Workshop on ACTION RESEARCH ON GROUNDWATER BUFFERING IN BANGLADESH 24 February, 2011 Prospects of Artificial Recharge for Augmentation of the Upper Dupi Tila Aquifer in Dhaka City, Bangladesh Sarmin Sultana Department of Geology, University of Dhaka
Presentation Outline ● ● ● ● What is AR & what are the techniques Why AR in Dhaka city What is the source of water for AR Objectives of this study Results and discussion Conclusions On going research
The Megacity Dhaka Needs no introduction Water Demand Supply
Why AR in Dhaka city Uniqueness of Dhaka in terms of GW problem ● ● ● GW Dependant City No imported water Big Gap between supply and Demand Heavy GW abstraction and well deepening Rate of water table decline 3. 5 m/y Aquifer dewatering No GW management !
Cone of depression 1970 1980 1995 2007 GW hydrograph of Upper Dupi Tila Water Table Elevation Contour demonstrates a steady down ward slope. for dry season as on 2008
Is going Deep a sustainable Solution?
Rainfall in Dhaka Mirpur (GT-2648010) Dhaka station (R 009} GW hydrographs and corresponding 7 -day rainfall are plotted for 1977 and 1993.
Objectives ● ● ● To estimate the current open space available for natural recharge to take place; To delineate potential zones for implementing site-specific artificialrecharge techniques using GIS analysis; and To assess suitability and applicability of Artificial Recharge in Dhaka.
Natural Recharge Area Map Area in % Bar Diagram of Recharge Area Classes
Infiltration Test at the pond of Institute of Fine Arts Status of the pond immediate after rain Status of the pond after 3 days from raining
Potential Zones Rules for selecting prospective zones of artificial recharge
Volume of Rainwater Available in Dhaka city (Sources: BBS City area (sq. km) Avg. annual rainfall (m) Total volume rainfall (M L) No of total concrete house available for rain water collection Each roof area (sq, m) Total roof area (sq. km) Yearly total volume of rainwater (ML) Daily Total Volume Of Rainwater (MLD) 370 2 740, 000 6, 78, 000* 110 74. 58 149160 408. 65 If 30 % of this water can be collected, then more than 100 MLD water will be available to recharge the aquifer artificially. Production well Number of abandoned wells of DWASA. Abandoned well R 2 R 3 R 4 R 5 Total 175 Production well R 1 47 21 15 6 264 Other Options Dredging and re-excavation of khals Avoid construction along faults River dredging and Bank filtration Systematic Clay Mining
Site Specific Artificial Recharge Technique Map Rules for selecting sites of definite artificial recharge methods No of Locatio ns Clay thickness (m) Method 6 10 – 15 Trench pit 6 40 – 50 Injection well 2 3– 7 Dug well 5 – 15 Lateral trench with vertical shaft 1 0 – 10 Spreading Technique 2 20 – 25 Retention pond with well 2 25 – 35 En-echelon Dam 2 15 -30 Check dam 3 Dhaka has high potential for Artificial Recharge
Workshop on ACTION RESEARCH ON GROUNDWATER BUFFERING IN BANGLADESH 24 February, 2011 THANK YOU
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