Environ. Process. https://doi.org/10.1007/s40710-018-0297-4 O R I G I N A L A RT I C L E
Hydrogeochemical Evaluation of Groundwater Quality for Drinking and Irrigation Purposes and Integrated Interpretation with Water Quality Index Studies Narsimha Adimalla 1,2 & Peiyue Li 1,2 & Sudarshan Venkatayogi 3
Received: 7 January 2018 / Accepted: 9 April 2018 # Springer International Publishing AG, part of Springer Nature 2018
Abstract Groundwater is the major source for drinking and irrigation purposes in the Central parts of Telangana. The demand for groundwater has recently increased due to intensive irrigation practices and population growth which in turn caused depletion of resource and deterioration of quality. In view of this, quality studies have been undertaken on 105 groundwater samples collected from the rock dominant semi-arid region of central Telangana and analysed for pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), chloride (Cl−), sulphate (SO42−), nitrate (NO3−), and fluoride (F−). Results revealed that 51% and 71% of groundwater has more than the maximum acceptable limits of fluoride (1.5 mg/L) and nitrate concentrations (45 mg/L), respectively, thus making the groundwater unsuitable for drinking purpose. Data plotted in Gibbs diagram reveal that the groundwater chemistry is primarily controlled by rock-water interaction. According to water quality index (WQI), 60% and 36% of groundwater samples fall in excellent and good categories for drinking purpose. A majority of groundwater samples fall in deep meteoric percolation and Na+-SO42− types, but most belong to Ca2+–Mg2+–HCO3−, Na+–HCO3− facies, and few are of Ca2+–Mg2+–Cl− and Na+– Cl− facies. 90% of groundwater in the study region is well suitable for irrigation. It is advised that groundwater with high fluoride and nitrate concentration should be avoided for drinking purposes.
* Narsimha Adimalla
[email protected]
1
School of Environmental Science and Engineering, Chang’an University, No. 126 Yanta Road, Xi’an 710054, China
2
Key Laboratory of Subsurface Hydrology and Ecological Effects in Arid Region of the Ministry of Education, Chang’an University, No. 126 Yanta Road, Xi’an 710054 Shaanxi, China
3
Department of Applied Geochemistry, Osmania University, Hyderabad 500 007, India
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Keywords Groundwater quality . Drinking and irrigation . Water quality index (WQI) . Rock dominant semi-arid region . Telangana
1 Introduction Groundwater plays a prominent role in water supply system for drinking, irrigation and industrial purposes in arid and semi-arid regions of the world. Recent studies reveal that nearly 65% of groundwater in the world is used for drinking purposes, about 20% for irrigation and 15% is used for industrial purposes (Adimalla and Venkatayogi 2018; Adimalla et al. 2018a; Saeid et al. 2018). UNEP (1999) reported that 1/3 of the world population uses groundwater for drinking purpose, especially developing countries like India and China. Groundwater plays vital role in fulfilling the basic needs of the society and over-exploitation has tremendous stress on this important resource due to increasing demand. It is essential to monitor the groundwater quality and quantity, and hence, the groundwater studies have become vital in semi-arid regions to meet the increasing demand and assess the groundwater quality. Groundwater measures in arid and semi-arid regions are controlled by local hydrogeology, topography, geological structures, evaporation, precipitation, rock-water interactions, weathering, industrial effluents, irrigation/cultivation, chemical fertilizers and largely anthropogenic activities (Adimalla and Venkatayogi 2017, 2018). Studies have been carried out over the world to demonstrate the groundwater measures/groundwater quality and its suitability for drinkingand irrigation, and major contaminant sources (Adimalla et al. 2018a; Dişli 2017; Li et al. 2016b; Alaya et al. 2014; Narsimha et al. 2013). Faten et al. (2016) have observed that the rock-water interaction and evaporation are the main factors, which control the groundwater chemistry in Northeastern Tunisia. Li et al. (2016a) conducted a study in the semi-arid region of Northwest China and found that the hydrochemistry of groundwater is mainly governed by rock-water interaction. Adimalla and Venkatayogi (2017) performed a groundwater quality study in the region of Medak, Telangana, and identified that rock-water interactions and geogenic sources are the main controlling factors of hydrogeochemistry. Over exploitation of groundwater has become one of the serious problems in many countries, including India. The annual extraction of groundwater in India is the highest in the world, which even supersedes that of the USA and China put together (NGWA 2016). CGWB (2013) estimated that approximately 245 × 109 m3 of groundwater is being used for irrigation and also nearly 90% of rural population of the country uses groundwater for drinking and domestic purposes. Moreover, groundwater pollution is a serious problem in India. Increasing water withdrawals and consumption, intensive urbanization, industrial growth, over usage of fertilizers and pesticides in agricultural regions, human and animal wastage and unplanned drainage systems are some of the important causes for the deterioration of the quality of groundwater. Therefore, in recent years a number of researchers have focussed on groundwater quality studies for various usages in India (Adimalla and Venkatayogi 2018; Adimalla et al. 2018a; Narsimha and Rajitha 2018; Narsimha 2018; Narsimha and Sudarshan 2013, 2017a, 2017b, 2018a, 2018b; Chetan et al. 2017; Subba Rao et al. 2012; Sudhakar and Narsimha 2013). In the current study region, residents merely rely on groundwater, since it is the main source for drinking and irrigation purposes. In Medak region of Telangana, much concern is caused by the continuous drop of water table from 18.39 m bgl to 24.34 m bgl in the last six months. Chinnakodur is one of the regions facing groundwater decline, pollution and deterioration of water quality. Therefore, the current study primarily deals with groundwater suitability for
Hydrogeochemical Evaluation of Groundwater Quality for Drinking and...
drinking purpose through the computation of a Water Quality Index (WQI). Water quality parameters are also compared with BIS (2012). In addition, the USSL (Richards 1954), Wilcox (1955), sodium adsorption ratio (SAR; Richards 1954), sodium percentage (%Na+; Wilcox 1955), residual sodium carbonate (RSC; Eaton 1950), magnesium hazard ratio (MHR; Raghunath 1987), and Kelly index (KI; Kelly 1963) were also used to determine the suitability of water quality for irrigation in the Chinnakodur region.
2 Study Area The present study area is situated in the central part of Telangana, located between 18°12′ and 18° 26’ North latitudes and 78°00′ and 79°98′ East longitudes (Fig. 1). The area has a continental arid to semi-arid climate with an annual average temperature of 26.3 °C, with May being the hottest month of the year. The average annual rainfall is 861 mm and July is the wettest month of the year. The study region is hard rock terrain occupied with Archaen granites, gneisses, amphibolite, hornblende biotite schist, and basic rocks. In the study area, groundwater naturally occurs under phreatic conditions in the weathered layer and semiconfined conditions in the fractured zones at different levels (CGWB 2013).
3 Sampling and Analytical Procedures 105 groundwater samples were collected and analyzed for various hydrochemical parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH) as CaCO3, calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), chloride (Cl−),
Fig. 1 Location map of groundwater samples in the Central Telangana
Adimalla N. et al.
sulphate (SO42−), nitrate (NO3−), fluoride (F−). EC and pH of water samples were measured in the field immediately after the collection of the samples using a pH/EC/TDS meter (Hanna HI 9811–5). The detailed analytical procedure is given in Table 1. Groundwater quality parameters such as sodium adsorption ratio (Richards 1954), residual sodium carbonate (Eaton 1950), sodium percentage (Wilcox 1955), Kelly’s ratio (Kelly 1963), and magnesium hazard ratio (Raghunath 1987) were evaluated for irrigation suitability. They were computed using the following equations: Naþ SAR ¼ qffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi 2þ Ca þ Mg2þ =2 %Na ¼
ð1Þ
Naþ 100 Ca2þ þ Mg 2þ þ Naþ
ð2Þ
Table 1 Instrumental, titrimetric and calculation methods used for chemical analysis of groundwater samples from Chinnakodur region, Telangana, South India Parameters Characteristics Analytical method
Reagents
Unit
General
pH 4, 7 and 9.2
–
pH
pH/EC/TDS meter
pH/EC/TDS meter Electrical Conductivity (EC) Total dissolved Calculation solids (TDS) Total hardness EDTA titrimetric (as CaCO3) Major cations
Major anions
Potassium chloride
APHA (1999) μS/cm APHA (1999)
EC X (0.55 to 0.75)
mg/L
Hem (1991)
mg/L
APHA (1999)
mg/L
APHA (1999) APHA (1999)
Sodium (as Na+) Potassium (as K+) Bicarbonates (HCO3−)
Flame photometric
EDTA, ammonia buffer and Eriochrome Black-T (EBT) indicator EDTA, sodium hydroxide and murexide MgH = TH-CaH; Mg = MgH X Eq.Wt of Mg X Normality of EDTA Sodium chloride (NaCl) and KCl
Flame photometric
NaCl and KCl
mg/L
Titrimetric
mg/L
Chloride (Cl−)
Titrimetric
Hydrosulfuric acid (H2SO4), phenolphthalein and methyl orange Silver nitrate (AgNO3), potassium chromate HCl, ethyl alcohol, NaCl, barium chloride, sodium sulphate Potassium nitrate (KNO3), Phenol disulponic acid, ammonia TISAB III and NaF
Calcium (as EDTA titrimetric Ca2+) Magnesium (as Calculation Mg2+)
Sulphates UV visible (SO42−) spectrophotometer Nitrate (NO3−) UV visible spectrophotometer Fluoride (F−) ISE (Ion selective electrode; Thermo Orion)
Reference
mg/L
mg/L
mg/L mg/L mg/L mg/L
APHA (1999) APHA (1999) APHA (1999) APHA (1999) APHA (1999) APHA (1999) APHA (1999)
Hydrogeochemical Evaluation of Groundwater Quality for Drinking and...
2þ RSC ¼ HCO−3 þ CO2− þ Mg2þ 3 − Ca
MHR ¼
Mg 2þ 100 Ca2þ þ Mg2þ
KI ¼
Naþ Ca2þ þ Mg2þ
ð3Þ
ð4Þ
ð5Þ
where all ion concentrations are expressed in meq/L. In addition, a water quality index (WQI) was computed to evaluate the groundwater suitability for drinking purposes (Horton 1965; Ramakrishnalah et al. 2009). The WQI used was developed by Horton (1965). It is a mathematical effectual tool, which provides a comprehensive model of the groundwater quality and is used to present large quantities of water quality data into a single number (Ramakrishnalah et al. 2009; Varol and Davraz 2015). WQIs are used by scientists to assess the water quality for drinking purposes in various geological terrains (Aly et al. 2015; Adimalla and Venkatayogi 2018; Ramakrishnalah et al. 2009). WQIs are effective tool to estimate the overall groundwater quality for drinking purposes by examining individual water quality parameters (e.g., pH, TDS, TH, Ca2+, Na+, K+, Mg2+, SO42−, Cl−, NO3− and F−). The following three stages are involved in WQI calculation: (a) assignment of weights (wi) to each water quality parameter involved; (b) calculation of relative weights (Wi) (based on Eq. 6); and (c) quality rating scale calculation (Qi) (based on Eq. 7): wi ∑ni¼1 wi
ð6Þ
Ci 100 Si
ð7Þ
Wi ¼
Qi ¼
where Qi is the quality rating for each chemical parameter i, Ci is the concentration of each chemical parameter i in each water sample (mg/L), n is the total number of parameters, and Si is the Indian drinking water standard (BIS 2012) for chemical parameter i. Assigning the weights for each chemical parameter is the most important part, which determines the significance of a water quality parameter for drinking uses. For each of 11 parameters, a weight (wi) has been assigned according to its relative importance in the overall quality of drinking water, as shown in Table 2. The most significant parameters have a weight of 5 and the least significant have a weight of 2. In the study, the maximum weight of 5 has been assigned to total dissolved solids, nitrate and fluoride, due to their major importance in water quality assessment (Ramakrishnalah et al. 2009). Then, water quality sub-indices (SIi) for each chemical parameter are computed by Eq. (8), and the WQI is determined by Eq. (9): SIi ¼ Wi Qi
ð8Þ
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WQI ¼ ∑ni¼1 SIi
ð9Þ
where SIi indicates the sub-index of the ith parameter.
4 Results and Discussion 4.1 Assessment of Groundwater Suitability for Drinking Purposes It is essential to distinguish the quality of groundwater for drinking purposes and other usages. Groundwater quality parameters and analytical results are presented in Table 3 and the values are compared with standard values of the Bureau of India Standards (BIS 2012), as shown in Table 4. The pH value ranged from 6.5 to 9.1, with a mean of 8.1 (Table 3). Nearly 90% of groundwater samples were alkaline in nature (Table 3). However, 9% of groundwater samples exceeded the recommended limits (BIS 2012; Table 4; Fig. 2a). The total dissolved solids (TDS) concentration in the groundwater varied from 224 to 1529 mg/L, with mean 741 mg/L (Table 3), and 18% of groundwater samples were within the acceptable limit (500 mg/L). 82% of the samples fell under the permissible limit (
