scholarly journals Flow Division Dynamics in the Mekong Delta: Application of a 1D-2D Coupled Model

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 837 ◽  
Author(s):  
Sepehr Eslami ◽  
Piet Hoekstra ◽  
Herman Kernkamp ◽  
Nam Nguyen Trung ◽  
Duc ◽  
...  
Keyword(s):  
Water Level ◽  
Irrigation System ◽  
Mekong Delta ◽  
Dry Season ◽  
Offshore Wind ◽  
Water Volume ◽  
Estuarine System ◽  
Tidal Amplitude ◽  
Tidal Dynamics ◽  
Salt Intrusion

The Mekong Delta constitutes a complicated multi-channel estuarine system, exchanging water with a delta-wide irrigation system. A 1D–2DH coupled numerical domain is calibrated and validated for water level and discharge during the dry season. This approach benefits from the simplicity of a 1D network within the estuarine and irrigation systems, while maintaining the interaction with the spatial tidal dynamics of the 2DH coastal domain. First, the role of the irrigation system on tidal dynamics is quantified; then, tidal propagation, freshwater budget, and the effect of offshore subtidal water level on discharge division are investigated. The results show that the complex irrigation system, in a friction-like manner, reduces the tidal amplitude up to 25%. The channels aggregate to 1% of the total water volume in the delta, while accommodating up to 10% of the tidal prism. Tidal amplitude reduces upstream, while subtidal water level is highly sensitive to upstream discharge, spring–neap cycles, and wind-generated offshore surge. Although cumulative discharge division within the estuarine network is consistent, temporal discharge division can be significantly sensitive to offshore wind-surge. During the dry season, it can reverse the expected subtidal discharge division within the time-scale of a few days and potentially influence salt intrusion.

scholarly journals PERENCANAAN EMBUNG GUWOREJO KECAMATAN TAROKAN KABUPATEN KEDIRI

2019 ◽  
Vol 12 (1) ◽  
pp. 59
Author(s):  
Yuono Mugi Kuncoro ◽  
Djoko Trijanto ◽  
Medi Efendi
Keyword(s):  
Water Level ◽  
Dry Season ◽  
Topographic Maps ◽  
Effective Capacity ◽  
Water Volume ◽  
Capacity Analysis ◽  
Flood Water ◽  
Initial Design ◽  
Hydrologic Analysis ◽  
Downstream Slope

In dry season Tarokan Sub-district of Kediri, often suffers from drought, so a small dam (embung) was required. The objectives of the study are to determine the dimension of the dam, its spillway and to analyze its stability. The required data were of rainfall, topographic maps, soil, and population.The initial design was hydrologic analysis by finding out the planned discharge Q50 and determining the water volume of inflow. To determine the effective catchment ponds, capacity analysis using topographical data and comparing the volume of water available. And analysis of spillway to determine the flood water level.The analyses result, the amount of the water needs of a population of 258.854.400m3, and the magnitude of the draft Q50 discharge of in 4.027 m3/sec (The  room  for  sediment  is  29,234.9 m3  at  elevation  1 m from the bottom of the pool); 390,000m3 effective capacity at +131.75 elevation, and flood water level at +132.75 elevation. The dimension of embung main dam is 6 m deep; embung crest at +133.00 elevation ; 3m wide embung crest ; 1:3 upstream slope; 1 : 2.25 downstream slope ; 10 m wide spillway channel 1 : 1 slope of wall of spillway channel ; and crest of spillway at +131.75. Geostudio software was used to calculate the figures safety against sliding. Keywords: embung, spillway, embung dimensions, slope stabilty

scholarly journals Dynamics of salt intrusion in the Mekong Delta: results of field observations and integrated coastal–inland modelling

2021 ◽  
Vol 9 (4) ◽  
pp. 953-976
Author(s):  
Sepehr Eslami ◽  
Piet Hoekstra ◽  
Herman W. J. Kernkamp ◽  
Nam Nguyen Trung ◽  
Dung Do Duc ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Saline Water ◽  
Water System ◽  
Mekong Delta ◽  
Hydrological Regime ◽  
Salt Transport ◽  
Mixed System ◽  
Estuarine System ◽  
Salt Intrusion ◽  
Numerical Domain

Abstract. On the list of challenges facing the world largest deltas, increased saline water intrusion (SWI) in the surface water system and its role in jeopardizing freshwater supply are often ranked very high. Yet, detailed process-based studies of SWI at the whole delta scale are limited, and the trends are regularly associated with global sea level rise. Here, using field measurements and a sophisticated 3D model that integrates the riverine, rural, estuarine, and coastal dynamics within one numerical domain, we study SWI at the scale of the Mekong Delta in extensive detail. While many studies downscale the SWI problem to a topic within an estuary, we show that the physical processes on the continental shelf, such as monsoon-driven ocean surge, directly influence salinity dynamics within the delta. Typical values of 20–40 cm surge over the continental shelf contribute to up to 10 km of further SWI. The delta's estuarine system is also more sensitive than many other systems to variations of river discharge. Furthermore, spring–neap variability plays a key role in SWI in the delta. The estuarine variability from a stratified to a mixed system between neap and spring tides develops 3D processes such as estuarine circulation and tidal straining that become the main upstream salt transport mechanisms. The 3D nature of salinity dynamics, and the role of upstream and downstream processes, suggests that compromising on dimension or extent of the numerical domain can limit the accuracy of predictions of SWI in the delta. The study also showcases the fact that riverbed incision in response to anthropogenic sediment starvation in the last 2 decades has increased stratification and activated or magnified 3D salt transport subprocesses that amplify upstream salt transport. With all the external forces on the delta, namely climate change and an altered hydrological regime by the upstream dams, due to deeper estuarine channels (driven by sand mining and upstream impoundments) compared to its near past, the delta itself has become far more vulnerable to even mild natural events. This exemplifies the fundamental importance of preserving the sediment budget and riverbed levels in protecting the world's deltas against SWI.

The Response of Salinity in Dry Season to Vertical Circulation in the Modaomen Estuary of the Pearl River, China

2012 ◽  
Vol 518-523 ◽  
pp. 4574-4577
Author(s):  
Xiao Ling Yin ◽  
Dong Lin Bai ◽  
Li Cheng Li
Keyword(s):  
Water Level ◽  
River Flow ◽  
Lower Layer ◽  
Field Measurements ◽  
Dry Season ◽  
Pearl River ◽  
Salt Intrusion ◽  
Modaomen Estuary ◽  
Coastal Sea ◽  
The Pearl River

In recent years, salt intrusion in estuaries of the Pearl River has become a serious problem for local water supply in dry season. Water level, circulation and salinity around mouth of the Modaomen estuary in spring and neap were examined respectively through field measurements. The results indicated that mild water level process reinforced baroclinic action to cause notable circulation downstream, which was more durable in neap. And, the current in lower layer was generally faster than that in upper layer during the neap circulation. These two probably resulted in higher bottom salinity in neap than in spring within the upper mouth, which was on the contrary to the lower mouth as well as the open coastal sea nearby. The activity of observed salt wedge by tidal force within the lower mouth contributed to local salinity variation. Thus, the saline processes and distributions in the estuary mouth depended on cooperation of estuarine circulation and tidal driving in the absence of river flow and wind.

scholarly journals Dynamics of salt intrusion in the Mekong Delta; results of field observations and integrated coastal-inland modelling

2021 ◽  
Author(s):  
Sepehr Eslami ◽  
Piet Hoekstra ◽  
Herman W. J. Kernkamp ◽  
Nam Nguyen Trung ◽  
Dung Do Duc ◽  
...  
Keyword(s):  
Continental Shelf ◽  
Mekong Delta ◽  
Hydrological Regime ◽  
Field Measurements ◽  
Salt Transport ◽  
Mixed System ◽  
Estuarine System ◽  
Salt Intrusion ◽  
External Forces ◽  
Numerical Domain

Abstract. In the list of challenges facing the world largest deltas, increased salt intrusion and its role in jeopardizing freshwater supply is often ranked very high. Yet, detailed process-based studies of salt intrusion at the whole delta scale are limited and the trends are regularly associated to global sea level rise. Here, using field measurements and a sophisticated 3D model that integrates the riverine, rural, estuarine, and coastal dynamics within one numerical domain, we study salt intrusion at the scale of the Mekong Delta in extensive detail. While many studies down-scale the salt intrusion problem to a topic within an estuary, we show that the continental shelf is an intrinsic component of the delta, and its physical processes, such as monsoon-driven ocean surge, directly influence salinity dynamics within the delta. Typical values of 20–40 cm surge over the continental shelf contribute to up to 10 km of further salt intrusion. The delta's estuarine system is also more sensitive than many other systems to upstream discharge variations. Furthermore, spring-neap variability plays a key role in salt intrusion in the delta. The estuarine variability from a stratified to a mixed system between neap and spring tides develops 3D processes such as estuarine circulation and tidal straining that become the main upstream salt transport mechanisms. The 3D nature of salinity dynamics, and the role of upstream and downstream processes, suggests that compromising on dimension or extent of the numerical domain, can limit the accuracy of predictions of salt intrusion in the delta. The study also showcases that riverbed incision in response to anthropogenic sediment starvation in the last two decades, has increased stratification, and activated or magnified 3D salt transport sub-processes that amplify upstream salt transport. With all the external forces on the delta namely climate change and altered hydrological regime by the upstream dams, due to deeper estuarine channels (driven by sand mining and upstream impoundments), the delta itself is far more vulnerable to even mild natural events. This exemplifies the fundamental importance of preserving the sediment budget and riverbed levels in protecting the world's deltas against salt intrusion.

CURRENT STATE OF SALT INTRUSION IN THE MEKONG DELTA IN VIETNAM

2020 ◽  
pp. 74-80
Author(s):  
Nguyen Thi Thuy Nhung Nguyen Thi Thuy Nhung ◽  
Keyword(s):  
Power Plants ◽  
Salt Water ◽  
High Tide ◽  
Mekong Delta ◽  
Dry Season ◽  
Mekong River ◽  
Circulation System ◽  
Deep Penetration ◽  
Hydroelectric Power ◽  
Salt Intrusion

The study aims to determine the evolution of salt intrusion in the Mekong Delta in Vietnam. Salt water appeared in the mouths of rivers many years ago, but its values in 2019-2020 are considered the highest in the history of observations and surpass the data of 2016 (the year with the highest salinity). In 2020, the phenomenon of salt invasion will strongly manifest itself in the Mekong Delta in Vietnam (in the lower reaches of the Mekong River), the penetration of salt water deep into the mainland and the marginal salinity of 4 (g/l) deeper than 5-25 km, depending on the range. The main reason for this is the change in the flow of water from the headwaters. During the dry season, the flow in the estuary is completely dependent on the flow of water from the upper Mekong River, and the construction of hydroelectric power plants affects the water content of the river below the dams. The second reason is the inefficient operation of the fresh water circulation system between rivers during the dry season in Vietnam. Some other causes are related to climate change, such as rising sea levels at high tide, which allows salt water to flow inland from the mouth, as well as a rather wide shape of the mouth and deep penetration into the land, which contributes to faster penetration. All this negatively affects the environment and sustainable economic development of the Mekong Delta in Viet Nam.

An assessment of the Dead Sea level change using remotely sensed data

2021 ◽  
Author(s):  
Musab Mbideen ◽  
Balázs Székely
Keyword(s):  
Remote Sensing ◽  
Water Level ◽  
Surface Area ◽  
Dead Sea ◽  
Spectral Radiance ◽  
Water Volume ◽  
Surface Model ◽  
Atmospheric Effects ◽  
Level 1 ◽  
The Dead

<p>Remote Sensing (RS) and Geographic Information System (GIS) instruments have spread rapidly in recent years to manage natural resources and monitor environmental changes. Remote sensing has a vast range of applications; one of them is lakes monitoring. The Dead Sea (DS) is subjected to very strong evaporation processes, leading to a remarkable shrinkage of its water level. The DS is being dried out due to a negative balance in its hydrological cycle during the last five decades. This research aims to study the spatial changes in the DS throughout the previous 48 years. Change detection technique has been performed to detect this change over the research period (1972-2020). 73 Landsat imageries have been used from four digital sensors; Landsat 1-5 MSS C1 Level-1, Landsat 4-5 TM C1 Level-1, Land sat 7 ETM+ C1  Level-1, and Landsat 8 OLI-TIRS C1 Level. After following certain selection criteria , the number of studied images decreased. Furthermore, the Digital Surface Model of the Space Shuttle Radar Topography Mission and a bathymetric map of the Dead Sea were used. The collected satellite imageries were pre-processed and normalized using ENVI 5.3 software by converting the Digital Number (DN) to spectral radiance, the spectral radiance was converted to apparent reflectance, atmospheric effects were removed, and finally, the black gaps were removed. It was important to distinguish between the DS lake and the surrounding area in order to have accurate results, this was done by performing classification techniques. The digital terrain model of the DS was used in ArcGIS (3D) to reconstruct the elevation of the shore lines. This model generated equations to detect the water level, surface area, and water volume of the DS. The results were compared to the bathymetric data as well. The research shows that the DS water level declined 65 m (1.35 m/a) in the studied period. The surface area and the water volume declined by 363.56 km<sup>2 </sup>(7.57 km<sup>2</sup>/a) and 53.56 km<sup>3</sup> (1.11 km<sup>3</sup>/a), respectively. The research also concluded that due to the bathymetry of the DS, the direction of this shrinkage is from the south to the north. We hypothesize that anthropogenic effects have contributed in the shrinkage of the DS more than the climate. The use of the DS water by both Israel and Jordan for industrial purposes is the main factor impacting the DS, another factor is the diversion of the Jordan and Yarmouk rivers. Our results also allow to give a prediction for the near future of the DS: the water level is expected to reach –445 m in 2050, while the surface area and the water volume is expected to be 455 km<sup>2</sup> and 142 km<sup>3</sup>, respectively. </p>

scholarly journals Description of the larva of Bromeliagrion rehni (Odonata: Coenagrionidae) with bionomic notes concerning its phytotelmic habitat in central Amazonas, Brazil

2008 ◽  
Vol 25 (3) ◽  
pp. 479-486 ◽  
Author(s):  
Sharlene R. da S. Torreias ◽  
Ulisses G. Neiss ◽  
Neusa Hamada ◽  
Ruth L. Ferreira-Keppler ◽  
Frederico A.A. Lencioni
Keyword(s):  
Rainy Season ◽  
Environmental Parameters ◽  
Dry Season ◽  
Stage Larva ◽  
Water Volume ◽  
Apical Region ◽  
Last Stage ◽  
First Time ◽  
The Relationship

The last-stage larva of Bromeliagrion rehni Garrison in De Marmels & Garrison, 2005 is described and illustrated and bionomics and habitat information on this species are provided. The study was conducted in the Reserva Florestal Adolpho Ducke, located near Manaus, state of Amazonas, Brazil.Twelve samplings were done between April, 2003 and April, 2005: six in the rainy season and six in the dry season. In each sampling month, 12 bromeliads (Guzmania brasiliensis Ule, 1907, Bromeliaceae) were collected, six of which were terrestrial and six epiphytic, yielding144 samples. A total of 75 specimens of B. rehni were collected. The relationship between larval B. rehni abundance and the measured environmental parameters (volume (ml), pH, season and stratum) was significant (ANCOVA, F = 5.296, d.f. = 130, p < 0.001). Larvae were most abundant in the rainy season (p < 0.01) and water volume was positively related to the abundance of B. rehni. Larvae of B. rehni can be distinguished from those of B. fernandezianum (the only species in the genus with described larvae) by the number of setae in the prementum and by the color of the apical region of the femur. The association of this species with phytotelmata of G. brasiliensis is reported here for the first time.

scholarly journals Design and Development of an Automatic Prototype Smart Irrigation Model

2021 ◽  
pp. 119-127
Keyword(s):  
Soil Moisture ◽  
Water Level ◽  
Irrigation System ◽  
Human Resources Management ◽  
Ultrasonic Sensor ◽  
Moisture Level ◽  
Moisture Sensor ◽  
Soil Moisture Level ◽  
Input Signals ◽  
Crop Field

In the current condition, it is difficult to increase plant development and reduce expenses in agricultural sectors; nevertheless, an advanced thought leads to the use of an automated model that introduces automation in the irrigation system, which can aid in improved water and human resources management. An automated model has been developed using sensors and microcontroller technology, to make the most efficient use of water supply for irrigation. A soil moisture content detector is inserted into the soil of the crops, and an ultrasonic sensor is placed above the soil of the crops to measure the water level after irrigation has begun. A C++ program with threshold values for the moisture sensor was used to start the system in the crop field depending on the soil moisture level, and an ultrasonic sensor was used to control the water in the crop field. The Arduino UNO board is a microcontroller inbuilt of Atmel in the mega AVR family (ATMega328) and the sensors were used to lead the model in turning ON/OFF. A microcontroller was included in this model to run the program by receiving sensor input signals and converting them to soil water content and water level values in the crop field. The microcontroller began by receiving input values, which resulted in an output instructing the relay to turn on the groundwater pump. An LCD screen has also been interfaced with the microcontroller to show the percentage of moisture in the soil, field water level, and pump condition. When the soil moisture level reaches 99 percent and the water level reaches 6 cm after 2.5 and 4 minutes, respectively, the pump is turned off. This model, according to the study, might save water, time, and reduce human effort.

scholarly journals Fertilizer for Sweet Pepper Under Drip Irrigation in an Oxisol in Northwestern Puerto Rico

1969 ◽  
Vol 65 (2) ◽  
pp. 123-128
Author(s):  
J. C. W. Keng ◽  
T. W. Scott ◽  
M. A. Lugo-López
Keyword(s):  
Drip Irrigation ◽  
Nutrient Management ◽  
Irrigation System ◽  
Sweet Pepper ◽  
Dry Season ◽  
Low Fertility ◽  
Wet Season ◽  
Promising Alternative ◽  
Broadcast Application ◽  
K Fertilizer

A drip irrigation system using porous plastic tubing was designed to study operational techniques of drip irrigation and fertilizer management in a highly weathered, leached, relatively low fertility, acid Oxisol. Sweet pepper (Capsicum annuum) was the test crop. All plots received an initial broadcast application of a 10-4.4-8.3 N-P-K fertilizer at the rate of 80 kg/ha. The experiment followed a randomized complete block layout with 4 treatments and 6 replications. The treatments were as follows: 1) N and K injected into the drip system, P banded; 2) banded N, P and K with drip irrigation; 3) broadcast N, P and K with drip irrigation; and 4) control-drip irrigation, no N, P and K other than the initial overall broadcast application. All treatments, except the control, received a total of 56.8 g of a 10-10-10 fertilizer per plant and all were uniformly drip irrigated according to pan evaporation data. Two crops were grown: one in the dry season and one in wet season. Yields were significantly different among all treatments for the dry season crop, with a high of 82.62 kg/ha for the treatments where Nand K were injected into the drip system and a low of 31.54 kg/ha for the control. For the wet season crop, no significant yield differences were found when fertilizer was injected into the drip system and when banded, but both these treatments were superior in yield to that of broadcast. These three treatments were superior to the control, with more than 100% increase. Drip irrigation is a promising alternative to currently used water-nutrient management methods for Oxisols in the wet-dry tropics.

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