Indian Journal of Geo Marine Sciences Vol. 46 (09), September 2017, pp. 1765-1779 Hydrogeochemistry of groundwater along a tsunami devastated coastal segment of Kerala: Arattupuzha Village, Alappuzha, India V. Sivanandan Achari*, T. Regi George, P. Deepa , M.S. Ambili, S. Jayasree, A.S. Rajalakshmi & Raichel Mary Lopez School of Environmental Studies, Cochin University of Science and Technology, Cochin -682022, Kerala, India *[Email: [email protected]] Received 04 July 2017 ; revised 20 July 2017 Water quality parameters exceed the permissible standard limit set by IS 2012, WHO 2011 and USEPA 2014 in many instances of sources studied. GIS study shows the spatial variation of parameters. Pearson's Correlation matrix study suggest that electrical conductivity of water is correlated with TH, Ca, Na, K and Cl. There are noticeable decline in quality with regards to WQI. Sodium – Chloride ratio shows that reverse ion exchange occur in the region. Hill-Piper Trilinear plots reveal mixed nature of different hydrochemical facies, mainly (i) Ca–Mg–HCO3 (Temporary Hardness), (ii) Ca-Mg-Cl-SO4 (Permanent Hardness) and (iii) Na– K–Cl (Saline) in shallow dug wells. Deep bore wells, the water is Ca–Mg–HCO3 type. Some of the sources are having saline water, corrosive and scale forming. [Keywords: Tsunami, Groundwater Quality, Pearson Correlation, Water Quality Index(WQI), Sodium-Chloride ratio, Saturation Indices, Hydrogeochemical facies] Introduction determined by ground water department for the 12 Study of ground water rest on an period since 1987 shows declining trend . This understanding of the subsurface water chemistry indicates that extensive groundwater extraction is and fresh water availability in a region is taking place over the years and the recharge important as a post disaster impact study1. In during monsoon season is not enough to India groundwater is an important water resource compensate. Coastal erosion is one of the grave for domestic and agriculture uses in both rural natural hazards affecting the Alappuzha district and urban areas2, 3. The need to assess the ground and extensive coastal erosion is taking place in water quality is becoming increasingly important the present study area. This area is devastated by th 13,14 in a local perspective4. Primary standards and 26 December 2004 Indian Ocean Tsunami treatment techniques protect public health by and has many significant features resulted by rich limiting the levels of contaminants in drinking mineral sand deposits. water and is possible through unfailing research Materials and Methods initiatives region wise. Several publications are available reporting the ground water quality in Study Area India5-10 and water conservation initiatives are The present study area (coastal region of planned based on the data available. India has Arattupuzha village, Alappuzha, Kerala, India) lies about 7517km long coastline and a complete between 9°7'41" & 9°11'26"N latitudes and groundwater quality profile of these regions 76°26'25" & 76°28'23"E longitudes. This region has comprising physico-chemical and biological been severely affected by 26th December 2004 parameters over a period of 12 months is rare. Indian Ocean Tsunami. Evaluation of groundwater Present study is focused on a coastal segment of quality with respect to pre and post tsunami Kerala-Arattupuzha in Alappuzha district11. This situation is elaborately done in this study (Figure 1). district has a flat unbroken coastline of 82km The sand and silt is the lithological feature length which constitutes 13.9 percent of the total of the study area. A major part of the district coast of the State of Kerala. Water level data forms part of the coastal plains. General elevation 1766 INDIAN J. MAR. SCI., VOL. 46, NO. 09, SEPTEMBER 2017 of the area is less than 6 m above mean sea level. straight. Absence of extensive tidal plain and the Soils have low content of organic matter and of intensive coastal erosion may be indicative of low fertility level. Geomorphology of the area neo-tectonic activity. Land use of the area includes beach, mudflat, coastal plains and water includes agricultural field, mixed vegetation, built body (Figure 2a). Beach ridges are suggestive of up and water body (Figure 2b). marine regression. Beach is very narrow and Fig. 1 - Location map of the study area, Arattupuzha coast, Alappuzha, Kerala, India (a) (a) Fig. 2 - a) Geomorphology and b) Land use pattern of the study area, Arattupuzha coast, Alappuzha, Kerala, India. ACHARI et al.: GROUNDWATER ALONG A TSUNAMI DEVASTATED COASTAL SEGMENT OF KERALA 1767 Groundwater samples are collected every Results and Discussion month from 6 shallow open dug wells and 7 deep Analytical results for the general parameters bore wells from January 2012 to December 2012 such as Temperature, pH, Electrical Conductivity (Figure 1). During sample collection (handling (EC), Redox Potential (Eh), Dissolved Oxygen and preservation) and analysis standard procedures (DO), Biochemical Oxygen Demand (BOD), Total recommended by the American Public Health Alkalinity (TA), Total Hardness (TH), Total 15 Association (APHA) are followed. The suitability Dissolved Solids (TDS); cations such as Calcium of groundwater for domestic purposes are evaluated (Ca), Magnesium (Mg), Sodium (Na+), Potassium by comparing the water quality parameters with (K+), Iron (Fe) and anions such as Bicarbonate those of the Indian standards IS 2012, World - - 2- (HCO3 ), Chloride (Cl ), Sulphate (SO4 ), Phosphate Health Organisation (WHO 2011)16 and US 3- - (PO4 ), Nitrate (NO3 ) for shallow Dug Wells (DW) Environmental Protection Agency (USEPA 2014) and deep Bore Wells (BW) are compared with the guideline values for drinking water. Spatial standards (WHO 2011& USEPA 2014) in Table:1. analysis of various physico-chemical parameters In the case of shallow dug wells mean of 6 stations was carried out using the ArcGIS 10 software. In and in the case of bore wells mean of 7 stations in order to interpolate the data spatially and to each month of year 2012 are averaged to determine estimate values between measurements, an the annual mean and standard deviation. From the inverse distance weighed (IDW) algorithm was analysis of Total Carbon (TC), Total Inorganic 17-19 used. Pearson Correlation study is done to Carbon (TIC) and Total Organic Carbon (TOC), it understand the relationship between different is clear that major components present in both DW 20-22 parameters. Water Quality Index (WQI) of the and BW strata are inorganic. different water sources were evaluated by pH shows slight alkaline in nature mostly for weighted arithmetic index method using the the sources. The 2012 annual mean pH of DW parameters pH, EC, Total Dissolved Solids strata in the study area is 7.8±0.4 and that of BW (TDS), Total Hardness (TH), Ca2+, Mg2+, Na+, K+, strata is 7.5±0.24. There is not much variation in pH HCO -,Cl- & SO 2-. To study the possibility of 3 4 and throughout the year it is within standard range major processes such as ion exchange or reverse of 6.5-8.5. Since pH is below 8.5, the alkalinity is ion exchange ratios Na/(Na+Cl ) and Na/Cl are mainly due to the presence of bicarbonate. EC of determined . If Na/Na+Cl ˃ 0.5 and if Na/Cl ˃ groundwater with respect to DW strata during year 1.0, ion exchange is observed. To assess the 2012 is 1.2±1.4 mS/cm with confidence interval irrigation quality23-25 of the water samples collected (CI) of 0.3-2.1 mS/cm at 95% significant level. 6 parameters are calculated using the concentrations After September 2012 there is a hike in the EC, of various ions obtained from chemical analysis which is an indication of sea water intrusion in dug after converting to milliequivalents per litre wells near to the sea. As regards to EC determined, (meq/L). They are Sodium Adsorption Ratio the water of those wells become unsuitable for (SAR), Sodium Percentage (Na%), Magnesium domestic uses because the EC exceed the standard Adsorption Ratio (MAR), Residual Sodium limit of 1.5 mS/cm. The degree of sea water Carbonate (RSC), Permeability Index (PI) and contamination, defined by sea water- fresh water Kelly’s ratio (KR). USSL and WILCOX diagrams interface, depends on the height of the fresh water are graphical plots to classify water samples based column over the mean sea level. So the DW stations on irrigation suitability. Analytical values obtained show variation in EC over the year. Annual mean for the groundwater samples are plotted on of EC of BW strata during year 2012 is Hill-Piper Trilinear diagram to understand the 0.33±0.04mS/cm. From the spatial distribution map hydrochemical regime of the study area. These of EC for the month of December 2012 (Figure: 3a), diagrams clearly explain the variations of cation very high profile for DW strata can be clearly seen. and anion concentration in the study area. The diamond-shaped field of piper diagram is divided The redox potential (Eh) is a numerical index of the intensity of oxidizing or reducing into four classes. The study presented in this paper 26 comprises hydrogeochemistry of the region based conditions within a system . In the present study, on groundwater quality of 6 dugwells and 7 bore redox potential is negative throughout the year wells sampled and analysed from January to this indicates reducing environment. Oxygen is December 2012. supplied to ground water through recharge and by 176 8 INDIAN J. MAR. SCI., VOL. 46, NO. 09, SEPTEMBER 2017 movement of air through unsaturated material hardness or carbonate hardness, CH); in many above the water table. This oxygen reacts with stations, permanent hardness (non carbonate NCH) oxidizable material encountered along the flow path is observed [ie; TH = CH + NCH]. TDS of DW of the water. Photosynthesizing biota enhances the strata exceed the permissible limit in many DO, whereas organic matter decomposition occasions.