Lake Boundary Research Articles

Spatiotemporal dynamic study of lakes and development of mathematical prediction model using geoinformatic techniques

Lake is the important part of the wetland and also the main source for agricultural irrigation, domestic water supply and industrial requirement. It maintains the aquatic ecosystem and also considered as the major place for biodiversity conservation. The lake area is getting reduced due to increase in siltation and eutrophication processes in the aquatic region. The dynamic changes of the lake create an adverse effect on the environment. The main objective of the present research is to study the spatial dynamic changes of the lake by GIS techniques and to develop the mathematical prediction model to understand the future trend of lake area. Multi-dated satellite image and topographical maps were used to generate the GIS-based thematic databases of the lake boundary for the period from 1954 to 2011. The result shows that the lake area decreased from 33.26 km2 to 10.8 km2 during 1954–2011. The decrease of the lake area is due to the natural and anthropogenic activities. In order to study the dynamic change and future trend of lakes, the spatial prediction model was developed for Thirukanchur Lake and was validated by a numerical prediction model with field based studies. The spatial model predicts that the lake area will be further reduced from 0.12 km2 in 2011 to 0.045 km2 in 2021. The above model can be applied to other lakes to predict future status of lake by adopting the required parameters.

Spatio-temporal evaluation of resolution enhancement for passive microwave soil moisture and vegetation optical depth

Space-borne passive microwave radiometers are used to derive land surface parameters such as surface soil moisture and vegetation optical depth (VOD). However, the value of such products in regional hydrology is limited by their coarse resolution. In this study, the land parameter retrieval model (LPRM) is used to derive enhanced resolution (∼10km) soil moisture and VOD from advanced microwave scanning radiometer (AMSR-E) brightness temperatures sharpened by a modulation technique based on high-frequency observations. A precipitation mask based on brightness temperatures was applied to remove precipitation artefacts in the sharpened LPRM products. The spatial and temporal patterns in the resulting products are evaluated against field-measured and modeled soil moisture as well as the normalized difference vegetation index (NDVI) over mainland Australia. Results show that resolution enhancement accurately sharpens the boundaries of different vegetation types, lakes and wetlands. Significant changes in temporal agreement between LPRM products and related datasets are limited to specific areas, such as lakes and coastal areas. Spatial correlations, on the other hand, increase over most of Australia. In addition, hydrological signals from irrigation and water bodies that were absent in the low-resolution soil moisture product become clearly visible after resolution enhancement. The increased information detail in the high-resolution LPRM products should benefit hydrological studies at regional scales.

Patterns and Processes of Salt Efflorescences in the McMurdo region, Antarctica

Evaporite salts are abundant around the McMurdo region, Antarctica (∼78°S) due to very low precipitation, low relative humidity, and limited overland flow. Hygroscopic salts in the McMurdo Dry Valleys (MDVs) are preferentially formed in locations where liquid water is present in the austral summer, including along ephemeral streams, ice-covered lake boundaries, or shallow groundwater tracks. In this study, we collected salts from the Miers, Garwood, and Taylor Valleys on the Antarctic continent, as well as around McMurdo Station on Ross Island in close proximity to water sources with the goal of understanding salt geochemistry in relationship to the hydrology of the area. Halite is ubiquitous; sodium is the major cation (ranging from 70%–90% of cations by meq kg-1 sediment) and chloride is the major anion (>50%) in nearly all samples. However, a wide variety of salt phases and morphologies are tentatively identified through scanning electron microscopy (SEM) and X-ray diffraction (XRD) work. We present new data that identifies trona (Na3(CO3)(HCO3)·2H2O), tentative gaylussite (Na2Ca(CO3)2·5H2O), and tentative glauberite (Na2Ca(SO4)2) in the MDV, of which the later one has not been documented previously. Our work allows for the evaluation of processes that influence brine evolution on a local scale, consequently informing assumptions underlying large-scale processes (such as paleoclimate) in the MDV. Hydrological modeling conducted in FREZCHEM and PHREEQC suggests that a model based on aerosol deposition alone in low elevations on the valley floor inadequately characterizes salt distributions found on the surfaces of the soil because it does not account for other hydrologic inputs/outputs. Implications for the salt distributions include their use as tracers for paleolake levels, geochemical tracers of ephemeral water tracks or “wet patches” in the soil, indicators of chemical weathering products, and potential delineators of ecological communities.

Planning Interventions for Lake Conservation: A Case of Shahpura Lake, Bhopal, India

With due increment in the development process of India, the problems related to environment are under constant increment and its contamination has now became a great threat for the rich ecology of the country. Particularly, the problems regarding the water quality are now becoming more acute and complicated due to increasing urbanization, industrialization, siltation, agricultural run-off and discharge of untreated sewage water. The city Bhopal in India having named as the city of lakes, is also experiencing similar issues. The famous characteristic lakes of Bhopal are under great environmental stress due to pollution from various sources. The Shahpura lake is one such lake, situated well within the city. A number of wards and colonies surrounding the lake boundary discharge their sewage and silage into the existing drainage network of the area, which ultimately finds its way into the lake through open drains. The main source of contamination in the lake is sewage fed drains, which are dumped into the lake during the summers. Besides this, other activities like bathing, cloth washing, cattle bathing and religious activities like idol immersion etc. also paves the way for high concentration of harmful chemicals in the lake. This work mainly discusses the existing situation and causes of water pollution in the Shahpura lake of Bhopal. It also brings into light the constitutional safeguards related to Lake Conservation in India and reviews their practical implications. In the end, it focuses on recommending the lake conservation strategies for the case of Shahpura lake; and suggests measures that could be adopted elsewhere to prevent the issue of lake pollution from various sources, emphasizing the importance of lakes.

INLAND-LAKES PROTECTION APPLICATION WITH HIGH RESOLUTION SATELLITE IMAGERY IN WUHAN CITY

Abstract. The new data source of China’s civilian high resolution earth observation system ZY-3, GF-1 were applied in the application of the monitoring and protection of the inland-lakes in Wuhan, Hubei Province. After the pre-process of these high resolution satellite images, the object-oriented classification and object-oriented change detection technology were applied in the inland-lakes protection of Wuhan, China. In this paper, the Xiwanhu Lake and Tangxunhu Lake including their surrounding areas were selected as an example, with the experiments the status of these lakes including the lake boundary, lake area and the change of these lakes including the lake water surface increased area, lake water surface decreased area were be obtained. Compared with the pixel-based method, the object-oriented classification and change detection technology shows its intuitive and higher precision in inland-lake protection. Remote sensing technology should be applied in monitoring and protection the inland-lake and other respects of water resource management more widely and deeply in China.

A lake detection algorithm (LDA) using Landsat 8 data: A comparative approach in glacial environment

Glacial lakes show a wide range of turbidity. Owing to this, the normalized difference water indices (NDWIs) as proposed by many researchers, do not give appropriate results in case of glacial lakes. In addition, the sub-pixel proportion of water and use of different optical band combinations are also reported to produce varying results. In the wake of the changing climate and increasing GLOFs (glacial lake outburst floods), there is a need to utilize wide optical and thermal capabilities of Landsat 8 data for the automated detection of glacial lakes. In the present study, the optical and thermal bandwidths of Landsat 8 data were explored along with the terrain slope parameter derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model Version2 (ASTER GDEM V2), for detecting and mapping glacial lakes. The validation of the algorithm was performed using manually digitized and subsequently field corrected lake boundaries. The pre-existing NDWIs were also evaluated to determine the supremacy and the stability of the proposed algorithm for glacial lake detection. Two new parameters, LDI (lake detection index) and LF (lake fraction) were proposed to comment on the performances of the indices. The lake detection algorithm (LDA) performed best in case of both, mixed lake pixels and pure lake pixels with no false detections (LDI=0.98) and very less areal underestimation (LF=0.73). The coefficient of determination (R2) between areal extents of lake pixels, extracted using the LDA and the actual lake area, was very high (0.99). With understanding of the terrain conditions and slight threshold adjustments, this work can be replicated for any mountainous region of the world.

Macroinvertebrate communities of ecotones between the boundaries of streams, wetlands, and lakes

Macroinvertebrate communities of ecotones between the boundaries of streams, wetlands, and lakes

Design and Characterization of a Turbulence Chamber for Scalar Flux Measurements at a Sediment-Water Interface

AbstractA turbulence chamber designed specifically for the laboratory study of environmental scalar fluxes at sediment-water interfaces was developed and fully characterized. The turbulent flow field was documented using particle image velocimetry (PIV), with particular emphasis on turbulence characterization. The chamber is capable of reproducing a wide range of turbulence levels covering 6 orders of magnitude of the dissipation rate of turbulent kinetic energy (10−10–10−4 m2 s−3). Its performance range includes conditions similar to low energy environments such as lake and reservoir bottom boundary layers (BBLs), verified by comparison to field data. The chamber is forced by three peristaltic pumps plumbed to six equispaced orifices on the top cap of the chamber, forming a closed system. The pumps drive either a momentum source (a jet) in the vertical direction or a momentum sink. The pumps operate continuously, but randomly change direction to generate a horizontally homogeneous turbulent region near ...

Impact of the desiccation of the Aral Sea on summertime surface air temperatures

The Aral Sea located in Central Asia has undergone drastic changes in the last 50 years. This study quantitatively estimates the change in lake surface area since the 1970s and investigates how this change can affect local and regional near-surface air temperatures during the summer. LANDSAT satellite imagery shows more than 80% reduction in lake surface area since the 1970s. Simulations with the Weather Research and Forecasting (WRF) regional climate model show that this change in the lake surface can lead to a statistically significant warming of more than 6 °C in 2 m air temperatures over the dry lake bed and a significant warming signal of up to 1 °C covering an area up to 200 km around the original lake boundary, especially to the south. Observations in this region are sparse but still warming trends consistent with the simulations are seen in 2 m air temperatures from the Global Historical Climatology Network dataset. Atmospheric reanalysis and land cover data suggest that large-scale climate variability and land use change in the Amu Darya and Syr Darya basins contribute to the regional warming trends. Improvements in data and modeling capability are required to study the effects on diurnal and seasonal temperature cycle.

Use of Mini‐Fyke Nets for Sampling Shallow‐Water Fish Communities in Florida Lakes

AbstractWe evaluated mini‐fyke nets for sampling shore‐based (SB; <1 m deep) fish communities in Florida lakes. Specifically, we wanted to determine the most effective deployment method and sample size required for adequately characterizing fish communities in these habitats. Shallow SB (0.15–0.6 m) net sets, in which nets were not completely submersed, collected significantly more individuals and a larger proportion of poeciliids. However, deep SB (0.6–1.0 m) net sets, in which nets were completely submersed, collected a larger proportion of centrarchids, cyprinids, and cyprinidontids. Net placement also significantly affected the overall catch and composition of samples. Nets placed in locations away from the lake boundary tended to collect actively schooling fishes such as Threadfin Shad Dorosoma petenense and cyprinids. Nets placed next to the lake boundary tended to collect species associated with shallow, vegetated habitats, particularly poeciliids, at greater frequencies. In some cases, the collection of these fishes was unique to a particular deployment method. Our results suggest that in long‐term monitoring of Florida's shore‐based lentic fish communities, nets should be placed in SB waters with the lead extending to the lake boundary. Although long‐term sampling objectives may vary, we determined that a sampling target of 30 net sets was sufficient for characterizing the fish community in terms of percentage composition, species richness, and species diversity. Furthermore, we recommend the continued use of additional gears to fully characterize littoral fish communities.Received December 19, 2013; accepted March 1, 2014

Spatiotemporal characteristics of nitrogen and phosphorus in the benthos of nearshore Lake Erie

Even though nutrient loading targets for Lake Erie have been met for almost 20years, the lake is still showing signs of eutrophication. In-lake nutrients usually originate from the outside of the lake boundaries; however, there are significant nutrient pools within the lake which potentially are cycled back to the water column from the benthic zone. A better accounting of sediment and benthic macroinvertebrate nutrient pools might further our understanding of why the lake still displays symptoms of eutrophication. We examined the spatiotemporal patterns in nitrogen and phosphorus concentrations of the numerically dominant amphipods, oligochaetes, chironomids, and dreissenid mussels, plus surficial sediments along the southern shoreline. Sediment nutrients and organic matter content increased from nearshore-to-offshore, and sediment nitrogen, but not phosphorus, showed significant differences among the basins. More than 98% of the benthic P and 94.5% of the benthic N were sequestered in the sediments whereas the remainder was in the biota. Dreissenid mussels accounted for approximately 95% of the non-sediment nutrients in the benthic zone. In 2011, an extremely wet year, the concentration of suspended solids was roughly 3.75× higher compared to the dry year (2012), and contained roughly 2.5× and 7.5× as much phosphorus and nitrogen, respectively. All benthic taxa showed significant annual differences in tissue nutrient content, potentially responding to the extreme meteorological differences between study years. There were no significant spatial differences in organism tissue nutrient concentrations either among lake basins or along the nearshore–offshore transects. We estimated that there were 41,691t of P and 116,544t of N in the benthic coastal zone. This updated accounting of the benthic nutrient pools, coupled with information on organism and sediment flux rates, might prove insightful in understanding nutrient dynamics in the Lake Erie nearshore.

Glacial Lake Expansion in the Central Himalayas by Landsat Images, 1990–2010

Glacial lake outburst flood (GLOF) is a serious hazard in high, mountainous regions. In the Himalayas, catastrophic risks of GLOFs have increased in recent years because most Himalayan glaciers have experienced remarkable downwasting under a warming climate. However, current knowledge about the distribution and recent changes in glacial lakes within the central Himalaya mountain range is still limited. Here, we conducted a systematic investigation of the glacial lakes within the entire central Himalaya range by using an object-oriented image processing method based on the Landsat Thematic Mapper (TM) or Enhanced Thematic Mapper (ETM) images from 1990 to 2010. We extracted the lake boundaries for four time points (1990, 2000, 2005 and 2010) and used a time series inspection method combined with a consistent spatial resolution of Landsat images that consistently revealed lake expansion. Our results show that the glacial lakes expanded rapidly by 17.11% from 1990 to 2010. The pre-existing, larger glacial lakes, rather than the newly formed lakes, contributed most to the areal expansion. The greatest expansions occurred at the altitudinal zones between 4800 m and 5600 m at the north side of the main Himalayan range and between 4500 m and 5600 m at the south side, respectively. Based on the expansion rate, area and type of glacial lakes, we identified 67 rapidly expanding glacial lakes in the central Himalayan region that need to be closely monitored in the future. The warming and increasing amounts of light-absorbing constituents of snow and ice could have accelerated the melting that directly affected the glacial lake expansion. Across the main central Himalayas, glacial lakes at the north side show more remarkable expansion than those at the south side. An effective monitoring and warning system for critical glacial lakes is urgently needed.

Influence from Surrounding Land on the Turbulence Measurements Above a Lake

Turbulence measurements taken at a Swedish lake are analyzed. Although the measurements took place over a relatively large lake with several km of undisturbed fetch, the turbulence structure was found to be highly influenced by the surrounding land during daytime. Variance spectra of both horizontal velocity and scalars during both unstable and stable stratification displayed a low frequency peak. The energy at lower frequencies showed a daily variation, increasing in the morning and decreasing in the afternoon. This behaviour is explained by spectral lag, where the low frequency energy due to large eddies that originate from the convective boundary layer above the surrounding land. When the air is advected over the lake the small eddies rapidly equilibrate with the new surface forcing. However, the large eddies remain for an appreciable distance and influence the turbulence in the developing lake boundary layer. The variances of the horizontal velocity and scalars are increased by these large eddies, while the turbulent fluxes are mainly unaffected. The drag coefficient, Stanton number and Dalton number used to parametrize the momentum flux, heat flux and latent heat flux respectively all compare well with current parametrizations developed for open sea conditions. The diurnal cycle of the partial pressure of methane, \(p\mathrm{CH}_{4}\), observed at this site is closely related to the diurnal cycle of the lake-air methane flux. An idealized two-dimensional model simulation of the boundary layer at a lake site indicates that the strong response of \(p\mathrm{CH}_{4}\) to the surface methane flux is due to the shallow internal boundary layer that develops above the lake, allowing methane to accumulate in a relatively small volume.

Down-slope cascading modulated by day/night variations of solar heating

Sloping sides of natural basins favour the formation of cross-shore temperature gradients (differential coastal heating/cooling), which cause significant littoral-pelagial water exchange. Autumnal denser water cascading along a sloping lake boundary, modulated by day/night variations of solar heating is considered numerically, in order to reveal the development of the cascading process in time, spatial structure of the exchange flows, and diurnal variations of volumetric flow-rate of littoral-pelagial exchange flow, as well as to compare its daily maxima at different depths/cross-sections, with known quasi-steady state predictions under constant buoyancy flux. The development of exchange flows progress through two phases: i) appearance and adjustment to day/night buoyancy flux variations; and ii) quasi-steady exchange, when variations of the flow rate in every next diurnal cycle are more or less the same as the previous day. The duration of the first phase depends on local depth (~1 day for depths of about 10 m, ~2 days for depths 15-25 m, and ~5 days down to 30 m for the considered initial linear vertical temperature stratification). Maximum horizontal exchange takes place in the cross-section where the thermocline meets the slope, and the cold down-slope currents detach from the bottom. The location of this cross-section advances off-shore with time, in accordance with the deepening of the upper mixed layer. The existence of a specific coastal circulation cell, with different water dynamics from those above the main part of the slope, is a characteristic feature of horizontal convective exchange. The mean value of the specific volumetric flow rate of the convective exchange, driven by day/night oscillations in its fully developed quasi-steady phase increases almost linearly with local depth, and is about twice as large as the quasi-steady exchange values, predicted by formula Q=0.0013·d1.37 (Q is measured in m2 s-1, and local depth above the slope d in m), suggesting that the thermal siphon, energized by oscillating day/night buoyancy fluxes, flushes coastal regions twice as efficiently as the cascading, developing under (more or less) uniform external conditions in field observations and laboratory experiments, which lie behind the given formula. Flushing time in the considered case has an order of 10-60 hours for a littoral zone of 6-30 m depth. Application of convective phase diagrams (e.g., Q vs ΔT) is suggested as a convenient way to describe the day/night convective exchange, allowing for visualization of the flow development process, its coherency and the time lag of the development at different depths.

Deriving landslide dam geometry from remote sensing images for the rapid assessment of critical parameters related to dam-breach hazards

Dam-breaches that cause outburst floods may induce downstream hazards. Because landslide dams can breach soon after they are formed, it is critical to assess the stability quickly to enable prompt action. However, dam geometry, an essential component of hazard evaluation, is not available in most cases. Our research proposes a procedure that utilizes post-landslide orthorectified remote sensing images and the pre-landslide Digital Terrain Model in the Geographic Information System to estimate the geometry of a particular dam. The procedure includes the following three modules: (1) the selection of the reference points on the dam and lake boundaries, (2) the interpolation of the dam-crest elevation, and (3) the estimation of dam-geometry parameters (i.e., the height, length, and width), the catchment area, the volumes of barrier lake and landslides dam. This procedure is demonstrated through a case study of the Namasha Landslide Dam in Taiwan. It was shown the dam-surface elevation estimated from the proposed procedure can approximate the elevation derived from profile leveling after the formation of the landslide dam. Thus, it is feasible to assess the critical parameters required for the landslide dam hazard assessment rapidly once the ortho-photo data are available. The proposed procedure is useful for quick and efficient decision making regarding hazard mitigation.

Fractionation and Potential Toxic Risk of Metals From Superficial Sediment in Itaipu Lake—Boundary Between Brazil and Paraguay

The objective of this study was to evaluate fractions of metals (labile and pseudo-total) extracted from sediment samples collected in Itaipu Lake (boundary between Brazil and Paraguay) and to assess the dynamics and mobility of these fractions by identifying the same bioavailability and ecological risk to metals in the aquatic environment. The concentrations of metal ions were determined by flame atomic absorption spectrometry. There was a correlation between the metal ions, both in the labile and the pseudo-total, with regard to particle size. To assess metals concentrations in sediment, numerical sediment-quality guidelines were applied. The concentrations of aluminum, cadmium, iron, manganese, lead, and zinc in all sediment samples are lower than the proposed probable effects level (PEL), thus possibly indicating that there are no harmful effects from these metals. In contrast, concentrations of copper, chromium, and nickel exceeded the PEL in some samples, thus indicating that these stations are at potential risk. The level of contamination in sediments of Itaipu Lake for all metals was evaluated using contamination factor, degree of contamination, and sum-of-metals toxic unit.

Subglacial Lake Whillans — Ice-penetrating radar and GPS observations of a shallow active reservoir beneath a West Antarctic ice stream

Ice-penetrating radar and kinematic GPS observations from Subglacial Lake Whillans (SLW), West Antarctica, reveal a shallow lake that is confined by steep basal topographic features. Radar imaging of SLW, although indicating wet basal conditions, is consistent with a water column depth of only ~6m or less during the near low-stand state at the time of the survey. Kinematic GPS profiles reveal that SLW is generally defined by a ~15m surface depression centered at S 84.237° W 153.614°. This point coincides with the area of lowest hydropotential in the lake basin and also the largest surface elevation range in ICESat data. Therefore this location appears to be an opportune site for subglacial access drilling of this active subglacial lake. A distinct basal topographic ridge on the grid south side of the basin is coincident with a strong contrast in relative basal reflectivity (~6dB), which we interpret as the lake boundary. Mapped hydropotential (calculated assuming hydrostatic equilibrium) shows that water enters the lake from the upstream direction and drains downstream. We hypothesize that a lake-level rise of ~5m plus flexural effects is sufficient to overtop a drainage divide. Thus SLW acts as a temporary storage basin for water beneath Whillans Ice Stream.

The key role of the chemolimnion in meromictic cenotes of the Yucatan Peninsula, Mexico

This study tests the ecological and physico-chemical effect of sharp density boundaries of meromictic lakes. The investigation was carried out in Nohoch Hol, an anchialine meromictic cenote situated 2.0 km inland from the Caribbean coast of the Yucatan Peninsula, Mexico. In situ physico-chemical parameters were recorded with a water quality datalogger at depth intervals of 0.5 m. In addition, seven water samples for determination of nutrients, bacterioplankton and phytoplankton in the water column were obtained using SCUBA. Bacterioplankton and phytoplankton densities are low, with concentrations consistent with the oligo- to ultraoligotrophic status of Nohoch Hol indicated by the low nutrient concentrations. The phytoplankton was dominated by the chlorophyte Scenedesmus. Maximum concentrations of bacterio- and phytoplankton were found at 10.0 m depth, the top of the chemolimnion. The similarity analysis clustered the samples in three defined groups: (a) the mixolimnion, (b) the mid- and bottom of the chemolimnion and the monimolimnion, and (c) the top of the chemolimnion. The principal component analysis explained over 85% of the total variance in two components (PC). PC1 was related to turbidity and the aggregation of the chlorophytes at the top of the chemolimnion. PC2 was related to dissolved oxygen and the accumulation of filamentous and total bacteria also at the top of the chemolimnion. The top of the chemolimnion acts as a boundary within the water column to the exchange of dissolved and particulate matter between the mixo and the monimolimnion and as an ecological zone with a crucial role in the biogeochemistry of Nohoch Hol.

Recovery Lakes, East Antarctica: Radar assessment of sub-glacial water extent

[1] A fast-flowing tributary of Recovery ice stream penetrates more than 500 km into the interior of East Antarctica. Recent satellite-based studies found surface features in the onset area of this tributary that indicate a significant subglacial hydraulic system, including four large smooth basins, the typical surface expression of large subglacial lakes, as well as eleven smaller areas over which ice-sheet surface elevations rapidly changed by discharge/filling of subglacial water. Here we present the first ice-penetrating radar evidence of subglacial conditions in this area. We identified a distinct ice-water interface only over a limited area within the boundaries of the investigated large smooth basins, previously hypothesized to be water-filled lakes. The radar characteristics in some areas are similar to those of a drained lake, indicating that parts of the bed are wet, but not a typical lake. We also find evidence for discrete water bodies outside of the lake boundaries. The lines of evidence indicate that the northern most two Recovery Lakes have recently drained.

Paleogeographic evolution and paleoenvironmental reconstruction of the Sudd area during the Early-Mid Holocene, Sudan

Sixty-five diatom species were identified from five localities within the top Umm Ruwaba Formation (namely Bara A, Bara B, Binaya, Sayal and Kosti). The recovered diatoms have been used here to confirm the existence of the so-called Lake Sudd, which once covered parts of central and southern Sudan, and lasted from 5.253 to 11.300 Ka B.P. The diatom assemblage indicates deposition in fresh to slightly saline water. The distribution of large-sized diatoms, noted within the study material, is attributed to the presence of spots characterized by high nutrition which correspond to the beach of the ancient lake. Integration of the paleontological results and remote sensing data permits the delineation of the lake boundary.