The Madi River, flowing through west-central Nepal, is a typical rain-fed river originating within the Lesser Himalayas. The Himalayan mountain chain and the Tibetan Plateau form one of the world's foremost water towers, supporting several of Asia's largest rivers and providing water to over a billion people in the surrounding lowlands. Stretching across northern Pakistan, northern India, Nepal, and Bhutan, the Himalayas comprise the High Himalayas and the Lesser Himalayas. The Lesser Himalaya, including the Middle Mountain zone, Siwalik foothills, and Terai plain, features denser human habitation and primarily rain-fed water supplies at elevations below 3,000 meters.

The vulnerability to global warming of the higher, ice-covered regions, often called the "Third Pole," and the resulting changes in downstream water provisioning are extensively studied. However, despite their critical importance, the hydrological implications of climate and land use changes in the Lesser Himalayas have received less scientific attention. More than 80% of the total streamflow emanating annually from the Himalayan mountain chain derives from rain falling in the Lesser Himalayas. Five decades ago, efforts to restore degraded upland forest lands in the Lesser Himalaya, particularly in Nepal, involved planting fast-growing pine trees. While these efforts helped stem local soil erosion and provided fuelwood to hill dwellers, the thirsty pines also contributed to reduced spring flows and streamflows, creating new problems. Climate change, human migration to urban centers, abandonment of rain-fed agriculture, and other interacting factors have further complicated the water management challenges in the Lesser Himalayas.

In September 2023, an international symposium was held in Pokhara, Nepal, to review the connections among water, forests, and rural livelihoods in the Lesser Himalayas. The meeting brought together experts from Nepal, China, India, the Netherlands, and the United States, along with representatives from international institutions, government officials, and regional journalists. The symposium identified key knowledge gaps regarding forest-water-livelihood relationships and outlined steps to address these gaps.

Until the mid-1980s, it was widely assumed that the widespread degradation and loss of forests in the Lesser Himalayas were the primary causes of flooding and sedimentation in the plains of Bangladesh and northern India. However, it was later found that other factors, including the region's steep topography, concentrated rainfall, and frequent tectonic activity, had a greater influence. Despite this, advanced forest degradation and loss in the Lesser Himalayas still had adverse local hydrological effects, including accelerated erosion, reduced rainfall infiltration, and groundwater recharge.

A major reforestation program initiated in the mid-1970s, along with community-based forest management practices and government regulations, led to remarkable improvements in the extent and condition of forests in the Nepalese Lesser Himalayas. Today, nearly 40% of Nepal's forests are managed by local Community Forest User Groups, resulting in significant forest cover growth and improved conditions.

The trend of rural-to-urban migration, driven by the search for better employment opportunities and other factors, has contributed to the regreening of the Lesser Himalayas. However, this migration has also led to agricultural labor shortages and the abandonment of upland agricultural fields. Supplying high-quality water to urban centers has become increasingly important, yet residents in rural upland areas still need daily water supplies. Nearly 80% of Nepal's hill and mountain dwellers depend on spring water for various uses.

The regional climate's seasonal character, with most annual precipitation occurring during the monsoon season, exacerbates water scarcity during drier parts of the year. Increasing urban water demands have intensified the effects of natural dry-season decreases in water supply. Declining spring water discharges, higher temperatures, erratic rainfall, disruptions from road building, and advanced soil degradation are frequently mentioned as potential causes of this trend.

The Pokhara symposium identified several vital contributors to the region's water supply problems, including increased urban demand and declining streamflow from rain-fed Lesser Himalayan catchments. The variability in precipitation and streamflow across the region has hampered precise determinations of the causes of these declines. Additionally, the effects of reforestation on groundwater recharge and stream base flows are less clear and require further study.

The symposium attendees called for renewed forest hydrological field studies through multidisciplinary collaborations. A new partnership nicknamed the "four harmonious friends," after a famous Buddhist parable, was formed to support new data collection and field measurements in representative recovering hill forests and mature tropical hardwood forests. These efforts aim to provide sustained measurements and serve as training grounds for students.

Boosting research and graduate-level education on watershed ecosystem management is crucial for developing local knowledge on forest management and hydrology. These steps will help ensure adequate water supplies for rural and urban areas of the Lesser Himalayas, preserve viable ecosystems, and adapt to climate change.

Learn more by visiting Eos., "Forests, Water, and Livelihoods in the Lesser Himalaya."