- Email: [email protected]
An integrated study of electrical resistivity tomography and infiltration method in deciphering the characteristics and potentiality of unsaturated zone in crystalline rock
Journal Pre-proof An integrated study of electrical resistivity tomography and infiltration method in deciphering the characteristics and potentiality of unsaturated zone in crystalline rock
Taufique Warsi, V. Satish Kumar, Ratnakar Dhakate, C. Manikyamba, T. Vinoda Rao, R. Rangarajan PII:
S2589-7578(19)30023-X
DOI:
https://doi.org/10.1016/j.hydres.2019.11.009
Reference:
HYDRES 19
To appear in:
HydroResearch
Received date:
20 June 2019
Revised date:
11 November 2019
Accepted date:
27 November 2019
Please cite this article as: T. Warsi, V.S. Kumar, R. Dhakate, et al., An integrated study of electrical resistivity tomography and infiltration method in deciphering the characteristics and potentiality of unsaturated zone in crystalline rock, HydroResearch(2019), https://doi.org/10.1016/j.hydres.2019.11.009
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier.
Journal Pre-proof AN INTEGRATED STUDY OF ELECTRICAL RESISTIVITY TOMOGRAPHY AND INFILTRATION METHOD IN DECIPHERING THE CHARACTERISTICS AND POTENTIALITY OF UNSATURATED ZONE IN CRYSTALLINE ROCK Taufique Warsi1, V. Satish Kumar1*, Ratnakar Dhakate1, C. Manikyamba1, T. Vinoda Rao2, R. Rangarajan1 1-CSIR-National Geophysical Research Institute (Council of Scientific & Industrial Research) Uppal Road, Hyderabad – 500007, India Tel: +91-040-23434700; Fax: +91-040-27211564
of
*E-mail: [email protected]
ro
2- Department of Geology, Andhra University Andhra Pradesh, 530003
-p
ABSTRACT
re
To assess the shallow subsurface conditions in a granitic terrain, Electrical Resistivity Tomography (ERT) and double ring infiltrometer studies were conducted in Hyderabad city, India. Electrical Resistivity Tomography
lP
responses were monitored continuously with, Wenner and Schlumberger array with an electrode spacing of 1 and 5 meters. Double ring infiltrometer hydrogeological test was equally done on the same ERT profile to image the
na
subsurface resistivity distribution for shallow depths only. ERT has exemplified highly weathered and weathered zones and the infiltrometer study illustrated, the rate at which the water is infiltrating from the topsoil to the
ur
subsurface weathered zone. The data acquired from ERT and infiltration tests were analyzed and it is depicted that
Jo
the rate of infiltration is increasing gradually concerning time i.e. at the 100th minute there is an anomaly showing a rapid increase in the rate of infiltration and the same is revealed in its depth calculation graph. Results indicating that the infiltrated water is tending to flow laterally rather than vertical, up to a depth of 17 meters, thus concluding that this zone might be dominated by sheeting joints which play a vital role as a water carrier to enhance groundwater quality as well as quantity. These sheeting zones are generally flat, sometimes curved and nearly parallel to the topographic level which is formed mainly in granitoid rocks. A comprehensive study reveals the near surface information and its potentiality in terms of groundwater recharge. The findings and approach has implication towards selecting suitable sites and implementing best recharge techniques to improve the aquifer condition in all the sectors and can be upscale on a regional level in granitic terrain.
1
Journal Pre-proof Keywords: ERT, DOUBLE RING INFILTROMETER, SHEETING JOINTS, UNSATURATED ZONES, HYDERABAD, INDIA
INTRODUCTION In today’s generation, water resource study has an increasing need to resolve the complex hydrologic problems in all phases of the hydrologic cycle. For a better consideration of infiltration, balanced research was
of
carried out, as defined by the (Soil Science Society of America,1956) "the descending passage of water into the soil"
ro
and a knowledge of how the hydrologic property may be evaluated. There are various factors affecting infiltration, which are briefed in this report and also the method for defining infiltration data (Richards 1952) and by the (Soil
-p
Science Society of America,1956) defined infiltration rate (infiltration capacity) as the maximum rate of water
re
impounded on the surface is riveted by the soil at a shallow depth and when suitable provisions are taken regarding the border or fringe, effects. Infiltration rate has the dimensions of velocity, LT-1, where L= length and T =time and
lP
Infiltration velocity, has been defined (Soil Science Society of America,1956) as per unit of area with per unit of time, the volume of water descending into the soil surface and has the dimensions similar to velocity. The
na
infiltration velocity is directly proportional to the infiltration rate. Usually, the infiltration rate or velocity is
ur
represented in inches per hour or centimeters per hour. Early work by Muntz (1908) was followed by evaluation studies by many investigators, among which were Kohnke
Jo
(1938), Free et.al (1940), Nelson and Muckenhirn (1941) and Klute (1952). The flow of water through soils in saturated and unsaturated water have been made by Colman and Bodman (1944), Kirkham and Feng (1949), Marshall and Stirk (1949), Miller and Richard (1952), regarding watercourse from infiltrometers under conditions of low initial moisture, a little information is available. Marshall and Stirk (1949) measure water below this infiltrometers is observed by tensiometers Haise (1949) and studied flow arrays in coarse-textured soils. Aronovici (1955), the complete study of water-flow patterns below infiltrometers and exemplified the impact of surface and subsurface circumstances on observed infiltration rates. The water which fall on the surface goes through the vadose zone, it is known as the active area which controls the water flux between the surface and groundwater. So understanding of soil moisture movement through vadose zone plays a vital role in the hydrological process. Many
2
Journal Pre-proof scientific workers have worked to understand the soil moisture movement but still, it is not vibrant. (Blo¨schland and Sivapalan (1995), Mahmood (1996), Sposito (1998), and Western et al. (2002).
Geophysical methods viz., ground-penetrating radar and electrical resistivity do not affect the soil structure, and the resulting measurement overlays the first level of spatial variability, at a decametric or even hectometres scale. Electrical Resistivity Tomography (ERT) has been extensively used for hydrogeological investigation (Binley
of
and Kemna, 2005); recently, it was also used to image the subsurface features like the structure near the surface and even the water content for the representation of hydrological processes. The study of various electrical sounding
ro
curves guided about the water infiltration and eventually the aquifer recharge (Barraud et al., 1979; Cosentino et al.,
-p
1979). The current improvement of a surface multi-electrode method, known as electrical resistivity tomography (ERT), offers nearly stimulating perceptions. This method is predominantly well suited to the 2-D explanation of
re
geological structures upright to the measurement electrode line (Griffiths and Turnbull, 1985; Griffiths et al., 1990;
lP
Shima, 1990; Griffiths and Barker, 1993). However, the electrical resistivity is known to be profound use to other physical factors like temperature and soil solution (Friedman, 2005; Besson et al., 2008). Many studies have shown
na
that electrical resistivity tomography (ERT) can be an apt method to study complex electrical resistivity distributions (2D or 3D) on a large scale (10–100 m wide and up to 40 m deep) (Bernstone et al., 2000; Binley et al., 2002;
ur
Buselli and Lu, 2001; Day-Lewis et al., 2003; De Carlo et al., 2013; Depountis et al., 2005; Descloitres et al., 2008).
Jo
The main objective of this paper is to perform the ERT to understand the movement and pathways of infiltrated water through vadose zone study and infiltration test at a particular point continuously concerning time and monitor the variations in the infiltration rate and the resistivity variation in two dimensions for the unsaturated subsurface layers. STUDY AREA, GEOLOGY, AND HYDROLOGY The study area is located in Hyderabad city, Telangana, India. The area is mainly characterized by flat topography with a semi-arid controlled climate. Geologically the study area consists of a part of the pre-Cambrian shield and is underlain by the Archaean crystalline complex, comprising of Granitoid rocks (mainly pink and grey granite) which exhibit structural features such as fractures, joints, faults, and fissures. The dominant rock in the
3
Journal Pre-proof study is feldspar and biotite rich granite, having a light color called leucocratic granite. The biotite, which plays an important role in weathering, appears to be a weak link during the weathering process. The study area is estimated around 1km2 which is mainly covered with grassland and plantation occupied by small patches of built-up land. The thickness of the Vadose zone ranges from 0 to 30 m thick, 10 m of the column is shared by a fissured granitic layer. The soil thickness in the study area varies between less than a meter to three meters in different zones. Geophysical studies and field observations have disclosed the existence of a tectonic feature. Dykes are crossed around the study area which trends east-west direction situated at Nacharam, Tarnaka Engerrand, (2002); Arora, (2008). The pattern
of
of the groundwater flow in the study area remains the same, broadly the groundwater flow is predominantly from north to south in the northern part of the area and towards southwest and west in the southern part of the area.
ro
Rainfall is estimated at around 600 to 800mm per year as per the reading of rain gauge installed in the study area.
-p
ERT and infiltration measurements were conducted in the area which has a soil thickness varying only a few
re
centimeters to one meter. So this experiment was carried out to study the subsurface characteristics behavior, the study area falls in the low lying area where the water is collected from all over the upstream and gets accumulated at
lP
this location.
na
METHODOLOGY
DOUBLE RING INFITROMETER
ur
The single ring infiltrometer works on the same principle as is built for the double ring infiltrometer where
Jo
an extra ring is installed concentrically to the inner ring. The goal of this extra ring is to generate only upright flow in the inner ring by reducing the sideways ground flow. The methods of Wu et al. (1999) can also be used, as these methods are applicable for both single as well as double-ring infiltrometer. Reynolds et al. (2002), Youngs (1987) and Wu et al. (1997). It was not certain whether the effect of the outer ring ensures a perfect upright flow. Wu et al. (1997) mentioned that the measurement error due to lateral flow is inversely proportional to the size of the ring. Wuest (2005) established that a single ring with the same diameter of a double ring records a higher infiltration rate and water flows from outer to the inner ring. The inner ring diameter of 30 cm (12 inches) and 60-cm (24 inches) diameter for the outer ring are suggested for a double-ring infiltrometer. The rings were kept vertical, and while driving the ring unnecessary disturbance of the soil surface was avoided. The rings were driven to 1 to 2 cm into the soil layer where the infiltration rate for a low subsurface layer is preferred. The rings were installed and a heavy
4
Journal Pre-proof wooden block has been placed and moved on the edges of the rings and hammered on that block to ensure that the rings penetrate the soil uniformly. Extra care has been taken that soil is not disturbed and both the rings were mounted to the same depth in this double-ring infiltrometer. Insitu groundwater was used instead of fresh water in order to maintain the equilibrium condition in terms of water quality. Water was cautiously poured into the inner and outer ring to maintain the desired depth and ensure that the water head in both the rings are at same level. The height of the water in the inner ring was measured initially for every 1 second by holding a ruler at the inner side of the ring. After the measurement the rings were filled and the volume of water were measured and noticed, which
of
was mandatory to calculate the depth of water percolating in to the soil (Table-I). This procedure continued till 10
ro
minutes for an interval of 1 second and then for every 2 seconds measurement was carried and the procedure was repeated till 25 minutes and thereafter interval was changed to 5 minutes and test was carried out till 110 minutes
-p
with the same interval of 5 minutes and then an interval of 10 minutes was taken up till the end of test i.e. 2 hours.
re
The filling required a lot of water and the total water added was 82.3 liters. For a low permeability, a longer test is
lP
desirable or a long-range infiltration rate is more applicable to the problem being studied. CALCULATIONS
na
The volume of water used during each measured time interval should be converted into the depth of water per unit of time (inches per hour or centimeters per hour). These calculations were made using the table given
ur
below. For double-ring infiltrometers, these calculations usually are for both rings combined. The main specification
Jo
for using the double-ring infiltrometer is given in Table-I, for calculating the depth the value used were 4. 57X10-4 in centimeters.
Table –I: Specification for double-ring infiltrometers experiment The diameter of
Area of annular
Area of annular
The volume of water,
Multiply the volume of water used in ml by
rings (inches)
space (sq in)
space (sq cm)
in ml, providing 1 in.
(A) or (B) to obtain the depth of water
depth (A) Inches
(B) Centimeters
12 and 18
141.4
912.3
2,318
4. 31X10-4
10.96X10-4
12 and 24
339.3
2, 189.2
5,561
1. 80X10-4
4. 57X10-4
5
Journal Pre-proof 197.9
1, 276.9
3. 08X10-4
3,244
7. 83X10-4
All the measured data, as well as the infiltration rates calculated during the progress of the test, are shown in the Tables-1 and 2.
ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT)
of
The principle of the ERT method comprises of the application of constant direct current into the ground
ro
through two current electrodes and measuring the resulting voltage at two potential electrodes (Dahlin and Zhou, 2004; Candansayar, 2008). The ERT method is based on a multi-electrode and multi-cable system spread on the
-p
ground. The position of current and potential electrodes during the measurement is dependent on the chosen
re
geometry of electrode arrays. The most commonly used arrays are the dipole-dipole, Wenner and Wenner–
lP
Schlumberger arrays. Each electrode configuration has specific advantages and disadvantages concerning the penetration depth and the horizontal & vertical resolution. In this study, the Wenner–Schlumberger configuration
na
has been utilized because it provides quite deep penetration, reliable stability and ability to detect both horizontal and vertical subsurface features (Dahlin and Zhou, 2004; Candansayar, 2008).
ur
Electrical Resistivity Tomography (ERT) has become a more and more renowned method over the decade to plot the electrical resistivity of the subsurface with complex geology (Griffiths and Barker 1993; Loke and Barker
Jo
18 and 24
1996; Zarroca et al. 2011; McInnis et al. 2013). Wenner-Schlumberger array was used to attain a good vertical resolution and also it provides a reasonable horizontal resolution (Sasaki 1992). An IRIS Syscal Junior Pro Switch48 resistivity instrument was used, with 24 stainless steel electrodes spaced at 1 m and 5 m electrode separation in the study area to know the Vadose zone thickness and scanning near surface condition in crystalline terrain. In total, seventeen ERT profiles were carried out to comprehend the resistivity variation with depths. The main goal of achieving these datasets was to study the unsaturated zone, which is varying from a depth of 4 to 24 m evidenced in the ERT. We use the RES2DINV software (Loke and Barker 1995; Loke et al. 2003) for the inversion of the apparent resistivity dataset. A least-square inversion method is used for a smooth-constrained inversion algorithm. It divides the subsurface strata into rectangular on the basis of resistivity, which is adjusted to minimize iteratively
6
Journal Pre-proof the difference between the computed and the measured apparent resistivity values; the root means square (RMS) error gives a measure of this difference (Loke and Barker 1996; Sasaki 1992). Generally, the data obtained during ERT field measurements are classically presented as apparent resistivity pseudo-sections, which give an approximate picture of the subsurface resistivity. Later inversion was achieved, which is based on the regularized least-squares optimization method (deGroot-Heldin and Constable, 1990; Loke et al., 2003).
of
RESULTS AND DISCUSSION
ro
Two test sites were selected in the area, which was approximately 10 m away from one other. The site 1, which is close to bore well wherein an infiltrometer was set up to conduct the infiltration test and at the same place
-p
ERT survey was carried out in such a way that the 12th electrode out of 24 electrodes was exactly placed in the inner
re
ring of infiltrometer, so that we can get a deeper information at this infiltrometer and periodically ERT pseudo section was retrieved whereas the infiltration test was uninterrupted till the end. Both the test was started
lP
simultaneously and were continued for 2 hours. Water level in the study area was measured with the manual Water level indicator (WLI) and found to be ~21m. There are 6 bore wells in the study area out of which 4 are in working
na
condition and remaining 2 are abandoned.
ur
At SITE 1 Table (1), represents the entire observation data like time interval, depth of penetration and rate of infiltration, as the time passed on the rate of infiltration was slowly increasing and its depth of penetration was
Jo
also increasing simultaneously but with a slight fluctuating, it is observed that there was an upsurge in the infiltration rate as well as its depth of penetration at 40th,100th and 160th minutes as in fig. (2a & 2b), the same was reflected in the ERT inverted model section, which was monitored for 20 minutes each and shown in ERT’s inverted sections (fig. 3). ERT 1 inverted section was the starting profile (0th minute) wherein it’s seen that a layer of thickness about ~1.3 to 2.5 meters is a sheeting joint sandwiched between the top and weathered zone. ERT 2 inverted section (20th minute) was showing the zone of wetting where water started flowing fast, which in turn results in an increase of infiltration rate was observed but in the case of depth of penetration graph
7
Journal Pre-proof there was a huge fluctuation as water was not flowing deeper into the soil which was dry initially, so it needs to saturate the pores on top surface. ERT 3 inverted section which was recorded at (40th minute) it’s seen that the plume of water after saturating top surface which was infiltrated up to a depth of 1.2 meters has moved rapidly as it has entered sheeting joint (hallow gap) underneath and same changes in slope are observed as in fig. (2a & 2b). ERT 4, 5 inverted sections which were recorded at (60th and 80th minutes) showing the plume movement
of
laterally, increasing the infiltration rate and its depth of penetration.
plume has been seen and it was confirmed by the fig. (2a & 2b).
ro
ERT 6 inverted section which was recorded at (100th minute) at this moment the water and movement of the
-p
ERT 7, 8 inverted sections at (120th and 140th minutes) in this cycle of models section the water is getting
re
infiltrated but not penetrating deep as the previous cycle of water which is infiltrated and is not allowing making the
lP
depth of penetration to decrease and even decrease the gradient of infiltration rate fig. (2a & 2b). ERT 9 inverted section at (160th minute) clearly states that the water that is infiltrated slowly has now
penetration observed.
na
reached that joint creating the plume of water to flow at a higher rate and the vice-versa with the depth of
ur
In the case of infiltration data, we have observed a cyclic pattern like for every 40 minutes the infiltration
Jo
rate gradient is lowered and after that, for 20 minutes the response of the curve was increasing. The data from 0th to 40th minute states that infiltration is gradually increasing and after that, from the 40th minute to 60th minute there is a rapid rise in the infiltration rate as well as the depth of penetration. The same cycle is repeated i.e. from 60th to the 100th minute again there was a very low gradient rise in infiltration rate and for 20 more minutes i.e. 100th to 120th minute we can see a rapid rise of infiltration rate. The same cycle is repeated for 120th to 160th minute the gradient was low and after that, there is an increase in its infiltration rate. In the case of depth of penetration curve, the first and second cycles response of curve was directly proportional to the rate of infiltration but after that 120th to 140th minute cycle, however, the rate of infiltration was low there was no penetration and decline in curve was observed the reason behind could be propelling the former saturated water by the fresh inward water (piston-flow model).
8
Journal Pre-proof SITE 2 was at a distance of about 10 meters from the SITE 1. In this ERT profiles were laid such a way that the 14th electrode was in the inner ring of infiltrometer out of these 24 electrodes. Table (2), represents the entire observation data like time interval, depth of penetration and rate of infiltration, as the time passed on, the rate of infiltration was slowly increasing and its depth of penetration was also increasing and fluctuating but it is observed that there was an upsurge in the infiltration rate as well as its depth of penetration at 20th,40th,100th and 140th minutes as in fig (4a & 4b), the same was reflected in the ERT inverted sections, which was monitored for an interval of 20 minutes each and shown in ERT’s sections (fig. 5).
of
ERT 1 inverted section was the starting profile (0th minute) wherein it's seen that the entire area was
ro
watered so this may be the reason for low resistivity from the top surface.
-p
ERT 2 and 3 inverted sections at (20th and 40th minute) in these sections it's seen that the plume of water is following its path of flow by the gradient. In the fig (4a & 4b) also seen that till 20th minute there is a gradual
re
increase in the depth of penetration and rise in infiltration rate.
lP
ERT 4 and 5 inverted sections at (60th and 80th minute) it is observed that the water is getting accumulated from the top surface and the water is flowing towards the 1st electrode following the trend of the slope. Its again seen
na
that water is getting accumulated and its plume is trying to move very slowly. The response in fig (4a & 4b) shows
minute.
ur
the depth of penetration and rate of infiltration were also decreasing slowly from the time interval of 60 th to 80th
Jo
ERT 6 inverted section at (100th minute) in this section its clearly observed that how the water which was accumulated in the previous interval of time has suddenly moved due to this piston-flow model i.e. the freshwater entering has propelled the older accumulated water and making to the plume flow rapidly and this infiltrated water was flowing in vertically as well as in lateral direction. This was even correlated with the fig (4a & 4b) showing a sudden upsurge in both the rate of infiltration and its depth of penetration. With this study, we can say that water is even flowing in vertical as well as lateral pattern. ERT 7 inverted section at (120th minute) showing the similar pseudo section as it is in the 0th to the 20th minute, showing a slow rise in the rate of infiltration and decreasing trend for the depth of penetration. It indicates the same cyclic pattern again started.
9
Journal Pre-proof ERT 8 inverted section at (140th minute) this model resistivity section is very much similar to this 60th and 80th minute but here there is more lateral spread from the top surface and even the plume is seen flowing the gradient. In the case of infiltration data at site 2, we have observed a similar pattern but not in a cyclic pattern as in the case of site1 but the changes are quite similar if we consider their time i.e. at 20, 100 and 140 th minute, showing a delay pattern when compared with the site 1. The infiltration rate gradient is increasing from the initial time and at 20 minutes the response of the curve was upsurge and the same was observed in the depth of penetration. As the
of
time of infiltration passed on, there was an increasing trend in the rate of infiltration as well as the depth of
ro
penetration. There was a sudden increase in infiltration and depth of penetration at the 100th minute and after that at
-p
140th minute also this increase was observed. All their variations were very well correlated in the ERT results. As per the lateral variation of inverted section we can observe the low resistive zones which are broader at the top
re
and can be concluded as closely spaced vertical joints which is connecting to the sheeting joints. In order to maintain
lP
the equilibrium condition, generally, infiltration rate will be higher at the initial phase and decreases gradually with time to the saturated state. Though, this scenario is different which attributed that the presence of sheeting joint
na
accelerates the passage of water through the joint in a way of preferential flow rather than piston flow. Since piston flow is very much confined to the weathered zone (soil) so it will not be applicable in the case of sheeting joint. By
ur
the virtue of sheeting joint passage of water below the surface is getting easier which impart us an idea to understand
Jo
the subsurface condition. As we can see in the figures (2a, 2b and 4a, 4b) that the general trend of infiltration rate is going on increasing with the small drastic kink during the passage which clearly provide the information that the water rushing through the joint and these scenarios can be justified through the 2D ERT inverted section (Fig. 3 & 5).
CONCLUSION Sheeting joints are the fractures or openings which generally advance parallel to the natural topographical slope and originated by tensile forces and some time it is observed as an outcome of mechanical fracturing which extends laterally over tens to hundreds of meters. The study manifested that there is a sheeting joint with a varying
10
Journal Pre-proof depth of 1-2.5 meter at site 1 and 6-16 meter at site 2. This sheeting joints has played a vital role in this experimental study of continuous monitoring of variation of near-surface resistivity at shallow depths through ERT and the inflow of water within the unsaturated layers by infiltration study at the two different sites in the study area. The evidence of sheeting joint is observed from the ERT results and it has been verified with the infiltration test and their results. It is seen that the infiltrated water is not penetrating deeper and the movement of water is lateral rather than vertical this phenomenon is due to the presence of sheeting joint, which restricts the flow of water to penetrate deeper within the unsaturated layers but might be connected to the aquifer somewhere which is a major finding from this study.
of
This finding can be very vigorous in terms of groundwater recharge through appropriate recharge technique in this near surface stressed condition. Integration of both resistivity and infiltration study impart us the idea about the
ro
existence of sheeting joint below the surface. This robust integrated approach can be upscale to the other regions of
-p
granitic terrain in order to implement recharge techniques, hence this approach can be very effective in terms of
re
groundwater recharge and management.
lP
ACKNOWLEDGMENT
The authors express their sincere gratitude to the Director, CSIR-NGRI, Hyderabad for his continuous
na
support and encouragement for the research activity. The first author acknowledges the cooperation of scientists and colleagues Dr. Dewashish Kumar, Mr. Arun Kumar, Mr. Vinod Kumar, and Mr. Venkatesh and Raj Kumar for their
ur
support and helping constantly in the fieldwork for collecting different types of the data and correcting the
Jo
manuscript. Author would also like to thank the reviewers and Editor for their valuable comments and suggestions to improve the quality of the manuscript. REFERENCES
Aronovici, V.S., 1955. Model study of ring infiltrometer performance under low initial soil moisture: Soil Sci. Soc. America Proc., v. 19, p. 1-6. Arora Tanvi., 2008. Geophysics and Geostatistics: An integrated approach to characterize and monitor the unsaturated zone, Thesis. Barraud, J.P., Dieulin, A., Ledoux, E., de Marsily, G., 1979. Relation entre mesures ge´ophysiques etflux de l'eau dans les sols non sature´s, Rapp. LHM/RD/79/3, Ecole Natl. Supe´ rieure des Mines de Paris, Paris.
11
Journal Pre-proof Bernstone, C., Dahlin, T., Ohlsson, T., Hogland, W., 2000. DC-resistivity mapping of internal landfill structures: two pre-excavation surveys. Environ. Geol. 39 (3–4), 360–371 Besson, A., Cousin, I., Dorigny, A., Dabas, M., King, D., 2008. The temperature correction for the electrical resistivity measurements in undisturbed soil samples: analysis of the existing conversion models and proposal of a new model. Soil Sci. 173 (10), 707–720 Binley, A., Winship, P., West, L.J., Pokar, M., Middleton, R., 2002. Seasonal variation of moisture content
of
in unsaturated sandstone inferred from borehole radar and resistivity profiles. J. Hydrol. 267 (3–4), 160–172.
ro
Binley, A., Kemna, A., 2005. DC resistivity and induced polarization methods. In: Yuram, R., Hubbard, S.S. (Eds.), Hydrogeophysics. Water and Science Technology Library, vol. 50. Springer, New York, pp. 129–156.
-p
Blo¨schl, G., and Sivapalan, M., 1995. Scale issues in hydrological model-ing—A review, Hydrol.
re
Processes, 9, 251 – 290, doi:10.1002/hyp.3360090305
lP
Buselli, G., Lu, K.L., 2001. Groundwater contamination monitoring with multichannel electrical and electromagnetic methods. J. Appl. Geophys. 48 (1), 11–23
na
Candansayar, M.E., 2008. Two-dimensional individual and joint inversion of three and four-electrode array
ur
dc resistivity data. Journal of Geophysics and Engineering 5, 290-300. Colman, E.A., Bodman, G.B., 1944. Moisture and energy conditions during downward entry of water into
Jo
moist and layered soils: Soil Sci. Soc. America Proc., 1943, v. 9, p. 3-11. Cosentino, P., Cimino, A., Riggio, A.M., 1979. Time variations of the resistivity in a layered structure with the unconfined aquifer. Geoexploration, pp. 11–17. Dahlin, T., Zhou, B., 2004. A numerical comparison of 2-D resistivity imaging with 10 electrode arrays. Geophysical Prospecting 52, 379-398. Day-Lewis, F.D., Lane, J.W., Harris, J.M., Gorelick, S.M., 2003. Time-lapse imaging of saline-tracer transport in fractured rock using difference-attenuation radar tomography.Water Resour. Res. 39 (10), 1740–1752.
12
Journal Pre-proof De Carlo, L., Perri, M.T., Caputo, M.C., Deiana, R., Vurro, M., Cassiani, G., 2013. Characterization of a dismissed landfill via electrical resistivity tomography and mise-à-la-masse method. J. Appl. Geophys. 98, 1–10. DeGroot-Hedlin, C., Constable, S.C., 1990. Occam's inversion to generate smooth, two-dimensional models from magnetotelluric data. Geophysics 55, 1613-1624. Depountis, N., Harris, C., Davies, M.C.R., Koukis, G., Sabatakakis, N., 2005. Application of electrical imaging to leachate plume evolution studies under in-situ and model conditions. Environ. Geol. 47 (7), 907–914.
of
Descloitres, M., Ruiz, L., Sekhar, M., Legchenko, A., Braun, J.J., Kumar, M.S.M., Subramanian, S., 2008.
ro
Characterization of seasonal local recharge using electrical resistivity tomography and magnetic resonance sounding. Hydrol. Process.22 (3), 384–394.
-p
Engerrand, C., 2002. Hydrogéologie des socles cristallins fissures a fort recouvrement d’altérites en regime
re
de mousson: étude hydrogéologique de duex bassins versants situés en Andhra Pradesh (Inde). Thése de doctorat,
lP
Université Paris VI
Free, G.R., Browning, G.M., Musgrave, G.W., 1940. Relative infiltration and related physical
na
characteristics of certain soils: U.S. Dept. Agriculture Tech. Bull. 729, 52 p. Friedman, S.P., 2005. Soil properties influencing apparent electrical conductivity: a review. Comput.
ur
Electron. Agr. 46 (1–3), 45–70.
Jo
Griffiths, D.H., Turnbull, J., 1985. A multi-electrode array for resistivity surveying. First Break 3, 16–20. Griffiths, D.H., Turnbull, J., Olayinka, A.I., 1990. Two-dimensional resistivity mapping with a computercontrolled array. First Break 8, 121–129. Griffiths, D.H., Barker, R.D., 1993. Two-dimensional resistivity imaging and modelling in areas of complex geology. J. Applied Geophysics 29, 211–226. Haise, H.R., 1949. Flow pattern studies in irrigated coarse-textured soils: Soil Sci. Soc. America Proc. 1948, v. 13, p. 83-89.
13
Journal Pre-proof Kirkham Don., Feng, C.L., 1949. Some tests of the diffusion theory and laws of capillary flow, in soils: Soil Sci., v. 67, p. 29-40. Klute, A., 1952. Some theoretical aspects of the flow of water in unsaturated soils: Soil Sci. Soc. America Proc., v. 16, p. 144-148. Kohnke Helmut., 1938. A method for studying infiltration: Soil Sci. Soc. America Proc., v. 3, p. 296-303. Loke, M.H., Barker, R.D., 1995. Least-square deconvolution of apparent resistivity pseudo-sections.
of
Geophysics 60(6):499–523.
ro
Loke, M.H., Barker, R.D., 1996. Rapid least-squares inversion of apparent resistivity pseudosections by a
-p
quasi-Newton method. Geophys Prospect 44:131–152
imaging inversion. J. Appl. Geophys. 49, 149–162.
re
Loke, M.H., Dahlin, T., 2002. A comparison of the Gauss-Newton and quasi-Newton methods in resistivity
lP
Loke, M.H., Acworth, I., Dahlin, T., 2003. A comparison of smooth and blocky inversion method in 2D
na
electrical tomography surveys. Explor Geophys 34:182–187. Mahmood, R., 1996. Scale issues in soil moisture modelling: Problems and prospects, Prog. Phys. Geogr.,
ur
20, 273 – 291, doi:10.1177/030913339602000302.
68, p. 359-370.
Jo
Marshall, T. J., Stirk, G.B., 1949. Pressure potential of water moving downward into the soil: Soil Sci., v.
McInnis, D., Silliman, S., Boukari, M., Yalo, N., Orou-Pete, S., Fertenbaugh, C., Sarre, K., Fayomi, H., 2013. Combined application of electrical resistivity and shallow groundwater sampling to assess salinity in a shallow coastal aquifer in Benin, West Africa. J Hydrol 505(15):335–345. Miller, R.D., Richard, Felix., 1952. Hydraulic gradients during infiltration in soils: Soil Sci. Soc. America Proc., v. 16, p. 33-38. Muntz, M.A., 1908. Influence of the permeability of soils on the conditions and success of irrigation: Direction Hydraulique Agricoles Annales, v. 38, p. 17.
14
Journal Pre-proof Nelson, L.B., Muckenhirn, R.J., 1941. Field percolation rates of four Wisconsin soils having different drainage characteristics: Agronomy Jour., v. 33, p. 1028-1036. Reynolds, W., Elrick, D., Youngs, E., Amoozegar, A., Booltink, H., Bouma, J., Clothier, B., Scotter, D., 2002. Methods of Soil Analysis. Part 4. SSSA Book Series. Soil Science Society of America. Richards, L.A., 1952. Report of the Subcommittee on Permeability and Infiltration, Committee on Terminology, Soil Science Society of America: Soil Sci. Soc. America Proc., v. 16, p. 85-88.
of
Sasaki, Y., 1992. Resolution of resistivity tomography inferred from nuERTcal simulation. Geophys
ro
Prospect 40:453–464.
Shima, H., 1990. Two-dimensional automatic resistivity inversion technique using alpha centers.
-p
Geophysics 55, 682–694.
lP
Soil Sci. Soc. America Proc., v. 20, p. 430-440.
re
Soil Science Society of America, 1956, Report of definitions approved by the Committee on Terminology:
Sposito, G., 1998. Scale Dependence and Scale Invariance in Hydrology,423 pp., Cambridge Univ. Press,
na
Cambridge, U. K.
ur
Western, A. W., R. B. Grayson, and G. Blo¨schl., 2002. Scaling of soil moisture: A hydrologic perspective,
Jo
Annu. Rev. Earth Planet. Sci., 30,149 – 180, doi: 10.1146/annurev.earth.30.091201.140434. Wu, L., Pan, M.L., Roberson, Shouse. P., 1997. Numerical evaluation of ring-infiltrometers under various soil conditions. Soil Science, 162:771–777. Wu, L., Pan, L., Mitchel, J., Sanden, B., 1999. Measuring saturated hydraulic conductivity using a generalized solution for single ring infiltrometers. Soil Science Society of America Journal, 63:788–792. Wuest, S., 2005. Bias in ponded infiltration estimates due to sample volume and shape. Vadose Zone Journal, 4:1183–1190. Youngs, E., 1987. Estimating hydraulic conductivity values from ring infiltromete measurements. Journal of Soil Science, 38:623–632.
15
Journal Pre-proof Zarroca, M., Bach, J., Linares, R., Pellicer, X.M., 2011. Electrical methods (VES and ERT) for identifying, mapping and monitoring different saline domains in a coastal plain region (Alt Emporda`, Northern Spain). J Hydrol
Jo
ur
na
lP
re
-p
ro
of
409(1–2):407–422.
16
Journal Pre-proof
FIGURE CAPTIONS Fig. 1: Location map of selected sites at NGRI campus Fig. 2a: Infiltration rates at site 1 Fig. 2b: Depth of penetration at site 1 Fig. 3: ERT inverted section at site 1 exhibiting flow of water through weaker zones. Fig. 4a: Infiltration rates at site 2 Fig 4b: Depth of penetration at site 2
Jo
ur
na
lP
re
-p
ro
of
Fig. 5: ERT inverted section at site 2 showing the passage of water in vadose zone.
17
Journal Pre-proof
Authors contribution Author 1: Taufique warsi
Involved in the blueprint of this work Actively involved in acquiring the data set Helped co-authors Comprehensive writing of paper with the authors support Analysis was done along with Co-authors Involved in the revision of the manuscript
ro
re
-p
Involved in the blueprint of this work Actively involved in acquiring the data set Helped co-authors Comprehensive writing of paper with the authors support Analysis was done along with Co-authors
lP
of
Author 2: V. Satish kumar
na
Author 3: Ratnakar Dhakate
Jo
ur
Involved in designing the experiment Partially involved in the experiment Suggestion was made in order to write the paper
Author 4: C. Manikyamba
Involved in designing the experiment Partially involved in the experiment Suggestion was made in order to write the paper
Author 5: T. Vinoda Rao
Involved in designing the experiment Partially involved in the experiment Suggestion was made in order to write the paper 18
Journal Pre-proof Author 6: R. Rangarajan
Jo
ur
na
lP
re
-p
ro
of
Involved in designing the experiment Partially involved in the experiment Suggestion was made in order to write the paper
19
Journal Pre-proof TABLE 1. INFILTRATION DATA AND CALCULATION OF SITE 1
of
INFILTRATION RATE (mm/minute) 0.00000 0.00009 0.00030 0.00044 0.00059 0.00074 0.00089 0.00101 0.00105 0.00126 0.00127 0.00153 0.00162 0.00171 0.00178 0.00190 0.00217 0.00265 0.00289 0.00337 0.00340 0.00380 0.00399 0.00477 0.00471 0.00529 0.00517 0.00547 0.00577 0.00726 0.00740 0.00810 0.00860 0.00933 0.00961 0.01162 0.01036 0.01058 0.01297 0.01341 0.01316 0.01451 0.01450 0.01555
-p
ro
LEVEL (cm) 15 12.8 14 14 14 14 14 14.1 14.4 14.2 14.5 14.2 14.3 14.4 14.5 14.5 14.3 13.8 13.9 13.7 14 13.9 14 13.6 13.9 13.7 14 14 14 13.4 13.6 13.5 13.5 13.4 13.5 12.9 13.6 13.7 13.1 13.2 13.5 13.3 13.5 13.4
na
lP
re
ACTUAL LEVEL (cm) 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15
ur
WATER ADD (ml) 2000 1554.3 706.5 706.5 706.5 706.5 706.5 635.85 423.9 565.2 353.25 565.2 494.55 423.9 353.25 353.25 494.55 847.8 777.15 918.45 706.5 777.15 706.5 989.1 777.15 918.45 706.5 706.5 706.5 1130.4 989.1 1059.75 1059.75 1130.4 1059.75 1483.65 989.1 918.45 1342.35 1271.7 1059.75 1201.05 1059.75 1130.4
Jo
TIME (minutes) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 19 21 23 25 27 29 31 33 35 37 39 42 45 48 51 54 57 60 63 66 70 74 78 82 86 90
20
DEPTH (cm) 0 0.706 1.138 1.138 1.138 1.138 1.138 1.106 1.010 1.074 0.978 1.074 1.042 1.010 0.978 0.978 1.042 1.202 1.170 1.234 1.138 1.170 1.138 1.266 1.170 1.234 1.138 1.138 1.138 1.330 1.266 1.298 1.298 1.330 1.298 1.491 1.266 1.234 1.427 1.395 1.298 1.362 1.298 1.330
Journal Pre-proof 13.4 13.3 13 12.5 12.6 12.8 12.9 12.9 13 13.1 13 11.4 11.5 11.6
-p re lP na ur 21
0.01625 0.01752 0.01990 0.02335 0.02412 0.02433 0.02498 0.02614 0.02672 0.02724 0.02899 0.04175 0.04359 0.04535
of
15 15 15 15 15 15 15 15 15 15 15 15 15 15
ro
1130.4 1201.05 1413 1766.25 1695.6 1554.3 1483.65 1483.65 1413 1342.35 1413 2543.4 2472.75 2402.1
Jo
94 99 105 111 117 123 129 135 141 147 153 163 173 183
1.330 1.362 1.459 1.619 1.587 1.523 1.491 1.491 1.459 1.427 1.459 1.972 1.940 1.908
na
ro
INFILTRATION RATE (mm/minute) 0.00000 0.00004 0.00013 0.00018 0.00018 0.00022 0.00022 0.00033 0.00038 0.00040 0.00088 0.00071 0.00138 0.00079 0.00170 0.00118 0.00130 0.00410 0.00462 0.00401 0.00483 0.00623 0.00578 0.00637 0.00696 0.00755 0.00814
re
-p
LEVEL (cm ) 15 12.8 12.7 13.8 14 14 14 14 13.8 14 14 13 13.4 13 13.7 13 13.4 13.2 11.1 11.5 12.1 11.8 11.9 12.2 12.1 12 12.2
lP
ACTUAL LEVEL (cm) 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15
ur
WATER ADD (ml) 5000 600 1100 1000 750 750 630 810 810 750 1490 1000 1670 840 1600 1000 1000 2900 2700 2000 2100 2400 2000 2000 2000 2000 2000
Jo
TIME (minutes) 0 1 2 3 4 5 6 7 8 9 10 12 14 16 18 20 22 24 29 34 39 44 49 54 59 64 69
of
Journal Pre-proof
22
DEPTH (cm) 0 2.5424 2.7694 2.724 2.6105 2.6105 2.55602 2.63774 2.63774 2.6105 2.94646 2.724 3.02818 2.65136 2.9964 2.724 2.724 3.5866 3.4958 3.178 3.2234 3.3596 3.178 3.178 3.178 3.178 3.178
Journal Pre-proof 12.1 12.5 12.4 12.3 12.9 12.8 12.9 12.7 10.4 10.7 10.8 10.7 10.9 11.2
0.00829 0.00792 0.00991 0.00997 0.01053 0.00934 0.00981 0.01993 0.02105 0.02130 0.02230 0.02636 0.02485 0.02542
of
15 15 15 15 15 15 15 15 15 15 15 15 15 15
ro
1900 1700 2000 1900 1900 1600 1600 3100 3000 2800 2720 3000 2650 2550
ur
na
lP
re
-p
TABLE 2. INFILTRATION DATA AND CALCULATION OF SITE 2
Jo
74 79 84 89 94 99 104 109 119 129 139 149 159 169
23
3.1326 3.0418 3.178 3.1326 3.1326 2.9964 2.9964 3.6774 3.632 3.5412 3.50488 3.632 3.4731 3.4277
Journal Pre-proof
HIGHLIGHTS This paper is an integrated study of ERT and infiltration method to decipher the sub-surface strata. The major finding from this study was identifying the sheeting joint.
Jo
ur
na
lP
re
-p
ro
of
This joint could be the sources for recharge and groundwater management
24
Figure 1
Figure 2
Figure 3r1
Figure 3r2
Figure 4
Figure 5r1
Figure 5r2
Taufique Warsi, V. Satish Kumar, Ratnakar Dhakate, C. Manikyamba, T. Vinoda Rao, R. Rangarajan PII:
S2589-7578(19)30023-X
DOI:
https://doi.org/10.1016/j.hydres.2019.11.009
Reference:
HYDRES 19
To appear in:
HydroResearch
Received date:
20 June 2019
Revised date:
11 November 2019
Accepted date:
27 November 2019
Please cite this article as: T. Warsi, V.S. Kumar, R. Dhakate, et al., An integrated study of electrical resistivity tomography and infiltration method in deciphering the characteristics and potentiality of unsaturated zone in crystalline rock, HydroResearch(2019), https://doi.org/10.1016/j.hydres.2019.11.009
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier.
Journal Pre-proof AN INTEGRATED STUDY OF ELECTRICAL RESISTIVITY TOMOGRAPHY AND INFILTRATION METHOD IN DECIPHERING THE CHARACTERISTICS AND POTENTIALITY OF UNSATURATED ZONE IN CRYSTALLINE ROCK Taufique Warsi1, V. Satish Kumar1*, Ratnakar Dhakate1, C. Manikyamba1, T. Vinoda Rao2, R. Rangarajan1 1-CSIR-National Geophysical Research Institute (Council of Scientific & Industrial Research) Uppal Road, Hyderabad – 500007, India Tel: +91-040-23434700; Fax: +91-040-27211564
of
*E-mail: [email protected]
ro
2- Department of Geology, Andhra University Andhra Pradesh, 530003
-p
ABSTRACT
re
To assess the shallow subsurface conditions in a granitic terrain, Electrical Resistivity Tomography (ERT) and double ring infiltrometer studies were conducted in Hyderabad city, India. Electrical Resistivity Tomography
lP
responses were monitored continuously with, Wenner and Schlumberger array with an electrode spacing of 1 and 5 meters. Double ring infiltrometer hydrogeological test was equally done on the same ERT profile to image the
na
subsurface resistivity distribution for shallow depths only. ERT has exemplified highly weathered and weathered zones and the infiltrometer study illustrated, the rate at which the water is infiltrating from the topsoil to the
ur
subsurface weathered zone. The data acquired from ERT and infiltration tests were analyzed and it is depicted that
Jo
the rate of infiltration is increasing gradually concerning time i.e. at the 100th minute there is an anomaly showing a rapid increase in the rate of infiltration and the same is revealed in its depth calculation graph. Results indicating that the infiltrated water is tending to flow laterally rather than vertical, up to a depth of 17 meters, thus concluding that this zone might be dominated by sheeting joints which play a vital role as a water carrier to enhance groundwater quality as well as quantity. These sheeting zones are generally flat, sometimes curved and nearly parallel to the topographic level which is formed mainly in granitoid rocks. A comprehensive study reveals the near surface information and its potentiality in terms of groundwater recharge. The findings and approach has implication towards selecting suitable sites and implementing best recharge techniques to improve the aquifer condition in all the sectors and can be upscale on a regional level in granitic terrain.
1
Journal Pre-proof Keywords: ERT, DOUBLE RING INFILTROMETER, SHEETING JOINTS, UNSATURATED ZONES, HYDERABAD, INDIA
INTRODUCTION In today’s generation, water resource study has an increasing need to resolve the complex hydrologic problems in all phases of the hydrologic cycle. For a better consideration of infiltration, balanced research was
of
carried out, as defined by the (Soil Science Society of America,1956) "the descending passage of water into the soil"
ro
and a knowledge of how the hydrologic property may be evaluated. There are various factors affecting infiltration, which are briefed in this report and also the method for defining infiltration data (Richards 1952) and by the (Soil
-p
Science Society of America,1956) defined infiltration rate (infiltration capacity) as the maximum rate of water
re
impounded on the surface is riveted by the soil at a shallow depth and when suitable provisions are taken regarding the border or fringe, effects. Infiltration rate has the dimensions of velocity, LT-1, where L= length and T =time and
lP
Infiltration velocity, has been defined (Soil Science Society of America,1956) as per unit of area with per unit of time, the volume of water descending into the soil surface and has the dimensions similar to velocity. The
na
infiltration velocity is directly proportional to the infiltration rate. Usually, the infiltration rate or velocity is
ur
represented in inches per hour or centimeters per hour. Early work by Muntz (1908) was followed by evaluation studies by many investigators, among which were Kohnke
Jo
(1938), Free et.al (1940), Nelson and Muckenhirn (1941) and Klute (1952). The flow of water through soils in saturated and unsaturated water have been made by Colman and Bodman (1944), Kirkham and Feng (1949), Marshall and Stirk (1949), Miller and Richard (1952), regarding watercourse from infiltrometers under conditions of low initial moisture, a little information is available. Marshall and Stirk (1949) measure water below this infiltrometers is observed by tensiometers Haise (1949) and studied flow arrays in coarse-textured soils. Aronovici (1955), the complete study of water-flow patterns below infiltrometers and exemplified the impact of surface and subsurface circumstances on observed infiltration rates. The water which fall on the surface goes through the vadose zone, it is known as the active area which controls the water flux between the surface and groundwater. So understanding of soil moisture movement through vadose zone plays a vital role in the hydrological process. Many
2
Journal Pre-proof scientific workers have worked to understand the soil moisture movement but still, it is not vibrant. (Blo¨schland and Sivapalan (1995), Mahmood (1996), Sposito (1998), and Western et al. (2002).
Geophysical methods viz., ground-penetrating radar and electrical resistivity do not affect the soil structure, and the resulting measurement overlays the first level of spatial variability, at a decametric or even hectometres scale. Electrical Resistivity Tomography (ERT) has been extensively used for hydrogeological investigation (Binley
of
and Kemna, 2005); recently, it was also used to image the subsurface features like the structure near the surface and even the water content for the representation of hydrological processes. The study of various electrical sounding
ro
curves guided about the water infiltration and eventually the aquifer recharge (Barraud et al., 1979; Cosentino et al.,
-p
1979). The current improvement of a surface multi-electrode method, known as electrical resistivity tomography (ERT), offers nearly stimulating perceptions. This method is predominantly well suited to the 2-D explanation of
re
geological structures upright to the measurement electrode line (Griffiths and Turnbull, 1985; Griffiths et al., 1990;
lP
Shima, 1990; Griffiths and Barker, 1993). However, the electrical resistivity is known to be profound use to other physical factors like temperature and soil solution (Friedman, 2005; Besson et al., 2008). Many studies have shown
na
that electrical resistivity tomography (ERT) can be an apt method to study complex electrical resistivity distributions (2D or 3D) on a large scale (10–100 m wide and up to 40 m deep) (Bernstone et al., 2000; Binley et al., 2002;
ur
Buselli and Lu, 2001; Day-Lewis et al., 2003; De Carlo et al., 2013; Depountis et al., 2005; Descloitres et al., 2008).
Jo
The main objective of this paper is to perform the ERT to understand the movement and pathways of infiltrated water through vadose zone study and infiltration test at a particular point continuously concerning time and monitor the variations in the infiltration rate and the resistivity variation in two dimensions for the unsaturated subsurface layers. STUDY AREA, GEOLOGY, AND HYDROLOGY The study area is located in Hyderabad city, Telangana, India. The area is mainly characterized by flat topography with a semi-arid controlled climate. Geologically the study area consists of a part of the pre-Cambrian shield and is underlain by the Archaean crystalline complex, comprising of Granitoid rocks (mainly pink and grey granite) which exhibit structural features such as fractures, joints, faults, and fissures. The dominant rock in the
3
Journal Pre-proof study is feldspar and biotite rich granite, having a light color called leucocratic granite. The biotite, which plays an important role in weathering, appears to be a weak link during the weathering process. The study area is estimated around 1km2 which is mainly covered with grassland and plantation occupied by small patches of built-up land. The thickness of the Vadose zone ranges from 0 to 30 m thick, 10 m of the column is shared by a fissured granitic layer. The soil thickness in the study area varies between less than a meter to three meters in different zones. Geophysical studies and field observations have disclosed the existence of a tectonic feature. Dykes are crossed around the study area which trends east-west direction situated at Nacharam, Tarnaka Engerrand, (2002); Arora, (2008). The pattern
of
of the groundwater flow in the study area remains the same, broadly the groundwater flow is predominantly from north to south in the northern part of the area and towards southwest and west in the southern part of the area.
ro
Rainfall is estimated at around 600 to 800mm per year as per the reading of rain gauge installed in the study area.
-p
ERT and infiltration measurements were conducted in the area which has a soil thickness varying only a few
re
centimeters to one meter. So this experiment was carried out to study the subsurface characteristics behavior, the study area falls in the low lying area where the water is collected from all over the upstream and gets accumulated at
lP
this location.
na
METHODOLOGY
DOUBLE RING INFITROMETER
ur
The single ring infiltrometer works on the same principle as is built for the double ring infiltrometer where
Jo
an extra ring is installed concentrically to the inner ring. The goal of this extra ring is to generate only upright flow in the inner ring by reducing the sideways ground flow. The methods of Wu et al. (1999) can also be used, as these methods are applicable for both single as well as double-ring infiltrometer. Reynolds et al. (2002), Youngs (1987) and Wu et al. (1997). It was not certain whether the effect of the outer ring ensures a perfect upright flow. Wu et al. (1997) mentioned that the measurement error due to lateral flow is inversely proportional to the size of the ring. Wuest (2005) established that a single ring with the same diameter of a double ring records a higher infiltration rate and water flows from outer to the inner ring. The inner ring diameter of 30 cm (12 inches) and 60-cm (24 inches) diameter for the outer ring are suggested for a double-ring infiltrometer. The rings were kept vertical, and while driving the ring unnecessary disturbance of the soil surface was avoided. The rings were driven to 1 to 2 cm into the soil layer where the infiltration rate for a low subsurface layer is preferred. The rings were installed and a heavy
4
Journal Pre-proof wooden block has been placed and moved on the edges of the rings and hammered on that block to ensure that the rings penetrate the soil uniformly. Extra care has been taken that soil is not disturbed and both the rings were mounted to the same depth in this double-ring infiltrometer. Insitu groundwater was used instead of fresh water in order to maintain the equilibrium condition in terms of water quality. Water was cautiously poured into the inner and outer ring to maintain the desired depth and ensure that the water head in both the rings are at same level. The height of the water in the inner ring was measured initially for every 1 second by holding a ruler at the inner side of the ring. After the measurement the rings were filled and the volume of water were measured and noticed, which
of
was mandatory to calculate the depth of water percolating in to the soil (Table-I). This procedure continued till 10
ro
minutes for an interval of 1 second and then for every 2 seconds measurement was carried and the procedure was repeated till 25 minutes and thereafter interval was changed to 5 minutes and test was carried out till 110 minutes
-p
with the same interval of 5 minutes and then an interval of 10 minutes was taken up till the end of test i.e. 2 hours.
re
The filling required a lot of water and the total water added was 82.3 liters. For a low permeability, a longer test is
lP
desirable or a long-range infiltration rate is more applicable to the problem being studied. CALCULATIONS
na
The volume of water used during each measured time interval should be converted into the depth of water per unit of time (inches per hour or centimeters per hour). These calculations were made using the table given
ur
below. For double-ring infiltrometers, these calculations usually are for both rings combined. The main specification
Jo
for using the double-ring infiltrometer is given in Table-I, for calculating the depth the value used were 4. 57X10-4 in centimeters.
Table –I: Specification for double-ring infiltrometers experiment The diameter of
Area of annular
Area of annular
The volume of water,
Multiply the volume of water used in ml by
rings (inches)
space (sq in)
space (sq cm)
in ml, providing 1 in.
(A) or (B) to obtain the depth of water
depth (A) Inches
(B) Centimeters
12 and 18
141.4
912.3
2,318
4. 31X10-4
10.96X10-4
12 and 24
339.3
2, 189.2
5,561
1. 80X10-4
4. 57X10-4
5
Journal Pre-proof 197.9
1, 276.9
3. 08X10-4
3,244
7. 83X10-4
All the measured data, as well as the infiltration rates calculated during the progress of the test, are shown in the Tables-1 and 2.
ELECTRICAL RESISTIVITY TOMOGRAPHY (ERT)
of
The principle of the ERT method comprises of the application of constant direct current into the ground
ro
through two current electrodes and measuring the resulting voltage at two potential electrodes (Dahlin and Zhou, 2004; Candansayar, 2008). The ERT method is based on a multi-electrode and multi-cable system spread on the
-p
ground. The position of current and potential electrodes during the measurement is dependent on the chosen
re
geometry of electrode arrays. The most commonly used arrays are the dipole-dipole, Wenner and Wenner–
lP
Schlumberger arrays. Each electrode configuration has specific advantages and disadvantages concerning the penetration depth and the horizontal & vertical resolution. In this study, the Wenner–Schlumberger configuration
na
has been utilized because it provides quite deep penetration, reliable stability and ability to detect both horizontal and vertical subsurface features (Dahlin and Zhou, 2004; Candansayar, 2008).
ur
Electrical Resistivity Tomography (ERT) has become a more and more renowned method over the decade to plot the electrical resistivity of the subsurface with complex geology (Griffiths and Barker 1993; Loke and Barker
Jo
18 and 24
1996; Zarroca et al. 2011; McInnis et al. 2013). Wenner-Schlumberger array was used to attain a good vertical resolution and also it provides a reasonable horizontal resolution (Sasaki 1992). An IRIS Syscal Junior Pro Switch48 resistivity instrument was used, with 24 stainless steel electrodes spaced at 1 m and 5 m electrode separation in the study area to know the Vadose zone thickness and scanning near surface condition in crystalline terrain. In total, seventeen ERT profiles were carried out to comprehend the resistivity variation with depths. The main goal of achieving these datasets was to study the unsaturated zone, which is varying from a depth of 4 to 24 m evidenced in the ERT. We use the RES2DINV software (Loke and Barker 1995; Loke et al. 2003) for the inversion of the apparent resistivity dataset. A least-square inversion method is used for a smooth-constrained inversion algorithm. It divides the subsurface strata into rectangular on the basis of resistivity, which is adjusted to minimize iteratively
6
Journal Pre-proof the difference between the computed and the measured apparent resistivity values; the root means square (RMS) error gives a measure of this difference (Loke and Barker 1996; Sasaki 1992). Generally, the data obtained during ERT field measurements are classically presented as apparent resistivity pseudo-sections, which give an approximate picture of the subsurface resistivity. Later inversion was achieved, which is based on the regularized least-squares optimization method (deGroot-Heldin and Constable, 1990; Loke et al., 2003).
of
RESULTS AND DISCUSSION
ro
Two test sites were selected in the area, which was approximately 10 m away from one other. The site 1, which is close to bore well wherein an infiltrometer was set up to conduct the infiltration test and at the same place
-p
ERT survey was carried out in such a way that the 12th electrode out of 24 electrodes was exactly placed in the inner
re
ring of infiltrometer, so that we can get a deeper information at this infiltrometer and periodically ERT pseudo section was retrieved whereas the infiltration test was uninterrupted till the end. Both the test was started
lP
simultaneously and were continued for 2 hours. Water level in the study area was measured with the manual Water level indicator (WLI) and found to be ~21m. There are 6 bore wells in the study area out of which 4 are in working
na
condition and remaining 2 are abandoned.
ur
At SITE 1 Table (1), represents the entire observation data like time interval, depth of penetration and rate of infiltration, as the time passed on the rate of infiltration was slowly increasing and its depth of penetration was
Jo
also increasing simultaneously but with a slight fluctuating, it is observed that there was an upsurge in the infiltration rate as well as its depth of penetration at 40th,100th and 160th minutes as in fig. (2a & 2b), the same was reflected in the ERT inverted model section, which was monitored for 20 minutes each and shown in ERT’s inverted sections (fig. 3). ERT 1 inverted section was the starting profile (0th minute) wherein it’s seen that a layer of thickness about ~1.3 to 2.5 meters is a sheeting joint sandwiched between the top and weathered zone. ERT 2 inverted section (20th minute) was showing the zone of wetting where water started flowing fast, which in turn results in an increase of infiltration rate was observed but in the case of depth of penetration graph
7
Journal Pre-proof there was a huge fluctuation as water was not flowing deeper into the soil which was dry initially, so it needs to saturate the pores on top surface. ERT 3 inverted section which was recorded at (40th minute) it’s seen that the plume of water after saturating top surface which was infiltrated up to a depth of 1.2 meters has moved rapidly as it has entered sheeting joint (hallow gap) underneath and same changes in slope are observed as in fig. (2a & 2b). ERT 4, 5 inverted sections which were recorded at (60th and 80th minutes) showing the plume movement
of
laterally, increasing the infiltration rate and its depth of penetration.
plume has been seen and it was confirmed by the fig. (2a & 2b).
ro
ERT 6 inverted section which was recorded at (100th minute) at this moment the water and movement of the
-p
ERT 7, 8 inverted sections at (120th and 140th minutes) in this cycle of models section the water is getting
re
infiltrated but not penetrating deep as the previous cycle of water which is infiltrated and is not allowing making the
lP
depth of penetration to decrease and even decrease the gradient of infiltration rate fig. (2a & 2b). ERT 9 inverted section at (160th minute) clearly states that the water that is infiltrated slowly has now
penetration observed.
na
reached that joint creating the plume of water to flow at a higher rate and the vice-versa with the depth of
ur
In the case of infiltration data, we have observed a cyclic pattern like for every 40 minutes the infiltration
Jo
rate gradient is lowered and after that, for 20 minutes the response of the curve was increasing. The data from 0th to 40th minute states that infiltration is gradually increasing and after that, from the 40th minute to 60th minute there is a rapid rise in the infiltration rate as well as the depth of penetration. The same cycle is repeated i.e. from 60th to the 100th minute again there was a very low gradient rise in infiltration rate and for 20 more minutes i.e. 100th to 120th minute we can see a rapid rise of infiltration rate. The same cycle is repeated for 120th to 160th minute the gradient was low and after that, there is an increase in its infiltration rate. In the case of depth of penetration curve, the first and second cycles response of curve was directly proportional to the rate of infiltration but after that 120th to 140th minute cycle, however, the rate of infiltration was low there was no penetration and decline in curve was observed the reason behind could be propelling the former saturated water by the fresh inward water (piston-flow model).
8
Journal Pre-proof SITE 2 was at a distance of about 10 meters from the SITE 1. In this ERT profiles were laid such a way that the 14th electrode was in the inner ring of infiltrometer out of these 24 electrodes. Table (2), represents the entire observation data like time interval, depth of penetration and rate of infiltration, as the time passed on, the rate of infiltration was slowly increasing and its depth of penetration was also increasing and fluctuating but it is observed that there was an upsurge in the infiltration rate as well as its depth of penetration at 20th,40th,100th and 140th minutes as in fig (4a & 4b), the same was reflected in the ERT inverted sections, which was monitored for an interval of 20 minutes each and shown in ERT’s sections (fig. 5).
of
ERT 1 inverted section was the starting profile (0th minute) wherein it's seen that the entire area was
ro
watered so this may be the reason for low resistivity from the top surface.
-p
ERT 2 and 3 inverted sections at (20th and 40th minute) in these sections it's seen that the plume of water is following its path of flow by the gradient. In the fig (4a & 4b) also seen that till 20th minute there is a gradual
re
increase in the depth of penetration and rise in infiltration rate.
lP
ERT 4 and 5 inverted sections at (60th and 80th minute) it is observed that the water is getting accumulated from the top surface and the water is flowing towards the 1st electrode following the trend of the slope. Its again seen
na
that water is getting accumulated and its plume is trying to move very slowly. The response in fig (4a & 4b) shows
minute.
ur
the depth of penetration and rate of infiltration were also decreasing slowly from the time interval of 60 th to 80th
Jo
ERT 6 inverted section at (100th minute) in this section its clearly observed that how the water which was accumulated in the previous interval of time has suddenly moved due to this piston-flow model i.e. the freshwater entering has propelled the older accumulated water and making to the plume flow rapidly and this infiltrated water was flowing in vertically as well as in lateral direction. This was even correlated with the fig (4a & 4b) showing a sudden upsurge in both the rate of infiltration and its depth of penetration. With this study, we can say that water is even flowing in vertical as well as lateral pattern. ERT 7 inverted section at (120th minute) showing the similar pseudo section as it is in the 0th to the 20th minute, showing a slow rise in the rate of infiltration and decreasing trend for the depth of penetration. It indicates the same cyclic pattern again started.
9
Journal Pre-proof ERT 8 inverted section at (140th minute) this model resistivity section is very much similar to this 60th and 80th minute but here there is more lateral spread from the top surface and even the plume is seen flowing the gradient. In the case of infiltration data at site 2, we have observed a similar pattern but not in a cyclic pattern as in the case of site1 but the changes are quite similar if we consider their time i.e. at 20, 100 and 140 th minute, showing a delay pattern when compared with the site 1. The infiltration rate gradient is increasing from the initial time and at 20 minutes the response of the curve was upsurge and the same was observed in the depth of penetration. As the
of
time of infiltration passed on, there was an increasing trend in the rate of infiltration as well as the depth of
ro
penetration. There was a sudden increase in infiltration and depth of penetration at the 100th minute and after that at
-p
140th minute also this increase was observed. All their variations were very well correlated in the ERT results. As per the lateral variation of inverted section we can observe the low resistive zones which are broader at the top
re
and can be concluded as closely spaced vertical joints which is connecting to the sheeting joints. In order to maintain
lP
the equilibrium condition, generally, infiltration rate will be higher at the initial phase and decreases gradually with time to the saturated state. Though, this scenario is different which attributed that the presence of sheeting joint
na
accelerates the passage of water through the joint in a way of preferential flow rather than piston flow. Since piston flow is very much confined to the weathered zone (soil) so it will not be applicable in the case of sheeting joint. By
ur
the virtue of sheeting joint passage of water below the surface is getting easier which impart us an idea to understand
Jo
the subsurface condition. As we can see in the figures (2a, 2b and 4a, 4b) that the general trend of infiltration rate is going on increasing with the small drastic kink during the passage which clearly provide the information that the water rushing through the joint and these scenarios can be justified through the 2D ERT inverted section (Fig. 3 & 5).
CONCLUSION Sheeting joints are the fractures or openings which generally advance parallel to the natural topographical slope and originated by tensile forces and some time it is observed as an outcome of mechanical fracturing which extends laterally over tens to hundreds of meters. The study manifested that there is a sheeting joint with a varying
10
Journal Pre-proof depth of 1-2.5 meter at site 1 and 6-16 meter at site 2. This sheeting joints has played a vital role in this experimental study of continuous monitoring of variation of near-surface resistivity at shallow depths through ERT and the inflow of water within the unsaturated layers by infiltration study at the two different sites in the study area. The evidence of sheeting joint is observed from the ERT results and it has been verified with the infiltration test and their results. It is seen that the infiltrated water is not penetrating deeper and the movement of water is lateral rather than vertical this phenomenon is due to the presence of sheeting joint, which restricts the flow of water to penetrate deeper within the unsaturated layers but might be connected to the aquifer somewhere which is a major finding from this study.
of
This finding can be very vigorous in terms of groundwater recharge through appropriate recharge technique in this near surface stressed condition. Integration of both resistivity and infiltration study impart us the idea about the
ro
existence of sheeting joint below the surface. This robust integrated approach can be upscale to the other regions of
-p
granitic terrain in order to implement recharge techniques, hence this approach can be very effective in terms of
re
groundwater recharge and management.
lP
ACKNOWLEDGMENT
The authors express their sincere gratitude to the Director, CSIR-NGRI, Hyderabad for his continuous
na
support and encouragement for the research activity. The first author acknowledges the cooperation of scientists and colleagues Dr. Dewashish Kumar, Mr. Arun Kumar, Mr. Vinod Kumar, and Mr. Venkatesh and Raj Kumar for their
ur
support and helping constantly in the fieldwork for collecting different types of the data and correcting the
Jo
manuscript. Author would also like to thank the reviewers and Editor for their valuable comments and suggestions to improve the quality of the manuscript. REFERENCES
Aronovici, V.S., 1955. Model study of ring infiltrometer performance under low initial soil moisture: Soil Sci. Soc. America Proc., v. 19, p. 1-6. Arora Tanvi., 2008. Geophysics and Geostatistics: An integrated approach to characterize and monitor the unsaturated zone, Thesis. Barraud, J.P., Dieulin, A., Ledoux, E., de Marsily, G., 1979. Relation entre mesures ge´ophysiques etflux de l'eau dans les sols non sature´s, Rapp. LHM/RD/79/3, Ecole Natl. Supe´ rieure des Mines de Paris, Paris.
11
Journal Pre-proof Bernstone, C., Dahlin, T., Ohlsson, T., Hogland, W., 2000. DC-resistivity mapping of internal landfill structures: two pre-excavation surveys. Environ. Geol. 39 (3–4), 360–371 Besson, A., Cousin, I., Dorigny, A., Dabas, M., King, D., 2008. The temperature correction for the electrical resistivity measurements in undisturbed soil samples: analysis of the existing conversion models and proposal of a new model. Soil Sci. 173 (10), 707–720 Binley, A., Winship, P., West, L.J., Pokar, M., Middleton, R., 2002. Seasonal variation of moisture content
of
in unsaturated sandstone inferred from borehole radar and resistivity profiles. J. Hydrol. 267 (3–4), 160–172.
ro
Binley, A., Kemna, A., 2005. DC resistivity and induced polarization methods. In: Yuram, R., Hubbard, S.S. (Eds.), Hydrogeophysics. Water and Science Technology Library, vol. 50. Springer, New York, pp. 129–156.
-p
Blo¨schl, G., and Sivapalan, M., 1995. Scale issues in hydrological model-ing—A review, Hydrol.
re
Processes, 9, 251 – 290, doi:10.1002/hyp.3360090305
lP
Buselli, G., Lu, K.L., 2001. Groundwater contamination monitoring with multichannel electrical and electromagnetic methods. J. Appl. Geophys. 48 (1), 11–23
na
Candansayar, M.E., 2008. Two-dimensional individual and joint inversion of three and four-electrode array
ur
dc resistivity data. Journal of Geophysics and Engineering 5, 290-300. Colman, E.A., Bodman, G.B., 1944. Moisture and energy conditions during downward entry of water into
Jo
moist and layered soils: Soil Sci. Soc. America Proc., 1943, v. 9, p. 3-11. Cosentino, P., Cimino, A., Riggio, A.M., 1979. Time variations of the resistivity in a layered structure with the unconfined aquifer. Geoexploration, pp. 11–17. Dahlin, T., Zhou, B., 2004. A numerical comparison of 2-D resistivity imaging with 10 electrode arrays. Geophysical Prospecting 52, 379-398. Day-Lewis, F.D., Lane, J.W., Harris, J.M., Gorelick, S.M., 2003. Time-lapse imaging of saline-tracer transport in fractured rock using difference-attenuation radar tomography.Water Resour. Res. 39 (10), 1740–1752.
12
Journal Pre-proof De Carlo, L., Perri, M.T., Caputo, M.C., Deiana, R., Vurro, M., Cassiani, G., 2013. Characterization of a dismissed landfill via electrical resistivity tomography and mise-à-la-masse method. J. Appl. Geophys. 98, 1–10. DeGroot-Hedlin, C., Constable, S.C., 1990. Occam's inversion to generate smooth, two-dimensional models from magnetotelluric data. Geophysics 55, 1613-1624. Depountis, N., Harris, C., Davies, M.C.R., Koukis, G., Sabatakakis, N., 2005. Application of electrical imaging to leachate plume evolution studies under in-situ and model conditions. Environ. Geol. 47 (7), 907–914.
of
Descloitres, M., Ruiz, L., Sekhar, M., Legchenko, A., Braun, J.J., Kumar, M.S.M., Subramanian, S., 2008.
ro
Characterization of seasonal local recharge using electrical resistivity tomography and magnetic resonance sounding. Hydrol. Process.22 (3), 384–394.
-p
Engerrand, C., 2002. Hydrogéologie des socles cristallins fissures a fort recouvrement d’altérites en regime
re
de mousson: étude hydrogéologique de duex bassins versants situés en Andhra Pradesh (Inde). Thése de doctorat,
lP
Université Paris VI
Free, G.R., Browning, G.M., Musgrave, G.W., 1940. Relative infiltration and related physical
na
characteristics of certain soils: U.S. Dept. Agriculture Tech. Bull. 729, 52 p. Friedman, S.P., 2005. Soil properties influencing apparent electrical conductivity: a review. Comput.
ur
Electron. Agr. 46 (1–3), 45–70.
Jo
Griffiths, D.H., Turnbull, J., 1985. A multi-electrode array for resistivity surveying. First Break 3, 16–20. Griffiths, D.H., Turnbull, J., Olayinka, A.I., 1990. Two-dimensional resistivity mapping with a computercontrolled array. First Break 8, 121–129. Griffiths, D.H., Barker, R.D., 1993. Two-dimensional resistivity imaging and modelling in areas of complex geology. J. Applied Geophysics 29, 211–226. Haise, H.R., 1949. Flow pattern studies in irrigated coarse-textured soils: Soil Sci. Soc. America Proc. 1948, v. 13, p. 83-89.
13
Journal Pre-proof Kirkham Don., Feng, C.L., 1949. Some tests of the diffusion theory and laws of capillary flow, in soils: Soil Sci., v. 67, p. 29-40. Klute, A., 1952. Some theoretical aspects of the flow of water in unsaturated soils: Soil Sci. Soc. America Proc., v. 16, p. 144-148. Kohnke Helmut., 1938. A method for studying infiltration: Soil Sci. Soc. America Proc., v. 3, p. 296-303. Loke, M.H., Barker, R.D., 1995. Least-square deconvolution of apparent resistivity pseudo-sections.
of
Geophysics 60(6):499–523.
ro
Loke, M.H., Barker, R.D., 1996. Rapid least-squares inversion of apparent resistivity pseudosections by a
-p
quasi-Newton method. Geophys Prospect 44:131–152
imaging inversion. J. Appl. Geophys. 49, 149–162.
re
Loke, M.H., Dahlin, T., 2002. A comparison of the Gauss-Newton and quasi-Newton methods in resistivity
lP
Loke, M.H., Acworth, I., Dahlin, T., 2003. A comparison of smooth and blocky inversion method in 2D
na
electrical tomography surveys. Explor Geophys 34:182–187. Mahmood, R., 1996. Scale issues in soil moisture modelling: Problems and prospects, Prog. Phys. Geogr.,
ur
20, 273 – 291, doi:10.1177/030913339602000302.
68, p. 359-370.
Jo
Marshall, T. J., Stirk, G.B., 1949. Pressure potential of water moving downward into the soil: Soil Sci., v.
McInnis, D., Silliman, S., Boukari, M., Yalo, N., Orou-Pete, S., Fertenbaugh, C., Sarre, K., Fayomi, H., 2013. Combined application of electrical resistivity and shallow groundwater sampling to assess salinity in a shallow coastal aquifer in Benin, West Africa. J Hydrol 505(15):335–345. Miller, R.D., Richard, Felix., 1952. Hydraulic gradients during infiltration in soils: Soil Sci. Soc. America Proc., v. 16, p. 33-38. Muntz, M.A., 1908. Influence of the permeability of soils on the conditions and success of irrigation: Direction Hydraulique Agricoles Annales, v. 38, p. 17.
14
Journal Pre-proof Nelson, L.B., Muckenhirn, R.J., 1941. Field percolation rates of four Wisconsin soils having different drainage characteristics: Agronomy Jour., v. 33, p. 1028-1036. Reynolds, W., Elrick, D., Youngs, E., Amoozegar, A., Booltink, H., Bouma, J., Clothier, B., Scotter, D., 2002. Methods of Soil Analysis. Part 4. SSSA Book Series. Soil Science Society of America. Richards, L.A., 1952. Report of the Subcommittee on Permeability and Infiltration, Committee on Terminology, Soil Science Society of America: Soil Sci. Soc. America Proc., v. 16, p. 85-88.
of
Sasaki, Y., 1992. Resolution of resistivity tomography inferred from nuERTcal simulation. Geophys
ro
Prospect 40:453–464.
Shima, H., 1990. Two-dimensional automatic resistivity inversion technique using alpha centers.
-p
Geophysics 55, 682–694.
lP
Soil Sci. Soc. America Proc., v. 20, p. 430-440.
re
Soil Science Society of America, 1956, Report of definitions approved by the Committee on Terminology:
Sposito, G., 1998. Scale Dependence and Scale Invariance in Hydrology,423 pp., Cambridge Univ. Press,
na
Cambridge, U. K.
ur
Western, A. W., R. B. Grayson, and G. Blo¨schl., 2002. Scaling of soil moisture: A hydrologic perspective,
Jo
Annu. Rev. Earth Planet. Sci., 30,149 – 180, doi: 10.1146/annurev.earth.30.091201.140434. Wu, L., Pan, M.L., Roberson, Shouse. P., 1997. Numerical evaluation of ring-infiltrometers under various soil conditions. Soil Science, 162:771–777. Wu, L., Pan, L., Mitchel, J., Sanden, B., 1999. Measuring saturated hydraulic conductivity using a generalized solution for single ring infiltrometers. Soil Science Society of America Journal, 63:788–792. Wuest, S., 2005. Bias in ponded infiltration estimates due to sample volume and shape. Vadose Zone Journal, 4:1183–1190. Youngs, E., 1987. Estimating hydraulic conductivity values from ring infiltromete measurements. Journal of Soil Science, 38:623–632.
15
Journal Pre-proof Zarroca, M., Bach, J., Linares, R., Pellicer, X.M., 2011. Electrical methods (VES and ERT) for identifying, mapping and monitoring different saline domains in a coastal plain region (Alt Emporda`, Northern Spain). J Hydrol
Jo
ur
na
lP
re
-p
ro
of
409(1–2):407–422.
16
Journal Pre-proof
FIGURE CAPTIONS Fig. 1: Location map of selected sites at NGRI campus Fig. 2a: Infiltration rates at site 1 Fig. 2b: Depth of penetration at site 1 Fig. 3: ERT inverted section at site 1 exhibiting flow of water through weaker zones. Fig. 4a: Infiltration rates at site 2 Fig 4b: Depth of penetration at site 2
Jo
ur
na
lP
re
-p
ro
of
Fig. 5: ERT inverted section at site 2 showing the passage of water in vadose zone.
17
Journal Pre-proof
Authors contribution Author 1: Taufique warsi
Involved in the blueprint of this work Actively involved in acquiring the data set Helped co-authors Comprehensive writing of paper with the authors support Analysis was done along with Co-authors Involved in the revision of the manuscript
ro
re
-p
Involved in the blueprint of this work Actively involved in acquiring the data set Helped co-authors Comprehensive writing of paper with the authors support Analysis was done along with Co-authors
lP
of
Author 2: V. Satish kumar
na
Author 3: Ratnakar Dhakate
Jo
ur
Involved in designing the experiment Partially involved in the experiment Suggestion was made in order to write the paper
Author 4: C. Manikyamba
Involved in designing the experiment Partially involved in the experiment Suggestion was made in order to write the paper
Author 5: T. Vinoda Rao
Involved in designing the experiment Partially involved in the experiment Suggestion was made in order to write the paper 18
Journal Pre-proof Author 6: R. Rangarajan
Jo
ur
na
lP
re
-p
ro
of
Involved in designing the experiment Partially involved in the experiment Suggestion was made in order to write the paper
19
Journal Pre-proof TABLE 1. INFILTRATION DATA AND CALCULATION OF SITE 1
of
INFILTRATION RATE (mm/minute) 0.00000 0.00009 0.00030 0.00044 0.00059 0.00074 0.00089 0.00101 0.00105 0.00126 0.00127 0.00153 0.00162 0.00171 0.00178 0.00190 0.00217 0.00265 0.00289 0.00337 0.00340 0.00380 0.00399 0.00477 0.00471 0.00529 0.00517 0.00547 0.00577 0.00726 0.00740 0.00810 0.00860 0.00933 0.00961 0.01162 0.01036 0.01058 0.01297 0.01341 0.01316 0.01451 0.01450 0.01555
-p
ro
LEVEL (cm) 15 12.8 14 14 14 14 14 14.1 14.4 14.2 14.5 14.2 14.3 14.4 14.5 14.5 14.3 13.8 13.9 13.7 14 13.9 14 13.6 13.9 13.7 14 14 14 13.4 13.6 13.5 13.5 13.4 13.5 12.9 13.6 13.7 13.1 13.2 13.5 13.3 13.5 13.4
na
lP
re
ACTUAL LEVEL (cm) 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15
ur
WATER ADD (ml) 2000 1554.3 706.5 706.5 706.5 706.5 706.5 635.85 423.9 565.2 353.25 565.2 494.55 423.9 353.25 353.25 494.55 847.8 777.15 918.45 706.5 777.15 706.5 989.1 777.15 918.45 706.5 706.5 706.5 1130.4 989.1 1059.75 1059.75 1130.4 1059.75 1483.65 989.1 918.45 1342.35 1271.7 1059.75 1201.05 1059.75 1130.4
Jo
TIME (minutes) 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 19 21 23 25 27 29 31 33 35 37 39 42 45 48 51 54 57 60 63 66 70 74 78 82 86 90
20
DEPTH (cm) 0 0.706 1.138 1.138 1.138 1.138 1.138 1.106 1.010 1.074 0.978 1.074 1.042 1.010 0.978 0.978 1.042 1.202 1.170 1.234 1.138 1.170 1.138 1.266 1.170 1.234 1.138 1.138 1.138 1.330 1.266 1.298 1.298 1.330 1.298 1.491 1.266 1.234 1.427 1.395 1.298 1.362 1.298 1.330
Journal Pre-proof 13.4 13.3 13 12.5 12.6 12.8 12.9 12.9 13 13.1 13 11.4 11.5 11.6
-p re lP na ur 21
0.01625 0.01752 0.01990 0.02335 0.02412 0.02433 0.02498 0.02614 0.02672 0.02724 0.02899 0.04175 0.04359 0.04535
of
15 15 15 15 15 15 15 15 15 15 15 15 15 15
ro
1130.4 1201.05 1413 1766.25 1695.6 1554.3 1483.65 1483.65 1413 1342.35 1413 2543.4 2472.75 2402.1
Jo
94 99 105 111 117 123 129 135 141 147 153 163 173 183
1.330 1.362 1.459 1.619 1.587 1.523 1.491 1.491 1.459 1.427 1.459 1.972 1.940 1.908
na
ro
INFILTRATION RATE (mm/minute) 0.00000 0.00004 0.00013 0.00018 0.00018 0.00022 0.00022 0.00033 0.00038 0.00040 0.00088 0.00071 0.00138 0.00079 0.00170 0.00118 0.00130 0.00410 0.00462 0.00401 0.00483 0.00623 0.00578 0.00637 0.00696 0.00755 0.00814
re
-p
LEVEL (cm ) 15 12.8 12.7 13.8 14 14 14 14 13.8 14 14 13 13.4 13 13.7 13 13.4 13.2 11.1 11.5 12.1 11.8 11.9 12.2 12.1 12 12.2
lP
ACTUAL LEVEL (cm) 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15
ur
WATER ADD (ml) 5000 600 1100 1000 750 750 630 810 810 750 1490 1000 1670 840 1600 1000 1000 2900 2700 2000 2100 2400 2000 2000 2000 2000 2000
Jo
TIME (minutes) 0 1 2 3 4 5 6 7 8 9 10 12 14 16 18 20 22 24 29 34 39 44 49 54 59 64 69
of
Journal Pre-proof
22
DEPTH (cm) 0 2.5424 2.7694 2.724 2.6105 2.6105 2.55602 2.63774 2.63774 2.6105 2.94646 2.724 3.02818 2.65136 2.9964 2.724 2.724 3.5866 3.4958 3.178 3.2234 3.3596 3.178 3.178 3.178 3.178 3.178
Journal Pre-proof 12.1 12.5 12.4 12.3 12.9 12.8 12.9 12.7 10.4 10.7 10.8 10.7 10.9 11.2
0.00829 0.00792 0.00991 0.00997 0.01053 0.00934 0.00981 0.01993 0.02105 0.02130 0.02230 0.02636 0.02485 0.02542
of
15 15 15 15 15 15 15 15 15 15 15 15 15 15
ro
1900 1700 2000 1900 1900 1600 1600 3100 3000 2800 2720 3000 2650 2550
ur
na
lP
re
-p
TABLE 2. INFILTRATION DATA AND CALCULATION OF SITE 2
Jo
74 79 84 89 94 99 104 109 119 129 139 149 159 169
23
3.1326 3.0418 3.178 3.1326 3.1326 2.9964 2.9964 3.6774 3.632 3.5412 3.50488 3.632 3.4731 3.4277
Journal Pre-proof
HIGHLIGHTS This paper is an integrated study of ERT and infiltration method to decipher the sub-surface strata. The major finding from this study was identifying the sheeting joint.
Jo
ur
na
lP
re
-p
ro
of
This joint could be the sources for recharge and groundwater management
24
Figure 1
Figure 2
Figure 3r1
Figure 3r2
Figure 4
Figure 5r1
Figure 5r2