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Bhutan (2021 Deadline)
Understanding of source waters and recharge mechanisms of mountain springs and streams in Radhi and Phongmey Gewogs in Trashigang, Bhutan Himalayas
PI: Tshewang Dendup (tshewang.sherubtse@rub.edu.bt), Royal University of Bhutan
U.S. Partner: Fengjing Liu, Michigan Technological University
Project Dates: April 2022 - June 2023
Project Overview
Mountain springs and streams are primary source water for millions of people in rural communities of the Himalayas for their drinking, domestic, and agricultural needs. Climate change, population increase, and economic development are mounting pressures on available water resources from springs and small streams in the region. A Bhutanese government report has indicated that flows in about 35% of springs in the country are declining, while 2% of them have completely diminished. Although Bhutan has high per capita water use capacity, most rivers and streams are inaccessible. Therefore, it is imperative to gain insights into spring and small stream generation, which is otherwise poorly understood in the region.
This PEER project sought to provide crucial information on sources and recharge mechanisms of perennial springs and streams used by local communities, with the aim of developing better water resources management and evaluation of climate change impacts on the livelihoods of these communities. The researchers combined field sampling from springs, streams, rainwater, snowmelt, and soil water with mathematical modeling using stable isotopes and geochemical tracers. The information from this study will support informed decision-making for springshed management plans and help understand the long-term impact of climate change on the fate of mountain springs and small streams.
Final Summary of Project Activities
The PEER project focused on two tributary catchments, the streams Yude Ri and Dungju Ri, within the Gamri watershed in Eastern Bhutan. The researchers conducted a field survey to map the hydrology and select sample sites. They collected a total of 454 water samples monthly from various sources, including main streams, tributary streams, springs, natural ponds, rainwater, and soil water, providing essential data for understanding water dynamics in spring flows. They also measured water level and stream discharge from August 2022 through January 2023 and identified variations in streamflow, with the highest flow during the monsoon season and receding flow in the post-monsoon period.
The team’s geochemical analysis of water samples revealed significant variations in solute concentrations among different water sources, with precipitation showing lower solute concentrations compared to spring water and soil water. The researchers used End-Member Mixing Analysis (EMMA) to determine the contributions of various water sources to spring flows. They found that direct precipitation (snowmelt and rainfall), soil water, and groundwater were the primary sources of spring flows and quantified their contributions to spring flow for all springs.
The project made substantial contributions to education by offering comprehensive training opportunities. Participants like Mr. Sonam Tobgay and Ms. Namgay Dema, assistant lecturers in Chemistry at Sherubtse College, were involved from the project's inception and received specialized training in various fieldwork techniques and analytical methods. Forest officers and laboratory assistants also underwent training, while third-year Chemistry BSc students at Sherubtse College benefitted from supplemental training, enriching their undergraduate program. The project's impact extended to the design and construction of essential equipment for collecting soil water and groundwater. These custom-designed tools proved instrumental in practical learning experiences for first-year BSc in Environmental Science students and found potential utility in Forestry and Agriculture programs (e.g. soil nutrient analysis of the cropland or forest) within the Royal University of Bhutan. Additionally, the acquisition of research equipment, including a portable flowmeter and cold storage refrigerator, ensured long-term benefits. International partnerships were also strengthened. The PI Tshewang Dendup and co-PI Dendup Tshering visited their U.S. partner Fengjing Liu in Michigan to collaborate on data analysis, modeling, and planning for report writing in April 2023, and in June Dr. Liu paid them a visit in Bhutan, during which he assisted with a training workshop and took part in field site visits.
Tshewang Dendup and his colleagues presented their preliminary findings presented virtually at the Assembly of the American Geophysical Union in December 2022, as well as through other workshops. The PI joined Water Research Bhutan (WRB), an informal scientific society focusing on the promotion of research and management of water in Bhutan. WRB publishes a monthly technical article in one of the newspapers in Bhutan, on issues related to freshwater and associated ecosystems, biodiversity, and hydrogeology, and the PI contributed two articles that closely align with the PEER project.
The Trashigang Forest Division Office, which collaborated on the PEER effort, is piloting a project as part of an initiative to revive drying water sources in Bhutan. The team shared their findings and provided basic training to foresters on methods for determining groundwater sources or origins using geochemical and isotopic tracer techniques, which appears to be effective for such a study in complex mountain terrain. Although the PEER project ended on June 30, 2023, its impacts continued to be felt afterwards. The PI was invited to participate in the national consultative meeting on "Managing Cryosphere and Water Risks in Bhutan," held August 9-10 in Bhutan. The event was organized by the National Centre for Hydrology and Meteorology (NCHM), Bhutan in collaboration with the International Centre for Integrated Mountain Development (ICIMOD) based in Nepal. The PEER team is well positioned to explore the scope for cooperation with these and other national and international organizations in the areas of cryosphere analysis, disaster risk reduction, and water resource management, and they also hope to continue collaborating with Dr. Liu as well.
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