Bhutan Journal of Natural Resources and Development

Mapping Water Resources and Potential Recharge Zones: A Watershed-Based Study of Tarilum Watershed, Drujaygang, Dagana Dzongkhag

Ngawang Dorji — Mon, 30 Jun 2025 00:00:00 +0000

This study assessed the ecological integrity and functionality of the Tarilum watershed using a watershed-based approach. Due to the lack of alternative watersheds nearby, this watershed is critical for sustaining the gewog’s water requirements, both for drinking and irrigation. The assessment, carried out using the 2016 watershed classification guidelines, GIS, and hydrogeological studies, categorized this watershed as ‘Degraded category’, primarily due to environmental stressors such as soil erosion, infrastructure development, and unsustainable land use practices. The study further identified such problems as porous and disturbed recharge zones and steep slopes in the watershed’s upper regions that require immediate management interventions. The results indicate a necessity for strategic land-use planning and implementation of erosion control measures to safeguard groundwater recharge and maintain water availability. Recommended management strategies include afforestation, sustainable land management, and recharge zone protection interventions. Adopting these strategies is anticipated to significantly enhance the watershed’s resilience, ensuring sustainable water availability and long-term ecological health.

Habitat Preference and Foraging Technique of River Lapwing (Vanellus duvaucelii Lesson, 1826) in Punatsangchhu River, Bhutan

Mirza Sium Masud, Dhan Bdr Gurung, Ugyen Dorji — Mon, 30 Jun 2025 00:00:00 +0000

The River Lapwing is experiencing population decline and has recently been categorised under near threatened. This study examined the habitat preferences and foraging patterns of River Lapwing in the Punatsangchhu River in Bhutan. A systematic line transect method covering 123 km, incorporating 42 sampling stations, was deployed to observe foraging technique and foraging success of River Lapwing. In addition, habitat parameters, water parameters and macroinvertebrate were recorded to observe their relationship to River Lapwing occurrence. The present study results indicated that the River Lapwing occurrence correlated with higher macroinvertebrate diversity (H’ = 1.93) compared to those where the River Lapwing did not occur. Sandbars were the primary foraging ground for River Lapwings, and a moderate positive relationship was observed between the sandbar used by the River Lapwing and the occurrence of the River Lapwing (r = 0.44, p = 0.00). However, human disturbance along the river and the occurrence of River Lapwing (r = -0.34, p = 0.00) had a moderate negative relationship. Among the five foraging techniques used by River Lapwing across the study area, walk-halt-peck (37.96%) was the highest, followed by walk-halt-probe (30.56%). Moreover, the River Lapwing foraging success was more than half (62.96 ± 9.53%) of the total attempts. Thus, River Lapwing occurrence was positively associated with higher macroinvertebrate diversity and the availability of sandbars along the river, while human disturbance negatively impacted their occurrence.

People’s Perception on Status of Spring Water, Degradation, and Adaptation Measures: A Case Study from Sarpang, Bhutan

Damudar Dahal, Toshiharu Kojima, Chandra Man Rai, Om Katel, Benu Prasad Dahal — Mon, 30 Jun 2025 00:00:00 +0000

Springs serve as the primary source of drinking and irrigation water in mountainous region worldwide. Despite the widespread drying up of mountainous springs, the identification of degradation factors at the local level is understudied. This study assessed the status of springs, degradation factors, and potential adaptation measures adopted by local people. The data were collected through household questionnaire survey and field visit in Lhayuel village of Sarpang district. The result confirmed that more than 60% of the people observed decline in spring flow, with older people being more aware of the springs drying up than their younger counterparts. Climate change (x̄ = 4.28), road construction (x̄ = 4.06), and landslides (x̄ = 4.00) were identified as the leading cause of springs drying, based on perceptions measured with a five-point Likert scale. Further, the satellite data showed increasing trend of annual mean temperature (p = .00, R² = .34) and decreasing annual total rainfall (p = .00, R² =.05) over the past 122 years. To address the drying of springs, people implemented various adaptation measures including the artificial expansion of lakes, fencing around springs, minimizing grazing and timber extraction, and planting native tree species around the springs. This study provides a foundation for identifying spring water issues in mountainous regions and establishes a framework for implementing adaptation measures.

Assessment of Heavy Metal Contamination in Soil and Plants Around Bhutan’s Main Landfill

Durga Man Ghemiray, Bhagat Suberi, Karma Wangchuk — Mon, 30 Jun 2025 00:00:00 +0000

Heavy metal contamination in landfill environments poses significant risks to public health and the environment. This study assessed heavy metal concentrations of iron (Fe), zinc (Zn), copper (Cu), and manganese (Mn) in soil and selected plants across three sites in Bhutan’s main landfill using Flame Atomic Absorption Spectrophotometry. Results showed heavy metal concentrations in soil followed the order Fe > Mn > Zn > Cu, with Fe levels in some samples exceeding the WHO/FAO limit of 10 mg/kg set in 2001. This exceedance, observed in soil collected directly from the landfill environment, indicates contamination likely caused by leachate migration. At a depth of 15–30 cm, a significant difference (P = 0.05) in heavy metal concentrations was detected between areas above and below the landfill. Correlation analysis revealed the intricate interplay between heavy metal concentrations and soil attributes, with soil organic matter playing a pivotal role in binding heavy metals. At 0-15 cm depth, Zn showed strong negative correlations (r = -0.940, p < .01) with soil organic carbon (SOC percent) and soil organic matter (SOM percentage) and a positive correlation (r = 0.940, p < .01) with electrical conductivity (EC). At 15–30 cm depth, Mn negatively correlated (r = –0.836, p < .05) with pH and positively correlated (r = 0.878, p < .01) with SOC percentage and SOM percentage. Heavy metal concentration varied among plant species, with Fe being the most abundant metal at the two sites. The bioaccumulation outcome indicated that Zn was the most accumulated in the selected plant. Bidens pilosa L. and Poa annua L. showed higher heavy metal accumulation in roots, suggesting their potential for phytoremediation. The Zn, Cu, and Mn levels exceeded the permissible limits set by WHO/FAO in the specified years, whereas Fe levels in plants remained within the WHO/FAO standards. This study highlights heavy metal distribution, soil-plant interactions, and environmental risks in landfill areas, offering strategies for contamination management. Longitudinal studies are recommended to monitor temporal trends in heavy metal distribution, assess the cumulative impact of leachate migration over time, and refine mitigation strategies. In addition, leachate dilution rate assessments are necessary to better understand contaminant dynamics and environmental impacts.