Detection of Water Spread Area Changes in Eutrophic Lake Using Landsat Data

Area of Science:

• Hydrology and Remote Sensing
• Environmental Monitoring
• Water Resource Management

Background:

• Nainital Lake is a vital water source for Uttarakhand, India, supporting tourism, domestic use, and irrigation.
• Climate change and over-exploration necessitate regular monitoring for effective conservation of lake ecosystems.
• Understanding dynamic changes in water spread area is crucial for preventing degradation.

Purpose of the Study:

• To investigate the dynamic changes in Nainital Lake's water spread area from 2001 to 2018.
• To evaluate the accuracy of remote sensing-based water indices for monitoring lake area.
• To determine trends and the magnitude of change in water surface area.

Main Methods:

• Utilized multiband rationing indices: Normalized Difference Water Index (NDWI), Modified Normalized Difference Water Index (MNDWI), and Water Ratio Index (WRI).
• Developed models in QGIS 3.4 software and validated with a physical GPS survey.
• Applied non-parametric Mann-Kendall and Sen's slope estimator tests to analyze trends and magnitude of change.

Main Results:

• The Normalized Difference Water Index (NDWI) demonstrated the highest accuracy (96.94%) in assessing water spread area.
• A significant decrease in Nainital Lake's water spread area was observed, particularly from March to June (7.7%).
• Seasonal decreases were also noted from July to October (4.67%) and November to February (2.79%).

Conclusions:

• Nainital Lake's water spread area has sharply decreased between 2001 and 2018.
• The study provides crucial data for policymakers and water experts for lake restoration and conservation efforts.
• Remote sensing techniques offer a viable solution for monitoring lakes in challenging terrains like Uttarakhand.