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Research Article
Assessment of Seasonal Disparity on Hydrogeochemical Facies Distribution in Cooum River, India

A. Dhamodharan, S. Shanthakumar and G.P. Ganapathy

Asian Journal of Earth Sciences, 2016, 9(1), 27-35.


Objective: The environmental stress such as climatic conditions, anthropogenic activities on river water quality and its flow is of challenging interest. In the present study, evaluation of the surface water (in Cooum river, India) quality and the seasonal impact have been investigated. Methodology: Hydrogeochemical facies such as piper plots, chloroalkali indices, kelly index, sodium absorption ratio, magnesium hazard and rock water interaction have been considered to understand the ionic constituents, geochemistry of the river water and its influence on water quality. The water samples were collected seasonally during March, 2013-2014 and are categorized as pre-monsoon, monsoon and post-monsoon. Results: The investigation results reveal that the ionic concentration and organic loads exhibits for all three seasons indicating the anthropogenic activities. Conclusion: The rock water interaction shows that plagioklase weathering is mainly dominant in the sampling sites and the ionic constituents were due to seawater intrusion and gypsum dissolution in the water.

ASCI-ID: 22-131

1. Rivers are considered too vulnerable water bodies as they tend to carry the wastewater from drainage basins2. The various factors such as rainfall, temperature, rock water interactions and other activities plays crucial part of river water quality and the seasonal variation of these factors has a significant role in concentration of pollutants in the river water. Also, the seasonal variation act as a very important factor in controlling the water cycle with active agents of transport such as ions and minerals etc.1. These agents may be in the form of suspended or in dissolved, from the source and has ability to deposit at different locations based on their physicochemical nature3. Hence, it is vital to monitor and prevent river pollution and to have dependable information on the quality of water for effective management2. Ionic constituents present in the river water is relatively small, but significant amounts and are usually originate from weathering of rocks, soil, dissolution of lime, gypsum and other soil minerals4. The variation in river water quality based on the hydrological factors and geochemical variations have been investigated and reported by researchers Shrestha and Kazama5, Hellar-Kihampa et al.6, Koklu et al.7, Kumarasamy et al.3 and Singh et al.2.

Overall literature study suggests that rock weathering and erosion are the two major factors that attribute to the changes in the geochemistry of elements on earth and also the cause for the transport of dissolved and particulate materials by rivers to the sea. Krishnaswami and Singh8 suggested characterising river water with respect to dissolved and particulate concentration of various ions and components in order to understand the rock weathering process. In addition, the rapid urbanization along the river basin is very crucial of the vulnerability of river water quality due to anthropogenic pressures9,10. Hydrogeochemical facies are the best indicators to study about the geochemical interactions in the subsurface of river. Tools such as piper plots, sodium hazard ratio and magnesium hazard helps to identify the influence of ionic constituents and their impact on the river water quality. Cooum river flowing inside the city has been polluted heavily due to anthropogenic activities. Understanding the river quality is very important, as the geology and the river water characteristics depends on the factors such as interaction with solid phases, residence time and anthropogenic impacts11. Hence, in this study the seasonal variation on the hydrogeochemical facies, rock water interactions of Cooum river flowing inside the Chennai city have been investigated.


Study area: River Cooum originates from Kesavaram dam and village at about 48 km West of Chennai. Though river Cooum originates from this dam, the excess water from the Cooum tank (79.82° latitude and 13.02° longitude) joins this course at about 8 km and this is considered as the head of the river Cooum. It flows through Kanchipuram, Thiruvallur and Chennai districts for a distance of about 68 km, after which it flow through the heart of the Chennai city and enters into the sea, Bay of Bengal. The river can be divided into two streams namely upstream and downstream, which is based upon the stretch of the river. The upstream is the flow of river flowing till urban area (Chennai city) and downstream stream is the river flowing inside the urban area (Chennai city). In this study, 11 locations (Fig. 1) have been identified to collect samples from the 18 km stretch of river basin in Chennai city. The study area along with the sampling points is shown in the Fig. 1.

Methodology: The surface water samples from Cooum river were collected from 11 different sampling points in an 18 km stretch of river, which passes through Chennai city. All the samples were collected in pre-sterilized polyethylene bottles and utmost care was taken to fill the bottles without air bubbles at each sampling site during March, 2013-2014 and categorized as pre-monsoon, monsoon and post-monsoon. The sampling locations and their designation are shown in Table 1. The collected samples were labelled and taken into the laboratory using a refrigerator box. The parameters such as pH and Electrical Conductivity (EC) were measured using potable kit (ELICO, India) at the site during sampling. The analysis of water quality parameters such as pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Dissolved Oxygen (DO), sulphate (SO4), chloride (Cl), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), carbonate (CO32–) and bicarbonate (HCO3–) have been analysed by following the standard procedure prescribed by American Public Health Association12. The sampling points in the Cooum river stretch were Napier bridge (SW1), Flag house (SW2), New Secretariat (SW3), Jail Cemetery (SW4), Chindadripet bridge (SW5), Chitratalkies bridge (SW6) and Erson bridge (SW7), Namasivayapuram causeway (SW8), Annanagar bridge (SW9), Aminjikarai bridge (SW10) and Koyembedu bridge (SW11). The analytical data quality was ensured through standardization experiments with duplicates and average has been reported. Statistical analysis for the data such as piper plot and rock water interaction was performed using Aquachem software in order to identify the insights of distribution of composition of Cooum river.

Fig. 1: Sampling locations in the downstream of Cooum river, source of image IRS P6 LISS III, national remote sensing centre, Hyderabad. Month and year of image March, 2013


Hydrogeochemical facies: The physicochemical parameters of the Cooum river has been presented in Table 1. The hydrochemical analysis plot was made using trilinear piper plot13 which is based on the domination of ions. The piper plots of the seasonal variation of Cooum river are presented in Fig. 2. The classification of cation and anion facies, in terms of major ion percentage and water types is based on the domain, in which they occur on the fragments of diagram14,15. It can be noted from the figure that during pre-monsoon season (Fig. 2a), 10 sampling points falls in Na-Cl type and only one sampling point falls in mixed Ca-Mg-Cl. From data plots of hydrogeochemistry it is easily noted that 8 sampling points have dominated Na and K and 3 sampling points shows no dominant type. For ionic constituents, 8 sampling points showed anionic faces (SO4,Cl) and 3 were no dominant type. During monsoon season (Fig. 2b), 9 samples of the study area fall in Na-Cl and 2 samples falls in mixed Ca-Mg-Cl.

Table 1: Physicochemical characteristics of Cooum river

Further, from data plots, it can be noted that hydro geochemistry of 9 sampling points is dominated with Na and K and 2 sampling points exhibits no dominant type. Likewise, 3 sampling points were dominated in chloride type and 8 sampling points shows no dominant type. Similarly, during post-monsoon season (Fig. 2c), it can be noted from the figure that all 11 samples falls in Na-Cl. From data plots, hydrogeochemistry is dominated by 10 sampling points that possess Na and K and 3 exhibits no dominant type. For ionic constituents, 5 sampling points exhibits chloride type, 4 sampling points showed no dominant type and 2 sampling points possess SO4 type. It is evident from the plots that Na+-Cl– and Ca+-Na+-HCO3– are the two major types present in study area, which is agreed with results of dominant and cations.

The indices such as of chloroalkaline indices (CAI and CAII), Sodium Absorption Ratio (SAR), Kelly’s Index (KI) and Magnesium Hazard (MH) for the surface water were calculated and are presented in Table 2. In order to observe changes in the chemical constituents during surface water runoff16, the calculation of chloroalkaline indices (CAI and CAII) helps to give an indication of ion exchange between the subsurface water and its environment17-19. The chloroalkali indices indicates the ion exchange process i.e., Ca2+ and Mg2+ from the surface water will be exchanged between Na+ and K+ of the host rock. Both the indices CAI and CAII can yield positive and negative values based upon the nature of the water. Negative value indicates the process of normal ion exchange process and positive value indicates the reverse exchange process in the surface water. In the present study, the chloroalkali indices exhibits positive values of surface water analysed indicating the reverse exchange process in the study area.

Kelly’s index and magnesium hazard were calculated for the surface water for all the three seasons.

Fig. 2(a-c): Piper trilinear plots of seasonal variation in Cooum river (a) Pre-monsoon, (b) Monsoon and (c) Post-monsoon

Kelly’s index of more than one indicates that water is unfit for any agricultural/domestic purposes. It can be noted from Table 1 that all the sampling locations falls over unity for all the three seasons indicating unsuitability of water for any other practical purposes.

Table 2: Hydrogeochemical facies distribution over Cooum river

Similarly, magnesium hazard (high levels of magnesium) will degrade the soil quality by converting to alkaline and make it unsuitable for any plantation near the banks of the river.

Salinity and sodium hazard: Sodium Absorption Ratio (SAR) isused to predict the sodium of high carbonate water in the absence of no residual alkali4. It is also the measure of relative proportions of sodium ions in aqueous phase to those of calcium and magnesium20 and can be calculated by using the Eq. 1:


For the present study, based on the USSL diagram, the hazard nature was found out by correlating SAR and EC and are shown in the Fig. 3. It can be noted from the figure that during pre-monsoon, sampling points (S1-S5) exhibits high levels of sodium hazard and sampling points (S6-S11) exhibits medium and low levels of sodium hazard. Similarly, during monsoon season, sampling points (S1-S4) falls in high levels and points (S5-S11) exhibits moderate and lower level of sodium hazard. However, the ratio is less than pre-monsoon level indicating the impact of rainfall among the sampling points. While, post-monsoon analysis exhibited sampling points (S1-S5, S7 and S11) indicating highlevels of sodium hazard and points (S6, S8-S10) shows low level of sodium hazard indicating high levels of pollutant discharge through anthropogenic activities.

Salinity hazard was high during post-monsoon season when compared with pre-monsoon and monsoon season. During pre-monsoon season sampling points (S1-S5) exhibits C4, which is very high level of salinity hazard which may be due to the intrusion of ocean water and sampling sites (S6-S11) shows low level of salinity hazard.

Fig. 3(a-c): SAR vs salinity hazard for river Cooum during various season (a) Pre-monsoon, (b) Monsoon and (c) Post-monsoon

Similarly, sampling sites (S1-S4) reveals the presence of high level of salinity hazard and other sites (S5-S11) exhibited low salinity hazard indicating effect of the rainfall over the season.

Table 3: Effect of seasonal variation of rock water interaction over Cooum river

Rock source deduction: Rock source deduction helps to gain insight to the possible origin of water samples. These results presents a general overview based on the ion ratio found in a sample, which are compared to the ratios of respective ions in reactive minerals. Table 3 provides the summary of criterion of rock source deduction21. It can be noted from the Table 3 that Plagioklase weathering was dominant during monsoon season indicating 63% of sampling points were recorded. The sodium ion was predominant over all the sampling points, which may be due to sodium source other than halite-albite as shown in the Table 3. The presence of calcium ions were high exhibiting 90% of sampling points during pre-monsoon season followed by 63% of sampling points during monsoon season, which is due to ion exchange or calcite precipitation. The total dissolved solids in the samples were due to carbonate weathering or brine or seawater intrusion in all the sampling points. Similarly, the chloride ratio in all sampling points showed that influence of rock weathering of the Cooum river. During pre-monsoon and post-monsoon the presence of HCO3 was 36 and 54% indicating gypsum dissolution due to natural process in the sampling points. However, during monsoon season all the points exhibited higher level of HCO3, which is due to mixing of sea water and dissolution of atmospheric CO2 in other areas.



This study reports the influence of seasonal variation on hydro geochemistry of surface water of Cooum river basin. It was noted that the Plagioklase weathering was very high particularly in monsoon season. In addition, it is also noted calcium precipitation, carbonate weathering and rock weathering is also predominant characteristics found in the Cooum river. The presence of Na+-Cl– and Ca+-Na+-HCO3– ionic types were found to be more dominant in the study area of Cooum river stretch. Similarly, the analysis of the hydrogeochemical indices such CAI, CAII, SAR, KI and MH indicated that all the sampling points of the Cooum river exceeds the permissible limits for domestic use and water is not suitable for living of aquatic organisms in river water, which is mainly due to the anthropogenic activities. The results reveal that river is polluted and not suitable for domestic, irrigation and aquaculture purposes. Hence continuous monitoring and cleaning mechanism mainly desiliting of deposition of hazardous silt is essential to assess the impact of pollution loads and restoration of Cooum river.

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