show that the construction of a wetland in the remaining 0.54 hectares of natural wetland will reduce total phosphorus by 35% and total nitrate by 45% (p = 0.05), whereas dredging the lake could reduce them by 80% each (p = 0.0005). Watershed management is the only sustainable solution to control nutrient flow into the lake and enable self-cleansing, factoring in the design of the receiving wetland and groundwater sources.

Su Kalitesi Durum Değerlendirmesi- Salda Gölü, Türkiye

Inland water bodies, either flowing or non-flowing all around the world, are under the adverse effect of both the climate change and anthropogenic activities. The water surface areas of lakes and wetlands diminish over time and thus, this global reality brings together the deterioration of water quality especially if such water bodies confront with a variety of human activities exerting pollutants. An example of such a vulnerable ecosystem is the Lake Salda located in the southwestern part of Turkey. This lake has gained the attention of international public due to its similarities with Mars. Over a long period of time, many researches have been conducted in this lake by different disciplines and scientists to better understand its unique features. In this study, water samples from the three selected stations on the lake at three different depths were collected and analyzed on physico-chemical parameters, organic matter content, nutrients, metals and semi metals according to national legislation and Water Framework Directive (WFD) of EU. The results are tabulated and analyzed in detail considering the potential pollution sources arising from the lake’s basin. The pollutants are linked with the experimental measurements, and those parameters that exceeded the Environmental Quality Standards (EQS) are underlined. It is for sure that the lake necessitates utmost care and attention according to the results achieved.