WO2008081468A1 - Tritium injection technique for the estimation of natural groundwater recharge - Google Patents
Tritium injection technique for the estimation of natural groundwater recharge Download PDFInfo
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- WO2008081468A1 WO2008081468A1 PCT/IN2007/000566 IN2007000566W WO2008081468A1 WO 2008081468 A1 WO2008081468 A1 WO 2008081468A1 IN 2007000566 W IN2007000566 W IN 2007000566W WO 2008081468 A1 WO2008081468 A1 WO 2008081468A1
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- tritium
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- groundwater recharge
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
- G01N33/24—Earth materials
- G01N33/246—Earth materials for water content
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- the present invention relates to a process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain. More particularly, the invention relates to the development of Tritium injection technique for the estimation of natural groundwater recharge by making the use of Tritium as a tracer artificially produced from nuclear reactor.
- Quantification of natural groundwater recharge is one of the most vital parameter as it enables evaluation of groundwater resources and provides significant input for efficient groundwater resource management, in drawing long term plans to develop the water resources, aquifer protection from unacceptable declines and in the protection of quality of water.
- groundwater level fluctuation approach when applied in isolation, is not reliable unless accurate values of specific yield from a reliable method are available. Significant errors thus get introduced in the estimation of recharge.
- the tracer used should behave exactly in a similar manner as that of the material in the system, but shall be at the same time necessarily different from the tracer used in order to enable detection.
- chemical tracers were used in hydrological investigations and are still being used whenever it is convenient viz., sodium chloride, sodium dichromate, potassium permanganate rhodamine, amidorhodamine, uranine, casine etc. Radioactive tracers can however be easily detected in dilutions «10 '6 ppm (Br 82 , I 131 , tritium (HTO)).
- HTO tritium
- PISTON FLOW MODEL proposed by Zimermmann et al. (1967a&b) and Kunststoff (1968 a&b) describes the working principle of the movement of water. This model works on the principle in such a way that the soil moisture moves downward in discrete layers through an unsaturated zone under the force of gravity which otherwise means that any fresh layer of water added to the surface pushes an equal amount of water beneath it further down, and so on.
- the present invention aims to develop tritium injection technique using an artificial tracer Tritium adopting the concept of Piston Flow Model for the estimation of natural groundwater recharge, which obviates the drawbacks of the prevailing processes/techniques.
- the main object of the present invention is to provide the development of tritium injection technique for the estimation of natural groundwater recharge in hard rock terrains, which obviates the drawbacks as detailed above.
- Another object of the present invention is to achieve site-specific estimates of natural groundwater recharge in hard rock terrains.
- Figure 1 represents schematic diagram of tritium injection in the field.
- Figure 2 represents cross section view of soil coring auger.
- Figure 3 shows a schematic diagram of distillation set up fabricated indigenously at NGRI, India where in 6 soil samples can be loaded in round bottom flasks simultaneously for distillation. The distillate is collected in glass ampule and is counted for tritium activity.
- Figure 4 represents a typical tritium activity and its variation with depths in the soil profile.
- Figure 5 represents a profile of recharge at Aregudem
- Figure 6 represents a profile of recharge at Lingajigudem
- the present invention relates to a process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain, the said process comprising the steps of injecting the tritiated water having an activity of 10uC/ml, at a pre-selected soil/field in pre-drilled bore hole having depth in the range of 60 to 120 cm using a drive rod before the onset of monsoon (rainy season), to drill a hole of diameter preferably 12 to 15 mm, allowing the inject of tritiated water as performed in step (a), at the impregnation site for a period in the range of 3 to 12 months (one hydrological cycle), collecting the said soil samples impregnated with tritiated water from step (b) after cessation of monsoon (after rainy season), weighing the soil collected sample in step (c) by a balance having an accuracy of at least 0.5 gm and determining the moisture content of the said samples by Torsion balance (Infra red light) having an accuracy of at least 0.2%, heating the steps of
- the pre-selected soil field is located in granites of Kongal basin, Nalgonda district, Andhra Pradesh, India.
- the borehole is having preferred depth of 80 cm below the root zone.
- the tritium activity is counted by liquid scintillation spectrometer.
- the tritium activity is preferably taken at a section of 10 cm to have a good resolution for precise measurements.
- the present invention provides development of a tritium injection technique for the estimation of natural groundwater recharge in hard rock terrain which works on the principle of the piston flow model, and the soil moisture moves downward in discrete layers through the unsaturated zone under the force of gravity which means any fresh layer of water added to the surface pushes an equal amount of water beneath it further down, and so on, tagging of the artificially produced tritium below the shallow root zone before the onset of monsoon rains and collecting soil core profiles after monsoon, computing the displaced position of tracer indicated by the peak in its concentration distribution which corresponds to spot natural recharge to groundwater over the time interval between the injection of tritium and the collection of the soil core profile by generating a graph between moisture content (%) and tritium activity of samples of each site against depth, determining the displacement of the tracer in order to estimate the natural groundwater recharge.
- the groundwater recharge in hard rock terrain is estimated by computing displacement of tracer, average content in the profile between injection depth and peak position, which could be easily obtained from the field data.
- the preciseness of the recharge estimates are protected and shall not decrease with the decrease in the moisture flux.
- the flow mechanism of moisture in the unsaturated and saturated zones is evaluated. The process developed applies the principle of the piston flow model wherein it is described that soil moisture moves downward in discrete layers through the unsaturated zone under the force of gravity that is any fresh layer of water added to the surface pushes an equal amount of water beneath it further down, and so on.
- the tritium is tagged below the shallow root zone before the onset of monsoon rains and collecting after monsoon.
- the displaced position of tracer is indicated by the peak in its concentration distribution, which corresponds to spot natural recharge of groundwater over the time interval between the injection of tritium and the collection of the soil core profile.
- Moisture content (%) and tritium activity of samples of each site were plotted against depth and the displacement of the tracer was determined to estimate the natural groundwater recharge.
- an approximate selection and distribution of injection sites in the field were identified taking many factors into consideration such as topography, local terrain, soil types, drainage pattern, access, and representative coverage.
- HTO tritiated water
- the hole of 60cm to 120cm depth and 12 to 15mm diameter is made , and tritiated water is injected into the hole through a Cu or stainless steel pipe 4 to 6 mm in diameter inserted into the hole, using a liquid pumping device of required capacity, connected to the pipe.
- the hole is made by using a specially developed drive rod (1) as shown in figure 1(a).
- the Tritium injection point is below the root zone of shrubs and away from active root zone of big plants as shown in fig 1(b). The hole is then filled back with local soil.
- the samples for measuring the tritium activity are taken on the completion of one hydrological cycle for a period in the range of 3 to 12 months.
- Soil samples are collected at the end of monsoon.
- Soil samples in 10 cm sections are collected to a depth of 3.5m by soil coring augers.
- An exemplary embodiment of soil-coring auger as shown in Figure 2 consists of a cap (10) attached to a collar(12) , to the collar a detachable handle(11) is attached .
- a pipe(13) of diameter 40 mm made of C class iron extends from the collar.
- Hammer weights are pounded over the cap to insert the auger into the ground so as to take the samples.
- Hoffer-type augers of varying lengths were fabricated and used for collecting soil core samples.
- the samples are weighed immediately after the collection in the field and double-sealed in plastic bags. Soil moisture is extracted in the laboratory by a vacuum distillation . The moisture content of each sample is determined using a balance preferably a torsion balance (infra red light) having an accuracy of at least 0.2%.
- the samples are then heated preferably in the temperature range of 100 to 150 degree C and mixed with insta-gel . The tritium activity of every 10 cm section is then counted and plotted against the sample depth for the entire profile and displacement of tritium is computed.
- a hole (2) is made by using a specially developed drive rod (1) as shown in figure 1(a),then as shown in figure 1(c) 2.5ml of tritiated water (HTO) having an activity 10 ⁇ C/ml i.e 25uC is injected at 80 cm depth in a 12.5mm diameter hole (2),through a stainless steel pipe(5) inserted into the hole.
- the pipe has a diameter of 4 mm and is connected to a 5 to 10 cc syringe (3) through a polythene pipe bend(4).
- the hole is filled back with local soil. Soil samples in 10 cm sections are collected at the end of the monsoon to a depth of 3.5m by soil coring augers.
- FIG. 3 A vacuum distillation set up used is shown in Figure 3 consists of a heater assembly (18) fitted with round bottom flasks(17) having sockets(15). Tubings (14) of diameter 3 mm made up of brass extend from sockets and pass through the condenser(water tank)(16) . The said tubings extend from the condenser into glass ampules(21) through rubber cork(20) fitted on the mouth of the glass ampules.
- the tubings are attached to vacuum pump through a pipe (19) , to which a vacuum gauze(22) is also attached .
- the moisture content of each sample was determined using a torsion balance. Samples were heated at 105 0 C by an infra-red lamp. 4 ml distillate was mixed with 10 ml of insta-gel (a universal liquid scintillation cocktail for counting aqueous and non-aqueous samples, manufactured by Packard Instrument Company, USA) in low potash glass vials, and the tritium activity was counted using Liquid Scintillation Spectrometer having background of about 25 counts per minute. The tritium activity of every 10 cm section was plotted against the sample depth for the entire profile and displacement of tritium is computed. An example of such plot is shown in figure 4.
- EXAMPLE-1 A small quantity of 2.5ml of tritiated water (activity 10 ⁇ C/ml) was injected at 80cm depth below the root zone in a 1.25 cm diameter hole using a drive rod at Aregudem of Kongal river basin, Nalgonda district, Andhra Pradesh, India. The hole was filled back by local soil. The soil samples were weighed immediately after the collection in the field and double-sealed in plastic bags. Hoffer-type augers of varying lengths were used. Soil moisture was extracted in the laboratory by vacuum distillation set up. The moisture content in about 25 gm of soil taken from each sample was determined by a torsion balance and heated by an infra-red oven at 105 0 C.
- This technique is conceptually simple and gives a site-specific estimate of natural groundwater recharge in hard rock terrain.
- This technique also is useful in evaluating the flow dynamics of unsaturated and saturated zones by detecting the path of tracer (tritium) movement.
- Piston flow model describes that the soil moisture moves downward in discrete layers through an unsaturated zone under the force of gravity which otherwise means that any fresh layer of water added to the surface pushes an equal amount of water beneath it further down, and so on. Thus water of the last layer in the unsaturated zone is added to water table.
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Abstract
A technique for quantitatively measuring the characteristic physical parameters of a porous medium viz. 'natural groundwater recharge', in hard rock terrain is developed by using radioactive isotope 'TRITIUM' as a tracer, which is an isotope of Hydrogen (H3). Tritium is tagged to a layer of soil in the unsaturated zone before the onset of monsoon. The tracer moves downwards in discrete layers due to rainfall input based on the working principle of Piston Flow Model. The tritium is subsequently detected after the cessation of the monsoon rains. Measurement of the displacement of tracer together with moisture content of soil due to certain rainfall during the elapsed time provides natural groundwater recharge.
Description
"TRITIUM INJECTION TECHNIQUE FOR THE ESTIMATION OF NATURAL
GROUNDWATER RECHARGE"
Field of the invention: The present invention relates to a process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain. More particularly, the invention relates to the development of Tritium injection technique for the estimation of natural groundwater recharge by making the use of Tritium as a tracer artificially produced from nuclear reactor.
Background and Prior Art of the invention:
Quantification of natural groundwater recharge is one of the most vital parameter as it enables evaluation of groundwater resources and provides significant input for efficient groundwater resource management, in drawing long term plans to develop the water resources, aquifer protection from unacceptable declines and in the protection of quality of water.
Estimation of natural groundwater recharge, by any method, is normally subject to many uncertainties and errors. Besides its estimation, determination of recharge variability in space and time is to be determined and this requires additional investigations to resolve it.
Available techniques used for estimating groundwater recharge can be classified into physical and chemical methods. In physical methods, one determines soil water balance, hydrologic balance, unsaturated hydraulic conductivity and gradient of water potential by processing hydro-meteorological and soil crop data, water table fluctuations and estimation of water flux beneath the root zone (Jacobus et al., 2002; Bridget et al., 2002 and Mondal & Singh 2004), whereas chemical and isotopic analysis of pore fluids from the unsaturated and saturated zones are conducted with the help of measurements of chemical methods (Edmunds, 1980). The groundwater level fluctuation approach, when applied in isolation, is not reliable unless accurate values of specific yield from a reliable method are available. Significant errors thus get introduced in the estimation of recharge. One should distinguish between specific yield and fill able porosity, as the later is smaller because of hysteresis. Calculation of recharge values based on
observed water level fluctuations and the ultimate specific yield values are usually over estimated (Sophocleous, 1985). There are various methods including hydro-geological and hydrological suitable to study spatial and temporal variations of recharge (Sharma, 1987; Simmer, 1987 and Sharma et al, 1991). For arid and semi-arid regions, most of these methods provide long term average estimate of natural groundwater recharge rates. While understanding the behavior of any dynamic system, material is transported from one part of the system to another. It is a common practice to use a tracer to track the material of interest. The requirements are that the tracer used should behave exactly in a similar manner as that of the material in the system, but shall be at the same time necessarily different from the tracer used in order to enable detection. Before the advent of radioactive tracers, chemical tracers were used in hydrological investigations and are still being used whenever it is convenient viz., sodium chloride, sodium dichromate, potassium permanganate rhodamine, amidorhodamine, uranine, casine etc. Radioactive tracers can however be easily detected in dilutions «10'6 ppm (Br82, I131, tritium (HTO)). As most of the prevailing techniques/processes are very laborious, expensive, require highly sophisticated field equipment and requirement of large data, larger site-specific measurements, need for regular monitoring (sometimes which even run for several years) and to determine certain parameters, which are very difficult to estimate accurately.
The concept of water movement through soil termed as PISTON FLOW MODEL proposed by Zimermmann et al. (1967a&b) and Munich (1968 a&b) describes the working principle of the movement of water. This model works on the principle in such a way that the soil moisture moves downward in discrete layers through an unsaturated zone under the force of gravity which otherwise means that any fresh layer of water added to the surface pushes an equal amount of water beneath it further down, and so on.
Objects of the invention:
The present invention aims to develop tritium injection technique using an artificial tracer Tritium adopting the concept of Piston Flow Model for the
estimation of natural groundwater recharge, which obviates the drawbacks of the prevailing processes/techniques.
Thus, the main object of the present invention is to provide the development of tritium injection technique for the estimation of natural groundwater recharge in hard rock terrains, which obviates the drawbacks as detailed above.
Another object of the present invention is to achieve site-specific estimates of natural groundwater recharge in hard rock terrains.
Still another object of the present invention is to protect preciseness in recharge values over other prevailing techniques. Yet another object of the present invention is to evaluate flow mechanism of moisture in the unsaturated and saturated zones.
Brief description of the drawings:
In the drawings accompanying this specification Figure 1 represents schematic diagram of tritium injection in the field. Figure 2 represents cross section view of soil coring auger. Figure 3 shows a schematic diagram of distillation set up fabricated indigenously at NGRI, Hyderabad where in 6 soil samples can be loaded in round bottom flasks simultaneously for distillation. The distillate is collected in glass ampule and is counted for tritium activity.
Figure 4 represents a typical tritium activity and its variation with depths in the soil profile.
Figure 5 represents a profile of recharge at Aregudem
Figure 6 represents a profile of recharge at Lingajigudem
Summary of the invention:
Accordingly, the present invention relates to a process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain, the said process comprising the steps of injecting the tritiated water having an activity of 10uC/ml, at a pre-selected soil/field in pre-drilled bore hole having depth in the range of 60 to 120 cm using a drive rod before the onset of monsoon (rainy season), to drill a hole of diameter preferably 12 to 15 mm, allowing the inject of tritiated water as performed in step (a), at the impregnation
site for a period in the range of 3 to 12 months (one hydrological cycle), collecting the said soil samples impregnated with tritiated water from step (b) after cessation of monsoon (after rainy season), weighing the soil collected sample in step (c) by a balance having an accuracy of at least 0.5 gm and determining the moisture content of the said samples by Torsion balance (Infra red light) having an accuracy of at least 0.2%, heating the said samples as obtained in step (d) preferably in the temperature range of 100 to 105 degree C and mixing with insta-gel, counting the tritium activity and finally plotting the tritium activity, as counted in step (e), of every 10 cm section against the sample depth for the entire soil profile to compute the natural groundwater recharge. In an embodiment of the present invention, the pre-selected soil field is located in granites of Kongal basin, Nalgonda district, Andhra Pradesh, India. In another embodiment of the present invention, the borehole is having preferred depth of 80 cm below the root zone. In a further embodiment of the present invention, the tritium activity is counted by liquid scintillation spectrometer.
In yet another embodiment of the present invention, the tritium activity is preferably taken at a section of 10 cm to have a good resolution for precise measurements.
Detailed description of the invention:
The present invention provides development of a tritium injection technique for the estimation of natural groundwater recharge in hard rock terrain which works on the principle of the piston flow model, and the soil moisture moves downward in discrete layers through the unsaturated zone under the force of gravity which means any fresh layer of water added to the surface pushes an equal amount of water beneath it further down, and so on, tagging of the artificially produced tritium below the shallow root zone before the onset of monsoon rains and collecting soil core profiles after monsoon, computing the displaced position of tracer indicated by the peak in its concentration distribution which corresponds to spot natural recharge to groundwater over the time interval between the injection of tritium and the collection of the soil core profile by generating a graph between moisture content (%) and tritium activity of samples of each site against depth,
determining the displacement of the tracer in order to estimate the natural groundwater recharge.
In accordance with the embodiment of the present invention, the groundwater recharge in hard rock terrain is estimated by computing displacement of tracer, average content in the profile between injection depth and peak position, which could be easily obtained from the field data.
In accordance with the embodiment of the present invention, the preciseness of the recharge estimates are protected and shall not decrease with the decrease in the moisture flux. In accordance with the embodiment of the present invention, the flow mechanism of moisture in the unsaturated and saturated zones is evaluated. The process developed applies the principle of the piston flow model wherein it is described that soil moisture moves downward in discrete layers through the unsaturated zone under the force of gravity that is any fresh layer of water added to the surface pushes an equal amount of water beneath it further down, and so on. The tritium is tagged below the shallow root zone before the onset of monsoon rains and collecting after monsoon. The displaced position of tracer is indicated by the peak in its concentration distribution, which corresponds to spot natural recharge of groundwater over the time interval between the injection of tritium and the collection of the soil core profile. Moisture content (%) and tritium activity of samples of each site were plotted against depth and the displacement of the tracer was determined to estimate the natural groundwater recharge. In this process, an approximate selection and distribution of injection sites in the field were identified taking many factors into consideration such as topography, local terrain, soil types, drainage pattern, access, and representative coverage.
A small amount of tritiated water (HTO) having an activity 10μC/ml is injected into the soil or field in a pre-drilled hole on the onset of monsoons. The hole of 60cm to 120cm depth and 12 to 15mm diameter is made , and tritiated water is injected into the hole through a Cu or stainless steel pipe 4 to 6 mm in diameter inserted into the hole, using a liquid pumping device of required capacity, connected to the pipe. The hole is made by using a specially developed drive rod (1) as shown in figure 1(a).The Tritium injection point is below the root zone
of shrubs and away from active root zone of big plants as shown in fig 1(b). The hole is then filled back with local soil. Care is taken during selection of injection site, a relatively flat patch of non-irrigated land (fellow patch of land) sufficiently far off from the big trees, near important land marks such as milestone, electric poles and small trees, etc. The ploughed or un-ploughed farm plot having no facility of well or irrigation canal is suitable to study the rainfall recharge. Every location of injection site is precisely identified through triangulation as shown in fig 1 (d) so that it could be relocated easily for collection of vertical soil core profiles after the cessation of monsoon rains. Tritiated water injection points (7) are separated from center(6) by 5 cm. Field identification markers (8) are separated from center by 1 m., and permanent and/or temporary bearings for site relocation (9) form a triangle with the center.
The samples for measuring the tritium activity are taken on the completion of one hydrological cycle for a period in the range of 3 to 12 months. Soil samples are collected at the end of monsoon. Soil samples in 10 cm sections are collected to a depth of 3.5m by soil coring augers. An exemplary embodiment of soil-coring auger as shown in Figure 2, consists of a cap (10) attached to a collar(12) , to the collar a detachable handle(11) is attached . A pipe(13) of diameter 40 mm made of C class iron extends from the collar. Hammer weights are pounded over the cap to insert the auger into the ground so as to take the samples. Hoffer-type augers of varying lengths were fabricated and used for collecting soil core samples. The samples are weighed immediately after the collection in the field and double-sealed in plastic bags. Soil moisture is extracted in the laboratory by a vacuum distillation .The moisture content of each sample is determined using a balance preferably a torsion balance (infra red light) having an accuracy of at least 0.2%. The samples are then heated preferably in the temperature range of 100 to 150 degree C and mixed with insta-gel . The tritium activity of every 10 cm section is then counted and plotted against the sample depth for the entire profile and displacement of tritium is computed.
In an exemplary embodiment a hole (2) is made by using a specially developed drive rod (1) as shown in figure 1(a),then as shown in figure 1(c) 2.5ml of tritiated water (HTO) having an activity 10μC/ml i.e 25uC is injected at 80 cm
depth in a 12.5mm diameter hole (2),through a stainless steel pipe(5) inserted into the hole. The pipe has a diameter of 4 mm and is connected to a 5 to 10 cc syringe (3) through a polythene pipe bend(4). The hole is filled back with local soil. Soil samples in 10 cm sections are collected at the end of the monsoon to a depth of 3.5m by soil coring augers. The samples are weighed immediately after the collection in the field by a balance having an accuracy of at least of 0.5 gm and double-sealed in plastic bags. Soil moisture is extracted in the laboratory by a vacuum distillation. A vacuum distillation set up used is shown in Figure 3 consists of a heater assembly (18) fitted with round bottom flasks(17) having sockets(15). Tubings (14) of diameter 3 mm made up of brass extend from sockets and pass through the condenser(water tank)(16) . The said tubings extend from the condenser into glass ampules(21) through rubber cork(20) fitted on the mouth of the glass ampules. The tubings are attached to vacuum pump through a pipe (19) , to which a vacuum gauze(22) is also attached . The moisture content of each sample was determined using a torsion balance. Samples were heated at 1050C by an infra-red lamp. 4 ml distillate was mixed with 10 ml of insta-gel (a universal liquid scintillation cocktail for counting aqueous and non-aqueous samples, manufactured by Packard Instrument Company, USA) in low potash glass vials, and the tritium activity was counted using Liquid Scintillation Spectrometer having background of about 25 counts per minute. The tritium activity of every 10 cm section was plotted against the sample depth for the entire profile and displacement of tritium is computed. An example of such plot is shown in figure 4.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention:
EXAMPLE-1 A small quantity of 2.5ml of tritiated water (activity 10μC/ml) was injected at 80cm depth below the root zone in a 1.25 cm diameter hole using a drive rod at Aregudem of Kongal river basin, Nalgonda district, Andhra Pradesh, India. The hole was filled back by local soil. The soil samples were weighed immediately
after the collection in the field and double-sealed in plastic bags. Hoffer-type augers of varying lengths were used. Soil moisture was extracted in the laboratory by vacuum distillation set up. The moisture content in about 25 gm of soil taken from each sample was determined by a torsion balance and heated by an infra-red oven at 1050C. Four-milliliter (ml) distillate was mixed with 10ml of insta-gel (a universal liquid scintillation cocktail for aqueous and non-aqueous samples, manufactured by Packard Instrument Company, USA) in low potash glass vials, and the tritium activity was counted using liquid scintillation counter having background of about 25 counts per minute. The tritium activity of every 10 cm section was plotted against its sample depth for the profile, which is shown in Figure 5. The value of the natural groundwater recharge is 1.2cm at this village.
EXAMPLE-2
Similarly, the above technique is applied in the other village, named Lingojigudem, Nalgonda District, Andhra Pradesh, India. The tritium activity of every 10 cm section was plotted against its sample depth for the profile, which is shown in Figure 6. The recharge value is 4.7 cm. These studies measure the total natural groundwater recharge taken place during a certain period, which is estimated by using this technique. The total rainfall during the corresponding period is 102 MCM and thus the fractional amount of recharge is 5 % of the rainfall.
The main advantages of the present invention:
1. Artificial Tritium, a radioactive isotope of hydrogen, a soft β-particles emitter having maximum energy 18Kev, a waste product obtained from nuclear reactors, having a half-life of 12.26 years, is of vital importance in groundwater investigations since there is no significant loss or delay in transit of the tritium tracer due to absorption in the soil medium.
2. The health hazard in handling tritium is negligible, as the Tritium used in these studies emits radiation, which is below the recommended permissible limit of International Atomic Energy Agency.
3. This technique is conceptually simple and gives a site-specific estimate of natural groundwater recharge in hard rock terrain.
4. This technique protects the preciseness of the recharge estimates and shall not decrease as the moisture flux to groundwater decreases.
5. This technique also is useful in evaluating the flow dynamics of unsaturated and saturated zones by detecting the path of tracer (tritium) movement.
6. Piston flow model describes that the soil moisture moves downward in discrete layers through an unsaturated zone under the force of gravity which otherwise means that any fresh layer of water added to the surface pushes an equal amount of water beneath it further down, and so on. Thus water of the last layer in the unsaturated zone is added to water table.
References:
Bridget, R. Scanlon, Richard W. Healy and Peter G. Cook, (2002). Choosing appropriate techniques for quantifying groundwater recharge, Hydrogeology
Journal, 10, pp. 18-39. Edmunds WM, Walton NRG (1980). A geochemcial and isotopic approach to recharge evaluation in semi-arid zones: past and present, In: Arid-zone hydrology: investigation with isotope techniques, IAEA-AG_-158/4, IAEA, Vienna, pp. 47-68.
Jacobus, J., Vries, de and Simmers Ian (2002). Groundwater recharge: an overview of processes and challenges, Hydrogeology Journal, 10, pp. 5-17.
Mondal, N. C. and Singh, V.S. (2004). A New Approach to Delineate the
Groundwater Recharge Zone in Hard Rock Terrain, Current Science, Vol. 87,
No.5, 10 Sept. 2004, pp. 658-662.
Munich, K.O., (1968a), Moisture movement measured by isotope tagging, Guidebook on Nuclear techniques in Hydrology, IAEA, Vienna, pp. 112-118.
Munich, K.O., (1968b), Use of Nuclear techniques for the determination of groundwater recharge rates, Guidebook on Nuclear techniques in Hydrology,
IAEA, Vienna, pp. 191-197.
Sharma M. L., Bah M. and Byrne J., Dynamics of seasonal recharge beneath semi-arid vegetation on the gnangara mound, Western Australia Hydrological
Processes, 1991 , Vol. 5, pp383-398.
Sharma M. L., Measurement and prediction of natural groundwater recharge - an overview, J. Hydrol. NZ 25, 1987, pp. 49-56.
Simmer, (1987), Estimation of natural groundwater recharge, D. Reidel Publish. Co. Dordrecht/Boston, pp.510.
Sophocleous M., (1985). The role of specific yield in groundwater recharge estimations: A numerical study, Groundwater, Vol. 23, No. 1 , pp.52-58
Zimmermann, U. Ehhalt, D. and Munnich, O.K. (1967a). Soil water movement and evapotranspiration: Isotopes in Hydrology, IAEA, Vienna, pp. 567-585. Zimmermann, U. Munnich, O.K. and Roetgher, W (1967b). Downward movement of soil moisture traced by means of hydrogen isotopes, American
Geophysical Monograph, 11 , pp.28-36.
Claims
1. A process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain, the said process comprising the steps of: (a) injecting the tritiated water having an activity of 10uC/ml, at a pre-selected soil/field in pre-drilled bore hole having depth in the range of 60 to 120 cm using a drive rod before the onset of monsoon (rainy season), to drill a hole of diameter preferably 12 to 15 mm,
(b) allowing the impregnation of tritiated water as injected in step (a), at the impregnation site for a period in the range of 3 to 12 months (one
N hydrological cycle),
(c) collecting the said soil samples impregnated with tritiated water from step (b) after cessation of monsoon (after rainy season),
(d) weighing the soil collected sample in step (c) by a balance having an accuracy of at least 0.5 gm and determining the moisture content of the said samples by Torsion balance (Infra red light) having an accuracy of at least 0.2%,
(e) heating the said samples as obtained in step (d) preferably in the temperature range of 100 to 105 degree C and mixing with insta-gel, and counting the tritium activity,
(T) plotting the tritium activity, as counted in step (e), of every 10 cm section against the sample depth for the entire soil profile to compute the natural groundwater recharge.
2. A process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain according to claim 1 wherein, the preselected soil field is located in granites of Kongal basin, Nalgonda district, Andhra Pradesh, India.
3. A process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain according to claim 1 wherein, the bore hole is having preferred depth of 80 cm below the root zone.
4. A process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain according to claim 1 wherein, the tritium activity is counted by liquid scintillation spectrometer.
5. A process for the estimation of natural groundwater recharge using tritium injection technique in hard rock terrain according to claim 1 wherein, tritium activity is preferably taken at a section of 10 cm to have a good resolution for precise measurements.
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Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104360036A (en) * | 2014-11-05 | 2015-02-18 | 北京市水利规划设计研究院 | In-situ aeration zone solution monitoring device and in-situ aeration zone ammonia nitrogen enhanced nitration system and method |
| CN108073779A (en) * | 2016-11-09 | 2018-05-25 | 中国辐射防护研究院 | The evaluation method of tritium concentration in plant and plant product |
| CN110850064A (en) * | 2019-12-03 | 2020-02-28 | 安徽省（水利部淮河水利委员会）水利科学研究院（安徽省水利工程质量检测中心站） | Method for detecting new and old water flowing on slope surface and in soil |
| US20220111304A1 (en) * | 2019-06-10 | 2022-04-14 | Zhejiang Hengda Instrumentation Co., Ltd. | Automatic tritium extraction method for environmental monitoring |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104360036A (en) * | 2014-11-05 | 2015-02-18 | 北京市水利规划设计研究院 | In-situ aeration zone solution monitoring device and in-situ aeration zone ammonia nitrogen enhanced nitration system and method |
| CN108073779A (en) * | 2016-11-09 | 2018-05-25 | 中国辐射防护研究院 | The evaluation method of tritium concentration in plant and plant product |
| US20220111304A1 (en) * | 2019-06-10 | 2022-04-14 | Zhejiang Hengda Instrumentation Co., Ltd. | Automatic tritium extraction method for environmental monitoring |
| CN110850064A (en) * | 2019-12-03 | 2020-02-28 | 安徽省（水利部淮河水利委员会）水利科学研究院（安徽省水利工程质量检测中心站） | Method for detecting new and old water flowing on slope surface and in soil |
| CN110850064B (en) * | 2019-12-03 | 2021-12-03 | 安徽省（水利部淮河水利委员会）水利科学研究院（安徽省水利工程质量检测中心站） | Method for detecting new and old water flowing on slope surface and in soil |
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