Hydrology in Nepal: One of the Most Dynamic River Systems

The latest article in BWI’s “Exploring the Hydrology” series delves into the beautiful country of Nepal and it’s hydrological riches.

Nepal, situated in the heart of the Himalayas, has not only the most stunning landscapes but also a hydrological network that sustains diverse ecosystems, agriculture, and local communities. The complex network of rivers flowing across the country’s diverse topography offers both opportunities and hurdles. In this article, we delve deeper into the significance and challenges of Nepal’s primary river basins. 

Nepal’s Hydrological riches

With thousands of rivers spanning well over 40,000 kilometers, Nepal’s river system is one of its greatest assets. High yearly runoff combined with distinctive topography features make the conditions ideal for Hydropower. As Nepal is located in the Himalayan regions, the region is widely affected by phenomena like erosion and sedimentation. 

Seasonal Variation

The seasonal changes in river flows is significant in Nepal, with about 80% of annual river flows occurring from June to November. The summer season flow contributes to 10% of the annual number, presenting challenges in aligning water availability with demand. The predictions of desired water use might not always match the natural supply patterns, thereby requiring proper planning for sustainable water management.

River Basins: The Heart of Nepal’s Hydrology

Nepal has four major river basins, each playing a crucial role in the country’s river dynamics. The Koshi, Gandaki, Karnali, and Mahakali River basins shape the terrain, supplying water for irrigation, hydropower, and sustaining the country’s population and their needs. These river basins pass through a variety of landscapes, including the Terai plains and the stunning Himalayas. 

The Koshi Basin

Location: Eastern Nepal

Importance:  Widely known as the “Sorrow of Bihar” (because of the frequent floods in the region) the Koshi Basin provides essential water resources for agriculture and supports the existence of a wide variety of flora and fauna in the Koshi Tappu Wildlife Reserve. In addition, the Koshi basin contributes to more than 50% of Nepal’s exploitable Hydropower potential. 

Challenges: The Koshi Basin faces challenges linked to sedimentation, soil erosion, and the management of extreme flooding events.

The Gandaki Basin

Location: Central Nepal

Significance: Referred to as the “Ganges of the Himalayas,” the Gandaki Basin is a crucial water source. Glacier lake outburst floods is a common hazardous phenomenon in this region. The precipitation across the basin widely varies because of it’s diverse terrains and seasonal differences. This basin has also a cultural and religious landscape, and is an essential part of Nepal’s heritage.

Challenges: Soil erosion, deforestation, and the development of industrial projects pose challenges to the intricate balance within the Gandaki Basin

Did you know? The Gandaki Basin is home to over 1000 glaciers and 300 lakes!!

The Karnali Basin

Location: Northwestern Nepal

Significance: The Karnali, which originates from Lake Mansarovar in Tibet, supports several communities, has immense hydroelectric potential, and is home to a wide variety of plants and aquatic life. 

The basin is a rich source of biodiversity, being home to around 200 fish species. The aquatic ecosystems, including lakes, wetlands, and smaller tributaries, contribute to the basin’s diverse biodiversity, making it an important region for researchers and conservationists. The intense monsoon rainfall and the inclination of slopes make it an optimal area for developing hydroelectric power. 

Challenges: Soil erosion, landslides, and sediment loads.

The Mahakali Basin

Location: Western Nepal

Significance: Forming the natural boundary between Nepal and India, the Mahakali Basin supports hydropower and local livelihoods. The fertile plains along the Mahakali Basin support growing agricultural practices. The river is harnessed for irrigation that contributes to local livelihoods and food production in the region. 

Challenges: Transboundary water management and climate change. 

The Need for Sustainable Water Management

As Nepal deals with challenges like climate change, deforestation, and industrial development, sustainable water management practices become even more important. In the face of these issues, leveraging advanced technologies like AI would contribute greatly in managing Nepal’s water resources . For example, BWI‘s discharge forecasts help analyze water flow patterns, thereby contributing to preventing floods, assisting with agricultural resource management, and overall sustainable development.

By understanding the delicate characteristics of its river basins, Nepal can become more water-resilient. The use of advanced technologies, such as river discharge forecasts, aids decision-makers in making informed choices for flood prevention, agricultural planning, and sustainable development.