MANAGEMENT OF GROUNDWATER SALINITY IN MAHARASHTRA - INDIA
HIMANSHU JOSHI
Associate Professor, Dept. of Hydrology, IIT-Roorkee, Roorkee – 247667, INDIA
P.P. BIRDE
Geologist, Groundwater Surveys & Development Agency, Pune, Maharashtra, INDIA
BHISHM KUMAR
Head, Nuclear Hydrology Division, N.I.H., Roorkee – 247667, INDIA
Parts of the area falling under Purna river basin in Amaravati district of Maharashtra are characterized by the groundwater salinity problem. The Groundwater Surveys and Development Agency of Maharashtra state (India) took up an “Induced Recharge Project” some time back, whereby the river water of good quality was used for recharging the saline groundwater in the aquifers adjoining the river courses. A large number of wells were drilled along the riverbanks. To assess the performance of this project, water samples from different rivers draining the study area and several wells were collected and analyzed for major ions, trace elements and stable isotopes 18O and D. Results indicate that about 72% of the induced recharge wells are performing well and are reflecting improved recharge.
INTRODUCTION
Water is essential for sustenance of life. The knowledge of the occurrence, replenishment and recovery of potable groundwater assumes special significance in quality-deteriorated regions, because of scarce presence of surface water. In addition to this, unfavorable climatic condition i.e. low rainfall with frequent occurrence of dry spells, high evaporation etc. on one hand and an unsuitable geological set up on the other, a definite limit on the effectiveness of surface and subsurface reservoirs. During recent years, stupendous growth of population and development of the area has compelled the users to adopt management practices for better conservation of water resources. Artificial recharge is one of the measures, which is taken where natural replenishment of recharge of water is not possible (Todd, [13]).
Alluvial valley of Purna river and its tributaries occupy parts of districts of Amravati, Akola and Buldhana of Maharashtra, India (Fig. 1). Out of a total area of about 7500 sq.km, 2956 sq.km is characterized by saline waters. The quality of shallow as well as deep ground water in this area is so saline that the villagers are bound to depend on Regional Piped Water Supply (RPWS) for drinking water and only rain fed crops are being cultivated. There are 342 villages falling in this saline zone, out of which, villages at the tail end of RPWS are facing acute drinking water shortage. In summer, due to inadequate supply of water, they have to depend on water supply through tankers. In order to find a long-term solution to this problem, Groundwater Surveys And Development Agency, Maharashtra (G.S.D.A.) launched on Induced Recharge Project in 1996. In this project, it was envisaged to create a reverse hydraulic gradient by continuous pumping of ground water from tubewells resulting in attainment of induced recharge of fresh water from river Purna to the affected aquifers in the saline tract (G.S.D.A., [4]). This study provides brief details of the salinity management program and results of performance evaluation done to assess its effectiveness.
STUDY AREA
Amravati district of Maharashtra state in India, is a part of alluvial valley of Purna basin. The district lies between latitude 200, 37’ and 210, 26’ N and longitudes 760, 37’ and 780, 27’ E in northeastern part of Maharashtra. The district covers an area of about 12,212 sq.km, out of which 3053 sq.km (25%) is covered by Purna alluvium. The salinity-affected area is 1756 sq.km. (58% of alluvium) and occurs along central part of river basin, which is located in northwestern part of the district. The salinity in shallow as well as deep groundwater on one hand and scarcity of surface storage due to low rainfall on the other makes the situation worse for management of water resources for both drinking irrigation and industrial use.
Purna alluvial deposit exhibits an alluvial topography. The area lies between the elevations 275 to 395 meters above mean sea level. It is having high relief in north and moderate to low relief in south. The maximum temperature recorded during the summer is 450C and minimum in winters is 100C. The study area is characterized by low rainfall with the average annual rainfall being 790 mm. The major drainage in the study area is Purna river, which originates from Bhainsdevi in Betul district of Madhya Pradesh at a height of just over 760 m in the Satpura hills. The Purna river runs in NNE-SSW direction and takes a right turn at village Amla and flows further in the East-West direction through central part of the saline tract. The main tributaries are Chandrabhaga, Shanoor and Bordi, all of which originate in Satpura ranges. The drainage pattern of Purna river in general is dendritic type.
Rock types exposed in the area are Upper Gondwana, Infra trappean bed, Deccan trap and Quaternary. Pre Quaternary geology and Quaternary geology is dealt with after the work of Ravishankar [10] and Tiwari et.al. [12]. The thick alluvial deposits in Purna alluvial tract appears to be of fluvial origin and were deposited in the actively subsiding graben or fault trough (Adyalkar, [1]). The CGWB, based on detailed survey and exploratory drilling at 28 sites classified subsurface geology of alluvial deposits in two broad groups (Dev Burman and Mehta, [3]). Younger alluvium is about 70-80 m thick consisting of sub-angular to surrounded gravels with sand, silt and clay. Older Alluvium is more than 250 m thick and consists mainly of yellowish clay with gravel and sand at the base. It is having finer sediment.
In younger alluvium, in general, 3 to 10 individual granular zones of varying thickness are encountered with a cumulative thickness of about 30 m (Table 1). Fence diagram of the study area highlights different horizons of multi aquifer system. 1st aquifer occurs in between 7 to 20 m, second in between 30-40 m and the third in the range of 56-62 m. The hydrogeological reports of Central Ground Water Board (CGWB) and GSDA indicate that the general ground water slope is parallel to topography towards south. At shallow depths, the ground water is under pheratic conditions. The deeper zone is under semiconfined conditions.
Table 1. Characteristics of hydrogeological feature of younger and older alluvium in
Amravati district, Maharashtra
No. / Characteristics / Younger Alluvium / Older AlluviumRange / Average / Range / Average
1. / Thickness (m) / 70-80 / - / >250 / -
2. / Thickness of granular zones / 10-50 / 30 / <1-43 / 5
3. / Percentage of granular horizons / 35-82 / 65 / <1-10 / <1
4. / No. of granular horizons / 3-10 / 5 / 1-3 / 2
5. / Yield in m3/day / 5-30 / 20 / 1-300 / <5
6. / Transmissivity m2/day / 88-1820 / 800 / 357 / 357
7. / Specific yield/storage / 6x10-3
3x10-6 / 3x10-4 / 1.5x10-4
1.3x10-4 / 1.4x10-4
SALINITY MANAGEMENT THROUGH INDUCED RECHARGE
Way back, Kailasons [6] and Mathew [9] conducted geophysical survey of the Purna valley by electrical resistivity method and suggested possibility of separating the saline water zone. Roy [11] also tried to delineate the saline tract by drilling 14 boreholes. Mathuraman et al. [9] described the origin of saline water as diagenetically altered meteoric water having a long residence time. GSDA carried out a pilot project of Induced recharge at village Dapura, Distt. Akola in 1962 and found positive indications of pumping.
GSDA launched an ambitious “Induced Recharge Project” in the study area in 1996 to improve the water quality of the groundwater, by drilling wells closer to river courses, and pumping out large quantities of saline water. It was envisaged that this activity would lead to reverse groundwater gradient thereby inducing the river water to recharge the saline aquifers. A total of 342 villages were targeted. Out of the targeted 342 villages, the categorization of villages was done (G.S.D.A., [5]), thirty-four villages were found to have sweet water whereas twenty-one villages needed partial mixing; one hundred thirty-two villages required further monitoring with continuous pumping for improvement of quality; seventy-three villages were not suitable for construction of projects and lastly eighty-three villages were yet to be tackled.
After commencement of the induced recharge project in 1996, about 293.30 lacs of rupees were spent and 132 tubewells were constructed for monitoring purpose. As the entire saline alluvium was not suitable for constructing Induced Recharge wells, wells constructed in Younger alluvium have been observed to give good results as compared to older alluviums. Area favorable for construction of tube well in the river section (Fig. 2) clearly indicates importance of site selection for project wells.
DATA AVAILABILITY AND PROCESSING
Data acquisition was carried out in two stages i.e. collection of available data and collection of water samples. Available data of lithologs, observation wells and chemical analysis as routinely collected by Ground Water Surveys and Development Agency, Amravati, Maharashtra has been obtained for establishing lithological correlation, assessment of groundwater movement and chemical changes with time. Thirty-three (33) groundwater samples were collected from tubewells, hand pumps and project wells of the study area.River water samples were collected from five (5) locations in River Purna, Chandrabhaga and Sahanoor respectively. Rainwater sample was also collected at Amravati to determine isotopic nature.
Field analyses were performed for estimation of temperature, pH, electrical conductivity, alkalinity and dissolved oxygen. For the laboratory chemical and isotopic analyses, the water samples collected from different sources as indicated above were analysed for major elements, Oxygen-18, Deuterium, Tritium and Heavy Metals. Standard procedures were followed for monitoring and analyses. Finally, the information generated from the above analyses alongwith the background information of geohydrology etc. was processed to draw meaningful conclusions.
PERFORMANCE EVALUATION OF INDUCED RECHARGE WELLS
An attempt has been made to evaluate the performance of the project wells located in the study area employing the hydrochemical and isotopic approaches.
Hydrochemical approach
In this approach, the relevant data pertaining to the samples collected from the project wells particularly on Dissolved Oxygen and major ions have been used. In addition, data available historical data on TDS/chloride have also been used in conjunction with the data acquired during the present study for time series analyses to discern trends in the water quality. Dissolved oxygen of river water is usually observed to be higher than groundwater and therefore, mixing of river water with groundwater may elevate the DO levels of groundwater, if there is no prominent biological activity during the process of infiltration as well as mixing with groundwater in the saturated zone. Analysis of 17 project wells on the basis of above preliminary fact revealed that most effective recharge was apparent at 4 villages. Rest of the wells did not exhibit effective recharge.
The TDS and chloride concentrations, measured by GSDA at 14 out of 17 sampling stations, since 1996, have been analysed. A declining trend in TDS and Chloride values is reflected at 11 sampling stations whereas an increasing trend is reflected at 2 project wells. Further, no trend is observed at 2 project wells. However, a in many of the above cases, a closer look at the trend patterns exhibits wide fluctuations, calling for classification studies.
Water type classification and Piper diagram
Groundwater samples from the 17 project wells have been classified according to Lloyd et al. [7] on the basis of Na+/Cl- and (Ca2+ + Mg2+ - SO42+ - HCO3-) / Cl- ratios. Based on these ratios it has been found that 72% of the wells are tapping groundwater that is either fresh or freshening type and 28% of the wells are tapping saline water with no effect of induced recharge. The water analysis data pertaining to the project wells are plotted in Piper diagram.
Isotopic approach
Under this approach, the isotopic data particularly on environmental tritium and stable isotopes 18O and D have been used to assess the influence of modern recharge as well as to distinguish between the rainfall and river recharge to groundwater being tapped by project wells. The isotopic signatures of groundwater falling in different types are not similar, but show variations. Using the stable isotopic signatures, the recharge sources to groundwater can be characterized in conjunction with tritium data.
The data on environmental tritium analysis was carried out for 8 localities. In the fresh water class, tritium values range between 1.3 and 3.3 TU indicating relatively traceable to moderate modern recharge. In freshening class, tritium values range from 1.0 to 2.1 TU indicating traceable modern recharge. And in saline class the values are less than 1.0 TU. Thereafter, Data on 18O and D of groundwater from the 16 out of 17 project wells were analysed. 18O value of Chandrabhaga river ranges from –3.5% to –3.3% at higher altitudes and is about -1.6% at lower altitude. The value –1.6% may be considered as isotopic index of local precipitation at the mean elevation of the study area (250 m above m.s.l.). 18O values less than – 1.6% with TU values less than 1 are then a result of rainfall infiltrated at higher altitudes, while 18O value less than –1.6% with TU value less than 1 may be due to contribution of river water. 18O value of the river Purna ranges from –2.1% to –2.5% and that of saline groundwater is also about –2.5%, which indicate effluent nature of river. The 18O value of Sahanoor river is about –2.0% as observed at a site located at higher altitude (400 m above m.s.l.).
Integrated evaluation employing stable isotopic signatures in conjunction with environmental Tritium and hydrochemical data has been attempted for all the samples (Bhattacharya et al.,[2]) e.g. induced recharge effect is visible when relatively depleted 18O occurs with low TDS, low Sr, and plots about IMWL (Indian Meteoric Water Line) whereas no effect of induced recharge is visible when relatively enriched 18O enriched value occurs with tritium < 1 TU, moderate to high TDS, and plots on El (Evaporation line). Marginal effect of induced recharge is visible when relatively enriched value of 18O occurs with lower to moderate TDS and Sr, lower tritium value, and plot in the area intermediate of EL and IMWL. In this fashion, the interpretations have been arrived at and have been presented in Table 2.
Table 2. Summary of performance of project wells located in Amravati district evaluated
by integrated approach
Sl. No. / Sample No. / Project Well Location / Hydro-chemical approach / Isotopic approach / Whether rechargedChandrabhaga basin
1. / 32 / Sangwa / Successful / Successful / Yes*
2. / 33 / Shiwarkhed / Successful / Successful / Yes*
3. / 31 / Nardoda / Successful / Successful / Yes*
4. / 22 / Shiwar bk / Successful / Successful / Yes**
5. / 23 / Tonglabad / Successful / Successful / Yes*
6. / 14 / Nachona / Successful / Not successful / No***
PurnaBasin
7. / 7 / Shignapur-17 / Not successful / Not successful / No***
8. / 9 / Shignapur-13 / Not successful / Not successful / No***
9. / 25 / Chandola / Not successful / Not successful / No***
10. / 26 / Karatkheda / Marginally successful / Marginally successful / Further study required*
11. / 24 / Ramtirth / Successful / Successful (Local rainfall) / Yes**
PedhiBasin
12. / 29 / Gaurkheda / Successful / Successful / Yes*
SahanoorBasin
13. / 27 / Telkheda / Successful / Successful / Yes*
14. / 28 / Katkheda / Successful / Successful / Yes*
15. / 6 / Rajkheda / Successful / Successful / Yes*
16. / 5 / Yerangaon / Successful / Successful / Yes*
17. / 4 / Pimplod / Successful / Successful / Yes*
* river contribution more than local rainfall **Local rainfall contribution more than river
***No effect of induced recharge
Figure 1. Index map of study area
Figure 2. Favorable section across Purna river
CONCLUSIONS
It has been observed that the wells located along Purna river are not showing effect of the river recharge. However, the wells located in the Chandrabhaga river and Pedhi river sub-basins are showing better results. Further, the wells tapping the first semi – confined aquifer (18-25 bgl) show better results than the ones that tap deep-seated aquifers.
REFERENCES
[1]Adyalkar, P.G., “Palaeogeography, nature and pattern of sedimentation and groundwater potentiality of the Purna basin of Maharashtra”, Proc. Nat. Inst. Sci. Ind., India, Vol. 29A, No. 1 (1963), pp 25-45.
[2]Bhattacharya, S.K., Gupta S.K. and Krishnamurthy R.V., “Oxygen and hydrogen isotopic ratios in groundwater and rivers from India”. Proc. Indian Acad. of Sciences, India, Vol. 94 (1985), pp 283-295.
[3]Dev Burman, G.K. and Mehta, M., “Aquifer Geometry and possibilities of improving ground water quality in Purna saline tract, Maharashtra”, Proc. Integrated Approach to Management Water and Soil of Purna river basin with special reference to salinity characteristics, India (1996).
[4]GSDA, “Report on desalinasation project”, Groundwater Surveys and Development Agency, Pune, India (1996).
[5]GSDA, “Report on desalinasation project”, Groundwater Surveys and Development Agency, Pune.
[6]Kailasam, L.N., “A geophysical study of conditions of groundwater salinity in the Purna valley, Berar”, Geol. Surv. Ind. report, India (1949).
[7]Lloyd, J.W. , “Saline groundwaters associated with fresh groundwater reserves in the United Kingdom. A survey of British hydrogeology”, Specl. Pub., R. Soc., London (1981), pp.73-84.
[8]Mathew, P.M., “Report on the geophysical investigations in exploratory tubewells areas in Purna valley, M.P.”, Geol. Surv. Ind. report, India (1955).
[9]Muthuraman, K., Tiwari, M.P. and Mukhopadhyay, P.K., “Salinity in groundwater of Purna basin – its genesis”, Jour. Geol. Soc. India, Vol. 39,(1992), pp. 50-60.
[10]Ravishankar, “Neotectonic activity along the Tapti Satpura lineament in Central India”. Indian Minerals, Vol. 41, No. 1, (1987), pp. 19-30.
[11]Roy, A.K., “Note on the selection of exploratory well sites in the Purna and Narmada basins, Madhya Pradesh (T.C.A. Operationa Agreement No. 12)”, Geol Surv. Ind. Memorandum No. 8, (1953)
[12]Tiwari, M.P., Bhai, H.Y., Padhi, R.N. Bandopadhyay, K.P. , “Geomorphology and geology of the Purna valley”. Proc. Integrated Approach to Management of Water and Soil of PurnaRiver Basin with Special Reference to Salinity Characteristics, , Nagpur, India, (1996), pp. 11-20.
[13]Todd, D.K., “Groundwater hydrology”. John Wiley and Sons, New York, (1980).