The plan to build a reservoir at the head watershed area in the Shivapuri Mountain to augment the flow of the polluted Bagmati River in Kathmandu Valley has spurred a debate as to how safe it would be and whether the added water will help wash the pollution in the river. An often overlooked aspect of this debate is the very nature of river ecology itself. The existence of a river is defined by its watershed, and without repairing the damage done to the natural functions of the said watershed, no plan, no matter how well-intentioned, is likely to clean the river.

Attempting to use a centralised solution to improve the condition of a decentralised system as that of a river is not only questionable but also imprudent. Further, there is no sense in cleaning only a stretch of the Bagmati if the tributaries such as Dhobikhola, Bishnumati, Manahara and others remain polluted. Without them being cleaned—which is beyond the scope of the proposed plan—Bagmati will remain dirty.

Unsurprisingly, we don’t know if the revival of the rivers in the valley is even possible because no attempts have been made yet to restore them. It would be more logical to have a holistic plan to revive the Bagmati, including its tributaries. If not, boomers will be the last generation to see the rivers that served thousands of households and farmers in the valley, providing water for irrigation as well as religious and cultural purposes. Posterity will only remember them as highly-polluted, malodorous blights.

River restoration

Over the years, several dead or polluted rivers have been restored in different parts of the world. For example, River Aravari in Rajasthan, India, which had gone dry for more than six decades, started to flow when hundreds of Johads, a traditional technique of collecting rainwater, were built along the river in the late 1990s. Now, a river parliament governs Aravari and makes policy decisions regarding river management. Another example most people cite is that of the River Thames in the United Kingdom, which was declared biologically dead in the 1950s. Today, it is one of the cleanest rivers in the region. The change primarily occurred when the sewer system was improved and strict regulations were imposed on the use of pesticides and fertilisers.

The Cheonggyecheon River in Seoul, South Korea, is another fascinating example. The river was covered with concrete, and a highway was built in its path when it dried up in the 1950s. Later, the wrongs were righted by removing the concrete and dismantling the elevated freeway. Water was pumped in from the Han River to make Cheonggyecheon flow again. Now, this artificial river is an attraction for tourists and residents.

If a river as polluted as the Thames or as dry as the Aravari can be revived, or if a river covered by a highway can be turned into a vibrant tourist attraction, one can hope that the Bagmati may be revived and restored as well. However, one should consider the watershed feeding the river before being so hopeful.

Watershed’s role

The function of a watershed is to store part of the rainwater as an intermediate reservoir in the soil and underground aquifers to be released gradually after the rain has ceased to fill the springs and streams flowing. In that sense, every unit area of a watershed is crucial in maintaining the river flow. Unlike the Cheonggyecheon or the Thames, where watersheds were either irrelevant or widespread, the Aravari example, with a watershed area approximately the same as that of the Bagmati, was possible because hundreds of rainwater storage tanks were built along the river channel surrounded by a predominately agrarian watershed.

Concerning the Bagmati, a large part of the watershed area within the valley occupies the valley floor, which was once sprawling open farmland. Most of it has been blanketed by the expansion of urban Kathmandu in the last half a century, restricting the replenishment of its aquifers. The recent settlements, including the newly constructed access roads, are located along the river, which are essentially the groundwater recharge areas. Consequently, the contribution of seepage to the river from the adjacent areas, especially between the monsoons, has been reduced to the minimal. Furthermore, everything that helped maintain the natural environment of the river is lost. The sand deposits at the foothills that helped store a part of the rainwater have been levelled to develop plots for housing. Decades of extraction have left Bagmati and its tributaries devoid of sand. Groundwater has been over-consumed.

In sum, it isn't the Bagmati and its tributaries that have dried; rather, the watershed areas designed to contribute water to these rivers have become parched. That is the price we have paid with our thoughtless, unimpeded pursuit of development, ignoring nature’s limitations.

Doable alternatives

A river renews itself, but when the stressors surpass its ability to do so, it ceases to exist, especially when the watersheds are small. Bagmati is a good example. It will be futile to attempt its restoration by investing in a structure with unknown associated risks and expensive costs involved. Moreover, if we concede that we have failed to save this important natural heritage, we may as well accept that we aren’t prepared to handle other emerging environmental challenges with much wider consequences. Therefore, no matter how difficult it may be or how long it may take, we have to think about how we can restore the watershed functions of the Bagmati to help it breathe.

Sustainable and cost-effective options within our means are worth investing in. Aravari can be a good case study. A decentralised system of small but numerous such structures to collect rainwater across the mountains and valley floor should be the way forward. But this can only be achieved when the local communities take the lead on such a project. The guiding principle should be to catch rainwater wherever it falls.

The government should start with a small tributary such as the Godawari to see how a decentralised and community-led approach to river restoration would work within an urban environment. If such an alternative is initiated with community involvement, it will help create a sense of ownership. Lessons from initial works can be rolled out to cover the valley floor, which forms a large part of the watershed, to store as much rainwater as possible in the intermediate groundwater reservoir during the monsoon. This should be the way forward to reviving the river if we are serious about handing over a pristine natural heritage to our children and grandchildren.