Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , Voss et al. , and 1 ; model for five trib- 2013 4 mm and a natural ff , ± ) and local rainfall mea- 2010 model confirms that Northern , , E. J. O. Schrama ff 2 14 mm in Northern Iraq between 2007 ± Trigo et al. UN-ESCWA and BGR ered a severe drought, with rainfall rates 40 % 11533 11534 or 130 ff 3 3 km ± 6 mm. Our findings indicate that man-made groundwater , D. A. M. A. Al-Manmi 1 ± model. The total mass depletion seen by GRACE between ff ). In the same period, discharge of large springs and rivers 2011 , Fadhil 1 , T. N. Olsthoorn 1 ered a drought between 2007 and 2009 and is consistent with the mass loss ff This discussion paper is/has beenSciences under (HESS). review Please for refer the to journal the Hydrology corresponding and final Earth paper System in HESS if available. Delft University of Technology, Delft, theUniversity Netherlands of Sulaimani, Department of Geology, Sulaymaniyah, Iraq extraction has a minor influence inplay this a region key while role. depletion of lake mass and geology 1 Introduction During 2007 till 2009, Northernbelow normal Iraq su levels based on both satellite ( Iraq su observed by GRACE overdicted that by period. the rainfall–runo Also, GRACE2007 and observed 2009 the is mainly annual explainedgroundwater cycle by depletion a of pre- lake 37 mass depletion of 74 utaries of the Tigris River, basedare on precipitation local geology from and Tropicaland climate Rainfall conditions. potential Model Measurement evaporation inputs from Mission GLDASresentation (TRMM) model of parameters. observations, the Our karstified modelin aquifers includes this a that region. rep- cause Observedto large river get natural discharges the groundwater were totalModerate variations used Resolution mass to Imaging variations, calibrate Spectroradiometer welite our (MODIS) corrected altimetry model. in for and In combination lake some order with mass in-situ satel- variations data. derived Our rainfall–runo from Observations acquired by Gravitysion indicate Recovery a And mass Climate lossand of Experiment 2009. 31 This (GRACE) data mis- isregion used including lake as mass an variations. independent We developed validation a of rainfall–runo a hydrologic model of the Abstract Hydrol. Earth Syst. Sci. Discuss.,www.hydrol-earth-syst-sci-discuss.net/11/11533/2014/ 11, 11533–11563, 2014 doi:10.5194/hessd-11-11533-2014 © Author(s) 2014. CC Attribution 3.0 License. surements ( E. H. Smidt 1 2 Received: 3 September 2014 – Accepted: 21Correspondence September to: 2014 G. – Mulder Published: ([email protected]) 17 OctoberPublished 2014 by Copernicus Publications on behalf of the European Geosciences Union. decreased substantially and datamanent from loss the of GRACE water satellite mass mission in indicated the a region per- ( Identifying water mass depletion in Northern Iraq observed by GRACE G. Mulder 5 20 10 15 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , , , , Feni- ). Ad- Werth ; 1997 ) and Gibelin and , Werth et al. 2008 ; ). From 2009 , Kavvas et al. Crétaux et al. ; Ngo-Duc et al. 2010 ; ). Therefore, it is ( 2013 2011 , , 2011 , Altinbilek 2008 2009 , , ), which showed that the Savenije ected the water supply of ). Schmidt et al. ff 2013 Voss et al. McLeman ( 2008 , Al-Manmi ; Schmidt et al. ; Chenoweth et al. 2013 ). Especially in Turkey, water demands , Voss et al. 2006 , 1998 Mariotti et al. 11536 11535 , ; ) and caused a strong decline in crop yields in 2008 2012 , model is developed based on the general hydrology , ). About 100 000 people have left their homes in North- ff Beaumont ; Hinderer et al. 2010 ; model and compared with the results derived from GRACE , ). For the Euphrates and Tigris region, a comparison between ff UN-ESCWA and BGR 2004 , 2011 erent satellite missions are merged with available ground data to Michel et al. , 2004 ff , ). Di Trigo et al. Giorgi and Lionello ; Altinbilek ). GRACE data was used for total water mass calculation. TRMM data was 2011 ). ( ective or non-existent, there are no guarantees that Iraq will ever receive as ff 2003 , Awange et al. Llubes et al. 2009 ), but they are generally coarse due to the lack of ground truth and do not yield ; ) to find lake mass variations. Local hydrologic and geologic data were obtained ; ). Decrease in rainfall and water availability directly a , 2007 , In this paper, a method is presented to determine the contribution of natural water This means that especially Northern Iraq has to cope with a permanent decrease of Several hydrologic studies of the region exist ( Concurrent with decreasing water availability in the region, water demands are fast In this study, a rainfall–runo Ali global hydrologic models like GLDAS, WGHM and GGP ( 2013 developed rainfall–runo and surface water mass. much water as before ( mass variations to the totalvariation in observed the mass study area signal isthe from derived surface from GRACE: GRACE water firstly, using the mass a total is masconGRACE approach. mass calculated to Secondly, and derive subtracted the fromthe water mass natural mass variation variation in observed variation soil by of moisture groundwater and groundwater and mass soil is moisture. calculated using Finally, a newly riparian countries. Because agreements on waterhardly between e riparian countries are either specific information on hydrology and groundwaterGravity storages. Recovery Mass observations and by Climate the more Experiment insight (GRACE), in provide the a terrestrial valuable water tool storages to and give are widely used as a validation of 2007 used for daily rainfall.altimetry MODIS data surface from reflectance the data Envisat, was Jason 1&2 used and in GFO combination satellite with missions ( distan, unpublished data). its water resources over the last years due to lower rainfall and lower river flows from important for the regionavailable water to resources. develop sound hydrological models to2011 keep track on the GRACE and the GLDAS model was made by during fieldwork in cooperationcharge with data of local one water ofdata) experts. the and Obtained Tigris rainfall data river data from tributaries includes four (Directorate stations dis- Dokan in Dam, the unpublished region (Meteorological department Kur- moment, about 42 000 ha ofdevelopment this and irrigation another scheme 500 000 is haditionally, operational, is several with planned dams 53 400 in and ha futureheadwaters under irrigations years of projects ( the are Tigris, under( which construction will in reduce the river Iranian flows in Northern Iraq permanently et al. 2011 increasing during theagriculture last ( years dueincrease to rapidly population due growth toconstruction and the of Southeastern increase dams and Anatolia of irrigation Project irrigated schemes (GAP), in which the includes upstream Tigris the catchment. At this and the main hydrological processes. and geology of the regioncia using et the topo al. flex approachobtain from forcing, calibration and validation data for the model ( 2009 GLDAS model underestimates bothbecause yearly a and groundwater long-term component mass ismodels variations, missing. of most Therefore, Northern likely more Iraq accurate are hydrological needed, to capture the region‘s natural groundwater flow onwards, rainfall rates have beenriod, rising, which but is are in still lineDéqué lower with than the decrease before in the rainfall drought in pe- the region predicted by ( towns and villages ( Northern Iraq ( ern Iraq as a consequence of depleted water sources ( 5 5 25 20 20 25 10 15 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ; 2 ). ). 2 The 1997 . This 2011 ◦ tot , , A cient vari- erences in ff ffi Brooks the total area of i m A ), which shows the large ). 2 ). Beside spatial di 2007 Schrama and Wouters , ; , the north-eastern part consists of 1997 1 , . Half of the flow originates from up- − 2006 1 , − yr man et al. 3 ff Brooks ; Hu 11538 11537 1998 , Swenson and Wahr erent processing steps, mainly to reduce noise, apply geo- gives the elevation map of the total study area, which in- ff 1 Beaumont ), albeit that the method is implemented at a finer resolution so i m P 2014 i m ( ). Figure the percentage of the mascon covered by our study area and A . The mountainous region to the north and northeast is the main source i is the equivalent water height in a particular mascon, m tot i 1 m A H − gives the mascon coverage and the calculation area of about 260 000 km i P m 2004 1 H 2 = , x i P Large lake mass variations atTharthar the had border to area be should included be in avoided. the Especially central lake area (Fig. = – Figure Where To ensure water supply in the region and generation of hydropower, many larger tot 3.1 GRACE mass calculations During the last years, several methodsbased have on been GRACE developed to data calculate like mass ( change 3 Methods Most of Northern Iraq isnates part in of Turkey and the flows upstream inflow catchment southwestern of of direction the the to Tigris Tigris the at river, Persianstream which gulf. Baghdad catchments The origi- is in total about Turkey yearly and 50 km half from tributaries in Northern Iraq ( 2 Study area mascons, the monthly massation variations obtained are from derived the fromaging GRACE the kernels GSM potential information. to coe Although reducethis studies noise research. use in The spatial the outcome aver- equivalent signal, water of height such the is methods mascon obtainedthe were by inversion total mascon. not method water We implemented mass is use variation in the that over following our a relation study time to area: obtain series of H a mascon, total study area. that was used. The study area was chosen based on the following conditions: details. For this studySchrama a et numerical al. solutionthat of mass so-called variations basin canmeans functions be that is retrieved the used in study from diseshave area only with one is an variable split surface approximate water up radius level. in Then, of using a 1 the finite influence functions number of of these basins or mascons, which Most methods comprise di physical corrections, add consistency and improve the ability of GRACE to see spatial 1000 mm yr of water of theon Tigris upstream River river and water ( the arid areas in the southwest are totally dependent climatic variations ina this desert area. climate with While rainfall ratesa the up mountain to range south-western 200 with mm yr part a considerably of colder and the wetter climate catchment and has rainfall rates up to Altinbilek or Iran. The figure alsoand presents 2012 a map based of on the TRMM mean 3B42 yearly rainfall data rates ( between 2002 of Mosul, Dukan, Derbendikhan,baniyah Adhaim and and Qadisiyah Hamrin, influencesAdditionally, two but the large also salt water lakes, Lake massesthe Urmia Tharthar, last and derived decade. Razzazah, Hab- from show water GRACE level declines (Fig. over cludes six main tributaries of the Tigris River of which five have headwaters in Turkey climates, there are alsotures. large Almost seasonal all rain and falls yearlymean during rainfall variations the rates in can winter rainfall drop period by and between fifty November tempera- percent and in March dryand and years. smaller dams are currently under construction. Our study area includes the lakes 5 5 10 15 20 25 10 20 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) and of the 250m of the 1 2 × 2 2011 ( model of Northern is the soil moisture ff G ) can be used as a mea- Crétaux et al. 2004 , of the total 265 000 km ). To obtain total lake mass con- 2 2013 , . But because the hydrology and rainfall 2 is the total area and ) compared to the total water mass deple- Rodell et al. A 11539 11540 2013 , , a comparison is given of the derived stage-area 3 of the lake mass for lake Razazzah. Note that these 1 3 Longuevergne et al. ; erent water bodies. The actual method uses a 250m ff 2013 , ), which includes data from the Envisat, Jason 1&2 and GFO satellite ). To decide whether a cubic regression gives a significant improve- d UN-ESCWA and BGR A d d 1 2013 test was used for a 95 % interval. Total volume change over time was then is the equivalent water height, 2013 ( A − G ( F H yr − − t t 3 Voss et al. A A t Boundaries of the studyaries. area should preferably coincide withThe catchment study bound- area preferably includes full mascons only. km H 3 – – − = Where Finally, the GRACE values have to be corrected for a part of the Urmia catchment From the lake level and lake-area time series stage-area curves were created using To compare the total water mass variation of the rainfall–runo 3.2 Derivation of lake mass The total lake mass variationsregion play ( an important role in the water balance of the Tigris in the northeast. This arearegime is of about the 45 000 area km are are assumed similar to to that beerror in similar in Northern to the calculations these Iraq, on in the atimescale small Northern total these time water Iraq. scale errors mass due It will to variations be is local minor rainfall likely events, due that but the on this a similarities introduces longer between an the regions. made to prevent overestimation ofthe lake lakes mass. are This close the correction borders was of necessary our because study area. This resulted in a reduction of Most of the conditions givenzah, above the are most met using southern the lake, proposed and area. lake For Urmia, lake Razaz- the most northern lake, correction are variation in water depthdesert from areas. the GLDAS model. Subscripts t and d indicate total and sure for the total water massIraq variation then in becomes: the area. The new GRACE values for Northern H that the soil moisture profile from GLDAS ( 250 m resolution). linear or cubic regression. In Fig. tion, and recharge anddo not discharge expect rates significant of groundwater variations the in aquifers this region. are Therefore, very we assumed low in this area, we USDA/FAS missions. Area calculations were basedevation on maps MODIS (DEM), satellite where data theDEM and reflectance to SRTM bands distinguish digital were el- di usedgrid to and comprises detect of water three andfrom steps: the First, the the DEM possible extendareas using of were the a selected lake using minimum was MODIS calculated nally, and reflectance the band maximum exact 5 elevation. lake (1240 nm, borders Secondly, 500 the m were resolution). defined larger Fi- using lake MODIS reflectance band 2 (858 nm, ment, the derived from the stage-volume curve, which is the integral of the stage-area curve. tributions in our studylated. area, The time lake levels series are of derived both from lake satellite level altimetry and by lake area were calcu- curve from our model andIssa a et survey al. done in 2011, which was obtained using sonar by on the water mass depletionlakes between is 2007 of and less 2009, importance. water mass variation of theIraq salt with GRACE, thethe derived southwestern GRACE mass desert, wasstudy which corrected area. is for Because about the the10 95 extended estimated 000 km area volume to of groundwater pumping is small (30–35 lake mass for Lake Urmiatwo salt and lakes mainly contributewithin the to catchment a boundaries gradual mainly decrease show2007 a of till sudden lake 2009, decrease mass, caused during while the by other drought lake of lakes management. Because our focus in this study is mainly 5 5 25 20 20 10 15 25 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , ): 2008 ( fraction ff process, see ). A total num- ff Stevanovic et al. . Additionally, the ; 1 rainfall per year on 2006 , 1 − ). Because these sta- 2010 erent total areas for the , ff ´ y et al. 2011 , ). TRMM data was calibrated Krásn Stevanovic and Iurkiewicz 1998 , and groundwater reservoirs in three ). This resulted in a model structure ). The most convenient way to eval- ). ff Almazroui 2011 2009 2006 ( ( model are calibrated rainfall data from the , Ali and Stevanovic ff Allen et al. 11542 11541 ; in the lower parts, see Fig. 1 ´ ) and reference evaporation derived from GLDAS y et al. − and deep groundwater reservoirs of the infiltrative 2004 ). Therefore, the performance of the model was first ff , due to shallow soil layers, steep slopes and imperme- 5 2007 Werth et al. gives an oversight of the model reservoirs and parame- ff Krásn model was used based on the topo flex approach as , Fenicia et al. ( modelling, because it is strongly influenced by the opera- 4 ff 1 ); erent forcing parameters and di ff − ff day 2010 model, is to use the discharge from the total study area, which ( 2 model ff Rodell et al. man et al. ). Figure ff ff 5 model consists of seven reservoirs, three reservoirs for the unsat- model was calibrated using both GRACE data and river discharge ff ff Hu Savenije erence in rainfall also varies widely. Therefore, the model was run separately ff . A lag function was added to the model to simulate the routing of water through Infiltrative or karstified zone: about onezone third of consists the of surface are karstifiedlimestones of the have limestone mountainous infiltration and rates is,from of 9 therefore, more to than highly 8000 50 infiltrative. m % These and transmissitiviesNon-infiltrative zone: ranging this zone consists ofcharacterised the by other fast mountainous runo areas, which are able underlying formations. Alluvial zone: most ofsilt the sediments. soils In in the thisevents. dry region south flash western floods part are consist common of during clay the and scarce rainfall ; Directorate Dokan Dam, unpublished data) and the bounds of the storage in the 4 Forcing parameters of the rainfall–runo 1. 2. 3. 2009 In this study, aproposed by rainfall–runo 3.3 Rainfall–runo not suitable for rainfall–runo tion of upstream dams andobtain reservoirs. was The for only the suitableLesser river inflow Zab discharge of data catchment Lake we (see Dukan, could Fig. which is located in the upstream part of the data, using methods similaruate to the rainfall–runo could be derived from thecharge total entering discharge the study of area theand from Tigris most Turkey. Unfortunately, river likely this in have data not Baghdad were been minus not measured. the available Additionally, dis- the discharge at those points is average, it can bespatial about di 200 mm yr for all 5 tributaries,geologic with zones. Meanwhile, di thethe setup models. and model parameters were kept the3.4 same for Model calibration The rainfall–runo tions are relatively closethe to region, each it other wascalibration and not values precipitation were possible used rates to to vary calculatefinally base distributed corrected much the daily with throughout rainfall calibrated model from snowfall only TRMM andmodel. and snowmelt on While were values the rainfall derived mountainous from gauges. region the Therefore, GLDAS receives up to 1000 mm yr by linear regressionmaniyah, with Dokan, monthly Derbendikhan precipitation and from Penjwen ( four gauging stations in Sulay- unsaturated reservoir were based on insights of local researchers. TRMM satellite ( climatic parameters ( ber of fourteen parametersduring were calibration used were in restricted the tonality model. minimum and and The ensure maximum realism values bounds, of of towere the model model. based prevent parameters equifi- The on bounds spring of and the river slow discharge reservoir ( runo urated zone, two forFig. the deep groundwater and two for the fast runo based on the geologyNorthern and Iraq topography (Fig. of theters. five The main model consists tributaries of of unsaturated,geologic the fast zones runo Tigris in accordance river with in geologic maps of The rainfall–runo streams and rivers. Theand fast runo non-infiltrative zones werecomparable combined, and share because the the same underlying topography aquifers and ( top soils are 5 5 25 20 10 15 10 25 15 20 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | (1) (2) 4 mm ± ciency (NS) for ffi ). Water mass de- NS) for low flows: e e ff log 2007 , is the average observed o Q ciency ( ffi , the regional average monthly 7 e e ff Schrama et al. gives the pareto front for the average NS and 2 2 11544 11543 ). The total lake mass accounts for 74 6  8  t o m Q Q 8 mm based on the minimum and maximum values   ± ! log log − −
 2 2 GRACE t o t o   Q o Q t m NS the modelled daily discharge. For the model mass performance,  Q Q + m − − log log Q Q t o t o   Q 1 Q 1 =  NS  = T t T t 1 ciency was used. Figure 1 = P = log represents the observed daily discharges, ffi 2 P T t T t + o P − P Q Q 1 shows the resulting GRACE values in terms of equivalent water height (EWH), − = NS 1 7 Q =

Q NS Model calibration was done using a Monte Carlo simulation with randomly chosen Where The uncertainty bounds of the final result are based on the results from other solu- max 4.1 GRACE Figure with an estimated confidence band of 17 mm ( 4 Results and discussion discharge for the Dukanmedium area and was high evaluated flows by and the by Nash–Sutcli the log Nash–Sutcli NS parison with GRACE. Thissimilarities expansion in is the possible region, due whichthe to means total the that region incorporation we based can on of data predict geologic of the the hydrologic smaller behaviourparameter Dukan of area. values for every model run within the given parameter bounds. The total evaluated for this area and then expanded to the whole of Northern Iraq to allow com- To compare the total lakeadded mass up change and with divided GRACE,mass all variation by lake in the volume terms total variations of were area EWH of (Fig. the region, resulting in the surface water the yearly rainfall sumAfter and 2009, the are yearly largest rainfallcoulde amounts before be have 2007 the increased reason and but of are smallest the still during persistent relatively low low, 2007–2009. which GRACE4.2 values in that Surface period. water variations. Yearly variation is 171 between 2003 and 2011.rainfall In is given the for lower therainfall. graph The same of periods period with Fig. to moreGRACE show than the values average relation as rainfall between generally aeas. coincide GRACE consequence The with values drought of increasing and period accumulation between ofwater 2007 mass, and rainwater while 2009 in the coincides the water withafter mass an catchment the is overall ar- drought. decrease more The in or magnitude less stable of during the the yearly periods variations before in and water mass coincides with during 2007 to 2009. Becausevariations in from soil the moisture wet and temporal seasonto depression water get storage, mass those an values can approximation are vary not ofyearly due useful groundwater minimum to and large surface values waterlogical were mass cycle used, depletion. and Therefore, which are are the best least representation influenced of by groundwater and the surface yearly water mass hydro- pletion between 2007 and 2009minimum is GRACE values 130 during mm the with years a before SD and the of years 14 after mm, the based drought on period the average log daily discharge and only the NS e tions on the pareto front. logNS of the riversolution discharge was chosen and based the on2012: the NS following for condition for the the water period between mass. 2004 The and presented optimal 5 5 25 20 10 15 10 20 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er, ff water 1 − reservoir, yr during the ff 3 3 6 mm between and unsaturated ± UN-ESCWA and ), but their values ; ff model are given in ff 2013 2004 ( erence in snow and lake , 4 mm to the yearly water ff ± model of the entire study area 3 mm. The fast runo ff erences between the results of ff ± ). Di 7 mm. Because the snow melts away ± 2013 5 mm and a decline of 34 ( Longuevergne et al. ± erences in the size of the studied basins, but ff 11546 11545 5 mm of the yearly water mass variation. This 2 and 43 ± 2 mm. Both reservoir storages have, therefore, no ± er mainly in the winter and summer peaks. During Stevanovic and Markovic ff ± Voss et al. model. The rainfall–runo ff comprises a period with stable groundwater levels till 2007, 6 mm to the water mass depletion between 2006 and 2009. 9 ± give a good illustration of this process. Snow mass accumulates 8 ). After 2009, modelled groundwater levels remained stable because rainfall compares the variation of the total water mass variations in the study area from 9 2013 , together with the contribution of the groundwater, fast runo , 9 The unsaturated reservoir shows the same pattern every year, with wet top soils reservoir as given in Fig. means that more thanof 50 surface % water of mass. the Suchthe total declines whole water in Euphrates mass surface and water depletion Tigris mass is basin were caused by already by claimed a for decline of the water mass depletion and 55 shows an average yearly variation2007 of and 138 2009. The twothe graphs wet di winter period,with patterns generally larger are peaks the in same, the but GRACE the data. amplitudes Possible causes of are the underestimation peaks di 4.4 GRACE and modelled values Figure GRACE and the rainfall–runo during the rainy season andage dry yearly or variation almost of dry thewhich unsaturated conditions reservoir during represents is dry overland 63 periods. flow Theduring and aver- and interflow shortly in after intense thevalues rainfall basin, events. are During shows relatively the peaks periods highvariation up with and of high to decrease rainfall, the 60 the fast fast mm reservoir whensignificant is the influence 38 on rains the end. watercontribution The mass to average the depletion yearly yearly on variation the with longer 100 term, mm of but the have total a of large 170 mm EWH. rates were still belowresult average, in but a a rise of sequence groundwater of levels and years a with revival higher of spring rainfall discharge. will likely drop. In the governorates ofemerges Sulaymaniyah and every Duhok year alone, from aboutBGR 1.5 springs km ( followed by a period withriod groundwater with depletion stable from groundwater levels 2007 fromaquifers till 2010 plays 2009, till an and 2012. important a Groundwater role from secondbecause in the pe- the karstified of groundwater its depletion between highduring 2007 recharge dry and 2009, periods. during While wetyears, the periods aquifers there still and is discharge fast much water discharge less through through springs replenishment springs during of dry groundwater and groundwater levels will The total waterFig. mass variations derived from the rainfall–runo this water has been routedmass to the peaks lakes in and Fig. reservoirs. Theduring di winter and almostthe all region. snow melts Snow away massshow during values a spring, yearly were feeding variation acquired the betweenevery from reservoirs 11 spring, GLDAS in snow (Rodell water etdoes mass not al., only influence 2004) influences water and mass the depletion yearly at water a longer mass4.3 time variations scale. and Natural groundwater variations reservoirs. Modelled groundwater variationsmass contribute variations 38 and 37 This is about twothe total third water of mass depletion. thealso The total explains large why contribution groundwater those of depletion the valuesGLDAS natural and where does groundwater not at mass not reproduced least by include one the groundwater GLDAS fourth storage. model, of because The time series for the groundwater Hamrin, Dukan and Mossoul,study had period. a The relatively total large volumethe contribution water decline of level those of variation smaller at in lakespeaks those least is in lakes mainly 5 lake km is because mass much lag largerwater mass than behind increases the the during major peaks winter lakes. in due The to GRACE yearly snowfall mass, and which rainfall, while is it because takes the time untill total these researches are likely causedexclusion by of di mostly smaller lakes can also play an important role. For example, lakes are higher than those given by 5 5 25 20 10 15 20 10 15 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ff Voss ; 2011 14 mm. This , ± erent hydrologic pro- ff Kavvas et al. ; 2011 , 11548 11547 Chenoweth et al. 6 mm of equivalent water height, the contribution of ± ers the possibility to quantify the di ff erence between the modelled and the literature values. The peaks ff model. Although most of the residuals appear to be random, there is shows the residuals of the water mass derived from GRACE and of the ff ), main aquifers and water storages were modelled seperately. Results are, 10 2013 , The dependency of this region on surface water is also reflected by the large water Especially, in the limestone aquifers of Northern Iraq, strong groundwater variations Figure model helps to give insightsconcerned in countries the and available can water bements. resources Contrary used and to as water other a flows studies base like between ( for water allocation and water agree- aquifers is unlikely, as thesupply groundwater is table mainly can supported vary byin surface strongly those water. and Additionally, areas almost the are all regional directly irrigation water linked schemes to large reservoirs. mass variations of theEWH surface observed water, by which GRACE.demands contributed With about from 75 decreasing riparian mm waterwater countries out management availability of in tools and 130 the is mm increasing Tigris growing, water including river transboundary catchment, models. the The developed need for reliable shows that natural groundwatermass variation values has are to used be to determine taken overdraft into of account aquifers. whenare GRACE common duetion to rates, extensive feeding karst numerous networks springs with in high the region. transmissivities Therefore, and overpumping infiltra- of these natural varation is about two third of the total groundwater depletion of 56 from GRACE data, whichthe gives region. an With indication a of depletion of the 37 human impact on groundwater in 5 Conclusions 5.1 Water masses in Nothern Iraq The presented approach o cesses in the regionand as groundwater well in as the total toshows water quantify the mass natural the variation. groundwater shares More variation of importantly, in the surface contrast overal water, model to soil the moisture total groundwater variation reduction factors for the massyears before of 2005 lakes is Urmia likelya and caused spin-up Razazzah. by period The the of fast spin-up 7overestimated. increase years, period in but of the before the 2002 model. rainfall The estimates model are has unreliable and likely this case, human water usestill can used play for an water important supplytion. role, or Another because agriculture local possible during cause water dry storage isperiod, periods, is the but contrary reduced this to amount term a of is natural vegetation probably situa- water negligible. during the dry rainfall–runo a slight downward trendfore. from This 2005 could onwards indicate and groundwater a extraction stronger in increase the in region, the but years also be- an error in the are 23 % onsions average. or Other water possible mass causes variabilitymaximum are of storage additional of smaller the lakes. water unsaturated Increate storage zone theory, a in to we fit large could depres- the have di during given changed summer curves the are better, also but smaller this in would the model compared to the derived GRACE data. In of accumulated snow water or random errors in rainfall rates from TRMM data; these are scarce, this iscauses valuable the information. However, water it variations isgeology in and not these river possible discharges. regions to Thisuse without determine data of additional what can in-situ data partly data on be is precipitation, obtained still from of satellites, vital but importance. the In our situation, there was only little data 5.2 Model structure and input data This research showed that GRACEmodels can because be it an gives importantregion. Especially direct data in source Northern measurements Iraq, in of where rainfall–runo water the resources and total data on water water resources balance of a larger on both satellite and in-situ data, which enhances its reliability and predictive power. therefore, more useful to water managers. Moreover, the model is based and calibrated et al. 5 5 25 20 10 15 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , , 11535 11536 11535 , 2011. 11536 11548 10.1007/978- , , 2011. , 2011. 11537 , . Secondly, snow- 11542 11535 ff and total water mass. 11535 ff 11535 11537 , 2011. , 2011. 11535 , 2004. , 1997. , 1997. 11541 , 10.1080/17538947.2010.489971 10.1016/j.asr.2011.01.004 10.1016/j.rse.2010.11.014 http://www.fao.org/docrep/x0490e/x0490e00. 11536 11542 11549 11550 model. Finally, GRACE mass calculations and ff , 2011. 10.1029/2010WR010269 10.1016/j.atmosres.2010.11.006 10.1080/07900629749719 10.1080/07900629749700 GRACE mascon solutions for remote sensing Australian hydrol- ◦ 4 10.1080/07900620310001635584 11541 × , 2010. 10.1029/2010WR010174 (last access: 20 December 2013), 1998. 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330 325 320 Survey 2011 Model Satellite measurements 315 ). erent lakes to the total water mass depletion. ff Waterlevel (m) 2013 11555 11556 ( 310 305 Issa et al. Comparison stage−area curves for Mossul Lake 300

200 150 100 350 300 250

) (km Area Total 2 Linear regression stage-area curve for lake Mossul. The curve is compared with Mascon coverage area for GRACE calculations. In the south-west the included desert Figure 3. a survey in 2011 using sonar by Figure 2. area and in the north-eastof the the included used Urmia mascons catchment. and The thesize larger red of dots circles the the show location the dots ofLake coverage indicates large Tharthar, lakes the in and the contribution reservoirs southwestern in of part, the di area. shows The the largest water mass depletion. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | w o l f m a e r t processes, which S ff α , A f K A s P K l a i v ε f u u l S l S E A

s A S β , A u S

A γ δ

α , H f K e v i 11558 11557 P t a r t l i ε f u f S S n E I

). (right) Boundaries of main tributaries of the Tigris in model based on the three main land classes in Northern n o ff N N β H , 2008 s H K u , S I

I s γ β S , H u e S v i t a r t E l u i f S ε n I P (left) Approximate division of Northern Iraq into three geologic zones, mainly based Setup of the rainfall–runo Stevanovic and Iurkiewicz Figure 5. on ( Northern Iraq with thesurements Dukan from area the given Dukancatchment in area of red. Northern and Calibration Iraq. calibration on for streamflow water is mass based is on based mea- on the whole Tigris Figure 4. consist of overlandstorage, flow which and is interflow.calculated the The based main two on reservoir focus lower levels in and reservoirs model this represent parameters. study. the The groundwater water fluxes, indicated with arrows, are Iraq. The upper three reservoirsmiddle (Su) two represent reservoirs the (Sf) water represent storage the in water the unsaturated storage zone, related the to fast runo Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | axis y axis the model performance for the x 11560 11559 GRACE values and monthly precipitation for extended study area. During the wet Model performance for river flow and GRACE values for all model runs. On the Figure 6. averag NS and logNS model performance for river flow at the inflow of lake Dukan. Figure 7. winter periods, water accumulates inmass the depletion region occured and during total seasons water of mass 2007/08 increases. and Largest 2008/09. water the NS model performance for GRACE mass and on the Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ff 11562 11561 erent model elements smoothed over 10 days, show- ff Left: water mass of the di Lake and snow mass for extended study area. Snow accumulates during winter and Figure 9. ing a permanent declinereservoirs. of Right: total groundwater water and massmodel a of for GRACE recurrent Northern minus pattern surface Iraq. water for mass the and unsaturated the rainfall–runo and fast Figure 8. melts away during spring,when while river lakes discharges shows drop. the highest water levels at the end of the spring Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 11563 Residual water mass in EWH from the observed GRACE values minus lake mass, Figure 10. snow mass and modelled soil moisture and groundwater mass.