Lessons from a reservoir
A little water in a once mighty reservoir on the river Arkavathy
|Some insights on how water requirements are catered to and how projects such as Hessarghatta become irrelevant over time with climate change|
Those who do not learn from history are doomed to repeat it – George Santayana.
Located to the west of Bangalore at a distance of 24 km, picturesque Hessarghatta is home to one of the first city water supply schemes located outside of a city. It is more correct to refer to the Hesserghatta reservoir as a ‘once upon a time’ water lifeline for Bangalore rather than a current lifeline. It has been given up as a reliable source by the Bangalore Water Supply and Sewerage Board (BWSSB) the institutional water supplier to the city, since it no longer reliably fills up.
Looking at the history of the reservoir and the water supply scheme for the city will give us some insights as to how water requirements to a city are catered to and how projects become irrelevant and have to be abandoned or are given up in the chase for water. With climate change staring at us, the Hessarghatta story has many lessons for urban India.
A bund was probably built in 1532 on the Arkavathy, creating the Hessarghatta tank which served as an irrigation tank for centuries. It was comprehensively redone in 1894 to become the major water supplier to Bangalore. For the first time the city had reached out for water beyond its tanks such as Dharmambudhi, Sampangi, Ulsoor and Sankey and local wells. A brick aqueduct brought water to a distance and then steam pumps were used to pump it up to Chimney Hills from where the water flowed by gravity to the Jewel Filters at Malleswaram.
The then Dewan K. Sheshadri Iyer played a key role in the development of the Hessarghatta water supply scheme which came to be called the Chamarajendra Water Works, as did the then Chief Engineer of Mysore M.C.Hutchins. It is now difficult to believe that Hessarghatta was chosen for reasons of long-term availability and purity of water.
D.K.Subramanian, in his seminal essay ‘Bangalore City’s water supply – A study’ mentions that the Chamarajendra Water Works was meant to deliver 55 litres of water per person per day to a population of 250,000 and the filtered water supply started on August 7, 1896.
Till the commissioning of the Thippagondanahalli reservoir in 1932-33, Hessarghatta remained the largest supplier of filtered water to the city. The reservoir last filled up in 1994 and year on year collects less and less water and therefore has gradually been given up as a reliable source of water for the city.
A reservoir with a catchment area of 189 square miles and with 184 tanks in its upper catchment and supplying 36 million litres per day of water becoming virtually redundant indicates the necessity for managing the catchment appropriately and ensuring good practices for free flow of water. Bangalore simply moved from Hessarghatta to Thippagondanahalli and from there to Torekadinahalli for Cauvery water.
The brick aqueduct and volute siphon are amazing water heritage structures fit to be preserved and displayed. It reveals the skills of our water engineers in being able to design and build beautiful systems. They now lie derelict. We need to revive and proudly display them for our future generations.
We need to understand the changes in the catchment of the Arkavathy and look at reviving the river and regenerating flows. The Hessarghatta reservoir has the capacity to supplement Bangalore’s water requirements at a far cheaper cost than any other. It makes ecological and economic sense to look at its revival. In learning from history the right lessons lies water wisdom.
Begun in 1891 and completed in 1896, the Hessarghatta reservoir was designed to provide water for a population of 250,000 people in Bangalore. This anticipated population was reached in 1921 itself and therefore a new project had to be thought of to augment supply of water to Bangalore. The monsoon failed in 1924 and 1925 and the 1926 monsoon too arrived late, leaving the Hessarghatta reservoir almost dry and causing a shortage of water in the city.
Prof D.K. Subramanian reports that by October,1925, tanks upstream were breached and drained to fill up Hessarghatta and provide relief to Bangalore city. Dodda Tumkur tank, followed by Kolathur and Mdure tanks, were breached to bring some water to Hessarghatta. Perhaps for the first time, in a sort of payment for ecological services, the city compensated the farmers dependent on the three tanks for the loss of water and irrigation.
A committee was constituted under Sir M.Visvesvaraya to find a permanent and reliable source of water for Bangalore. The committee suggested the construction of dam across the Arkavathy itself but further downstream after the confluence of the Kumudavathi at Thippagondanahalli (T.G.Halli). The reservoir came to be called the Chamarajendra reservoir and the water to Bangalore started flowing from it in 1933.
The Bangalore Water Supply and Sewerage Board (BWSSB) website tells us that the original storage of water in T.G.Halli was 2364 million cubic feet and subsequently it was increased, by raising the height of the reservoir wall, to 3038 million cubic feet. Water was pumped to the city in stages. In the final stage around 135 to 140 million litres of water was pumped from the reservoir to the city daily.
One consequence of shifting from Hessarghatta to Thippagondanhalli was the height to which water had to be pumped to reach Bangalore. From Hessarghatta the head to which water had to be pumped to Bangalore was 131 metres and required only a single stage pumping from Soladevanahalli. From T.G.Halli however, the head was 234 metres and necessitated two-stage pumping with an intermediate pumping station at Tavarekere.
The catchment area of T.G.Halli, 1453 square kilometres, represented a substantial increase over the Hessarghatta catchment area of 474 sq. km. The catchment area was declared a regulated zone under the Prevention of Pollution Act in 2004 following a public interest petition in the High Court of Karnataka. Industrial waste discharge and construction therefore are regulated in this catchment area.
Both the quantity and quality of inflow into the T.G.Halli reservoir is on the decline and it is unlikely to be considered a reliable source for Bangalore in the coming decade.
While the catchment area to satisfy the city’s thirst keeps on increasing, the water footprint too increases. In the absence of a catchment management institution no planning, coordination and investment is done to ensure that the quantity, reliability and quality of flows in our rivers and reservoirs are maintained. In the absence of any form of regulation of water withdrawal in the catchment, unhampered withdrawal of water from tanks and groundwater for irrigation of water-intensive crops leaves rivers and reservoirs dry.
Constituting a river basin authority for rivers such as the Arkavathy will enable all stakeholders to participate and a reasonable allocation made to satisfy all needs. Unless such an institution is brought into play, these reservoirs will remain as mute monuments to the cities’ thirst and our mismanagement of our rivers and waters. Conflicts around water will become inevitable. Learning from history and taking steps to prevent repeated failures is water wisdom.
As a consequence of trying to understand the role of Hessarghatta reservoir in Bangalore’s growth, the Bangalore City Project (http://bcp.wikidot.com/) proposes to organize a walk on the reservoir bund. on December 6. The walk will look at the reservoir and its current state. A siphon provided as an overflow mechanism is another unique structure to be observed. Remnants of a brick aqueduct and a small temple on the bund will also be seen. Experts will explain how the reservoir functioned.
If you want to participate in the event please call Sandhya at 080- 2364 4690 or send an e-mail to firstname.lastname@example.org. We have 35 limited seats and the seats will be filled on a first come first serve basis. We propose to organize a bus from Cubbon Park to Hessarghatta and back. You should bring along drinking water and some snacks. The walk will be about 3 km long and will take about two-and-a-half hours.