1. Introduction
Water plays a major role in the lives of all organisms, as it is an important source of life on earth. Water is used for various needs such as irrigation, transportation, drinking, electricity production and entertainment activities, including boating and swimming. Overuse of water is a serious threat to life forms, as it leads to the lowering of the water table. Rivers are surface water sources and are included under the freshwater category. The river Neyyar is one of the 44 famous rivers in Kerala, and it is the southernmost river in the state. It has a length of 56 kilometres, originates from Agastya Mala in the Western Ghats, flows through Neyyattinkara taluk in Thiruvananthapuram district and joins the Arabian Sea near Poovar. The water is mainly used for domestic, drinking, irrigation and recreational purposes. At present, the entire world, especially developing countries, is facing water-related problems such as scarcity of drinking water, lack of freshwater resources and poor water security. Water-related problems have turned critical in the small catchment rivers of developing countries (Padmalal et al., 2011). The present study aims to analyse the current water quality status of the Neyyar River. Physicochemical parameters such as temperature, pH, turbidity, total dissolved solids, electrical conductivity, total hardness and sodium content were chosen for the analysis.
2. Materials and Methods
2.1. Study Area
The river Neyyar is one of the major rivers of Kerala. It has a length of 56 kilometres and originates from Agastya Mala in the Western Ghats. It flows through Thiruvananthapuram district and joins the Arabian Sea near Poovar. It lies between 8° 36′ 56.2428″ N, 77° 14′ 45.5604″ E and 8° 18′ 20.0124″ N, 77° 4′ 47.0064″ E (Figure 1). Five sites along the river stretch were selected for the present study, namely Arattu Kadavu (S1), Arakkunnu (S2), Vadakkekotta (S3), Alatharackal (S4) and Panchikattu Kadavu (S5). Sites S1 (Arattu Kadavu), S2 (Arakkunnu) and S3 (Vadakkekotta) are located upstream, whereas sites S4 (Alatharackal) and S5 (Panchikattu Kadavu) are located downstream. Sampling was done in the early morning using clean 2-litre polythene bottles, and the collected samples were transported to the laboratory for analysis. The study period was from June 2022 to November 2022. The study was done by considering the seasons in Kerala, mainly the southwest monsoon (June 2022 to August 2022) and the northeast monsoon (October 2022 and November 2022).
2.2. Physicochemical Analysis
Physicochemical analysis was carried out for water parameters such as temperature, pH, turbidity, total dissolved solids, electrical conductivity, total hardness and sodium content by following the standard methods of the American Public Health Association (APHA, 2017) and IS 3025. Water temperature was measured at the time of sampling using a sensitive mercury thermometer. The pH of the water was recorded in the laboratory using a pH meter. The turbidity of the water samples was noted using a digital Nephelo Turbidity Meter (Systronics 132). Total dissolved solids (TDS) in the water samples were calculated using the ‘Total Dissolved Solids Dried at 180 °C’ method. Electrical conductivity was measured using a conductivity meter (Elico CM 180). Total hardness in terms of CaCO3 was determined using the EDTA titrimetric method. The sodium level in the water samples was determined by the flame emission photometric method. The data obtained from the study were compared with the drinking water standards of the World Health Organization (WHO, 2022) and the Bureau of Indian Standards specification IS 10500 (BIS, 1991).
3. Results
The average rainfall (mm) of Neyyattinkara taluk recorded from June 2022 to November 2022 is shown in Figure 2. A minimum rainfall of 133.4 mm was recorded during the northeast monsoon (November), and a maximum of 444.7 mm was recorded during the southwest monsoon (August). Water temperature ranged from 24.2 °C to 27.35 °C. Seasonal variations of water temperature in the Neyyar River are given in Tables 1 and 2. During the southwest monsoon, the minimum water temperature was found at S1 (Arattu Kadavu) and the maximum water temperature was found at S5 (Panchikattu Kadavu). In the northeast monsoon, the minimum water temperature was found at S1 (Arattu Kadavu) and the maximum water temperature was found at S5 (Panchikattu Kadavu) (Figure 3). Seasonal variations of pH in the Neyyar River are given in Tables 1 and 2. During the southwest monsoon, the minimum pH was found at S1 (Arattu Kadavu) and the maximum pH was found at S5 (Panchikattu Kadavu). In the northeast monsoon, the minimum pH was found at S1 (Arattu Kadavu) and the maximum pH was found at S4 (Alatharackal) (Figure 4). The turbidity of the water samples was recorded seasonally. Seasonal variations in the turbidity of the Neyyar River are recorded in Tables 1 and 2. During the southwest monsoon, the minimum turbidity was found at S1 (Arattu Kadavu) and the maximum turbidity was found at S5 (Panchikattu Kadavu). In the northeast monsoon, the minimum turbidity was found at S1 (Arattu Kadavu) and the maximum turbidity was found at S5 (Panchikattu Kadavu) (Figure 5).
Total dissolved solids in the water samples were recorded seasonally. Seasonal variations of total dissolved solids in the Neyyar River are given in Tables 1 and 2. During the southwest monsoon, the minimum value of total dissolved solids was found at S1 (Arattu Kadavu) and the maximum value was found at S5 (Panchikattu Kadavu) (Figure 6). The electrical conductivity of the water samples was recorded seasonally. During the northeast monsoon, the minimum value of electrical conductivity was found at S1 (Arattu Kadavu) and the maximum value was found at S5 (Panchikattu Kadavu) (Figure 7).
The total hardness of the water samples, in terms of CaCO3, was recorded seasonally. Seasonal variations of total hardness in the Neyyar River are given in Tables 1 and 2. During the southwest monsoon, the minimum value of total hardness was found at S1 (Arattu Kadavu) and the maximum value was found at S5 (Panchikattu Kadavu). In the northeast monsoon, the minimum value of total hardness was found at S1 (Arattu Kadavu) and the maximum was found at S5 (Panchikattu Kadavu) (Figure 8). The sodium content of the water samples was recorded seasonally. Seasonal variations of sodium content in the Neyyar River are given in Tables 1 and 2. During the southwest monsoon, the minimum sodium level was found at S1 (Arattu Kadavu) and the maximum was found at S5 (Panchikattu Kadavu) (Figure 9).
| Sl. No. | Parameters | BIS, IS 10500 | WHO | Sites of Neyyar River | ||||
|---|---|---|---|---|---|---|---|---|
| S1 | S2 | S3 | S4 | S5 | ||||
| 1 | Temperature (°C) | – | – | 24.7±0.50 | 24.8±0.33 | 25.5±0.73 | 25.73±0.66 | 27±0.45 |
| 2 | pH | 6.5–8.5 | 7–8.5 | 6.81±0.36 | 6.82±0.38 | 7.13±0.45 | 7.11±0.10 | 7.53±0.34 |
| 3 | Turbidity (NTU) | 1–5 | 5 | 12.33±2.05 | 21±1.63 | 24.67±3.40 | 23.33±6.24 | 26.67±6.18 |
| 4 | Total Dissolved Solids (mg/L) | 500–2000 | 500–1000 | 22.27±2.50 | 36.17±3.18 | 73.27±2.96 | 202.83±15.89 | 571.33±76.52 |
| 5 | Electrical Conductivity (µS/cm) | – | 400 | 33.07±4.35 | 46.17±4.62 | 83.9±7.24 | 54.87±6.81 | 1112.87±529.69 |
| 6 | Total Hardness as CaCO3 (mg/L) | 200–600 | 100–500 | 38±4.90 | 68±18.24 | 152.67±47.36 | 343±52.20 | 589±69.08 |
| 7 | Sodium (mg/L) | – | 200 | 1.03±0.63 | 2.54±1.40 | 8.20±4.95 | 58.27±14.84 | 89.42±11.11 |
| Sl. No. | Parameters | BIS, IS 10500 | WHO | Sites of Neyyar River | ||||
|---|---|---|---|---|---|---|---|---|
| S1 | S2 | S3 | S4 | S5 | ||||
| 1 | Temperature (°C) | – | – | 24.6±0.65 | 25.27±0.54 | 26.13±0.57 | 26.87±0.58 | 27.5±0.24 |
| 2 | pH | 6.5–8.5 | 7–8.5 | 6.41±0.30 | 6.71±0.11 | 6.92±0.23 | 7.28±0.18 | 6.99±0.39 |
| 3 | Turbidity (NTU) | 1–5 | 5 | 5±3.74 | 8.33±2.36 | 16.67±4.08 | 6±5.66 | 15±8.16 |
| 4 | Total Dissolved Solids (mg/L) | 500–2000 | 500–1000 | 23.2±3.19 | 37.2±2.82 | 64.67±10.25 | 300.27±136.77 | 810.7±146.02 |
| 5 | Electrical Conductivity (µS/cm) | – | 400 | 39.13±2.55 | 50.73±5.71 | 67.5±7.16 | 70.83±4.74 | 1149.83±116.39 |
| 6 | Total Hardness as CaCO3 (mg/L) | 200–600 | 100–500 | 51.33±8.18 | 90±9.20 | 198±37.56 | 413±36.67 | 698.67±74.12 |
| 7 | Sodium (mg/L) | – | 200 | 0.92±0.07 | 5.51±1.51 | 10.07±0.83 | 53.88±4.07 | 109.57±12.67 |
4. Discussion
According to the results, fluctuations are noticed in the physicochemical parameters of water at the selected sites along the Neyyar River. Fluctuations in the physicochemical parameters can be correlated with environmental conditions. The average rainfall data of Neyyattinkara taluk from June 2022 to November 2022 indicated that higher rainfall occurred during the southwest monsoon than during the northeast monsoon. Thus, the rainfall pattern could bring about an alteration in the physicochemical parameters of the Neyyar River water. The water temperature of the Neyyar River during the northeast monsoon is higher than that during the southwest monsoon. This is due to the high rainfall observed during the southwest monsoon. Other reasons for the fluctuation in river water temperature include early morning sampling, the intensity of solar radiation and climatic conditions. Similar observations were also recorded by Abhilash et al. (2015) in the Neyyar River. Temperature can alter the chemical reactions in water and also affect the odour and taste of water (Trivedy & Goel, 1986). Normal pH in water ranges from 6.5 to 8.5. The pH of the Neyyar River water ranged between these limits. The pH noticed during the northeast monsoon is higher than that during the southwest monsoon, and S5 (Panchikattu Kadavu) showed the maximum pH value compared to the other sites. Similar pH values were recorded by Abhilash et al. (2015) in the Neyyar River. According to Abhilash et al. (2015), the pH value of the Neyyar River water showed an increase from freshwater to coastal areas. In the Neyyar River, higher turbidity was observed during the southwest monsoon than during the northeast monsoon. The overall turbidity recorded in the study period was found to be above the permissible limits. Similar results were also recorded by Shaniya et al. (2018) in the Thamaraparani River. According to Shaniya et al. (2018), during the monsoon season, a high range of turbidity was recorded because of plankton inflow and the mixing of plankton, suspended and colloidal particles. Reasons for turbidity in water include the deposition of sediments, sand mining, etc.
Total dissolved solids in water comprise the organic and inorganic substances that can be measured. Total dissolved solids have a direct relationship with electrical conductivity. TDS in the Neyyar River water was found to be higher at S5 (Panchikattu Kadavu) than at S1 (Arattu Kadavu) during the northeast monsoon. A sudden increase in TDS indicates water pollution from extraneous sources (Aboo & Mandal, 1967). The conductivity of water depends on its temperature and the amount of dissolved salts present, either through human activities or through natural processes (Pal et al., 2015). In the Neyyar River, the conductivity values were above the permissible limits. High values of electrical conductivity were recorded at S5 (Panchikattu Kadavu) during both the southwest monsoon and the northeast monsoon. Similar observations were also recorded by Shaniya et al. (2018) in the Thamaraparani River.
Hardness can prevent the lathering of soap in water and thus increase the boiling point (Trivedy & Goel, 1986). The hardness of the Neyyar River water showed a slight deviation at some sites and is below the permissible limits. An increase in hardness was observed from S1 (Arattu Kadavu) to S5 (Panchikattu Kadavu). Hardness in water during the northeast monsoon was found to be higher than during the southwest monsoon. Hardness of water between 75 mg/L and 150 mg/L could help in the productivity of fish (Basant Kumar et al., 2011). Among the five sites of the Neyyar River, high sodium was recorded at S5 (Panchikattu Kadavu) and low sodium was observed at S1 (Arattu Kadavu).
5. Conclusion
The river Neyyar plays an integral part in the lives of people who live near the river basin, as they depend on the river water for their daily needs. The results obtained from the present study of the water samples were compared with the general standards prescribed for drinking water. Deviations are noticed for some parameters, such as turbidity, electrical conductivity and total hardness, in comparison with the WHO and BIS (IS 10500) standards. The Neyyar River shows an increase in the values of physicochemical parameters on moving from upstream to downstream. Panchikattu Kadavu (S5), near Poovar, shows higher readings than Arattu Kadavu (S1), which is near the Neyyar Dam. This indicates the deterioration of water quality due to anthropogenic activities, agricultural practices, construction works, disposal of wastes, sand mining, hospital discharges and the mixing of drainage as the river flows through human settlements. Therefore, the present study indicates the immediate need to protect the river from damage, pollution and unethical human practices in the use of river water. This can ensure the good quality of the river water, making it fit for human needs and also for other organisms in water.
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