July, 2011 || Volume 15 No.3
1
Evaluation of aquifer parameters and groundwater quality in Doon Valley, Uttarkhand
Meenakshi Rawat, Hemanti Sharma, Manali Singh, U.Kedareswarudu and R. P. Singh1
University of Petroleum & Energy Studies, Energy Acres, Bidholi, Dehradoon, Uttarakhand
1 Central Ground Water Board, 419-A, Kanwali Road, Balliwala, Dehradoon, Uttarakhand.
E.mail: kedareswarudu@yahoo.com
ABSTRACT
Doon valley forms part of Dehradun District, Uttarakhand in the Himalayan Mountain Belt. Doon valley area is drained by the mighty rivers, Ganga, Yamuna and their tributaries prominent of which are Asan, Tons, Rispana and Song rivers. Though the area is bestowed with plenty of surface water resource, the major drinking and irrigation requirements of the valley are met through groundwater. Therefore, it becomes imperative to know the scientific attributes of the ground water bearing formations so that the ground water may be developed and managed in an objective and controlled manner. There are two aquifers in the valley, shallow aquifer under unconfined conditions and deeper with confined conditions. Pumping tests are carried out, one in each of the aquifers, to estimate the aquifer parameters and well characteristics. These values infer that these aquifers are with high potential. Groundwater quality is also analyzed through hydrochemical data obtained from 20 samples covering the area. Ninety five percent of the samples fall in field 5 of the Richard’s diagram where alkaline earths dominate over the alkalies and weak acids exceed the strong acids. The data suggests that the groundwater in Doon Valley is potable and suitable for domestic and irrigation purposes.
2
Importance of mapping of subsurface structures precisely in groundwater modeling
C.Krishnaiah
Central Water and Power Research Station, Khadakwasla, Pune - 411 024
E.mail : krishnaiahc@yahoo.com
Abstract
Groundwater, an important source of water supply in many regions of India, has been incessantly contaminated from various man made and natural pollution sources. Thus, concern over the potential for migration of wastes in the subsurface has generated a great deal of interest in the study of mechanisms responsible for contaminant transport through groundwater.
Numerical models have frequently been proved to be inadequate in spite of considerable efforts made to represent the actual flow mechanism in the subsurface on which contaminant transport depends. However, when modifications representing the flow mechanisms related to some undetected heterogeneous subsurface features were made, improvements were obtained in the agreement between field and modeled flow results. This is because if the subsurface heterogeneities such as fractures, dykes, buried channels or lenses are not known precisely, there is a chance of missing the presence of higher or lower hydraulic conductivity zones, leading to erroneous predictions.
In view of the above, finite element numerical modeling technique is used to study the effect of the presence of various subsurface structures, which control the flow mechanism and in turn alter the transport phenomenon. A base case of a homogeneous subsurface is considered and changes in the subsurface flow pattern aroused by heterogeneities were compared and examined. The study indicated that the spread of pollution depends on hydrogeology at the source. It is noticed that the existence of dykes, fractures and buried channels and their orientation modeled in the area greatly influenced the spread of pollution. The spread of contamination also depends on presence of lenses like clay or sand. From these results it can be concluded that if the subsurface is not precisely mapped, the groundwater models may be proved inadequate in the prognosis of contamination transport.
3
Audiomagnetotellurics (A.M.T) soundings based on the Bostick approach and evidence of tectonic features along the northern edge of the Congo Craton, in the Messamena/Abong-Mbang area (Cameroon)T.Ndougsa-Mbarga, A.Meying1, D.Bisso2, D.Y.Layu1, K.K.Sharma3 and E.Manguelle-Dicoum1
Department of Physics, Advanced Teacher’s Training College, University of Yaoundé I,
P.O. Box 47 Yaoundé Cameroun
1Department of Physics, Faculty of Science, University of Yaoundé I, P.O. Box 812 Yaoundé Cameroun.
2Department of Earth Sciences, Faculty of Science, University of Yaoundé I, P.O. Box 812 Yaoundé Cameroun.
3Department of Applied Geology, School of Earth and Atmospheric Sciences, University of Madras, Guindy Campus, Chennaï - 600 025, India.
E.mail: theopndougsa@gmail.com /tndougsa@yahoo.fr
ABSTRACT
An Audio-Magnetotelluric (A.M.T) study is carried out in the Messamena/Abong-Mbang area in Cameroon. It consists of two measurement profiles S-N. The A.M.T data sets are collected using a resistivity meter with frequencies ranging from 4.1 Hz to 2300 Hz. The frequency range used has permitted to reach some important depths because of high resistivity values of the metamorphic rocks. A 1D linearized inversion and 2D modelling of data led to attain a granitic basement at 9 km on one hand, and to put in evidence an important buried fault structure at Abong-Mbang in another hand. From a 2D modelling of pseudo-sections of resistivity and phase, a system of folds has been discovered at Messamena. The tectonic structures put in evidence in the Messamena/Abong-Mbang area are perfectly linked to the collision between the Pan-African Belt and the Congo Craton. The pseudo sections of phase for the two profiles permitted to propose two geological models of rock layers distribution.
4
Estimating the Viscosity of Rock Bodies - A Comparison Between the Hormuz- and the Namakdan Salt Diapirs in the Persian Gulf, and the Tso Morari Gneiss Dome in the Himalaya
Soumyajit Mukherjee
Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai- 400 076
E.mail: soumyajitm@gmail.com
ABSTRACT
Based on known extrusion rates, the viscosities of the Hormuz and the Namakdan salt diapirs in the Persian Gulf were estimated to be between 1.15×1017 and 8.75×1020 Pa s, and the Tso Morari gneiss dome in the Himalaya to be £ 1022 Pa s. The idea behind doing these exercises was that the deduced parameters would help us in building scaled analogue model of tectonics of these areas. Neglecting any gravity spreading, erosion and the geothermal gradient, these diapirs and domes were assumed to be incompressible Newtonian viscous fluids, which extruded at rates of few mm per year through channels of uniform elliptical or circular cross-sections driven by buoyant push arising from minor difference in density of the rocks at the bottom. However, while the salt diapirs rose £ 10 km through vertical channels for 104 yrs, the gneiss dome extruded hundreds or even thousands of km along a channel that plunged between 70 and 620 (maximum variation allowed by previous workers in their models) for 53 Ma covering hundreds or even thousands of km along the channel. Starting from the Poisson equation, the velocity profile of the salt diapirs are deduced to be time dependent and free from any overburden rocks, whereas that the velocity profile for the Tso Morari dome was independent to time and a plug of multi-lithology tried to prevent its extrusion were considered.
5
Delineation of shallow aquifer zones using electrical resistivity and bore hole litholog details in the Northwestern part of Bhuvanagiri, Chidambaram Taluk, Cuddalore District, Tamilnadu
C.Dushiyanthan, TJeyavel Raja Kumar, K.Karthikeyan1, B.Thiruneelakandan, D.Davidraju2 and K.ManoharanDepartment of Earth Sciences, Annamalai University, Annamalai Nagar – 608 002
1Department of Civil Engineering, Annamalai University, Annamalai Nagar – 608 002
2PSN college of Technology, Tharuvaikulam, Tirunelveli.
E-mail: hydrodushi@gmail.com
ABSTRACT
Five Vertical Electrical Soundings were carried out in the northwestern part of Bhuvanagiri, Chidambaram Taluk, Cuddalore District, Tamilnadu to identify the shallow fresh water zones and understand the sub-surface lithological sequence. The maximum electrode separation used is 100m by Schlumberger configuration. Geologically, sedimentary rocks of cretaceous and Mio-Pliocene with alluvium are present. The resistivity data was interpreted by using IPI2WIN software. The maximum error percentage observed was 4.3. The interpreted result shows four layer strata. The resistivity and layer thickness of the first layer are 2.82 ohm m to 10.9 ohm m and 0.9m to 4.77m respectively. The resistivity and layer thickness of the second layer varies from 1.66 ohm m to 17.7 ohm m and 3.61m to 12.0m respectively. The VES number 1 and 4 results indicate the shallow aquifer zones. The interpreted results have been compared with the subsurface strata to validate the results.
6
A comparative study of the groundwater potential in hard rock areas of Rajapuram and Balal, Kasaragod, Kerala
C.V.GopalanMarine and Coastal Surveys Division,Geological Survey of India
Mangaladevi Road, Pandeshwar, Mangalore – 575 001
E.mail : gopalancv@yahoo.com.
ABSTRACT
Groundwater exploration in hard rock terrain due to the restricted movement/occurrence of water, remains a challenging task. Resistivity of rock formation gives an indication of groundwater occurrence with an established inverse relationship. Resistivity surveys carried out in Rajapuram and Balal areas of Kasaragod district show contrasting results whereas the former is totally devoid of groundwater reserves while the latter has good potential. In Rajapuram, where the surface is covered with thick laterite, the resistivity values vary from 1795 ohm-m to 621 ohm-m from surface to depth of 100m.The interpretation of resistivity data using inverse slope method shows that there are three layers/formations below the surface. They are (1) Laterite cover at the top with a resistivity of 1000 ohm-m (0-30m) followed by (2) Less fractured rock with a resistivity of 400 ohm-m (30-60m) and (3) Massive rock with resistivity of 746 ohm-m (60-80m). Here, all the formations are dry and this site cannot be reccommended for bore well. In Balal area, where surface is covered with soil, the resistivity value ranges between 133 ohm-m to 253 ohm-m. The results of resistivity data shows three layers/formations. They are : (1) soil cover with resistivity of 118 ohm-m (0-15m) at top followed by (2) Less fractured rock with resistivity of 400 ohm-m (15-35m) and (3) Highly fractured rock with resistivity of 143 ohm-m which contains water at a depth of 35m to 50m. The site is reccommended for bore well with total depth of 50m and casing of 15m.Exploratory drilling confirms a discharge of 3 litres per second.
