Water Management for Ahmedabad – Gandhinagar Urban

Agglomerate

Prakash R GupteSenior Hydrogeologist –(Sc-c)

CGWB, WCR, Ahmedabad

March, 2011

Location of Ahmedabad – Gandhinagar and its Urban Agglomerate

G ujarat

G andhinagar

G andh inagar C ity

Ahm edabad - Gandhinagar - Twin City with surrounding urban areas

Ahm edabad C ity

Ahmedabad is situated on both sides of river Sabarmati. It lies between 22°55' & 23°08' North latitude and 72°30' & 72°42' East longitudes where as new capital city, Gandhinagar is at 30 km north of Ahmedabad, on right bank of Sabarmati River, situated between 23°05' and 23°22' North latitude and 72°31' to 72°49' East longitude.

The areas around Ahmedabad and Gandhinagar city are rapidly developing and became one of the largest Urban Agglomerate known as “Greater Ahmedabad”, have total aggregate area of 4200 sq km

Ahmedabad Municipal Corporation (AMC) areas is 190.84 sq km,

Ahmedabad Urban Development Authority (AUDA) area is 1200 sq km,

Gandhinagar Notified Area (GNA) as Gandhinagar city area is 57 sq. km,

Bopal and 9 other Municipalities along with 150 semi urban / urban villages as Urban Agglomerates (UA) falls in Dascroi taluka and Gandhinagar taluka have area of 2752 sq. km.

Population Growth – Ahmedabad – Gandhinagar & AUDA Area

0.00

0.50

1.00

1.50

2.00

2.50

3.00

3.50

4.00

4.50

5.00

1981 1991 2011

Popu

latio

n in

Mill

ion

Population Growth

AMC Area AUDA Area Gandhinagar

The population in AMC area in 1981 was 21.5 Lakh which became 35.2 lakh in 2001

The population of AUDA area increased from 27.2 lakh in 1981 to 47.0 lakh in 2001.

The population of Gandhinagar city increased from 0.624 lakh in 1981 to 1.95 lakh in 2001.

The population within the AMC limits appears to approach a stabilization level – AMC area has very high density of 18,000 person / sq km.

The areas adjoining AMC, falling within AUDA limits have shown rapid growth. AUDA area has population density of 3,900 persons / sq.km

The area of Gandhinagar City also have very high growth rate and has population density of 3,400 persons / sq.km

Hydrometeorology – Ahmedabad – Gandhinagar Area

Ahmedabad – Gandhinagar area has a tropical monsoon climate, which is hot and dry, except in the rainy season.

Summer days are very hot with mean maximum temperature of 41.30C while, nights are pleasant with mean minimum temperature of 26.30C.

The mean maximum and minimum temperatures in winter are 30°C and 15.4°C respectively.

The average annual rainfall of the area is 782 mm, although there is a considerable variation from year to year. It occurs generally during the months of June to September.

The average relative humidity is 60% with a maximum of 80% to 90% during the rainy season.

0

10

20

30

40

50

60

70

80

90

0

50

100

150

200

250

300

350

Jan Mar May July Sep Nov

Rai

nfal

l (m

m)

Year

Rainfall (mm) Max temp °C Min temp °C

wind speed km/hr Relative Humidity (%)

Climatological Plot for Ahmedabad IMD Station

Physiography, Drainage & Soils – Ahmedabad – Gandhinagar Area

The area as a whole, in general monotonously flat except few mildly undulating topography owing to the presence of stabilized dunal land forms.

The elevation of land surface ranges from 40 to 60m AMSL with master slope towards south.

The average elevation of Ahmedabad city area is about 48m AMSL while Gandhinagar has 52 m AMSL. Isolated high grounds, with elevations more than 60m AMSL, are observed on both sides of river Sabarmati.

The most important surface water body in the Ahmedabad Gandhinagar area is the river Sabarmati. The Khari river runs almost parallel to the Sabarmati towards east, beyond the city limits.

One of the oldest irrigation schemes of Gujarat ‘Kharicut canal scheme’ passes through eastern part of Ahmedabad City, which also serve as ‘Strom Water Drainage’ during monsoon.

The Kankaria and the Chandola are two important ponds in the Ahmedabad city area. Under ambitious ‘National Lake Conservation Plan’, AMC and AUDA have taken up project to

interlink 45 surface bodies (ponds & lakes) and recharge it with storm water and surplus surface water of Narmada Canal.

The area is mostly underlain by blown sand and silt deposits of aeolian character, except localized pockets where it is fluvial.

The soils in the entire area are deep to very deep, with soil depths more than 100 cm. It is either coarse sandy or fine sandy loam, with less clay content and has good to excellent drainability.

Aquifer System – Ahmedabad – Gandhinagar Area

ISR OLD E ng

Centra l School M ES AP N arodaSabarm ati

R iver

0 m

-40

-80

-120

-160

-200

60

276

296

226214 219

Subsurface section between ISRO - N aroda

Scale

0 0.5 1 2 km Sand, gravel etc - AquiferC lay -silty c lay etc Aquitard

U nconfined Aquifer

Confined Aquife r

The subsurface aquifer disposition in Ahmedabad and Gandhinagar area, down to explored depth up to 300m, is very well established

Phreatic ( 30 to 60 m depth) as well as deep semi confined / confined aquifer system (60 to 200 m depth) are extensively developed

Deep boreholes have penetrated the

thick sequence of post-Miocene sediments down to 300 m depth and these sediments continue further below.

The aquifer system is regionally extensive and correlates with the aquifer system demarcated by CGWB in Central Gujarat plains (CGWB/UNDP-1978).

The Phreatic aquifer and first confined to semi confined aquifer can be correlated with the aquifer "A", which is phreatic at top and becomes semi-confined to confined at lower levels in the central Gujarat plains.

The second and third confined aquifers can be correlated with the aquifers "B" and "C" respectively

Geology & Stratigpahy - Ahmedabad – Gandhinagar Area

Age Lithology ThicknessQuaternary(Holocene – Pleistocene)

Alluvium Maximum 700 m ; 400 - 600 m around A`bad –G`Nagar

Tertiary(Miocene) Sandstone and Shale Maximum 900 m.

200-300 m near margin of the basin

- - - -- - - - - - - - - - - -- - -- - -Unconformity - - - - - - -- - -- - - - - - - - - - - -

(Oligocene) Sandstones, shale and limestone Maximum 160 m

(Eocene)Shale and siltstone with

sandstone and limestone intercalation

About 100 m thick in the centre and thinning towards east and west margin

Mesozoic(Cretaceous) Deccan Trap

-- - - - - - - - - - - -- - -- - -Unconformity - - - - - - -- - -- - - - - - - - - - - - Bagh Beds

Geologically, the Ahmedabad -Gandhinagar urban area forms a part of the Cambay Basin.

The thickness of multilayered Quaternary alluvium system in Ahmedabad – Gandhinagar urban area is around 300 to 600m, which is underlain by Tertiary sediments.

Geomorphologically they represent two types of landforms, i.e. fluvial and aeolian of Quaternary period.

The fluvial landforms consist terrace deposit, abandoned channels, cut-off meanders and swampy lands while aeolian landform consist dunes, inter dunes and sandy flats etc, of geological past in Quaternary period.

Depositional variations due to sea level changes, lateral shifting of river courses, soil formation and aeolian activities etc., were the active environmental agencies responsible for lateral and vertical variation of the lithological characters of Quaternary sediments.

The unconsolidated Quaternary formation consists mainly of alternate layers of sand, silt gravels and intermixed kankars etc

The sand horizons are prevalent at different depth levels and form aquifers. Spatial variation in groundwater quality and quantity may be attributed to intermixing / overlapping of various facies,

forming aquifer system in the area.

Depth to Water Level - Ahmedabad Gandhinagar Area

Water level increasing in depth from northwest to southeast direction.

In Gandhinagar city phreatic aquifer is almost dry and water level is hardly found between 35m and 40m bgl.

It is also observed that seasonal fluctuation of water table, between pre-post monsoon periods, ranges from -0.25 to 3.72m in phreatic aquifer.

In Ahmedabad Urban area depth to water level ranges between 7m and 40m bgl in phreatic aquifer.

Depth to Water Table - Ahmedabad Gandhinagar Area

Water table in user confined aquifer ranges from 20 m to 50 m bmsl in Ahmedabad Urban Area

In Gandhinagar area the water table is approximately 40m bmsl.

Ground Water flow direction is from South east to North west direction, towards deep aquifer zones of Cambay Basin

Water Supply By Sources – Ahmedabad & Gandhinagar Urban Area

0

500

1,000

> 1986 1986-2000 2000-2006 2006-2008

MLD

Water Supply by SourceAhmedabad Urban Area

Groundwater Surfacewater

In decades of 1970-80, water requirement of Ahmedabad urban area was totally met through series of deep tube wells spread in entire city areas. In decade of 1980-90 it was partially augmented through surface water resources.

Before 1986, out of total 400 mld water supplied, contribution from groundwater resources was 350 mld (88 %).

With implementation of various surface water sources projects dependency on groundwater decreased drastically

In year 2006-2008,, out of total 760 mld water supply, only 30 mld (4 %) is from ground water resources (AUDA 2008).

Water requirement of Gandhinagar Urban area is mostly relied on surface water resources

At present, in Ahmedabad & Gandhinagar area Surface Water Resource is main source for water supply Over the years, Groundwater levels are rapidly declining and deep ground water has high TDS, making it unsuitable for drinking uses.

Water Supply – Present Status & Projection for future

Year 1991 2001 Projection2011 2021 2031

Population in lakh

33.00 44.27 53.99 79.58 101.44

Water Requirements

in mld528 706 863 1273 1623

Year 1999 2001 Projection2025

Population in lakh 1.90 2.00 4.25

Water Requirements

in mld45 50 120

@ 160 LPCD

@ 250 LPCD in 1999 & @ 270 in 2001 & 2025

Ahmedabad Urban Area

Gandhinagar Area

With increasing population, Large Gap in Ground Water Supply & Total Requirement

Additional demands are meet through Surface Water Resource

Ahmedabad & Gandhinagar Urban Area are exceedingly

relying on Surface Water Supply

Water Level Decline trend of Ahmedabad Urban Area

1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

0.00

20.00

40.00

60.00

80.00

100.00

120.00

Water Level Decline - AMC Area TW

Central Zone Eastern Zone Western ZoneWat

er Le

vel i

n m

bgl

YearWater level in Tube Wells(m bgl)

Central Zone

Eastern Zone

Western Zone

1960 24.38 17.06 23.161965 41.45 31.69 40.231970 54.86 45.11 53.641975 67.05 54.86 64.611980 78.03 65.83 73.761985 86.56 75.59 83.511990 93.87 82.90 91.441995 99.97 90.22 96.31

The aquifer system occurring at depth zones 45 & 90m; 100 & 170m; 180 - 250+m are developed through tube wells in Ahmedabad Urban area

Tube wells however screen all these aquifers and thus providing effective interconnection and therefore the information is cumulative of different aquifers tapped.

Consistent decline in groundwater level at rate of 2 to 4 m per year from 1960 to 1995 is recorded in AMC tube wells

Hydrograph - Ahmedabad – Gandhinagar Area

y = 2.3961x - 4692.70

20

40

60

80

100

1201984 1986 1988 1990 1992 1994 1996 1998 2000

Dep

th to

Wat

er L

evel

(m)

Years

Well Hydrograph

46A4C05 Ahmedabad Cant Pz I I Ahmedabad District [Zones: 125-192 m bgl]

y = 0.3989x - 769.770

5

10

15

20

25

30

35

401986 1988 1990 1992 1994 1996 1998 2000

Dep

th to

Wat

er L

evel

(m)

Years

Well Hydrograph

46A4C07 Gandhinagar Pz III [Zones: 40-60 m bgl] Gandhinagar District

Consistent decline in phreatic and deep water level observed in Ahmedabad – Gandhinagar Area during 1986 to 2000

Effect of recharge / water conservation observed in phreatic aquifer at places – (Bopal Pz III Above)

Bopal Pz III – Zone 10 to 40 m depth

Rise O.53 m / year

Ahmedabad Cantonment Pz –I Zone 126 to 192 m bgl

Gandhinagar Pz – III Zone 40 to 60 m bgl

Decline O2.3 m / year

Decline O.4 m / year

Groundwater Resources – Ahmedabad – Gandhinagar Area ( Year 2004 )

S. No. Groundwater Resource ComponentAhmedabad

City and Daskroi Taluka

Gandhinagar Taluka

1. Gross Groundwater Recharge (MCM/yr.) 150.06 121.042. Allocation for Natural Discharge (MCM / year) 7.50 6.05

3. Utilisable Groundwater Recharge (MCM/yr.) [80% of “1”] 142.56 114.99

4. Total Groundwater Draft (MCM/yr.) 215.06 160.985. Groundwater Balance (MCM/yr.) -95.75 -49.79

6 Allocation for domestic & industrial used for next 25 years (MCM/yr.) 70.91 10.15

7. Level of Groundwater Development (%) 150.86 139.998. Category Over Exploited Over Exploited

Groundwater formed a dependable, most important source of water in Ahmedabad –Gandhinagar area till year 1980

With overall development of groundwater resources in all over the State, mainly in Central Mainland Gujarat, groundwater draft has outpaced natural recharge component in Ahmedabad and Gandhinagar area.

Both, Ahmedabad City –Dascrori Taluka & Gandhinagar Taluka area are in ‘Over Exploited’ category since 1997

Hydrochemistry – Ahmedabad – Gandhinagar Urban Area

In parts of Ahmedabad urban area, Groundwater at shallow depths shows wide variation in the chemical quality. In general, groundwater is brackish with EC >3000 µS/cm

(at 25°C), in most of the South and southwest part High nitrate concentration (more than 100 ppm) has been

observed at a number of sampling points. High fluoride concentration (more than 1.5 ppm) has also

been observed in localized areas. The quality of the groundwater in the deeper aquifers is

generally fresh up to 250 m depth for which data is available.

However, at places the brackish groundwater is also observed within this depth.

In Gandhinagar Urban Area groundwater quality in major part of the area is fresh

The Electrical Conductivity (EC) of groundwater varies between 250 to 1000 µS/cm (at 25°C) in phreatic aquifer.

The chloride value in groundwater ranges from 65 ppm to 250 ppm.

Deep ground water is also good except a small area in the south-western part of the area, around Sertha, have brackish to saline groundwater at depth

Major Groundwater Related Problem – Ahmedabad – Gandhinagar Area

Groundwater resources are depleting at alarming rate in major part of Ahmedabad – Gandhinagar urban areas, although most of the domestic and industrial requirement is meeting through Narmada based surface water resources.

The AMC operates about 300 deep tube wells to augment city water supply. Abstraction from river bed aquifer by radial wells other 2000 no of private bore wells / tube wells owned by private housing societies, business houses, industries, cantonment area etc., create huge stress on already exploited deep aquifer system.

Over the years, consistent fall in water levels (piezometric surface) and has affected the well yields and pumping costs.

Lowering of aquifer potential heads seems to have created a regional groundwater trough in the central part

Depleting Ground Water Resources

Pollution of Ground Water

One third of the sewage of the city is partially treated and remaining two thirds of untreated sewage is directly discharged in the Sabarmati which make downstream most vulnerable to groundwater pollution.

Industrial effluent of eastern part of Ahmedabad urban area are either discharged in to the Kharicut canal, small nallas or spread over the topographic depressions. This has caused degradation of land in these areas and probably also effected the shallow groundwater.

Improper construction of wells particularly in private sector, lack of aquifer protection by cement seals and grouts and old abandoned wells can serve as conduits for direct vertical connection and make deep aquifer vulnerable to pollution.

Feasibility of RWH & AR in Ahmedabad Gandhinagar Area

Large scale exploitation of groundwater resources during last two decades has created major portion of unconfined aquifer system dry, which has good scope to get recharge through suitable structures and sources.

Groundwater recharge experiment by injection under pressure (80 to 100 psi ) in 1974 by State Govt in a deep tube well, established feasibility of injecting water @ 3888 m3/day.

Another study of State Government with PRL, in 1977 near Hansol involving shallow dug well as source well and deep tube well of tapping aquifer below 75 m (tapping 80 m of granular zones) as target zones, it was observed that no clogging in injection well after 220 hrs of recharge. the efficiency of injection well could be improved and the frictional losses minimised using PVC

pipes for siphon, better recharge rates of up to 980 lpm could be achieved. This method was found more economical , costing @ 45 paisa per 1000 litres

Similarly the technical feasibility and economic viability of artificial recharge of groundwater, in North Gujarat alluvial plains, having similar hydrogeological condition like Ahmedabad –Gandhinagar area, has already been established by CGWB on the basis of pilot studies carried out under UNDP –CGWB project in 1986.

A pilot project for waste water renovation for unrestricted irrigation and groundwater recharge using Soil-Aquifer Treatment System (SAT) Technique in the Sabarmati bed at Ahmedabad was conducted jointly by NEERI, PRL and AMC(1997) and found that the SAT renovated effluent conformed to the WHO bacteriological guidelines for unrestricted irrigation.

Recently, under ‘National Lake Conservation Plan’ few lakes in AUDA and AMC area have been renovated and connected through storm water drainage have shown rise in phreatic aquifer water level in many parts of the Ahmedabad City

Groundwater Development Strategy – Ahmedabad Gandhinagar Area

GW Monitoring & Regulatory Measures

Real time water level monitoring and management systems can be worked out in stressed areas. Through suitable regulatory measures, enforcement of directives to uses ground water resources

for specific purpose can be worked out

GW Conservation & Artificial Recharge

Review existing directive to construct roof top rainwater harvesting structures in new building for efficient implementation

The surface run off water from roof top of buildings, road surfaces, parks, schools, stadiums, etc., can be diverted to shallow recharge pits, shallow bores, abandoned dried dug wells, etc.

The areas where excess rain water accumulates, like the village ponds/talavs and other natural depressions, should be utilized for water conservation purposes.

Similarly, for Gandhinagar area, aquifers below 200m depth are notified by CGWA during year 2000, as protected aquifer for drinking water use only. Improving enforcement of this directive and efficient monitoring can help conservation of deep aquifer resources.

All surface body – existing ponds and lakes in urban area can be rejuvenated and improved for artificial recharge of surplus storm water & Narmada Canal Water in line of ‘National Lake Conservation Plan’ for ground water recharge.

Thanks