14.1.2.2 Groundwater Level and Tidal
Level Measurements
The groundwater levels in the sampling wells
were recorded using a water level recorder. Tidal
water levels were measured at estuary mouth of
nearby beaches and inland dug wells. The
influence of tide on the estuarine water level was
measured using a Schlumberger data logger.
Monitoring wells consisting of 3.2 cm diameter
PVC pipe with a 7.6 cm screen at the bottom
were installed in shore and river banks for tidal
level and temperature measurement (Urish and
McKenna 2004). The pressure transducers
include atmospheric pressure compensation and
were connected to a data logger for continuous
data recording on hourly basis. The location of
the sampling stations, elevation and distance
from the coast was measured using Garmin Etrex 12-channel global positioning system (GPS).
14.1.3 Results and Discussion
14.1.3.1 Groundwater Chemistry
The quality of groundwater has equal importance
as the quantity and this has been recognized only
a couple of decades ago. The characteristic of
groundwater (hard or soft; mineralized or nonmineralized) depends on extend of reactions with
the country rock (Edmunds 1994). The identification of major controlling mechanisms of
groundwater chemical composition and dynamics of flow systems are necessary for optimal
management of coastal aquifers (Amiri et al.
2016). Salinization of groundwater due to seawater intrusion can be precisely examined using
the water chemistry data along with hydrogeological assessments (Han et al., 2014). The result
of hydrochemical analysis and field measurements for 79 groundwater samples for three years
and its statistical parameters (i.e., minimum,
maximum and mean) with drinking water specification are summarized in Table 14.1. Hydrogeochemical characteristics and preliminary
investigation of groundwater quality analysis was
performed (Selvakumar et al. 2012; Chandrasekar et al. 2013).
The pH of the analyzed samples that are
alkaline in range varies from 6.17 to 8.9 (average
7.66). The electrical conductivity values vary
from 276 to 14,523 µS/cm with an average value
of 3,563.7 µS/cm in the year 2012. On examining the EC (Saxena et al. 2004 and Mondal et al.
2009) the groundwater was classified into three
categories such as freshwater (<1,500 µS/cm),
brackish water (1500–3000 µS/cm) and saline
water (>3000). Based on the classification, 44%
of the samples are found in saline water and 18%
of the samples have brackish water, and the
remaining 38% samples are fresh in nature.
Abnormal high value of EC indicates the possibility of seawater intrusion. The electrical conductivity of water is an easy indicator of its
salinity or total dissolved content. The spatial
distribution map of TDS in the groundwater
samples are shown in Fig. 14.2.
The maximum values of TDS are reported
from Manapad to Navaladi zones and Chettikulam area where intensive beach placer mining is
noticed and hence making the groundwater
unsuitable for drinking. Moreover, the excavation of beach placer minerals from these sites
disturbs the hydrologic conditions of these
aquifers, which in turn results in seawater intrusion. The higher TDS concentration is due to
other sources like saltpan activities, irrigation
return flow and seepage from untreated domestic
sewages. However, low TDS values are observed
(<1000 mg/l) in villages of Pattinamaruthur,
Veppalodai, Mettupanaiyur, Palayakayal, Punnakayal, Keeranur and Leepuram, which indicates the availability of fresh groundwater.
The cation and anion concentrations confirm
most of the groundwater samples belong to the
order of Na
+ > Mg
2+ > Ca
2+ > K
+ and Cl
− >
SO 4
2− > HCO
−
3 for cations and anions, respectively. The calcium and magnesium concentration varied from 24.1 to 1864.8 mg/l and 28.8 to
1174 mg/l. Sodium, the dominant cation, ranged
between 104.1 and 804.2 mg/l. Most of the
groundwater samples (82%) exceed the maximum permissible limit (200 mg/l) of WHO
(2004). Spatial distribution of sodium (Fig. 14.3)
indicates that the high concentration was noted
14 Impacts of Beach Placer Mineral Mining …
187
Level Measurements
The groundwater levels in the sampling wells
were recorded using a water level recorder. Tidal
water levels were measured at estuary mouth of
nearby beaches and inland dug wells. The
influence of tide on the estuarine water level was
measured using a Schlumberger data logger.
Monitoring wells consisting of 3.2 cm diameter
PVC pipe with a 7.6 cm screen at the bottom
were installed in shore and river banks for tidal
level and temperature measurement (Urish and
McKenna 2004). The pressure transducers
include atmospheric pressure compensation and
were connected to a data logger for continuous
data recording on hourly basis. The location of
the sampling stations, elevation and distance
from the coast was measured using Garmin Etrex 12-channel global positioning system (GPS).
14.1.3 Results and Discussion
14.1.3.1 Groundwater Chemistry
The quality of groundwater has equal importance
as the quantity and this has been recognized only
a couple of decades ago. The characteristic of
groundwater (hard or soft; mineralized or nonmineralized) depends on extend of reactions with
the country rock (Edmunds 1994). The identification of major controlling mechanisms of
groundwater chemical composition and dynamics of flow systems are necessary for optimal
management of coastal aquifers (Amiri et al.
2016). Salinization of groundwater due to seawater intrusion can be precisely examined using
the water chemistry data along with hydrogeological assessments (Han et al., 2014). The result
of hydrochemical analysis and field measurements for 79 groundwater samples for three years
and its statistical parameters (i.e., minimum,
maximum and mean) with drinking water specification are summarized in Table 14.1. Hydrogeochemical characteristics and preliminary
investigation of groundwater quality analysis was
performed (Selvakumar et al. 2012; Chandrasekar et al. 2013).
The pH of the analyzed samples that are
alkaline in range varies from 6.17 to 8.9 (average
7.66). The electrical conductivity values vary
from 276 to 14,523 µS/cm with an average value
of 3,563.7 µS/cm in the year 2012. On examining the EC (Saxena et al. 2004 and Mondal et al.
2009) the groundwater was classified into three
categories such as freshwater (<1,500 µS/cm),
brackish water (1500–3000 µS/cm) and saline
water (>3000). Based on the classification, 44%
of the samples are found in saline water and 18%
of the samples have brackish water, and the
remaining 38% samples are fresh in nature.
Abnormal high value of EC indicates the possibility of seawater intrusion. The electrical conductivity of water is an easy indicator of its
salinity or total dissolved content. The spatial
distribution map of TDS in the groundwater
samples are shown in Fig. 14.2.
The maximum values of TDS are reported
from Manapad to Navaladi zones and Chettikulam area where intensive beach placer mining is
noticed and hence making the groundwater
unsuitable for drinking. Moreover, the excavation of beach placer minerals from these sites
disturbs the hydrologic conditions of these
aquifers, which in turn results in seawater intrusion. The higher TDS concentration is due to
other sources like saltpan activities, irrigation
return flow and seepage from untreated domestic
sewages. However, low TDS values are observed
(<1000 mg/l) in villages of Pattinamaruthur,
Veppalodai, Mettupanaiyur, Palayakayal, Punnakayal, Keeranur and Leepuram, which indicates the availability of fresh groundwater.
The cation and anion concentrations confirm
most of the groundwater samples belong to the
order of Na
+ > Mg
2+ > Ca
2+ > K
+ and Cl
− >
SO 4
2− > HCO
−
3 for cations and anions, respectively. The calcium and magnesium concentration varied from 24.1 to 1864.8 mg/l and 28.8 to
1174 mg/l. Sodium, the dominant cation, ranged
between 104.1 and 804.2 mg/l. Most of the
groundwater samples (82%) exceed the maximum permissible limit (200 mg/l) of WHO
(2004). Spatial distribution of sodium (Fig. 14.3)
indicates that the high concentration was noted
14 Impacts of Beach Placer Mineral Mining …
187