Spatial distribution and hydrogeochemical evaluations of groundwater and its suitability for drinking and irrigation purposes in kaligonj upazila of satkhira district of Bangladesh

Abstract

Groundwater is a significant water resource for drinking and irrigation in Satkhira district, Bangladesh. The depletion of groundwater resources and deterioration in its quality are the results of the confluence of factors such as industrialization, intensive irrigation, and rapid population growth. For this reason, this study focused on the evaluation of tubewell water of six unions of Kaligonj upazila in Satkhira district, which is situated in the coastal southwest part of Bangladesh. Major and trace elemental concentrations were assimilated into positive matrix factorization (PMF) to identify potential sources and their respective contributions. Principal component analysis (PCA) revealed that groundwater salinization and manmade activities were the primary causes of heavy metals in the coastal groundwater. Its average pH value was found to be 7.5, while Dissolved oxygen, Total dissolved solids, salinity, and conductivity, with values ranging from 1.18 to 7.38 mg/L, 0.5-4.88 g/L, 0.4-5%, and 0.95 to 8.56 mS/cm, respectively. The total hardness average value was 561.7 mg/L, classified into the very hard water categories, which is why 90% of the tubewell water samples were unfit for household purposes. All samples had an excessive level of arsenic present. The iron concentration of fifteen (15) samples crossed the standard limit according to WHO 2011 value. Around 63% of the samples were of the Na⁺-K⁺-Cl^--SO₄^2- type, and about 72% were sodium-potassium and alkali types. 98% of samples were covered in chloride and bicarbonate. The findings showed that 45.83% of the groundwater samples had negative Chloroalkaline index (CAIs), while 54.16% had positive. The permeability index (PI) was an average of 73%, and residual sodium carbonate (RSC) averaged 260.2 mg/L, and the findings clearly showed that 80% of the samples weren't appropriate for irrigation. According to the sodium adsorption ratio (SAR) value, 65% of the samples fell into the unsuitable category. These calculations indicated a high overall salinity hazard in the study area, which may be caused by the intrusion of sea water given that the study area is close to the coastal region. Findings compared to standards revealed that the majority of the samples were deemed unfit for drinking and irrigation purposes. Hence, additional attention must be paid to this area to ensure the availability of drinkable water and to preserve sustainable farming practices.

Keywords: Hydrochemistry; Irrigation suitability; Multivariate statistical analysis; Salinity; Spatial distribution; Water quality index.

Graphical abstract

Fig. 1

Sampling sites based on Geographic Information System (GIS).

Fig. 2

Pie diagram to represent the contribution (%) of different cations (A) and anions (B) of the study area.

Fig. 3

Principal component analysis (PCA) scree plot (a) and biplot (b) based on the correlation matrix.

Fig. 4

Dendrogram for all the physio-chemical parameters of the water samples.

Fig. 5

PMF factor profiles for identifying sources by bars (left y-axis) and the percentage contributions (right y-axis).

Fig. 6

Piper diagram of the samples in the studied region [(1) SO₄²⁻ type, (2) Ca²⁺-Mg²⁺-SO₄^2--Cl^- type, (3) Ca²⁺-Mg²⁺- HCO₃⁻ type, (4) Na⁺- HCO₃⁻ type, (A) Na⁺- K⁺ type, (B) Mg²⁺ type, (C) No-dominance, (D) Ca²⁺ type, (E) No-dominance, (F) SO₄²⁻ type, (G) Cl⁻ type, and (H) HCO₃⁻ type].

Fig. 7

Ion scatter diagram (a–h) showing relationships among major ions in the groundwater (STW) where (a) Na⁺ vs total cations (b) Na⁺ + K⁺ vs total cations (c) Ca²⁺ + Mg²⁺ vs total cations (d) Cl⁻ + SO₄²⁻ vs total anions (e) Cl⁻ vs total anions (f) HCO₃⁻ vs total anions (g) Ca²⁺ + Mg²⁺ vs HCO₃⁻and (h) Ca²⁺ + Mg²⁺ vs HCO₃⁻ + SO₄²⁻.

Fig. 7

Ion scatter diagram (a–h) showing relationships among major ions in the groundwater (STW) where (a) Na⁺ vs total cations (b) Na⁺ + K⁺ vs total cations (c) Ca²⁺ + Mg²⁺ vs total cations (d) Cl⁻ + SO₄²⁻ vs total anions (e) Cl⁻ vs total anions (f) HCO₃⁻ vs total anions (g) Ca²⁺ + Mg²⁺ vs HCO₃⁻and (h) Ca²⁺ + Mg²⁺ vs HCO₃⁻ + SO₄²⁻.

Fig. 8

The Gibb's Ratios of (a) TDS versus cations and (b) TDS versus anions.

Fig. 9

EC, TDS, SAR, % Na⁺, TH, KR versus concentration of Groundwater in different locations.

Fig. 10

Total ion concentrations versus Permeability index (PI).

Fig. 11

Spatial distribution maps (a–n) for selected parameters while (a) pH, (b) TDS, (c) EC, (d) Salinity, (e) Alkalinity, (f) As, (g) Na⁺, (h) K⁺, (i) Ca²⁺, (j) Mg²⁺, (k) Cl⁻, (l) HCO₃⁻, (m) % Na⁺ and (n) SAR.

Fig. 11

Spatial distribution maps (a–n) for selected parameters while (a) pH, (b) TDS, (c) EC, (d) Salinity, (e) Alkalinity, (f) As, (g) Na⁺, (h) K⁺, (i) Ca²⁺, (j) Mg²⁺, (k) Cl⁻, (l) HCO₃⁻, (m) % Na⁺ and (n) SAR.

Fig. 11

Spatial distribution maps (a–n) for selected parameters while (a) pH, (b) TDS, (c) EC, (d) Salinity, (e) Alkalinity, (f) As, (g) Na⁺, (h) K⁺, (i) Ca²⁺, (j) Mg²⁺, (k) Cl⁻, (l) HCO₃⁻, (m) % Na⁺ and (n) SAR.

Fig. 11

Spatial distribution maps (a–n) for selected parameters while (a) pH, (b) TDS, (c) EC, (d) Salinity, (e) Alkalinity, (f) As, (g) Na⁺, (h) K⁺, (i) Ca²⁺, (j) Mg²⁺, (k) Cl⁻, (l) HCO₃⁻, (m) % Na⁺ and (n) SAR.