City needs Blue belt, its lakes, tanks

The City of Lakes - this is what Bangalore was known as before it was called the Garden City. But alas, it's neither a blue, (lakes & water-bodies) nor a green (tree/forest cover) city any more. Most of the lakes in Bangalore were constructed way back in the sixteenth century by damming the natural valley systems by building check-dams & bunds across them.

But, unfortunately, the impact of urbanization has taken a heavy toll on these lakes due to large-scale encroachment for infrastructure and development projects leaving very few lakes today within Bangalore city. More than 20 lakes have been converted into bus-stands, g courses, playgrounds, residential colonies, commercial complexes, etc. In fact few water-bodies were breached under the malaria eradication programme long ago.

Most of the lakes and water-bodies built earlier were man-made for the purpose of drinking water, agriculture, floriculture, horticulture, fishing and other needs. Along with this they have also influenced and regulated the microclimatic condition of Bangalore in a favorable manner. The lakes have also served to replenish groundwater resources.

With nearly 920 lakes in the 1960s and less than 500 in 1993 and down to just about 50 in 2015 the city has constantly lost one of its major natural resource base. Interestingly, unfiltered water was supplied from tanks & lakes like Dharmambudhi (present day Bus station), Millers tank (opp. Cantonment railway station), Sankey and Ulsoor tanks. Later, from late 1890s water was supplied from Hessarghtta and then it was also obtained from Thippagondana-halli in 1933. This only shows that Bangalore had enough water resources to sustain its population and their activities.

The topographic features of the city clearly indicates radial slopes towards east and west with a smooth ridge running north to south. The rainfall over this ridge gets divided and flows east or west into the three major slopes and valleys namely - Koramangala - Challagatta valley, Hebbal valley and Vrishabavathi valley.

These undulating landscapes and terrain of the ridges, hills, valleys and terrain lends itself perfectly to the natural creation of lakes and water-bodies that can capture and store maximum rainwater. In addition to creating natural water bodies small & medium streams are also formed by each of valley starting with the ridge at the top. Thus, a series of shallow tanks, varying in shape & size are naturally formed. This overall topography & landscape also helps groundwater recharge and strengthen underground water resources.

With an annual rainfall of 900 mm and with three different rainy seasons covering nine months of the year Bangalore can actually harvest sufficient amount of rainwater. Between June & October monsoons account for nearly 65% of the total annual rainfall in the South West monsoon period and 35% during the N-E monsoons (November - December.). The streams between ridges and valleys have been dammed at suitable locations creating a cascade of reservoirs in each of the three valley systems. Each lake stores rainwater from its catchments with excess flows cascading downstream into the next lake. But this unique combination of natural & man-made design has been completely destroyed due to unplanned growth and haphazard development. The ridges have been intermittently flattened; the slopes are leveled and obstructed; catchment area around lakes are encroached; all these eventually obstructing the freshwater inflow in to the lakes and eventually killing the lakes within the city. This is the status of all the lakes in Bangalore today.

The only hope now lies in the revival and rejuvenation lakes & water-bodies in the peri-urban areas that are drying up. These lakes / water-bodies are not yet polluted or contaminated like the ones which are within the city. The topography, landscape and related ecological features still have the potential to harvest, collect & store maximum amounts of rainwater. There are several such water bodies and lakes all around Bangalore city in its peri-urban region. By following and implementing suitable eco-restoration methods it would take about two to three years to revive such water bodies. And it would require about Rs.2.50 crores to restore one such water body. Bangalore, therefore, needs a Blue Belt if it has to sustain in future. And a strong & healthy partnership between the government & private organizations can rebuild Bangalore's depleting water resource.