Rainwater Harvesting in India:Rainwater Harvesting in India:Rainwater Harvesting in India:Rainwater Harvesting in India:Some Critical Issues for Basin Planning and Some Critical Issues for Basin Planning and Some Critical Issues for Basin Planning and Some Critical Issues for Basin Planning and

ResearchResearchResearchResearch

M. Dinesh KumarM. Dinesh KumarExecutive Director

Institute for Resource Analysis and PolicyHyderabad

Email: dinesh@irapindia.orgBrainstorming session on Farm Ponds

CRIDA, Hyderabad21-22 April, 2009

Plan of Presentation

� Introduction to the basic premise

� Supply side issues in RWH

� Demand side Issues

� Economic issues� Economic issues

� Issues relating to improving basin water economy

� Major findings

� Ways to make RWH more effective

� Conclusions

Water Harvesting and Groundwater Recharge in India

� Objectives� Improve runoff collection and

storage efficiency� Equitable distribution of water� Resource management

� Underlying value

� Local water self sufficiency; � Local water self sufficiency; demands are small

� Assumption

� More structures mean more benefit

� Structures are cost-effective

� Planning & action are community based & decentralized

Supply-Demand Issues in Rainwater Harvesting

� Low rainfall in water scarce areas

� Variability in rainfall is high in water scarce regions

� Fewer rainy days in semi arid and arid, water scarce areas

� Evaporation rates are high in water scarce regions

� Large part of India has hard rock geology

Supply-demand issues in rainwater harvesting

� High inter-annual variability in runoff

� Poor infiltration capacities of soils in

hard rock areashard rock areas

� High water demand in water scarce areas

� Demand far irrigation exceeds the locally harvestable renewable resources

Economic Issues in Water Harvesting

� Very High Cost of Production of Water

� The gross returns range from Rs. 1.9/m3 to Rs. 17/m3 (based on data from 450 farmers in 9 agro climatic sub-regions) 9 agro climatic sub-regions)

� Scale considerations are important in economic evaluation of small WHS

� Trade off between economics and hydrological benefits

Issues related to improving basin water economy

� Demands higher in lower plains of river basins; supply potential is high in upper basin areas

� Economic value of water is high in scarce � Economic value of water is high in scarce areas

� Lack of integrated approach to planning

� Groundwater contributing to surface flows in hilly areas

Issues related to improving basin water economy

� Poor storage in hard rock aquifers

� Many basins are physically water-scarce

� Downstream Impacts in closed basins

� Many basins in water-scarce regions are “closed”

� Downstream negative impacts in Ghelo river basin, Saurashtra

� Lack of water use planning for the harvested water

Findings

� Limited potential of RWH in water-scarce areas

� low mean annual rainfalls, high inter-annual variability, high PET & E

� Inefficient recharging in hard rocks

� Many water-scarce regions have water demands, far exceed the supplies

� Unit cost of water harvesting is prohibitively high for many known techniques

� Scale considerations can further reduce the economic prospects of water harvesting

Findings

� Lower catchments of basins are more naturally water-scarce

� Economic value of water is high in water-scarce areas scarce areas

� Maximizing hydrological benefits reduces cost effectiveness

� U/S diversions reduce prospects of D/S areas in closed basins of water-scarce areas

How to make water harvesting more effective?

� Understand catchment hydrology better

� Use of hydrological simulation models for un-gauged basins

� Use of remote sensing and GIS to generate geo-morphological data for simulation modelsmorphological data for simulation models

� Analyze cost implications of harvesting/recharge for different physical environments and with different systems

� Focus on green water, harvested in RWHS

� Collection efficiency

� Use efficiency

How to make water harvesting more effective? Cont…

� Study basin water accounts and water balance

� How much water is used up as beneficial ET, non-beneficial Evaporation

� How much surplus flows available for harnessing� How much surplus flows available for harnessing

� Improve wet water-saving in water harvesting structures and large water resource systems

� Develop proper water use plans for WHS as well

Conclusions

� Water harvesting/watershed programmes to be supported by proper understanding of basin water accounts and balance

� Further, indulging in large-scale water harvesting projects calls for a careful harvesting projects calls for a careful consideration of costs and benefits with due consideration to hydrological regimes, and cost of different techniques.

� Developing proper water use planning before harvesting initiatives is important Developing proper water use planning before harvesting initiatives is important

Average Mean Annual RainfallAverage Mean Annual Rainfall

Coefficient of variation in rainfall

Mean Annual Rainy Days

Infiltration Rate in Sandy Loam and Silty clay

Soil at the bottom of dug well

1500

2000

2500

Infi

ltrat

ion

Rat

e (m

m/h

r) f

or s

andy

60.00

70.00

80.00

90.00

Infi

ltrat

ion

Rat

e (m

m/h

r) f

or s

ilty

Sandy Loam Sandy Loam

0

500

1000

1500

1 3 5 8 12 20 30 50 80 120

Time (Minutes)

Infi

ltrat

ion

Rat

e (m

m/h

r) f

or s

andy

lo

am

0.00

10.00

20.00

30.00

40.00

50.00

60.00

Infi

ltrat

ion

Rat

e (m

m/h

r) f

or s

ilty

clay

Sandy Loam Sandy Loam

Silty Clay

Average Annual Potential EvaporationAverage Annual Potential Evaporation

Aquifer System in India

Runoff Variability Higher than Rainfall Variability

Probability of Occurrence of Rainfall and Runoff in Banas

basin

400000

500000

600000

Estim

ated Runoff

(cubic m

etre)

1500.00

2000.00

Rainfall (m

m)

Estimated runoff

Rainfall

0

100000

200000

300000

400000

1.2

8.3

15.5

22.6

29.8

36.9

44.0

51.2

58.3

65.5

72.6

79.8

86.9

94.0

Percentage probability

Estim

ated Runoff

(cubic m

etre)

0.00

500.00

1000.00

1500.00

Rainfall (m

m)

Upstream Vs Downstream Water Upstream Vs Downstream Water Demands in AgricultureDemands in Agriculture

Figure 7: Ustream Vs Dowmstream Water Demands in 6 Basins

1.5

2

2.5

3

3.5

/R

0.3

0.4

0.5

Per Capita

Net Sown Area

(ha)

0

0.5

1

1.5

Sabarmati Indus Narmada Cauvery Krishna Mahanadi

ET 0/R

0

0.1

0.2

Per Capita

Net Sown Area

(ha)

ET0/R (UCD) ET0/R (LCD)

Per Capita Net Sown Area (UCD) Per Capita Net Sown Area (LCD)

Water has Higher economic value in scarce areas

11.007

14.85215

20

Econom

ic v

alu

e (Rs)

11.007

0

5

10

Eastern UP Western Punjab

Econom

ic v

alu

e (Rs)

Sr. No

Type of Recharge Structure

(Life in years)

Expected Active Life of the System

Estimated Recharge Benefit(TCM)

Capital Cost of the

Structure (in Lac Rs.)

Cost of the

Structure per m3 of water

(Rs/m3)

Annualized Cost*(Rs/m3)

Estimated Unit Cost of Artificial Recharge Structures Builtunder Pilot Scheme of CGWB

1 Percolation Tank

10 2.0-225.0 1.55-71.00

20.0-193.0

2.00-19.30

2 Check Dam 5 1.0-2100.0

1.50-1050.0

73.0-290.0

14.60-58.0

3 Recharge Trench/Shaft/

3 1.0-1550.0

1.00-15.00

2.50-80.0 0.83-26.33

4 Sub-surface Dyke

5 2.0-11.5 7.30-17.70

158-455.0

31.60-91.00

GOI, 2007

Water harvesting interventions to replace a SSP (9 MAF of water)

would cost us somewhere near two times the rough cost of NRLP

Wells are overflowing!

Figure X: Water Level Fluctuation in Wells in Fulzar, Ghelo River

Basin

0

15-0

622

-06

29-0

66-

0713

-07

20-0

727

-07

3-0810

-08

17-0

824

-08

31-0

87-

0914

-09

21-0

928

-09

5-1012

-10

19-1

026

-10

2-119-

1116

-11

0

5

10

15

20

25

30

35

40

45

10

20

30

40

50

60

70

Rainfall, mm Nr-Median Far-Median

Average Reference Evapo-transpiration Against Mean Annual Rainfall in Selected River Basins in Water-Scarce Region

Sr.No

Name of theBasin

Mean Annual Rainfall (mm)

AverageAnnualWaterResources1mm)

EffectiveAnnualWaterResource2

(mm)

ReferenceEvapo-

transpiration3

(mm)

Upper Lower Upper Lower

1 Narmada basin 1352.00 792.00 444.70 937.60 1639.00 2127.001 Narmada basin 1352.00 792.00 444.70 937.60 1639.00 2127.00

2 Sabarmati basin 643.00 821.00 222.84 309.61 1263.00 1788.80

3 Cauvery basin 3283.00 1337.00 316.15 682.80 1586.90 1852.90

4 Pennar basin 900.00 567.00 193.90 467.80 1783.00 1888.00

5 Krishna basin 2100.00 1029.00 249.16 489.15 1637.00 1785.90

Effect of Watershed Interventions on Effect of Watershed Interventions on RunRun--Off Off

G-S Rainfall-Runoff, Cms

100

120

140

Total Rainfall, Cms Total Roff, Cms

0

20

40

60

80

100

66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 0 1 2 3 4 5

Year

Marginal cost & benefits of water harvesting with different stages of basin development

Marginal benefit (Social,

Environmental and

Economic)

Marginal Cost/ benefit

Wet

O

Economic)

Marginal Cost/ benefit

Wet

Year

Degree of Water Development

Wet Year

Dry Year

Increasing unit cost for higher runoff collection

Trade off between Economics and Hydrological

Opportunity

0.25

0.00

0.05

0.10

0.15

0.20

1 3 11.89MCM

Rs.