Table of Contents
Water Quality Index in Wetlands: Insights from Thol Bird Sanctuary Study
Last Updated: August 31, 2025
Introduction
Have you ever wondered how scientists decide if a wetland’s water is safe for farming or wildlife? Instead of looking at dozens of complex chemical tests, they use a single, powerful tool: the Water Quality Index (WQI).
At Thol Bird Sanctuary, a Ph.D. study by Dr. M. H. Bhadrecha (2018) applied WQI to understand whether the wetland can support irrigation and biodiversity simultaneously. This blog will explore:
- What WQI means and why it matters.
- How WQI was measured at Thol Wetland.
- Key findings on water quality and seasonal changes.
- Conservation lessons for wetlands worldwide.
Understanding Water Quality Index (WQI)
The WQI is a numerical score derived from several physico-chemical parameters like pH, dissolved oxygen, hardness, nutrients, and salts. It simplifies water analysis into categories such as excellent, good, medium, poor, or unsuitable.
“WQI being a well-accepted tool for water quality management; need was also felt for determination of WQI from irrigation point of view” (p. 10).
This makes WQI extremely useful not just for scientists but also for farmers, policymakers, and conservationists.
Thol Bird Sanctuary as a Case Study
Located in Mehsana district, Gujarat, Thol Wetland is both a wildlife sanctuary and an irrigation source. With over 92 waterfowl species and thousands of migratory birds, its ecological value is undeniable (p. 28).
But pressures like oil drilling, cattle grazing, plastic waste, and agricultural runoff constantly affect its water quality (pp. 3–5). WQI was applied to assess whether this wetland could still balance human irrigation demands with ecological health.
How the Study Measured WQI
Samples were collected across three locations representing both core and tourist-influenced zones. Parameters included:
- pH, conductivity, dissolved oxygen, BOD, COD
- Nutrients: nitrate, phosphate, ammonium
- Salts & ions: sodium, chloride, sulphate
- Hardness & alkalinity
The study then applied Irrigation Water Guidelines and CPCB classification systems to compute WQI values (Table 4.2 & 4.3, pp. 49–50).
Key Results from Thol Wetland
- Overall WQI – Water was generally classified as good to medium quality for irrigation.
- Seasonal variation –
- Monsoon: better dilution of pollutants, improving WQI.
- Summer: concentrated pollutants lowered WQI scores.
- Spatial variation –
- Core areas closer to catchment water had higher WQI.
- Tourist/recreation zones showed lower WQI due to organic load (pp. 84–85).
- Irrigation suitability – Despite minor pollution, water remained usable for irrigation, supporting local agriculture (Table 5.6, p. 85).
Why WQI Matters Beyond Irrigation
While WQI was developed with agricultural use in mind, it also reflects broader ecological health:
- Bird habitats: Poor water quality affects benthic organisms, which are food for waterfowl.
- Groundwater recharge: Polluted wetlands pass contaminants downstream.
- Human health: Communities using wetland water indirectly depend on WQI monitoring.
As the study warns:
“The status of water quality for wetlands of TBS… was found to be slightly polluted to polluted condition” (p. 18).
Conservation Implications
To maintain balanced WQI at Thol and similar wetlands, the study recommends:
- Controlling agricultural runoff (reduce fertilizers/pesticides).
- Regulating tourism impacts, especially waste disposal.
- Preventing oil contamination from ONGC wells.
- Routine WQI monitoring as part of wetland management.
For policymakers and NGOs, WQI offers a low-cost, repeatable method to integrate into conservation strategies.
(For more on WQI methods, see Central Pollution Control Board guidelines).
Conclusion
The Water Quality Index in wetlands is more than just a scorecard. It is a lens that connects irrigation needs, bird conservation, and ecosystem resilience.
At Thol Bird Sanctuary, WQI revealed that while water is still usable, pressures are pushing the wetland towards stress. Protecting wetlands means protecting both farmers’ livelihoods and migratory birds’ survival.
WQI is not just a number — it’s a warning system for our wetlands.
FAQs
Q1: What is considered a good WQI for irrigation?
Generally, WQI < 50 is excellent, 50–100 good, 100–200 medium, >200 unsuitable.
Q2: How often should wetlands be tested for WQI?
At least seasonally (monsoon, winter, summer) to capture variations.
Q3: Can WQI replace biodiversity assessments?
No, WQI is chemical-focused. It should be combined with biomonitoring (like benthic invertebrates).
Author Bio
Researcher: Dr. M. H. Bhadrecha
Ph.D., Department of Zoology, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara (2018).
Research Guide: Prof. P. C. Mankodi
Source & Citations
Thesis Title: Ecosystem Assessment of Thol Bird Sanctuary with Special Reference to Benthic Macroinvertebrate Community
Researcher: Dr. M. H. Bhadrecha
Guide (Supervisor): Prof. P. C. Mankodi
University: The Maharaja Sayajirao University of Baroda, Vadodara
Year of Compilation: 2018
Excerpt Page Numbers: pp. 10–100
Disclaimer: Some sentences have been lightly edited for SEO and readability. For the full, original research, please refer to the complete thesis PDF linked in the section above.
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