The spatial and temporal results of monitored water parameters are summarized in Table 1. The recorded pH values of lake water samples were found to be within the neutral range (7.05 ± 0.44) during the post-monsoon and shifted marginally towards alkaline (8.25 ± 0.38) during the pre-monsoon season. Seasonal variations were noted for EC, TDS, and TSS contents in lake water, which revealed their higher values in the post-monsoon compared to pre-monsoon period (Table 1). This observation can be explained due to surface runoff influx and soil erosion during the rainy season in lake catchment areas, which result in an increase in suspended and dissolved solids in the lake water. The measured values for dissolved oxygen (DO) ranged between 4.90 and 8.40 mg/L in post-monsoon season with an average of 6.43 mg/L (±1.35) and between 3.40 and 6.20 mg/L during the pre-monsoon period with an average of 4.97 mg/L (±1.02). Increased DO levels in the post-monsoon season could be attributed to turbulence caused in lake water due to precipitation and the influx of runoff water into the lake system. Total hardness (TH) and chloride (Cl−) showed marginally lower values in the post-monsoon season (Table 1) due to dilution effect caused by the infusion of rainwater. Increased DO levels in the post-monsoon season could be attributed to turbulence caused in lake water due to precipitation and the influx of runoff water into the lake system. Biological oxygen demand (BOD) is found to be a little higher than the inland surface water quality guideline during both seasons. The nutrient components (i.e., total nitrogen (TN) and total phosphorous (TP)) in lake water showed clear seasonal variations, of which notable variability was recorded in TN content. The measured values for nutrient components were recorded to be on the higher side during the pre-monsoon season in comparison to the post-monsoon (Table 1). This finding can be correlated to the higher rate of evaporation in the pre-monsoon season (i.e., summer), and also due to the dilution effect during the monsoon period. Likewise, elevated chlorophyll-a (Chl-a) content was recorded during the pre-monsoon and lower values were recorded during the post-monsoon season. This situation can be related to the higher level of nutrients, particularly TP in the lake water during the same period, which promotes algal growth and, therefore, chlorophyll-a content in a monitored lake. Findings of the present investigation on lake water system suggested that concentrations of measured water parameters are very much within the acceptable range for surface waters (IS:2296 1982), with few exceptions.
Descriptive statistics of measured lake water parameters, along with standards of drinking water (BIS 2012) and surface water (IS:2296 1982)
| Water parameters | Pre-monsoon | Post-monsoon | Indian standards for surface water (IS:2296) | BIS (2012), drinking water standards | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | Max | Mean | SD | Min | Max | Mean | SD | Desirable | Permissible | ||
| pH | 7.7 | 8.6 | 8.25 | 0.38 | 6.3 | 7.6 | 6.98 | 0.50 | 6.5–8.5 | 6.5–8.5 | NX |
| EC (μS/cm at 25 °C) | 228 | 490 | 333.33 | 103.67 | 274 | 560 | 429.00 | 95.22 | – | – | – |
| TSS (mg/L) | 16 | 29 | 21.62 | 4.89 | 28 | 46 | 36.40 | 6.91 | – | – | – |
| TDS (mg/L) | 153.24 | 325.6 | 223.69 | 68.72 | 185.4 | 378.5 | 289.47 | 64.71 | 500–1,500 | 500 | 2,000 |
| TA (mg/L) | 86 | 147 | 116.17 | 22.96 | 64 | 136 | 95.33 | 26.85 | – | – | – |
| TH (mg/L) | 28 | 52 | 37.68 | 8.54 | 16 | 24 | 19.97 | 2.74 | 300.00 | – | – |
| DO (mg/L) | 3.4 | 6.2 | 4.97 | 1.02 | 4.9 | 8.4 | 6.43 | 1.35 | 4.00 | – | – |
| BOD (mg/L) | 4.6 | 7.8 | 6.12 | 1.26 | 2.6 | 4.3 | 3.47 | 0.64 | 3.00 | – | – |
| COD (mg/L) | 27 | 38.5 | 32.58 | 4.50 | 16.5 | 27.5 | 21.33 | 4.05 | – | – | – |
| Cl− (mg/L) | 16.5 | 24.5 | 20.87 | 3.30 | 9.8 | 17.2 | 13.72 | 3.03 | 250–600 | 250 | 1,000 |
 (mg/L) | 1.7 | 2.6 | 2.20 | 0.35 | 0.9 | 1.8 | 1.42 | 0.35 | 400.00 | 200 | 400.00 |
Total  (mg/L) | 0.08 | 2.1 | 1.29 | 0.74 | 0.02 | 1.4 | 0.44 | 0.61 | – | – | – |
Total  (mg/L) | 3.6 | 8.7 | 6.10 | 1.78 | 0.09 | 2.8 | 1.72 | 1.00 | 20–50 | 45 | NX |
| Chl-a (μg/L) | 46.5 | 78.4 | 61.70 | 11.87 | 22.9 | 43.8 | 35.12 | 8.50 | – | – | – |
| Fe (mg/L) | 0.64 | 0.9 | 0.78 | 0.09 | 0.52 | 0.76 | 0.65 | 0.09 | 0.3–50 | 0.3 | NX |
| Water parameters | Pre-monsoon | Post-monsoon | Indian standards for surface water (IS:2296) | BIS (2012), drinking water standards | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | Max | Mean | SD | Min | Max | Mean | SD | Desirable | Permissible | ||
| pH | 7.7 | 8.6 | 8.25 | 0.38 | 6.3 | 7.6 | 6.98 | 0.50 | 6.5–8.5 | 6.5–8.5 | NX |
| EC (μS/cm at 25 °C) | 228 | 490 | 333.33 | 103.67 | 274 | 560 | 429.00 | 95.22 | – | – | – |
| TSS (mg/L) | 16 | 29 | 21.62 | 4.89 | 28 | 46 | 36.40 | 6.91 | – | – | – |
| TDS (mg/L) | 153.24 | 325.6 | 223.69 | 68.72 | 185.4 | 378.5 | 289.47 | 64.71 | 500–1,500 | 500 | 2,000 |
| TA (mg/L) | 86 | 147 | 116.17 | 22.96 | 64 | 136 | 95.33 | 26.85 | – | – | – |
| TH (mg/L) | 28 | 52 | 37.68 | 8.54 | 16 | 24 | 19.97 | 2.74 | 300.00 | – | – |
| DO (mg/L) | 3.4 | 6.2 | 4.97 | 1.02 | 4.9 | 8.4 | 6.43 | 1.35 | 4.00 | – | – |
| BOD (mg/L) | 4.6 | 7.8 | 6.12 | 1.26 | 2.6 | 4.3 | 3.47 | 0.64 | 3.00 | – | – |
| COD (mg/L) | 27 | 38.5 | 32.58 | 4.50 | 16.5 | 27.5 | 21.33 | 4.05 | – | – | – |
| Cl− (mg/L) | 16.5 | 24.5 | 20.87 | 3.30 | 9.8 | 17.2 | 13.72 | 3.03 | 250–600 | 250 | 1,000 |
| (mg/L) | 1.7 | 2.6 | 2.20 | 0.35 | 0.9 | 1.8 | 1.42 | 0.35 | 400.00 | 200 | 400.00 |
| Total (mg/L) | 0.08 | 2.1 | 1.29 | 0.74 | 0.02 | 1.4 | 0.44 | 0.61 | – | – | – |
| Total (mg/L) | 3.6 | 8.7 | 6.10 | 1.78 | 0.09 | 2.8 | 1.72 | 1.00 | 20–50 | 45 | NX |
| Chl-a (μg/L) | 46.5 | 78.4 | 61.70 | 11.87 | 22.9 | 43.8 | 35.12 | 8.50 | – | – | – |
| Fe (mg/L) | 0.64 | 0.9 | 0.78 | 0.09 | 0.52 | 0.76 | 0.65 | 0.09 | 0.3–50 | 0.3 | NX |
NX, no relaxation, i.e., values/concentrations within the desirable limit are only acceptable; no values/concentrations are permitted/acceptable beyond the recommended standards.