Nakhhu river: The Southern Tributary of Bagmati river

Bagmati river is fed by Nakhhu tributery from the southern part of Kathmandu Valley.  Nakhhu river originates around Tikabhairab George and flows downstream encompassing Lele, Chapagaun, Bungmati, Saibu, Kusunti and then converges with Bagmati river at Chovar. The Ekantakuna-Tikabhairab road undulates with the river and crosses it at Nakhhu.

Map of Kathmandu Valley showing Nakhhu river territory

Nakhhu river though is at natural conditions at the source, is impaired by human activities at it flows downstream. Human activities like haphazard stone quarrying, squatter settlement encroaching river territory, and road alignment along the river has affected the natural being downstream.

Nakhhu river at Nallu area

Nakhhu river at Bungmati area

The land use pattern of the river catchment varies from the headwater region to downstream. The dominant landuse at the source is forest and farming with scanty human influence which turns into massive quarrying, encroachment and domination by human settlement at downstream. The connection of untreated sewerlines discharging into the river bosom has affected the riverine water quality and the aquatic fauna.

Quarrying activities at Nakhhu river (source ICIMOD)

The river accumulates excessive pollutants as it reaches Nakhhu area. The clear river water turns dark and stinky as it reaches the stretch. Dissolved oxygen is necessary to maintain aerobic conditions in surface waters and is considered a primary indicator when assessing the suitability of surface waters to support aquatic life. The dissolved oxygen drops from 6mg/l to 0.63mg/l as it reaches Nakhhu. Dissolved Oxygen levels >2mg/l is unsuitable for most aquatic organisms.

Measuring dissolved oxygen at Bungmati (Photo credit: Bishal Jibi Ghimire)

The river at Nakhhu area

 Sand mining activities are rampant in the mid section of the river. Large Tippers can be seen moving along the river-way for transportation. Crusher mills can be observed at the river banks that provides materials for urban development of Kathmandu Valley. The operation of the quarry has caused large volume of sediments which has affected the sediment load concentration of the river. The unnatural increase in sediment loads adversely affects the aquatic fauna and hence disturbing the overall riverine ecology.