Abstract Groundwater, a key part of the hydrological cycle, is under increasing pressure from different land uses and changing climate. However, less attention has been paid to integrated groundwater management than surface waters. This thesis combined hydrological and socio-economic research for the case study of the Rokua esker aquifer in order to update current concepts of groundwater management. The Rokua area contains groundwater-dependent lakes and a periodic water level decline has raised concerns about the future of these lakes. Peatland drainage in the vicinity of the aquifer has been accused of changing the aquifer conditions. Groundwater discharge from the esker aquifer to drained peatland was studied to identify relevant hydrological processes for groundwater-surface water interactions. The results revealed a connection between the aquifer and the peatland whereby groundwater can enter the ditches through seepage or preferential flow. Modeling was used to determine critical factors in the management of the esker aquifer-peatland system. The results showed that climate and land use can affect esker groundwater, while peatland drainage in the vicinity can have similar impacts to groundwater abstraction and drought. Peatland restoration by filling in drainage ditches could possibly restore the aquifer groundwater levels. However, for the Rokua aquifer, which will possibly experience less severe dry periods in the future, extensive drainage restoration is currently too major, uncertain, and expensive a measure relative to the expected benefits. Multi-criteria decision analysis was used to identify ways of facilitating stakeholder involvement and learning in groundwater management. The results obtained with this participatory process confirmed that it can foster learning on complicated groundwater issues and collaboration in a process encompassing disputes and diverse interests. The decision analysis process led to the initiation of dialogue on more integrated management, where the preferences of all stakeholders were discussed and taken into account. Overall, this thesis shows how different aspects of aquifer management, such as land use, climate, ecological and economic values, and stakeholder preferences, can all be taken into account using a combined method which reduces the mistrust between opposing interests through research and information, resulting in more robust future planning. / Tiivistelmä Pohjaveteen, hydrologisen kierron avainosaan, kohdistuu kasvavia paineita eri maankäytön muodoista ja ilmastonmuutoksesta. Pohjaveden hallintaan ei kuitenkaan ole kiinnitetty tarvittavaa huomiota. Tässä väitöstyössä yhdistettiin hydrologista ja sosioekonomista tutkimusta Rokuan harjualueella pohjaveden hallintakonseptin päivittämiseksi. Rokuan alueella on useita pohjavedestä riippuvaisia järviä, joiden vedenpinta on kausittain laskenut voimakkaasti. Pintojen lasku on kasvattanut paikallisten huolta järvien tilasta. Harjua ympäröivät metsäojitetut turvemaat, ja ojituksia on syytetty pohjaveden tilan ja sitä kautta myös järvien tilan heikkenemisestä. Työn ensimmäisessä osassa tutkittiin pohjaveden hydrologisia purkautumisprosesseja harjun pohjavesiesiintymästä ojitetulle suoalueelle. Tulokset osoittivat hydraulisen yhteyden akviferin ja turvemaan välillä: pohjavesi pääsi purkautumaan metsäojiin joko suotautumalla tai turpeen kaksoishuokoisuusrakenteiden kautta. Seuraavassa vaiheessa työtä pohjavesimallinnusta käytettiin määrittämään kriittisiä pohjaveden tilaan vaikuttavia tekijöitä pohjavesi-turvemaa-systeemissä. Mallinnustulosten perusteella niin ilmasto kuin maankäyttökin vaikuttavat kumpikin suoraan pohjaveden pinnankorkeuden tilaan. Turvemaiden ojituksilla pohjavesialueella voi olla samoja vaikutuksia pohjaveden pinnankorkeuden tasoihin kuin pohjaveden otolla tai kuivilla kausilla. Turvemaiden ennallistaminen ojia täyttämällä voi osittain palauttaa vedenpinnan tasoja pohjavesialueella. Rokuan harjualueen tapauksessa suuren mittakaavan oja-alueiden ennallistaminen todettiin kuitenkin liian epävarmaksi ja kalliiksi toimenpiteeksi hyötyihin nähden, varsinkin jos kuivien kausien vaikutus suurilla harjualueilla heikkenee tulevaisuudessa sademäärien kasvun myötä. Työn kolmannessa osassa käytettiin monitavoitearviointia eri sidosryhmien osallistamiseen ja oppimiseen pohjavesien hallinnassa. Osallistavasta prosessista saadut tulokset vahvistivat, että menetelmää voidaan käyttää oppimisen edesauttamiseen vaikeissa pohjavesiasioissa sekä yhteistyön muodostamiseen ristiriitaisessa ja monimutkaisessa tapauksessa. Monitavoitearvioinnin prosessi johti keskustelun avaukseen yhtenäisemmän suunnittelun puolesta, joka ottaa huomioon eri sidosryhmien näkökulmat ja tuo ne osaksi keskustelua. Tämä väitöstyö osoitti miten eri pohjavesialueen hallintaan tarvittavat näkökulmat, kuten maankäyttö, ilmasto, ekologiset ja ekonomiset arvot, sekä sidosryhmien mielipiteet voidaan kaikki ottaa huomioon yhdistämällä eri metodeja. Näin tutkimuksella ja informoinnilla vähennetään epäluottamusta eri intressitahojen välillä ja luodaan pohja vakaammalle pohjavesialueiden tulevaisuuden suunnittelulle.

<p>Topography is one of the primary drivers of physical processes in the rivers and floodplains. Advances in remote-sensing and survey techniques have provided high-resolution representation of the floodplains but information regarding the 3D representation of river channels (commonly known as river bathymetry) is sparsely available. Field surveys along an entire river network in a watershed remains infeasible and algorithms for estimating simple but effective characterization of river channel geometry are hindered by an incomplete understanding of the role of river bathymetry in surface and subsurface processes. </p> <p> The first objective of this dissertation develops an automated framework – System for Producing RIver Network Geometry (SPRING) for improving the geospatial descriptors of a river network. The tool takes as input the DEM and erroneous river centerline to produce spatially consistent river centerlines, banks, and an improved representation of river channel geometry. SPRING can process entire river networks and is not limited single reach applications. The proposed framework is flexible in terms of data requirements, resolution of output datasets and user preferences. It has a user-friendly graphic user interface (GUI) and is appropriate for large-scale applications since it requires minimal user input.</p> <p> A better understanding of the role of bathymetric characteristics in surface-subsurface hydrology and hydrodynamics can facilitate an efficient incorporation of river bathymetry in large river networks. The second objective explores the level of bathymetric detail required for accurately simulating surface and subsurface processes by developing four bathymetric representations using SPRING with reducing level of detail. These bathymetric configurations are simulated using a physically based tightly coupled hydrologic and hydrodynamic model to estimate surface and subsurface fluxes in the floodplains. Comparison of fluxes for the four bathymetric configurations show that the impact of river bathymetry extends beyond surface routing to surface water – groundwater interactions. Channel conveyance capacity and thalweg elevation are the most important characteristics controlling these interactions followed by channel side slope and channel asymmetry. </p> <p> The final objective aims to develop benchmarks for bathymetric characteristics for accurately simulating flooding related physical processes. The sensitivity of surface and subsurface fluxes to error in channel conveyance capacity is investigated across reaches with varying geomorphological characteristics. SPRING is used to create six bathymetric configurations with varying range of error in channel conveyance capacity (ranging from 25% to 300%). They are simulated using a tightly coupled physically distributed model for a flood event and the estimates of water surface elevation, infiltration and lateral seepage are compared. Results show that incorporating channel conveyance capacity with an error of within 25% significantly improves the estimates of surface and subsurface fluxes as compared to those not having any bathymetric correction. For certain reaches, such as those with high drainage area (>1000km²) or low sinuosity (< 1.25), errors of up to 100% in channel conveyance capacity can still improve H&H modeling.</p>

Les eaux souterraines constituent une réserve d’eau potable non négligeable, leur alimentation se fait en majeure partie par les précipitations, appelée recharge des nappes. Du fait de leur grande importance, la compréhension du fonctionnement de ces ressources en eau est plus que jamais indispensable. Celle-ci passe par l’élaboration de modèles mathématiques. Ces outils nous offrent une meilleure appréhension et une bonne prévision des phénomènes physiques. Les systèmes hydrogéologiques sont généralement très complexes et caractérisés par des dynamiques hydriques très variables dans le temps et dans l’espace. Cette complexité a attiré l’attention de nombreux hydrogéologues et un grand nombre de modèles très sophistiqués a été développé afin de décrire ces systèmes avec précision. Cependant, la prise en compte de la recharge de ces réservoirs reste toujours un défi dans la modélisation hydrogéologique. En effet, le plus souvent, les modèles hydrogéologiques simulent l’écoulement dans la nappe tout en considérant la recharge comme une constante sur le domaine et indépendante du système. De plus, elle est souvent calculée de façon simplifiée. Or, la recharge traduisant la quantité des précipitations atteignant les nappes est une composante hydrologique complexe et variable car elle interagit avec les nappes et dépend des conditions climatiques, du couvert végétal et du transfert de l’eau dans le sol. Ce présent travail vise à intégrer cette recharge variable et complexe aux modèles hydrogéologiques. À cet effet, un modèle couplé a été développé. Une première partie de ce modèle permet de calculer la recharge des nappes en modélisant les interactions précipitations-sol et l’hydrodynamique dans le sol. Cette modélisation a été effectuée en utilisant des modèles conceptuels simples basés sur des lois empiriques (Gardénia, Nash) et des modèles physiques résolvant l’équation de Richards. La recharge ainsi calculée est intégrée à la deuxième partie du modèle simulant l’hydrodynamique dans les nappes décrite par l’équation de diffusivité. Des méthodes numériques précises et robustes ont été utilisées pour résoudre les équations du modèle mathématique : les éléments finis non conformes ont été utilisés pour résoudre l’équation de diffusivité et l’équation de Richards est résolue sous sa forme mixte par une méthode itérative en temps. En somme, ce modèle couplé permet de décrire les variations de niveaux de nappe à partir des données météorologiques connaissant les paramètres caractéristiques de cet aquifère. [...] / Groundwater is the main available water resource for many countries; they are mainly replenished by water from precipitation, called groundwater recharge. Due to its great importance, management of groundwater resources is more essential than ever, and is achieved through mathematical models which offer us a better understanding of physical phenomena as well as their prediction. Hydrogeological systems are generally complex thus characterized by a highly variable dynamic over time and space. These complexities have attracted the attention of many hydrogeologists and many sophisticated models that can handle these issues and describe these systems accurately were developed. Unfortunately, modeling groundwater recharge is still a challenge in groundwater resource management. Generally, groundwater models are used to simulate aquifers flow without a good estimation of recharge and its spatial-temporal distribution. As groundwater recharge rates show spatial-temporal variability due to climatic conditions, land use, and hydrogeological heterogeneity, these methods have limitations in dealing with these characteristics. To overcome these limitations, a coupled model which simulates flow in the unsaturated zone and recharge as well as groundwater flow was developed. The flow in the unsaturated zone is solved either with resolution of Richards equation or with empirical models while the diffusivity equation governs flow in the saturated zone. Robust numerical methods were used to solve these equations: we apply non-conforming finite element to solve the diffusivity equation and we used an accurate and efficient method for solving the Richards equation. [...]

The region of interest is part from Iraqi western desert covering an area about 100,000 km². Several of the large wadis such as Hauran, Amij, Ghadaf, Tubal and Ubaiydh traverse the entire region and discharge into the Euphrates River. The present study included the following hydrogeological investigations: Lineaments interpretation was done by using different data sets (SRTM 30 m and Landsat ETM 15m), within different algorithms. Some faults recognized by field survey match rather well with the automatically extracted lineaments with only a small difference between field data and re-mote sensed data. The groundwater flow directions (west to east) for three aquifers were determined by using different spatial interpolation algorithms. Due to the faults impact, the flow direction gets a slightly other direction when reaching the fault’s zone. Two pumping test were performed close to fault 2 in the unconfined aquifer Dammam using well no. 9 and 17. Results of pumping test and recovery were evaluated with the analytical model MLU for Windows. Well 17 shows a slightly higher transmissivity (0.1048 m²/min) in compari-son to well 9 (T= 0.0832 m²/min). This supports the assumption of a zone of unique elevated permeability between fault 1 and fault 2 because of the tectonic stress and the anticline structure. The catchment and watershed delineation was performed by means of four GIS packages utilizing three DTM´s: 90 m and 30 m SRTM (Shuttle Radar Topography Mission) and the ASTER 30 m. A thorough field survey and manual catchment delineation of the same area was available from Division 1944. Software used was Arc Hydrotools, TNTmips, River Tools and TecDEM. Ten 90 m SRTM and twelve 30 m ASTER files were merged by means of ArcGIS. The 30 m SRTM dataset of Iraq was supplied by courtesy of the US Army and the region of interest (ROI) was clipped from this DTM using ArcGIS. No additional steps were performed with both DTM data sets before using the mentioned software products to perform the catchment analysis. As a result the catchment calculations were significantly different for both 30 m and 90 m data and the different software products. The groundwater model implemented in Visual Modflow V.4.2 was built by 5 main layers repre-senting Dammam aquifer, first aquiclude, UmEr Duhmma aquifer, second aquiclude and the Tayarat aquifer. Averaged readings of groundwater head from 102 observation wells were used to calibrate the model. Calculated recharge average was 17.5 mm/year based on the water balance for ~30 years (1980-2008). A sensitivity analysis was performed by using different permeability and recharge values. However, the model showed a rather low sensitivity because the values of the standard error of the estimation were between 2.27 m and 3.56 m. Models with recharge less than 11.85 mm/year or more than 60 mm/year did not converge and thus failed to produce a result. Models with Kf values from 1.1-3 to 1.1-4 m/s for aquifers and from 1.1-7 to 1.1-8 m/s for aquicludes converged. Water budget is about 2.17*10¹⁰ m³/year; by irrigating the greenhouses this budget will cover only 1.75% of the total area. However, this value could be upgraded up to 8 – 9 % by utilizing the groundwater inflow from Saudi Arabia.:List of Content Page Dedication ………………………………..………………..2 Acknowledgment ………………………………..………………..3 List of contents …………………………………..……………..4 List of Figures ………..……………………………..….......…8 List of Tables ………..……………………………….…….…9 List of abbreviations ………..……………………………….………10 English Abstract ……………………………………….………..12 German Abstract ..………………...…………………….……….14 1 Introduction ………..……………………………….………16 1-1 Preface ………..……………………………….………16 1-2 Region of interest ………..……………………………….………16 1-3 Previous Studies ………..……………………………….………17 1-3-1 Local studies ………..……………………………….………17 1-3-1-1 Hydrogeological Studies ………..………………………….…….17 1-3-1-2 Remote Sensing Studies ………..………………………….…….18 1-3-2 Global studies …..……………………………….…….18 1-3-2-1 Groundwater flow and fracture zone ..………………………...19 1-3-2-2 Lineaments extraction ………..…………………………….….19 1-3-2-3 Watershed delineation ………..……………………….……….20 1-4 Importance of investigation area ……………..………………..…24 1-5 Motivation ………..……………………………….…….…24 1-6 Deliverables ………..……………………………….………24 1-7 Problems ………..……………………………….………26 2 Methodology ………..……………………………….………27 2-1 Literature review ………..……………………………….………27 2-2 Personal contact ………..……………………………….………27 2-3 Field work ………..……………………………….………27 2-4 Evaluation of geological data ………………………….………27 2-4-1 Geological cross section ….……..……………………….27 2-4-2 Fault system by means of remote sensing techniques …..………28 2-5 Climate and Meteorology..…..………………………………....……28 2-5-1 Meteorological data ………..……………………………….………28 2-5-2 Aridity index ………..……………………………….………28 2-5-3 Groundwater recharge ………..…………………………….….29 2-5-4 Vegetation index ………..……………………………….………29 2-5-5 Actual evaporation ………..……………………………….………30 2-5-6 Soil moisture ………..……………………………….………32 2-5-7 Runoff ………..……………………………….………32 2-6 Hydrogeology ………..……………………………….………34 2-6-1 Pumping test ………..……………………………….………34 2-6-2 Groundwater flow ………..……………………………….………34 2-6-3 Wadi catchment delineation ……………………………….…34 2-6-3-1 Dataset ………..……………………………….………34 2-6-3-2 Approaches ………..……………………………….………34 2-6-3-3 Software packages ………..……………………………….………35 2-6-4 PC options ………..……………………………….………39 2-6-5 Groundwater Model ………..……………………………….………39 2-6-5-1 Conceptual model ………..……………………………….………40 2-6-5-2 Input ………..……………………………….………41 2-6-5-3 Properties ………..……………………………….………41 2-6-5-4 Boundary conditions ………..……………………………….………41 2-6-5-5 Observation wells ………..……………………………….………42 2-6-5-6 Solver ………..……………………………….………42 2-6-5-7 Calibration ………..……………………………….………42 3 Geological setting ………..……………………………….………44 3-1 Preface ………..……………………………….………44 3-2 Tectonic and structure …………………………………………..…...44 3-3 Stratigraphy ………..……………………………….………46 3-3-1 Tayarat formation ………..……………………………….………47 3-3-2 Umm Er Radhumma formation ………………………………....47 3-3-3 Dammam formation ………..……………………………….………48 3-3-4 Euphrates formation………..…………………………………………48 3-4 Topography and Ubaiydh Wadi …………………………………49 4 Climate and meteorology.…………………………………..………51 4-1 Preface ………..……………………………….………51 4-2 Precipitation ………..……………………………….………51 4-3 Temperature ………..……………………………….………52 4-4 Potential evaporation …………………………………………53 4-5 Relative humidity ………..……………………………….………54 4-6 Wind ………..……………………………….………55 4-7 Sunshine duration ………..……………………………….………56 5 Hydrogeology ………..……………………………….………57 5-1 Preface ………..……………………………….………57 5-2 Tayarat aquifer ………..……………………………….………57 5-2-1 Pressure conditions ………..……………………………….………57 5-2-2 Hydraulic characteristics …………………………………………57 5-2-3 Water quality ………..……………………………….………58 5-3 Um Er Radumma aquifer …………………………………………58 5-3-1 Pressure conditions ………..……………………………….………58 5-3-2 Hydraulic characteristics …………………………………………58 5-3-3 Water quality ………..……………………………….………59 5-4 Dammam aquifer ………..……………………………….………59 5-4-1 Pressure conditions ………..……………………………….………59 5-4-2 Hydraulic characteristics …………………………………………60 5-4-3 Water quality ………..……………………………….………60 6 Result and discussion …………………………………………61 6-1 Topographic contour map …………………………………………61 6-2 Geological cross section …………………………………………62 6-3 Lineaments evaluation …………………………………………65 6-4 Groundwater flow ………..……………………………….………66 6-5 Pumping test evaluation …………………………………………70 6-6 Catchment calculation …………………………………………72 6-7 Water balance and Recharge ……………………………….…76 6-8 Groundwater model ………..……………………………….………78 6.8.1 Model sensitivity ………..……………………………….………80 6.8.2 Groundwater management ……………………………….…83 7 Conclusion and recommendations …………………………………84 7.1 Conclusion ………..……………………………….…….…84 7.2 Recommendations ………..……………………………….…….…85 8 References ………..……………………………….………86 9 Appendixes ………..……………………………….………90 10 Field work Photos ………..……………………………….………115 11 Author CV. ………..……………………………….………116 / Das Untersuchungsgebiet umfasst eine Fläche von etwa 100.000 km² und ist Teil der westlichen irakischen Wüste. Einige der großen Wadis wie Hauran, Amij, Ghadaf, Tubal und Ubaiydh durchqueren die gesamte Region und entwässern in den Euphrat. Die vorliegende Arbeit umfasst folgende hydrogeologische Untersuchungen: Die Interpretation der Lineamente wurde anhand verschiedener Datensätze (SRTM 30 m und Landsat ETM 15 m) und unter Nutzung unterschiedlicher Algorithmen durchgeführt. Einige Störungen, welche während Feldmessungen identifiziert wurden, stimmen gut mit automatisch extrahierten Lineamenten überein, der Unterschied zwischen Feld- und Fernerkundungsdaten ist somit gering. Die Ermittlung der Grundwasserfließrichtungen (von West nach Ost) der drei Aquifere erfolgte unter Nutzung verschiedener Algorithmen zur räumlichen Interpolation. Es zeigte sich, dass die Störungen zu einer leichten Veränderung der Fließrichtung mit zunehmender Nähe zur Störungszone führen. Zwei Pumpversuche in den Brunnen 9 und 17 wurden nahe der Störung 2 im ungesättigten Aquifer Dammam durchgeführt. Die Auswertung der Ergebnisse der Pump- und Wiederanstiegsversuche erfolgte mittels des analytischen Modells MLU für Windows. Es zeigte sich, dass Brunnen 17 eine leicht höhere Transmissivität aufweist (T = 0,1048 m²/min) im Vergleich zu Brunnen 9 (T = 0,0832 m²/min). Dies unterstützt die Annahme der Existenz einer Zone erhöhter Permeabilität zwischen den Störungen 1 und 2, verursacht durch tektonischen Stress und die Antiklinalstruktur. Die Erfassung von Einzugsgebiet und Wasserscheiden erfolgte anhand von vier GIS-Paketen unter Nutzung von 3 DTM’s: 90 m und 30 m SRTM (Shuttle Radar Topography Mission) sowie ASTER 30 m. Genaue Daten aus einer Feldkampagne und eine manuelle Abgrenzung des Einzugsgebietes derselben Region standen zur Verfügung (Division 1944). Als Software kamen Arc Hydrotools, TNTmips, River Tools und TecDEM zum Einsatz. Zehn SRTM- (90 m) und zwölf ASTER-Files (30 m) wurden mittels ArcGIS vereinigt. Ein 30 m SRTM-Datensatz des Irak (bereitgestellt durch die US-Armee) diente als Grundlage für das Ausschneiden des Untersuchungsgebietes (ROI) mit Hilfe von ArcGIS. An beiden DTM Datensätzen wurden vor der Ermittlung des Einzugsgebietes mit den genannten Software-Produkten keine zusätzlichen Schritte durchgeführt. Als Resultat ergaben sich signifikante Unterschiede zwischen den 30 m und 90 m Datensätzen sowie der verschiedenen Software. Das in Visual Modflow V.4.2 implementierte Grundwassermodell wurde aus fünf Hauptschichten bestehend aus Dammam Aquifer, erster Stauer, UmEr Duhmma Aquifer, zweiter Stauer und Tayarat Aquifer aufgebaut. Durchschnittliche Werte der Grundwasserstände aus 102 Observationsbrunnen dienten der Kalibrierung des Modells. Die berechnete mittlere Grundwasserneubildung betrug 17,5 mm/a, basierend auf dem Wasserhaushalt der letzten 30 Jahre (1980-2008). Unter Einbeziehung verschiedener Werte für Permeabilität und Grundwasserneubildung wurde eine Sensitivitätsanalyse durchgeführt. Dabei ergab sich allerdings eine geringe Empfindlichkeit des Modells, resultierend aus einer Standardabweichung der Schätzung zwischen 2,27 m und 3,56 m. Modelle mit einer Grundwasserneubildung kleiner 11,85 mm/a und größer 60 mm/a zeigten keine Konvergenz und führten somit zu keinem Ergebnis. Modelle mit kf Werten zwischen 1.1-3 und 1.1-4 m/s für Aquifere und zwischen 1.1-7 und 1.1-8 m/s für Grundwasserstauer konvergierten. Die Grundwasserneubildung betrug etwa 2,17∙10¹⁰ m³/a, für die Bewässerung von Gewächshäusern deckt diese Summe nur 1,75% des gesamten Gebietes ab. Allerdings könnte dieser Wert durch die Nutzung des Grundwasserzuflusses aus Saudi Arabien auf 8 – 9% gesteigert werden.:List of Content Page Dedication ………………………………..………………..2 Acknowledgment ………………………………..………………..3 List of contents …………………………………..……………..4 List of Figures ………..……………………………..….......…8 List of Tables ………..……………………………….…….…9 List of abbreviations ………..……………………………….………10 English Abstract ……………………………………….………..12 German Abstract ..………………...…………………….……….14 1 Introduction ………..……………………………….………16 1-1 Preface ………..……………………………….………16 1-2 Region of interest ………..……………………………….………16 1-3 Previous Studies ………..……………………………….………17 1-3-1 Local studies ………..……………………………….………17 1-3-1-1 Hydrogeological Studies ………..………………………….…….17 1-3-1-2 Remote Sensing Studies ………..………………………….…….18 1-3-2 Global studies …..……………………………….…….18 1-3-2-1 Groundwater flow and fracture zone ..………………………...19 1-3-2-2 Lineaments extraction ………..…………………………….….19 1-3-2-3 Watershed delineation ………..……………………….……….20 1-4 Importance of investigation area ……………..………………..…24 1-5 Motivation ………..……………………………….…….…24 1-6 Deliverables ………..……………………………….………24 1-7 Problems ………..……………………………….………26 2 Methodology ………..……………………………….………27 2-1 Literature review ………..……………………………….………27 2-2 Personal contact ………..……………………………….………27 2-3 Field work ………..……………………………….………27 2-4 Evaluation of geological data ………………………….………27 2-4-1 Geological cross section ….……..……………………….27 2-4-2 Fault system by means of remote sensing techniques …..………28 2-5 Climate and Meteorology..…..………………………………....……28 2-5-1 Meteorological data ………..……………………………….………28 2-5-2 Aridity index ………..……………………………….………28 2-5-3 Groundwater recharge ………..…………………………….….29 2-5-4 Vegetation index ………..……………………………….………29 2-5-5 Actual evaporation ………..……………………………….………30 2-5-6 Soil moisture ………..……………………………….………32 2-5-7 Runoff ………..……………………………….………32 2-6 Hydrogeology ………..……………………………….………34 2-6-1 Pumping test ………..……………………………….………34 2-6-2 Groundwater flow ………..……………………………….………34 2-6-3 Wadi catchment delineation ……………………………….…34 2-6-3-1 Dataset ………..……………………………….………34 2-6-3-2 Approaches ………..……………………………….………34 2-6-3-3 Software packages ………..……………………………….………35 2-6-4 PC options ………..……………………………….………39 2-6-5 Groundwater Model ………..……………………………….………39 2-6-5-1 Conceptual model ………..……………………………….………40 2-6-5-2 Input ………..……………………………….………41 2-6-5-3 Properties ………..……………………………….………41 2-6-5-4 Boundary conditions ………..……………………………….………41 2-6-5-5 Observation wells ………..……………………………….………42 2-6-5-6 Solver ………..……………………………….………42 2-6-5-7 Calibration ………..……………………………….………42 3 Geological setting ………..……………………………….………44 3-1 Preface ………..……………………………….………44 3-2 Tectonic and structure …………………………………………..…...44 3-3 Stratigraphy ………..……………………………….………46 3-3-1 Tayarat formation ………..……………………………….………47 3-3-2 Umm Er Radhumma formation ………………………………....47 3-3-3 Dammam formation ………..……………………………….………48 3-3-4 Euphrates formation………..…………………………………………48 3-4 Topography and Ubaiydh Wadi …………………………………49 4 Climate and meteorology.…………………………………..………51 4-1 Preface ………..……………………………….………51 4-2 Precipitation ………..……………………………….………51 4-3 Temperature ………..……………………………….………52 4-4 Potential evaporation …………………………………………53 4-5 Relative humidity ………..……………………………….………54 4-6 Wind ………..……………………………….………55 4-7 Sunshine duration ………..……………………………….………56 5 Hydrogeology ………..……………………………….………57 5-1 Preface ………..……………………………….………57 5-2 Tayarat aquifer ………..……………………………….………57 5-2-1 Pressure conditions ………..……………………………….………57 5-2-2 Hydraulic characteristics …………………………………………57 5-2-3 Water quality ………..……………………………….………58 5-3 Um Er Radumma aquifer …………………………………………58 5-3-1 Pressure conditions ………..……………………………….………58 5-3-2 Hydraulic characteristics …………………………………………58 5-3-3 Water quality ………..……………………………….………59 5-4 Dammam aquifer ………..……………………………….………59 5-4-1 Pressure conditions ………..……………………………….………59 5-4-2 Hydraulic characteristics …………………………………………60 5-4-3 Water quality ………..……………………………….………60 6 Result and discussion …………………………………………61 6-1 Topographic contour map …………………………………………61 6-2 Geological cross section …………………………………………62 6-3 Lineaments evaluation …………………………………………65 6-4 Groundwater flow ………..……………………………….………66 6-5 Pumping test evaluation …………………………………………70 6-6 Catchment calculation …………………………………………72 6-7 Water balance and Recharge ……………………………….…76 6-8 Groundwater model ………..……………………………….………78 6.8.1 Model sensitivity ………..……………………………….………80 6.8.2 Groundwater management ……………………………….…83 7 Conclusion and recommendations …………………………………84 7.1 Conclusion ………..……………………………….…….…84 7.2 Recommendations ………..……………………………….…….…85 8 References ………..……………………………….………86 9 Appendixes ………..……………………………….………90 10 Field work Photos ………..……………………………….………115 11 Author CV. ………..……………………………….………116

During the recent summers, Gotland has suffered from drinking water shortage and due to the climate change, the water shortage can possible increase in the future. To find a solution, the Swedish Environmental Research Institute IVL and Region Gotland are going to build a testbed at Storsudret located on the south of Gotland, to investigate different sustainable solutions. One possible solution is to increase the water level in Lake Mjölhatteträsk, located at Storsudret, to increase the water storage. This master thesis has focused on the water balance of the lake to understand whether it is possible to store more water in the lake and how large areas that would be flooded in the event of an increase in the water level. This has been done using a combination of field data sampling with geophysical methods, hydraulic tests, water depth measurements, existing hydrometeorological data from Lantmäteriet and the Geological Survey of Sweden (SGU) and modelling with the tools MIKE SHE and MIKE HYDRO River created by DHI and also GIS. The result of this master thesis showed that there is a very thin soil layer with possibly high clay and silt content to the west of the lake. At the bottom of the lake, a thick clay layer exists which reduces the hydraulic connection between the lake and the surroundings. The potential to store and extract water in the sand layer in the west is therefore small. However, there is potential to produce enough water in the lake to meet the water demand at Storsudret, according to the model created in MIKE SHE. This would require a dam at a suggested location at the outflow with a height of 0.12 m. / Gotland har under de senaste åren lidit utav vattenbrist under somrarna och på grund av klimatförändringarna är det möjligt att vattenbristen kan komma att öka i framtiden. För att hitta en lösning har Svenska Miljöinstitutet (IVL) och region Gotland fått i uppgift att anlägga en testbädd på Storsudret på södra Gotland, där olika hållbara lösningar ska testas. En möjlig lösning är att höja vattennivån i sjön Mjölhatteträsk på Storsudret för att på så vis kunna lagra mer vatten. Den här masteruppsatsen har fokuserat på hur sjöns vattenbalans ser ut för att förstå om det är möjligt att lagra mer vatten i sjön och hur stora områden som skulle bli översvämmade vid en ökning av vattennivån. Detta har gjorts med hjälp av en kombination av fältstudier med geofysiska mätningar, hydrauliska tester, vattendjupmätningar och flödesmätningar tillsammans med digitala databaser från Lantmäteriet och Sveriges Geologiska Undersökning (SGU) samt modellering med verktygen MIKE SHE och MIKE HYDRO River som skapats av DHI och även GIS. Resultatet för den här masteruppsatsen visade att det finns ett mycket tunt jordlager med eventuellt högt ler och silt innehåll väster om sjön. Vid botten av sjön finns ett tjockt lerlager som minskar den hydrauliska förbindelsen mellan sjön och omgivningen. Potentialen att lagra och utvinna vatten i sandlagret i väst är därmed liten. Däremot finns det potential att producera tillräckligt med vatten i sjön för att kunna uppfylla vattenbehovet på Storsudret, enligt modellen skapad i MIKE SHE. Detta skulle innebära en dam vid en föreslagen punkt vid utflödet som har en höjd på 0.12 m.

Due to precipitation poor winters and springs and over-exploitation of groundwater reserves during the summer months as a consequence of tourism, the island of Gotland has experienced fresh water shortages during recent years which has led to harsh restrictions in the use of municipal water. In order to find a solution to the islands fresh water problems, the region of Gotland and the Swedish Environmental Institute (IVL) have initiated a project in which the southernmost part of Gotland, Storsudret, will be used as a test site for new methods of sustainable freshwater storage and extraction methods. A, for Sweden, new method currently being investigated is the use of subsurface dams in order to increase the storage capacity of soil groundwater, thus increasing the possible extractions. Methods for finding suitable sites for subsurface dams has been investigated by Imran Jamali, 2016, and Ludvig Almqvist, 2017. There is however a need in further investigating and developing methods for subsurface dam location. This master thesis has focused on performing on-site data collection and on the use of groundwater flow model to evaluate the possibility of placing a subsurface dam on Storsudret, as steps in a method to localize areas suitable for subsurface dams. On site data was collected through resistivity measurements and water level measurements. This was used as input data for the flow model, MIKE SHE, together with more general GIS-data available. Flow modelling was performed during the period 2015-2018, which included the initially dry years of 2015-16 and the summer of 2017, and the more precipitation rich second half of 2017 and spring of 2018. Subsurface dams were modelled to investigate the results on the surroundings. The result did not show any obvious locations for the placement of a subsurface dam within the modelled area. The site considered to be most suitable for dam placement was modelled but showed only a rather small additional stored volume. However, the model result indicated that large possibilities for freshwater extraction already could be present in an existing geological formation in the area, even without the presence of a subsurface dam. As a tool for finding the specific location of groundwater dams, it was concluded that MIKE SHE gives a good overview over the general hydrogeological features and flow paths. Thus, it is a valuable tool when it comes to finding interesting sites for further investigations. However, due to problems in obtaining detailed enough input data, the model is considered to be less suitable for finding specific locations for dam placement when investigating a larger domain. / På grund av nederbördsfattiga vintrar och ett överuttag från grundvattenreservoarerna under turistsäsongen på somrarna, har Gotland erfarit vattenbrist under senare år vilket lett till hårda bevattningsförbud för såväl kommunalt och enskilt vatten. För att hitta en lösning på denna vattenbrist har Region Gotland och Svenska Miljöinstitutet (IVL) initierat ett projekt på den södra delen av Gotland, Storsudret, som kommer att användas som en testplats för nya lösningar inom lagring och uttag av färskvatten. En, för Sverige, ny metod som för nuvarande undersöks är användandet av grundvattendammar som ett sätt att öka lagringskapaciteten i marken och på så sätt kunna öka uttagen av grundvatten. Metoder för att finna lämpliga platser för grundvattendammar har undersökts av Imran Jamali, 2016, och Ludvig Almqvist, 2017. Därtill finns ett behov av att vidare undersöka och utveckla metoder för lokalisering av grundvattendammar. Denna masteruppsats har fokuserat på att utföra data-inhämtning i fält och bygga upp en grundvattenflödesmodell för att utvärdera möjligheten att placera en grundvattendam på Storsudret, som ett vidare steg i att utveckla en metod för att finna lämpliga platser för grundvattendammar. Data från fältundersökningar hämtades genom resistivitetsmätningar och vattenståndsmätningar. Dessa data användes som inmatning i grundvattenflödesmodellen, MIKE SHE, tillsammans med mer generell GIS-data. Flödesmodellering utfördes under perioden 2015-2018, vilket inkluderade torrår under perioden 2015-2016 och slutet av sommaren 2017 och mer nederbördsrik period under hösten 2017 och våren 2018. Grundvattendammar modellerades för att undersöka områdespåverkan. Resultaten visade på ingen självklar lokalisering för en grundvattendamm inom det modellerade området, på grund av platt geologi utan tydliga utflödespunkter blev resultatet av en damm endast en liten ökad grundvattenvolym. Däremot visade modellresultaten att stora uttagsmöjligheter för grundvatten redan fanns i existerande geologiska formationer även utan en grundvattendamm närvarande. Som ett steg i metoden att finna lämpliga platser för grundvattendammar var MIKE SHE ett bra verktyg för att ge en god överblick över de generella hydrogeologiska flödena. MIKE SHE är ett värdefullt verktyg när det kommer till att hitta intressanta platser för vidare undersökningar. Däremot fanns problem med att finna detaljerade inmatningsdata vilket gör modellen mindre lämplig för att finna exakta grundvattendamsplaceringar inom ett större område.

Die genaue Kenntnis über den Wasserhaushalt stellt die Grundlage für die Bewirtschaftung der Ressource Wasser dar. Im urbanen Raum spielen dabei die siedlungshydrologischen Randbedingungen, wie Versiegelung, Anschlussgrad an die Kanalisation oder wasserbauliche Eingriffe, eine nicht zu vernachlässigende Rolle. Zur Quantifizierung der verschiedenen Wasserhaushaltsgrößen wurde ein konzeptioneller Ansatz entwickelt, der die jeweiligen Randbedingungen berücksichtigt und deren gegenseitige Beeinflussung abbildet. Hierbei muss der Einfluss auf den Wasserhaushalt auch bei veränderten Bedingungen simulierbar sein. Als Untersuchungsgebiet wurde das Gebiet der Wuhle, ein rechter Nebenfluss der Spree, gewählt, da es alle relevanten Aspekte der Wasserwirtschaft beinhaltet. Die Wuhle entspringt auf der Barnim-Grundmoränenhochfläche bei Ahrensfelde und mündet nach etwa 15,7 km Lauflänge im Stadtteil Köpenick in die Spree. Der Ansatz beruht auf der Berechnung der Wasserhaushaltsgrößen mit Hilfe eines flächendifferenzierten Verfahrens zur Ermittlung des Gesamtabflusses aus Niederschlag abzüglich der Verdunstung sowie dessen Aufteilung in einen oberirdischen und einen unterirdischen Teil. Zur Verifizierung der wasserhaushaltlich bestimmten Abflussgrößen wurden detaillierte hydraulische Untersuchungen an der Wuhle durchgeführt und abschnittsweise interpretiert. Anschließend wurde mit Hilfe der Förderdaten der Wasserwerke eine Grundwasserhaushaltsbilanz durchgeführt. Im Ergebnis ließ sich hydrogeologisch der Anteil an Uferfiltrat an der Gesamtfördermenge ermitteln. Zur Simulation des Einflusses des Wasserhaushaltes und der Grundwassernutzung auf den Grundwasserkörper wurde mit Hilfe des Simulators FEFLOW© eine numerische Modellierung der Strömungsverhältnisse durchgeführt. Über den Abgleich der simulierten Grundwasserhöhen mit den Grundwasserständen aus der Stichtagsmessung erfolgte eine zusätzliche Überprüfung der wasserhaushaltlich berechneten Abflussgrößen. / The exact knowledge of the water balance is the basis of the water supply and distribution within a catchment area. In an urban area the boundary conditions of the civil engineering like the sewer system or the hydraulic engineering plays an important role. To quantify the water balance a conceptual approach was developed which takes the current conditions and their interdependence into consideration. The impact of changing conditions on the water balance can also be simulated. As investigation area the catchment of the Wuhle River was chosen because it includes all relevant aspects of water management. The Wuhle River has its source on the ground moraine of the Barnim plateau directly at the city boundary in Ahrensfelde and reaches the Spree in the quarter Köpenick after about 15.7 km. This method uses a differentiated calculation by area to determine the total outflow of rainfall minus evaporization. It also determines the submontane and aboveground distribution. For verification purposes detailed hydraulic investigations were carried out at the Wuhle. With the production rate of the waterworks the groundwater balance was then calculated. As a result the amount of bank filtrate of the total groundwater withdrawal was determined in a hydro geological way. Using the simulation software FEFLOW© a numeric model of the flow pattern was created to simulate the influence on the water balance and the groundwater. The displayed subterranean catchment area of the water work Wuhlheide was based on the water table contours which were interpolated from a fixed date measurement of the groundwater heads. By comparing the simulated groundwater heads and the water levels from the fixed date measurement an additional verification of the water balance was realised.

Poly- och perfluorerade alkylsubstanser (PFAS) är samlingsnamnet för en stor grupp kemikalier som det senaste årtiondet tilldelats världsomfattande uppmärksamhet med anledning av frekventa förekomster i vattenmiljö, djurliv och människor. Samtliga PFAS som uppträder i miljön är antropogena och har blivit industriellt framtagna och tillämpade i över 60 år. På grund av deras fysiska och kemiska stabilitet och ytaktiva egenskaper är PFAS eftertraktade inom en rad olika industriella och kommersiella produkter, från filmbildande brandskum till vatten-, smuts- och fettavvisande ytbeläggningar. De omfattande möjligheterna för användning har resulterat i utsläpp av PFAS i miljön, antingen av direkta källor (~80 %) som tillverkning och tillämpning av PFAS-innehållande produkter, eller indirekta källor (~20 %) som nedbrytning och transport av prekursorer. Åtgärder har därför tagits på nationell, regional och global nivå för att begränsa användningen och spridningen av selekterade PFAS-ämnen. En av de mest uppmärksammade föroreningsproblemen med PFAS i Sverige är utsläppen av filmbildande brandsläckningsskum (AFFF) från brandövningsplatser. Som en konsekvens av flera decenniers användning och okontrollerat utsläpp till miljön har koncentrationerna av PFAS uppmätts att vara som högst i anslutning till övningsplatserna. Ämnenas mobilitet och höga vattenlöslighet gör att risken för transport till kringliggande områden är stor, vilket ökar risken att förorena närliggande grundvattentäkter. Flera exempel på PFAS-haltigt dricksvatten i svenska hushåll har bland annat upptäckts i kommuner såsom Uppsala, Ronneby, Halmstad, Botkyrka. Två före detta brandövningsplatser i Bodens kommun har brukat AFFF i övningssyfte i samband med brandövningar då platserna var aktiva. NIRAS Sweden AB har på uppdrag av Försvarsmaktens miljöprövningsenhet utrett området med avseende på PFAS och konstaterade förhöjda nivåer av ämnena i grundvattenmiljö. Eftersom flera ytvattenförekomster gränsar till brandövningsområdet finns det en oro för ämnenas spridningsbenägenhet och potential att påverka närmsta dricksvattentäkt. Syftet med examensarbetet har av den anledningen varit att kartlägga spridningen av PFAS i grundvatten från de två före detta brandövningsstationerna i Boden. Tillvägagångssättet har gått ut på att upprätta en grundvattenmodell i modelleringsprogrammet Visual MODFLOW Classic. Den hydrogeologiska modellen har tillämpats för att utföra föroreningstransport med hjälp av insticksmodulerna MODPATH och MT3DMS. Transport av det mest framträdande PFAS-ämnet i området, PFOS, modellerades från båda brandövningsplatserna och föroreningsplymens utveckling har visualiserats i flera tidssteg. Resultatet från grundvattenmodelleringen visade att grundvattnet från brandövningsområdena i det övre grundvattenmagasinet rör sig i nordvästlig till nordöstlig riktning, men även mot Luleälven. I det undre grundvattenmagasinet rör sig vattnet i nordvästlig, men har också tendens att röra sig mot Luleälven. Föroreningstransporten visade att PFOS har benägenhet att röra sig mot Luleälven i en sydvästlig riktning. Transporttiden av PFOS från brandövningsplatserna till Luleälven beräknades med MODPATH till sex respektive 7 år för den kalibrerade modellen och område 13/24. Visualisering av PFOS-plymen med MT3DMS visade att det tar cirka 100 år för ämnena att nå Luleälven. / Poly- and perfluoroalkyl substances (PFASs) is the collective name for a large group of organic chemicals which in the past decade have gained global attention due to their frequent occurence within the aquatic environment, wildlife and humans. All PFAS that occur in the environment are man-made and have been industrially created and used for over 60 years. Due to their physical and chemical stability and surface active attributes, PFAS are coveted within an array of industrial and commercial products, such as film-forming fire foam to water, dirt and grease-repellent coatings. The many possibilities to use PFAS have led to environmental emissions, either through direct sources (~80%) like manufacturing and application of PFAS-containing products, or indirect sources (~20%), through decomposition and transport of precursors. Within the PFAS-family, perfluoroctanesulfonat (PFOS) and perfluoroctaneacid (PFOA) are the most well-known and studied chemicals which have gained particular attention due to their persistence and high frequency in the environment, in turn leading them to be easily detected in humans and animals globally. PFOS and PFOA have further shown bioaccumulative and toxic traits and have thus increased the regulatory interest in the chemicals in questions of environmental and human health. Measures have therefore been taken on national, regional and global levels to restrict the use and dispersion of selected PFAS-substances affiliated with negative effects. One of the contamination issues to have gained most attention in Sweden is the emission of film-forming fire foam from fire drill locations. The PFAS-containing foam has been used throughout the country for practicing extinguishing fires related to class B: liquid fires, and has been predominantly used by military, airports and industries. As a consequence from the multi decennial use and uncontrolled emissions, the PFAS concentration, mainly PFOS and PFOA, has been measured to be highest in connection with the exercise sites. The substances mobility and high water solubility has increased the risk for their transportation to nearby areas and they may through rainfall infiltrate the ground to potentially reach the groundwater where they risk contaminating nearby groundwater sources. In Sweden, contaminated PFAS-areas are a particularly debatable issue, as about 50% of Swedish drinking water comes from groundwater-related water sources and for that reason, they have increased the general concern for human exposure. Several examples of PFAS-rich drinking water in Swedish households have been found in municipalities as Botkyrka, Halmstad, Ronneby and Uppsala and have in some cases been so high that related water resources have been withdrawn. Even if the intake of drinking water containing large quantities of PFAS substances is not considered to give rise to acute health effects, awareness of the long-term effects of exposure to PFAS is still very limited. A number of experimental and epidemiological studies focusing on PFOS and PFOA, on the other hand, have documented that both high and low doses of the substances can cause a number of adverse health effects. More recently, regulations on legislation for PFAS have reduced the scope of application, preferably for PFOS, but in accordance with this, products such as PFOS-containing fire foams have been substituted with other PFAS which have continued to be used at fire drill locations in Sweden. Continuous emissions of PFAS at these sites are thus still an up-to-date and forthcoming issue, as the substances - together with already existing pollutants - will remain for a long time to come. There are therefore reasons to limit the use further, but due to the lack of data for most PFAS pollutants, there is currently no benchmark value issued by the EU for PFAS other than PFOS. However, the National Food Agency has issued limit values based on the presence of 11 PFAS substances (PFBS, PFHxS, 6:2 FTSA, PFBA, PFPeA, PFHxA, PFHpA, PFNA, PFDA, PFOA och PFOS) with an action threshold of 90 ng·L-1and a health-based limit value for 900 ng·L-1. The values ​​should give an indication that levels of PFAS which are larger in scope than the recommendation are too high and that measures should be taken to minimize the risk of spreading and unhealthy exposure to humans. For this reason, fire drill locations using fire-containing foam containing PFAS in Sweden are a high priority for mapping PFAS distribution in the country and identifying potential areas that are at risk of being affected by the spread of the pollutants in soil and water. As a result, two closed fire drill locations in Boden municipality - as part of a nationwide survey - have been investigated with regard to the fire extinguishing foam that has historically been used and caused pollution in the area. The PFAS-based fire foam is assumed to have had historical application to two exercise sites that operated between 1940 – 1985 and 1987 – 2005, respectively. In 2016, an environmental technical soil survey was carried out with regard to the presumed PFAS occurrence for the area. The investigation was based on sampling of soil and groundwater at four and eight different points respectively, centered around the two fire drill locations, and the results showed that the current contamination in the area was clearly noticeable and that the levels were higher than the Swedish Food Agency's recommended action threshold. Findings of PFOS that exceeded SGI's preliminary target value in groundwater (45 ng·L-1) and in soil (10 µg/kgTS) were also measured in connection with the two fire drill sites, which increased the interest in broadening the mapping of the current pollution situation with the aim of creating a better understanding of the extent of the pollution and potential spreading potential. Because the knowledge of the groundwater flow direction is limited, a hydrogeological model over the fire drill location can lead to a better understanding of the groundwater flow direction and thus the possible spreading direction of the present PFAS substances. The model can also be used as a tool for calculating the time required for the potential of the pollutants to affect the nearest protection object and thereby estimate and prevent the risks for human exposure in the area at the conceivable start of construction work in the now discontinued area. The results from the groundwater modelling showed that the groundwater from the fire drill areas in the upper groundwater reservoir moves in a northwesterly to northeasterly direction, but also towards the Lule River. In the lower groundwater reservoir, the water moves to the northwest and towards the Lule River. The contamination transport showed that PFOS tends to move toward the Lule River in a southwesterly direction. The transport time of PFOS from the fire training sites to the Lule River was estimated with MODPATH to 6 and 7 years respectively for the calibrated model and area 13/24. Visualization of the PFOS plume with MT3DMS showed that it takes about 100 years for the substances to reach the Lule River.

This thesis aimed to evaluate the groundwater discharge distribution in the Krycklan catchment by developing a groundwater flow model using COMSOL Multiphysics and assuming a topography- controlled groundwater surface. Previous research has shown that the groundwater surface can be modeled as a subdued replica of the topography in humid climate regions where the permeability of the subsurface is low and where the groundwater surface is shallow. In earlier studies by Mojarrad (2021), it has been shown that the modeled infiltration becomes higher than the observed infiltration when a topography-controlled groundwater surface boundary is used and that a solution to this is to decrease the resolution in recharge areas. This method was therefore used in the thesis; however, the modeled infiltration was unsuccessfully lowered. This is thought to be due to differences between the model and the previous study and which are discussed further in this thesis. The discharge and recharge areas were identified using the direction of the vertical component of Darcy velocity, and the discharge flow distribution was evaluated in ArcMAP. The discharge flow distribution in the landscape was compared to real geographical data of surface water to identify a discharge threshold value for when the water balance is upheld by surface water flow or by evapotranspiration. The evapotranspiration discharge flow distribution was also evaluated, where the highest flow values were found in riparian zones of the landscape. / Syftet med denna avhandling var att utvärdera föredelningen av grundvattnets utflöde i Krycklans avrinningsområde genom att utveckla en grundvattenflödesmodell i COMSOL Multiphysics med antagandet av en topografikontrollerad grundvattenyta. Tidigare forskning har visat att grundvattenytan kan modelleras som en dämpad kopia av topografin i fuktiga klimatområden där permeabiliteten i underytan är låg och där grundvattenytan är grund. En implikation av att använda en topografikontrollerad grundvattenyta har visat sig vara att den modellerade infiltrationen blir högre jämfört med den observerade infiltrationen. Tidigare studier av Krycklans avrinningsområde har visat att genom att minska upplösningen i infiltrationsområden kan den modellerade infiltrationen framgångsrikt sänkas, därför användes denna mesh-utjämningsmetod i avhandlingen. För validering av modellen jämfördes den modellerade infiltrationen med den observerade infiltrationen i Krycklans avrinningsområde. Valideringen visade att mesh-utjämningen misslyckades med att minska infiltrationen, vilket tros bero på skillnader mellan modellen och den tidigare studien och som diskuteras vidare i denna avhandling. Grundvattnets infiltration- och utflödesområden identifierades med hjälp av riktningen på den vertikala komponenten av Darcy-hastighet, och utflödesfördelningen utvärderades i ArcMAP. Utflödesfördelningen i landskapet jämfördes med verkliga geografiska data för ytvatten för att identifiera ett tröskelvärde för utflödet när vattenbalansen upprätthålls av ytvattenflöde eller av evapotranspiration. Fördelningen av utflöden genom evapotranspirations utvärderades också, där de högsta flödesvärdena återfanns i områden nära ytvattenkroppar i landskapet.

Das Ziel der vorliegenden Arbeit ist die ausführliche Analyse und Beschreibung langfristiger abiotischer Standortbedingungen von Fluss und Grundwasser für das in einem Hartholzauenwald gelegene Untersuchungsgebiet im Naturschutzgebiet Saalberghau an der Mittleren Elbe bei Dessau. Hierzu erfolgt zunächst die Entwicklung eines allgemeinen Konzeptes, dass die Modellierung des Fluss- und des Grundwasserregimes sowie die statistische Auswertung dieser miteinander verbundenen Regime umfasst. Es wird davon ausgegangen, dass nur eine Synthese dieser Einzelbausteine die Grundlage für eine zusammenhängende Analyse und Beschreibung der komplexen auentypischen Dynamik dieser beiden Regime anhand objektivierbarer statistischer Parameter bilden kann. Darüberhinaus stellt die Zielsetzung auf langfristige Aussagen eine unentbehrliche Voraussetzung dar, um das Zeitspektrum der hier zu betrachtenden Altbäume typischer Hartholzauenbaumarten adäquat berücksichtigen zu können. / The present dissertation aims at a detailed analysis and description of the long-term abiotic site conditions (river flow and groundwater) for the floodplain area under investigation, namely a hardwood forest in the nature reserve &amp;quot;Saalberghau&amp;quot; on the Middle Elbe close to the town Dessau. For this purpose, firstly a general concept which covers the modelling of the surface water and groundwater regime as well as a statistical interpretation of these two interconnected regimes is developed. It is assumed that only a synthesis of those separate modules can form a sufficient basis for a cohering analysis and description of the complex dynamics of these two regimes in floodplain forests by means of objective statistic parameters. Furthermore, only longterm statements can take into account the age spectrum of the hardwood stand.