Saturday, June 12, 2021

 

Lalbagh Open Well Rejuvenation

Lalbagh botanical garden is a 240 acres (0.97 km2) garden and is located in south Bangalore. It is managed by the Department of Horticulture, Bangalore. There are 5 open wells in Lalbagh. Of these 3 wells have water however, water from these wells are not being used. Two of the wells were closed by filling it with waste materials.  One of the closed wells was taken for rejuvenation in the month of March 2021.  After rejuvenation of the well 5ft of water was seen indicating the presence of shallow aquifer. With a pump house next to these wells indicated that these wells were used before borewell was introduced.


To manage the flooding in the north western part of the park during the rainy season, 100 recharge wells are being dug. This will help in recharging the aquifer and also  mitigate flooding.


Location of Lalbagh, Bangalore

Say Trees approached Biome Environmental Trust to identify a well in the city for rejuvenation.  The objective was to create awareness about the connection between groundwater, shallow aquifers and open wells. Since Lalbagh sees hundreds of people every day, rejuvenating a well in such a location will meet the objectives. 

To create awareness a poster/board will be placed with information next to the well. 

This project was funded by Say Trees.



Open Wells in Lalbagh

There are 5 open wells in Lalbagh.  Of these, 3 wells (Well no. 1,4,5) have water.  2 of the wells (Well no. 2 and 3) were closed by dumping construction debris, garden waste and other waste.  It was decided to take up Well no. 2, located close to the SunDial park, for rejuvenation. The dimension of the well is 10ft diameter  and 29ft depth.


WellDigger Ramakrishna inspecting Well no. 2 for rejuvenation


After taking the necessary permission from the Deputy Director of Horticulture, well digger Ramakrishna and his team started cleaning the well for rejuvenation.


The well was filled with tree branches, leaves, stone, construction debris, paper and plastic waste.  Ramakrishna and  team worked for 8 days to remove the waste and completely clean the well. They used a crane to remove the heavy material and silt. They hit water at the bottom of the well. After cleaning and treating the well  5ft of standing clear water is observed.


Cleaning of the well


Well diggers removing the waste dumped in the well

Paper and plastic waste


        
Stone and construction waste



Tractors carrying the plastic and paper waste out of Lalbagh

Outside of the well after cleaning

8 tractor loads of plastic/paper waste were taken out of Lalbagh.  The stone, garden waste and silt was left in the garden to be used.

Inside the well after rejuvenation

The dimension of the rejuvenated well is 10ft diameter  and 29ft depth. The well can hold upto 64000 liters of water.


A perforated metal cover with a door was fixed on top of the well for safety purposes.  This also prevents leaves falling into the well.



Perforated Metal cover 



Next step is to fix the plumbing and motor for using the well water in the garden and for any other requirement.














Tuesday, March 16, 2021

Water and sanitation in Devanahalli: Drinking water supply business

 Part 5: Drinking water supply business 


Southegowdanahalli is the only location where water is available at shallower depths and in plenty throughout the year. Mr.Krishnamurthy is a successful entrepreneur running a commercial drinking water supply business since 2002. Krishnamurthy supplies 50,000-100,000 litres of water every day. He is majorly supplying water to two apartments like Brigade and other apartment.

Businessman Mr.Krishnamurthy

  • He has 3 water tankers having the capacity 12,000, 4000 and 3000litres each. Mostly 12,000litres capacity tanker is put into use(which saves on the cost)
  • For 4000litres capacity tanker Rs.400 is charged. There is no GST charged for water supply 
  • Mr.Krishnamurthy has 4 borewells at 700, 300 and two borewells at 250feet in depth drilled in 2013,2014, 2015 and 2016. Each borewell is yielding about 1 inch water. 
  •  His business is having the current demand of 50,000litres a day. Krishnamurthy is fully equipped to supply around 150,00-180,000 litres a day. 
  • The water storage sump is of the capacity 100,000litres which is at the basement of his building.
  • He is also practicing groundwater recharge from the outflows from the tankers. The recharge well is 20feet in depth. 

Basement sump


Recharge well 


  • He shifted to solar panels in the year 2014 to cut down cost incurred on pumping. Every month Rs.60,000-70,000 was the cost incurred on pumping the groundwater. After shifting to solar panels the cost incurred on pumping has come down to Rs.5000 which is mostly due to non sunny days. The capital cost on solar panels is at Rs.740,000 which can generate 6.5kilowatt of electricity. In his words, “I have recovered the capital cost on solar panels within a year in the form of cost savings on the electricity bills. I have benefited the most from Solar panels.”
  • For each borewells one hp motor is put into use.
  • On groundwater he says the surrounding 150acres has a high Groundwater table. It is ideal to tap top soil water. As the borewell goes deeper there are less chances of striking water. 
  • Every day the entrepreneur checks for TDS levels in the water where the counts were .36 and .40 when he demonstrated the testing. 
  • The entrepreneur is planning to expand his business by installing a new RO plant where he can supply bottled water. He is aiming to provide 20litres of water at a competitive price of Rs.4 where he confidently says he could still be able to make profits. 

- Rakshitha M L

Water and sanitation in Devanahalli: Honey suckers

  

Part 4: Honey suckers


Devanahalli town is entirely dependent on on-site sanitation having pit toilets and septic tanks. Devanahalli has majority of pit toilets than septic tanks. Pit toilets are made up of cement rings varying from 10-15 feet in depth. In old houses, pit toilets are comparatively bigger in size and are made up of stones. Pit emptying cycle is driven by seasons. In summers, fecal sludge is said to be more dry. During monsoons absorption of fecal sludge by the ground is said to be low. Thus pit emptying is said to be more during monsoons.

Honey suckers play a vital role in emptying, transporting and disposal of fecal sludge. There is a combination of both private and government honey suckers in the town. There is one government owned and four private owned honey suckers in Devanahalli. Government honey sucker is almost a decade old and lack the manpower meaning it gets to operate when a driver is available. The four private honey suckers are owned by Narasimha Murthy, Punith, Ramesh and Kiran. Government owned honey sucker charges Rs.1000 to empty a pit toilet and Private honey suckers charges Rs.800 on an average (price is kept low to compete with government honey sucker). A pit toilet can usually have 1000-1500 litres of fecal sludge. Honey suckers are usually of 3500-4000 litres capacity. A honey sucker can accommodate more pit toilets (3-4 pit toilets) in summer when compared to winter(1-2pit toilets). On an average a honey sucker can accommodate 1-2 pit toilets. 

Honey suckers are asked to dispose fecal sludge only in the Fecal Sludge Treatment Plant(FSTP). TMC puts fine on honey suckers disposing fecal sludge in the open fields.


Honey sucker emptying the fecal sludge in FSTP


Honey sucker operator Kiran: Honey sucker operator Mr. Kiran makes about 1 to 3 trips a day. Three is the maximum trips he makes which will be 12,000litres of fecal sludge in quantity. He says in recent years the number of rented houses are more in number and the pit toilet contains about 3000litres of fecal sludge. "If we dispose fecal sludge in open spaces TMC will fine us. If the capacity of FSTP is full, TMC asks us to dispose in the open fields more than 5kms away from the city. When the FSTP is full or far from the collection point and if farmers are not taking fecal sludge we dispose of FS in open farm fields, mostly when the crop is harvested so it also helps the future cultivation. I think the capacity of FSTP is very less."

Honey sucker operator Punith: Mr.Punith's honey sucker is having 6000 litres of capacity. He mostly takes grey water from the commercial plots which is allowed to be dumped in farm fields. According to Punith, "the collection tank has just 5000 litres capacity. It takes more time to empty my honey sucker in the FSTP. I have to wait for one to two hours just to unload. I have to be competitive in my business, I cannot afford to say no to calls I get from households and thus I have no other choice to find a dumping place elsewhere after TMC limits. FSTP is a good initiative but it is not executed properly. There is a strong need to have big sumps."

Honey sucker operator Ramesh: Mr.Ramesh is a 45year old honey sucker operator who mostly serves within Devanahalli town. According to Ramesh, "We cannot find an open space to empty the fecal sludge. People question us if we dump in open spaces. During the rainy season it becomes all the more difficult. Thus having a formal disposal site helps us. FSTP capacity is very less. Rajkumar asks honey suckers to wait or to come back after an hour if both the tanks are full. Least it should accommodate 8 trucks. If FSTP are created in other places like in Chikkaballapur it helps us. "


- Rakshitha M L

Water and sanitation in Devanahalli: Fecal Sludge Treatment Plant


 Part 3: Fecal Sludge Treatment Plant


Devanahalli Fecal Sludge Treatment Plant is the first of its kind in the country. FSTP is functioning from the year 2015. FSTP is implemented by Consortium of DEWATS Dissemination (CDD) Society with the funding from Bill and Melinda Gates foundation. According to CDD's report "Insights from Fecal Sludge Management in Devanahalli", FSTP was implemented to facilitate scientific dumping of fecal sludge and to end open dumping of fecal sludge causing health and environmental hazards. FSTP converts fecal sludge into co-compost which is sold to farmers.

CDD was looking after FSTP for a duration of one year. From 2016 to till date TMC is managing the FSTP entirely with technical guidance from the CDD. The plant manager, civil engineer is from the outsourced private company who was appointed in 2019.

ABS system

 Co-compost

Finances of FSTP: The capital cost of FSTP is Rs.8,000,000. The land belonged to TMC and thus capital cost excludes the land cost. Major cost of maintenance of FSTP is on paying the manpower. FSTP has one manager, one plant operator and 3 workers collecting wet waste. Rs. 15,000 is the salary paid to four workers. This makes about Rs.180,000 per annum. 


Operational capacity: According to CDD's report FSTP is designed to treat 6000litres of FS in a day and FSTP is currently operating at 1/3rd of its capacity. According to TMC in a day 3000litres of fecal sludge is collected in the FSTP (this could be a single trip or 2-3 trips having around 1000litres capacity). In 2020, Government owned honey sucker has just made 12 trips a year whereas private owned honey sucker made 333 trips. 


Co-compost: Fecal sludge compost is mixed with Municipal wet waste in 1:3 ratio to create co-compost. Co-compost is suggested to balance the Nitrogen level where E-Coli and Fecal Coli growth (could grow when applied to soil) can be permanently stopped when mixed with wet waste. CDD experimented the efficiency of co-compost by applying it on to the plants grown in the FSTP premises. Only after the results were proved to be good co-compost was sold to the farmers. Co-compost is sold to farmers at Rs.7 per kilogram. Currently there are 10-12 farmers buying co-compost in smaller quantities and 5-6 farmers buying in tons. There are mixed opinions from farmers using co-compost, few find the co-compost is not giving good results and few say they are benefitted. There are farmers who are reluctant to buy co-compost because it is fecal sludge and famers who bought co-compost without being aware it is fecal sludge never returned to buy. Co-compost is generally used for rose and grapes which are best suited as the farmers suggest. Yearly 200-250 tons of co-compost is generated. When FSTP was just started, advertisements on co-compost and FSTP was made using print media and on auto rickshaws. 


Monitoring of FSTP: TMC has been monitoring FSTP for almost two years. There are no challenges currently faced by TMC in maintaining the FSTP because of the efficient worker Mr. Rajkumar. Rajkumar has been working in FSTP since its inception. He brings every small or major issue into TMC's notice which reduces TMC’s burden. Environmental Engineer Miss. Nethravathi gives all the credit to Rajkumar for the success of FSTP by saying "if Rajkumar wasn't there we would have neglected FSTP in all the bundles of works we handle."TMC is now planning to train other worker to reduce the dependence on only one worker.


Records: A ledger is regularly maintained by Rajkumar which contains all the details of honey suckers. The details include, date, government or private, name of the driver, contact number, quantity of fecal sludge and its sludge and water ratio, type of pit toilet and dept, Valve one or two, time of flow to BioGas digester, weight of solid waste in kg etc.


Wastewater disposal: Commercial units have created big tanks to hold grey water in the areas where there are no storm water drains. Wastewater(grey water) from these tanks are emptied by honey suckers and allowed to discharge in farmers fields since it has nutrients beneficial for agricultural fields. 


TMC on-field checks: TMC makes frequent field visits. TMC officials stop the honey suckers and check the type of sludge (grey water from commercial units or fecal sludge) and where they are emptying frequently.


Penalty on honey suckers: TMC is putting fines on the honey suckers who are disposing fecal sludge in open spaces. Honey Sucker operator Mr.Ramesh was fined Rs.5000 for dumping in a farm field. 


Biogas Digester: Biogas Digester has been very inefficient since day one. it was supposed to fulfill the cooking needs of Rajkumar. It would take two hours to cook rice using the limited biogas generated. Rajkumar approached CDD and asked them to provide an alternate fuel source. He has got a gas cylinder from CDD and cooking and now he says, he has put the air out option in the biogas digester always open which would generate no gas!


Wet waste: Wet waste is collected from 10 wards currently. FSTP does not aim to be a complete solution for wet waste and thus total wet waste generated is not fully utilized in FSTP. Currently there are 4 complete wet waste composts and one partial compost under TMC.

- Rakshitha M L

Water and sanitation in Devanahalli: Treated wastewater


 Part 2: Treated wastewater


Minor Irrigation Department is pumping Treated wastewater from Sewage Treatment Plants to KC Valley where lakes in Kolar and Chikkaballapur region are filled up. This was implemented as a drought mitigation strategy which enables groundwater recharge. Similarly treated wastewater from STPs in HN valley is also been pumped to fill up lakes. Devanahalli is receiving treated wastewater from the mid of 2020. 

Currently treated wastewater is been pumped to Doddakere, Sihineerkere and Bettakote lakes to name a few. MID was pumping TWW in alternate weeks when it just started pumping. According to the water man of Devanahalli town, MID is aiming not to allow the lakes to go dry. MID monitors the water level in the lakes and if the water level is less than 50% it pumps TWW immediately. 

Siyineerkere lake

 Doddakere lake was slightly de-silted before pumping treated wastewater and the bund was strengthened by the TMC. Sihineerkere lake's waste weir must be repaired and bunds must be strengthened. TMC says yield of borewells near Sihineerkere lake have increased drastically. TMC is yet to check the borewells near Doddakere to find out if there is an increase in the yield.


Farmers perceptions on treated wastewater: Farmers are very happy about the entry of treated wastewater. Farmers have noticed the increase in the yield of borewells. Treated wastewater has led to the increase in yield of borewells and open wells have seen water after decades.

In the words of farmer Mahesh, " Open wells of Devanahalli haven't seen water since two to three decades. After the entry of treated wastewater open wells have seen 30ft water. Borewells yield has increased twice. It is very important Doddakere lake fills up completely. If Doddakere lake is full it benefits all the open wells and borewells of Devanahalli. Recharge zone of Sihineerkere lake is limited to very few zones. We are extremely happy to see water in our open wells. If Doddakere lake is full my open well will overflow. Treated wastewater benefits all the farmers and it also reduces migration."


TMC's open wells: here are two open wells within 100m from the lake belonging to Town Municipal Corporation. These two open wells went dry for two decades. The open in the shape of a lock is referred as heritage well. Heritage well is yet to be cleaned and desilted. The other well is cleaned up, desilted and stones are strengthened.

         
          Heritage well

         
           Cleaned up open well 

Pump test and water quality tests were conducted to this well. According to the pump test the aquifer yields about 70,000-80,000litres per day. Water quality test results indicated the water is fit for drinking with little chlorination. The current water level is at 12ft from the ground level. It is expected to increase as the water level in Sihineerkere lake increases. Water level in the heritage well is at 16ft from the ground level. Yes, the measurement might vary since the lake has solid waste accumulation.

- Rakshitha M L

Water and Sanitation in Devanahalli: Water Supply

 

Part 1: Water supply


Devanahalli is a small town of Bengaluru Rural District of Karnataka.  Devanahalli is located at a distance of 40kms from Bengaluru. The town is a Town Municipal Council having the population of 28,051 as per 2011 census (currently 35,000 according to TMC). The town is divided into 23 wards. 

Devanahalli is popular for Kempegowda International Airport which geared the town growth. Migration to the closest Bengaluru in search of better employment opportunities is a common phenomenon. Yet Devanahalli is mainly agriculture driven. The town falls into semi-arid to arid climatic zone and also considered to be drought prone. Flowers, vegetables, spinach and grapes are the major crops grown. Long term horticulture crops are not popular in the town. The produce is sold at the nearest Bengaluru markets. Farmers complain of not getting wage laborers since daily earners are working in commercial units, Airport or moving towards Bengaluru city.

 



Water supply: 

There is no perennial source of water supply in Devanahalli and groundwater is the only source of water supply to the town. Town Municipal Council (TMC) supplies 1,200,000liters of water a day at 55-65LPCD. TMC supplies both sweet and saline water to households. Sweet water is supplied once in 8 days and saline water once in 2 days. TMC is not supplying water for commercial units in the town. TMC is supplying water for government schools in the town and not private schools. TMC is not supplying water to ward number 22 and 2 since every household has a borewell.

Water tankers: TMC owns 2 water tankers and there are 5 private water tankers. Private water tankers are required to take the permission from TMC before operating. 

Borewells: TMC has drilled 112 borewells out of which 32 are not yielding. Devanahalli is dominated by saline water. Borewells around Sihineerkere lake (Sweet water lake) are the major source of water for the town. TMC has 8-10 borewells in the radius of 500m from the lake to meet the drinking water needs of the town. TMC has drilled 18 borewells in 2019, 8 borewells in 2020 and planning to drill 9 borewells in 2021.

RO Plants: RO plants are used to treat drinking water. There are 13 decentralized RO plants. One RO plant is provided for every 3 wards.

Water tariffs: Devanahalli TMC charges water tariffs to the households. Per month a nominal amount of Rs.120 is charged. Rs.4,800 is the deposit need to be made in order to take the water supply connection. 50% of the population is served for free without levying the water tariff. 


- Rakshitha M L

Wednesday, January 27, 2021

Devanahalli and its water: Then and Now

The Devanahalli town located very close to the Bangalore International Airport (34 km from Bangalore) is home to around 30,000 people. It is also 

the main town of Devanahalli Taluk in the Bangalore Rural district. The town is of historical significance. The town is still a sought after location for

 its old temples, forts dating back to the 15th Century. The town is also the birthplace of Tipu Sultan, an erstwhile ruler of the Kingdom of Mysore 

from 1782 to 1799.

Locating Devanahalli

Traditionally, Agriculture has been practiced in Devanahalli and it is the main livelihood to many communities in the town. Devanahalli is also home

 to a number of Keres, open wells and step wells/Kalyanis which are of cultural and heritage value. They were also the traditional water systems locally. 

This region has historically been dependent on the network of cascading tanks, step wells and open wells to tap local groundwater for different water 

needs. Tanks served the purpose of both groundwater recharge and as irrigation reservoirs. All domestic needs and agriculture needs are served by 

Open wells and step wells/kalyanis used for religious and cultural purposes. 

 

Within the town Shineeru kere or “Sweet water lake” and Doddadda ammani kere or “very big lake” are two major water bodies. These water bodies 

serve the drinking, domestic and agriculture needs indirectly. The two lakes recharge the groundwater as well. To access this groundwater, almost 

every household and farmers built open well as a decentralized water management system. Devanahalli also had few public open wells to serve the 

needy. These public open wells also had a kundi/small tub adjacent to it to withdraw water from well and pour into the tub to use for their day needs. 

In few of the public places/places of importance, a traditional water distribution system/ Silendra near the dargah is places which served water for

 travelers who waited here to board a vehicle or for rest.

Identified open wells in Devanahalli

Open well

Step well

Kundi/ Tub

Silendra/ Water distribution system for travellers

With a new wave of urbanization proposed by Bangalore International Airport Area planning Authority (BIAAPA) in the last decade, Devanahalli is 

planned to be the centre of new developments. It would be surrounded by large Software, Hardware, Financial Services and Aerospace special 

economic zones (SEZs). Today, its municipal boundaries cover an area of around 16 sq km but it's set to expand in the coming years. This 

development will also lead to transition from agricultural lands to real estate – currently mostly into residential properties. Along with the 

landscape transition, the region will also experience transition in its water scape. The catchments of the lakes are already disturbed affecting inflows 

into the lakes. Groundwater tables have also fallen drastically in the region, and in general this area experiences water scarcity.  

 

Farmers therefore have invested in drilling deeper bore wells in many places, often without adequate yields. Beautiful open wells with masonry stones 

dot the landscape, but are mostly dry and filled with solid waste today. The area has also seen investments by farmers in drip irrigation systems to 

conserve the water. The town is managed by local municipality i.e. the Town Municipal Council (TMC). The individual households of the town are now 

connected with water pipes to receive municipal supply from public bore wells dug by the TMC or from tankers and few are connected with their own 

borewells, changing the water paradigm from decentralized water management to centralized water supply. Eventually, to sustain the growing water 

needs, deeper aquifers replaced traditional systems as a primary driver for irrigation and domestic consumption. Though, these sources provided 

short term relief  but drastic exploitation of groundwater was soon visible. Every year 8-10 new borewells are dug to meet the growing water 

demands of the town putting shallow aquifers out of the imagination. This is the best time for Devanahalli town to realise the role open wells have 

played over the centuries in management of water. Can we look at bringing back this water heritage of the town which were crafted exquisitely to be 

called work of art? Stories are already emerging from the town of formal and informal enterprises realising the importance of shallow aquifer. 

 

In the next few blogs we will talk about small stories on the impact of urbanization on shallow aquifer in Devanahalli. 



Monday, January 25, 2021

Puttenahalli-Yelahanka Lake Report 2020

  

Summary

Puttenahalli-Yelahanka Lake is spread over 34 acres in North Bangalore.  Known for its bird population and bird diversity it was declared as a “Bird Conservation Reserve’ in 2015.  For a long time, with heavy inflow of sewage into the lake water quality had deteriorated. The Forest department, Citizens, Institutions and Ornithologist came together to design and rejuvenate the lake to help restore the lake to its original glory.  When we visited the lake in August 2020 the rejuvenation process was complete.


The lake's main source of water was a combination of rain and treated sewage.  It receives runoff from its upstream source, Attur Lake.  However, due to urban growth this source had become a trickle and very little run-off reached the lake from 2012.  Instead, wastewater, predominantly sewage began flowing in and filled this Lake.  From 2013 plans were initiated first, to remove the sewage sludge from the lake and second, provide for an alternative source of water to keep the lake filled throughout the year.  To achieve this, a diversion drain for sewage was designed and executed to divert incoming sewage into a 3m wide diversion drain that runs along the South and East side of the lake.  In this way primary sewage is prevented from directly entering the Lake.  A runoff diverting sluice was designed and built upstream at the mouth of the lake so that only storm water or heavy runoff can enter the lake upstream.  Whereas the daily flow of sewage continues to flow in the diversion drain.  The stormwater or runoff entering the lake through this sluice is allowed to flow on a boulder and reed bed so as to trap the plastics and other floating wastes and thus allowing only clean water to enter the lake during the rainy season.  The work on restoration began in 2016 and was completed in July 2018.  As a part of the above restoration, a ‘Passive Conditioning Plant’ was constructed at the South East corner of the lake and commissioned with a capacity of providing one million liters of good quality water into the lake to compensate for evaporation losses and fall in the water levels in the Lake.  Wastewater from the diversion drain is channelled into this plant which then gets treated before it enters the lake. The quantity of wastewater entering the plant can be controlled by the balancing weir and a sluice gate.  Water is treated and let into the lake to replenish the water lost due to evaporation, mainly in summer while also allowing a defined quantity of nutrients for supporting primary algal biomass to grow and support a high fish density for the birds’ food.


Location with series of the lake


Plan of the lake

 A                                                                                                        A’

Conceptual Section AA’



Overview and Observations


Puttenahalli lake is located in North Bangalore in Yelahanka, on the way to Doddaballapura, near KPTCL office.


Puttenahalli Lake

  

Custodian

Forest Department

Lake Area

34 acres

STP 

Passive Conditioning Plant

Wetlands

Yes

Upstream lake

Attur Lake

Downstream lake

Yelahanka Lake


The Forest department which is the custodian of the lake, in partnership with YPLBCT (Yelahanka Puttenahalli Lake and Bird Conservation Trust) lake group overlooks the maintenance of the lake in consultation with water experts from IISc and Bird experts from GKVK. The entire lake is imagined as an urban forest, designed to keep human interference to the minimum.  The walking path covers only the northern part while the Southern and Eastern and Western boundaries do not have public access.  There are benches placed and gazebos planned for photographers and birdwatchers to pursue their interests.  The lake is designed to be generally shallow in nature with a maximum depth of 8 feet with three depth zones keeping in mind different types of birds will inhabit and benefit from the shallow (waders), mid-depth (swimmers) and two metre deep (diving birds) zones. The depth of the lake increases gradually from 2ft to 8ft West to East. 


YPLBCT is an active citizen lake group.  They have various activities like Idol making for Ganesha festival, Kere Habba, Bird census at the lake to encourage citizens to get involved with the lake.


Inlet


There are two sources of water for this lake.  As sewage flows along the run-off channel, there is a need to separate the daily flow of sewage from the rain-water entering as run-off from upstream.  Upstream of the Lake, the daily flow of sewage is let into a diversion drain that flows along the southern boundary for nearly a kilometre and then flows past the eastern bund towards the Yelahanka Lake.  At the mouth of the Lake, there is a diversion system such that when the flow is low and the water level in the run-off channel is low, it flows into the diversion channel.  However, when there is heavy runoff from heavy rain and the water level in the drain is high, a large part of the runoff flows past the barrier into the shallow end of the lake over a boulder trap that arrests silt and debris.  On the other hand when there is no rain and the water levels in the lake is low due to drying up, the sewage is let into the PSTP (passive sewage treatment plant), gets treated to bath water quality and then flows into the lake at the deep end.  A balancing weir is built slightly downstream of the PSTP inlet such that water is taken into the lake only if the water level in the lake is low.  When the Lake is full, no sewage enters the PSTP and all the sewage flows down the diversion drain.  Thus fresh water from run-off enters the Lake upstream at this mouth at the shallow end while sewage is taken in only when the Lake water level is low through the PSTP at the deep end of the Lake.  The diversion drain prevents the sewage directly entering the lake. There are sluice gates at both the inlets to control the inflow of water that may be needed during maintenance of Lake.


Sluice gate at the Southwestern side of the lake


Passive Sewage Treatment Plant (PSTP)


A passive conditioning plant with a capacity of one million liters per day (1MLD) is constructed in the lake at the deep end on the Southeast corner of the lake abutting the diversion drain.  A balancing weir helps control the intake of sewage into the plant. The balancing weir lets sewage to flow into the PSTP only if the water level in the lake is low and the Lake is drying up.  The passive conditioning plant has 3 zones or tanks.  In the first zone incoming sewage is subject to anaerobic digestion and most of the organic matter in the sewage is converted to biogas while a small part of the digested material, predominantly anaerobic bacteria settle down as sludge.  The treated supernatant stripped off the digestible organic material, now flows to the next zone where it is treated with algae in two stages for further purification.  In the second tank, specialized algae called Euglena are allowed to grow and these feed on the suspended bacteria still remaining in the water coming out of the anaerobic digester.  After a day of treatment by Euglena in this tank, the clarified water enters the second algal tank.  This tank permits a high growth of algae and in bright light, due the rapid photosynthesis, the pH of the water rises to about 9.0 and supersaturating the water with photosynthetically derived oxygen.  These two phenomena of high pH and supersaturated dissolved oxygen in water firstly kill most of the potential pathogens (if found) and second remove a large part of the nitrogen and phosphorus from the water.  The treated water at this stage reaches recreation quality or wild-life quality and after this the water enters the lake.  The treatment and filling up the lake with treated sewage is necessary to replenish water lost due to evaporation and during summer and prevent the lake going dry. This will ensure water at the lake all through the year and helps to recharge the groundwater level in the vicinity.  The water quality is so managed so as to provide for food for the higher levels of fish numbers maintained to attract more water birds.


Passive Sewage Treatment Plant

Outlet


There is one main outlet or spillway at the Northeast of the lake.  Lake water overflows from an overflow weir.  The diversion drain diverts sewage flowing into Puttenahalli lake and flows along its boundary without allowing it to mix up with the freshwater in the Lake.  The excess water from the lake falling over the spillway as well as the diversion drain join after crossing the lake and flows into a reed bed before entering the Yelahanka lake. 


Outlet


Islands and Bird Nesting Sites


There are 4 mini islands created at the lake. Two islands existed prior to restoration and two more were created during the restoration process.  The islands are planted with trees for creating bird habitats keeping in mind the roosting and nesting activities.  A gazebo is being built opposite these islands for photographers and bird watchers for their activities. There is no direct access to the island and therefore birds roosting and nesting remains undisturbed.


Island

There are seatings provided along the pathway. 


Benches


Livelihood Activities


Various livelihood activities are being added slowly to sustain people dependent upon the Lake.  Grass cutters are allowed into the lake to cut grass and Alternanthera and take it for feeding their cattle. This helps keep the weed level low in and on the banks of the Lake and also reduce human-snake encounters.


A Grass cutter at the lake

Fishing


The lake has been seeded with four kinds of fishes while catfish has inadvertently entered this lake from upstream lakes.  Controlled fishing has been taken up to reduce the population of large fish (more than half kilo), so as to maintain fish at sizes appropriate for birds to feed on.  Only large fish are allowed to be removed from the Lake through use of large nets and any small fish caught are returned to the Lake.  Large fish usually prey on smaller fish as their main food and thus need to be selectively removed.  Some extent of emergent weeds need to be maintained as fish shelters to maintain the fish population especially of the fingerlings and hatchlings.  However, there is a need for a more scientific management of the fish population and types in the lake to favour bird feeding.  Studies are on to show that fish are breeding and growing the lake. 


Biodiversity at the lake


Puttenahalli lake was declared as a ‘Bird Conservation Reserve’ in 2015.  The rejuvenation and design for the lake was planned and executed with this in mind.  After the rejuvenation, the lake sees many birds roosting and nesting.  Bird Surveys are carried out twice a month and species sighted are recorded and discussed with the management group as well as interest groups.  There are a lot of insects such as butterflies and dragonflies, beetles and wasps that supplement various other bird feed such as Myna, bee-eaters, etc.  One could also see different species of plants around the lake. For a complete list please visit YPLBCT website.


Below are few pictures of the biodiversity that we noticed


  1. Birds


Coots


Purple Swamphen


There are over 120 species of birds spotted at the lake; Coot, Purple moorhen, Spot billed ducks, Pond heron to name a few.  We observed Coots nesting near the island.


  1. Flora




Few plants that we observed are Kadamba tree, Canon ball, Ficus, Acasia, Rain trees, Jamoon tree, Honge, Bamboo.  Some of the wetland species were Alternanthera (alligator weed), Typha, Ipomea (morning glory), Vetiver, Colocasia, Cyprus, duckweed, Knot weed, Wolffia, Bamboo to name a few.  Wolffia size depends on the amount of ammonia in the waterbody. Less ammonia encourages Wolffia-major to grow and more ammonia encourages wolffia-minor to growThe same plant behaves differently on soil and on water.  Taking knotweed as an example, the stem of knotweed is hollow when in water and solid/filled when on soil.


There are date palm trees on the island which have mile-a-minute creepers covered over it with beautiful pink flowers. 


Duckweed at the outlet

As indicated earlier, the Lake was designed to have three depths to meet the needs of three types of birds.  At the shallow end, it was observed that the alligator weed was growing in abundance and has created a niche for various types of swamp hens (purple moorhen, etc).  On any given day there are over a hundred swamp hens to be sighted.  They also created nests among these weeds and are breeding extensively.  The occurrence of these alligator weeds is due to the legacy sludge and the difficulty during lock down for Lake maintenance and weed removal.  We were told that this excess growth will slowly subside once the sediment stabilises and submerge vegetation sets up, which then takes care of the weeds.  It can take up to 2 years to see the effect of the restoration.


  1. Fishes- 

The fishes have been reported to include Catla, Tilapia, Rohu, Snake head fishes, Guppies and Cat fishes.


  1. Insects

Grizzled Pintail



Common Picture Wing

Many butterflies were observed. A picture of one of the Blues is below.


Blues