Applying nature-based solution at Nagdaha

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Nagdaha is a sub-urban wetland in Kathmandu Valley. With many wetlands in the Valley in decrepit state, Nagdaha is an urban oasis that has relatively maintained its state. I use the term relatively because the wetland is far from its original condition with sedimentation and nutrient retention being the chief problem causing its deterioration. A while back, the residents say a massive fish kill incident occurred even causing horrid smell for days. A group of youths – Nagdaha Youth Club have been actively involved in its restoration organizing activities for its clean-up, manually dredging sediments and uprooting water hyacinth. Although this is not a sustainable solution, the approach is applaudable. A nature-based solution was needed.

On a fateful day, we happen to meet: the Youth Club members with my friends who work in aquatic ecology and environmental science. We wanted to contribute in Nagdaha’s restoration and the sedimentation retention pond seemed a necessity. The retention pond would act as a buffer zone taking in the sediments and nutrients before it drains into the lake. Seems like a straight forward plan but actually following through the plans would require a lot of efforts. Apart from the technical expertise required we would also need to have the local people support in our work. This was just a thought, then came Wageningen University’s Student Challenge. This was a great opportunity for us because not only were they providing us some funding but they were also providing us mentoring sessions.

So, now we have collected baseline data – depth measurement, precipitation measurement, soil nutrient dynamics, physico-chemical parameter readings, and even some macroinvertebrate collection. The lake’s sediments were mostly composed of sand, silt, and clay and these sand particles need to be retained which will require a pond. The pond will have a deeper section and a shallower section, the later for macrophyte plantation.

Baseline data collection at Nagdaha. From top, left to right – depth measurement using a fish finder, water sample collection, soil sampling, staff gauge construction, and macroinvertebrate collection

We also organized stakeholder meeting. Some residents relate to Nagdaha with their happiest childhood memories from swimming, fishing, meeting friends to quite contemplation the wetland has provided all. They certainly wanted to restore the wetland and one of the costliest measures they had taken was concretization of the embankments. The measure although seems scenically beautiful is a bad move. It is as if reducing a complex ecosystem into a hole.

The residents recalled they used to collect the sediments in the lake for their agricultural use as the mud was highly productive. But now nobody does this and hence, the wetland is facing the problem of sedimentation. The people seemed taken by our plan of constructing a sedimentation retention pond because it harnesses the power of nature to address the problem at hand.

Over the next couple of months, we will be doing just that. And it has been quite a journey till date. I have always wanted a practical on the ground impact-based work. But work and responsibilities have propelled me towards writing reports, doing administrative work, and meetings. These are not unimportant work per se but I have the most alive in field and to see one’s work making an impact gives worth to my work.

 Keep you posted!

Anu Rai

I am an aspiring environmental researcher.

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