76.75
1
76.75
1
The Water Quality Index (WQI) Calculator combines multiple water quality parameters into a single score that indicates the overall quality of a water body. WQI simplifies complex water quality data into a number from 0 to 100, where higher values indicate better water quality.
This calculator uses the weighted arithmetic method, which multiplies each parameter's quality rating by its relative weight and divides by the total weight. WQI is used globally by environmental agencies for public reporting, trend monitoring, and comparing water quality across different locations.
The Water Quality Index is calculated as:
WQI = Σ(wi × qi) / Σwi
Where:
Quality ratings are typically: 91-100 Excellent, 71-90 Good, 51-70 Medium, 26-50 Bad, 0-25 Very Bad. Common parameters include DO, pH, BOD, turbidity, nitrates, phosphates, temperature, and total coliforms.
Inputs
Results
WQI = (24 + 16.25 + 22.5 + 14) / 1.0 = 76.75. This falls in the "Good" quality category.
Inputs
Results
WQI of 39 indicates "Bad" water quality, likely requiring intervention before the water is suitable for aquatic life.
Common parameters include dissolved oxygen (DO), pH, biochemical oxygen demand (BOD), turbidity, total dissolved solids, nitrates, phosphates, temperature deviation, and fecal coliforms. Different agencies (NSF, CCME, Indian CPCB) use different parameter sets and weighting schemes.
Each measured parameter value is converted to a quality rating (0-100) using sub-index curves or tables. For example, a DO of 100% saturation might score 95, while 50% saturation scores 30. These curves are established by water quality agencies based on ecological and human health standards.
Generally, WQI above 80 indicates good quality suitable for most uses. Above 90 is excellent. However, WQI should not be the sole criterion for drinking water safety, as it may mask individual parameter violations. A WQI of 75 with one severely failing parameter may still be unsafe.
Roboculator Team
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