Lake Volume Research Articles

Expansion of supraglacial lake area, volume and extent on the Greenland Ice Sheet from 1985 to 2023

Expansion of supraglacial lake area, volume and extent on the Greenland Ice Sheet from 1985 to 2023

Sources Affecting Microplastic Contamination in Mountain Lakes in Tatra National Park

The global atmospheric transport of microplastics (MPs) plays a crucial role in the contamination of remote, especially higher-elevation, environments. Precipitation is considered the main source of MP pollution. Meanwhile, plastic waste generated from, for example, tourism activities can be a local source of MP pollution. In this study, we specify which of the mentioned sources of MP, global or local, have a higher impact on the pollution level in the high-elevation oligotrophic lakes of Tatra National Park in Poland. Due to its unique natural value, it is listed by UNESCO as an international biosphere reserve and meets the criteria for Natura 2000 areas. We comprehensively analyzed the morphometric and anthropogenic features of 11 lakes in terms of the contamination level, color, shape, and polymer type of the MPs found in the surface waters. MP fibers were found to be present in all studied lakes, with contamination ranging from 25 to 179 items/m3. Polypropylene, polyethylene terephthalate, and natural or semi-natural cellulose fibers—black or red in color with a length of 0.2–1.0 mm—predominated, which corresponds with other studies conducted on remote mountain ecosystems. We did not find any correlation of the number of MPs with local anthropogenic pressure characteristics. In turn, the significant correlation with lake area, coastline length, lake volume, and catchment area indicated airborne sources, including global transport of MPs to the lakes with reduced water outflow.

Role of Lake Morphometric and Environmental Drivers of Ice Cover Formation and Occurrence on Temperate Lakes: A Case Study from the Eastern Baltic Lakeland, Poland

The presence of ice cover on temperate lakes is a crucial factor in determining the functioning of these ecosystems. The isolation of water from atmospheric influences significantly alters physical, chemical, and biological processes, and the intensity of this impact depends on the duration of the ice cover. This study analyzed the basic parameters of ice cover on several dozen lakes in Northeastern Poland. The aim of this study is to investigate the influence of morphometric parameters, alongside environmental factors, on the variation of ice cover characteristics in lakes located within the Eastern Baltic Lakeland. Characterization of ice conditions in the analyzed lakes was based on basic statistics such as minimum and maximum values, mean, standard deviation, coefficients of variation, skewness, and kurtosis. Given that the dataset contains variables describing ice phenomena in the studied lakes and data describing location, morphometric parameters, and land cover directly adjacent to the lake (treated as independent variables), a method of Spearman’s rank correlations and constrained ordination method were decided upon. Despite the relatively small study area, significant variability was observed, with average differences as follows: 26 days for the onset of ice cover, 17 days for the end date, 15 cm for ice thickness, and a 30-day difference in the average duration of ice cover. Key factors included parameters such as lake volume, average depth, and land use (urbanized and agricultural areas). Understanding parameters such as the onset and end of ice cover is essential for lake ecosystems, both from an ecological and economic perspective. This knowledge is crucial for interpreting the behavior of living organisms, water quality, and economic considerations.

Reconstructing Tibetan Plateau lake bathymetry using ICESat-2 photon-counting laser altimetry

Lake bathymetry is important for quantifying and characterizing underwater morphology and its geophysical state, which is critical for hydrological and ecological studies. Due primarily to the harsh environment of the Tibetan Plateau, there is a severe lack of lake bathymetry measurements, limiting the accurate estimation of total lake volumes and their evolutions. Here, we propose a novel lake bathymetry reconstruction by combining ICESat-2/ATLAS (Advanced Topography Laser Altimetry System) data with a numerical model. An improved grid-based photon noise removal method is used to address the photon signal buried in the background noise during the local daytime. The developed model was validated for seven lakes on the Tibetan Plateau and showed good agreement between simulated and measured lake volumes, with an average absolute percentage error of 8.0 % for maximum water depth and 19.7 % for lake volume simulations. The model was then utilized to estimate the water volume of other lakes by combining it with the self-affine theory. The lake depths obtained from ICESat-2/ATLAS show good agreement (RMSE = 0.69 m; rRMSE = 10.3 %) with available in-situ measurements for lakes with depths <16.5 m, demonstrating the potential of ICESat-2/ATLAS for improved reconstruction of the bathymetry of clear water inland lakes. Our study reveals for the first time, that the Tibetan Plateau has an estimated total lake water volume of 1043.69 ± 341.31 km3 for 33,477 lakes (>0.01 km2) in 2022. Over 70 % (∼734.8 km3) of the lake water storage is concentrated in the Inner Plateau, with the Yellow River basin accounting for 10.9 % (∼113.9 km3), followed by the Indus River basin with 7.2 % (∼75.1 km3). Our study provides a robust method for estimating total lake volumes where in-situ measurements are scarce and can be extended to other clear water lakes, thus contributing to more accurate global assessments and towards comprehensive quantification of Earth's surface water resources distribution.

Changes monitoring in Hongjiannao Lake from 1987 to 2023 using Google Earth Engine and analysis of climatic and anthropogenic forces

The research aimed to quantify the lake area dynamics, evaluate the changes in distance and rate of lake shorelines quantitatively and spatially and investigate the key factors influencing the Hongjiannao Lake (HL) area shrinkage. The study used remote sensing (RS) data from Landsat TM/ETM+ and OLI images and Google Earth Engine (GEE), a cloud platform for obtaining the lake surface area and island information from 1987 to 2023. A modified normalized difference water index (MNDWI) was applied to water area extraction. Digital Shoreline Analysis System (DSAS) was employed to assess net shoreline movement (NSM) and depict the lake shoreline length and rate changes. Furthermore, the water level was derived by ASTER GDEM V2 using the waterline method and lake boundaries. Six climatic features (temperature, precipitation, potential and actual evaporation, aridity index, and actual water difference) were investigated to find the driving factors of lake area shrinkage by correlation and factor analysis. The results reveal that during 1987–2023, the HL area has undergone four separate phases: stable (1987–1997), shrinkage (1998–2015), growth (2016–2019), and reduction (2020–2023). The most substantial negative change (−7.45%) in the HL area was observed in 1998. NSM analysis demonstrates that the lake has experienced both expansion and shrinkage at various times and locations. According to Water Balance Method, the water volume of HL exhibited variations, ranging from −0.1895 to −0.009 km³. The average yearly change in lake volume, water level, and area displayed similar characteristics with high inconstancy. Correlation and factor analysis of lake area and climatic factors demonstrate that higher precipitation, low temperatures, less potential evaporation level, lower actual evaporation rates, and more minor differences in water levels are associated with an increase in lake area. In contrast, the opposite conditions lead to a reduction in lake size.

Effectiveness of diluting Moses Lake, Washington, with low phosphorus Columbia River water

Welch, EB and Brattebo SK. 2024. Effectiveness of diluting Moses Lake, Washington, with low phosphorus Columbia River water. Lake Reserv. Manage. 40:xxxx-xxxx. Moses Lake has been rehabilitated by dilution with low total phosphorus (TP) inflow to improve lake quality in 46 of the past 47 years. Inflows of low TP (7 µg/L) Columbia River water (CRW), which enters during April–September, have ranged from around 75 to over 400 × 106 m3 (mcm), representing 0.5–2.5 total lake volumes annually. The CRW inflows substantially lowered the May–September average lower lake TP from 152 µg/L during 1969–1970 before dilution to 25 µg/L during the past 24 years when CRW input averaged 250 mcm. Total P decreased to an average of 65 µg/L during 11 of the first 12 years following the start of large CRW inputs with the Clean Lakes Project in 1977. Increased CRW inflow since 2000 reduced TP to less than 30 µg/L and has greatly improved lake quality and lowered the cyanobacteria fraction of phytoplankton biomass. Cyanobacteria were minimal at 5–22% of phytoplankton biomass in 2 years (2001, 2021) with 284 mcm of CRW inflow and average TPs of 19 and 20 µg/L. Average TP was 20 and 25 µg/L and cyanobacteria were 12 and 22% in 2022 and 2023 with less CRW (235 and 197 mcm). Even in the more enriched upper lake, TP in 2021–2023 averaged about half that of the previous 4 years (39 vs. 73 µg/L) and cyanobacteria averaged 33% of phytoplankton biomass. Unless the internal TP load is reduced substantially, CRW input should be at least 250 mcm to dilute external and internal loading and to hold TP below 30 µg/L and minimize cyanobacteria, as occurred in 2021–2023.

Identification and quantitative estimates of groundwater transfers to formerly charophyte dominated marl lakes with radon-222

Interaction with groundwater determines many processes in marl lakes. Net transfer of inorganic carbon helps define their chemical characteristics and determines their unique benthic flora. Nutrient enrichment weakens the biogeochemical buffering mechanisms which help maintain a clear-water state and many small, shallow marl lakes are prone to siltation. Despite hydrological processes being recognised as important for the complex interactions between plants, nutrient availability and physical sediment properties which shape marl lake ecology, groundwater discharge to many of these lakes has never been quantified. The aim of this study was to locate and quantify groundwater transfers to degraded marl lakes in a Special Area of Conservation on the island of Ireland. A RAD7 radon detector identified and measured elevated concentrations of 222Rn in three lakes for quantifying their groundwater influx with a 222Rn mass-balance equation. Conservative estimates of mean daily groundwater discharge to Kilroosky Lough, Drumacrittin Lough, and Dummy's Lough were 143 m3, 502 m3, and 269 m3 respectively. With extrapolation to the entire hydrological year, annual groundwater recharge contributed approximately 47 %, 155 %, and 50 % of the respective lake volumes. The areas within the lakes which were found to have the highest groundwater influence also closely matched the locations where substantial charophyte communities persist suggesting that the two are linked. These findings underline the importance of groundwater transfers for the water budget in small marl lakes and will inform management efforts to mitigate their eutrophication.

Long‐range transport of littoral methane explains the metalimnetic methane peak in a large lake

AbstractIn large and stratified lakes, substantial methane stocks are often observed within the metalimnion. The origin of the methane (CH4) accumulated in the metalimnion during stratification, which can sustain significant emissions during convective mixing, is still widely debated. While commonly attributed to the transport of methane produced anaerobically ex situ, recent evidence suggests that oxic in situ methane production could also contribute to metalimnetic methane peaks. Here, we assessed the origin, that is, pelagic CH4 production or transport of sublittoral CH4 through the interflow, of metalimnetic methane in Lake Geneva, the largest lake in Western Europe. Microbial diversity data do not support the hypothesis of oxic methane production in the metalimnion. In contrast, both spatial and temporal surveys of methane show that maxima occur at depths and sites most affected by the Rhône River inflow. Methane δ13C values point to an anaerobic sublittoral methane source, within a biogeochemical hotspot close to the river delta region, and an efficient transport across several kilometers in a vertically well‐constrained metalimnion. Our current findings emphasize the indirect role of river interflows for the long‐range transport of CH4 produced in sediment biogeochemical hotspots, even for large lakes where sublittoral habitats represent a fairly limited fraction of the lake volume.

A geospatial modelling for glacial lake outburst floods susceptibility analysis in the Central Himalayas

ABSTRACT Glacial lakes have increased throughout a significant portion of the Himalayan region, and hence the present study focuses on a geospatial modelling approach for analysing the susceptibility to glacier lake outburst flood (GLOF) in the central Himalayan region. Multitemporal satellite imageries such as Landsat-TM and Sentinel-2 were taken. The hydrodynamic compatibility tool, i.e. HEC-RAS 5.0, was used for GLOF prediction, and the lake volume and surface area were calculated using established empirical equations. The breach fails and flood flow were approximated, and arising uncertainties were analysed with three outburst scenarios. The number of lakes and their sizes have significantly increased according to the findings of the study. Of these, the Vasundhara Lake (VL), which is located at 4,676 m above the sea level, is assigned to the hazardous category for more examination. It has been found that the lake's area expanded over the past three decades (i.e. 1994–2020), rising from 0.15 to 0.29 km2. The study demonstrates that, in the worst-case situation, infrastructure along riverbanks may be susceptible to harm. The study provides information on the potential effects of GLOF events in the study region that might be used in early warning systems and water resource management plans.

Water Resources Monitoring in a Remote Region: Earth Observation-Based Study of Endorheic Lakes

In the western Andes, climate changes have led to drastic ecological changes during the Pleistocene and Holocene. Given the debate surrounding precipitation pattern changes and the lack of research on lakes in the Chilean Altiplano, this study aims to assess recent climate changes. The paper presents an innovative methodology based on Google Earth Engine (GEE), utilizing fluctuations in water levels in endorheic lakes as natural precipitation indicators. Three lakes (Chungará, Miscanti, and Miniques) in isolated drainage systems were studied, where changes in water levels directly reflect rainfall variations. Data from Landsat-OLI 8, Landsat-ETM+, Landsat-TM 5, and MODIS spanning 31 years were processed using the Google Earth Engine platform. The shapes of the water bodies were extracted using hue saturation value (HSV) composites. The surface areas of the lakes were compared with precipitation data from national meteorological stations and the Tropical Rainfall Measuring Mission (TRMM) using linear regression analyses. Both lake area and rainfall volume showed a decrease over time, with varying trends depending on environmental conditions. However, the analysis consistently indicates a reduction in the area and volume of Chilean lakes corresponding to observed rainfall patterns over the past three decades.

Assessing the Impact of Climate Change on Glacial Lake Outburst Flood (GLOF) in Eastern Hindu Kush Region Using Integrated Geo-Statistical and Spatial Hydrological Approach

Glacier retreat, a major impact of climate change that continues to occur in many parts of the world, continues to increase the risk of glacial lake outburst floods (GLOFs) in northern Pakistan. The rapid melting of glaciers in the mountains of Northern Pakistan, including the Hindu Kush, the Himalayas and the Karakoram, the rapid melting of glacier has led to the formation of 3044 glacial lakes, with 33 identified as particularly vulnerable to GLOFs. This study uses remote sensing and geographic information systems (GIS) methods for mapping and representing GLOFs. Based on the observational data of lake area, volume, and depth, empirical equations are developed through statistical methods. Only two lakes, Chitral-GL2 and Swat-G31, are classified as lakes with high potential for GLOF. Through modeling techniques using HEC-RAS and HEC-GeoRAS spatial hydrological models integrated with GIS remote sensing, the spatial extent and depth of inundations under different lake volumes are assessed. The analysis reveals that a total area of 20.56 km2 is susceptible to submersion by GLOFs, with Chitral-GL2 flooding area of 14.80 km2 and Swat-GL31 5.79 km2. Different land types are impacted by critical water depths, with built-up and agricultural lands 2.7 km2 totally, and barren lands 8.93 km2 under different flood depths ranging from less than 5 m to over 15 m.

Heterogeneous changes in global glacial lakes under coupled climate warming and glacier thinning

Global glacial lakes have expanded markedly in recent decades, accompanied by many catastrophic glacial lake outburst floods. However, our understanding of glacial lake evolution and connections with global warming and glacier thinning remains insufficient due to fragmented studies and a lack of standardized mapping. Here we evaluated the glacial lake changes and their drivers, taking care to accurately map glacial lakes while excluding non-glacier fed lakes in the same geographic area. In 2020, a total of 71,508 glacial lakes were identified worldwide, covering an area of 21,770.9±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm$$\\end{document}544.2 km2. The total volume of 1280.6±\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pm$$\\end{document}354.1 km3 is equivalent to a sea-level rise of 3.45 mm. Since the 1990s, glacial lake numbers, areas, and volumes increased by 54%, 11%, and 9%, respectively. The spatial evolution patterns align well with resolved large-scale, decadal glacier mass changes. Glacier-fed lakes extensively expanded due to glacier retreat and melting, while ice-dammed lakes were primarily affected by thinning ice dams, resulting in heterogeneous changes and underestimated outburst potential. Under the sustained glacier degradation scenario, the results of this study have implications for further evaluation of glacial lake water resources and outburst risks on a global scale.

Submerged Surface Area and Water Storage Volume of Hamrin Dam Lake Using Contour Lines

The predictions and warnings from drying up lakes and rivers are increasing nowadays, especially in Iraq, due to climatic changes and water flow reduction from neighboring countries. Consequently, this paper deals with monitoring the changes in submerged surface areas and Hamrin dam lake storage volume from December 2011 to the end of 2022. Hamrin Lake supplies Diyala province, Iraq, with irrigation water. Multitemporal satellite images were acquired from google earth pro and Earth Observation (EO) browsers. Triangular Irregular Network (TIN) layers generated contour lines through the ArcGIS environment. Volumes were calculated using the end area method. The results show that the water storage volume reached 1.8 billion cubic meters (bcm) in December 2016 and decreased to 12 million cubic meters in December 2021. Hamrin Lake lost 99% and 98% of its capacity relative to the normal water storage volume in 2021 and 2022, respectively. At normal storage, the maximum water volume of Hamrin Lake is about 3 bcm. The scarcity of irrigation water from Hamrin Lake causes decreasing agricultural areas, desertification, and people migrating to other regions.

Morphometric characteristics of Lake Limboto as critical lake in Gorontalo Province, Indonesia

This research aims to investigate the factors leading to siltation in Lake Limboto by analyzing its morphometric characteristics gathered through direct field measurements and remote sensing using Geographic Information System (GIS). Lake Limboto covers an approximate surface area of 26.09 square kilometers, boasts a maximum depth of 4 meters, and maintains an average depth of 2.83 meters. The Shoreline Development Index (SDI) stands at approximately 2.57, indicating an irregular shape of the lake's water body, while the Lake Volume Development (VD) index, at 2.12, suggests a generally flat lake bottom. The Relative Depth (Zr) registers at around 0.69%, as observed from the water turbidity level. The lakebed relief in the vicinity of the lake's periphery is predominantly flat and shallow, particularly in the western, northern, and southern regions, with depths measuring less than 2 meters. In contrast, the lakebed relief in the central and eastern sections tends to be less flat but still features depths of less than 4 meters. Siltation in Lake Limboto primarily results from high sediment input originating from erosion processes, agricultural activities, and settlements in the surrounding area.

Bayesian Approach to Estimate Proglacial Lake Volume (BE‐GLAV)

AbstractWe present a new model called Bayesian Estimated Glacial Lake Volume (BE‐GLAV) to estimate the volume of proglacial lakes. Presuming the lake cross‐section as trapezoidal, BE‐GLAV uses a Bayesian calibration approach to adjust the cross‐sectional geometry to match modeled and observed lake surface widths. We validated our model using bathymetric measurements from lakes spread across High Mountain Asia (specifically, the Himalaya and Tien‐Shan), with aerial extents ranging from 0.01 to 5.5 km2. The modeled lake volumes agreed with the measured lake volume with a root‐mean‐square absolute uncertainty of ∼14%. With minimum and maximum errors of ∼0.3% and ∼61.2%, BE‐GLAV performed well compared to 10 other models in a model inter‐comparison experiment. Using the measured set of volumes, our model can constrain both the root mean square (RMS) error and the maximum percentage error in modeled lake volume, unlike other models, some of which can compute just the RMS uncertainty.

Interacting impacts of hydrological changes and air temperature warming on lake temperatures highlight the potential for adaptive management.

Globally, climate warming is increasing air temperatures and changing river flows, but few studies have explicitly considered the consequences for lake temperatures of these dual effects, or the potential to manage lake inflows to mitigate climate warming impacts. Using a one-dimensional model, we tested the sensitivity of lake temperatures to the separate and interacting effects of changes in air temperature and inflow on a small, short-residence time (annual average ≈ 20days), temperate lake. Reducing inflow by 70% increased summer lake surface temperatures 1.0-1.2°C and water column stability by 11-19%, equivalent to the effect of 1.2°C air temperature warming. Conversely, similar increases in inflow could result in lake summer cooling, sufficient to mitigate 0.75°C air temperature rise, increasing to more than 1.1°C if inflow temperature does not rise. We discuss how altering lake inflow volume and temperature could be added to the suite of adaptation measures for lakes.

Long-term Satellite-derived Bathymetry of Arctic Supraglacial Lake from ICESat-2 and Sentinel-2

Abstract. The polar ice sheets serve as natural thermostats, regulating Earth’s temperatures. The Greenland Ice Sheet (GrIS), the second-largest ice sheet, is a critical indicator of climate change and global warming. Estimating the volume of supraglacial lakes on the GrIS, which is directly linked to the extent of melting in the Arctic ice sheet, requires information on both lake area and water depth. Conventional bathymetric methods (i.e., airborne bathymetric LiDAR, shipborne echo-sounder) are commonly used for accurate water depth measurement. However, polar supraglacial lakes face challenging conditions, leading to uncertainties in their spatial and temporal distribution. To overcome the limitations, this study combines Sentinel-2 and ICESat-2 (Ice, Cloud, and Land Elevation Satellite-2) to estimate bathymetry and detect changes in lake volume on the GrIS from 2019 to 2023. Firstly, Sentinel-2 images were pre-processed, and ICESat-2 single-photon LiDAR points were extracted using the DBSCAN (Density-Based Spatial Clustering of Applications with Noise) method, followed by the bathymetric corrections as the training data. Subsequently, three bathymetry models (i.e., log-linear, log-ratio, and BP (Back Propagation) neural network) were constructed using Sentinel-2 images and ICESat-2 data. Lastly, the highresolution ArcticDEM (Arctic Digital Elevation Model) was used as the validation data to assess the satellite-derived bathymetry accuracy. In this study, the log-ratio model yielded the best results with the R2, RMSE, and MAE of 0.92, 0.79 m (lower than 10% of the maximum depth), and 0.62 m. The results demonstrate the feasibility of the integrated active and passive remote sensing approach for bathymetry in Arctic supraglacial lakes.

Calculation of Kinetic Fractionation of Open‐Water Evaporation Over an Upland Reservoir

AbstractBased on the fact that many water reservoirs built in headwater catchments receive no water input during dry season, we modified the Craig‐Gordon model and proposed an approach to calculate kinetic fractionation factors in open‐water evaporation taking into account isotopic compositions of precipitation and of lake water, lake volume, and land‐based meteorological data. The approach is centered around the determination of lake water isotope enrichment rate over time during dry periods. We then applied this approach for calculating kinetic fractionation factors, turbulence index, and open‐water evaporation for a small reservoir located in a sub‐tropical monsoonal climate. We found that the kinetic fractionation factors, εK,H and εK,O are, respectively 3.11‰ ± 0.41‰ and 2.50‰ ± 2.15‰, corresponding to the turbulence index of 0.43 ± 0.19. Evaporation rates in open‐water estimated by our approach is 1.55 times of the land‐based evaporation gauged in the nearby meteorological station. Wind speed, represented by turbulence index, is proved as an important climatic factor influencing kinetic fractionation. This study confirms that wind and surface area factors, which have been neglected in several isotope mass balance models, should be included into calculation process.

Elastic Stress Coupling Between Supraglacial Lakes

AbstractSupraglacial lakes have been observed to drain within hours of each other, leading to the hypothesis that stress transmission following one drainage may be sufficient to induce hydro‐fracture‐driven drainages of other nearby lakes. However, available observations characterizing drainage‐induced stress perturbations have been insufficient to evaluate this hypothesis. Here, we use ice‐sheet surface‐displacement observations from a dense global positioning system array deployed in the Greenland Ice Sheet ablation zone to investigate elastic stress transmission between three neighboring supraglacial lake basins. We find that drainage of a central lake can place neighboring basins in either tensional or compressional stress relative to their hydro‐fracture scarp orientations, either promoting or inhibiting hydro‐fracture initiation beneath those lakes. For two lakes located within our array that drain close in time, we identify tensional surface stresses caused by ice‐sheet uplift due to basal‐cavity opening as the physical explanation for these lakes' temporally clustered hydro‐fracture‐driven drainages and frequent triggering behavior. However, lake‐drainage‐induced stresses in the up‐flowline direction remain low beyond the margins of the drained lakes. This short stress‐coupling length scale is consistent with idealized lake‐drainage scenarios for a range of lake volumes and ice‐sheet thicknesses. Thus, on elastic timescales, our observations and idealized‐model results support a stress‐transmission hypothesis for inducing hydro‐fracture‐driven drainage of lakes located within the region of basal cavity opening produced by the initial drainage, but refute this hypothesis for distal lakes.

Analysis of morphological change of lentic water bodies by using spatial vulnerability index (SVI) in Tarai region of Rapti river plains, India

ABSTRACT Spatio-temporal analysis of waterbodies in terms of detection of morphological change could serve as a guiding tool to restore the lentic ecosystem. This research analysed the loss of lake extent within 50 years (1969–2019) through natural, anthropogenic reasons, as well as a lack of attention to protecting lakes in the Tarai region. In 1969, 75 lakes were found, but now only 46 lakes are alive. Among the 75 lakes, seventeen transformed into large ponds after reduction in extent, and twelve lakes either appeared as waterlogging zones during the rainy season or were permanently extinct and used as agricultural fields’ built-up activities. The spatial vulnerability index (SVI) measured the level of deterioration and urgency of lake restoration. 8 lakes were determined to be highly vulnerable (below 29.26%) and lost about 311.20 hectares of potential area of lake beds due to gradual increasing shallowness. Regression analysis measured a very weak correlation between the reducing percent of lake extent (during 50 years) and current lake extent (R2 = 0.1336), average depth (R2 = 0.0035), circumference (R2 = 0.0543), and volume (R2 = 0.0728) of 46 lakes. This study elucidated the restoration practices of the lakes to prevent their gradual extinction.