Guest Blog by Manu Bhatnagar
Even as the water crisis gathers pace time is playing out a requiem for lakes and wetlands. Poor understanding of hydrology, greed driven capture of wetlands by real estate, the adoption of the shortest straight line path by infrastructure development agencies, the effort by engineers to make everything straight and neat by concretization, the plummeting of groundwater tables and the interception of free flowing surface runoff by alteration of basin characteristics are the major drivers of the rapid extinction of our waterbodies.
In February, 2017 the Supreme Court directed that all waterbodies recorded in the National Wetland Atlas of 2010-11 were to be protected and conserved. This amounted to over 201,000 waterbodies of 2 ha plus water spread area. Overall, the number of waterbodies in the country stands at over 600,000.
However, several studies across the country are recording the serious loss of waterbodies, decline in their spread, growing number of dry waterbodies and deterioration of water quality. Thus, IIT Delhi’s Centre for Atmospheric Sciences has reported a 40% loss 0of waterbodies in the National Capital Region and Quality Council of India’s ongoing survey of waterbodies in the 5 Ganga Basin States shows a loss of 25% waterbodies.
In such a context any gains ought to be celebrated and this narrative records one such positive story. In 1998 INTACH submitted to the Delhi Govt. its seminal study ‘Blueprint for Water Augmentation in Delhi’. One chapter dealt with historic waterbodies such as Hauz Khas.
The Hauz Khas was a historic waterbody carved out by Allaudin Khalji for his proximate military camp in 1298 AD. It received water from a localized catchment and the water table had been quite high. However, in the 1960s the Hauz had become dry partly out of diversions of storm water and partly due to the falling of the water table. In 1968 DDA had tried to fill the lake by first concretizing the bed but they had not been able to fill the lake and over time the concrete had crumbled and given way to vegetation.
It took 5 years of persuasion before DDA would consent to allow us to prepare a DPR for reviving the dry Hauz Khas lake spread over 15 acres. And even here the perception was that the consent was being given to quieten a vociferous and nuisance NGO.
In 2003 an MoU [worth Rs. 5.5 Lakhs] was signed for preparation of the DPR. Several investigations were carried out such as plane table survey, bathymetry, identifying the catchment area and slopes from old survey maps, investigative bores, groundwater test. The investigations showed that the bed soil of the Hauz was very porous and would not retain the rain water for more than a few days.
By now the South-west Division of DDA had become interested in the novel project and subsequently enthusiastic as well. On the recommendation of SE Mr. RK Sood it was proposed to tap the secondary level treated wastewaters of Vasant Kunj STP which flowed through the Sanjay Van Reserve Forest. A series of check dams were made in Sanjay Van to cleanse the waters further while aiding the groundwater recharge in that segment of the southern ridge. The proposals are depicted in the map below :
The DPR was ready in 2003 and the same year the work was taken up. A major hurdle came up when the treated wastewater were again contaminated by a flow of raw wastewater from RK Puram side. It was decided to isolate the treated flow from Vasant Kunj STP in a pipe in the stretch through the Qutab Institutional Area, the IIT and the Rose Garden north of Ring Road all the way to the Hauz. This was a major expense and not budgeted for. But ‘where there is a will there is a way’ or the other adage –‘find a way or make one’ resulted in Mr Sood solving this problem. Pipes ordered by him years ago in a project in East Delhi were lying unused – these were requisitioned at no cost and isolated the clean water.
But the NCERT would not allow us to lay the pipes through the drain channel passing through their campus. Here, the Chairman INTACH had to speak to a JS in the Education Ministry [his junior in the Haryana IAS cadre] who spoke to the obstinate head of NCERT to not come in the way as INTACH was only ‘obeying High Court orders’ – this worked and we could proceed. But we still had to contend with the IIT who started diverting the piped water for their own gardening. A similar reasoning put a stop to the pilferage.
At the Outer Ring Road a large valve was installed which could allow the waters [treated wastewater as well as rain water runoff] to flow in the drainage system to Yamuna or, when turned, divert the waters to the Hauz through Rose Garden.
With the duckweed blanket in position and the conveyance system complete the system was ready for operations and in April, 2004 the waters were diverted to the Hauz by operating the valve at the Outer Ring Road. Sure enough, we were excited to see the Hauz getting filled. But we were in for some sharp lessons.
Initially, the water level and spread would not build up. It took a few months before the water would really spread and fill the Hauz as the strata below the bed first needed to be saturated in order for the surface spread to build up. Subsequently, the water did fill up. However, the poor treatment of sewage at the STP rendered the water rich in nutrients and this gave rise to the explosion of an algae known as spirogyra. The algal cover prevented oxidation of the waters resulting in foul smells and criticism from the morning walkers from the posh colonies of South Delhi. We had to stop operations for a while.
In the following rains a lot of turbid water [with muddy sediment] came in and we were able to reduce the requirement of treated wastewater. We also introduced lime dozing in order to settle out some of the dissolved organic pollutants. The lake seemed to have stabilized by August, 2005.
From the fisheries department at Seelampur 150,000 carp fingerlings were transported to the lake. Guppy fish were introduced to consume mosquito larvae. Grass carps were brought from Calcutta in large oxygenated cans travelling overnight in the Kalka Express. Later, wayward residents of Mehrauli introduced the carnivorous catfish [Mangur] in Sanjay Van check dams and these floated into the Hauz and consumed most of the other species.
By 2006 end we considered the lake as stabilized. The groundwater rise could be seen in old dug wells in the deer park. Abandoned handpumps in the adjacent Hauz Khas village became productive. A family of Spot Bill ducks took up residence in the island. Ducks from drying lakes elsewhere in the city were transported to the Hauz. Migratory birds such as shovelers and coots became common while occasionally common pochards, mallards, graylag goose, kingfishers, cormorants and pied herons could be spotted.
In 2007 we were out of the picture but were recalled as the authorities had been unable to manage the duckweed lagoons and poor water quality had resulted in an algal blanket over the lake. We resorted to the then novel method of bacterial bioremediation. The bacteria breaks up nitrates and sulphates freeing oxygen thus raising the dissolved oxygen levels. The dozed bacteria compete with the algae for food and starve the algae [which are only microscopic plants] even as the nitrates are no longer available to fertilize growth of algae. As the water clears sunlight reaches into the depths of the lake enabling submerged plants to generate oxygen through photosynthesis allowing several microbes to perform their niche functions in the lake ecology.
A month long exercise showed good results with the algal turbidity greatly reduced. The results can be seen in the images below as well as the water samples drawn from the lake.
Thereafter, aerators were introduced and these were moved around particularly sited in the sun and wind shadow zone between the island and the Hauz Khas village to the east. It was noted that the open spread to the west was generally of better quality as a result of shallow waters and natural aearation. Maintenance of high water quality depends upon the source waters being of acceptably good quality, ecological processes and other in situ measures.
It has been 17 years since the Hauz Khas has been revived. Many lessons were learnt. The regular availability of treated wastewater has enabled an aquifer recharge of over 1800 million litres till now [or 250 days water supply of Delhi]. Rainfall is erratic and available for only 15-20 days in a year whereas treated wastewater is available daily. Groundwater quality, checked pre-project, remains almost unchanged a decade later. Tube well operations in the district park have curtailed owing to high water yields.
The water recharged through the Hauz is picked up by tube wells in surrounding posh colonies who would never have accepted recycled wastewater directly. Thus, the project offers a good example of closed resource cycle. The project is highly replicable in the command area of various sewage treatment plants and has shown the way for revival of most urban lakes in the country.
The story of the Hauz is also captured in a short movie on YouTube at https://youtu.be/PCTxavP1q_A.
The lake can be better maintained than it is at present but for that wetlands knowledge will have to be mainstreamed in the owning agency or else external expertise would have to be retained. We are hopeful that this will happen in due course.
Manu Bhatnagar (email@example.com),
Principal Director, Natural Heritage Division, INTACH