scholarly journals Combined geoelectrical and geoelectromagnetic survey for contributing to local hydrogeological regime – The case study of Delfini basin (Chios isl. – Greece)

2020 ◽  
Author(s):  
Т.Д. Пападопулос ◽  
Дж.Д. Алексополус ◽  
С. Дилалос
Keyword(s):  
Water Potential ◽  
Fresh Water ◽  
Water Discharge ◽  
Geophysical Methods ◽  
Confined Aquifer ◽  
Lateral Extent ◽  
Alternative Water ◽  
Winter Time ◽  
Fresh Water Discharge ◽  
Summer Time

В данной статье исследуется механизм питания источников, распределенных вокруг широкой области Дельфини на северо-восточной стороне острова Хиос, в попытке найти возможные пути фильтрации пресных вод внутри острова, до того как они будут сброшены в море. Цель. Бурение гидрогеологических скважин для увеличения добычи имеет жизненно важное значение для удовлетворения потребностей в питьевой воде и ирригации широкой территории. Несмотря на то, что в последние годы на острове Хиос интенсивно бурятся скважины, потребность в дальнейших исследованиях связана с увеличением потребления воды в летнее время, с одной стороны, и неэффективностью альтернативных водных ресурсов (например, строительство плотин, опреснительных установок и т.д.), с другой стороны. Методы. Геофизические методы (низкочастотная электроразведка и удельное сопротивление) использовались для детального изучения областей водного потенциала, таких как наиболее широкая область Дельфини, где в зимнее время огромное количество пресной воды сбрасывается через источники до уровня моря. Результаты и их обсуждение. Наличие ограниченного водоносного горизонта, состоящего в основном из известняков, которые перекрыты обломочными непроницаемыми отложениями, а также наличие разрывных зон, несущих водный потенциал, определяют гидрогеологический режим близлежащего района. Это также объясняется наличием солоноватых вод на положительных высотах, обнаруженных в летнее время в близлежащих источниках. По-видимому, боковая протяженность непроницаемых обломочных отложений играет решающую роль, позволяя внутреннему стоку морской воды в летнее время и в сочетании с наличием ограниченного водоносного горизонта пресной воды создавать восходящий смешивающийся поток пресной и морской воды в источниках возвышенностей. В зимнее время огромное количество оттока пресной воды не позволяет внутреннему притоку морской воды In this paper the feeding mechanism of springs distributed around the broader area of Delfini at NE side of Chios Island is explored, in an effort to locate possible fresh water paths inland before they are discharged to the sea. The drilling of hydro wells for more production is of vital importance to cover the drinking and irrigation needs of the broader area. Aim. Although Chios has been extensively drilled in the past years the demand for further investigations comes from an increased water consumption during summer time in one hand and the inefficiency of alternative water resources (e.g. construction of dams, desalination units, etc) on the other hand. Methods. Geophysical methods were used (VLF and resistivity) to explore in detail water potential areas, like the broader area of Delfini, where during winter time huge quantities of fresh water discharge through springs to sea level. Results and its discussion. The presence of a confined aquifer composed mainly of limestones, which are overlain by clastic impermeable deposits, together with the existence of water potential bearing fracture zones determine the hydrogeological regime of the nearby area. It is also explained the presence of brackish waters at positive elevations found during summer time at nearby springs. It seems that the lateral extent of impermeable clastic deposits plays a crucial role in allowing the inland flow of seawater during summer time and combined with the presence of the confined aquifer of fresh water produce an upward mixing flow of fresh and seawater at springs of positive elevations. During winter time the huge amount of fresh water discharges do not allow the inland flow of seawater

scholarly journals Analytical approach for determining the mean water level profile in an estuary with substantial fresh water discharge

2016 ◽  
Vol 20 (3) ◽  
pp. 1177-1195 ◽  
Author(s):  
Huayang Cai ◽  
Hubert H. G. Savenije ◽  
Chenjuan Jiang ◽  
Lili Zhao ◽  
Qingshu Yang
Keyword(s):  
Water Level ◽  
Fresh Water ◽  
River Discharge ◽  
River Flow ◽  
Water Discharge ◽  
Value Theory ◽  
Velocity Amplitude ◽  
Mean Water Level ◽  
The Mean ◽  
Fresh Water Discharge

Abstract. The mean water level in estuaries rises in the landward direction due to a combination of the density gradient, the tidal asymmetry, and the backwater effect. This phenomenon is more prominent under an increase of the fresh water discharge, which strongly intensifies both the tidal asymmetry and the backwater effect. However, the interactions between tide and river flow and their individual contributions to the rise of the mean water level along the estuary are not yet completely understood. In this study, we adopt an analytical approach to describe the tidal wave propagation under the influence of substantial fresh water discharge, where the analytical solutions are obtained by solving a set of four implicit equations for the tidal damping, the velocity amplitude, the wave celerity, and the phase lag. The analytical model is used to quantify the contributions made by tide, river, and tide–river interaction to the water level slope along the estuary, which sheds new light on the generation of backwater due to tide–river interaction. Subsequently, the method is applied to the Yangtze estuary under a wide range of river discharge conditions where the influence of both tidal amplitude and fresh water discharge on the longitudinal variation of the mean tidal water level is explored. Analytical model results show that in the tide-dominated region the mean water level is mainly controlled by the tide–river interaction, while it is primarily determined by the river flow in the river-dominated region, which is in agreement with previous studies. Interestingly, we demonstrate that the effect of the tide alone is most important in the transitional zone, where the ratio of velocity amplitude to river flow velocity approaches unity. This has to do with the fact that the contribution of tidal flow, river flow, and tide–river interaction to the residual water level slope are all proportional to the square of the velocity scale. Finally, we show that, in combination with extreme-value theory (e.g. generalized extreme-value theory), the method may be used to obtain a first-order estimation of the frequency of extreme water levels relevant for water management and flood control. By presenting these analytical relations, we provide direct insight into the interaction between tide and river flow, which will be useful for the study of other estuaries that experience substantial river discharge in a tidal region.

scholarly journals SPECIES COMPOSITION AND DIVERSITY OF TIDAL TRAP NET CATCHES IN THE WATERS OF INDRAGIRI HILIR, RIAU, INDONESIA

2017 ◽  
Vol 7 (1) ◽  
pp. 47
Author(s):  
Badrudin Badrudin ◽  
Bambang Sumiono ◽  
T.S Murtoyo
Keyword(s):  
Species Composition ◽  
Fresh Water ◽  
Coastal Waters ◽  
Water Discharge ◽  
Fresh Water Discharge

The coastal waters of the eastern part of lndragiri Hilir, Riau, which are mostly estuarine, are influenced by the huge fresh water discharge and are usually fertile.

The tidal circulation and flushing capability of the outer Tay Estuary

1980 ◽  
Vol 78 (3-4) ◽  
pp. s33-s46
Author(s):  
J. A. Charlton
Keyword(s):  
Exchange Rate ◽  
Fresh Water ◽  
Water Discharge ◽  
Hydraulic Model ◽  
Tidal Currents ◽  
Tidal Circulation ◽  
Fresh Water Discharge ◽  
Outer Estuary ◽  
Tay Estuary

SynopsisMeasurements of tidal currents in the outer Tay Estuary, and from the hydraulic model of the estuary, are used to present a tidal atlas of the area and to deduce residual tidal circulation. Additional tests on the model show that the volumetric exchange rate with the sea of the outer estuary can be as high as 58 per cent per tide, but may be lowered to about 35 per cent if multiple tide recirculation is considered. Fresh water discharge into the estuary does not materially affect this exchange rate.

Evidence of the recent decade change in global fresh water discharge and evapotranspiration revealed by reanalysis and satellite observations

2012 ◽  
Vol 48 (2) ◽  
pp. 153-158 ◽  
Author(s):  
Ki-Weon Seo ◽  
Duane E. Waliser ◽  
Baijun Tian ◽  
Baek-Min Kim ◽  
Seong-Chan Park ◽  
...  
Keyword(s):  
Fresh Water ◽  
Water Discharge ◽  
Recent Decade ◽  
Satellite Observations ◽  
Fresh Water Discharge

Prediction of salinity intrusion in Danshuei estuarine system

2008 ◽  
Vol 39 (5-6) ◽  
pp. 497-505 ◽  
Author(s):  
A. Etemad-Shahidi ◽  
A. Dorostkar ◽  
Wen-Cheng Liu
Keyword(s):  
Fresh Water ◽  
Water Discharge ◽  
Eddy Diffusivity ◽  
Turbulence Closure ◽  
Estuarine System ◽  
Salinity Intrusion ◽  
Closure Scheme ◽  
Fresh Water Discharge ◽  
Vertical Eddy Diffusivity ◽  
Vertical Eddy

The main parameters that affect the flow conditions and intrusion of salt water in an estuary system are tides and the seasonal variation of water discharge. A laterally averaged two-dimensional numerical model called MIKE 11 XZ is used to simulate the hydrodynamics and salinity intrusion of Danshuei River estuarine system. This model can simulate hydrodynamics and water quality in estuaries, reservoirs and lakes. MIKE 11 XZ solves the Reynolds-averaged Navier–Stokes equations by using Abbott–Ionescu finite difference scheme in a non-dimensional vertical σ-coordinate. Vertical eddy diffusivity in the model can be determined by a constant value, a mixing length theory and a k or k−ɛ turbulence closure scheme with Richardson number correction. A series of comprehensive field data obtained from Danshuei estuarine system is used for evaluation, calibration and verification of the model. The friction coefficient was calibrated and verified using water surface elevation and velocity measurements, respectively. Then the vertical eddy diffusivity was calibrated and verified through comparison of salinity measurements in different layers of several stations. Reasonable agreement was obtained between the model results and the observed data using k−ɛ turbulence closure scheme. The model application was investigated with different discharges and the effect of discharge variation on salinity intrusion was determined. The results showed that the fresh water discharge is the main parameter that affects the salinity intrusion in this system. Finally, simple power equations are suggested to predict the salinity intrusion due to the fresh water discharge in different tributaries of the system.

Some Aspects of the Ecology of Lake Macquarie, N.S.W., with Regard to an Alleged Depletion of Fish. II. Hydrology

1959 ◽  
Vol 10 (3) ◽  
pp. 279 ◽  
Author(s):  
RS Spencer
Keyword(s):  
Sea Level ◽  
Fresh Water ◽  
Oxygen Tension ◽  
Heavy Rainfall ◽  
Salt Water ◽  
Water Discharge ◽  
Narrow Channel ◽  
Mean Sea Level ◽  
Lake Temperature ◽  
Fresh Water Discharge

Lake Macquarie is a marine-dominated drowned valley connected to the sea by a shallow narrow channel which damps tidal oscillations from 5 ft on the coast outside to about 3 in. in the like. Superimposed on the semi-diurnal tides are changes in level in response to changes both in the external daily mean sea-level and in the volume of fresh water discharge into the lake. Temperature and chlorinity cycles are closely linked. Discharge from the creeks supplies phosphate but little nitrate for the lake. Prolonged heavy rainfall in both 1955 and 1956 produced stratification of the water associated with lowered oxygen tension in the underlying salt water. There is evidence of a wind-generated circulation within the lake.

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