12.1 Water and Waste Water
The water availability for meeting the future demands of Bengaluru for the master plan period and beyond was one of the concerns expressed by some citizens during the public consultations. By all accounts, the availability of surface water (synonym as Cauvery water) has not affected the growth of city (in terms of population and spatial). Having said that Bengaluru is at the situation where the only surface water source available to city (River Cauvery) is legally getting exhausted and dependency on ground water is growing. Will the city continue to grow? probably yes – for the fact that Bengaluru has become self-sustaining economic growth centre in entire state of Karnataka. Even if the policy decision is taken to reduce the pressure on Bengaluru by developing counter magnets, the real impact would only be visible after decade or two, provided all policy initiatives are implemented in time bound manner.
Water would be required for future population in Bengaluru – during the master plan period (2031) and beyond. It is indeed a fact that city is to face water shortage in future even after having exhausted the only surface water source, thereby increasing the dependency on ground water much more than today. The situation is likely to persist in future, the only difference being the spatial impact. The water is likely to be available and supplied to entire of BBMP by master plan period, it is the adjoining villages with Bengaluru Metropolitan Area, that are likely to get urbanised over next 15 years. How we reduce the water demand and manage the water demand is going to be most important aspect in utilising existing resources to providing safe drinking water to fellow city residents. The implementation of dual pipeline system and use of recycled water for non-potable activities for all future developments is likely bring substantial reduction in potable water demand, thereby dependency on resources. Further, social acceptability of use of recycled yet potable water would completely change the water dynamics in the city. However, this is possible only if the of water supply and sewage system covers the entire planning area.
Located at 950 Mean Sea Level Bengaluru is only metropolitan city which is not abutting to any major surface water source (River). Bangalore Water Supply and Sewerage Board (BWSSB) formed in 1964 under BWSSB Act, 1964 is mandated to provide water supply and sewage systems primarily within the BBMP (708.5 sqkm). However in the Bengaluru Metropolitan Area (admeasuring 1294 sqkm), in addition to BBMP, there are 51 Gram Panchayat’s (with 251 villages having spatial extent of 583 sqkm) served by Panachayath Raj Engineering Department (RDPR/ PRED). At present BWSSB is extending the water supply and sewage network to entire BBMP area and is expected to complete the works by 2021. However, there is no coverage of water supply and sewage network in many areas already urbanised and under process of urbanisation outside the BBMP Limits. These areas are expected to get further urbanised by 2031 with planned development as envisaged under Revised Master Plan - 2031. It is therefore recommended that BWSSSB provide support to RDPR in planning for water supply and sewerage network for entire BMA, for the fact that existing/ planned systems
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within BBMP will have to be integrated/ extended to villages outside BBMP. This is to help in designing and implementing the integrated networks across BMA.
As per Census, BBMP has a population of 8.4 Million (93% of BMA) whereas the rest of 251 villages together hold 0.7 million persons, thus a total of ~9.1 million in BMA. The population projections for RMP 2031 suggests that population within BMA is expected to reach ~20 million by 2031, thereby, making Bengaluru the third most populous city in the country.
At present BWSSB is withdrawing about 19 TMC of water (1470 MLD) from Cauvery to meet city’s water demand. The Plan/ work is on for getting additional 10 TMC (775 MLD) of water as accorded by the Cauvery Tribunal to meet the water demand for BBMP area alone. Thus, altogether about 29 TMC (2250 MLD) of water is available for Bengaluru from Cauvery. Though Unaccounted for Water amounts to 46%, the actual water losses (transmission, leaks, treatment and distribution) are around 15-18%. Also, network coverage (both water supply and sewage) in the city is limited and work is in progress to get entire BBMP covered by 2021.
The water demand has been established considering 135 LPCD supply to the population. Non-domestic water demand for potable purposes has been established considering 45 lpcd for estimated work force. Equal amount of non-potable water has been considered for non-domestic sector to establish the total non-domestic demand. The net water demand including water demand for non-domestic activities has been estimated at 3639MLD for the projected population of 20.3 million for BMA by 2031. The net demand of 3639MLD translates to the total gross water requirement for BMA at 4282 MLD considering 15% losses towards transmission & distribution.
As mentioned earlier, dual pipeline system for use of recycled water would reduce the overall water demand for potable water. If the water supply is split (within plot/ site) into two – potable (@90 lpcd) and non-potable (45lpcd) then the water demand for potable water can be reduced by 865 MLD. However, still there will be water shortage of about 862MLD [refer table 2]. This water shortage likely to be met through Ground Water, thereby increasing the dependency on ground water from present level 677 MLD to 862 MLD (about 27% (185MLD) higher than present levels). It may be noted that due to change of land use from Agriculture to urban activities within BMA, the water withdrawal for current agriculture activities to the tune of 100-150 MLD would be available for urban activities. This is with the assumption that present over draft will continue. Thus, the status of ground water dependence in 2031 would be of the similar scale as it is at present.
To meet the future water demand following are the master plan suggestions:
Providing Infrastructure across the Planning Area: Being a public utility, providing water to the public has a vital interest in its functioning and wellness of the society. More than 27% of water supplied by BWSSB is among the BPL and EWS of the society and is provided free of charge. BWSSB has coverage of 575 sq.km area out of 710 sq.kms of BBMP. The rest 135 Sq.km under 110 villages is expected to be covered by 2021. However, rest of the planning are outside BBMP are not covered by BWSSB, and it is imperative to improve the coverage to not only within BBMP but also in villages outside BBMP falling within BMA. It is therefore recommended to institutionalise the planned water supply and sewage network out BBMP as well to reduce the dependency on ground water.
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Dual pipe line for drinking and other purposes for the newly planned areas and additional population. On implementation of Dual pipeline, Government has to take measures to supply Cauvery water for all the purposes for population expected to be living in the BBMP in existing establishments and for only potable purposes for the population residing in any new developments in BBMP area which need to be developed on the basis of zero liquid discharge policy. Similarly, dual pipeline system shall cater to additional population expected to be residing in 251 villages of BMA with only potable water demand being supplied by Government infrastructure. This initiative could minimize additional water requirement significantly but it is difficult to make an assessment of the same at master plan level. As per IS 1172, out of a total per capita demand of 135-200 lpcd, a flushing water requirement of 45 lpcd may be taken for flushing requirements and the remaining quantity for other domestic purposes. However, other non-potable water uses may include gardening, washing etc. Recycled water has to be made available for non-domestic purposes and non-drinking purposes in the 251 villages where the new supply network is planned. Even after realising 865mld of treated recycled water and additional about 2000mld recycled water would be available, which can be utilised for revival of lakes and valley system. Using innovative systems like artificial aquifer recharge would help in improve the ground water levels.
Water Conservation: Over 50% of the population of the project population of 2031 has been assumed to be supplied potable water @135lpcd; however there is a strong potential for reducing this demand of 135lpcd through promoting awareness for water conservation, implementation of decentralised sewerage treatment plants for the local area, which can be utilised for gardening, horticulture purposes and other activities like car washing. This would lead to reduction in potable water demand to 120lpcd, which translate to saving of about 166MLD. Thereby bringing down the dependence on ground water below the present level.
Treating Recycled Water to Potable Level: The fact that Cauvery will not be adequate for city and relishing water from other sources is still to determined, it is proposed to recycle the sewage water with tertiary treatment technologies available in the market and supply to the city for all the purposes.
Evaluation of Proposals of Thyagaraja Committee: For long term purposes some of the major interventions proposed by the Thyagaraja Committee to explore new sources have to be considered by the state government on priority basis.
Rejuvenation of Lake and Valley System: The lake and valley system has been historically water supply source, however due to limited sewage network coverage; most of the lakes are filled with sewage. The improved coverage of sewage network is expected to improve the quality of water flowing into lakes. In addition to that recycled water shall be used to rejuvenate the lakes along with dredging of some of large lake to improve the holding capacities and aid ground water percolation. Adequate sewage network and infrastructure shall be developed to contain the sewage flow into lakes and streams.
Towards provision of land for water and sewage infrastructure, the Master Plan has incorporated the proposals provided by BWSSB for BBMP area and are appropriated depicted in proposed land use maps.
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