The catchment of a lake or a reservoir is the area from which it collects the water that it eventually stores. Across the country many citizen groups and government institutions are trying to protect, revive and restore water bodies. In rural areas too many tanks are being desilted and channels cleared to store water. It is now clear the protecting the water body is but the first step in restoring and reviving it. The big challenge is in the management of the catchment.
Sitting on the banks of Chikkarayyapanahalli tank one sees nothing but rolling green on all sides. The Nandi hill ranges are in the north and from here, when it rains, water flows down in springs and streams to fill the first tank on river Arkavathi. The water is crystal clear and has percolated and filled up the open wells in the downstream area. The waters of the wells are clean and potable. Mulberry, paddy, mango trees grow green.
Yet there is a hidden threat. Slowly farming and agriculture is moving in into the upstream area of the tank and encroaching on the catchment. With this will flow less water into the tank.
Fertilizers applied on the fields will run off into the waters and this nutrient-rich waters will eutrophy and what was once crystal clear water where the reflections of the Nandi Hill range could be seen, will turn green with algae and water plants. The quality of the well waters too will deteriorate. Pretty soon there will be a threat to the drinking water availability. It is a slow, creeping death for the waters and it is through catchment mismanagement.
Come to Bangalore city. The Narsipura -2 lake has seen a lot of community engagement in keeping it clean from garbage, in planting trees and learning about the biodiversity of the lake through dedicated action by many concerned citizens working with the elected representatives. Yet there is a threat to the sustainability of the lake. Sewage enters it through the storm-water drain inlet. Efforts to divert it are not working for many reasons.
The heavy rains of October filled the tank but brought with it plastics, bottles and other garbage along with the storm-water. With garbage collection not being effective in the catchment area, much of it ends up in drains. When it rains this ends up in the lowest point which is the lake.
Urban catchments are much more difficult to manage because of the large-scale presence of solid and liquid waste spread all over the catchment. Without an effective catchment management strategy it will be impossible to manage our water bodies.
The watershed continues to be the unit of hydrology and management which, unless protected, will pollute water both on the surface and below the ground. In the absence of any single institution responsible for the watershed, coordination between various institutions becomes the challenge.
As the unit of the watershed becomes larger and goes into becoming a river basin the institutional coordination becomes even more difficult. The river, the lake or the tank is but a mere recipient of the waters that fall on the catchment. Managing the catchment and keeping it clean and free from pollution will be water wisdom.
