Site selection and cost-benefit analysis for artificial recharge in the

Site selection and cost-benefit analysis for artificial rechargein the Baghmalek plain, Khuzestan Province, southwest Iran

Nasrollah Kalantari & Kazem Rangzan &

Satish Shripad Thigale & Mohammad Hosein Rahimi

Abstract Available hydrogeological data for the Bagh-malek aquifer, southwest Iran, suggest that in order tocounter progressive depletion of groundwater, but at thesame time meet the growing demand on groundwaterresources, artificial recharge should be considered. Thesuccess of artificial recharge schemes requires the inte-gration of many types of data and information. The primeprerequisite in establishing an artificial recharge schemeusing the surface spreading technique is identification of asuitable site. Therefore, an integrated investigation,including a detailed assessment of surface and sub-surfacegeology, and hydrogeological surveys were undertaken.The potential of harvesting storm waters, considering theirquality and suspended loads, has been evaluated. Usingthis background, three sites (including basins and checkdam) for artificial recharge are suggested in the north andnortheast of the area, where the thickness of coarsealluvium is greatest. On the basis of the collected data,(1) the rate of recharge that can be achieved at the threesites is approximately 2.2 million m3 per year, (2) thecost–benefit ratio is 1:1.32, and (3) the analysis suggeststhat the project could recover the investment within3 years.

Keywords Baghmalek aquifer . Artificial recharge .Groundwater management . Site selection . Iran

Introduction

With increasing population, demand for more reliablesupplies of water has increased. The situation is critical inplaces where groundwater is the only accessible waterresource and withdrawal of water is more than the rate ofrecharge. Consequently groundwater deterioration and/oran imbalance in the groundwater budget is created.Khuzestan Province of southwest Iran has four permanentrivers and several ephemeral rivers with unreliabledischarge; in 2008 the total annual available water wasabout 14×109 m3 (Water resources status of Khuzestanbasins, unpublished data, 2008). There is a considerablenetwork of irrigation systems associated with permanentrivers for irrigation of fertile soil which occupies a vastpart of the province. For several reasons, surface water cannot meet the demand: (1) most of the surface water movesaway as flash flood, (2) surface water is not availableeverywhere, and (3) there is a short flow period with smallrivers—for example, Abul-Abbas River has good waterflows close to the Baghmalek plain for only a few monthsand dries up quickly in low rainfall years. Therefore,many areas (for example, Baghmalek, Zevier chery,Kheran, Gale-e-tool, Izeh, Doselagh plains) in KhuzestanProvince depend solely on groundwater and the totalannual groundwater abstraction approaches 998.2 million(M)m3, which exceeds annual groundwater recharge. Dueto geology and rainfall patterns, this important waterresource is unevenly distributed both spatially andtemporally; with the exception of drought years, annualrainfall of the Khuzestan Province territory normallyvaries between 240 and over 600 mm in low and highaltitudes respectively. Groundwater has been withdrawn inthe last couple of decades for community water supplyand agriculture. As a result of over-pumping of ground-water resources and the small amounts of recharge relativeto extraction rate, water tables have declined and, in someareas water, quality is at risk (Kalantari and Rangzan2000). The Baghmalek agricultural plain (Fig. 1) providesone of the promising aquifers in Khuzestan Province andgroundwater is often the only source of water supply fordrinking as well as agriculture. The withdrawal of waterfrom the Baghmalek aquifer is more than the rate of

Received: 1 December 2008 /Accepted: 2 November 2009Published online: 26 November 2009

© Springer-Verlag 2009

N. Kalantari ()) :K. Rangzan :M. H. RahimiGeology Department,Shahid Chamran University,Golestan Blvd, Ahvaz, Khuzestan, Irane-mail: [email protected]

M. H. Rahimie-mail: [email protected]

S. S. ThigaleGeology Department,University of Pune,Ganeshkhind Road, Pune, Maharashtra 411007, India

Hydrogeology Journal (2010) 18: 761–773 DOI 10.1007/s10040-009-0552-x

recharge and groundwater level has receded. To combatwater-table decline, managed aquifer recharge is anattractive option (Mousavi and Rezai 1999; Krishnamurthyet al. 2000; Mandal and Singh 2004).

A limiting factor in developing artificial recharge ofgroundwater is site selection (Bouwer 2002). A lack ofsuitable sites often causes neglect of artificial recharge as awater management technique (Pyne 1995; Kalantari andRangzan 2000; Abu-Taleb 2003). Most previous studieson site selection consider the general concepts only, butsite selection has many restrictions and is often deter-mined by local conditions, both natural and man made(Bouwer 1989; Al-Ismaily and Probert 1998). The inves-tigation of the feasibility of an artificial recharge siteshould be based on amalgamated studies that cover all theaspects of groundwater recharge (Kowsar 1991; Jain1996). The study presented here, in the Baghmalek plainof Khuzestan Province, considers the local conditions indetail, and comprises a combined investigation of allrelevant aspects, including physiography, geology, hydrol-ogy, hydrogeology, hydrochemistry, measurement of run-off suspended material, grain size analysis, and infiltrationcapacity. In addition, the suitability of artificial rechargestructures, the capacity of the recharge sites and the cost-benefit ratio were also considered. It is shown that suchschemes do not have to be prohibitively expensive to setup, and pay-back periods can be relatively short.

This report describes (1) the potential sites for artificialrecharge in the area, and the most suitable artificialrecharge method to augment groundwater resources; (2)computation of the annual rate of recharge from waterretention schemes, and (3) estimation of the cost of the

water retention structures and evaluation of the cost–benefit ratio.

General description

The Baghmalek territory is formed of two physiographicunits; the Baghmalek plain and the surrounding heights ofdominantly conglomerate and gypsum rocks (Fig. 1). TheBaghmalek plain is an intermountain plain, lying in theZagros structural belt. The Baghmalek plain occupies anarea of approximately 55 km2 and is situated between 49°42′ and 50°8′E longitude and 31°26′ and 31°41′N latitudeto the northeast of Ahvaz in Khuzestan Province. Theaverage elevation of the Baghmalek plain is 725 m abovesea level (m asl), the average minimum and maximumannual temperatures are 7 and 37°C, and the overallclimate is temperate. Based on the last 30 years of data,since establishment of the meteorology station in 1979,the mean annual precipitation is 640 mm with mostrainfall occurring in winter (November to February). Thedata of the last 23 years, since development of themeteorology station in 1984, indicate that the meanannual temperature, relative humidity and evaporationare 21°C, 58% and 1,445 mm respectively.

The absence of substantial elevation differences andthe presence of the fertile soil in most parts of the studyarea make it agriculturally productive. The area has apopulation of about 110,000 people who are mostlylocated in Baghmalek city: the combined population ofthe villages exceeds 5,000. Most of the farmers own theirland, with farmed land occupying about 45 km2 (4,516 ha)

Fig. 1 Location map (Khuzestan Province, Iran) and drainage network in the district of Baghmalek

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and the main agricultural cultivation in the sandy loamsoils consists of wheat, oats, cucumber, watermelon,onion, rice, corn and tomato. Agriculture is the maingroundwater consumer in the area accounting for over90% of the 15 Mm3 annual withdrawal and is generallyused to irrigate crops from August through to thefollowing June.

Results and discussion

Watershed characteristicsThe watersheds of three ephemeral streams, Tapeh tele-vision (1), Kayani (2), and Sherkat (3) rise from DerbMountain: the former two (1 and 2) join the ephemeralGelal Stream while the latter (3) is a tributary of theephemeral Paderazan Stream (Fig. 2). The drainagesystem is dendritic and the summarized characteristics ofthe Tapeh television, Kayani and Sherkat sub-basins aregiven in Table 1.

GeologyExisting geological maps and additional field informationwere used to identify the lithological units (Figs. 1 and 2).The Bakhtyari conglomerate formation (Pliocene) cropsout in the north and northeast and in the remaining areasthe Gachsaran formation (lower Miocene) occurs. TheGachsaran formation is composed dominantly of gypsum,and the occurrence of marl and salt interbeds is not

unusual but gypsum outcrop is only observed in the studyarea. Quaternary sediments overlie both formations asshown in Fig. 2. The Baghmalek plain in the north and thenortheast is covered by Quaternary gravel, which has avariable clast size, and the remaining parts of the area aremainly covered by sandy loam soil. Tube well andpiezometer lithological logs indicate that the Quaternarysediments are predominantly gravel but the gravels areinterbedded with other sediments (Fig. 3).

Fractures and faults occur in the northeast and north-west of the area, but the effect of the regional Izeh Faultand shear zone on compacted conglomerate rock hasresulted in a higher density of these features in thenortheast. The structural features mainly control thepermeability of the conglomerate formation, while inaddition to these lineaments, solution cavities also governgypsum formation porosity. The most widely distributedforms of lineaments in the surrounding rocks of the plainare fractures. The density of longitudinal and lateralfractures is very significant in the northeastern part ofthe study area and the fracture widening approaches a fewcentimeters.

As shown in the rose diagram in Fig. 2, the longitudinaland lateral fractures are trending N140–150 and N40–50respectively. Apart from fractures, several normal faultsextending NE–SW occupy the conglomerate formation inthe northeast and the north. In addition to these smallscale faults, two outstanding faults (Izeh and Baghmalek),trending N–S and NW–SE, cross the Baghmalek plain(Fig. 2). Faults and fractures have a crucial influence on the

Fig. 2 Local geology and location of the recharge sites

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hydrogeological properties of the plain. Izeh Fault is aregional basement structure and its occurrence has createda shear zone which has, in turn, resulted in concentrationof fractures and small faults in the northeast due to thebrittle nature of conglomerate rock. These structuralfeatures are favorable locations for rain percolation andalso provide suitable underground pathways for watermovement towards the central part of the study area(Figs. 4 and 5).

HydrogeologyExtraction for drinking, industry and agriculture occurs at47 boreholes. The depth to the water table ranges from 15to 30 m (Fig. 4) and the thickness of the saturated zoneranges from 55 to over 75 m. The piezometers andexploitation wells (Figs. 2 and 4) range in depth from 35to over 50 m and 70 to 105 m respectively. Well yieldsrange from 20 to 39 L/s, the higher yields being found inthe north and northeast. Water-table elevation varies from693 to 845 m asl and groundwater originates dominantlyfrom the east, northeast and the northwest and movestoward the center of the basin (Fig. 5).

The annual amount of groundwater withdrawal andrecharge varies, depending heavily on rainfall. The

estimated groundwater recharge from the alluvial plain,the highly fractured conglomerate in the northeast, and theconglomerate and gypsum formations in the north andnorthwest, in the year 2006, was 4.3, 4.2, and 1.7 Mm3,respectively. Based on Richard (1998) and general Darcyequation , rainfall and groundwater flow recharges werecalculated. In the same year, groundwater abstraction fromboreholes and wells of the area was about 15 Mm3. Theannual recharge rate and extraction amount controlgroundwater levels and, as is evident from the hydrograph(Fig. 6), the fall in groundwater level was, on average, 5 mbetween 2000 and 2006. Since the year 2000, due to risein withdrawal and reduction in recharge, water level hasbeen falling rapidly. Although the increasing groundwaterextraction has caused water-table decline, the primereason for such decline is the significant drop in rainfalland its subsequently reduced contribution to the rechargeof the aquifer. The fall in groundwater level hasnecessitated the consideration of integrated water resourcemanagement, including artificial recharge.

Infiltration test and hydraulic parametersTo obtain information on upper soil layer drainagecapacity, an infiltration (I) test has to be undertaken

Table 1 Physical characteristics of the sub-basins

Sub-basin A (km2) L (km) S (%) BR D (km/km2) H (m asl)

Tapeh television (1) 4.1 4.52 19.4 3.61 2.95 1,325Kayani (2) 5.9 5.02 15.2 2.57 3.06 1,082Sherkat (3) 3.35 3.66 3.4 2.96 5.1 780

A area; L length; S net slope; BR bifurcation ratio; D drainage density; H average elevation

Fig. 3 Lithological logs of piezometers (locations shown in Fig. 2)

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Fig. 4 The location of wells and depth to water table contours

Fig. 5 Piezometer locations and water table elevation contours (meters above sea level)

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(Abu-Taleb 1999; Allen 2002). At each location (Tapehtelevision, Kayani, and Sherkat), several infiltration testswere conducted with double- ring infiltrometers, as wellas using ponds and hand excavated pits. Hydraulicconductivity (K) was measured using the inverse augermethod (Reynolds and Elrick 1985; Kuraz 2001).Pumping test data from alluvium boreholes wereanalyzed using the Boulton and Strelestova (1976)method to obtain estimates of transmissivity (T) andstorage coefficient (Sy). Porosity (n) was estimated, notmeasured. The results from these tests are summarizedin Table 2.

RunoffThe mean annual rainfall of the area as a whole is about640 mm. Precipitation occurs in storm events as well ascontinuous rain, the former being of short duration andhigh intensity, the latter of long duration and low intensity.Runoff estimation is a prerequisite for design of infra-structures in artificial recharge schemes, but runoff dataare often not available. Therefore, in such circumstances,if fairly long rainfall records are available, the resultingrunoff can be derived from empirical formulae. In thepresent study, for more precision of the data and based onprevious experiences (Kalantari and Bazarafkan 2003)using empirical methods to estimate runoff, the Justinapproach was used. This method (Justin 1972) is based onsimilarities in characteristics of the watersheds, and thedata of the rain gauge-bearing watersheds are used toestimate the runoff of ungauged watersheds. The Justincoefficient (K) is determined and used in the following

equations to estimate the annual runoff of the watershedsbased on Justin method.

S ¼ H max�H minffiffiffi

Ap ð1Þ

R ¼ W

Að2Þ

K ¼ R 1:8T þ 32ð ÞSO:155P2 ð3Þ

A = area of watershed (km2); H max = maximum(elevation) of the basin (km); H min= minimum elevationof the basin (km); W = annual discharge of the watershed(Mm3); P = annual average rainfall (cm); T = averagetemperature of the basin (°C); R = runoff (m); S = slope(m/m); and K is the Justin coefficient.

The Gelal watershed which contains rain gauge dataand, from the point of view of geology, climate,vegetation cover and soil, is very similar to theunknown (ungauged) watersheds (Tapeh television,Kayani, Sherkat) was taken as the known watershed.The coefficient (K) for the known watershed wascalculated and, by inverse processing, the annualrunoffs of the unknown watersheds were estimated(Table 3).

The design of recharge infrastructure needs carefulconsideration to have proper capacity to provide sufficientrecharge to meet demands, to accommodate storm waterrunoff, and to be stable during flash floods. Therefore, theSoil Conservation Service (1975) relation was taken intoaccount to compute return periods of the rainfall to predict

Fig. 6 Rainfall and groundwater levels in the Baghmalek plain from 2000 to 2006

Table 2 Physical characteristics of surface and sub-surface materials

Site I (mm/h) n (%) K (m/h) T (m2/day) Sy

Tapeh television (1) 135 38 14.5 540 0.17Kayani (2) 131 38 13.8 450 0.15Sherkat (3) 132 38 16 545 0.18

I infiltration, n porosity, K hydraulic conductivity, T transmissivity,Sy storage coefficient

Table 3 Annual discharge of the ephemeral streams (Mm3)

StreamTapeh television Kayani Sherkat

1.54 1.499 0.383

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the probable maximum discharge of the ephemeralstreams (Table 4).

HydrochemistryThe quality of recharging water is an important parameterin site selection for artificial recharge (Jordan et al. 2004).As the source of artificial recharge water in the area isrunoff, the surface water quality was monitored at fivewater sampling stations located at the Tapeh television,Kayani, and Sherkat, Gelal and the Paderazan ephemeralstreams. Samples were collected by directly dipping thecontainer into the streams in October 2006. The electricalconductivity (EC), temperature (°C) and pH were meas-ured in the field and samples were analyzed in thelaboratory for major cations (Ca2+, Mg2+, Na+ and K+)and anions (HCO3

− , SO42− and Cl−). The results are

summarized in Table 5.The low EC and total dissolved solids (TDS) values of

the surface water samples indicate that intermittent streamwaters have not experienced salinization. The overallsuitability of the surface water in the east and the northernpart of the study area is favorable for recharge and has thepotential to improve water quality in the aquifer. It isevident from Table 5 and Fig. 7 that major anions andcations of surface water in the east and the northeast arerespectively bicarbonate and calcium; however, the Pader-azan ephemeral stream water contains relatively highsulfate and calcium concentrations (Fig. 7) and theconcentrations of these two ions have elevated the TDSof the sample.

In order to evaluate groundwater quality, 22 monitoringwell samples were chosen for analysis based on theirvicinity to the recharge sites and the electrical conductiv-ity variation of samples taken from a larger survey ofwells. Groundwater samples were taken from outlet tubesat the exploitation wellheads in May 2006 (shown inFig. 4) and were placed in appropriate containers. Thegroundwater physico–chemical data are summarized inTable 6. The EC ranges from 388 to 1,454 μS/cm.Groundwater is dominantly recharged from good quality

surface water but water–rock interaction controls thechemical quality of these waters, particularly in the centraland northwest of the study area and some of the sampleshave experienced salinization due to sulfate bearing strata(Fig. 7). The dominant anion and cation of the ground-water samples in the east are bicarbonate and calcium,while in the west and northwest calcium and sulfate ionsare dominant.

The Parkhurst and Appelo (1999) program PHREEQCwas used to calculate saturation indices of the collectedsamples. All of the groundwater samples were saturatedwith respect to calcite and dolomite—only one sample wasunsaturated with respect to dolomite—and all of the sampleswere below the equilibrium state with gypsum (Table 7).The saturation index values of calcite (SIc) and dolomite(SId) reflect precipitation characteristics of the Baghmalekaquifer which minimize well-screen perforations and con-sequently reduce the wells discharge. On the other hand, thewater samples from the ephemeral streams—Tapeh tele-vision (SW1), Kayani (SW2) and Sherkat (SW3)—thatwere unsaturated with respect to calcite and dolomite,specify capability of the injected recharged water to reachbelow equilibrium the groundwater.

Suspended solidsAn important factor to be considered while designing astructure for artificial recharge is the amount of suspendedparticle material within the system. Determining theamount and type of suspended material in the storm wateris important in order to evaluate the impact of suspendedload on alluvial bed infiltration and recharge. A number ofstudies have documented the relationship between sus-pended load type and concentration and permeabilityreduction of the recharge system (Raeisi and Koohyan1998; Mousavi and Rezai 1999; Kalantari and Rahmani1999; Bouwer 2002). In the current investigation, threesamples of storm water from each tributary (Tapehtelevision, Kayani and Sherkat) were collected in the wetseason (October to December) in 2006 and the averagedried sample weights for each storm water site wererespectively 132, 143 and 123 mg/L. The composition ofthese suspended loads was measured using a MasterSizer(Malvern UK made Instrument) laser device, and togetherwere found to contain on average 39% sand , 47% siltsand 14% clay (Fig. 8). The high percentage of silt andsand originates from the calcareous conglomerate unit,and consists of a high percentage of calcium carbonate sois susceptible to dissolution. Thus, this component of the

Table 4 Probable maximum flood volume of ephemeral streams(m3) in different return periods

Sub-basin Return period (years)5 10 20 50

Tapeh television 514,900 630,800 757,400 888,000Kayani 466,300 568,800 667,900 795,100Sherkat 195,034 233,912 278,114 325,416

Table 5 Physico-chemical characteristics of ephemeral stream water (mg/L), collected in October 2006

Sample site T (°C) EC (μS/cm) pH HCO3− SO4

2− Cl− Ca2+ Mg2+ Na+ K+

Tapeh television 16.5 212 7.24 66 13.8 8.0 25 6.5 6.0 0.3Kayani 16 150 7.22 46.6 10 7.0 19 5.7 5.0 0.3Sherkat 17 126 7.2 39 8.2 6.0 13 5.0 4.5 0.2Gelal 16.3 331 6.8 103 21.6 11 31 7.5 9.6 0.4Paderazan 17.5 700 7.32 95 350 8.0 183 41 34 1.5

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suspended sediment load may not greatly reduce thepermeability of the reservoir or shorten the viability of therecharge site.

Artificial recharge methodsBased on the collected data, two types of artificialrecharge method—recharge basin and check dam—weresuggested to catch and infiltrate flash flood waters fromthe ephemeral streams (Fig. 2). A check dam is a waterharvesting structure built across the direction of water flowon small rivers or streams with the aim of water mitigation.Check dams hold back left-over water flow during the rainyseason in a reservoir behind the barrier and the major benefitis recharge of the adjoining aquifer. The site selection for thedam is very important and, in order to be cost effective,many components of the system have to be taken intoaccount. The main parameters include: infrastructuredesign, permeability of stream bed, slope of water course,narrowness of stream, steep sided slope, availability of

construction materials, watershed lithology and storagecapacity of the barrier.

For calculation of storage capacity at the Tapehtelevision check dam, a contour map of the catchmentwas prepared and by considering height of the dam(4.5 m), back water length was determined (60 m). Then,by measuring the area of each contour level in the water-filled area, maximum storage capacity (surface water) wascomputed. Back water length was estimated in this way,although the use of more sophisticated surveying instru-ments is preferred.

Based on the dimension of the ponds and maximumwater line the storage capacity of the recharge basins wasestimated. It was proposed that the check dam at theTapeh television site should have a storage capacity ofapproximately 160,800 m3. The dimensions of themasonry trapezoidal check dam constructed at this sitewere 60×35×4.5 m (length, width and height). Based oncost effectiveness, volume of runoff event, high infiltrationrate of the area; and, simply conducting excess flood waterinto Gelal stream, on the eastern side of the Kayani

Fig. 7 Piper diagram of surface water samples and a representation of the maximum, minimum and mean concentrations of all 22groundwater samples

Table 6 Physico–chemical characteristics of all 22 groundwater samples (mg/L), taken in May 2006

Parameter T (°C) EC (μS/cm) μmhos/cm pH HCO3− SO4

2− Cl− Ca2+ Mg2+ Na+ K+

Maximum 24 1,454 7.9 335 725 29 256 53 16 2.7Minimum 20 388 7.7 113 26 14 33 21 7.0 0.8Mean 22 576 7.8 192 123 19 68 31 10 1.4Standard deviation - 298 0.07 31 200 3.4 64 11 2.5 9.5

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ephemeral stream, three recharge basins of 350×100×2.5 m each were suggested.

Two recharge basins of 250×150×2.5 m each weresuggested for the Sherkat stream. At the Kayani site, thenumber of recharge basins was selected on the basis ofusual annual rainfall discharge of the stream. The averagedepth of water in these basins and backwaters in the checkdam are respectively 2.5 and 3.35 m. As a result of theSherkat site proximity to Loran village, two large capacityrecharge basins were considered to alleviate the risk offlooding.

Hydraulic loadingThe required time to discharge the total volume ofimpounded water at the recharge sites was estimated usingthe following relationship:

T ¼ V=A� R ð4Þ

where T = discharge time in days; V = total volume of waterin the recharge basins and backwater in the check dam inm3;A = area of the reservoir in m2 and R = infiltration rate in m/day. It was assumed that the induced infiltration rate (R)would be 70% of the basic infiltration rate, and there isgeneral agreement that, even after the first intake, otherparameters would be affected. Thus, based on previousexperiences (Kalantari and Rahmani 1999; Kalantari andRangzan 2000), and on a conservative estimate, an inducedrecharge rate of 70% of the basic infiltration rate was used totake account of the reduction in infiltration and the hydraulicconductivity variation. Table 8 summarizes the results ofthese calculations.

EvaporationAn analysis of evaporation records from the evaporim-eter (US A class) installed at the Baghmalek meteoro-logical station indicated that the average rate ofevaporation was about 1.49 mm/day from Decemberto March; the monthly evaporation at the Baghmalekmeteorological station from 1985 to 2005 is given inTable 9. Therefore, on the basis of discharge time, thevolume of backwater impoundment of the check damand recharge basins and, using an evaporimeter coef-ficient of 0.7, the evaporation losses were estimated(Table 10).

Recharge estimationThe estimation of recharge rate from the surface reservoirs(recharge basins and check dam) to the unconfined aquiferwas carried out in the following steps:

1. The capacities of the sites were assumed equal to theirdesign capacities (sites 1 to 3 have design capacities,respectively, of 1.7×105, 2.1×105 and 1.5×105 m3).

2. Rainfall records were examined to determine frequencyof high intensity rainfall which would produce signifi-cant runoff events (it was found that this occurs five tosix times a year: five flood events were assumed tooccur each year).

3. It was assumed that in the first intake of the reservoirs1×105, 1.3×105 and 1.1×105 m3, respectively, areneeded to saturate the unsaturated zone below therecharge sites. By considering depth to water table,porosity, specific yield, the base of the infrastructures(m2), and assuming 5% soil moisture, the amount ofwater needed to meet saturation of the aerated zone wascalculated.

4. The volume of water percolating downwards from therecharge infrastructures was calculated as the differencebetween the reservoir capacity (step 1) and thecomputed evaporation rate (see section Evaporationand Table 10).

Table 7 Representative saturation indices of the ephemeral streams and groundwater samples

Saturation index Sample numberGW1 GW2 GW3 GW4 GW5 GW6 SW1 SW2 SW3

SIc 0.21 0.08 0.68 0.41 0.18 0.08 −1.04 −1.32 −1.56SId 0.50 0.15 1.48 0.82 0.66 −0.19 −2.44 −2.95 −3.30SIg −2.36 −2.00 −2.11 −2.40 −2.15 −0.51 −2.71 −2.95 −3.16

GW groundwater; SW surface water (ephemeral streams); SI saturation index for c (calcite), d (dolomite) and g (gypsum)

Fig. 8 Grain size analysis of suspended loads of the Tapehtelevision, Kayani and Sherkat tributaries

Table 8 Parameters used for calculation of discharge time

Site T (day) V (m3) A (m2) R (m/day)

Tapeh television (1) 5.6 8×104 2.4×104 5.9×10−2

Kayani (2) 3.8 7×104 3.5×104 5.2×10−2

Sherkat (3) 3.7 7.5×104 3.75×105 5.4×10−2

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5. Using the results from the number of significant runoffevents—(step 2) × (design capacity-evaporation (steps1 and 4)—volume of water needed to saturate theunsaturated zone below the recharge facility (step 3)—was calculated.

Using this approach, it was estimated that the totalannual recharge water flux into groundwater storage fromthe three sites is about 2.2 Mm3.

CostIn general, the main cost of recharge schemes dependsupon the degree of source water treatment and siltation,construction, land value, maintenance and the type ofrecharge scheme. In areas such as Baghmalek, due to theproximity of the source water close to the suggested sites,suitable chemical quality of water, relatively low sus-pended solids, extensive land availability, on-site rawmaterials for construction and the simplicity of therecharge ponds, establishment of the artificial rechargeschemes seems reasonable. The costs of infrastructure arechiefly associated with construction and a part would haveto be allocated for operation and maintenance. In the caseof basin recharge schemes, a large amount of the invest-ment is spent on soil removal and levee construction, andin the case of check dams, the capital cost is the small-dam construction. Any how, due to foregoing reasons, lowlabor salary and cheap fuel for machinery, the constructioncost is low. As a result of cooperation of the inhabitants,operation is not a serious problem, and 5% of the capitalcost is suggested for the scheme’s maintenance (Bakhtiaret al. 1997). The capital costs, in 2007-terms, for the Tapetelevision check dam and the Kayani and Sherkat rechargebasins would be, respectively, $US 81,764, $US 84,588and $US 55,882, a total of $ US 222,234. In order to haveknowledge about the cost of artificial recharge schemes inthe area, the initial estimated construction cost of theSherkat artificial recharge scheme, which consists of twobasins (each with 250 m length, 150 m width, 3 m heightand a total volume of 1.5×105 m3 to store runoff water) isgiven in brief in Table 11.

It is apparent from Table 11 that, based on previousexplanations, the initial construction cost of surface waterinfrastructure in such areas is not expensive and, in suchcases, the initial cost mainly involves excavation, soilremoval and embankment. The total estimated cost ofinfrastructure construction including basins and the checkdam is $ 222,234 and the cost of 1 m3 of infiltrated waterin the first year of operation is approximately $ 0.12.

Cost-benefit analysisIn general, the most economic artificial recharge schemesare those in regions where water level declines areassociated with agriculture (Shahbaz et al. 2008). In theBaghmalek agricultural area, the results of the presentstudy suggest that an artificial recharge project couldreverse groundwater decline and thereby make more landavailable for irrigated farming, thus substantially raisingfarmers’ income. Thus, in addition to other benefits suchas reduction in groundwater decline and flood watermitigation, the most important benefit of the suggestedartificial recharge projects in Baghmalek is agriculturalproduction. Implementation of these schemes couldincrease groundwater storage, enhance the total area undercultivation and change the area of rain fed farming intoirrigation farming. Generally, wheat, oats, cucumber,onion, rice, corn and tomato are cultivated in the studyarea, but due to the rise of price in the last few years,much of the cropped area in the Baghmalek plain has beenconverted to rice cultivation. This crop is by far the mostintensive in terms of use of groundwater and in fact ismainly responsible for the lowering of the groundwaterlevel. The cost-benefit analysis (Table 12) undertaken aspart of the present investigation and summarized below is

Table 9 The monthly evaporation at the Baghmalek meteorological station (mm)

Statistic parameters Month AnnualJan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Minimum 30.5 34.5 36.9 48.9 51.9 83.2 133.6 123.3 122.4 68.7 48.2 26.3 685.1Maximum 49.4 59.1 73.5 137.2 165.2 232.2 238 254.5 235 14.9 97.7 66.7 1,757.5Average 39.9 46.8 55.2 93.1 108.5 157.7 185.8 188.9 178.7 108.8 72.9 46.5 1,282.8

Table 10 Evaporation and discharge rates at the recharge sites

Site Evaporation (m3) Recharge volume (m3)

Tapeh television (1) 0.1×105 0.7×106

Kayani (2) 0.3×104 0.9×106

Sherkat (3) 0.2×104 0.6×106

Table 11 Construction cost of the Sherkat suggested site

Item Cost ($US)

Design 1,500Excavation and soil removal 21,500Embankment and compaction 11,000Water diversion barrier 3,500Minor concrete structure 2,600Embankment riprap 2,500Labor fee 2,550Miscellaneous 1,800Workshop cost 3,621Regional coefficient costa 5,311Total 55,882

a For execution in remote areas

770


based on the increase in rice production as a result ofimplementation of artificial recharge.

In this investigation, all elements including rechargerate, recoverable water and irrigation return flow havebeen computed. On average, the annual groundwaterrecharge by the projects is estimated to be 2.2 Mm3 andit is expected that 1.87 Mm3 is recoverable for agriculturalactivities. An important point is that not all of the waterfrom a project can be recovered; some is kept in storageand some moves away. For instance, building up theartificial groundwater mound in the Baghmalek aquifercan increase the rate of groundwater movement away fromthe recharge area due to an increase in hydraulic head. Inthe study area, movement can discharge injected waterinto nearby Gelal ephemeral stream (Fig. 1). The differ-ence between recharge and recovery was taken intoaccount as underground flow due to the groundwatermound (5.3 m) and was computed utilizing Darcy’s lawand a cross sectional area of aquifer in the vicinity of theTape television and Kayani schemes. Therefore, therecoverable water (1.87 Mm3) is taken into account andthis is sufficient to bring 0.53 km 2 (53 ha) more of bareland into rice cultivation. As a result of favorablepermeability and low depth to groundwater, on averageabout 0.36 Mm3 will be returned as irrigation rechargewater annually (Rahimi and Kalantari 2008). The returnrecharge may help to balance the probable decrease ininfiltration capacity of the infrastructures as a result ofsedimentation. The study also indicates that the artificialrecharge schemes would have a lifetime of about threedecades assuming good maintenance of the recharge sites.Based on this conclusion, an attempt has been made toevaluate the approximate efficiency of the suggestedBaghmalek recharge sites.

The annual water demand per hectare (0.01 km2) forgrowing rice is approximately 35,407 m3 (Protection andexploitation of Khuzestan province water resources, 2002,unpublished data). The output of each hectare of landunder cash crop rice cultivation is approximately 4.5 tons(Director General of Khuzestan Province AgricultureDepartment, personal communication, 2007; Zali 1985;Anonymous 2005) and the rice price (Anbarboo variety)per ton was $ US 1,000, in the year 2007. Therefore, riceprovides, in total, an annual income close to $ US237,665; this figure is expected to grow annually by10% due to increase in price. Expansion of irrigationfarming would result in an increase in pumping and othermiscellaneous costs. These costs have been estimated tobe 40% of the total annual gain from the schemes. Thisestimation is based on data collected in the field from anumber of well owners and by applying the return on aninvestment equation (Buchanan and Cross 2005).

According to the data for 2007 from the Planning andFinance Organization of Iran, the fixed costs, includingdesign and construction of the hydraulic structures,management and other miscellaneous costs for the Tapehtelevision check dam and the Kayani and Sherkat basins,would be respectively $US 81,764, $ US 84,588 and $ US55,882, yielding a total of $ US 222,234. It is alsoassumed that 5% of the capital cost with an annualdiscount rate of 10%, would be needed for maintenanceand protection of the infrastructures (Kowsar 1991;Bakhtiar et al. 1997; Ballukraya and Sakthivadivel2002). In the present investigation, a cost-benefit analysis,based on the increase in rice production as a result ofusing artificial recharge schemes, was undertaken. Giventhese assumptions and using the cost-benefit analysis(Table 12), it is calculated that the three schemes could

Table 12 The income and cost with their present values at 10% discount rate, $ US

Year Fixedcosts

Variablecost

Totalcost

Cost,present value

Cumulativecost, presentvalue

Income Income,present value

Cumulativeincome,present value

Benefit/cost

0 222,234 0 222,234 222,234 222,234 0 0 0 01 - 116,795 116,795 106,178 328,412 261,431 237,665 237,665 0.722 - 128,475 128,475 106,178 434,589 287,574 237,665 475,330 1.093 - 141,322 141,322 106,178 540,767 316,332 237,665 712,995 1.324 - 155,455 155,455 106,178 646,945 347,965 237,665 950,659 1.475 - 171,000 171,000 106,178 753,122 382,762 237,665 1,188,324 1.586 - 188,100 188,100 106,178 859,300 421,038 237,665 1,425,989 1.667 - 206,910 206,910 106,178 965,478 463,142 237,665 1,663,654 1.728 - 227,601 227,601 106,178 1,071,655 509,456 237,665 1,901,319 1.779 - 250,361 250,361 106,178 1,177,833 560,401 237,665 2,138,984 1.8210 - 275,397 275,397 106,178 1,284,010 616,441 237,665 2,376,649 1.8511 - 302,937 302,937 106,178 1,390,188 678,086 237,665 2,614,314 1.8812 - 333,231 333,231 106,178 1,496,366 745,894 237,665 2,851,978 1.9113 - 366,554 366,554 106,178 1,602,543 820,484 237,665 3,089,643 1.9314 - 403,209 403,209 106,178 170,8721 902,532 237,665 3,327,308 1.9515 - 443,530 443,530 106,178 1,814,899 992,785 237,665 3,564,973 1.9616 - 487,883 487,883 106,178 1,921,076 1,092,064 237,665 3,802,638 1.9817 - 536,672 536,672 106,178 2,027,254 1,201,270 237,665 4,040,303 1.9918 - 590,339 590,339 106,178 2,133,432 1,321,397 237,665 4,277,968 2.0119 - 649,373 649,373 106,178 2,239,609 1,453,537 237,665 4,515,633 2.0220 - 714,310 714,310 106,178 2,345,787 1,598,890 237,665 4,753,297 2.03

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recoup the investment within 3 years and the cost–benefitratio is 1:1.32

Conclusions

The water supply for different purposes in the Baghmalekplain depends solely on groundwater and annual ground-water extraction from the aquifer is approximately15 Mm3. As a result of heavy withdrawal of groundwaterin the area, there is a gradual decrease in water level.

The Baghmalek Mountain front, and in particular DerbMountain, makes available a very suitable site for artificialrecharge due to high infiltration capacities of the coarsealluvial deposits. Based on surface and subsurface inves-tigation, recharge sites were selected and basin and checkdam schemes were suggested. The average infiltration rateof the suggested sites was 133 mm/h. The low EC andtotal dissolved solids of the ephemeral-stream samplesindicate that in most parts of the study, area waterresources are quite good.

The total annual runoff available for recharge is3.8×106 m3 and it is estimated that about 2.2 Mm3

could be injected into the aquifer with 1.87 Mm3 beingrecoverable. The low weight of runoff suspendedmaterial and the low ratio of clay particles make thesites favorable for recharge. The total estimated cost ofinfrastructure construction including basins and checkdams is $ 222,234 and the cost of 1 m3 infiltrated waterin the first year of operation is approximately $ 0.12.The cost–benefit ratio, based soley on the predictedincrease in agricultural production, is estimated at1:1.32, with a payback period of about 3 years. Apartfrom groundwater augmentation, impeding groundwaterlevel fall, and the substantial contributions to farmers’incomes, the effects of destructive floods can bemitigated, which is another side benefit.

Acknowledgements The authors would like to thank ShahidChamran University and the Water and Power Organization ofKhuzestan Province for providing facilities and financial support toconduct this study. The assistance of Professor J. Tellam, of theUniversity of Birmingham, UK for editing the English text issincerely acknowledged. Thanks are also due to anonymousreviewers and the Technical Editorial Advisor Mrs. Duncan fortheir constructive suggestions.

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