Water Quality Index for the Evaluation of Water Quality from Different Source: A Case Study of Lafia
- Ogah Halimat
- Abdullahi Zainab Suleiman.
- Yusuf Gabriel
- 1852-1859
- Jun 21, 2025
- Public Health
Water Quality Index for the Evaluation of Water Quality from Different Source: A Case Study of Lafia
* Ogah Halimat, Abdullahi Zainab Suleiman., Yusuf Gabriel
Dept of Geography Federal University of Lafia, Nasarawa State
*Corresponding Author
DOI: https://doi.org/10.51244/IJRSI.2025.120500170
Received: 24 April 2025; Accepted: 08 May 2025; Published: 21 June 2025
ABSTRACT
Water must be significantly free from dissolved solid, plant and animal waste and bacterial contaminants in order to be safe for human use. The Water Quality Index method was used to assess the water quality of several water sources (well and borehole) in the Lafia district of Nasarawa state. In order to determine if groundwater in the study region is suitable for residential use, the current inquiry was conducted to calculate the Water Quality Index. Numerous physico-chemical and biological data, including pH, chloride, sulphate, nitrate, calcium, feacal streptococcus, total coliform, and magnesium, were used to calculate WQI. The computed WQI result, which falls into the Good (Acceptable), Bad, and Very Bad (Rejected) classes, varies from 0 to 58.9 in one instance and from 0 to 98.0 in another, based on the empirical formulas for the groundwater samples. A distinct index range was produced by each parameter. Findings from the research revealed that all wells & borehole sampled have high faecal streptococcus above the recommended level for drinking water, thereby requiring the need for urgent public health intervention
Keywords: water quality index, physical, chemical and biological parameters.
INTRODUCTION
All living things need water, which is a vital natural resource. Humans, however, utilize water more than any other living thing for drinking, personal, household, industrial, and recreational purposes [1]. Energy generation, agriculture, and industry all depend on clean and consistent water supply. Water is essential to every environment and community on Earth for daily existence, sanitation, and hygiene. The demand for potable water for residential, agricultural, and industrial applications has rapidly expanded due to population growth.
The consequence effect of the circumstance is that some residents find other ways to get water, such as drilling wells or boreholes, while others who cannot afford it get water from water vendors that may not be of high quality [13]. Unsafe water is a global public health problem, placing persons at risk, plethora of diarrheal and other infections as well as chemical intoxication [6]. The majority of freshwater bodies worldwide are becoming contaminated, which reduces the water’s potability [3].
Water quality is the term used to describe the physical, chemical and biological parameters of the water relating to its suitability for particular use [16]. Water Quality Index is an important technique for demarcating groundwater quality and its suitability for drinking purposes [2].
WQI is defined by [17] as an assessment of the physical, chemical, and biological characteristics of water in relation to its natural quality, human impacts, and intended uses. A mathematical formula is used to rate the water quality, thereby establishing whether the water is suitable for drinking and other household purposes.
According to [9], Horton originally created the index in 1965 to gauge the quality of water using the ten most often utilized water characteristics. Later, several specialists made changes to the approach. These indices made use of different types and numbers of water quality parameters. Each parameter has a weight assigned to it based on its own standards, which shows how important the parameter is and how it affects the index.
Based on a few water factors, the index gives a single value that represents the general quality of the water at a specific location and time. WQI turns a complicated dataset into information that is simply comprehensible and useful. The water quality grading system used in the WQI denotes how suitable water is for drinking [11]. The single value output of this index, derived from several parameters provides important information about water quality that is easily interpretable, even by lay people.
WQI, which synthesizes various available water quality data into an easily understandable format, provides a way to summarize overall water quality conditions that can be clearly communicated to policy makers [10]. [12]worked on the groundwater quality index using GIS, where they calculated the normalized sub-indices and then ranked them. Their study area was a few km², and the parameters they used only chemical parameters containing ions. The final index represented in percentages rather than values.
Furthermore, WQI makes it easier to compare various sample locations and occasions [5]. Therefore, a continuous periodical monitoring of water quality is necessary so that appropriate steps may be taken for water resource management practices [7]. The development of WQI is the main emphasis of this study, which is subsequently used to evaluate whether groundwater is suitable for residential use.
Description of the Study Area
Lafia is situated in central Nigeria. It is one of the 13 local government districts in the state of Nasarawa and serves as its capital. Lafia is located between Latitude 8029’30″N and Longitude 8031’0″E on a global scale [14]. It spans an area of around 18 km from north to south and 14 km from east to west, and it takes up about 258 km². According to [15], there are around 509,300 people living in the town. The town’s geography is composed of gently sloping terrain that is typically below 400 meters, with a number of slopes down to the larger Benue plain.
The soil is predominantly sandy loam [8]. The vegetation type is guinea savanna, which is distinguished by its irregular canopy. A wet season and a dry season are its two distinct seasons [4]. Figure 1 depicts the location of Nasarawa on the maps of Nigeria and lafia on the map of Nasarawa.
Figure 1: Map showing the study area
Source: digitize and map out by Zainab.
MATERIALS AND METHODS
In order to see the suitability of groundwater for domestic use in Lafia district, we therefore make use of the water quality index. WQI is considered as the most effective method of measuring water quality. A number of water quality parameters are included in a mathematical equation to rate water quality, determining the suitability of water for drinking and other domestic use. The primary data of all physico-chemical and biological parameters were collected and delivered within 48hrs of collection to federal ministry of water resources for laboratory analysis of the sample. Two sample were collected each, from different sources in the following rural areas of lafia (gimara, bukan koto, tudun amba and agyaragu tofa). Making a total of eight (8) sample, 4 from boreholes and 4 from hand dug wells. GPS was used to record the locations of the various water spots. The data generated were used to calculate water quality index (WQI). The relative weighted method was used for the calculation of the index value in this study.
RESULTS
Figure: 2. Map of the study area showing sampling points
Source: digitize and map out by Zainab.
Table 1: GPS location of the samples
| No of sample | Ground position system (GPS) |
| Borehole 1 | 08029’810”N 008033’409”E |
| Borehole 2 | 08027’826”N 008034’287”E |
| Borehole 3 | 08028’883”N 008030’425”E |
| Borehole 4 | 08028’236”N 0080,32.123”E |
| Well 1 | 08029’475”N 008033’341”E |
| Well 2 | 08027’710”N 008034’289”E |
| Well 3 | 08028’406”N 008030’355”E |
| Well 4 | 08028’238”N 008032’120”E |
Table 2: Statistical summary of physico-chemical and biological parameters of samples in the study area
| S/N | PARAMETERS | Bh1 | Bh2 | Bh3 | Bh4 | W1 | W2 | W3 | W4 | NSDWQ/WHO |
| 1 | pH | 7.69 | 7.85 | 7.93 | 7.73 | 7.62 | 8.25 | 8.34 | 7.23 | 6.5 – 8.5 |
| 2 | TDS | 742 | 758 | 683 | 353 | 459 | 291 | 283 | 351 | 500mg/l |
| 3 | Calcium | 18.1 | 22.0 | 16.0 | 15.2 | 31.3 | 63.4 | 29.4 | 12.8 | N/A |
| 4 | Nitrate | 23.8 | 40.3 | 29.4 | 52.0 | 57.1 | 18.0 | 38.0 | 39.0 | 50 |
| 5 | Turbidity | 1.5 | 2.0 | 1.9 | 3.0 | 3.9 | 4.0 | 2.3 | 3.8 | 5NTU |
| 6 | Sulphate (mg/L) | 59.0 | 26.0 | 68.0 | 43.0 | 70.0 | 99.3 | 43.2 | 63.4 | 100 |
| 7 | Chloride (mg/L) | 41.3 | 33.1 | 181 | 85.1 | 69.2 | 141 | 16.3 | 8.0 | 250 |
| 8 | Magnesium | 5.13 | 18.1 | 7.81 | 20.2 | 19.0 | 16.2 | 12.0 | 14.2 | 20 |
| 9 | Fluoride (mg/L) | 0.06 | 1.38 | 1.51 | 0.13 | 0.21 | 0.05 | 0.02 | 1.52 | 1.50 |
| 10 | Total Coliform | 11.0 | 10 | 6.0 | 2.0 | 14.0 | 5.0 | 9.0 | 6.0 | 10 |
| 11 | Faecal streptococcus | 100 | 163 | 87 | 22 | 144 | 0.1 | 120 | 56 | 0 |
Source: Field and laboratory analysis
Calculation of WQI
The WQI for the research region is determined using the parameter standard limit by Nigeria Standard for Drinking Water Quality / WHO, which is shown below. The WQI was calculated using eleven physical, chemical, and biological characteristics. Weights ranging from 1 to 5 are assigned based on the parameter values. Weight 1 is assigned if the gap between the value and the allowed value range is small (i.e if the figure between the value and the recommended standard limit after finding the difference is small then a weight of 1 is given), and weight 5 is assigned if the difference is large. The Weight (w) has been assigned according to its concentration and relative importance in the overall quality of water for drinking purposes and other domestic use. Additionally, the relative weight has been computed and is displayed in table 3 below.
Table 3. Water Quality Index
| Physical, chemical and biological parameters | Standard limit NSDWQ/WHO | Weight given (Wi) | Relative weight (RW) |
| Turbidity (NTU) | 5 | 1 | 0.0911 |
| ph. | 6.5 – 8.5 | 3 | 0.030 |
| TDS (mg/l) | 500 | 5 | 0.152 |
| Calcium (mg/l) | N/A | 0 | 0 |
| Chloride (mg/l) | 250 | 5 | 0.152 |
| Nitrate (mg/l) | 50 | 1 | 0.030 |
| Fluoride (mg/l) | 1.50 | 5 | 0.152 |
| Magnesium (mg/l) | 20 | 2 | 0.061 |
| Sulfate (mg/l) | 100 | 1 | 0.030 |
| Total coliform cfu/1000m | 0 | 5 | 0.152 |
| Faecal streptococcus | 0 | 5 | 0.152 |
| ∑33 |
RW = Wi/ ∑n Wi————————————————–1
RW = 3/33 = 0.0911
Where: RW = Relative Weight
Wi = weight given Ci = concentration of the parameters Qrs = quality rating scale
Si = sub index
Table 4. Displaying the parameters Concentration, quality rating scale and sub-index
| Physical, chemical and biological parameters | Concentration of parameters (Ci) | Quality rating scale (Qrs) | Sub index (Si) |
| Turbidity (NTU) | 2.8 | 56.0 | 16.80 |
| ph. | 7.83 | 97.9 | 8.9187 |
| TDS (mg/l) | 490 | 98 | 14.8960 |
| Calcium (mg/l) | 26.025 | 0 | 0 |
| Chloride (mg/l) | 71.875 | 28.8 | 4.3776 |
| Nitrate (mg/l) | 37.2 | 74.4 | 2.2320 |
| Fluoride (mg/l) | 0.61 | 40.7 | 6.1864 |
| Magnesium (mg/l) | 14.08 | 70.4 | 4.2944 |
| Sulphate (mg/l) | 58.9875 | 58.9 | 1.7670 |
| Total coliform cfu/1000ml | 7.875 | 78.75 | 11.97 |
| Faecal streptococcus cfu/1000ml | 86.5125 | 0 | 0 |
| ∑71.442 |
Qrs = Ci /S × 100 ————————————————– 2
Qrs = 2.8/5.0 = 0.56 × 100 = 56.0
Si = Rw × Qrs ——————————————————- 3
Si = 0.030 × 56.0 = 16.80
Qi = ∑Si ————————————————————— 4
Qi = 71.442
QI = ∑Qi ————————————————————– 5
Table 5. Show the Water quality index classification
| Water quality index level | WQI status |
| 0 – 25 | Excellent water quality |
| 25 – 50 | Good water quality |
| 51 – 75 | Poor water quality |
| 76 – 100 | Very poor water quality |
| >100 | Unsuitable for drinking |
DISCUSSION
The World Health Organization (WHO) and individual countries have worked hard to ensure that certain standards of criteria are supplied in order to ensure the safety of water that people consume, considering the high number of diseases in the world that are brought on by contaminated water. The geological structure, urbanization and use of fertilizer in the agricultural field played a significant role in affecting water quality. Settlement pattern and land use practices in study area leaves inhabitants with limited distance between wells and sanitary structures as such; wells are often located too close to sanitation systems in households without taking water quality into cognizance. Asides the distance between wells and sewage pit and topography, other factors such as seasonal variation, inadequate hygiene and sanitation, well disinfection and well characteristics play significant role in the level of well water contamination. Based on physical criteria, the research determined the safety level of select wells and boreholes in the Lafia district. The turbidity of all wells and boreholes fell within the 5NTU National Standard limit. The wells’ maximum turbidity range is 4.0, whereas the borehole’s is 3.0. The borehole’s lowest range is 1.5, whereas the well’s is 2.3. All of the wells and boreholes had pH values between 6.5 and 8.5, which is the WHO’s recommended range. With the exception of boreholes 1, 2, and 3, which surpass the limit with numbers 742, 758, and 683, respectively, all wells and boreholes fall under the limit for total dissolved solids.
The biological parameters of the study which are total coli form and Feacal strep, have been identified to be of high level in various boreholes & wells. A total coli form of WHO is given as 10. Looking at the analysis, all the wells & borehole analyzed are within the Nigeria standard limit. Except for borehole 1 and well 2 which has the following value 11 and 14.
The analysis gives the feacal streptococcus of all the samples to have exceeded the NSDWQ & WHO Standard which is 0. High value of Total dissolved solid in groundwater are generally not harmful to human beings, but high absorption of these may affect person who are suffering from kidney and heart diseases. Water containing high solid may cause laxative or constipation effects. High level of TDS are caused due to the presence of potassium, chloride, sodium and toxic ions in larger amounts, which are also observed in BH1 with the figure 742, BH2 with 758, BH3 with 683. It is also undesirable to drink as it may taste salty, metallic or bitter.
CONCLUSION AND RECOMMENDATION
The calculated WQI from the empirical formulas for the groundwater samples range from 0 to 58.9 in one case, were Bh4 has 28.0 and in another case the value ranges from 0 to 98.0 were W1 has 98.0 and falls within the Good (Acceptable), Bad and Very Bad (Rejected) class. Every parameter generated a different index range. Findings from the research revealed that all wells & borehole sampled have high faecal streptococcus above the recommended level for drinking water, thereby requiring the need for urgent public health intervention. Alongside, there is need to increase awareness of the community towards the dangers associated with the use of contaminated water; the danger in constructing septic tanks near water sources and vice versa and treatment of water by boiling and filtering before use for drinking, cooking and washing. In addition to this, there should be restrictions on the free ranging domestic animals and other domestic solid wastes which are dumped around the house; which could be possible sources of bacteria pollution of the hand dug wells and borehole. Preference should be given to water protection through well monitoring and routine analysis of well water samples over the sporadic campaigns against outbreak waterborne infections. Change assessment studies should also be conducted to evaluate the trend of the groundwater pollution over time as waterborne diseases could continue to be a health problem in study sites if appropriate measures are not taken.
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