scholarly journals Daily water-level variations of supraglacial lakes in the southern Inylchek Glacier, Central Asia

2020 ◽  
Author(s):  
Naoki Sakurai ◽  
Chiyuki Narama ◽  
Mirlan Daiyrov ◽  
Muhammed Esenamanov ◽  
Zarylbek Usekov ◽  
...  
Keyword(s):  
Water Level ◽  
Drainage Water ◽  
Water Levels ◽  
Supraglacial Lakes ◽  
Surface Models ◽  
Increase Rate ◽  
Aerial Vehicle ◽  
Water Level Variations ◽  
Daily Water ◽  
Lake Drainage

Abstract. To better understand the storage in and drainage through supraglacial lakes and englacial conduits, we investigated the daily water-level variations of supraglacial lakes on the southern Inylchek Glacier in Kyrgyzstan. To examine these variations, we used daily aerial digital images over three years (22 July–15 August 2017, 8–29 July 2018, and 12–19 July 2019) from an unmanned aerial vehicle (UAV) that were converted to digital surface models (DSMs) and ortho-images. Our main results are as follows. 1) When one lake drained, the water levels of other lakes might simultaneously increase, indicating that drainage water is shared with several lakes through a main englacial conduit. In one drainage event, a branch englacial conduit clearly connected to a main englacial conduit. 2) Sometimes, several lakes discharged simultaneously, indicating that several lakes had connected to a main englacial conduit that had opened. Such a case can cause larger-scale drainage than that from the opening of a branch englacial conduit. 3) Several lakes discharged twice in the same year, each time through a different conduit, indicating that the main englacial conduit can be abandoned and reused. 4) In some lakes, the water level gradually increased with nearly the same increase rate just before drainage. Such an increase may be an indicator of imminent lake drainage.

scholarly journals Simultaneous drainage events from supraglacial lakes on the southern Inylchek Glacier, Central Asia

2021 ◽  
pp. 1-12
Author(s):  
Naoki Sakurai ◽  
Chiyuki Narama ◽  
Mirlan Daiyrov ◽  
Muhammed Esenamanov ◽  
Zarylbek Usekov ◽  
...  
Keyword(s):  
Water Level ◽  
Drainage Water ◽  
Water Levels ◽  
Aerial Images ◽  
Supraglacial Lakes ◽  
Surface Models ◽  
Increase Rate ◽  
Aerial Vehicle ◽  
Water Level Variations ◽  
Gradient Line

Abstract To understand the mechanism of simultaneous drainage event related to supraglacial lakes on a debris-covered glacier, we investigated water-level variations of supraglacial lakes on the southern Inylchek Glacier in Kyrgyzstan. To examine these variations, we used daily aerial images for 2017–2019 from an uncrewed aerial vehicle that were converted to 15 cm-digital surface models and ortho-images. Our main results are as follows: (1) When one lake drained, the water levels of other lakes simultaneously increased, indicating that drainage water is shared with several lakes through a main englacial conduit. In one drainage event, a branched off englacial conduit clearly connected to a main englacial conduit. (2) Sometimes several lakes discharged simultaneously, indicating that several lakes had connected to a main englacial conduit that had opened. Such cases can cause larger-scale drainage than that from the opening of a branched off englacial conduit. (3) Simultaneous drainage occurred twice in the same year, each time through a different conduit, indicating that the main englacial conduit can be abandoned and reused. (4) In some lakes, the water level on the hydraulic gradient line increased gradually with nearly the same increase rate just before drainage. Such an increase may be an indicator of a possible simultaneous drainage event.

scholarly journals Dynamics of fortnightly water level variations along a tide-dominated estuary with negligible river discharge

2021 ◽  
Author(s):  
Erwan Garel ◽  
Ping Zhang ◽  
Huayang Cai
Keyword(s):  
Water Level ◽  
Phase Difference ◽  
River Discharge ◽  
Water Levels ◽  
Level Increase ◽  
Upstream Direction ◽  
Water Level Variations ◽  
Mean Water Level ◽  
The Mean ◽  
Guadiana Estuary

Abstract. Observations indicate that the fortnightly fluctuations in mean water level increase in amplitude along the lower half of a tide-dominated estuary (The Guadiana estuary) with negligible river discharge but remain constant upstream. Analytical solutions reproducing the semi-diurnal wave propagation shows that this pattern results from reflection effects at the estuary head. The phase difference between velocity and elevation increases from the mouth to the head (where the wave has a standing nature) as the high and low water levels get progressively closer to slack water. Thus, the tidal (flood-ebb) asymmetry in discharge is reduced in the upstream direction. It becomes negligible along the upper estuary half, as the mean sea level remains constant despite increased friction due to wave shoaling. Observations of a flat mean water level along a significant portion of an upper estuary, easier to obtain than the phase difference, can therefore indicate significant reflection of the propagating semi-diurnal wave at the head. Details of the analytical model shows that changes in the mean depth or length of semi-arid estuaries, in particular for macrotidal locations, affect the fortnightly tide amplitude, and thus the upstream mass transport and inundation regime. This has significant potential impacts on the estuarine environment.

scholarly journals Feedback Mechanism in Bifurcating River Systems: the Effect on Water-Level Sensitivity

Water ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1915
Author(s):  
Matthijs R.A. Gensen ◽  
Jord J. Warmink ◽  
Fredrik Huthoff ◽  
Suzanne J.M.H. Hulscher
Keyword(s):  
Water Level ◽  
Flood Risk ◽  
River System ◽  
Feedback Mechanism ◽  
Water Levels ◽  
River Systems ◽  
Water Level Variations ◽  
System Water ◽  
Discharge Distribution ◽  
Single Branch

Accurate and reliable estimates of water levels are essential to assess flood risk in river systems. In current practice, uncertainties involved and the sensitivity of water levels to these uncertainties are studied in single-branch rivers, while many rivers in deltas consist of multiple distributaries. In a bifurcating river, a feedback mechanism exists between the downstream water levels and the discharge distribution at the bifurcation. This paper aims to quantify the sensitivity of water levels to main channel roughness in a bifurcating river system. Water levels are modelled for various roughness scenarios under a wide range of discharge conditions using a one-dimensional hydraulic model. The results show that the feedback mechanism reduces the sensitivity of water levels to local changes of roughness in comparison to the single-branch river. However, in the smaller branches of the system, water-level variations induced by the changes in discharge distribution can exceed the water-level variations of the single-branch river. Therefore, water levels throughout the entire system are dominated by the conditions in the largest branch. As the feedback mechanism is important, the river system should be considered as one interconnected system in river maintenance of rivers, flood-risk analyses, and future planning of river engineering works.

Influence of morphometric parameters and meteorological conditions on ephemeral pool hydrology in the Canadian Shield forest 

2021 ◽  
Author(s):  
Marjolaine Roux ◽  
Marie Larocque ◽  
Philippe Nolet ◽  
Sylvain Gagné
Keyword(s):  
Surface Water ◽  
Water Level ◽  
Meteorological Conditions ◽  
Canadian Shield ◽  
Water Levels ◽  
Forest Biodiversity ◽  
Rainfall Events ◽  
Ephemeral Pools ◽  
Water Level Variations ◽  
Dry Out

<p>Ephemeral pools are geographically isolated wetlands commonly found in temperate forests of northeastern North America. These wetlands are usually hydrologically isolated from the surface water network but in some conditions can be connected to local groundwater flow. They fill at maximal capacity following spring snowmelt and dry out during summer. They contribute to forest biodiversity by providing breeding habitats for amphibians during their spring and early summer period of hydrological activity. However, ephemeral pools are poorly understood and rarely studied because of their small dimensions and temporary hydrology. This work presents the final results of a five-year study aimed to acquire new knowledge on ephemeral pool hydrology to go beyond the anecdotical pool and to understand the conditions and processes that driving their hydrology. A large number of pools (39) located in the Canadian Shield forest were instrumented to monitor hourly water level variations in the pool and in the neighboring and underlying fractured bedrock aquifer. They were also described in extensive details for their geomorphological features and water levels over a period from one to five years (April 2016 to July 2020). The first rather surprising result from this work is that, although the pools are all located in bedrock depressions, they cover a wide range of morphologies. Their maximum sizes vary from 29 to 1866 m<sup>2</sup> and their maximal volumes vary from 4 to 654 m<sup>3</sup>. Their maximum water depths are also highly contrasted, ranging from 0.14 m to 2.03 m. The pool depressions are overlain by mineral sediments (silt to fine sand with occurrences of coarse sand and gravel) of contrasted thicknesses (0 m to 1.70 m). An organic matter layer of highly varying thickness (0.12 m to 1.24 m) was observed at all sites above the mineral sediments. Despite these varied morphological conditions, all the pools have similar hydrological patterns throughout the year and these patterns are highly resilient to meteorological conditions. They dry out between the end of May and the end of July, rapid temporary refilling during important summer rainfall events, and partially refilling in autumn following more frequent rainfall events and lower evapotranspiration. The results show that surface water levels are maintained when the underlying sediments are saturated. Otherwise, the ephemeral pools lose water by infiltration to the underlying aquifer. Water level variations within the pools are positively and significantly correlated with net precipitation (P – PET). Hydroperiods vary between 28 days (2020) and 86 days (2017), reflecting the year-to-year meteorological variability. The mean hydroperiod is significantly correlated to spring rainfall (April to June), but also to the volume of water stored in the pool, and to the pool surface area. This study provides a unique and original dataset that contribute to better understand the hydrodynamics and resilience to anthropogenic (forestry) and natural (climate change) impacts of a wetland type that is rarely studied but provide crucial habitats for forest biodiversity.</p>

scholarly journals Comparison of random forests and other statistical methods for the prediction of lake water level: a case study of the Poyang Lake in China

2016 ◽  
Vol 47 (S1) ◽  
pp. 69-83 ◽  
Author(s):  
Bing Li ◽  
Guishan Yang ◽  
Rongrong Wan ◽  
Xue Dai ◽  
Yanhui Zhang
Keyword(s):  
Water Level ◽  
Random Forests ◽  
Lake Water ◽  
Poyang Lake ◽  
Time Lag ◽  
Water Levels ◽  
Support Vector ◽  
Lake Water Level ◽  
Water Level Variations

Modeling of hydrological time series is essential for sustainable development and management of lake water resources. This study aims to develop an efficient model for forecasting lake water level variations, exemplified by the Poyang Lake (China) case study. A random forests (RF) model was first applied and compared with artificial neural networks, support vector regression, and a linear model. Three scenarios were adopted to investigate the effect of time lag and previous water levels as model inputs for real-time forecasting. Variable importance was then analyzed to evaluate the influence of each predictor for water level variations. Results indicated that the RF model exhibits the best performance for daily forecasting in terms of root mean square error (RMSE) and coefficient of determination (R2). Moreover, the highest accuracy was achieved using discharge series at 4-day-ahead and the average water level over the previous week as model inputs, with an average RMSE of 0.25 m for five stations within the lake. In addition, the previous water level was the most efficient predictor for water level forecasting, followed by discharge from the Yangtze River. Based on the performance of the soft computing methods, RF can be calibrated to provide information or simulation scenarios for water management and decision-making.

scholarly journals Borehole water-level variations and implications for the subglacial hydraulics of South Cascade Glacier, Washington State, U.S.A.

1994 ◽  
Vol 40 (135) ◽  
pp. 293-304 ◽  
Author(s):  
Andrew G. Fountain
Keyword(s):  
Hydraulic Conductivity ◽  
Water Level ◽  
Water Flow ◽  
Washington State ◽  
Diurnal Variations ◽  
Water Levels ◽  
Seasonal Evolution ◽  
Borehole Water ◽  
Water Level Variations

AbstractBoreholes were drilled in South Cascade Glacier to investigate the hydraulics of subglacial water flow. Results indicate that subglacial water pressures are generally close to local ice-overburden pressures and that a subglacial debris layer probably exists. Calculations indicate that the range of hydraulic conductivity of this layer is 10−7-10−4m−1. The borehole water levels generally increased during the ablation season and may be caused by a seasonal evolution in the permeability of the debris layer. Water in the debris layer drains to a subglacial conduit, the existence of which is inferred by large diurnal variations in the water level of one borehole. These levels commonly reached the bottom of the glacier, indicating near-atmospheric pressures in the conduit.

scholarly journals EFFECTS OF WATER LEVEL VARIATIONS ON THE STABILITY OF ROCK ARMOURED SLOPES

2018 ◽  
pp. 44 ◽  
Author(s):  
Marcel R.A. Van Gent ◽  
Suzanna A.A. Zwanenburg ◽  
Jan Kramer
Keyword(s):  
Water Level ◽  
Physical Model ◽  
Model Tests ◽  
Water Levels ◽  
Level Variation ◽  
Water Level Variation ◽  
Stepwise Approach ◽  
Physical Model Tests ◽  
Water Level Variations ◽  
The Stability

Physical model tests on the stability of rock armoured slopes have been performed to demonstrate the importance of water level variations during a storm, due to a tide or a storm surge. For the stability of rock armoured slopes also the importance of the sequence of storms at various water levels has been studied. The test results indicate that a smooth sinusoidal water level variation leads to an increase in damage compared to the same wave conditions at a constant water level. Furthermore, a stepwise approach of the sinusoidal water level elevation leads to other results than the approach with a continuous water level variation, whereas the continuous water level variation resembles the peak of a storm or the tidal water level variation better than a stepwise approach. If storms with different water levels attack the armour layer, the damage is generally smaller than if all storms attack the armour layer at the same water level. Furthermore, the results have been discussed based on earlier analyses where the statistics of rock armoured slopes have been addressed and the importance of the length effect has been illustrated using a method to apply results from physical model tests to real structures.

scholarly journals Fluctuating water levels influence access to critical habitats for threatened Cowichan Lake lamprey

FACETS ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 488-502
Author(s):  
Chiranjib Chaudhuri ◽  
Joy Wade ◽  
Colin Robertson
Keyword(s):  
Water Level ◽  
Water Levels ◽  
Spawning Period ◽  
Habitat Area ◽  
Management Actions ◽  
Bear Lake ◽  
Aerial Vehicle ◽  
Key Drivers ◽  
Term Data

Cowichan Lake lamprey ( Entosphenus macrostomus) is a threatened species resident to Mesachie Lake, Cowichan Lake, and adjoining Bear Lake and their major tributaries in British Columbia. Decreases in trapping success have created concerns that the population is declining. Some potential threats include water use, climate change, and management actions. Owing to the absence of long-term data on population trends, little information is available to estimate habitat quality and factors that influence it. We sought to fill this gap by examining associations between habitat area and variables representing suspected key drivers of habitat availability. Critical habitat areas were imaged using an unmanned aerial vehicle over a period of three years at three sites at Cowichan Lake and a subsequent habitat area was classified. Meteorological and anthropogenic controls on habitat area were investigated through automatic relevance detection regression models. The major driver of habitat area during the critical spawning period was water level during the storage season, which also depends on the meteorological variables and anthropogenic control. It is recommended that regulation of the weir should aim to ensure that the water level remains above the 1 m mark, which roughly equates to the 67% coverage of water on the habitat area used for spawning.

scholarly journals Unmanned Aerial Vehicle with Thermal Imaging for Automating Water Status in Vineyard

2021 ◽  
Vol 3 (2) ◽  
pp. 79-91
Author(s):  
Subarna Shakya
Keyword(s):  
High Resolution ◽  
Water Level ◽  
Unmanned Aerial Vehicle ◽  
Thermal Imaging ◽  
Water Status ◽  
Water Levels ◽  
Agricultural Crop ◽  
Crop Water ◽  
Crop Water Stress Index ◽  
Aerial Vehicle

Thermal imaging is utilized as a technique in agricultural crop water management due to its efficiency in estimating canopy surface temperature and the ability to predict crop water levels. Thermal imaging was considered as a beneficial integration in Unmanned Aerial Vehicle (UAV) for agricultural and civil engineering purposes with the reduced weight of thermal imaging systems and increased resolution. When implemented on-site, this technique was able to address a number of difficulties, including estimation of water in the plant in farms or fields, while considering officially induced variability or naturally existing water level. The proposed effort aims to determine the amount of water content in a vineyard using the high-resolution thermal imaging. This research work has developed an unmanned aerial vehicle (UAV) that is particularly intended to display high-resolution images. This approach will be able to generate crop water stress index (CWSI) by utilizing a thermal imaging system on a clear-sky day. The measured values were compared to the estimated stomatal conductance (sg) and stem water (s) potential along the Vineyard at the same time. To evaluate the performance of the proposed work, special modelling approach was used to identify the pattern of variation in water level. Based on the observation, it was concluded that both ‘sg’ and ‘s’ value have correlated well with the CWSI value by indicating a great potential to monitor instantaneous changes in water level. However, based on seasonal changes in water status, it was discovered that the recorded thermal images did not correspond to seasonal variations in water status.

scholarly journals Dynamics of fortnightly water level variations along a tide-dominated estuary with negligible river discharge

Ocean Science ◽  
2021 ◽  
Vol 17 (6) ◽  
pp. 1605-1621
Author(s):  
Erwan Garel ◽  
Ping Zhang ◽  
Huayang Cai
Keyword(s):  
Water Level ◽  
River Discharge ◽  
Mean Amplitude ◽  
Water Levels ◽  
Level Increase ◽  
Upstream Direction ◽  
Water Level Variations ◽  
Mean Water Level ◽  
The Mean ◽  
Guadiana Estuary

Abstract. Observations indicate that the fortnightly fluctuations in the mean amplitude of water level increase in the upstream direction along the lower half of a tide-dominated estuary (the Guadiana Estuary), with negligible river discharge, but remain constant upstream. Analytical solutions reproducing the semi-diurnal wave propagation shows that this pattern results from reflection effects at the estuary head. The phase difference between velocity and elevation increases from the mouth to the head (where the wave has a standing nature) as the timing of high and low water levels come progressively closer to slack water. Thus, the tidal (flood–ebb) asymmetry in discharge is reduced in the upstream direction. It becomes negligible along the upper estuary half as the mean sea level remains constant despite increased friction due to wave shoaling. Observations of a flat mean water level along a significant portion of an upper estuary suggest a standing wave character and, thus, indicate significant reflection of the propagating semi-diurnal wave at the head. Details of the analytical model show that changes in the mean depth or length of semi-arid estuaries, in particular for macrotidal locations, affect the fortnightly tide amplitude and, thus, the upstream mass transport and inundation regime. This has significant potential impacts on the estuarine environment in terms of ecosystem management.

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