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Groundwater quality assessment in Borana

of 0.05 mg/L for total chromium in drinking water. (1 < GPI < 1.5), “Moderate pollution” (1.5 < GPI < 2.0),
However, it is important to note that these findings “High pollution” (2.0 < GPI < 2.5), and “Very high
contrast with a study by Gebresilasie et al., which pollution” (GPI > 2.5), as outlined by Sanad et al.
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reported that chromium levels in all hand-dug well The calculated GPI values, presented in Table 6, ranged
water samples from Kafta Humera District, Ethiopia, from 0.190 to 1.44, categorizing the water quality
were below the detection limit (DL) of the method used. into two distinct groups: “Insignificant pollution” and
These differing results underscore the variations in Cr⁶⁺ “Low pollution”. The results showed that 80% of the
concentrations across different geographical locations 10 ground drinking water sources investigated (Y1, Y2,
and water sources. Y3, Y4, E1, E2, S1, and S2) were in the “Insignificant
pollution” category, indicating excellent suitability for
3.1.13. Mn²⁺ levels drinking. In contrast, 20% of the sources, specifically
Analysis of water samples revealed that the D1 and D2, were classified as having “Low pollution”.
concentration of Mn²⁺ ranged from the method DL to Notably, the highest GPI value of 1.44 was recorded at
0.60 mg/L (Table 5). Of the ten samples examined, five D1 (Table 6).
(50%) showed detectable levels of Mn²⁺. However, the
Mn²⁺ concentrations in these samples were significantly 3.3. NPI
lower—from 1.3 to 20 times below the WHO health- In this study, NPI values ranged from −0.89 to 4.04,
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based recommended guideline value of 0.4 mg/L for with an average of 0.658. The NPI is a tool used to
drinking water. Among the samples, only the water assess water pollution caused by elevated nitrate
collected from the D1 sampling site exhibited an Mn²⁺ concentrations. The NPI values classify water quality
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concentration of 0.60 mg/L, which exceeded the health- as follows: “Clean (unpolluted)” (NPI < 0.0), “Low
based recommendation value. The Mn²⁺ concentrations pollution” (0.0 < NPI < 1.0), “Moderate pollution”
measured in this study were lower compared to those (1.0 < NPI < 2.0), “High pollution” (2.0 < NPI < 3.0),
reported by Garoma et al. but higher than those and “Very high pollution” (NPI > 3.0), as outlined by
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reported by Gebresilasie et al. in Ethiopia. Al-Aizari et al. Analysis of the NPI values (Table 6)
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reveals that samples from sites Y2, Y4, and D1
3.1.14. Total Fe exhibited values of 1.97, 1.93, and 1.95, respectively,
The water samples examined in this study showed total categorizing them as experiencing Moderate Pollution,
Fe concentrations ranging from 0.02 to 0.50 mg/L. which accounts for 30% of the total samples. Five sites
Among the ten samples analyzed, only one (S2 sampling (Y3, E1, E2, S1, and S2), representing 50% of the total,
site) exhibited a total iron concentration of 0.50 mg/L, were classified as “Clean (unpolluted)”. The D2 site
exceeding the WHO recommended taste threshold for was categorized as having “Low pollution”. Notably,
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iron in drinking water, which is set at 0.3 mg/L. The total the Y1 site was classified as experiencing “Very high
iron concentrations observed in this study were lower pollution”, indicating a significant and concerning level
compared to findings from various regions in Ethiopia, of nitrate contamination at this location.
as reported by Shigut et al., Gebresilasie et al. , and
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Lewoyehu. The variations in iron levels may be 3.4. WQI
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attributed to factors such as geological characteristics, The WQI offers a detailed assessment of the quality of
water sources, agricultural practices, and other local surface and groundwater for a wide range of domestic
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influences on water quality. uses. As a rule, the WQI is utilized to appraise the
suitability of groundwater for drinking purposes in
3.2. GPI accordance with established the WHO standards. 13
According to Sanad et al., the GPI is used as a The WQI values are classified as follows: “Unsuitable
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comprehensive metric that accounts for the combined for drinking” (WQI ≥300), “Very poor” (200 < WQI
effects of various chemical factors on groundwater < 300), “Poor” (100 < WQI < 200), “Good” (50 < WQI
quality, offering a single value that reflects the overall < 100), and “Excellent” (WQI < 50). These classifications
level of groundwater pollution. are based on the work of Elssaidi et al. Table 6 presents
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The GPI value effectively reflects the degree the WQI values for all groundwater samples analyzed,
of groundwater contamination. The GPI values as calculated using Equations I, VI, VII, and VIII. The
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classify water quality into the following categories: WQI values, as shown in Table 6, ranged from 19.4 to
“Insignificant pollution” (GPI < 1), “Low pollution” 143.6 across the 10 sampling sites, with an average value

Volume 22 Issue 1 (2025) 109 doi: 10.36922/AJWEP025040023