Groundwater quality and community health risk in Lalitpur Metropolitan City, Nepal – a geospatial analysis

Figures & data

Figure 1. Study area with groundwater sample sites and the land-use classes.

Figure 2. Geological map of Lalitpur Metropolitan City showing rock formations and groundwater sampling points.

Table 1. Weights assigned to groundwater parameters for drinking purpose.

Parameter	Unit	Categories	Weight assigned	Parameter	Unit	Categories	Weight assigned
pH		≤6.5	1	Cl-	mg/L	<100	1
		6.6-8.5	2			100-250	2
		>8.5	3			> 250	3
TDS	mg/L	≤500	1	HCO3^-	mg/L	≤150	1
		501-1000	2			151-300	2
		>1000	3			>300	3
EC	μS/cm	≤1000	1	NO3^-	mg/L	≤11.2	1
		1001-1500	2			11.3-50	2
		>1500	3			>50	3
Na^+	mg/L	≤100	1	NH4^+	mg/L	≤1.2	1
		101-200	2			1.3-1.5	2
		>200	3			>1.5	3
K^+	mg/L	≤50	1	Fe	mg/L	≤0.05	1
		51-100	2			0.06-0.3	2
		>100	3			>0.3	3
Ca^2+	mg/L	≤100	1	PO4^3-	mg/L	≤0.5	1
		101-200	2			0.6-1.0	2
		>200	3			>1.0	3
Mg^2+	mg/L	≤50	1	SO4^2-	mg/L	≤ 125	1
		51-100	2			126-250	2
		>100	3			>250	3
TH	mg/L	≤250	1	TC	MPN	< 1	1
		251-500	2			≥ 1	2
		>500	3

Table 2. Groundwater quality zoning for drinking through classification of weightage.

Total weightage	Quality classified
16	Very good
17–24	Good
25–32	Moderate
33–40	Bad
40–47	Very bad

Table 3. Weights assigned to groundwater parameters for irrigation purpose.

Classification patterns	Categories	Ranges	Weight	Winter samples	Post monsoon sample
Salinity hazard (TDS)	Excellent	<175	1	2	2
	Good	175–525	2	22	24
	Permissible	525–1400	3	11	9
	Doubtful	1400–2100	4
	Unsuitable	>2100	5
Chloride (mg/L)	Excellent	<135	1	28	32
	Good	136–355	2	7	3
	Fair	>355	3
Sodium absorption rate (SAR)	Excellent	0–10	1	35	35
	Good	10–18	2
	Fair	18–26	3
	Poor	>26	4
Sodium percentage (Na %)	Excellent	0–20	1	20	13
	Good	20–40	2	14	20
	Permissible	40–60	3	1	2
	Doubtful	60–80	4
	Unsuitable	>80	5
Permeability index (PI)	Class I	>75	1
	Class II	25–75	2	6	2
	Class III	<25	3	29	33
Magnesium adsorption ratio (MAR)	Suitable	<50	1	35	33
	Unsuitable	>50	2		2

Table 4. Groundwater quality zoning map for irrigation.

Total weightage	Quality classified
Up to 9	Very good
10	Good
11	Moderate
12	Bad
>12	Very bad

Table 5. Statistics of groundwater chemistry in Lalitpur Metropolitan City.

Parameters		pH	TDS	EC	Na^+	K^+	Ca^2+	Mg^2+	TH	Clˉ	HCO3ˉ	NO3ˉ	NH^4+	Fe	PO4^3-	SO4^2-	TC
Unit			mg/l	μS/cm	mg/l	mg/l	mg/l	mg/l	mg/l	mg/l	mg/l	mg/l	mg/l	mg/l	mg/l	mg/l	MPN/100 ml
Minimum	W	8.38	137	276	33.2	0.84	64	2.4	100	22.72	20	0.04	< 0.1	< 0.01	0.23	5.52	56
	PM	7.28	112	226	13.9	0.27	38.47	2.4	80	20.45	15	0.04	< 0.1	< 0.01	0.10	4.42	68
Maximum	W	9.54	1063	2127	70.3	41.5	478	61.68	612	241.4	450	0.14	0.99	10.16	3.58	77.7	254
	PM	9.54	1051	2021	79.8	50.3	389	81.87	485	220.1	105	0.3	0.46	4.19	3.65	63.22	315
Mean	W	9.15	491.71	983.63	53.65	16.21	218.4	22.21	306	103.71	148.29	0.06	0.16	1.02	0.78	21.02	123.09
	PM	7.97	466.35	913.63	55.85	15.87	158.93	22.14	253.03	80.87	39.29	0.07	0.13	0.42	0.45	16.47	151.48
SD	W	0.41	217.69	436.53	10.27	13.08	105.62	11.3	126.55	52.55	87.04	0.02	0.17	2.42	0.86	20.93	53.66
	PM	0.44	198.15	393.5	17.9	13.63	83.3	18.18	97.14	45.767	21.73	0.05	0.08	0.97	0.64	15.69	67.41
CV	W	4.48	44.27	44.38	19.14	80.69	48.36	50.87	41.36	50.67	58.7	33.07	105	236.48	109.64	99.54	43.6
	PM	5.56	42.49	43.07	32.05	85.87	52.42	85.32	38.39	56.59	55.32	79.4	60.02	230.28	140.71	95.24	44.5
NDWQS (2008)	Range	6.5 − 8.5	1000	1500	----	----	200	----	500	250	----	11.2	1.2	0.3	----	250	95% in sample
WHO (2011)	Range	6.5 − 8.5	1000	1500	200	100	100	50	500	250	300*	50	1.5	-----	1	250	95% in sample

Note: W winter, PM post-monsoon

Table 6. Association among various chemical parameters in the groundwater of Lalitpur Metropolitan City in Winter and Post-monsoon as revealed by the Pearson moment correlation coefficient.

Winter samples			Post-monsoon samples
Parameters		R	Parameters		R
pH	TC	−0.56**	pH	TC	−0.53**
EC	TDS	1.00**	EC	TDS	0.99**
TH	Ca^2+	0.92**	TH	Ca^2+	0.66**
TH	Mg^2+	0.57**	TH	Mg^2+	0.55**
Fe	NH4^+	0.62**	Fe	NH4^+	0.64**
Fe	Mg^2+	0.38*	pH	SO4^2-	0.035*
Fe	NO3^-	0.68**	TH	Na^+	0.42*
SO4^2-	K^+	0.36*	Cl^-	K^+	0.48**
Mg^2+	K^+	−0.34*	Cl^-	Mg^2+	0.39*
NH4^+	Mg^2+	0.49**	NO3^-	K^+	0.45**
NH4^+	TH	0.39*	HCO3^-	TDS	0.57**
NH4^+	NO3^-	0.45**	HCO3^-	EC	0.57**
			HCO3^-	Na^+	0.34*
			TC	Cl^-	0.43**
			TC	SO4^2-	−0.34*

Note: ^**Correlation is significant at the 0.01 level (2-tailed).

* Correlation is significant at the 0.05 level (2-tailed).

Figure 3. Spatial distribution map of pH of study area.

Figure 4. Spatial distribution map of Total Dissolved Solids of study area.

Figure 5. Spatial distribution map of Electrical Conductivity of study area.

Figure 6. Spatial distribution map of Total Hardness of study area.

Figure 7. Spatial distribution map of Calcium ion of study area.

Figure 8. Spatial distribution map of Magnesium ion of study area.

Figure 9. Spatial distribution map of Sodium of study area.

Figure 10. Spatial distribution map of Potassium of study area.

Figure 11. Spatial distribution map of Ammonium in LMC.

Figure 12. Spatial distribution of Bicarbonate in the groundwater of LMC.

Figure 13. Spatial distribution of Chloride in the groundwater of LMC.

Figure 14. Spatial distribution of Sulphate in the groundwater of LMC.

Figure 15. Spatial variation of Nitrate in the groundwater of LMC.

Figure 16. Spatial distribution map of Phosphate of study area.

Figure 17. Spatial variation of Iron in the groundwater of LMC.

Figure 18. Spatial distribution of total coliform in the groundwater of LMC.

Figure 19. Groundwater quality for drinking in the municipality wards of LMC with population density.

Figure 20. Spatial and seasonal variations of contamination level in the groundwater at the sampling sites (wells).

Table 7. Contamination level (C-level) of groundwater in the municipality wards of Lalitpur Metropolitan City during winter and post-monsoon as determined by the contamination index (C_d).

Sample No.	Winter		Post-monsoon
	Cd	C-level	Cd	C-level
W1	< 0.1	Low	< 0.1	Low
W2	< 0.1	Low	< 0.1	Low
W3	0.5	Low	0.2	Low
W4	0.4	Low	0.4	Low
W5	29.3	High	0.1	Low
W6	< 0.1	Low	< 0.1	Low
W7	33.8	High	13.0	High
W8	0.2	Low	< 0.1	Low
W9	0.1	Low	< 0.1	Low
W10	3.0	Medium	2.3	Medium
W11	0.1	Low	< 0.1	Low
W12	6.3	High	0.4	Low
W13	0.1	Low	0.3	Low
W14	2.7	Medium	< 0.1	Low
W15	1.8	Medium	0.5	Low
W16	1.0	Medium	0.6	Low
W17	0.1	Low	< 0.1	Low
W18	2.7	Medium	2.6	Medium
W19	0.2	Low	< 0.1	Low
W20	0.1	Low	< 0.1	Low
W21	7.2	High	3.2	High
W22	0.1	Low	< 0.1	Low
W23	0.1	Low	0.6	Low
W24	6.1	High	0.4	Low
W25	18.9	High	7.3	High
W26	0.2	Low	< 0.1	Low
W27	2.7	Medium	2.6	Medium
W28	3.6	High	1.1	Medium
W29	0.5	Medium	0.1	Low
W30	0.7	Medium	< 0.1	Low
W31	0.6	Medium	0.1	Low
W35	< 0.1	Low	< 0.1	Low

Figure 21. A: Groundwater contamination level and population density in the municipality wards of LMC. B. Ward wise total population in the LMC.

Table 8. Municipality ward-wise projected population of Lalitpur Metropolitan City in the year 2021 (based on population growth rate in Nepal by the World Bank).

Municipality ward	Well No.	Households	Population in 2011	Population in 2021*	Percent of total population
1	W10	2221	8434	9249	2.96
2	W25	4839	19061	20903	6.69
3	W24	3528	14082	15443	4.94
4	W17, W34, W23	3913	15367	16852	5.39
5	W29	1516	6404	7023	2.25
6	W8	1563	6780	7435	2.38
7	W6	1839	7849	8618	2.75
8	W9	2816	11400	12502	4
9	W13	3484	13908	15252	4.88
10	W11	1729	6554	7187	2.3
11	W12	2460	10109	11086	3.55
12	W7	2352	10349	11349	3.63
13	W18	3772	14867	16304	5.22
14	W28	5438	21232	23284	7.45
15	W31, W30	3480	13858	15197	4.86
16	W14	2058	10139	11119	3.56
17	W5	2678	10644	11672	3.74
18	W22	2007	8146	8933	2.86
19	W15	1774	7385	8099	2.59
20	W16	3121	12380	13576	4.35
21	W20, W33	1056	4927	5403	1.73
22	W32, W19	1304	5966	6542	2.09
23	W2	1854	7002	7679	2.46
24	W1, W35	1324	5676	6224	1.99
25	W21	2996	11575	12693	4.06
26	W27	1377	5813	6375	2.04
27	W26	1020	4279	4692	1.5
28	W4	1667	6577	7213	2.31
29	W3	1070	4159	4561	1.46
Total	35	70056	284922	312464	100

(Source: CBS, 2012)

* Projected population

Figure 22. Groundwater quality of samples for irrigation based on TDS concentration.

Figure 23. Groundwater quality for irrigation based on chloride concentration.

Figure 24. Sodium Adsorption Ratio (SAR) in winter and post-monsoon samples.

Figure 25. Spatial distribution map of Sodium percentage.

Figure 26. Spatial distribution map of Permeability Index.

Figure 27. Magnesium Adsorption Ratio (MAR) in winter and post-monsoon samples.

Figure 28. Groundwater quality for irrigation in the municipality wards of LMC.

Figure 29. Scatter plots showing variations of the principal cations versus TDS in winter (a), and during the post-monsoon (b).

Figure 30. Scatter plots showing variations of the principal anions versus TDS in winter (a), and during the post-monsoon (b).

Figure 31. Scatter plot showing seasonal variation of Na⁺ versus Cl^ˉ in the groundwater.

Figure 32. Scatter plot for seasonal variation of HCO₃^ˉ versus Na⁺ in the groundwater.

Figure 33. Scatter plot showing seasonal variation of Ca/Mg molar ratio.

Figure 34. Scatter plot of (Ca²⁺ + Mg²⁺) versus (HCO₃^ˉ + SO₄^2ˉ) depicting seasonal variation in silicate weathering and carbonate weathering.

World Health Organization (WHO). 2011. Guidelines for drinking water. 4th ed. Geneva: World Health Organization.

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Data availability statement

All the datasets used to support the findings of this study are available from the corresponding author upon request.