newsletter of isotope hydrology section issue no. 21 ...isotope hydrology has been ... use of both...

In this Issue

Photo Credit: K.M. Kulkarni / IAEA

From the Section Head . . . . .

As this issue of the newsletter is being published, the 50th GeneralConference of the IAEA is meeting in Vienna. Isotope Hydrology has beena part of the IAEA’s activities almost from the beginning of the IAEA fiftyyears ago. After making substantial contributions to the scientific field, theisotope hydrology portion of the IAEA’s work acquired the status of aprogramme and was renamed the programme on water resources. Thisreflected both the importance of water in sustainable development and thewider role of the IAEA in enabling countries to develop their human andinstitutional capacity for using isotope techniques. Since then, theprogramme of work in water resources has focused to a large part onidentifying and removing obstacles to a wider use of isotopes in waterresources management. Let me highlight a few of these items here.

Strengthening the network of isotopes in precipitation, Global Network ofIsotopes in Precipitation (GNIP), has been a challenge for more than twodecades. This challenge arises from two basic issues: the effort needed to

Newsletter of Isotope Hydrology SectionIssue No. 21, September 2006

From the Section Head . . . . . . . . . 1

News in Brief. . . . . . . . . . . . . . . . . . 3

SGD: An Emerging Coastal Issue. . . . . . . . . . . . . . . . . .6

Managing Aquifer Recharge. . . . . . .10

Managing Aquifer Rechargein the Middle East . . . . . .. . . . . . . . 11

IAEA/RCAExecutive Meeting onGroundwater Contamination . . . . . .13

Meetings in 2006. . . . . . . . . . . . . . .14

Isotope Hydrology Staff . . . . . . . . . .15

Announcement . . . . . . . . . . . . . . . 16

Water & Environment News No. 21, September 2006

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collect precipitation samples and the use of isotopedata in hydrological and climate studies. Increasingly,data collection for hydrology and meteorology ismigrating to automated and/or satellite basedobservation networks. Isotope data networks,however, require the availability of someinfrastructure and human resource to collect physicalsamples. This creates substantial difficulties inbuilding a network that can operate over a long term.

We have taken a number of steps, including theprovision of small grants, to facilitate the collectionand shipping of precipitation samples to Vienna foranalysis. Recently, we began a collaborative activitywith Dr. Tyler Coplen of the US Geological Survey tomodify his design of an automated sample collector.This sample collector may be used to gather up to 96precipitation samples at preset intervals. Whenavailable, this modified collector can ease the burdenand reduce human resource requirements forobtaining precipitation samples from remote areas aswell as areas where an interested community ofscientists may not be available. In addition, it wouldallow easier collaboration with other scientificprogrammes which presently may not include isotopeinvestigations in their work.

The GNIP Scientific Steering Committee has been re-constituted and presently includes Jim Ehleringerfrom the University of Utah, USA, John Roads fromthe Scripps Institution of Oceanography, La Jolla,California, USA, Tetsuo Ohata from the JapanAgency for Marine-Earth Science and Technology,Japan, and representatives of World MeteorologicalOrganization (Wolfgang Grabs), and Past GlobalChanges (PAGES) (currently Georg Hoffman,Laboratoire des Sciences du Climat etl´Environnement, Saclay, in France). Interactionshave also been strengthened with institutionsoperating GNIP stations and an attempt is being madeto bring many of the station operators together on anannual basis to discuss the state of the network and itsuse.

The operation and management of GNIP is alsoimpacted by the degree of use of the data forhydrology and/or climate studies for a lack ofavailability or use of data decreases the motivation ofthose who may have to invest some resources tooperate a GNIP station. Over the years, we havefacilitated the dissemination of GNIP data through theinternet.

In addition to precipitation data, we have compiledisotope data from aquifers and rivers worldwide.These data are also being used to build thematic mapsof fossil water aimed at assisting decision-makers andwater authorities in adopting better practices forgroundwater management. The database software hasbeen considerably improved to make it user-friendly.We will soon release a GIS tool, developed incooperation with the Institute of Geography at theUniversity of Vienna, that would allow statistical dataprocessing and plotting of data on to graphics andmaps. A hard copy of all isotope data compiled fromthe Africa region would soon be published by theIAEA as an “Atlas” to provide easy reference toprevious studies and foster greater use of the data infuture research.

The ability to analyse water samples for isotope ratiosis another obstacle in the wider use of isotopes inhydrology. The development of a dual-inlet gas-source massspectrometer in the 1950s heralded anexplosive growth in the use of isotopes in hydrologyand geology. New technological developments forisotope analysis of hydrological samples hold a greatpromise for revolutionizing the use of isotopes inwater resources management. With extra-budgetaryfunding from the US Government, we are presentlytesting and adapting a laser isotope analysis machine.This relatively inexpensive, low-skill and low-costinstrument, compared to the dual-inlet mass-spectrometer, could be operated at a minimal cost byresearchers and practitioners alike including non-isotope hydrologists, and would overcome the presentbarrier a wider use of isotopes in hydrology posed bya lack of easy availability of isotope analysis.

As a means to increase the integration of isotopes inhydrological investigations, we are building apartnership with other organizations, in particular theGlobal Environment Facility (GEF) to formulate andexecute comprehensive groundwater managementprojects. These projects will address scientific andpolicy issues and demonstrate the use and value ofinformation obtained from isotope techniques. First ofthese projects being implemented is in northern Africawhere we are assisting Egypt, Libyan ArabJamahiriya, Sudan and Chad to manage the shared,Nubian Aquifer. Other projects being formulatedinclude a characterization of groundwater-surfacewater interactions in the Nile River Basin and anassessment of national groundwater resources inEthiopia.

No. 21, September 2006 Water & Environment News

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Water resources management continues to be high onthe international agenda. The UN has proclaimed2005–2015 as the UN Decade for Action “Water forLife”, recognizing the growing awareness of thecritical linkage between water and development.Isotope Hydrology has an important role to play inhelping people manage their resources.

News in Brief

New staff members

Mr. Kamel Zouari joined the Isotope HydrologySection in May 2006. He was a former Professor atthe Engineering School of the University of Sfax inTunisia. His interests include the use of environmentalisotope techniques for the assessment of groundwaterresources of regional scale basins. He has coordinatedseveral bilateral and regional projects related to waterresources in arid regions funded by the InternationalAtomic Energy Agency, the European Commissionand UNEP. In the Section, Mr. Zouari will work onsustainable water resources management usingisotope and hydrochemical techniques, mostly inAfrican countries.

Ms. Mari Ito joined the Section in June 2006 afterworking on data management related to climatechange in the Climate Change Secretariat. Sheobtained a PhD in biogeochemistry with hydrologyand GIS. She previously worked on the developmentand implementation of several environmental anddevelopment projects in eastern Europe, SoutheastAsia, Africa, and Mexico in the UN and bilateralorganizations. She is interested in the interactionbetween water quantity and quality, environmentalsettings, and climate change, together with theapplication of GIS and the organization of data. Ms.Ito hopes to contribute to sustainable development,especially in developing countries and the countries ineconomic and social transition, through projects andother activities.

Departing staff members

Mr. Andrew Herczeg left the Isotope HydrologySection in August 2006 to return to his position atCSIRO Land and Water laboratories in Adelaide,Australia. During his 1 1/2 years at the Section, heassisted with development of a number of projectssuch as hydrological processes in wetlands, globalnetwork for monitoring isotopes in rivers, estimatingdeep drainage in irrigation areas, training and capacitybuilding and large aquifer projects such as the NubianSandstone Aquifer System. In addition, he managed anumber of TC groundwater projects in the arid zone ofAfrica and the Middle East. He was also involved inplanning and organizing the 2007 Isotope HydrologySymposium.

Mr. Seifu Kebede left the Isotope Hydrology Sectionin July 2006 to return to the Department of EarthSciences, Addis Ababa University, Ethiopia. Mr.Kebede was involved in compiling isotope, chemicaland hydrological data on African meteoric watersunder the ISOHIS programme as a Junior ProfessionalOfficer.

Meetings

The International Workshop on the Isotope Effects inEvaporation “Revisiting the Craig-Gordon ModelFour Decades after its Formulation” was held in Pisa,Italy during 3–6 May 2006. Mr. Pradeep Aggarwalwith 3 staff members from the Section participated in

In this issue of the Newsletter, a number ofcontributions discuss the application of isotopes incoastal zones, managing aquifer recharge,groundwater contamination, etc.

I hope you find this issue of newsletter useful andinformative.

Pradeep Aggarwal


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the workshop. The aim of the Workshop was to re-examine the Craig-Gordon evaporation model andreview current knowledge on the isotope fractionationduring phase changes of water in naturalenvironments and laboratory experiments. Twoscientific papers prepared by staff members werepresented in this workshop.

A consultants meeting (CM) to “DevelopGeochemical and Isotope Techniques to Evaluate theWater Flux Below the Root Zone in IrrigationSystems” was held at IAEA, Vienna (12–15 June2006). The diminishing capacity to divert and fullyutilize new water supplies is placing greaterconstraints on the ability of irrigated agriculture tofurther contribute to world food production. Whilethere have been significant advances and innovationin irrigation methods for better yields and crop watermanagement avoiding non-productive losses of watersuch as leakage from transfer systems, evaporationduring application and deep drainage below the rootzone have been less well studied. Deep percolation(recharge) resulting from irrigation have seriousimplications for sustaining groundwater irrigation,food security, drinking water supplies, andgroundwater dependent ecosystems. While drainageplays an important role in preventing buildup of saltswithin the plant rooting zone, there can be adverseconsequences manifested by water logging due toincrease in water tables, salinisation, or nutrient andpesticide discharge to waterways and wetlands.Nuclear techniques are useful in quantifying deepdrainage on plot to regional scale as well as inevaluation of off-site impacts.

Isotopes and geochemical techniques providepotential for improved quantification of deep drainageover time and spatial scales not afforded byconventional water balance or lysimeter studies. Theuse of both environmental tracers and applied tracers,while having been widely used in catchment scalestudies, have not been adopted as widely inagricultural systems on a large scale.

The consultants meeting has identified a specific setof methodologies that can be tested through acoordinated research project (CRP) on a plot tocatchment to regional scale. The meeting report hasrecommended a set of sites as a way of up-scaling theinformation to determine regional water balances.Incorporating the isotopic information with discharge

data and water quality also form an essential part ofthe proposed project design.

From 29 May to 9 June 2006 a formulation meetingfor a new IAEA/UNDP/ GEF Medium-Sized Project“Adding the Groundwater Dimension to Nile RiverBasin Management” was held at the IAEAheadquarters in Vienna. The objectives of the meetingwere to: i) Review the relevance and need forassessing the groundwater-surface water inter-linkages in the Nile River Basin as well as to discussthe results of the on-going IAEA technicalcooperation project (RAF/8/037) that is investigatinggroundwater linkages with Lake Victoria and parts ofthe lower Nile; ii) Gain agreement amongst projectpartners about the objectives, expected outputs &outcomes, activities and needed inputs for the newinitiative; and iii) Prepare a joint IAEA/UNDP/ GEFinitiative for adding the groundwater dimension to theNile River Basin management activities. Participantsfrom 6 countries and representatives from relevantprojects under the Nile Basin Initiative frameworkjoined the IAEA staff and associated experts todevelop this initiative. The proposal has beensubmitted to UNDP/GEF for review and approval.

The “Nubian Technical Baseline Meeting” was heldduring 8–12 May 2006 in Vienna with theparticipation of Nubian countries, IAEA staff andexperts. The objectives of the meeting were to: i)Review and synthesize currently available technicalinformation, with a focus on isotopic data, as a basisfor updating the “baseline” knowledge of the NubianSandstone Aquifer System (NSAS); ii) Determineinformation gaps that need to be filled in order to gainbetter understanding of the system and to assesstransboundary issues; iii) Consider strategies(sampling, monitoring, etc.) that could effectively andefficiently lead towards filling these gaps; iv) Developconcrete steps for filling these gaps in the frame of theIAEA’s co-funded activities for isotopic analysis inthe IAEA/UNDP/GEF Nubian Aquifer Project and inparticular to support the development of a report on“Shared Aquifer Diagnostic Analysis (SADA)”.

The IAEA’s Water Resources Programme co-sponsored the “European Groundwater Conference”that was held during 22–23 June 2006. TheConference was organized by the Austrian


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Environment Agency on behalf of the AustrianGovernment in its tenure of the EU Presidency. TheConference brought together an international groupof over 300 groundwater specialists, policymakersand managers to focus on policy and scientific aspectsof the overall EU groundwater legislative frameworkconcerning groundwater quality and implementationof the groundwater elements of the EU WaterFramework Directive. The key topic at the conferencewas the new EU Daughter Directive on GroundwaterProtection and Management. In addition to co-sponsoring the conference, the IAEA’s WaterResources Programme (WRP) provided a plenarypresentation on the “Use of Isotopic Techniques forGroundwater Assessment and Management” and abooth that highlighted IAEA achievements in thefield.

The 3rd International Symposium on TransboundaryWater Management was held in Ciudad Real, Spainfrom 30 May to 2 June 2006. The meeting was hostedby the University of Castilla-La Mancha incooperation with a number of national andinternational organizations and institutes, such as theUNESCO, Spain´s Ministry of the Environment,Sustainability of semi-Arid Hydrology and RiparianAreas (SAHRA), and the IAEA´s Water ResourcesProgramme. More than 120 participants with a broadfield of expertise reviewed the current status andrecent developments on a number of topics dealingwith management of surface waters and groundwatersshared by two or more territorial entities. Technicalsessions comprised characterization of hydrologicalsystems, recent advances on modelling, possibleimpact of global change in water availability andquality, legal issues such as the water law or theimplications of the European Water FrameworkDirective, resolving historical conflicts on water,public participation in decision-making, sharinghydrological information, analysis of the economicalimplications of shared management, etc., Theprogramme consisted of a number of plenary sessions,three parallel technical sessions as well as a postersession. With the assistance of the IAEA´s WRP, apre-symposium workshop on “Applications ofIsotopic Techniques for Transboundary AquiferManagement” was held during 29–30 May 2006. Thevalue and role of isotopes to assess groundwatersystems were emphasized in the workshop.Contribution of the IAEA, over the last four decades,in the field of Isotope Hydrology was highlighted.

Forthcoming

GNIP-Scientific Steering Committee Meeting

The fifth meeting of the Scientific SteeringCommittee of the GNIP (Global Network of Isotopesin Precipitation) will be held at the IAEAHeadquarters, Vienna in November 2006. Thismeeting is designed to provide advice to the IAEAand the WMO on strengthening of the operationalaspects related to the GNIP as well as on the relatedglobal monitoring activities, such as GNIR (GlobalNetwork of Isotopes in Rivers) and MIBA (MoistureIsotopes in the Biosphere and the Atmosphere).Review of the current status and recent developmentsof the programme on isotope monitoring ofprecipitation will be undertaken during the meeting.Also advice on activities to establish or reactivate theGNIP stations, will be sought.

A consultants meeting also related to the GNIP will beheld in November 2006 at the IAEA Headquarters,Vienna. The meeting deals with the establishment ofnational networks for monitoring isotope contents inprecipitation. The main objective of the meeting willbe to provide basic information on the GNIP andrelevant operational aspects to national teams leadingto establishment/reactivation of national networkswithin the GNIP.

Editor’s Note

To receive a free copy of Water & Environment Newsregularly, please write to:

Isotope Hydrology SectionInternational Atomic Energy Agency, Wagramer Strasse 5, P.O. Box 100 A-1400, Vienna, Austria

Email: [email protected].: +43-1-2600-21736Fax: +43-1-2600-7

Alternatively it is also available on the websitehttp://www.iaea.org/water

Contributions to the newsletter are welcome.


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The direct flow of groundwater into the ocean and the recycling of seawater through coastal aquifers are processes thathave been largely ignored in estimating material fluxes from the land to the sea. Submarine groundwater discharge

(SGD) is becoming recognized as an important process along many coasts that leads to fluxes of nutrients and carbon that may exceed riverine inputs.

Submarine Groundwater Discharge: An Emerging Coastal Issue

By Willard S. Moore, University of South Carolina, USA

The most evident interface between terrestrial andocean waters is the river mouth or estuary. Lessobvious is the subterranean interface betweenterrestrial groundwater and ocean water. The directflow of groundwater into the ocean and the recyclingof sea water through coastal aquifers are processesthat have been largely ignored in estimating materialfluxes from the land to the sea.

Submarine groundwater discharge (SGD) includesany and all flow of water on continental margins fromthe seabed to the coastal ocean, regardless of fluidcomposition or driving force. SGD is becomingrecognized as an important process along many coastsleading to fluxes of nutrients and carbon that mayexceed riverine inputs. There are two issues that mustbe considered: (1) What is the flux of freshwater dueto SGD? (2) What are the material fluxes due tochemical reactions of sea water and meteoric waterwith the aquifer matrix? Hydrologists are primarilyconcerned with the first question as it relates directlyto the freshwater reserve in coastal aquifers andsalinization of these aquifers. Oceanographers are alsointerested in this question because there may bebuoyancy effects on the coastal ocean associated withsubterranean input of fresh water. Chemical,biological, and geological oceanographers are moreconcerned with the second question as it relatesdirectly to alteration of coastal aquifers and nutrient,metal, and carbon inputs to the ocean (and in somecases removal from the ocean).

As freshwater flows through an aquifer driven by aninland hydraulic head, it can entrain seawaterdiffusing and dispersing upward from the salty aquiferthat underlies it. (Figure 1). Superimposed upon thisterrestrially-driven circulation are a variety of marine-induced forces that result in flow into and out of theseabed even in the absence of a hydraulic head. Toemphasize the importance of mixing and chemicalreaction in coastal aquifers, these systems have beencalled “subterranean estuaries” because they arecharacterized by biogeochemical reactions thatinfluence the transfer of nutrients, metals, and carbonto the coastal zone in a manner similar to that ofsurface estuaries. Several studies estimate that onsome coastlines the flux of nutrients into salt marshesand the coastal ocean through subterranean estuariesrivals the nutrient flux to the coast by rivers or theatmosphere.

The natural supply of nutrients and carbon by SGDmay be necessary to sustain biological productivity insome environments. There is also awareness that insome cases, SGD may be involved in harmful algalblooms and other negative effects. As coastaldevelopment continues, changes in the flux andcomposition of SGD are expected to occur. Toevaluate the effects of SGD on coastal waters, it isnecessary to know the current flux of SGD and itscomposition.

Attempts to quantify SGD have focused on threeapproaches: (1) using seepage meters to directlymeasure discharge; (2) using tracer techniques tointegrate SGD signals on a regional scale; and (3)groundwater modeling. Seepage meters (Figure 2), areconstructed from the top of a steel drum driven intothe sediment. In the simplest application a small

plastic bag collects the SGD. More advanced seepagemeters are based on heat pulse and acoustic Dopplertechnologies or dye dilution. Tracer techniques(Figure 3) utilize chemicals (often naturally occurringradionuclides) that have high concentrations ingroundwater relative to coastal waters and low

Figure 1. The interface between meteoric and seawater.


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reactivity in the coastal ocean. These techniquesrequire an assessment of the tracer concentration inthe groundwater, evaluation of other sources of thetracer, and a measure of the residence time of thecoastal water. With this information, an inventory ofthe tracer in coastal waters is converted to an offshoreflux of the tracer. This tracer flux must be replaced bynew inputs of the tracer from SGD. There have beenseveral attempts to reconcile groundwater flowmodels with tracer-derived and seepage meterestimates of SGD; these attempts have generallyfailed.

An initiative on SGD characterization was developedby the International Atomic Energy Agency (IAEA)and UNESCO in 2000 as a 5-year plan to assessmethodologies and importance of SGD for coastalzone management. The IAEA component included 2technical meetings on the subject and a CoordinatedResearch Project (CRP) on “Nuclear and IsotopicTechniques for the Characterization of Submarine

Groundwater Discharge (SGD) in Coastal Zones”carried out jointly by IAEA’s Isotope HydrologySection in Vienna and the Marine EnvironmentLaboratory in Monaco, together with 9 laboratoriesfrom 8 countries. In addition to the IAEA, theIntergovernmental Oceanographic Commission (IOC)and the International Hydrological Programme (IHP)of the UNESCO have provided support. This overalleffort originally grew from a project sponsored by theScientific Committee on Ocean Research (SCOR)who established a Working Group (112) on SGD.

The overall objective of the IAEA CRP was toimprove the capability of the Member States for waterresources and environmental management of coastalareas. The specific research objectives were: i) Toidentify and integrate the application of isotopemethods with conventional methods appropriate fordetection, characterization, and quantification ofsubmarine groundwater discharge in coastal areas. ii)To explore application of recently developed nuclearand isotopic techniques suitable for quantitativeestimation of various components of SGD. iii) Todevelop a better understanding of the influence ofSGD on coastal oceanographic processes and ongroundwater regimes for better management ofgroundwater resources and environmental concerns incoastal areas.

This CRP brought together investigators from diversescientific backgrounds to assess SGD in differentgeological/hydrological regimes and to synthesize theresults into a comprehensive paper (Figure 4). Theactivities of the project included joint meetings

Figure 3. Strategy to determine the importance of exchange with coastal aquifers.1. Identify tracers derived from coastal aquifers that are not recycled in the coastal ocean. Map their distributionand evaluate other sources (rivers, sediments, atmosphere).2. Determine the exchange rate with the open ocean.3. Calculate the tracer flux to the ocean, hence the tracer flux from the aquifer. 4. Measure the average tracer concentration in the coastal aquifer to calculate fluid flux.5. Use the concentrations of other components (nutrients, carbon, metals) in the aquifer or their ratios to thetracer to estimate their fluxes.

Figure 2. Manual seepage meter.


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(Vienna 2000, 2002, and 2005; Syracuse, Sicily, 2001;and Monaco 2004), sampling expeditions (Australia2000; Sicily 2001 and 2002; New York 2002; Brazil2003; and Mauritius 2005), joint analytical work, dataevaluation, and preparation of joint publications. Acombination of geochemical, geophysical, andhydrological techniques and models revealedsubstantial SGD at each site. The CRP compareddifferent techniques and arrived at a consensusprotocol for future SGD studies. As a result of thisCRP as well as the SCOR, IHP, and IOC support, 43scientific papers have been published or are in press;an additional 12 have been submitted. We anticipatethat this list will continue to grow over the next fewyears. The products of this CRP will serve as standardreference materials in ongoing and future studies ofSGD.

The overall finding of the CRP agrees with otherstudies of SGD, namely that it is fairly ubiquitous inthe coastal zone. In unconfined aquifers SGD usuallyfollows a pattern of decreasing flux with distancefrom the shore. There are temporal patterns modulatedby waves and tides; not only the diurnal tidalvariations, but also the spring-neap lunar cycle.Superimposed on these predictable patterns are theeffects of storms and other events that may cause largeSGD fluxes in a short time. Semi-confined aquifersmay discharge many km offshore without a clearpattern. Detailed knowledge of subsurface geologywould be required to predict where such discharge isexpected. Regardless of location, however, bothspatial and temporal variations are to be expected.Preferential flow paths (sometimes revealed assubmarine springs) are commonly found not only inkarst environments, but also in settings that appearreasonably homogeneous and isotropic. Tidalvariations generally appear as higher SGD rates at lowtide levels (and lower rates at high tides). However,the modulation is not necessarily linear and the

relationships are not completely understood (Figure5). In some situations the rate of SGD seems to changeabruptly without an obvious cause. The compositionof SGD is often a mixture of fresh and salinegroundwater with recirculating seawater accountingfor 90% or more of the discharge in some locations orless than 10% in the case of some offshore springs.

While each study site must be approachedindividually, there are a few generalizations that canbe made. All the measurement techniques describedhere seem valid although they each have their ownadvantages and disadvantages. Therefore, multipleapproaches should be applied whenever possible. Inaddition, a continuing effort is required in order tocapture long-period tidal fluctuations, storm-inducedeffects, and seasonal variations. The choice oftechnique will depend, of course, not only on what isperceived to be the “best” approach, but by practicalconsiderations (cost, availability of equipment, etc.)as well. For many situations, where calm seas prevailand the coast is not affected by significant waves orstrong currents, seepage meters appear to work verywell. These meters provide a flux at a specific timeand location from a limited amount of seabed(generally ~0.25 m2). Seepage meters range in costfrom almost nothing for a simple bag-operated meterto several thousands of dollars for those equipped withmore sophisticated measurement devices. However,labour costs to install and maintain seepage metersover a large area for more than a few days aresubstantial. Seepage meters are subject to artefacts butcan provide useful information if one is aware of thepotential problems and if the devices are used in theproper manner. This seems to be especially true inenvironments where seepage flux rates are relativelyrapid (>5 cm/day).

Use of natural geochemical tracers, especially

Figure 4. SGD studies in progress at the Shelter Island, USA. (Photocourtesy W.C. Burnett)

Figure 5. Variation of 222Rn, seepage flux, and tide height. In generalseepage and 222Rn are highest at low tide, but the data are not relatedlinearly. Note the very high seepage for the second low tides on 19 and20 Nov., but not for the earlier low tides on these days. These early lowtides were not characterized by high 222Rn activities. WHOI in the figuremeans Woods Hole Oceanographic Institution. (Courtesy W.C . Burnett)


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isotopes, involves the use of costly equipment andrequires personnel with special training andexperience. One of the main advantages of the tracerapproach is the integration of the SGD signal throughthe water column so smaller-scale variations, whichmay be unimportant for larger-scale studies, aresmoothed out. The approach may thus be optimal inenvironments where especially large spatial variationis expected (e.g., fractured rock aquifers). In additionto the spatial integration, tracers integrate the waterflux over the time-scale of the isotope and the waterresidence time of the study area. Depending uponwhat one wants to know, this can often be a greatadvantage. Finally, different components of SGD canbe recognized and quantified using isotopic tracers.This allows discharge from surficial and semi-confined aquifers to be separated. In all casesconclusions based on isotopic tracers depend on thevalidity of the models and their assumptions used tointerpret the distributions. Mixing and atmosphericexchanges in the case of radon must be evaluated andcare must be exercised in defining the end-members.The use of multiple tracers is recommended whenpossible.

Simple water balance calculations have been shown tobe useful in some situations as an estimate of the freshgroundwater discharge. Hydrogeologic, dual-density,groundwater modelling can also be conducted assimple steady state (annual average flux) or non-steady state (requires real time boundary conditions)methods. Unfortunately, at present neither approachgenerally compares well with seepage meter andtracer measurements, often because of differences inscaling in both time and space. Particular problemscan be encountered in the proper scaling andparameterizing dispersion processes. Apparentinconsistencies between modelling and directmeasurement approaches often arise because differentcomponents of SGD (fresh and salt water) are beingevaluated or the models do not include transientterrestrial (e.g., recharge cycles) or marine processes(tidal pumping, wave set up, storms, etc.) that drivepart or all of the SGD. Geochemical tracers andseepage meters measure total flow, very often acombination of fresh groundwater and seawater.Water balance calculations and most models evaluatejust the fresh groundwater flow.

Although the techniques described here are well-developed, there is no “standard” methodology. Forexample in karstic or fractured bedrock environments,heterogeneity must be expected. In this case it would

be best to plan on multiple approaches. Rates arelikely to be controlled by the presence or absence ofburied fracture systems where flow is focused, ordispersed, by the topography of the buried rocksurface. In such situations, integrated SGD might beassessed with dispersed geochemical tracers ordescribed statistically from many, randomly situated,seepage measurements. In volcanic aquifers,especially young basalts, the radium signal may below. This was found to be the case in the Mauritiusstudy and in other studies in Hawaii. Such a situationmight hamper the application of Ra and Rn tracers inthese settings. In such an environment one should alsoconfirm the spatial heterogeneity with somepreliminary seepage meter deployments andgeophysical techniques; and use traditional modellingapproaches with caution as good results will likelyrequire more complex models and a significantamount of data.

In a coastal plain setting without an underlying semi-confined aquifer, it is likely that the results will bemore homogeneous. Seepage meters often work wellin such environments where conditions are calm.These can provide good estimates that can be checkedby looking for a distinctive pattern in the results. Sucha pattern might, for example, consist of a systematicdrop off in seepage rates as a function of distanceoffshore in unconfined aquifers. Simple modellingapproaches (e.g., hydraulic gradients, tidalpropagation, thermal gradients) can often be valuablein this type of environment. Tracers also will workvery well in coastal plain environments.

This emerging field will require the expertise andviewpoints of a wide variety of coastal scientists.Some will try to understand the movement of waterthrough anisotropic strata due to forcing by hydraulicgradients, tides, waves, storms, coastal freshwaterdemands, and changing sea level. Others willinvestigate chemical reactions among the variablecomposition fluids and aquifer solids and the changesthese reactions cause to both phases. The presenteffects of the discharge on the biology, chemistry,geology, and physics of the coastal ocean must beunderstood. Past effects of SGD, especially duringaltered sea level, must be considered as well. There islittle doubt that important coastal management issueswill derive from these studies.

For further information please contact K.M. Kulkarniat [email protected]


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Managing Aquifer Recharge : How Can Isotope Hydrology Help ?

By Jordan F. Clark, Dept. of Earth Sciences, University of California, Santa Barbara, USA

During the last 50 years, the increased demand forfreshwater has created shortages throughout theworld. The projected growth in population combinedwith a changing climate is likely to make the situationworse. New solutions are needed to meet future waterdemands. One of the emerging solutions is a processknown as managed aquifer recharge (MAR) thatinvolves diverting surplus runoff water or recycledwastewater into aquifers for storage and laterextraction. MAR is now practised for the combinedmanagement of groundwater and surface water inmany parts of the world.

While there are many potential benefits of MAR, oneneeds to be mindful of many potential side-effects thatmay arise when altering the natural water andchemical cycles within the subsurface. For example,understanding the movement and fate of injectedwater as well as changes to the water quality duringtransit through the soil and groundwater is needed.Contaminants from industry, agriculture, or municipalsources that are part of the source water supply mayaffect the ambient groundwater quality. Theintroduction of disinfection by-products, infectivemicro-organisms, and organic compounds withunknown health risks into groundwater supplies is asignificant concern. It is paramount to understand thefate and transport of potential contaminants nearMAR sites. Only from this understanding can robustand appropriate regulations be developed.

Stable isotopes of water and conservative ions areused as ‘fingerprints’ that can trace movement andfate of water. Also, dating with tritium and itsdaughter, 3He, and deliberate tracer experiments areused to estimate water residence time within thesubsurface. This knowledge is needed to establishedhydraulic connections and travel times between therecharge location and production wells. Thesetechniques are probably the most reliable and cost-effective methods for determining travel timesbetween recharge location and wells considering thecomplex hydrogeology and transport processes that

exist near most MAR operations. Because of thevariety of techniques and multiple manners in whicheach technique can be used, isotopes are well suitedfor site planning studies as well as for performanceevaluations of young and old MAR operations. Thesetechniques have been used and tested in the CoastalDunes of the Netherlands, the Orange County WaterDistrict, California, The Berlin Water Works,Germany, and the Bolivar ASR system, SouthAustralia.

The isotope techniques may be most useful inproviding critical parameters for examining in situwater quality changes. The application of stableisotopes of carbon, nitrogen, oxygen and possiblycompound specific isotopes can evaluate the rate andextent of biodegradation of contaminants and organicmatter and to evaluate in situ biogeochemicalreactions that change the quality of the rechargedwater within the subsurface. Many potentialcontaminants such as most infective micro-organismsare naturally removed or become inactive with time inthe subsurface.

While many of the well characterized MAR sites inthe world are in developed nations, there arenumerous sites in the developing world that haveequally long operation histories and are the source ofa large fraction of the potable water supply. Thesource water for most of these sites is either surplusrunoff or recycled wastewater. Examining the scale ofthe water quality impact as well as water balance iscrucial to the viability and long-term sustainability ofMAR in the water-stressed parts of the world.

For further infomation please contact P. Aggarwal at:[email protected].

One of the emerging solutions to ever increasing water demand is a practice known asmanaged aquifer recharged (MAR) that involves diverting runoff water or

recycled water into aquifers for storage and later extraction.


11

Isotopes and Geochemical Techniques in the Studyof Managed Aquifer Recharge in the Middle East

By Paul Pavelic, CSIRO Land & Water, Adelaide, Australia

Groundwater resources in many parts of the MiddleEast are under increased stress owing to increaseddemand for water from rapid population growth inrecent decades. As large volumes of water aregenerated seasonally in arid areas during episodicstorm events that drain into lowlands and aresubsequently lost to evapotranspiration, there ispotential to alleviate the stress on groundwater byimplementing water harvesting techniques.

Throughout the Middle East, surplus water fromstorms is stored in aquifers via basins or injectionwells and later drawn upon via extraction wells duringtimes of shortage. The earliest known practice ofenhancing groundwater through artificial rechargedates back several millennia in the Middle East.

Although simple in concept, successful andsustainable managed aquifer recharge (MAR) isdependent upon addressing numerous technicalissues. Of these, characterizing local hydrogeologicalconditions and the resulting distribution of recharged

water within the aquifer, the degree of mixingbetween recharge water and ambient groundwater,and residence times within the system arefundamental to the successful management of MARschemes. The scope of isotope applications in MARhas not been thoroughly evaluated, with few studies ofthis kind in arid or semi-arid climates, and fewer (ifany) within the Middle East.

TC Project RAS/8/103 will assist the Member Statesinvolved to better manage aquifer recharge sceheme,through the use of isotopic techniques supported byconventional geochemical tracers.

A diverse range of case studies have been selected forinvestigations that encompass hydrogeologicalenvironments ranging from unconsolidated sand tokarstic limestone, and water sources ranging frompristine snowmelt to treated sewage effluent (Table 1).There is an emphasis on surface spreading methodsthat target unconfined aquifers, although one siteutilizes injection wells to store water within a

Study Site MAR Type Hydrogeological Setting Monitoring locations Tracers

Siwaqa Dam,Jordan

Recharge dam fordrinking supplies(Cap=2.5X106 m3)

Upper creaceous limestone dam, observation wells and2 production wells

Major ions, 2H, 18O,3H

Rajil Dam,Jordan

Recharge dam for oasisrestoration(Cap=3.5X106 m3)

Basalt overlying limestone observation wellsunder construction

Major ions, 2H, 18O,3H

Wala Dam, JordanRecharge dam forirrigation and drinking (Cap=9.3X106 m3)

Upper Creataceouslimestone

dam, 3+ observation wellsand 2 production wells

Major ions, 2H, 18O,3H, 14C

Damascus Basin,Syria

7 (or more)injection sites Alluvial sands and gravels

recharge water,observation wells andproduction wells


Beryan Dam,Sana’a BasinYemen

Recharge dam (Cap=0.22X106 m3)

Alluvial sediments overlyingBasalt

climate, groundwaterlevels, recharge water andgroundwater quality


Beih Dam,UAE Recharge dam Fissured limestone observation wells Major ions, 2H, 18O,

3H

TawiyaenDam,UAE

Recharge dam fortertiary-treated sewageeffluent

Fissured limestone observation wells Major ions, 2H, 18O,3H

Table 1. Several of the MAR investigation sites selected for study.


12

confined aquifer (Figure 1). All case studies arereplenishing stressed aquifers that are used for urbanand/or agricultural water supply.

A short course and workshop was conducted inDamascus during February 2006 involving all theparticipating countries to share the broad range ofknowledge and experiences on MAR within theproject team. Assistance was provided with siteselection, development of monitoring programmesand analytical capabilities.

Preliminary results to date indicate that the applicationof isotope techniques have contributed to theunderstanding of the technical issues. The ultimateaims are to assess the feasibility of applying MARschemes at various sites, to determine the sitecharacteristics that best suit this purpose, and topromote the development of a regional capability forusing isotopes and geochemical techniques to aidfuture investigations. Already the project hassucceeded in enhancing collaboration amongstparticipating countries, and between the various

Figure 1. Injection well, Damascus Basin, Syria.

Figure 2. Participants in the Regional training course Damascus , Syria 5–16 February 2006.

institutions responsible for water supply andmanagement.

For further information please contact P. Aggarwal at:[email protected]


13

Application of Isotope Techniques in Groundwater Contamination

The applications of environmental isotopes forunderstanding hydrological processes and tracing thesources, movement and fate of contaminants arerelatively well developed. Adoption of the techniquesby water resources managers and policy makers hasbeen less successful. There are many reasons for this,such as lack of knowledge regarding the uniqueinformation provided by isotope techniques, pooraccess to and high cost of isotopic analyses, lack ofeffort to make the isotopic applications relevant,among others.

It has recently been observed that informationdissemination through meetings with water resourcesmanagers and planners generally results in increasedawareness and use of isotope techniques. An executivemeeting under the ongoing RCA project RAS/8/097was organized in Ho Chi Minh City, Vietnam during23–26 May 2006. The main purpose of the meetingwas to discuss the emerging issues of contaminationof groundwater systems in the Member States and toprovide participating end users (water resourcemanagers) with knowledge of advantages and utility

of isotope techniques in tackling the groundwatercontamination problems. 23 representatives fromBangladesh, China, India, Malaysia, Mongolia,Myanmar, Pakistan, Philippines, Sri Lanka, Thailandand Vietnam participated in the meeting.

Individual participants from each of the countriespresented the problems that could be categorized intocommon themes as follows: coastal and inlandsalinisation, landfill leachate, industrial and minewaste effluents, nutrients and pesticides fromirrigation activities, sewage disposal into rivers,naturally high arsenic, fluoride and manganese, andoverexploitation of aquifers causing induced rechargeof wastewater. The conclusion of these presentationswas that very often, the sustainable use ofgroundwater is limited by water quality rather thanquantity considerations. These may be caused byingress of poorer quality water from adjacent aquiferresulting from over-development or it may be a legacyof years of indiscriminant disposal of waste whenenvironmental issues were not of concern. Animportant aspect that has not been traditionally

Participants of the IAEA/RCA Executive Meeting, Ho Chi Minh City, Vietnam.


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Meetings in 2006

• Research coordination meeting on isotopic age and composition of streamflow as indicators of groundwater sustainability, Vienna, 8–2 May 2006

• Consultants meeting to develop geochemical and isotope techniques to evaluate the water flux below the rootzone in irrigation systems, Vienna, 12–15 June 2006

Forthcoming

• Consultants meeting on establishment of national networks for monitoring isotope contents of precipitation,Vienna, 6–8 November 2006

• 5th Meeting of the scientific steering committee of the Global Network of Isotopes in Precipitation (GNIP),Vienna, 9–10 November 2006

• First research coordination meeting of the CRP, Geostatistical analysis of spatial isotope variability to map thesources of water for hydrological studies, Vienna, 27–29 November 2006

• First research coordination meeting of the CRP, Isotope techniques for assessment of hydrological processesin wetlands, Vienna, 4–8 December 2006

• Second research coordination meeting of the CRP, Isotope methods for study of water and carbon cycledynamics in the atmosphere and biosphere, Vienna, 6–8 February 2007

On the Web

The six volumes of the “Environmental Isotopes in theHydrological Cycle” are now available in English, Spanish and French.

These could be downloaded freely in PDF format from the Section’swebsite: http://www.iaea.org/water

considered is the contamination by natural sources ofotherwise fresh waters. The classic case example isthe arsenic laden waters of Bangladesh and WestBengal, India. New occurrences of arseniccontamination of groundwater were reported fromIndia, Pakistan, Vietnam, China, Thailand and

Myanmar. In addition, manganese occurrences werealso reported from India, Bangladesh and Pakistan.

For further information please contact K.M. Kulkarniat: [email protected]


15

Staff of Isotope Hydrology

Mr. Pradeep AGGARWAL

Head of Section and Water Resources Programme ManagerU.S.A., Ph.D. in Geochemistry,Joined the Section in 1997.Tel.: +43-1-2600-21735E-mail: [email protected]

Mr. Luis ARAGUAS-ARAGUAS

Isotope HydrologistSpain, Ph.D. in Geochemistry,joined the Section in 2005.

Tel.: +43-1-2600-21734E-mail: [email protected]

Mr. Andy GARNER

Water Resource Management SpecialistAustria/U.S.A., MSc. in EnvironmentalManagement, joined the Section in 2004.Tel.: +43-1-2600-21739E-mail: [email protected]

Mr. Manfred GROENING

Unit Head, Isotope Hydrology LaboratoryGermany, Ph.D. in Environmental Physics,Joined the Section in 1995.Tel.: +43-1-2600-21740E-mail: [email protected]

Mr. Kshitij KULKARNI

Isotope HydrologistIndia, Ph.D. in Isotope Hydrology, joined the Section in 2001.Tel.: +43-1-2600-21758E-mail: [email protected]

Mr. Turker KURTTAS

Isotope HydrologistTurkey, Ph.D. in Hydrogeology, joined the Section in 2005.Tel.: +43-1-2600-26712E-mail: [email protected]

Mr. Axel SUCKOW

Isotope Hydrologist / GeochronologistGermany, Ph.D. in Env. Physics, joined the Section in 2003.Tel.: +43-1-2600-26762E-mail: [email protected]

Ms. Ornanette AZUCENA

Secretary, Philippines, Tel.: +43-1-2600-21736E-mail: [email protected]

Mr. Timothy CHAVEZ

Data Coordination Clerk, Philippines,Tel.: +43-1-2600-21757E-mail: [email protected]

Ms. Michaela DAVIN

Secretary, Austria Tel.: +43-1-2600-21737E-mail: [email protected]

Ms. Cecilia DEVIA-TORRES

Secretary, ColombiaTel.: +43-1-2600-21738E-mail: [email protected]

Mr. Kamel ZOUARI

Isotope HydrologistTunisia,Ph.D. in Isotope Hydrogeology, joined the Section in 2006.Telephone: +43-1-2600-21733E-mail: [email protected]

Ms. Mari ITO

Isotope HydrologistJapan, Ph.D. in Biogeochemistry with Hydrology and GIS, joined the Section in 2006.Telephone: +43-1-2600-21732E-mail: [email protected]

Mr. Tomas VITVAR

Isotope HydrologistCzech Republic, Ph.D. in Hydrology, joined the Section in 2003.Tel.: +43-1-2600-21741E-mail: [email protected]


The Water and Environment News are prepared twice per year by the Isotope Hydrology Section, Division of Physical and ChemicalSciences, Department of Nuclear Sciences and Applications.

International Atomic Energy AgencyWagramer Strasse 5, P.O. Box 100, Printed by the IAEA in Austria,

A-1400 Wien, Austria September 2006

Water and Environment NewsNo. 21 September 2006

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