Map indicating (in yellow) lake locations chosen for the study
Image Credits: Prof. J. Indu and Kumar Nitish

The following article was originally written by Mr. Joel. P. Joseph and published here.

IIT Bombay’s new web application, IMPART, allows researchers to track changing water surface temperatures and can help to track climate change

Studies indicate that sea surface temperatures, along with the surface temperatures of rivers, have consistently increased in recent years. In 2023, sea surface temperatures saw their sharpest rise in more than a century. Climate change and human activities are driving this trend, particularly in Asia, where river surface temperatures are rising rapidly. Lakes, critical sources of freshwater, are also experiencing significant impacts.

Water bodies heat up much slower than materials on land, making their surface temperature a key indicator of global warming and climate change. These changes have profound effects on both aquatic and terrestrial ecosystems over time. Hence, monitoring lake water surface temperatures is essential for managing water resources and tracking climate change. For instance, rising surface temperatures can trigger harmful algal blooms, reduce oxygen levels, and adversely affect aquatic life in the lake. Accurate measurements of lake water surface temperatures are therefore crucial for safeguarding these ecosystems.

To address this need, Kumar Nitish and Prof J. Indu from the Department of Civil Engineering and Interdisciplinary Centre for Climate Studies at the Indian Institute of Technology Bombay (IIT Bombay) have developed a novel open-source web-based application called IMPART. Short for Integration of dynaMic water extents towards improved lake wAter suRface Temperature, IMPART calculates the temperature of lake water surfaces considering the dynamic changes in lake areas. Their study, published in the Journal of Environmental Management, overcomes the shortcomings of traditional methods, which assume constant lake areas—a simplification that can lead to misleading results.

“Accounting for dynamic changes in lake water surface extents significantly improves the accuracy of lake water surface temperature estimations,” remarks Prof Indu J, the lead researcher of the study. Factors such as growing urbanization, seasonal variations, and rising temperatures alter lake surface areas and volumes from time to time, necessitating a more nuanced approach.

IIT Bombay’s IMPART bridges this gap by incorporating real-time changes in lake extents to calculate both static and dynamic lake water surface temperatures. The static temperature assumes a constant lake area, while the dynamic temperature adjusts for changes in water extents. IMPART’s intuitive, user-friendly interface makes it easy for individuals, researchers, and organizations to record and access lake water surface temperature data and track lake ecosystems more effectively.

The researchers used the temperature data recorded by satellite instruments (namely, MODIS and LANDSAT) and lake extent data from the lake images obtained from Google Earth Engine for the particular days. Using a combination of these, they determined the temperature of the lake area corresponding to that time. The IMPART toolkit calculated both static and dynamic lake water surface temperatures for 342 lakes worldwide, including 115 lakes in India. For its static module, the software used the same water extent indicated in the databases from where monthly surface temperatures were obtained. For the dynamic module, the IMPART toolkit estimated how the water area changed for each monthly measurement of surface temperature in the database.

“Dynamic considerations have now become feasible thanks to the advancements in remote sensing, cloud-based platforms (such as Google Earth Engine), and algorithms capable of incorporating reflectance data with dynamic lake extents, (thus) enabling a more accurate and comprehensive analysis,” explains Nitish.

The findings revealed significant differences between static and dynamic temperature estimates for more than half the lakes studied. Notably, these differences were statistically significant for over three-fourths of Indian lakes. Prof. Indu says, “Our approach highlights the importance of treating lake water surfaces as dynamic rather than static, enabling a more precise understanding of how freshwater ecosystems respond to climate change.”

The study also identified climatic zones where dynamic measurements are especially crucial. By categorizing locations of the lake into tropical, arid, temperate, cold, and polar climatic zones, the researchers found that the differences between static and dynamic temperatures were most pronounced in arid, temperate, and tropical zones compared to cold and polar regions.

IMPART allows climate scientists to monitor lake water surface temperatures more accurately and study and mitigate the impact of these changes on the ecosystems within and around. It has a strong potential as a tool for tracking climate change, and the tool’s applications can be extended to other research areas.

“IMPART can be applied to water resource management, ecological health assessments of lakes, and early-warning systems for lake ecosystems under environmental stress,” Prof Indu concludes.

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The original academic article titled Integration of dynaMic water extents towards imProved lake wAter suRface Temperature (IMPART) was written by IIT Bombay’s researchers and published in the Journal of Environmental Management, Volume 368.

The original paper can be found here.