Analysts examine Bengaluru’s water security indices and data challenges

Water usage in the city, per ward, has been determined by examining the groundwater index, land use index, and governance index.

(In Part 1, data analysts explained how they arrived at a definition of water security. In Part 2, the analysts explained the methodology used in estimating the Cauvery index and the results have been obtained. In continuation, part 3 will explain the methodology used in estimating the remaining indices and its results)

Groundwater index

Borewell count: The OpenCity borewell dataset was used to map borewells into Bruhat Bengaluru Mahanagara Palike (BBMP) wards and compute the number of borewells per ward. Assuming an average yield of 5,000 litres/day, water supply from borewells was normalised with ward population and the wards were ranked by this normalised supply.

Groundwater extraction: Data from the Dynamic Groundwater Resources of Karnataka as of March 2022 was used to assess the groundwater extraction. The relevant table for Bengaluru (Annexure -VB [Page 114]) is reproduced below:

DistrictTaluk% over extractionCategorisation
Bengaluru RuralDevanahalli152Over Exploited
Bengaluru RuralDoddaballapur157Over Exploited
Bengaluru RuralHosakote167Over Exploited
Bengaluru RuralNelamangala105Over Exploited
Bengaluru UrbanAnekal129Over Exploited
Bengaluru UrbanBengaluru North170Over Exploited
Bengaluru UrbanBengaluru South108Over Exploited
Bengaluru UrbanBengaluru East239Over Exploited
Bengaluru UrbanYelahanka157Over Exploited

The wards were then mapped to the respective taluks. Lower groundwater extraction is desirable and hence wards with lower over extraction percentage were assigned a higher rank.

Groundwater quality: Data from the Karnataka State Groundwater Quality Evaluation Report -2018 was used. Table -12 water quality Data of Bengaluru Urban DIstrict 2018-2019 from the report has been reproduced below:

DistrictTaluk# of monitoring stationsStations with non -potable water
Bengaluru RuralDevanahalli617%
Bengaluru RuralDoddaballapur930%
Bengaluru RuralHosakote520%
Bengaluru RuralNelamangala617%
Bengaluru UrbanAnekal770%
Bengaluru UrbanBengaluru North1457%
Bengaluru UrbanBengaluru South767%
Bengaluru UrbanBengaluru East650%
Bengaluru UrbanYelahanka                          NA57%

The wards were then mapped to the respective taluks. As with the groundwater extraction, wards with a lower non-potable probability were assigned a higher rank.

Lake/tank area coverage: We analysed the BBMP wards dataset with QGIS to determine the percentage of area covered by lakes and ponds in each ward, using the Lakes and Ponds data from Open City.

Results

The ranks at the variable level were then added up and the wards were ranked again to arrive at the groundwater index. The results are plotted in the heatmap below:

A higher area covered by lakes and tanks is good in terms of groundwater rechargeability. Hence, wards with a higher area covered by lakes and tanks were assigned a higher rank.

Ward #Ward NameBorewell Water supply (l/p/d)Lakes/tanks %Groundwater extractionGW QualityRank
ValueRankValueRankValueRankNon-potable probabilityRank
106Marathahalli9.32325%3239%550%11
9Hebbal Kempapura8.92813%7170%457%22
101Dodda Nekkundi9.2269%10239%550%13
1Kempegowda Ward8.43210%8157%357%24
45Rajarajeshwari Nagar12.343%39108%167%35
4Yelahanka Satellite Town11.393%35157%357%27
10Byatarayanapura10.3164%28157%357%27
14Kuvempu Nagar14.432%44157%357%28
213Jaraganahalli7.44418%6108%167%39
22Peenya Industrial Area8.7306%20170%457%210
58Kadu Malleshwar Ward0.32010%95170%457%2216
82Banaswadi0.32020%95239%550%1217
124Subhash Nagar0.32030%95170%457%2218
57Rajmahal Guttahalli0.32040%95170%457%2219
76Hennur0.32050%95170%457%2220
117Vasanthnagar0.12110%95170%457%2221
120Bharathi Nagar0.02160%95170%457%2225
125Okalipuram0.02160%95170%457%2225
150Attiguppe0.02160%95170%457%2225
119Shivaji Nagar0.02160%95170%457%2225

The results are displayed in the heatmap below:

  • The blue end of the spectrum represents the best-performing wards
  • The white end represents the worst-performing wards
groundwater index map
Bengaluru groundwater extraction and quality heat map. Graphic: Team “Vrishabhavathi”
  • Wards which have been historically serviced by Cauvery water and hence less dependent on borewell supply appear to be ranked quite low in this index
  • Some wards in the eastern and the south western areas rank very low, this is likely due to inadequate data on the actual number of borewells present

Land use index

Built up area: We used the land use maps – built-up vs unbuilt to arrive at the unbuilt area in each ward. Wards were ranked in ascending order of unbuilt area percentage – the more unbuilt area in a ward, the higher the ranking.

Results

The ranks for each variable (built-up area and commercial area) were then summed up individually. These totals were ranked again to determine the land use index/rank. The ward with the best performance in terms of the identified variables is ranked 1, while the ward with the worst performance is ranked 225. The table below provides the variable values and ranks for the top 10 and bottom 10 wards.

Ward #Ward NameUnbuilt area % (lakes excluded)Commercial land area %Net Rank
ValueRankValueRank
33Hemmigepura87%10%11
104Varthur80%20%12
208Anjanapura78%40%13
36Jalahalli78%50%14
172Agaram77%60%15
97Kadugodi73%90%16
210Kalena Agrahara72%110%17
31Bande Mutt71%120%18
203Subramanyapura71%130%19
44Jnana Bharathi ward70%140%110
189Ganesh Mandir ward18%15670%208216
197Srinagar7%20729%158217
154Rayapuram4%21333%163218
52Shakthi Ganapathi Nagar9%19642%183219
148New Guddadahalli12%18167%199220
55Malleswaram13%17688%215221
50Nalvadi Krishna Raja Wadiyar4%21840%178222
179Madivala4%21650%187223
79Kadugondanahalli6%20960%198224
153Padarayanapura1%22546%185225

The values plotted on to a heatmap is presented below:

  • The blue end of the spectrum represents the best performing wards
  • The white end represents wards which perform the worst
Land use index heat map with built-up area and commercial area
Bengaluru ward level land Use index heat map. Graphic: Team “Vrishabhavathi”

The peripheral areas particularly on the southern and eastern edges perform better on this index owing to less built-up and commercial area.

Governance index

The Bangalore Water Supply and Sewerage Board (BWSSB) contacts were obtained from their website and their office location details were geocoded. We then assigned these locations to their respective wards. We located the following wards where a BWSSB liaison officer was available.

Ward NumberWard Name
100Garudachar Palya
101Dodda Nekkundi
102AECS Layout
104Varthur
107Bellanduru
15Kammagondanahalli
17Chikkasandra
19T Dasarahalli
203Subramanyapura
206Konanakunte
208Anjanapura
209Gottigere
212Naganathapura
224Hosa Road
225Kudlu
26Dodda Bidarakallu
27Lingadheeranahalli
29Ullalu
3Atturu
33Hemmigepura
5Kogilu
7Thanisandra
8Amrutahalli
86Challakere
87Horamavu
97Kadugodi

Having access to a BWSSB liaison officer is desirable. Therefore, the wards mentioned in the table above were assigned a rank of 1, while the rest of the wards ranked at 2.

(Part 4 of the series will highlight how to address the gaps in data to enhance Bengaluru’s water security)

(The other team members who contributed their insights for this article are: Swati Ganeshan, VishnuPriya Viswanathan, Ritika Gupta, Aniket Sawant, and Chandanapriya Dhanraj)

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