ACTION RESEARCH ON WATER BUFFERING IN BANGLADESH

SCOPE AND OPTIONS FOR APPLICATION IN BANGLADESH

Albert Tuinhof – Acacia Water

Dhaka, 24 February 2011

University of Dhaka

Geology Department

Department of Public health Engineering

(GROUND)WATER BUFFERING IN BANGLADESH

• Why is storage important ?• Water buffering: the concept• Technical options • Possibilities in Bangladesh• Examples/tools• Cost and benefits

Source Abstraction Treatment Distribution Point of use

Water supply provision

Water res. dev. & mgt.

Storage needed to bridge gaps in supply

and demand

Resource mgt and water supply need more integration

STORAGE: BETWEEN RESOURCE AND SUPPLY

SOME FIGURES

• Surface water storage per capita– Ethiopia 43m3

– South Africa 750m3

– North America 6150m3

• Village ponds or domestic rainwater storage could add 2-5 m3 per person per annum

• Each additional 10mm groundwater recharge could add 50-100 m3 per person per annum

4

WHERE STORAGE IS INADEQUATE

5

WHERE THERE IS STORAGE

6

The Economist 22 May 2010 :

In semi- arid Gujarat agriculture has grown at an average of 9.6% since 2000, due to the creation of 500,000 small ponds,

dams and such like

STORAGE IS BUFFERING

Its not about allocation scarce water but to catch and retain water and extend the chain of use and reuse as possible within a basin

MANAGING THE WATER BUFFER: THE CONCEPT

Quick scan to assess hydrological, socio-economic and environmental conditions and water buffering needs on basin /catchment level

Selection of appropriate Recharge, Retention and Reuse) interventions using tools and valuation techniques for decision making

Focus on rural water livelihoods but also for urban ws and productive use

Goal: upscaling (pilot projects) and integration of buffer management in IWRM /Basin Water Management

RAIN, SURFACE AND GROUNDWATER

• Local tanks, surface water and subsurface storage (active use of aquifer) for both water- and food security

• Subsurface storage (MAR) is largest potential in terms of quantity (m3 ) and quality protection

9

MAR

CLASSIFICATION OF 3R SOLUTIONS

Rain water

Surface runoff

Stream flow

1 infiltration ponds / recharge basins/ percolation tanks

X GW2 flooding and irrigation X GW4 ditch, furrow, drains, burrowing, punching x3 X GW

B 1Induced

infiltrationbank infiltration X GW

Well/gallery + pump

1 deep injection well (ASR, AS-TR) X *1) X GW2 shallow injection well / recharge shafts X X *1) GW3 dug well /recharge pits X X GW

1 gully plugging /small weirs X GW/M3 sand dams /gabions /sub surface dams X GW5 recharge dams /percolation tanks/ check X GW/SW6 maintaining river beds/stream channel mod X GW/M

1 barriers, bunds, trenches X M3 terracing, vegetation strips etc X X M4 ponds / reservoirs /checkdams X X SW Pump5 RW interception + tank/reservoir/cistern X SW Pump/tap

x 2) SW: surface water, RW: Ra inwater, GW: Groundwater ; M:Moisture

E

Run-off and rainfall

harvesting

x 1) infi l tration after tempory s torage and pre treatment (fi l tering), may a lso make use of other sources l ike treated waste water or urban s tormwater run-off

Mainly Well + pump

Transpiration

ASurface

recharge

CPoint

rechargeWell + pump

drain/well /gallery +

pump

In channel recharge and

retentionD

CodeRecharge/

interceptionMethod

RainfallRetention

x2) Reuse

3R and MAR

MAR:

building infrastructure and/or modifying the landscape to intentionally enhance groundwater recharge

Recharge enhancement provides additional storage

Coastal: Salinity

Barind Tract: Quantity

Flood Plains: Arsenic

Chittagong Hills: Difficult Geology

Madhipur Tract: Overexploitation

Sylhet: surfaceClay and geology

Coastal zone:Salinity

TistafanSandy deposits

POTENTIAL IN BANGLADESH

POTENTIAL IN BANGLADESH

infiltration ponds / recharge basins - + - - - - -flooding and irrigation - + + - - + -ditch, furrow, drains, burrowing, punching etc - - + - - + -

Induced infiltration

bank infiltration - + - + - - -

deep injection well (ASR, AS-TR) + - + + + + -shallow injection well / recharge shafts + + + + - + -dug well /recharge pits - + + + - + -

gully plugging/ small weirs - + - - - - +sand dams /gabions /sub surface dams - + - - - - +recharge dams /percolation tanks/ check dams + - - + - - +maintaining river beds /stream channel modifcations

barrier, bunds, trenches etc. + + - + - - -terracing, nefarim, veg strips etcponds / reservoirs /checkdams + + + + + + +RW interception + tank/reservoir/cistern + + + + + + +

Run-off and rainfall

harvesting

Tista Fan

x1): Includes Greater Dhaka x2) includes Chapai Nawabganj area

Surface recharge

Point recharge

Recharge/ interception

MethodSylhet

DepressionCoastal Plains

In channel recharge and

retention

Barind Tract

Flood Plains X2)

Madhupur Tract x1)

Hill Tracts

Production wells drilled along the Mohanandan River abstract part of the water from the river. Simulations with a groundwater model and with a Bank Infiltration Simulator (NASRI) show that approximately 30% (dry season) to 60% (wet season) of the pumped water (at 30-50 m) originates from the river with travel times of 5-10 days (wet season) to 30-40 days (dry season).

BANK INFILTRATION:CHAPAI NAWABGANJ

Subsurface storage

Abstraction well

- Capital cost : 8,000-12,000 USD- Annual cost: O&Mand monitoring: 1,000-1500 USD- Water storage provided: 2,000 m3/rainy season - Number of users: 20-30 families (100-200 users)

SAND STORAGE DAMS

Khulna

Sundarbans

SHALLOW GROUNDWATER INFILTRATION

Pilot Study of fresh WR in the coastal belt (IWACO, UNICEF, 1985)

Infiltration testing

ACTION RESEARCH ON GROUNDWATER BUFERING IN BANGLADESH , PHASE 2

173R solutions to improve Water Quality and Quantity

Fresh water from ponds and roofs can be injected in the shallow (brachish) aquifer during monsoon for abstraction during dry season

2 tests sites are constructed and tested after the 2010 monsoon

2 new sites will be added for testing during the 2011 monsoon

A 3D model was made to guide the testing and to be calibrated for future desings and upscaling

INFILTRATION TESTING

Upozila Population 2006

Area km2 % affected

Kaliganj 275.000 329 100

Assasuni 268,000 377 100

Syamnagar 337,000 1969 100

Batiaghata 151,000 237 20

Paikgacha 267,000 378 50

Koyra 207,000 1583 100

Dacope 169,000 1050 100

Rampal 192,000 276 80

Mongla 160,000 1502 100

Morrelganj 376,000 439 95

Sarankhola 123,000 825 100

Total 2,526,000

UPSCALING POTENTIAL SHALLOW GW INFILTRATIONIN KHULNA AND SATHKIRA DISTRICT:

Experiences can also be used to assess and test the application elsewhere in Bangladesh

Station Country

Coordinates Longitude xxx Latitude xxx

Town DhakaProvince /District

Country Bangladesh

Rainfall data

Period: 1953 1982

Number of years ny 30

Number months nm 360

Average annual rainfall (mm) 1951

Fixed input parameters

Leakage losses (%) L 5Run-off coefficient f 0.8

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Average

5 5 5 6 6 6 6 6 5 5 5 5 5.4

DHAKA BANGLADESH

Consumption (lit/cap/day)

0.0

50.0

100.0

150.0

200.0

250.0

300.0

350.0

400.0

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Ave

rag

e ra

infa

llMonth

Average monthly rainfall

SIMULATION MODEL RAINWATER HARVESTING

Catchment area (m2) /cons. Ac 2 Vc 0.8

No. of months with Sl<1 : 22No. of months with SL=0 : 0

0.98

Storage capacity (m3) / cons.

Reliability (St): aggregated supply level over whole period

0.00.10.20.30.40.50.60.70.80.91.0

1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361

Su

pp

ly L

ev

el

Months

Dhaka, Bangladesh, 1953-1982

Ac 2 Vc 0.8 reliability St 0.98

Parameter A(m 2) V (m 3) No.

Roof surface (A) 500 200 250

Tank capacity (V) 25 10 13

No. consumers 100 40 50

select values for red numbers

Design parameters of RHS for selected Ac and Vc which are entered in above graph

0.98 2 4 6 8 10 120.8 0.98 0.99 1.00 1.00 1.00 1.00

1 1.00 1.00 1.00 1.00 1.00 1.00

2 1.00 1.00 1.00 1.00 1.00 1.00

3 1.00 1.00 1.00 1.00 1.00 1.004 1.00 1.00 1.00 1.00 1.00 1.00

Vc

Reliabiliy (St) for a range of Ac and Vc Ac

sensitivity analysis

Assign monetary values to non financial cost and benefits

value and discount all cost and benefits

determine Net Present Value (NPV) and Cost/Beneftit Ratio ( BCR) for decision making

Carry out water buffer quick scan

Identify potential 3R solution(s)

Identify cost & benefits of 3R solution(s) and of the "no intervention" option

Determine whether C&B can be measured and quantified

Select and apply valuation tool

Techniques : Revealed Preference Stated Preference Benefit Transfer

YES NO

ECONOMIC VALUATION OF STORAGE: 3R CBA

OVERVIEW OF COST /BENEFITS OF STORAGE

COST ITEM VALUATION

CONSTRUCTION Incl. design etc USD

ADDITIONAL COST Land acquisitionPower supply

USD

SOCIAL/ENV. COST EIA/SIA / Mitigation USD - USD/yr

O&M Incl .monitoring USD/yr

BENEFITS ITEM VALUATION

REDUCED COST OF WATER Drinking, livestock, rural industry, small scale irr. USD/yr, based on

interviewsINCR. PRODUCTIVITY See above: income increase

HOUSEHOLD BENEFITS Improved health, more time Indirect, through valuation methods.

SOCIAL / COMMUNITY BENEFITS

Cohesion, security, education

ENVIRONMENTAL BEN. Biodiversity, vegetation

Village household income (Rs thousand/yr)

1996 2004Bhalgudi 18,000 26,000Chikhalgaon 20,000 28,000Hadshi village 24,000 30,000Nanegaon 62,000Nadgaon 20,000average 20,667 33,200

Location agricultural income (Rs thousand/yr)

before afterUSBed 18.00 36.00Dsbed 10.00 28.00Samrapur 28.00 35.00Vajapur 16.00 19.00Nedardi 15.00 33.00Control 22.00 23.00total

Kolwan Valley

3 check dams

Population 15,000

Catchment area 80 km2

EXAMPLES OF MEASURED BENEFITS : INDIA

Satlana Carr

3 check dams/1 percolation pond

Population 4250

Catchment area 20 km2

Thank you