Water Table Uncertainties due to Uncertainties in Structure and Properties of an Unconfined Aquifer

Ground Water ◽  
2017 ◽  
Vol 56 (2) ◽  
pp. 251-265
Author(s):  
Juerg Hauser ◽  
Florian Wellmann ◽  
Mike Trefry
Keyword(s):  
Water Table ◽  
Unconfined Aquifer ◽  
Structure And Properties

scholarly journals Relevance of topographic control on hydrogeological properties of the weathered granite gneiss aquifer in watershed perspective -- Usri sub-basin, Giridih, India

2020 ◽  
Author(s):  
Ashok Kumar
Keyword(s):  
Water Table ◽  
Geographical Area ◽  
Ground Surface ◽  
Granite Gneiss ◽  
Unconfined Aquifer ◽  
Aquifer System ◽  
Northern Margin ◽  
Topographic Features ◽  
Basin Water ◽  
Basement Surface

Usri, a southward sloping fourth order drainage sub-basin of Barakar river, is located in the northern margin of Chhotanagpur plateau, Giridih, India. Gently sloping undulating landforms devoid of hills and outcrops is main characteristics of this sub-basin. Topographic elevation varies between 310 to 390 m MSL. Geographically it is located between lat 24.38° N to 24.54° N long and 86.07° E and 86.28° E longitudes. Thick weathered horizon developed over homogenous Archean granite-gneiss is the principal unconfined aquifer system. Basement topographic (weathering depth) and water table have been correlated with the surface topographic features (landforms). Presence of considerably thick weathered horizons, devoid of rock exposures, regional uniformity in geomorphic characters and its location at fringe of plateau provides favorable condition for correlation of surface topography with basement topography and water table. It has been observed that basement surface is replica of ground surface only in regional or watershed perspective with reference to common datum. The basement surface is not always exact replica of ground surface at micro watershed scale. In many cases, basement surface is reverse of ground surface. The depth basement has remained constant along the basin water-divide situated near the margin of the plateau. The depth of basement (weathered horizon) is higher in upper reaches than lower reaches on the micro water-divides (upland) as well as in the drainage depressions (channels) within the sub-basin. The upper reaches of the sub-basin mainly along the basin water-divide has better groundwater prospects than lower reaches. There is no definite trend of water table with respect to ground and basement topography. Many places water table is shallow on the micro water-divides (upland) and deep in drainage depressions (channels). The established correlations are likely to be applicable in the other geographical area where similar watershed and geological characteristics exits.

To Classify the Groundwater Hydrographs by Factor Analysis Method

2012 ◽  
Vol 518-523 ◽  
pp. 4097-4103
Author(s):  
Hwa Sheng Gau ◽  
Chung Yi Chung ◽  
Shao Wei Liao ◽  
Wen Liang Lai
Keyword(s):  
Factor Analysis ◽  
Water Table ◽  
Unconfined Aquifer ◽  
Groundwater Table ◽  
Total Variance ◽  
Analysis Method ◽  
Pingtung Plain ◽  
Table Data ◽  
Three Components

This study is using Factor Analysis method to analyze the hydrographs of groundwater table for classification of recharge zone. The water table data are taken from 37 wells which located on unconfined aquifer in Pingtung plain. The result shows that 93% of total variance can be explained by three components. The 1th component is related to rainfall; the 2th and 3th are related to recharge from TungKang Basin and Kaoping basin, respectively.

Model Assisted Planning of Agricultural Groundwater Development in Bist Doab Interbasin (India)

2020 ◽  
Author(s):  
Aditya Kapoor ◽  
Deepak Kashyap
Keyword(s):  
Water Table ◽  
Unconfined Aquifer ◽  
Groundwater Development ◽  
Cropping Pattern ◽  
Maize Crop ◽  
Cropping Patterns ◽  
Sink Term ◽  
Point Data ◽  
Crop Area ◽  
The Impact

<p>Present study aims at planning of agricultural groundwater development in Bist interbasin (India) that is experiencing excessive water table decline due to intense agricultural groundwater pumping. The interbasin covering an area of 8040 Km<sup>2</sup> comprises an alluvial unconfined aquifer that is hydraulically connected to two major perennial rivers viz., Satluj and Beas.  A finite difference based distributed flow model of the study area was calibrated for transmissivity geostatistically on the basis of discrete point data at 15 points, and head fields available at 6 discrete times. The deficit of transmissivity data was overcome by invoking the Pilot point approach wherein transmissivity at additional artificial points are estimated by the least squares approach. The calibrated model was oriented towards the agricultural objective by correlating its sink term with crop areas. The model was used to simulate the long-term stabilized head and the depth fields corresponding to prevailing cropping pattern. The simulation indicates large and unsustainable water table decline. The impact of various moderated cropping patterns on the water table decline was subsequently simulated. It was concluded that replacement of some fraction of area under water intensive rice crop by maize crop area may stabilize the water table depths to acceptable limit.</p>

Floodplain hydraulics in a glaciated bedrock river valley

2012 ◽  
Vol 43 (6) ◽  
pp. 870-889 ◽  
Author(s):  
David W. Ostendorf ◽  
Erich S. Hinlein ◽  
Aaron I. Judge
Keyword(s):  
Travel Time ◽  
Water Table ◽  
Unconfined Aquifer ◽  
Silty Sand ◽  
Specific Yield ◽  
Recharge Rate ◽  
One Dimensional ◽  
Sand Deposit ◽  
Diurnal Fluctuations ◽  
Eastern Massachusetts

Data and one dimensional, unsteady theory document the average, seasonal, and diurnal hydraulics of an unconfined aquifer in the surficial floodplain deposit of the Neponset River, which flows through a glaciated bedrock valley in eastern Massachusetts. The 20 m thick silty sand deposit has a permeability of 1.4 × 10−11 m2, a porosity of 0.37, a 600 m halfwidth, and an infiltration coefficient of 0.39. The steady water table is parabolic with a 0.60 m value at the valley wall that implies an average 33-year travel time across the floodplain in response to an average recharge rate of 7.0 × 10−9 m/s. Seasonal hydraulics are governed by the floodplain porosity and marked by periodicity of the river (0.48 m amplitude) and recharge (1.9 × 10−8 m/s amplitude), which maintain flow from the floodplain into the river year round. Attenuation of the diurnal fluctuations suggests that the specific yield ranges from 0.05 to 0.14, and yields horizontal flow excursions of 1 m scale near the riverbank.

Water table drawdown due to a pumped well in an unconfined aquifer

1973 ◽  
Vol 9 (1) ◽  
pp. 236-242 ◽  
Author(s):  
T. D. Streltsova ◽  
K. R. Rushton
Keyword(s):  
Water Table ◽  
Unconfined Aquifer

scholarly journals Analytical Solutions of Vertical Airflow in an Unconfined Aquifer with Rising or Falling Water Table

Water ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 625
Author(s):  
Ran An ◽  
Pei Dong ◽  
Jun-Zhi Wang ◽  
Yifan Zhang ◽  
Xianfang Song ◽  
...  
Keyword(s):  
Water Flow ◽  
Water Table ◽  
Vadose Zone ◽  
Analytical Solutions ◽  
Air Flow ◽  
Thick Layer ◽  
Unconfined Aquifer ◽  
Positive Pressure ◽  
Low Permeability ◽  
Cap Layer

The rise and fall of the groundwater level can drive air flow in the vadose zone. In turn, the air flow can interact with the water flow. When the unconfined aquifer is covered by a low-permeability media, the coupling of the water flow and the air flow is more obvious. In this study, a conceptual model is established for coupling of air flow and water flow in the vadose zone in response to rapid fluctuations of the water table. Water injection and drainage experiments are conducted in a double-layered sand column with a thick layer (80.5 cm) of coarse sand and a thin layer of fine sand as a low-permeability cap. Different cap thickness (2 cm, 5 cm, 7.5 cm) and different thickness of the vadose zone (30 cm, 40 cm) are set for the experiments. Negative pressure (NP)/positive pressure (PP) of the air in the vadose zone is observed in the drainage/injection experiments, with higher pressure in experiments of thicker cap layer. In each experiment, NP or PP increases rapidly to reach a maximum in the early stage, and gradually becomes zero in the late stage. Analytical solutions on three subdivided stages indicate the permeability and thickness of the cap layer, as well as permeability and porosity of the media in the vadose zone are the key controlling factors on the process of coupling of air flow and water flow. The solutions also reveal the formation mechanism of air pressure in the vadose zone with a low-permeability cap. This study has both theoretical significance and engineering applications.

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