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M. S. Mohan Kumar Department of Civil Engineering Indian Institute of Science Bangalore Urban Groundwater Scenario

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Page 1: Urban Groundwater Scenario - KSWNkswn.in/images/Mohan_Kumar.pdf · Urban Groundwater Scenario. Increased global ... •Overexploitation and poor management have contributed to

M. S. Mohan Kumar

Department of Civil Engineering

Indian Institute of Science

Bangalore

Urban Groundwater Scenario

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Increased global water stress

Global Water Scarcity

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Groundwater• Groundwater is the largest accessible and often still untapped freshwater

reservoir on earth.

• Global groundwater resources are assessed to be around 10.5 million km³. (Source: BGR & UNESCO)

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Groundwater

Groundwater depletion remapped in three-dimensional topography to show 'mountains of groundwater depletion' especially in the United States, Mexico, Saudi Arabia, Pakistan, India and China.

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1951 5177

1991 2209

2001 1820

2025 1341

2050 1140

Present Demand 813

Total Anticipated

Demand

In 2025 1093

In 2050 1447

Water Demand

(Billion Cubic Metre)

Per Capita Water Availability

(Cubic Meter Per Year)

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Demand and Supply Gap

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Demands of various Sectors

(In percentage)

Sector 2010 2025 2050

Irrigation 78 72 68

Domestic 6 7 9

Industries 5 8 7

Power 3 4 6

others 2 2 3

Evaporation

losses

6 6 7

Major portion from

Groundwater

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Groundwater• Groundwater is the major source of drinking water in both

urban and rural India.

• Besides, it is an important source of water for the agricultural and the industrial sector.

• 85% of rural population obtain water mainly from wells where the source is shallow or deep aquifers (groundwater).

• The total annual replenishable ground water resource in India is about 433 BCM.

• 16 percent of total potential used for drinking, industrial and other purposes, the remaining available for irrigation.

• Its availability depends on the rainfall and recharge conditions.

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• Total Annual Ground Water Recharge: 433 BCM

• Balanced Dynamic Ground Water: 168 BCM

• Annual ground Water Draft: 231 BCM

• Major source of ground water recharge: Rainfall (67%)

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Withdrawals of Surface and Groundwater

• Exploitation of ground water has reached such a state that natural recharge is not sufficient.

• Pollution of groundwater resources has become a major problem today.

• The pollution of air, water, and land has an effect on the pollution and contamination of groundwater.

A major portion of ground Water in India is used for irrigation.

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Groundwater Status – Global and Indian ContextGlobal trends in groundwater irrigation

Top 20 groundwater irrigating countries

Source IWMI

India: around 27Mha

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• Urban Groundwater

– Generally used for domestic and industrial use.

– Natural groundwater recharge is less due to impermeable surfaces.

– Groundwater pollution is high compared to rural groundwater

• Rural Groundwater

– Generally used for agricultural uses.

– Natural recharge is more compared to urban areas.

– Pollution is less due to lack of industries polluting surface water etc.

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Urban Groundwater

•Uses: ResidentialCommercialIndustrial

•Recharge:Rainfall rechargeLeakages from drinking water pipelinesLeaking sewersSurface water (contaminated)

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Urban Groundwater Issues

Water Quantity Issues:

Reduction in water level

Inadequate recharge

Climate change and Urbanization

Water table rise will cause water logging in low-lying areas.

Water Quality Issues

Recharge from sewers

Natural contaminants like arsenic, fluoride, iron etc.

Agricultural pollution

Industrial pollution

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Groundwater Quantity Issues

CATEGORISATION OF BLOCKS/MANDALS/TALUKASAs on March 2004 (CGWB)

Water level FluctuationJanuary 2007 vs Decadal Mean (1997-2006)

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Groundwater Quality Issues

• Most of the contaminants are due to anthropogenic activities, while a few are due to natural geologic deposits of salts

• 14 states in India have fluoride levels above 1.5 ppm

• High levels of arsenic (above 50 ppb) found in 6 districts in West Bengal

• Excessive withdrawal of water from coastal aquifers especially in Kutch & Saurashtra in Gujarat, Chennai in Tamil Nadu and Calicut in Kerala has led to saltwater intrusion

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Fluoride affected areas in IndiaArsenic affected areas in West Bengal

Groundwater Quality Issues

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Groundwater Scenario in Bangalore

• Groundwater plays an important role in the total water

supply of the city. 40% of the population of Bangalore isdependent on groundwater.

• Number of borewells in the city is ranging from 200,000 to400,000.

• Overexploitation and poor management have contributed togroundwater depletion and quality problems.

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Piped and Groundwater Supply: Bangalore

Zone Surface Water (MLD) Groundwater (MLD)

Central 67.10 38.91

North 210.46 87.08

West 184.89 149.45

East 169.19 50.46

South 133.106 176.00

South East 104.79 67.80

Total 869.54 569.70

•BWSSB Zonewise Piped Water Supply and Groundwater Consumption

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Ground Water Scenario in Bangalore

Source: CGWB, 2011

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Well Density= Number/Km2

House Borewell

Public Borewell

Groundwater Pumping

Total Pumping =

4.26 MLD/Km2

Groundwater pumping

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Population Density :

9206 – 70408 Persons/Km2

BWSSB Water Supply :

1.08 – 5.29 MLD/Km2

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Bangalore: GW Pumping and Recharge

• Annual Rainfall in Bangalore: 900mm; of which 10% is recharge(0.07 km3/yr)

• Piped water supply to Bangalore is about: 910 MLD out ofwhich 45% is UFW. And of this UFW, 50% recharges the groundwater (0.07 km3/yr)

• Wastewater: Considering 50% of wastewater recharges theground water, (0.07 km3/yr) total ground water recharge is0.21 km3/yr.

• Groundwater - Assuming 50% of the borewells are dry, and theremaining borewells yielding about 1.5lit/sec, with a pumpingof 2 hours duration per day, groundwater pumping is 0.59km3/yr.

Pumping=2.8 times Recharge

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Ground Water Scenario in Bangalore: Water Quality

Source: CGWB, 2011

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Status of groundwater quality in Bangalore: Conducted by the Department of Mines and Geology, Government of Karnataka

• The study collected 918 samples from 735 locations across an area of 400 square kilometers of the city .– In 370 locations (50.34%), the groundwater was found

not suitable for domestic purposes as per the ISO 10500:1991 standard.

– 278 samples showed higher than permissible nitrate contamination, as high as 747 mg/L (permissible limit of 50 mg/L).

– Bacteriological contamination was tested separately at 100 locations that were deemed high-risk, and contamination was found in 74 of the 100 samples.

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Groundwater in Coastal towns

• Over exploitation of coastal aquifers results in environmental impacts including seawater intrusion and land subsidence.

• Rivers are the major contributors of pollution of the coast and coastal aquifers.

• A case study of Warakaliaquifer in Kerala (Thiruvananthapuram) showed high amounts of salts and fluoride.

A rise in sea-level will affect ground-water flow in coastal aquifers

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• To develop a sustainable water management plan towards the future

needs of Mulbagal Town, Kolar district, Karnataka.

• To efficiently manage the groundwater resources.

• To achieve these groundwater studies have been taken up, which envisage

to assess the behavior of the groundwater system through monitoring of

groundwater levels & its use.

• Models are being developed that would be used as diagnostic tools for

current and future assessments.

• Emphasis is also on development of generic models applicable for

“urban groundwater management goals” with the optimal data

collection.

• Population- 80000, Borewells-105, Water supply – 4 MLD

Mulbagal experience: Groundwater based water supply

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System Details

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1. The Mulbagal town (~ 6 Km2) is in the Kolar district of

Karnataka and is on the highway between Bangalore and

Chennai.The population of the town is ~80,000. The demand

for water is 4.0 mld.

2. The current water supply is ~3.0 mld. The water needs are

mainly met from groundwater sources. Municipality has (75%)

wells, which are pumped. In addition there are private wells

(25%) as well.

3. The municipality has a total of 105 bore wells. There are Five

pumping stations, which are located outside the town and each

station has a cluster of bore wells that are pumped to distribute

water to the town. A total of 51 bore wells (~50%) are there in

these five pumping stations.

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Investigations

1. During July 2008-August 2009, monthly groundwater table

mapping and its dynamics during the monsoon & non-monsoon

season have been obtained through extensive monitoring. This

was performed by a novel approach in which the existing wells

are used as observation wells. Since there is no observation well

network of any government agency in the town, the first step was

to create a data base specific to the scale of the town.

2. The data base of monitoring comprises of: Municipal wells = 98;

Private wells = 37; Agricultural wells = 137.

3. The yields of wells (~ 140 wells) are obtained by extensive data

collection. The yields vary from 1 L/s to 3 L/s (average ~ 2 L/s

with a cov of 60%).

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1. A simple methodology is developed that uses groundwater level

fluctuations during monsoon and non-monosoon in various

zones with different controls to estimate (i) rainfall recharge,

(ii) recharge from indirect sources, (iii) subsurface drainage.

2. The recharge amount estimated in the town is much higher than

outside town region due to the other sources of recharge. The

relatively lower quality of water in the town indicates the

impacts of other indirect recharge sources.

3. The recharge in the town occurs both from direct rainfall

recharge as well as indirect sources of leakages.

Groundwater Studies

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1. At present there is no operating approach for assessing the

groundwater balance components at the scale of a town or city.

This needs to be jump started since several towns depend for a

large fraction on groundwater.

2. Such a practice would lead to sustainable development in the

future considering the large investments (to the tune of few

crores towards bore wells drilling, pumping machinery and

ancillary systems) made by municipalities and private users.

3. The studies being performed at Mulbagal town would bring out

(a) how to protect the catchment areas of pumping zones and

their sustainability, and (b) how to efficiently manage the

groundwater within the town combining it with water and

waste water treatment options.

Policy Issues

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Mulbagal town limits & setting

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GW Monitoring Network with Wards

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Way Forward: Ground Water Management

• Demarcation and assessment of artesian aquifers• Mapping of flood plain aquifers• Mapping of important aquifer system• Management of coastal aquifer• Conjunctive use of surface and ground water in

irrigation• Remote sensing studies for ground water studies• Water balance studies at city scale for groundwater

usage. • Ground water resource assessment in:

– Over-exploited area,– Naturally contaminated area– Water scarce areas

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National Project on Aquifer Management (NAQUIM)

• The importance of groundwater for national development has deemed it necessary to be more specific; more general “groundwater management” has become “aquifer management” to answer the specific queries on availability and sustainability.

• CGWB has taken up National Project on Aquifer Management in XII & XIII Plan period to formulate sustainable aquifer management plan.

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National Project on Aquifer Management (NAQUIM): Flow chart

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Ground Water Regime Monitoring

• Total number of 15653 ground water monitoring wells are located all over the country.

• Ground water samples are collected from these observation wells once a year during the month of April/ May to obtain background information of ground water quality changes on regional scale.

• This data is used for assessment of ground water resources and changes in the ground water regime.

• Karnataka : 1507 monitoring wells.

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Ground Water Resources Assessment

• Ground Water Resources of the country have been assessed and being updated periodically by CGWB. There are two types of resources viz:– Annually Rechargeable Dynamic Ground Water

Resource: This resource is computed jointly by CGWB and State Ground Water Departments

– Static Ground Water Resource: This occurs below the dynamic resource and it has been evaluated on the basis of explorartory drilling. Till now the static resource has been assessed to the depth of 450m in soft rock and 100m in hard rock

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Artificial Recharge of Ground Water• A demonstrative scheme on “Rain Water Harvesting and

Artificial Recharge to Ground Water” has been taken up at following areas:

– Lingala, Pulivendula Vemula and Vemalli blocks in Kadapadistrict, Andhra Pradesh

– Gangavalli block in Salem district, Tamil Nadu– Mallur Block in Kolar district, Karnataka– Bel watershed, Amla & Multai Blocks in Betul District, Madhya

Pradesh.– Upper reaches of Choti kali Sindh river in parts of Sonkatch &

Bagli blocks in Dewas district, Madhya Pradesh.

• Combination of Percolation Tanks, Watershed Structures,Recharge wells, Roof Top Rain Water Harvesting are adopted for artificial recharge of ground water.

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Acknowledgements

• Anjana G R

• Usha Manohar

• Sheetal Kumar K R

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Thank you…..