Dhobikhola, The Northern Tributery of Bagmati River

The environmental health and water quality of Bagmati river has been affected by the valley centric development of Kathmandu Valley. The tribuatries of Bagmati are not exception in the course. The tributaries are abused by reckless river bed excavation, water extraction and pollutant dumping.
Dhobikhola is northern tributary of Bagmati river and it drains the core urban areas including Kapan,Mandikatar, Ratopul, Anamnagar,Baneswor, Thapathali. It merges with the Bagmati at Buddhanagar. It is also known as "Rudramati" and hosts a number of religious and cultural heritages like Bhadrakali, Shiva Mandir, Maitidevi at its banks.

Aerial photograph showing Dhobikhola tributary of Bagmati river

Dhobikola originates from Shivapuri Danda and has catchment area of 31.2km2 and river length of 18.2Km. The river is at good health around its source however gets overloaded with filthy water as it goes downstream. The river as it converges with Bagmati seems no better than a mere sewage drain. The dissolved oxygen levels before the dense settlement areas of Chunikhel is 11mg/l which drops to 0.56mg/l at the time it converges with Bagmati river.

The river shares bad fate as most of the other tributaries of Bagmati river.Sand mining is excessive in the river and bamboo weirs are dominant structures upstream for sand collection. Heaps of sand being uploaded in tippers is not a rare scene at Chunikhel area. A gravelled road undulates with the river and loaded tippes pass through it producing vibration and bankcutiing of the river territory.

Measuring dissolved oxygen level in Dhobikhola before dense settlement of Chunikhel

River bed excavation at headwater region  of Dhobikhola near Chunikhel

 The sand mining and river bed excavation has posed serious effects on the riverine environment. It destroys habitat for many aquatic species. This cause disruption in the riverine ecology. The sediment laded water affects respiration and other phenomenon killing fishes. The mixing of untreated waste water has made stream toxic and unsuitable for any living being.

Sediment load in the river water after Chunikhel area.

By the time the river passes Ratopool, Maitidevi and reaches Baneswor, the river is analogous to black water. The river bank is channelized and few very fine deposits of clay like sediment can be seen. The river bed is homogenous with almost all fine nutrient laden silty soil.

According to fundamentals of aquatic ecology, the  more heterogenous the river territory, the better is the river health. For example the heterogenity in river bed ceates more habitat and hence biodiversity. The diversified ecological conditions serves to purify water and increase the self purification capacity of the river.

Dhobikhola confluence at Bagmati river

 Courtesy: Water and Urban Initiative Project
Special Thanks: Bishal Jibi Ghimire

References
Bagmati Action Plan
http://np.geoview.info/dhobikhola_dhobikhola,5407597w