Assessing Climate and Land Changes in a Himalayan Watershed

Jim Crocker
23rd February, 2024

Assessing Climate and Land Changes in a Himalayan Watershed

Image Source: Natural Science News, 2024

Understanding the future of our rivers and the potential for flooding is crucial for preparing for the challenges that come with a changing planet. The Puthimari River, a tributary of the mighty Brahmaputra in India and Bhutan, is known for its significant contribution to downstream floods, especially during the monsoon season. A recent study by the National Institute of Hydrology, India[1], has taken a closer look at how this river's discharge might change in the future due to both land use changes and climate change. The study spans an extensive period from 2025 to 2099, dissected into three 25-year intervals. It employs a sophisticated tool known as the Soil and Water Assessment Tool (SWAT), which is a computer model that predicts the environmental impact of land use, land management practices, and climate change. SWAT has been successfully calibrated and validated, showing high reliability in its predictions for the Puthimari River. Climate change projections were based on five different climate models, which are part of the larger Coupled Model Intercomparison Project (CMIP5). These models help scientists understand how climate variables like temperature and rainfall might change under different scenarios. The study looked at two scenarios: RCP4.5, which assumes that we will moderately reduce our greenhouse gas emissions, and RCP8.5, a scenario where emissions continue to rise unabated. Land use and land cover change (LULCC) were also a significant part of the study. The future landscape of the region was projected using a method called the CA-Markov model, which predicts changes in land cover by considering both the current state and the 'rules' that have driven past changes. The findings are telling. By the end of the century, the study predicts a nearly 20% increase in rural settlements and a decrease in forests, croplands, and water bodies. These changes in land use could have profound effects on the river's discharge. For instance, more settlements can lead to increased runoff as less water is absorbed into the ground, while fewer forests can mean less water is retained in the ecosystem. When it comes to climate change, the study forecasts a significant increase in monsoon rainfall—up to 38.92% under the worst-case emissions scenario. This would lead to a corresponding surge in river discharge, which could exacerbate flooding risks. Under the moderate emissions scenario, the increase in discharge is predicted to be 34.27%, still a substantial rise. These findings echo the broader patterns observed in other studies. For example, research in the Kibungo sub-catchment[2] also used SWAT to predict changes in streamflow due to climate and land use changes, finding significant decreases in rainfall and increases in temperature that could affect water resources. Similarly, the global land use change analysis by HILDA+[3] highlighted the extensive impact of land use changes on the environment, with different trends in the Global North and Global South. The study in Nagaland, India[4], further emphasized the importance of monitoring LULC changes due to rapid urbanization and its environmental consequences, such as landslides and flash floods. The study on the Puthimari River not only corroborates these findings but also adds a new dimension by combining the effects of LULCC and climate change on river discharge. This comprehensive approach provides a more complete picture of the future risks and can inform better flood management strategies. The implications of this research are significant for policymakers and local governments. With the potential for increased flooding, there is a clear need for both structural measures, like dams and levees, and non-structural measures, such as land use planning and community preparedness programs. The study offers a foundation for developing strategies to mitigate flood risks and manage the watershed sustainably. In conclusion, the Puthimari River study is a critical step forward in understanding the complex interplay between land use, climate change, and river dynamics. It provides a valuable blueprint for future research and a guide for decision-makers who must navigate the challenges of a changing environment.



Main Study

1) A combined impact assessment of climate and land use/land cover change in an Eastern Himalayan watershed in northeast India.

Published 22nd February, 2024

Related Studies

2) Impacts of climate and land use/cover changes on streamflow at Kibungo sub-catchment, Tanzania.

3) Global land use changes are four times greater than previously estimated.

4) Monitoring land use land cover changes in the Eastern Himalayan landscape of Nagaland, Northeast India.

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