scholarly journals Evapotranspiration Partitioning and Response to Abnormally Low Water Levels in a Floodplain Wetland in China

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Xiaosong Zhao ◽  
Yuanbo Liu
Keyword(s):  
Water Level ◽  
Land Surface ◽  
Water Budget ◽  
Poyang Lake ◽  
Meteorological Data ◽  
Partition Ratio ◽  
Water Levels ◽  
Water Evaporation ◽  
Floodplain Wetland ◽  
Wetland Water

Evapotranspiration (ET) is an important component of the wetland water budget. Water level declines in Poyang Lake, the largest freshwater lake in China, have caused concerns, especially during low water levels. However, how wetland ET and its partitioning respond to abnormally low water levels is unclear. In this study, wetland ET was estimated with MODIS data and meteorological data. The wetland ET partitioning and its relationship with abnormally low water levels were analyzed for 2000–2013. The results showed that the water evaporation rate (Ewater) was larger than the land ET rate (ETland); theETland/Ewaterranged from 0.77 to 0.99. When the water level was below 12.8 m, the ET partition ratio was larger than 1, which indicates that wetland ET comes from land surface ET more than water evaporation. The negative standardized water level index (SWI) was used to represent an abnormally low water level in the wetland. Although the monthly wetland ET decreased as the negative SWI decreased,ETlandwas higher than the average under negative SWI conditions from September to December, when the water level decreased. The abnormally low water level induced more water loss from the land surface, especially when the water level decreased, which reduced the available water resources along the wetland shore.

scholarly journals Regulation of Vegetation and Evapotranspiration by Water Level Fluctuation in Shallow Lakes

Water ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 2651
Author(s):  
Qiang Liu ◽  
Liqiao Liang ◽  
Xiaomin Yuan ◽  
Sirui Yan ◽  
Miao Li ◽  
...  
Keyword(s):  
Water Level ◽  
Open Water ◽  
Water Area ◽  
Water Level Fluctuation ◽  
Water Levels ◽  
Water Level Fluctuations ◽  
Water Evaporation ◽  
Level Fluctuation ◽  
Open Water Area ◽  
Annual Scale

Water level fluctuations play a critical role in regulating vegetation distribution, composition, cover and richness, which ultimately affect evapotranspiration. In this study, we first explore water level fluctuations and associated impacts on vegetation, after which we assess evapotranspiration (ET) under different water levels. The normalized difference vegetation index (NDVI) was used to estimate the fractional vegetation cover (Fv), while topography- and vegetation-based surface-energy partitioning algorithms (TVET model) and potential evaporation (Ev) were used to calculate ET and water evaporation (Ep). Results show that: (1) water levels were dramatically affected by the combined effect of ecological water transfer and climate change and exhibited significant decreasing trends with a slope of −0.011 m a−2; and (2) as predicted, there was a correlation between water level fluctuation at an annual scale with Phragmites australis (P. australis) cover and open-water area. Water levels also had a controlling effect on Fv values, an increase in annual water levels first increasing and then decreasing Fv. However, a negative correlation was found between Fv values and water levels during initial plant growth stages. (iii) ET, which varied under different water levels at an annual scale, showed different partition into transpiration from P. australis and evaporation from open-water area and soil with alterations between vegetation and open water. All findings indicated that water level fluctuations controlled biological and ecological processes, and their structural and functional characteristics. This study consequently recommends that specifically-focused ecological water regulations (e.g., duration, timing, frequency) should be enacted to maintain the integrity of wetland ecosystems for wetland restoration.

scholarly journals Evidences of hydraulic relationships between groundwater and lake water across the large floodplain wetland of Poyang Lake, China

2017 ◽  
Vol 18 (2) ◽  
pp. 698-712 ◽  
Author(s):  
Yunliang Li ◽  
Jing Yao ◽  
Guizhang Zhao ◽  
Qi Zhang
Keyword(s):  
Water Level ◽  
Lake Water ◽  
Poyang Lake ◽  
Spatial And Temporal Variability ◽  
Floodplain Wetland ◽  
Lake Water Level ◽  
Groundwater Dynamics ◽  
Isotope Evidence ◽  
To Receive ◽  
Poyang Lake Wetland

Abstract Hydraulic relationship between wetlands and lakes has become an important topic for the scientific and decision-making communities. Poyang Lake, an open freshwater lake in China, and the extensive floodplain wetland surrounding the lake, plays an important role in protecting the biodiversity of this internationally recognized wetland system. This paper is the first field-based study into an investigation of the groundwater dynamics in the floodplain wetland and the associated hydraulic relationship with the lake using hydrological, hydrochemical and stable isotope evidence, as exemplified by Poyang Lake wetland. Results show that groundwater stores within the floodplain wetland exhibit spatial and temporal variability in terms of the magnitudes of groundwater level variations. Floodplain groundwater fluctuations largely reflect patterns of the precipitation and the lake water level; however, the groundwater dynamics are highly affected by the variations in the lake water level, rather than local precipitation. Floodplain wetland is most likely to receive the lake water during spring and summer and may recharge the lake during periods of low lake water level. Additionally, floodplain groundwater displays similar hydrochemical and environmental isotope signatures to that of the lake at different sampling periods, indicating a close hydraulic relationship between groundwater and the lake throughout the year.

scholarly journals Water-level attenuation in broad-scale assessments of exposure to coastal flooding: a sensitivity analysis

2018 ◽  
Author(s):  
Athanasios T. Vafeidis ◽  
Mark Schuerch ◽  
Claudia Wolff ◽  
Tom Spencer ◽  
Jan L. Merkens ◽  
...  
Keyword(s):  
Water Level ◽  
Flood Risk ◽  
Land Surface ◽  
Surface Characteristics ◽  
Water Levels ◽  
Risk Indicators ◽  
Population Exposure ◽  
Modelling Framework ◽  
Complex Interactions ◽  
Flood Exposure

Abstract. This study explores the uncertainty introduced in global assessments of coastal flood exposure and risk when not accounting for water level attenuation due to land-surface characteristics. We implement a range of plausible water-level attenuation values for characteristic land-cover classes in the flood module of the Dynamic and Integrated Vulnerability Assessment (DIVA) modelling framework and assess the sensitivity of flood exposure and flood risk indicators to differences in attenuation rates. Results show a reduction of up to 47 % in area exposure and even larger reductions in population exposure and expected flood damages when considering water level attenuation. The reductions vary by country, reflecting the differences in the physical characteristics of the floodplain as well as in the spatial distribution of people and assets in coastal regions. We find that uncertainties related to not accounting for water attenuation in global assessments of flood risk are of similar magnitude to the uncertainties related to the amount of SLR expected over the 21st century. Despite using simplified assumptions to account for the process of water level attenuation, which depends on numerous factors and their complex interactions, our results strongly suggest that an improved understanding and representation of the temporal and spatial variation of water levels across floodplains is essential for future impact modelling.

scholarly journals EXTREME WATER LEVEL EXCEEDANCE PROBABILITIES AROUND AUSTRALIA

2012 ◽  
Vol 1 (33) ◽  
pp. 53
Author(s):  
Leigh MacPherson ◽  
Ivan David Haigh ◽  
Matthew Mason ◽  
Sarath Wijeratne ◽  
Charitha Pattiaratchi ◽  
...  
Keyword(s):  
Tropical Cyclone ◽  
Water Level ◽  
Return Period ◽  
Meteorological Data ◽  
Storm Surges ◽  
Value Theory ◽  
Water Levels ◽  
Sea Levels ◽  
Extreme Water Level ◽  
Extreme Water Levels

The potential impacts of extreme water level events on our coasts are increasing as populations grow and sea levels rise. To better prepare for the future, coastal engineers and managers need accurate estimates of average exceedance probabilities for extreme water levels. In this paper, we estimate present day probabilities of extreme water levels around the entire coastline of Australia. Tides and storm surges generated by extra-tropical storms were included by creating a 61-year (1949-2009) hindcast of water levels using a high resolution depth averaged hydrodynamic model driven with meteorological data from a global reanalysis. Tropical cyclone-induced surges were included through numerical modelling of a database of synthetic tropical cyclones equivalent to 10,000 years of cyclone activity around Australia. Predicted water level data was analysed using extreme value theory to construct return period curves for both the water level hindcast and synthetic tropical cyclone modelling. These return period curves were then combined by taking the highest water level at each return period.

scholarly journals Study on the Causes of the Decline of the Low Water Levels of Poyang Lake, China

2019 ◽  
Vol 117 ◽  
pp. 00014
Author(s):  
Jian-Zhao Guan ◽  
Lei Zhang ◽  
Chun-Ming Fang ◽  
Jun Feng
Keyword(s):  
Water Level ◽  
Poyang Lake ◽  
Dominant Role ◽  
Water Environment ◽  
River Channel ◽  
Water Levels ◽  
Sand Mining ◽  
Channel Erosion ◽  
Main River Channel ◽  
Water Level Decline

The drastic decline in the water level of Poyang Lake during the dry season has close connection with the water environment and lake ecology. The drastic decline has attracted considerable attention, and has led to intense scientific discussions regarding its cause. However, the importance of the different causes of the low water level decline has not been clearly illustrated. To improve the understanding of the reasons for the decline of low water levels in the Poyang Lake Waterway, this paper investigated the contributions of river channel erosion and sand mining to the water level decline. The results show that sand mining mainly occurred on the beaches of the Waterway, and had a relatively small effect on the change in the shape of the main river channel. It was found that the contribution of sand mining to the decline in the low water level was no more than 30%, while the average contribution by natural erosion was about 85%. This indicates that natural channel erosion of the Waterway has been significant, and plays a dominant role in the declining water levels of the Waterway.

Changes in hydrologic conditions in the Dixie Valley and Fairview Valley areas, Nevada, after the earthquake of December 16, 1954

1957 ◽  
Vol 47 (4) ◽  
pp. 387-396
Author(s):  
C. P. Zones
Keyword(s):  
Ground Water ◽  
Water Level ◽  
Land Surface ◽  
Water Levels ◽  
Temporary Increase ◽  
Valley Fill ◽  
Dixie Valley ◽  
Main Fault ◽  
Hydrologic Conditions ◽  
Total Discharge

abstract The earthquake of December 16, 1954, affected hydrologic conditions in the Dixie Valley and Fairview Valley areas, Nevada. In Dixie Valley the rate of flow of water from wells was temporarily increased and water flowed for more than a month from several wells that had not flowed before. Water levels in wells were higher after the earthquake, but the trend of water levels since the earthquake has varied locally. There is no evidence that ground-water temperatures were affected. The flow of Mud Springs, which is on the main fault on the west side of Dixie Valley, increased substantially immediately after the earthquake, but since has decreased to essentially its pre-earthquake rate. The water level in Fairview Valley was about 4 feet higher after the earthquake. In East Gate Valley and at West Gate, ground-water levels were lower after the earthquake. In June, 1956, the water level in East Gate Valley was 34 feet lower than the pre-earthquake level. At West Gate the water level was about 9 feet lower. In Stingaree Valley the water level began to rise after an initial decline and reached a peak about 11 feet higher than the pre-earthquake level. Possible causes for the rise in ground-water levels in Dixie and Fairview Valleys include tilting of the confined and semiconfined aquifers in the valleys, compaction of the sediments of the valley fill, and increased upward leakage of ground water. It is possible that opening of new fractures and widening of pre-existing fractures in the bedrock between East Gate, Cowkick, and Stingaree valleys has accelerated the rate of movement of ground water between those valleys. The temporary increase in the flow of water from Mud Springs may be due to the opening of fractures in the fault zone along which the water is rising, or to a possible lowering of the land surface at the springs with a resulting increase in artesian head at the spring orifices. It is thought that any increase in the total discharge of ground water in the Dixie Valley and Fairview Valley areas is temporary because the increased discharge is probably from ground-water storage.

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.

Lake Mead and Hoover Dam monitoring in Nevada and Arizona states, USA using InSAR

2020 ◽  
Author(s):  
Mehdi Darvishi ◽  
Georgia Destouni ◽  
Fernando Jaramillo
Keyword(s):  
Los Angeles ◽  
Water Level ◽  
Land Surface ◽  
Ground Deformation ◽  
The United States ◽  
Water Levels ◽  
Lake Mead ◽  
Water Level Changes ◽  
Hoover Dam ◽  
The Impact

<p>Man-made reservoirs and lakes are key elements in the terrestrial water system. The increased concern about the impact of anthropogenic interventions on and the dynamics of these water resources has given rise to various approaches for representing human-water interactions in land surface models. Synthetic aperture radar interferometry (InSAR) has become a powerful geodetic tool for this purpose, by evidencing changes of ground and water surfaces across time and space. In this research, the Lake Mead and associated Hoover Dam are studied using Small Baseline Subset (SBAS) technique. Lake Mead is the largest reservoir in the United States, in terms of water capacity, supplies water and hydropower for millions of people in Las Vegas, Los Angeles and southwestern part of the USA. In recent years, rising temperature, increasing evaporation and decreasing precipitation have decreased water levels substantially, and probably modified its surrounding groundwater and surface as well.</p><p>This study aims to identify a hydrology-induced ground deformation around the lake Mead and a probable Hoover dam movement displacement. For the reservoir, we used the SBAS technique using 138 SAR data, including ERS1/2, Envisat, ALOS PALSAR and Sentinel-1, covering a time-spam between 1995 and 2019. For the analysis on the dam, we used the SBAS technique from 2014 to 2019 with descending and ascending modes of Sentinel-1A/B imageries. We found two main deformation patterns around the lake associated with the water level changes. Firstly, ERS and Sentinel-1 data evidenced a ground deformation that manifested itself as as a subsidence pattern in 1995 that has gradually changed into an uplift up to 2019. Secondly, the correlation trend between the deformation and water level changes has changed from negative to positive, with a transition point around March 2008. A possible interpretation for this is that the ground has initially reacted to the water fluctuations in the reservoir before March 2008 but after no longer plays a dominant role in the deformation occurring around the lake. The findings will help us to have a better understanding over the changes happened around the lake due to the water level changes and provide the valuable information for more effective management and maintenance of hydraulic structures and facilities near by the lake and water control in the future.</p>

Groundwater modelling for time periods of up to hundreds of thousands of years.

2020 ◽  
Author(s):  
Gerrit H. de Rooij ◽  
Thomas Mueller
Keyword(s):  
Surface Water ◽  
Water Level ◽  
Coastal Plain ◽  
Land Surface ◽  
Hydraulic Head ◽  
Water Levels ◽  
Analytical Models ◽  
Time Interval ◽  
Mountain Range ◽  
Time Step

<p>Occasionally, there is an interest in groundwater flows over many millennia. The input parameter requirement of numerical groundwater flow models and their calculation times limit their usefulness for such studies.</p><p>Analytical models require considerable simplifications of the properties and geometry of aquifers and of the forcings. On the other hand, they do not appear to have an inherent limitation on the duration of the simulated period. The simplest models have explicit solutions, meaning that the hydraulic head at a given time and location can be calculated directly, without the need to incrementally iterate through the entire preceding time period like their numerical counterparts.</p><p>We developed an analytical solution for a simple aquifer geometry: a strip aquifer between a no flow boundary and a body of surface water with a prescribed water level. This simplicity permitted flexible forcings: The non-uniform initial hydraulic head in the aquifer is arbitrary and the surface water level can vary arbitrarily with time. Aquifer recharge must be uniform in space but can also vary arbitrarily with time.</p><p>We also developed a modification that verifies after prescribed and constant time intervals if the hydraulic head is such that the land surface is covered with water. This excess water then infiltrates in areas where the groundwater level is below the surface and the remainder is discharged into the surface water. The hydraulic head across the aquifer is modified accordingly and used as the initial condition for the next time interval. This modification models the development of a river network during dry periods. The increased flexibility of the model comes at the price of the need to go through the entire simulation period one time step at a time. For very long time records, these intervals will typically be one year.</p><p>Given the uncertainty of the aquifer parameters and the forcings, the models are expected to be used in a stochastic framework. We are therefore working on a shell that accepts multiple values for each parameter as well as multiple scenarios of surface water levels and groundwater recharge rates, along with an estimate of their probabilities. The shell will generate all possible resulting combinations, the number of which can easily exceed 10000, then runs the model for each combination, and computes statistics of the average hydraulic head and the aquifer discharge into the surface water at user-specified times.</p><p>A case study will tell if this endeavor is viable. We will model the aquifer below the mountain range north of Salalah in Oman, which separates the desert of the Arabian Peninsula from the coastal plain at its southern shore. Rainfall estimates from the isotopic composition of stalactites in the area indicate distinct dry and wet periods in the past 300 000 years. In combination with estimated sea level fluctuations over that period, this provides an interesting combination of forcings. We examine the dynamics of the total amount of water stored in the aquifer, and of the outflow of water from the aquifer into the coastal plain.</p>

scholarly journals Integrated model projections of climate change impacts on water-level dynamics in the large Poyang Lake (China)

2019 ◽  
Author(s):  
Yunliang Li ◽  
Qi Zhang ◽  
Hui Tao ◽  
Jing Yao
Keyword(s):  
Climate Change ◽  
Water Level ◽  
Lake Water ◽  
Hydrological Model ◽  
Poyang Lake ◽  
Baseline Period ◽  
Global Climate Models ◽  
Water Levels ◽  
Future Climate Change ◽  
Increased Risk

Abstract This study outlines a framework for examining potential impacts of future climate change in Poyang Lake water levels using linked models. The catchment hydrological model (WATLAC) was used to simulate river runoffs from a baseline period (1986–2005) and near-future (2020–2035) climate scenarios based on eight global climate models (GCMs). Outputs from the hydrological model combined with the Yangtze River's effects were fed into a lake water-level model, developing in the back-propagation neural network. Model projections indicate that spring–summer water levels of Poyang Lake are expected to increase by 5–25%, and autumn–winter water levels are likely to be lower and decrease by 5–30%, relative to the baseline period. This amounts to higher lake water levels by as much as 2 m in flood seasons and lower water levels in dry seasons in the range of 0.1–1.3 m, indicating that the lake may be wet-get-wetter and dry-get-drier. The probability of occurrence for both the extreme high and low water levels may exhibit obviously increasing trends by up to 5% more than at present, indicating an increased risk in the severity of lake floods and droughts. Projected changes also include possible shifts in the timing and magnitude of the lake water levels.

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