Mapping Economic Feasibility of Managed Aquifer Recharge System

*Deepak Lakahnpal & Dr. S.K. Sharma

Abstract

A multi-stage process is recommendable towards determining economic feasibility of potential MAR projects. Various steps include (i) establishing feasibility of suitable potential aquifers to recharge,(ii) quantity and quality of source recharge water and its match with quality of native ground water aquifer under recharge,(iii) and demand  for water and its potable and non-potable uses. Cost of MAR projects include the capital cost as well as O&M and financial cost. The capital costs are fixed one-time cost incurred during design & construction of MAR projects and include cost on account of land/feasibility, field testing and the design and construction cost. The O&M cost includes cost on account of labour, energy. Water quality testing, maintenance cost, pre and post treatment cost and raw water cost. The total values of recharge water include its development and extraction value and sedentary value. The economic feasibility of MAR projects should be driven by a multitude of approach to include, evaluating the suitability and availability of aquifer systems under recharge,the recharging source water and demand of source water for its potable/no-potable uses.

1. Introduction: Managed Aquifer Recharge (MAR) is intentional & purposeful banking of aquifer system for later use well as for determining environmental and ecological benefits. The MAR is achieved through area-specific feasible interventions that principally include the infiltration basin, pits, trenches, injection well-bores, the lake and river bank filtration, in-stream modifications, modular rain-tank systems and Aquifer& Recovery System. The economic benefits and efficiency of MAR system basically depend on hydro-geological, morpho-dynamic and technical framework of an area that include the hydraulic conductivity & ground water gradient, constructional design and operational maintenance of recharging structures.
2. Addressal of Issues: In the determination of relative efficiency of different artificial recharging measures & structures, the following criteria is to be kept in view:

• Declining ground water levels and diminishing ground water resources
• Inadequacy of ground water in lean periods
• Empty storage capacity of Aquifers
• Physical efficiency of water harvesting vis-a-vis storage capacity of aquifer regimes
• Quantity & quality of  source recharge water and its  match with native ground water quality
• Dominance of indirect recharge in Arid-region and direct recharge in Humid areas
• High and low permeability soil regions
• Brackish Ground water Aquifers(BGWAs)
• Soil infiltration rates, aquifer storage capacity, landuse-lancover types
• Aquifer recharge by Recycled water and health impact

• Factors Influencing Cost of MAR Schemes: These include:

      Infiltration, Percolation & Injection-well techniques

        (i)Factor of variability and availability of Rain-infiltration run-off

        (ii) Infiltration, percolation and injection well techniques

       (iii) Efficiency of Rain Water Harvesting (RWH) structures

       (iv) Cost of land in identified MAR regions

       (v)  Design and O&M of MAR structures

       (vi) MAR measures, recharging structures and divers environment

     (vii)  Pre and post-recharge treatments

    (viii) Artificial recharge feasibility and construction

    (ix)  Source recharge availability & water transfer

    (x)  Soil types, soil permeability and infiltration rates

    (xi) Aquifer types (unconfined/confined) & Aquifer storage capacity

   (xii)  Factor of aquifer transmissivity and hydraulic gradient

   (xiii) Infiltration and injection rates

   (xiv) Socio-economic, legal, technical and regulatory factors

  (xv) Energy Pricing

  (xvi) Monitoring cost (monitoring of ground water or recharge water quality field-kit based lab analysis cost)

 (xvii) Administrative & personnel management costs

• Procedures for Examining Economic Benefits of MAR Schemes:

         Step-wise procedures considered in evaluating cost & over all benefits of MAR scheme include:

    Step1:     Analysing the change in quantity and quality resulting from execution of MAR projects.

    Step2:     Economic value of change in ground water quantity & quality

    Step3:     Social and environmental value of water

In the paper only MAR system with storage-aim are considered. Evaluation of the benefits is somewhat difficult to quantify: The increased storage via MAR increases volume of water for later use. The pumping cost to lift water is reduced due to ground water build-up and rise ion water-table.

• Parametric Frame-work for Estimating Cost of MAR Schemes; It is as given below Table-1:

Table-1: Framework for Estimating Cost of MAR Schemes

• Cost Economics of MAR Schemes:  Principally & essentially the varied nature of geo-hydrogical, socio-economic & regulatory factors govern the cost of MAR scheme projects. A review of MAR scheme areas in India has revealed the complete absence of cost and financial data on managed aquifer recharge measures and tools. The paper only outlines the procedure to be adopted in assessing costs of MAR schemes in Indian context with particular frevelance to NCT Delhi. Artificial recharge scheme projects for recharging unconfined aquifers using natural untreated water are known to be relatively cheaper and economic in comparison to deeper aquifer recharge water. Paper discusses procedure of using natural Yamuna River water as well as source recycled water (treated water) for recharging alluvial and hard rock aquifer areas and describes a case each for NCT Delhi. Also scope for similar future work to be undertaken connected with economics of recharging ground water using Aquifer Storage & recovery and Lake- Bank Filtration as well as Modular Rain Tank (Atlantis system) methods of recharging ground water are discussed.

• Goal: Water Storage Aim of MAR Projects: These include:
• Storm Water Drains(SMDs)
• Aquifer Storage &Recovery (ASR) coterminous with Water Treatment Plant Complex  areas of Delhi Jal Board  in Delhi, were surplus water for recharging may be in existence.
• In-stream modifications and construction of Check dams in Delhi Ridge areas.
• Bhatti Abandoned Mines Area, South Delhi
• Case Applications: Following Type-cases are used to figuring out projected cost-estimates of projects & likely experience benefits & outcomes.

Case Study I. Storm Water Drains (SWDs): Kanjhawda & Narela Area of NCT Delhi.

Case Study II, ASR System conterminous with WTPs.

Case Study III In stream-modification & Check Dams.

The details underlying these study types with reference to their project-site areas in NCT Delhi are described:

Case Study Area I:

1. Storm Drains: Kanjhawda & Narela Areas, NW District Delhi: Framework Flow-Diagram of MAR Design is given as below:

Computation of Artificial Recharge to Ground Water through Proposed Interventions & Estimated Cost.

Compulate of Artificial Recharge to Ground Water through proposed intervention & Estimated Cost in given table-2 below.

Table-2: Artificial Recharge to Ground Water (SWDs)

The city drains that are free from domestic sewage can be identified and used for recharging ground water using storm water. A diagrammatic design leading to use of city drains & storm water management is shown in Fig-1.:

Case Study Areas II

Bhati-Abandoned Mine Area (South Delhi)

MAR Project Design: Design Flow  diagram is given as below:

The study Area Map is at Figure-2. Volume of Mine pits (14 Nos.) is given in Figure-3. Infiltration rate sof Mine pits vary from 2 to 28 mm/hr.

II.1 Infrastructure:

• Pit-basins under Artificial Recharge
• Distance between Source Recharge Water & Abandoned Pit basins.

II.2 Cost Functions:

• Altitude difference between Okhla Source Treated Water & Pit basin areas.
• Topographic contour map of a pit (as an example).
• Financial Cost: To include expenditure as account of
• Geological & Hydrogeological Investigation.
• Water transfer cost to recharge site depending on distance.
• Supply [pump line cost.
• Cost of land may be nil being Government Land.
• Infiltration basin area & infiltration test cost.
• Cost of Peizometer Monitoring Wells.
• Operating & Maintennace Cost (O & M):

Main expenses to include are:

• Recharge water, pumping system at water in-take site (Okhla, Delhi)
• Energy consumption of pumping equipment system depending upon flow rate & cost price of energy to supply recharge water to recharge sites.
• Cost of periodic monitoring of recharge water quality via piezometer well.
• Difference is altitude between source water area & REcyclying well.
• Livelised Cost:

Overall capital O & M cost over each year divided by annual volumes of water infiltration in pit-basins.

Case Study Area III: In stream-modification & Check Dams

Recharge Dam is a type of In-channel modification for MAR where artificial recharge is caused through base of pond build up behind a bund. The infiltration through stream bed enhances recharge downstream of check dam structure & raises ground water levels & yield in wells for abstraction of water supplies for irrigation & allied uses.

A GIS-Based method is used to delineate micro-catchments thereby capturing run-off through cascading structurs & small check dam locations would expectedly range from 1 to 2m with yield ranging from 1 to 3 litres per second.

The case study for Check Dam sites location in Ahravali Ridge Area of Delhi with a sample figure is described & shown in fig-4. The index of map reveals the watershed data assessment for locating run-off production area in macro & micro-catchments in Delhi Ridge area where small check dam structure are located that can be constructed through an estimated approximate cost of Rs. 7-10 lakh.

The monitoring wells suggested to be located downstream of check dams would reveal the area of influence downstream of dam which could possible be 1 to 2 km downstream. The stable isotope studies would reveal the travel time taken by recharged water to ground water table in such wells.

Case Study IV: ASR Projects: The ASR projects are proposed to be considered at the following Eight Water Treatment plants (Table-An ASR project is chosen at Okhla Water Treatment Plant as DJB has indicated priority for this. An injection well is proposed opposite to pump house and across road along the boundary wall to minimize piping lengths and, if possible, use existing pumping facility for injection of water when demand is low. Provision of a pit around injection well is also proposed to use water during back washing of ASR well and water during cleaning of overhead tanks and water from other structures within Treatment plant.

Table-3: Proposed ASR Projects

Aquifer Storage & Recovery (ASR): The Aquifer storage and recovery is essentially the storage of water in an aquifer through a well when water is available which in the instant case is Urban Storm water and the recovery of water is from same well during water demand. It is an Injection well system for seasonal storage of water there can be separate infiltration and  extraction wells called Aquifer Storage Transfer Recovery (ASTR). Depending upon availability of source storm water for injection and storage, the number of ASR wells can vary from a single well to a well-field comprising a large number of wells as feasible.

A schematic representation of an Aquifer Storage & Recovery well is shown as Fig-5

• Estimating Cost of MAR Schemes: Briefly the investment,operating and life-cycle costs could be determined  for proposed MAR projects as outlined below:

  (i) Investment cost: These include:

• Cost of preliminary studies of recharging area that includes hydrological and hydrogeological studies
• Cost on account ofsource water-transfer infrastructures including supply pipes
• Cost of treated recharge water
• Land cost for construction of infiltration structures
• Cost of design and construction of infiltration structures
• Cost of montoring structures(piezometric wells)

  (ii) Operating cost: These include annual and recurring costs as:

• Cost on account of water withdrawal from river, canal etc.
• Water-intake maintenance cost
• Pre-treatment and operational cost
• Annual expenses: administrative and personnel management expenses

  (iii) Levlised cost: It is the annual cost divided by annual volume of recharge and covers the cost on account of life duration of MAR project.

• Economics of various MAR Methods for projects identified/described: This is as given in Table-4 below:

1. Conclusion:

Ground Water, in India, serves as major source of water supply both for rural and urban communities. Managed Aquifer Recharge(MAR) system. In India, have  eight  broad component types which include (i) Water spreading, (ii) Induced Recharge as Lake and River bank infiltration system(LBI & RBI),(iii) In-channel stream-modifications (iv) Aquifer Storage & Recovery Systems(ASR & ASTR wells),(v) Check dams and Sub-surface Dykes),(vi) Atlantis Modular Rain-tank systems  (vii) Pits, trenches and shafts driven with boreholes and (viii) Conventional Roof-top Rainwater Harvesting. A synoptic account of economic & feasible MAR system of NCT, Delhi are discussed.

Economic appraisal and assessment of MAR systems depends on soil characteristics, aquifer storage empty space and storage capacity, location of source water quantity & quality as well as land use and land cover details of area under water harvesting and recharging.

Water as economic commodity and good is essential for life and environment since it bears both social and environmental values. The capital and investment costs include (i) inventory and study of recharge site,(ii) cost on account of water abstraction,(iii)cost of source recharge water, its quantity, quality and treatment as necessary,(iv) related operational and maintenance costs as well as the cost on account of the type of recharging method.

REFERENCES:

Adriana  Valcu-Lisman;   Economic  considerations of Managed Aquifer recharge

A.M.J. Meijrink;  Application of Remote Sensing and  Geographical Information System; Netherlands Hydrogeological Research in Cooperation; Delft 1994

Dillon, 2005, O. Dillon: Future Management of  Aquifer Recharge, Hydrogeol.J.,13(2005),pp 313-316

Pyne, R. David G 1995. Groundwater Recharge and Wells: A Guide to Aquifer Storage Recovery. Lewis Publishers, Boca Raton, FL.

By *Deepak Lakahnpal, Chief (Civil), WAPCOS Ltd., Dr. S.K. Sharma, Consultant (Ground Water) Wapcos Ltd.  & Former Member, CGWB,Govt. of India