Sunday, 5 December, 2021

Improving Water Quality Of Bagmati River


Salil Raj Aryal

The Bagmati River is considered the cradle of civilisation in the Kathmandu Valley. Hindus have long been taking bath in this river to start their day in god’s remembrance. This river originates at Baghdwar Falls, situated in Shivpuri Nagarjun National Park near Sundarijal in Nepal and converges with its tributaries such as Manohara, Bishnumati, Dhobikhola, etc. downstream. It is believed that civilization in this region started around 723 BCE.

In recent years, the quantity of wastewater produced in urban areas of the Kathmandu Valley has increased substantially due to rapid growth in population, industrial production, and commercial activities, as well as increase in water consumption pattern. The human activity generated contamination from agricultural, industrial and municipal introduces significant amount of nutrients and organic materials into the rivers.

Dissolved Oxygen
One of the many ways of knowing the scale of polluted water source is by observing the Dissolved Oxygen (DO) level. Oxygen is measured in its dissolved form as DO. It is a barometer of the ecological health of a stream and is the most important parameter for protection and survival of aquatic life. Discharge of degradable wastewater in the flowing water results in a decreased in DO concentrations due to metabolism of pollutants by microorganisms, chemical oxidations of reduced pollutants, and respiration of plants, algae and phytoplankton.
If more oxygen is consumed than is produced, dissolved oxygen levels decline and sensitive animals may move away, weaken, or die. The cold-water minimum DO has been established at 4mg/L considering a proportion of the less tolerant insect species common to salmonid habitats. This goal can be achieved by controlling the wastewater pollution loads, by flow augmentation and by oxygenators.

Water pollution remains a challenging issue for the sustainable development of Kathmandu Valley despite several infrastructural, awareness-raising and policy measures. Before 1980 A.D., the Bagmati River was in drinkable condition. In recent years, the surface water is degraded due to inadequate wastewater treatment facilities that have accelerated the accumulation of untreated wastes and wastewater from domestics, industries and hospitals into rivers as point source of pollutants.

The sewers lines have direct connection with the Bagmati river and its tributaries with no wastewater treatment plants. Also, river encroachment, slum dwellers, river corridor road construction has narrowed the river and is another source of non-point source of pollutants. This is because, all these activities make river bank left with impermeable surface that affects infiltration rate, causing rain water discharged into river with soluble and insoluble pollutants to be a non-point source of pollution to Bagmati River.

The water quality data for this study has been taken from High Powered Committee for Integrated Development of the Bagmati Civilization (HPCIDBC) website. March 2021 and April 2021 data has been considered for the study purpose. Details of elevation, distance between two monitoring stations and chainage from Sundarijal is taken from Google Earth pro. This study aims to know the Bagmati River water pollution level along a 28.5 KM stretch between Sundarijal (S1) and Chovar (S11) consisting of total 11 data collection stations within Kathmandu valley.

What we can infer from above table is, water quality at Sundarijal is in clean and natural condition since the DO level is 6.7 mg/L. As we move down the river trail, it can be observed that as water quality at Gokarna area has been compromised since the DO level has come down to 3.5 mg/L. The dense urban settlement begins from around this area.

By the time Bagmati River reaches Manohara and Bagmati confluence the water quality has degraded till such a length that at the DO level has been consistently been 0 mg/L for 5 consecutive stations. The difference in DO level at Sundarijal and Sundarighat speaks volume about the pollution level in Bagmati. From this data we can say that 12.26 KM of Bagmati River is completely septic. DO level below 4mg/L is an indication of complete loss of aquatic life and their habitat. Fisheries and other aquatic lives cannot survive in this water condition due to extreme hypoxic situation.
Many solutions have been proposed and may have been carried out to decrease the level of pollution in Bagmati river; but the water quality has become nothing but more polluted. With Bagmati Mega Cleaning Campaign, there has not been a significant change in the water quality level of Bagmati River as data suggests.

The fault in Bagmati cleaning campaign is that it focuses just on suspended solid waste but on the quality of water that flows through the river. Bagmati has seven tributaries and if something is to be done about its cleanliness, the campaign should be started in tributary level. This is particularly important now since federalism is already practices in Nepal. The focus of Bagmati cleaning campaign must begin from provincial and municipal level of Kathmandu Valley.

As name suggests “Bagmati Pradesh”, the Pradesh itself has not been working effectively for Bagmati River. In addition, all Eighteen municipalities of Kathmandu valley have to work in collaboration for improving water quality with Bagmati Pradesh with funding provided from municipals and provincial level.

Policy Amendment
For new residential and commercial building constructions, the policy level amendment should be done regarding septic tank provision. For existing structures in Kathmandu valley, wastewater must be treated in collective way from local level with cost sharing model between household and local level government.
Kathmandu Upatyaka Khanepani Limited has been collecting 50% of the water bill amount in the name of sewage disposal.

Rather, this approach can be made proactive and collect certain percentage of bill amount to dedicate it for sewage treatment. After pilot testing this approach, in case of fund insufficiency, additional cost can be raised on the basis of head count in a household by following the principal of polluters pay.

In Kathmandu valley, the only way seen to tackle this problem is by building retaining wall; but there is something extra that we can do. For instance, making a barrier to prevent people from directly disposing wastes in the river in the form of natural park, tree plantation of pollution filter plants such as narkat, willow, water iris can help to curb the pollution level.
Furthermore, a reservoir is being built for Bagmati River cleaning aspect but its tributaries are left untouched. It is suggested to construct, multiple reservoirs in all the tributaries in Shivapuri range. This will particularly benefit in ground water recharge of Kathmandu City.

If we were to follow the recommendations, the days when Bagmati River will have same status as “Pabitra Nadi” as ancient Bagmati Civilization would not be far away. It is high time now that we bring back the life of river that has been flowing in Kathmandu for generations.

(Aryal is a civil engineer who graduated from Indian Institute of Technology Bombay (IIT BOMBAY) specialising in water resources engineering.