The results of analysed physico-chemical and biological parameters of ground water collected from thirty villages in pre and post monsoon seasons are presented in Table 4.
Table 4
Physico-chemical and Biological parameters during Pre & Post monsoon Seasons
S.No. | Season | pH | EC | TDS | TA | TH | Ca+ 2 | Mg+ 2 | Cl− | SO4 − 2 | DO | BOD |
S1 | Pre-monsoon | 7.15 | 500 | 320 | 216 | 140 | 24.25 | 19.37 | 35.5 | 10.00 | 4.8 | 2.4 |
Post-monsoon | 7.72 | 500 | 320 | 212 | 375 | 126.00 | 14.62 | 77.9 | 11.0 | 4.2 | 1.8 |
S2 | Pre-monsoon | 8.19 | 42 | 279 | 143 | 65 | 10.80 | 8.90 | 58.0 | 6.06 | 8.9 | 5.0 |
Post-monsoon | 7.07 | 1110 | 790 | 235 | 132 | 38.00 | 19.5 | 207.0 | 12.9 | 8.1 | 4.9 |
S3 | Pre-monsoon | 7.60 | 1480 | 1040 | 349 | 230 | 42.00 | 25.85 | 102.0 | 69.00 | 4.1 | 2.0 |
Post-monsoon | 7.70 | 1589 | 1052 | 517 | 328 | 49.00 | 50.41 | 297.0 | 67.0 | 3.9 | 1.6 |
S4 | Pre-monsoon | 7.50 | 1465 | 998 | 354 | 225 | 43.00 | 23.58 | 108.0 | 73.00 | 4.0 | 2.2 |
Post-monsoon | 7.67 | 900 | 576 | 268 | 200 | 44.00 | 21.92 | 76.4 | 42.0 | 4.4 | 2.1 |
S5 | Pre-monsoon | 6.80 | 301 | 198 | 139 | 78 | 14.60 | 9.30 | 78.0 | 5.90 | 8.1 | 6.3 |
Post-monsoon | 7.18 | 238 | 178 | 99 | 58 | 18.00 | 8.5 | 43.0 | 8.9 | 7.7 | 5.2 |
S6 | Pre-monsoon | 7.20 | 568 | 327 | 178 | 165 | 39.00 | 15.38 | 115.0 | 84.00 | 3.8 | 2.1 |
Post-monsoon | 7.80 | 500 | 320 | 204 | 135 | 28.00 | 15.83 | 30.7 | 80.0 | 4.4 | 2.0 |
S7 | Pre-monsoon | 7.32 | 500 | 320 | 238 | 180 | 26.05 | 28.01 | 50.4 | 07.00 | 4.0 | 2.0 |
Post-monsoon | 7.79 | 500 | 320 | 146 | 100 | 36.00 | 2.44 | 165.0 | 13.0 | 6.2 | 1.8 |
S8 | Pre-monsoon | 7.30 | 1355 | 872 | 303 | 209 | 71.00 | 12.07 | 203.0 | 139.00 | 6.9 | 2.8 |
Post-monsoon | 7.73 | 1000 | 640 | 490 | 265 | 38.00 | 41.41 | 173.0 | 32.0 | 4.0 | 2.1 |
S9 | Pre-monsoon | 7.50 | 989 | 619 | 212 | 135 | 43.00 | 9.07 | 15.5 | 77.00 | 4.1 | 2.3 |
Post-monsoon | 7.30 | 1190 | 810 | 334 | 156 | 38.00 | 17.94 | 246.0 | 72.0 | 4.5 | 2.4 |
S10 | Pre-monsoon | 7.19 | 842 | 561 | 395 | 149 | 39.50 | 11.60 | 63.0 | 11.20 | 8.5 | 14.6 |
Post-monsoon | 6.70 | 889 | 602 | 335 | 151 | 44.50 | 11.3 | 63.0 | 3.40 | 5.3 | 1.1 |
S11 | Pre-monsoon | 7.65 | 2695 | 1680 | 499 | 356 | 45.80 | 12.21 | 679.0 | 92.00 | 4.7 | 2.2 |
Post-monsoon | 8.45 | 2479 | 1728 | 537 | 322 | 73.85 | 30.61 | 813.0 | 106.0 | 4.3 | 2.5 |
S12 | Pre-monsoon | 7.30 | 580 | 348 | 182 | 157 | 40.00 | 13.53 | 108.0 | 81.00 | 3.9 | 2.0 |
Post-monsoon | 7.20 | 785 | 498 | 273 | 143 | 41.00 | 13.5 | 217.0 | 79.0 | 4.8 | 2.5 |
S13 | Pre-monsoon | 7.52 | 1290 | 812 | 295 | 235 | 56.25 | 20.62 | 135.0 | 27.00 | 4.7 | 2.3 |
Post-monsoon | 8.05 | 790 | 711 | 325 | 277 | 61.80 | 20.12 | 152.0 | 31.0 | 3.9 | 2.1 |
S14 | Pre-monsoon | 8.21 | 1378 | 919 | 198 | 135 | 29.20 | 16.45 | 41.0 | 18.90 | 3.9 | 2.5 |
Post-monsoon | 7.10 | 1629 | 1092 | 293 | 185 | 51.90 | 9.9 | 263.0 | 22.8 | 5.1 | 1.9 |
S15 | Pre-monsoon | 7.55 | 1800 | 1230 | 1050 | 210 | 65.10 | 26.50 | 309.0 | 23.60 | 7.8 | 6.0 |
Post-monsoon | 7.30 | 1984 | 1210 | 434 | 235 | 63.50 | 28.2 | 318.0 | 30.2 | 8.9 | 6.3 |
S16 | Pre-monsoon | 7.50 | 1190 | 753 | 395 | 243 | 52.00 | 27.53 | 247.0 | 82.00 | 4.3 | 1.9 |
Post-monsoon | 7.80 | 1370 | 873 | 455 | 285 | 28.00 | 52.53 | 555.0 | 84.0 | 4.3 | 1.7 |
S17 | Pre-monsoon | 7.39 | 300 | 192 | 72 | 60 | 18.04 | 3.65 | 24.2 | 04.00 | 4.4 | 2.4 |
Post-monsoon | 7.96 | 400 | 256 | 76 | 70 | 28.00 | 0.00 | 23.8 | 05.0 | 6.0 | 3.6 |
S18 | Pre-monsoon | 7.62 | 1590 | 1016 | 318 | 235 | 54.70 | 13.80 | 356.0 | 69.00 | 3.9 | 2.2 |
Post-monsoon | 8.45 | 1290 | 890 | 345 | 215 | 71.19 | 11.91 | 245.0 | 69.0 | 5.4 | 1.1 |
S19 | Pre-monsoon | 7.39 | 1020 | 675 | 341 | 159 | 28.40 | 21.80 | 78.0 | 8.20 | 7.9 | 5.1 |
Post-monsoon | 7.30 | 2152 | 1443 | 607 | 181 | 29.30 | 25.7 | 229.0 | 40.8 | 5.7 | 2.3 |
S20 | Pre-monsoon | 7.40 | 978 | 625 | 209 | 139 | 41.00 | 10.07 | 25.75 | 73.00 | 4.2 | 1.9 |
Post-monsoon | 7.76 | 800 | 512 | 214 | 175 | 36.00 | 20.71 | 106.0 | 27.0 | 4.8 | 2.3 |
S21 | Pre-monsoon | 7.51 | 1380 | 875 | 236 | 225 | 46.10 | 10.28 | 524.0 | 81.00 | 4.1 | 2.1 |
Post-monsoon | 8.01 | 899 | 675 | 252 | 217 | 39.05 | 60.25 | 90.5 | 51.0 | 4.1 | 2.3 |
S22 | Pre-monsoon | 7.37 | 600 | 384 | 322 | 150 | 26.05 | 20.71 | 50.4 | 17.00 | 4.0 | 1.6 |
Post-monsoon | 7.87 | 800 | 512 | 100 | 115 | 40.00 | 3.65 | 123.0 | 04.0 | 5.0 | 1.8 |
S23 | Pre-monsoon | 7.40 | 1205 | 735 | 388 | 234 | 49.00 | 25.73 | 243.0 | 80.00 | 4.1 | 2.1 |
Post-monsoon | 7.06 | 700 | 448 | 178 | 130 | 32.00 | 12.18 | 75.5 | 43.0 | 4.0 | 2.1 |
S24 | Pre-monsoon | 6.83 | 600 | 384 | 198 | 230 | 48.10 | 14.62 | 76.2 | 12.00 | 4.0 | 2.0 |
Post-monsoon | 6.76 | 600 | 384 | 190 | 130 | 32.00 | 12.18 | 46.5 | 25.0 | 4.8 | 1.8 |
S25 | Pre-monsoon | 7.30 | 1380 | 879 | 314 | 212 | 73.00 | 11.78 | 214.0 | 145.0 | 7.4 | 2.7 |
Post-monsoon | 7.50 | 1095 | 697 | 63 | 253 | 31.00 | 40.39 | 247.0 | 138.0 | 7.6 | 2.9 |
S26 | Pre-monsoon | 7.28 | 1692 | 1133 | 289 | 240 | 41.00 | 35.10 | 212.0 | 28.12 | 9.1 | 5.9 |
Post-monsoon | 7.40 | 1545 | 1032 | 280 | 237 | 44.40 | 30.5 | 214.0 | 19.23 | 7.3 | 4.3 |
S27 | Pre-monsoon | 6.90 | 2010 | 1240 | 398 | 294 | 62.10 | 29.40 | 335.0 | 20.38 | 8.1 | 5.8 |
Post-monsoon | 7.10 | 1790 | 1191 | 377 | 243 | 59.40 | 34.3 | 359.0 | 34.9 | 7.0 | 5.0 |
S28 | Pre-monsoon | 7.10 | 1198 | 792 | 315 | 143 | 31.00 | 14.80 | 106.0 | 5.00 | 8.1 | 4.9 |
Post-monsoon | 7.16 | 1062 | 711 | 253 | 138 | 39.10 | 10.3 | 114.0 | 19.60 | 5.1 | 1.3 |
S29 | Pre-monsoon | 7.20 | 1790 | 1175 | 504 | 249 | 70.10 | 25.50 | 198.0 | 22.30 | 8.7 | 5.9 |
Post-monsoon | 7.00 | 1570 | 1020 | 396 | 218 | 70.10 | 20.3 | 224.0 | 23.5 | 8.3 | 5.5 |
S30 | Pre-monsoon | 7.70 | 1095 | 696 | 374 | 147 | 44.65 | 13.15 | 208.0 | 43.00 | 4.0 | 2.0 |
Post-monsoon | 8.39 | 785 | 698 | 301 | 202 | 42.61 | 19.21 | 199.0 | 31.0 | 4.4 | 1.9 |
All parameters are in mg/L except pH and EC (µS/cm).
Concentration of Hydrogen Ion – pH
There's no scientific basis that the pH of drinking water has an impact on health (WHO, 2011b). But the pH of water can indirectly affect human health. The pH of groundwater in all the villages during pre-monsoon and post-monsoon periods is in permissible limit of 6.5 to 8.5 (BIS-IS:10500). pH ranges between 6.8 (Dosapadu) to 8.21 (Korumamidi) and 6.76 (Rangapalem) to 8.45 (Jagannadhapuram) with an average value of 7.4 and 7.54 during pre and post monsoon seasons respectively. Average values of pH represent slightly alkaline nature of groundwater. pH determines the suitability of water for various purposes (Jyothirmayee, 2016).
Low pH values are observed as 6.80 in Dosapadu (S5) of Denduluru mandal and 6.76 in Rangapalem (S24) of Chintalapudi mandal during pre-monsoon and post-monsoon respectively. Maximum pH 8.21 is observed at Korumamidi (S14) village of Nidadavolu mandal during pre-monsoon and 8.45 is noticed at Jagannadhapuram (S11), Munduru (S18) of Pedavegi mandal during post-monsoon season. High pH values (more than 8.00) are observed at Korumamidi (S14) of Nidadavolu mandal, Jagannadhapuram (S11), Munduru (S18), Pedavegi (S21), Vijayarai (S30) and Koppulavarigudem (S13) villages of Pedavegi mandal in both pre and post monsoon seasons.
Spatial distribution of pH in pre and monsoon seasons is shown in Fig. 2. Very few patches in both the seasons represent alkaline nature of the samples (pH > 8) and are situated in SE & SW portions in pre-monsoon season & SW portion in post monsoon season. Alkaline pH is more favorable for fluoride dissolution (Keshavarzi et al. 2010).
Electrical Conductivity – EC
Conductance is a calculation of the electric flow capability of water that is specifically related to ion concentration in the water (EPA, 2012). Electrical conductivity during pre-monsoon period varies between 42 µS/cm (Denduluru) to 2695 µS/cm (Jagannadhapuram) and 238 µS/cm (Dosapadu) to 2479 µS/cm (Jagannadhapuram) in post monsoon period. Conductivity of the groundwater stands at an average of 1127µS/cm, 1098 µS/cm in pre and post monsoon seasons respectively.
High EC values of 2695 µS/cm and 2479 µS/cm are observed in Jagannadhapuram (S11) of Pedavegi mandal during pre-monsoon and post-monsoon periods. 70% of samples during pre-monsoon and 60% samples during post-monsoon exceeded the permissible limit of 800 µS/cm (BIS-IS: 10500). Higher EC values throughout pre-monsoon than that of post-monsoon season are due to decreasing levels in water table. During post-monsoon, lower EC levels are attributed to precipitation dilution (Dandge and Patil, 2023). Water leakage from the surface raises water concentration in the water body during pre-monsoon season and increases electric conductivity (Mandal et al. 2019).
Spatio-temporal distribution of EC is presented in Fig. 3. During pre-monsoon, not as much of area with desirable limits of EC and spreads in NW and S portions. But during post-monsoon, the extent of those trivial portions are highly increased and those are identified in NW, SW and S portions. Highest EC (> 2000 µS/cm) is spread across SW and S portions during both the seasons. Higher electrical conductivity values are observed in most of the villages.
Total Dissolved Solids - TDS
TDS ranges from 192 mg/L (Lingagudem) to 1680 mg/L (Jagannadhapuram) and 178 mg/L (Dosapadu) to 1728 mg/L (Jagannadhapuram) in pre-monsoon and post-monsoon seasons respectively (Table 4). Minimum TDS values are observed i.e. 192 mg/L in Lingagudem (S17) of Chintalapudi mandal in pre-monsoon and 178 mg/L in Dosapadu (S5) of Denduluru mandal in post monsoon. The maximum TDS values of 1680 mg/L and 1728 mg/L are observed in Jagannadhapuram (S11) of Pedavegi mandal in pre-monsoon and post-monsoon seasons correspondingly. Consumers often reported to have a poor taste of water with high TDS for drinking purpose (Young et al. 1996). TDS values in 21 villages (71%) during post-monsoon and 22 villages (73.33%) in pre-monsoon exceeded the permissible limit of 500 mg/L. The agricultural practices, residential runoff, leaching of soil and discharges from industrial or sewage treatment plants are the primary sources for TDS (Boyd, 2000). Higher rates of infiltration of water due to sandstone formations leads to increase of impurities, ion concentration results in higher TDS values (Sarithadevi et al. 2016). Spatio-Temporal distribution of TDS is illustrated in Fig. 4. NW region and patches of SW portion are in permissible limits during pre and post monsoon seasons.
Total Alkalinity
Alkalinity is the most important parameter of groundwater and it depends on pH values which is a measure of the carbonate, bicarbonate and hydroxide ions present in water (Sundus, 2021). Alkalinity ranges from 72 mg/L to 1050 mg/L and 63 mg/L to 607 mg/L in pre and post monsoon seasons respectively. Minimum values i.e. 72 mg/L in Lingagudem (S17) village during pre-monsoon and 63 mg/L in Saggonda (S25) village in post monsoon season are observed. Maximum values i.e. 1050 mg/L in Kothapalli (S15) village and 607 mg/L in Nidadavolu (S19) village are observed during pre and post monsoon seasons respectively. Alkalinity of ground water is in permissible limit of 200 mg/L in seven villages (23.33% − 7 out of 30) during pre-monsoon and in six villages (20% − 6 out of 30) during post-monsoon. Alkalinity exceeds the permissible limits in all remaining villages in both seasons Presence of bicarbonates trigger the alkalinity in groundwater (Adams et al. 2001). High alkalinity of drinking water is injurious to human health. It disturbs normal pH of body fluids and impairs the enzyme function in body (Geetu and Anil, 2017). Spatial and temporal distribution of alkalinity is shown in Fig. 5. Smallest patch of NW during pre-monsoon and smaller parts in W and NW are in desirable limits. The remaining parts of the area in both seasons exceeded the permissible limits.
Calcium-Ca 2+
Ca2+ concentration is ranging from 10.8 mg/L to 73 mg/L and 18 mg/L to 126 mg/L in pre monsoon and post monsoon seasons respectively. Minimum calcium values i.e. 10.8 mg/L in Denduluru (S2) during pre-monsoon and 18 mg/L in Dosapadu (S5) in post monsoon are observed. Maximum calcium values i.e. 73 mg/L in Saggonda (S25) during pre-monsoon season and 126 mg/L in Chintalapudi (S1) during post monsoon season are noticed. Calcium concentration of groundwater in all villages (100%) during pre-monsoon and in 29 villages (97%) during post-monsoon is in permissible limit of 75 mg/L. Calcium concentrations up to and exceeding 100 mg/l are common in natural sources of water, particularly groundwater (WHO, 2011).
Figure 6 illustrates the spatio-temporal distribution of calcium. Calcium of groundwater is in permissible limit throughout the study area in pre-monsoon season. Calcium concentration is high at Western part of the study area during post monsoon season.
Magnesium-Mg 2+
Magnesium is an important parameter responsible for the hardness of the water (Arjun et al. 2021). Magnesium concentration varies from 3.65 mg/L (Lingagudem) to 35.1 mg/L (Settipeta) in pre-monsoon and 0 mg/L (Lingagudem) to 60.25 mg/L (Pedavegi) in post monsoon periods. Lower concentrations in both seasons are observed at Lingagudem (S17) whereas the maximum concentration i.e. 35.1 mg/L in Settipeta (S26) village of Nidadavolu mandal during pre-monsoon and 60.25 mg/L in Pedavegi (S21) during post-monsoon are observed. Magnesium concentration in 90% of the villages is in permissible limit of 30 mg/L and exceeded in 10% of the villages during both seasons. Magnesium is present in groundwater usually at lower concentrations (WHO, 2011). Deficiency of magnesium causes various risks to humans such as hypertension, vasoconstrictions, atherosclerotic vascular disease, cardiac, eclampsia in pregnant women, acute myocardial in infection and osteoporosis etc. (Mohd Saleem et al., 2016).
Spatial distribution of magnesium concentration is presented in Fig. 7. A negligible patch in SE is with maximum magnesium concentration and the remaining area is in permissible limit during pre-monsoon season. Considerable part in NE and small patches of SW, central area are with maximum concentration of magnesium during post monsoon season.
Total Hardness
The Calcium-based hardness usually predominates in ground water (National Research Council, 1977). Hardness concentration ranges from 60 mg/L (Lingagudem-S17) to 356 mg/L (Jagannadhapuram-S11) in pre-monsoon and 58 mg/L (Dosapadu-S5) to 375 mg/L (Chintalapudi-S1) in post monsoon. The permissible limit of total hardness for human consumption is 300 mg/L (BIS, 2012). In 29 villages (97%), hardness ranges between moderately hard to very hard in both the seasons. Hardness values more than 300 mg/L makes the water hard to drink.
Spatial and temporal concentration of total hardness in the study area is shown in Fig. 8. Groundwater in major portions of the study area is in hard (121–180 mg/L) to very hard (> 180 mg/L) during both the seasons. Groundwater in very few patches of NW is in moderately hard (61–120 mg/L) during both the seasons (McGowan, 2000).
Sulphates- SO 4 2−
Concentration of Sulphates varies from 4.0 mg/L (Lingagudem) to 145 mg/L (Saggonda) and 3.4 mg/L (Gopavaram) to 138 mg/L (Saggonda) with an average concentrations of 47.16 mg/L and 40.87 mg/L during pre-monsoon and post-monsoon periods respectively. Minimum concentration Sulphates i.e. 4.0 mg/L in Lingagudem (S17), 3.4 mg/L in Gopavaram (S10) are observed in pre and post monsoon seasons respectively. Maximum concentration Sulphates i.e. 145 mg/L, 138 mg/L are observed in Saggonda (S25) during both the seasons. Sulphates concentration of groundwater in all villages (100%) is in permissible limit of 150 mg/L during pre and post monsoon seasons. No health-based guideline value has been derived for Sulphate (WHO 2011a; Krishna Kumar et al. 2015).
Spatial and temporal distribution of Sulphates in groundwater is given in Fig. 9. As the figure commended, Sulphates concentration of groundwater in the entire study area are within the permissible limit during both pre and post monsoon seasons.
Chlorides-Cl −
The NaCl, KCl and CaCl2 are the common water dissolving chloride containing salts spread in nature. The weathering cycle absorbs chlorides from several rocks into the water and soil (WHO, 1996). Chlorides are crucial for observing the contamination of ground water by wastewater. Minimum Chloride values of 15.5 mg/L are observed at Gopalapuram (S9) in pre-monsoon season and 23.8 mg/L at Lingagudem (S17) in post monsoon season whereas maximum Chloride values of 679 mg/L and 813 mg/L are observed in Jagannadhapuram (S11) of Pedavegi mandal during pre and post monsoon seasons respectively. Higher concentration of chlorides indicates the higher degree of organic pollution (Munawar, 1970). The average values of the chlorides in the study area are about 166.6 mg/L, 199.8 mg/L during pre-monsoon and post monsoon seasons respectively. Average value of Chlorides in post-monsoon is higher than that of pre-monsoon because of increasing level of water which dissolves more salts from soil (Ramesam 1982; Ballukraya, 1999). Chlorides concentration of groundwater in 15% of villages during pre-monsoon and in 18% of villages during post-monsoon exceeded the permissible limit of 250 mg/L (BIS, 2012).
Figure 10 elaborates the distribution of concentration of Chlorides in the groundwater of study area. SW portion in pre monsoon and SW & NE parts in post monsoon season exceeded the permissible limit of 250 mg/L. The temporal and spatial changes in chloride content of ground water are due to physical process like intercourse with other aquifers of diverse chlorides concentration throughout recharge process (Kumar et al. 2006).
Dissolved Oxygen-DO
The concentration of dissolved oxygen varies between 3.8 mg/L and 9.2 mg/L during pre-monsoon and 3.9 mg/L and 8.9 mg/L during post-monsoon. Minimum concentrations of dissolved oxygen i.e. 3.8 mg/L in Dwaraka Tirumala (S6), 3.9 mg/L in Koppulavarigudem (S13) are noticed in pre and post monsoon seasons respectively. Maximum concentrations of DO i.e. 9.2 mg/L in Settipeta (S26), 8.9 mg/L in Kothapalli (S15) are observed during pre and post monsoon seasons respectively. The DO of groundwater in 36.66% of villages in pre-monsoon and in 50% of villages in post-monsoon exceeded the permissible limit of 5.0 mg/L (BIS, 2012). DO is an important geochemical oxidant and its concentration controls the solubility of many naturally occurring and polyvalent trace elements in ground water (Seth and Austin, 1988).
The spatial and temporal distribution of dissolved oxygen concentration is presented in Fig. 11. Dissolved Oxygen of groundwater is in permissible limit in majority portions of the study area during pre and post monsoon seasons. Groundwater with maximum Dissolved Oxygen concentrations are noticed in SE & SW parts in pre-monsoon, SW part in post monsoon season.
Biological Oxygen Demand - BOD
Biological oxygen demand refers to the amount of oxygen required for the biotic degradation of organic matter in water bodies. The Biological oxygen demand is a parameter to assess the organic load in a water body. This kind of contamination can seriously affect human health (merusonline.com). The BOD of groundwater ranges between 1.6 mg/L to 14.6 mg/L in pre-monsoon and 1.1 mg/L to 6.3 mg/L in post-monsoon seasons respectively. Minimum BOD concentrations i.e. 1.6 mg/L in Raghavapuram (S22) during pre-monsoon and 1.1 mg/L in Munduru (S18) during post monsoon are noticed. Maximum concentrations i.e. 14.6 mg/L in Gopavaram (S10) and 6.3 mg/L in Kothapalli (S15) are observed during pre and post monsoon seasons respectively. BOD of groundwater in 21% villages during pre-monsoon and in 9% villages during post-monsoon exceeded the permissible limit of 5 mg/L (BIS, 2012). High values of BOD indicates the sewage contamination in groundwater.
Distribution of BOD is shown in Fig. 12. BOD of groundwater in SE and SW parts during pre-monsoon and in small patch of SW portion during post monsoon season exceeded the permissible limit.
Water Quality Index-WQI
Water Quality Index is one of the most effective tools to communicate information on the quality of water to the concerned citizens and policymakers (Besma et al. 2018). WQI is highly useful for quality monitoring and management of groundwater. The WQI is a dimensionless number with values ranking between 0 and 100. It is a unique digital rating expression that expresses overall water quality status viz. excellent, good, poor etc. at a certain space and time based on various water quality parameters (Arjun et al. 2021). It is an important indicator for assessing groundwater quality and its suitability for drinking purpose (Boateng et al, 2016). Detailed water quality index status in pre-monsoon and post-monsoon seasons for each village is presented in the Table 5. The water quality index of 47.91 (Table 6) indicates the overall water quality during pre-monsoon period is good in condition and certainly fit for consumption whereas WQI of 57.67 in post-monsoon period indicates the poor quality of water (Table 7). Similar observations are furnished by Chaterjee and Raziuddin (2002, 2007) and Srivastava et al. (2007). This poor quality of water needs a proper disinfection method for drinking purpose.
Table 5
Water Quality Status in the Villages of Study Area
Sampling Village | Pre-Monsoon | Post-Monsoon |
WQI | Status | WQI | Status |
Chintalapudi (S1) | 57.16 | Poor | 27.33 | Good |
Denduluru (S2) | 28.39 | Good | 57.79 | Poor |
Dondapudi (S3) | 82.10 | Very poor | 56.65 | Poor |
Dorasanipadu (S4) | 53.39 | Poor | 51.78 | Poor |
Dosapadu (S5) | 17.45 | Excellent | 4.73 | Excellent |
Dwaraka Tirumala (S6) | 50.33 | Poor | 27.89 | Good |
Erraguntapalli (S7) | 42.34 | Good | 39.76 | Good |
G. Kothapalli (S8) | 74.43 | Poor | 39.03 | Good |
Gopalapuram (S9) | 40.26 | Good | 37.20 | Good |
Gopavaram (S10) | 19.97 | Excellent | 33.33 | Good |
Jagannadhapuram (S11) | 108.56 | Unfit | 63.15 | Poor |
Komathikunta (S12) | 31.30 | Good | 30.92 | Good |
Koppulavarigudem (S13) | 71.84 | Poor | 50.02 | Good |
Korumamidi (S14) | 32.61 | Good | 67.30 | Poor |
Kothapalli (S15) | 53.19 | Poor | 82.88 | Very Poor |
Kovvurpadu (S16) | 84.56 | Very poor | 56.79 | Poor |
Lingagudem (S17) | 43.10 | Good | 21.91 | Excellent |
Munduru (S18) | 85.09 | Very poor | 52.98 | Poor |
Nidadavolu (S19) | 58.09 | Poor | 43.90 | Good |
Pangidigudem (S20) | 53.63 | Poor | 33.72 | Good |
Pedavegi (S21) | 86.46 | Very poor | 44.29 | Good |
Raghavapuram (S22) | 44.99 | Good | 40.59 | Good |
Rallakunta (S23) | 19.90 | Excellent | 51.36 | Poor |
Rangapalem (S24) | 8.40 | Excellent | 14.87 | Excellent |
Saggonda (S25) | 48.54 | Good | 39.54 | Good |
Settipeta (S26) | 54.22 | Poor | 48.91 | Good |
Somavarappadu (S27) | 46.78 | Good | 37.59 | Good |
Tadimalla (S28) | 24.67 | Excellent | 24.58 | Excellent |
Vegavaram (S29) | 35.48 | Good | 49.93 | Good |
Vijayarai (S30) | 81.88 | Very poor | 54.48 | Poor |
Table 6
Water Quality Index in Pre-monsoon season
Parameter | Observed value | Standard values (Sn) | Unit weight (Wn) | Quality rating(Qn) | WnQn |
pH | 7.39 | 6.5–8.5 | 0.2190 | 26 | 5.694 |
TDS | 735.9 | 500 | 0.0037 | 147.18 | 0.545 |
TA | 314.26 | 120 | 0.0155 | 261.88 | 4.059 |
TH | 187.83 | 300 | 0.0062 | 62.61 | 0.388 |
Ca+ 2 | 42.50 | 75 | 0.025 | 56.66 | 1.417 |
Mg+ 2 | 17.66 | 30 | 0.061 | 58.866 | 3.591 |
Cl− | 166.69 | 250 | 0.0074 | 66.67 | 0.493 |
| | | ∑Wn= 0.3378 | ∑Qn= 679.88 | ∑WnQn= 16.19 |
Water Quality Index = ∑WnQn / ∑Wn = 47.91 |
All values are in mg/L except pH and EC (µS/cm).
Table 7
Water Quality Index in Post-monsoon season
Parameter | Observed value | Standard values (Sn) | Unit weight (Wn) | Quality rating(Qn) | WnQn |
pH | 7.55 | 6.5–8.5 | 0.2190 | 36.66 | 8.03 |
TDS | 739.3 | 500 | 0.0037 | 147.86 | 0.547 |
TA | 293.16 | 120 | 0.0155 | 244.3 | 3.787 |
TH | 195.7 | 300 | 0.0062 | 65.23 | 0.404 |
Ca+ 2 | 45.84 | 75 | 0.025 | 61.12 | 1.528 |
Mg+ 2 | 22.60 | 30 | 0.061 | 75.33 | 4.595 |
Cl− | 199.61 | 250 | 0.0074 | 79.84 | 0.591 |
| | | ∑Wn= 0.3378 | ∑Qn= 710.35 | ∑WnQn= 19.48 |
Water Quality Index = ∑WnQn / ∑Wn = 57.67 |
All values are in mg/L except pH and EC (µS/cm)
The water quality index rating in each village is much better during post-monsoon with respect to trend line. The blue dotted trend line represents increase in WQI ratings during pre-monsoon period, whereas the green dotted line also represents increasing trend during post monsoon season with better WQI ratings as compared to pre-monsoon (Fig. 13). WQI depicts the composite impact of different water quality parameters and communicates water quality information to the public and legislative policy-makers to shape strong policy and implement the water quality programs (Kalavathy et al. 2011).
The status of Water Quality Index in the villages of study area during two seasons along with number of villages and its percentage is shown in Table 8. The distribution of WQI status of villages during pre and post-monsoon seasons is shown in Fig. 14.
Table 8
WQI Status of groundwater in the villages during Pre and Post-monsoon Seasons
Pre-monsoon | | Post-monsoon |
WQI Status | No. of Villages | % | WQI Status | No. of Villages | % |
Excellent | 5 | 16.66 | Excellent | 4 | 13.33 |
Good | 10 | 33.33 | Good | 16 | 53.33 |
Poor | 9 | 30.00 | Poor | 9 | 30.00 |
Very poor | 5 | 16.66 | Very poor | 1 | 3.33 |
Unfit | 1 | 3.33 | Unfit | 0 | 0.0 |
The water quality index (WQI) map has been prepared using ArcGIS 10.1 on the basis of the selectively chosen quality parameters to decipher the various quality classes viz. excellent, good, poor, very poor and unsuitable at each sampling station for drinking purpose (Arjun et al. 2021). Spatial and temporal distribution of WQI in the study area is presented in Fig. 15. The WQI Map of the study area indicates that major portion is having poor (51–75) quality of ground water while very small pockets are with very poor (76–100) and unfit (> 100) quality of water in both the seasons. Excellent (< 25) to good (26–50) quality ground water is prevailing in NW and SE parts during pre-monsoon and in SW part during post monsoon season. There is a noticeable change in WQI of groundwater in SE part during post monsoon season.