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E. Shaji ¹, N. Vinayachandran ², D. S. Thambi ²

Affiliations
1 Department of Geology, University of Kerala, Kariavattom, Trivandrum - 695 581, IN
2 Central Ground Water Board, Kerala Region, Trivandrum - 695 004, IN

Abstract

Hydrogeochemical characteristics of groundwater in phreatic aquifers of Alleppey district were studied. Factor analysis has been applied to the chemical analysis data of 32 water samples collected from dug wells to extract the principal factors corresponding to the sources of variation in the hydrochemistry. 12 hydrochemical parameters were correlated and statistically examined. Varimax rotation was used to define the factor scores and percentage of variance in the hydrogeochemistry. A four-factor model is extracted and explains over 80.394% of the total groundwater quality variation. Factor-1 has high loading values of Electrical Conductivity (EC), Ca⁺⁺, and Cl^-, and reflects the signature of saline water. Similarly strong correlation exists between F3 score and pH. The correlation coefficient matrix between EC and Na⁺, Cl^-, SO^--₄ is significant. The mineralogy of coastal aquifers and the marine aerosol are playing significant role in the hydrogeochemistry of groundwater in the phreatic aquifer system.

Keywords

Factor Analysis, Groundwater, Coastal Aquifer, Marine Aerosol, Kerala.

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E. Shaji ¹

Affiliations
1 Department of Geology, University of Kerala, Kariavattom, Trivandrum-695 581, Kerala, IN

Abstract

An opportunity to study the effects of artificial structures like tidal regulators on the near-shore environment is provided by the manually operated tidal regulator constructed across a man-made canal in an estuarine environment in the tropical climatic setting of the southern coastal State of Kerala in India. The regulator was constructed across a man-made canal at Pozhikkara in 1957 to control the salt water intrusion into Paravoor Kayal (Kayal = back water or estuary) and to protect a natural estuary. This protection was originally being afforded by a feature locally known as 'Pozhi', which is in fact a natural sand bar occurring along the coast separating backwaters from the sea during the summer, but allowing the sea and the backwater to merge by its erosion during the monsoon. This natural sandbar, thus, protected the Paravoor estuary from sea water ingress from the Lakshadweep sea (of the Indian Ocean) during the summer season. When a situation, where the natural sandbar could not protect the estuary and the inland paddy crops from saline water ingress arose, the concept of an artificial tidal regulator was evolved by the farmers of the Ithikara Ela (Ela = paddy field). An artificial canal was constructed 500 m south of the sandbar by cutting the main land, thus, connecting the lake and the sea. Thereby, around 1 sq. km of land was separated from the main land to become an island with 87 houses and 300 inhabitants. During 1985 the performance of the regulator started deteriorating, finally leading to its collapse in 1990. The water levels in the wells, the EC, pH, TH, Ca, Mg, Na, K, CO₃, HCO₃, SO₄ and Cl were determined in this study. The hydrological impacts of this regulator were (i) the hydraulic continuity of the aquifer has been disturbed, (ii) the dug wells, which used to yield fresh water on the separated land mass, became dry within five years of commissioning of the regulator, as the canal became effluent in nature, (iii) the dug wells were consequently deepened and salt water intrusion began and at present more than 25 wells are saline due to salt water intrusion into the freshwater aquifer of the 1 sq km area, (iv) the Paravoor estuary is becoming more saline day-by-day due to the free flow of saline water through the canal, and (v) the Paravoor estuary is getting filled up with ocean sediments during high tides and sand terraces are being formed within the lake. All these are direct outcome of the badly maintained tidal regulator. As a remedial step the spillway shutters should be refitted immediately. This will help protect the deteriorating environment and ecosystem of Paravoor estuary and the adjoining land. Rainwater harvesting is recommended for the polluted wells. The artificial tidal regulator project was implemented without a proper environmental impact assessment. Detailed environmental impact assessment is essential before implementing such schemes in coastal areas at the interface of varied environments, especially like an estuarine one in the tropics.

Keywords

Saline Intrusion, Tidal Regulator, Sand Bar, Backwaters, Tidal Barrages, Paravoor Estuary.

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Prathibha Raveendran ¹, E. Shaji ¹

Affiliations
1 Department of Geology, University of Kerala, Kariavattom Campus, Trivandrum-695581, IN

Abstract

Groundwater in the hard rock aquifers of Trivandrum district has been studied to characterize the groundwater potential and prospects. The study area is occupied by four watersheds (Ayirur, Vamanapuram, Karamana and Neyyar) and groundwater is one of the main sources of water for drinking and agricultural purpose. The groundwater scenario has been assessed by using the water table contour maps and groundwater level fluctuation maps based on the data obtained from 93 observation wells. The average water level in the region is 9 to 13 and 8 to 10 mbgl during pre and post monsoon seasons respectively. The deepest water level (20.21 mbgl to 26.67 mbgl) is recorded from places such as Chovvarapotta, Pazhayaucchakkada and Ozhukupara and shallowest water level (0.85 mbgl to 1.61 mbgl) is in places like Irumba, Punnamkarikkakam, Kathipara and Erattachira. Most of the deep dug wells go dry during summer months, though these wells show good water level fluctuation during rainy season. A detailed investigation has revealed that substantial quantity of groundwater is being lost as base flow. This base flow of groundwater makes the rivers and river lets, perennial in the area. The long term trend analysis shows that (ten years data), majority of the wells are showing declining trend (1.99 m/year) and this decline is attributed to the change in land use pattern in the area and less recharge from the rainfall. The rainfall analysis shows that there is not much variation in the rainfall pattern over the last few years. On the basis of mathematical projection the water level trends for the next ten years has been predicted. The analysis shows that the groundwater potential in the hard rock aquifer is depleting hence an immediate recharge measures have to be implemented in this region to arrest the decline trend and the base flow.

Keywords

Hard Rock Aquifer, Kerala, Groundwater Resources, Hydrochemistry, Long Term Trend.

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T. R. Deepu ¹, E. Shaji ¹

Affiliations
1 Department of Geology, University of Kerala, Kariavattom Campus, Thiruvananthapuram-695 581, Kerala, IN

Abstract

The geochemical characteristics of groundwater in the Chittur block, Palghat, Kerala have been studied to assess the water quality for domestic and irrigational purposes. During pre-monsoon (April- 2010) period 89 groundwater samples were collected from 61 dug wells and 28 bore wells. Chemical analysis of the groundwater shows different ranges for different parameters (pH 6.25-8.29, EC 250- 2400 μS/cm, TDS 160-1536 mg/L, TH 65-945 mg/L, Mg²⁺ 3.62-189.46 mg/L, F^- 0.02-6.3 mg/L, Cl^- 10-672 mg/L, Na⁺ 1-126 mg/L, K⁺ 1-23 mg/L, NO₃ ^- 1.42-23.15 mg/L, SO₄ ^2- 5.72-159.62 mg/L and PO₄ ^3- 0-2.12 mg/L). High fluoride (F^-) concentration is reported from 12% water samples. Piper diagram reveals that 42% of the samples are MgCO₃ type. Irrigational suitability of water is evaluated based on sodium adsorption ratio, residual sodium carbonate, sodium percent, salinity hazard and USSL diagram. Salinity hazards show that 52% of the samples fall in high salinity hazard (C3) and 1% in very high salinity hazard class (C4). The study shows that, groundwater beyond the acceptable limit of EC, TDS, TH, Mg²⁺ and F^- are not suitable for drinking, and groundwater fall in very high salinity hazard class is not suitable for irrigation.

Keywords

Groundwater Quality, Fluoride, % Sodium, Sodium Adsorption Ratio, Residual Sodium Carbonate, Chittur.

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E. Shaji ¹

Affiliations
1 Department of Geology, University of Kerala, Kariavattom campus, Trivandrum - 695 581, IN

Abstract

The first International Conference on Engineering Geophysics was held at UAE University, Al AIN, United Arab Emirates during December 11 to 14, 2011. Over 170 delegates from 24 countries attended the conference organized by the United Arab Emirates University and Al Ain City Municipality in association with European Association of Geoscientist and Engineers (EAGE). Minister of Higher Education and Scientific Research and Chancellor of the UAE University HH Sheikh Nahyan Bin Mubarak Al Nahyan inaugurated the Conference.

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E. Shaji ¹, K. V. Sarath ¹, Pranav Prakash ¹, Adithya Pazhoor Abraham ², V. Deepchand ¹, V. Kunhambu ³, A. P. Pradeepkumar ¹

Affiliations
1 Department of Geology, University of Kerala, Thiruvanathapuram 695 581, IN
2 Department of Civil Engineering, National Institute of Technology, Calicut 673 601, IN
3 Central Ground Water Board, Kerala Region, Thiruvanathapuram 695 004, IN

Abstract

Tunnel wells or surangams are less common traditional groundwater harvesting structures of Kasara-god district in Kerala, southern India. These horizontal wells, structurally resembling Qanats, are driven into the laterite plateaus and hills for tens of metres. The status of tunnel wells of Kasaragod is synthesized, the problems and prospects examined to evolve a common strategy for sustainability. Functionally four different types of tunnel wells exist: (1) single tunnel, (2) single tunnel with branches, (3) tunnel system ending in a vertical well, and (4) tunnel system ending in a well with a horizontal outlet. The yield of tunnel wells has reduced over the years and 50% of them are now dry. Single tunnels (types 1 and 2) act as conduits for excessive draining of groundwater from the aquifer system during the rainy season, leading to wastage of groundwater and lowering the water table. The discharge estimates from the 24 tunnel wells indicate that 6653 m³ of groundwater gets discharged from the aquifer per day.To prevent wastage, the mouth of the tunnel wells should be fitted with half shutter gate with a control valve at the bottom. There is an urgent need to create awareness to protect and modify these traditional water harvesting structures for sustainability of water resources.

Keywords

Discharge, Groundwater, Kasaragod, Traditional Water Harvesting, Tunnel Wells, Surangam.

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