This study evaluated the impacts of shallow and deep open drains on groundwater levels and drain performance under varying climate scenarios and irrigation application rates. The MIKE SHE model used for this study is an advanced and fully spatially distributed hydrological model. Three drain depths, climates and irrigation application rates were considered. The drains depths included 0, 1 and 2 m deep drains. The annual rainfall and meteorological data were collected from study area from 1976 to 2004 and analysed to identify the typical wet, average and dry years within the record. Similarly three irrigation application rates included 0, 10 and 16 ML/ha-annum. All together twenty seven scenarios (3 drains depths, 3 climates and 3 irrigation application rates) were simulated. The observed soil physical and hydrological data were used to calibrate and validate the model. Mean square error (R[superscript]2) of the simulated and observed water table data varied from 0.7 to 0.87. Once validated the MIKE SHE model was used to evaluate the effectiveness of 1 and 2 metre deep drains. The simulated water table depth, unsaturated zone deficit, exchange between unsaturated and saturated zones, drain outflow and overland flow were used to analyse their performance. The modeling results showed that the waterlogging was extensive and prolonged during winter months under the no drainage and no irrigation scenario. In the wet climate scenario, the duration of water logging was longer than in the average climate scenario during the winter months. In the dry climate scenario no waterlogging occurred during the high rainfall period. The water table reached soil surface during the winter season in the case of wet and average climate. For the dry climate, the water table was about 0.9 metres below soil surface during winter. / One and 2 metre deep drains lowered the water table up to 0.9 and 1.8 metres in winter for the wet climate when there was no irrigation application. One metre deep drains proved effective in controlling water table during wet and average climate without application of irrigation water. One metre deep drains were more effective in controlling waterlogging a in wet, average and dry years when the irrigation application rate was 10 ML/ha-annum. With 16 ML/ha-annum irrigation application, 1 metre deep drains did not perform as efficiently as 2 metre deep drains in controlling the water table and waterlogging. In the dry climate scenario, without irrigation application, 1 metre deep drains were not required as there was not enough flux from rainfall and irrigation to raise the water table and create waterlogging risks. Two metre deep drains lowered the water table to greater depths in the wet, average and dry climate scenarios respectively when no irrigation was applied. They managed water table better in wet and average climate with 10 and 16 ML/ha-annum irrigation application rate. Again in the dry climate, without irrigation application 2 metre deep drains were not required as there was a minimal risk of waterlogging. The recharge to the groundwater table in the no drainage case was far greater than for the 1 and 2 metre deep drainage scenarios. The recharge was higher in case of 1 metre deep drains than 2 metre deep drains in wet and average climate during winter season. / There was no recharge to ground water with 1 and 2 metre deep drains under the dry climate scenarios and summer season without irrigation application as there was not enough water to move from the ground surface to the unsaturated and saturated zones. When 10 ML/ha-annum irrigation rate was applied during wet, average and dry climate respectively, 1 metre deep drains proved enough drainage to manage the recharge into the groundwater table with a dry climate. For the wet and average climate scenarios, given a 10 ML/ha-annum irrigation application rate, 2 metre deep drains managed recharge better than 1 metre deep drains. Two metres deep drains with a 10 ML/ha-annum irrigation application rate led to excessive drainage of water from the saturated zone in the dry climate scenario. Two metres deep drains managed recharge better with a 16 ML/ha-annum irrigation application rate in the wet and average climate scenarios than the 1 metre deep drains. Two metres deep drains again led to excessive drainage of water from the saturated zone in dry climate. In brief, 1 metre deep drains performed efficiently in the wet and average climate scenarios with and without a 10 ML/ha-annum irrigation application rate. One metre deep drains are not required for the dry climate scenario. Two metre deep drains performed efficiently in the wet and average climate scenarios with 16 ML/ha-annum irrigation application rate. Two metre deep drains are not required for the dry climate scenario.

Groundwater is a sensitive component affected by climate change. Modelling the dynamics of groundwater levels is inherently difficult particularly as the response to climate change. Given this complexity, most of the current studies using long term groundwater time series were conducted by statistical analysis or using over simplified assumptions to represent the physical processes in hydrological system. With the objective of providing an improved physically based groundwater modelling approach to support climate change impact assessment, a dataset of long term time series of groundwater levels from two different soil types (sand and till) were selected from the Tärnsjö area located in southeast of Sweden. The CoupModel was chosen to perform the simulation since it offers a physically based representation on groundwater recharge processes. A two-step strategy for calibration with first short-term calibration followed by long-term testing was adopted. Simulated groundwater levels followed the general patterns of measured groundwater level dynamics; however, auto-correlations and periodicities were observed in residuals for all sites of which two sandy soil sites with deeper groundwater tables maintained strong auto-correlations in long time lags and an extra 15.4-year periodicity. The long memory of the system rendered it more susceptible to climate change. Uncertainty arises if different initial condition had been applied in short term period calibration.

<p>Available observations are often not sufficient as a basis for decision making in water management. Conceptual runoff models are frequently used as tools for a wide range of tasks to compensate the lack of measurements, e.g., to extend runoff series, compute design floods and predict the leakage of nutrients or the effects of a climatic change. Conceptual runoff models are practical tools, especially if the reliability in their predictions can be assessed. Testing of these models is usually based solely on comparison of simulated and observed runoff, although most models also simulate other fluxes and states. Such tests do not allow thorough assessment ofmodel-prediction reliability. In this thesis, two widespread conceptual models, the HBV modeland TOPMODEL, were tested using a catalogue of methods for model validation (defined as estimation of confidence in model simulations). The worth of multi-criteria validation forevaluating model consistency was emphasised. Both models were capable to simulate runoffadequately after calibration, whereas the performance for some of the other validation tests wasless satisfactory. The impossibility to identify unique parameter values caused large uncertainties in model predictions for the HBV model. The parameter uncertainty was reducedwhen groundwater levels were included into the calibration, whereas groundwater-levelsimulations were in weak agreement with observations when the model was calibrated againstonly runoff. The agreement of TOP-MODEL simulations with spatially distributed data was weak for both groundwater levels and the distribution of saturated areas. Furthermore, validation against hydrological common sense revealed weaknesses in the TOPMODEL approach. In summary these results indicated limitations of conceptual runoff models and highlighted the need for powarful validation methods. The use of such methods enables assessment of the reliability of model predictions. It also supports the further development of models by identification of weak parts and evalution of improvements.</p>

Available observations are often not sufficient as a basis for decision making in water management. Conceptual runoff models are frequently used as tools for a wide range of tasks to compensate the lack of measurements, e.g., to extend runoff series, compute design floods and predict the leakage of nutrients or the effects of a climatic change. Conceptual runoff models are practical tools, especially if the reliability in their predictions can be assessed. Testing of these models is usually based solely on comparison of simulated and observed runoff, although most models also simulate other fluxes and states. Such tests do not allow thorough assessment ofmodel-prediction reliability. In this thesis, two widespread conceptual models, the HBV modeland TOPMODEL, were tested using a catalogue of methods for model validation (defined as estimation of confidence in model simulations). The worth of multi-criteria validation forevaluating model consistency was emphasised. Both models were capable to simulate runoffadequately after calibration, whereas the performance for some of the other validation tests wasless satisfactory. The impossibility to identify unique parameter values caused large uncertainties in model predictions for the HBV model. The parameter uncertainty was reducedwhen groundwater levels were included into the calibration, whereas groundwater-levelsimulations were in weak agreement with observations when the model was calibrated againstonly runoff. The agreement of TOP-MODEL simulations with spatially distributed data was weak for both groundwater levels and the distribution of saturated areas. Furthermore, validation against hydrological common sense revealed weaknesses in the TOPMODEL approach. In summary these results indicated limitations of conceptual runoff models and highlighted the need for powarful validation methods. The use of such methods enables assessment of the reliability of model predictions. It also supports the further development of models by identification of weak parts and evalution of improvements.

The Geological Survey of Sweden (SGU) has initiated a project to calibrate models to simulategroundwater levels in monitoring wells of their Groundwater Network, based on a commission fromthe Swedish Government after experiencing historically low groundwater levels and shortage in 2016and 2017. A version of the HBV model with 4 parameters, focusing on calculating groundwaterrecharge and levels, was manually calibrated to 119 groundwater stations in 2017 and the modelresults were classified according to a ‘good’, ‘poor’ or ‘bad’ visual fit to observations. In this thesis,the process-based model CoupModel, which allows the user to freely setup a model structure, wasused to simulate groundwater levels. The objectives of this thesis were to evaluate the usability of theCoupModel in groundwater level simulations and forecasting, and compare the results to previoussimulations using the HBV model. 22 groundwater stations of fast and slow responding aquifers, distributed all over Sweden, wereused to simulate groundwater levels with the CoupModel. A model structure with 11 parameters tocalibrate was constructed to represent all groundwater stations. A split-sample test was performed withcalibration of 10,000 Monte Carlo simulations and validation of the 10 simulations with the highestNash-Sutcliffe efficiency (NSE). The NSE performance was highest, and consistent through calibration and validation, for fastresponding aquifers using the CoupModel, whereas the performance of slow responding aquifers waslower. Residual analysis showed periodicity with under- and overestimations for low and highgroundwater levels, respectively, indicating that the model structure is not sufficient in representing allgroundwater stations. No relationship existed between CoupModel performance and HBV calibrationperformance, topographic position, aquifer type, location or distance to climate station. The HBVperformance was lower than for the CoupModel, with residuals of larger spread and periodicity. The CoupModel can be used for simulation and forecasting of groundwater levels, but a newmodel structure or individual structures for all groundwater stations must be constructed. A sensitivityanalysis of the parameters in the model structure must be performed to study the systematic under- andoverestimations. / Grundvatten har en stor betydelse för att upprätthålla ekosystem och försörja människor meddricksvatten, där grundvattentillgång och nivåer beror av bland annat nederbörd, temperatur,snösmältning, växtupptag och antropogen påverkan på jord och mark. Förändringar i temperatur- ochnederbördsmönster på grund av klimatförändringar och en större vattenförbrukning påverkargrundvattennivåernas variationer inom och mellan år. Den här studien syftar till att undersöka hur ochi vilken uträckning den konceptuella modellen CoupModel kan användas för simulering ochprognostisering av grundvattennivåer, samt hur den står sig i relation till en annan, tidigare studeradmodell (HBV-modellen). Studiens relevans uppdagades hos Sveriges geologiska undersökning (SGU)i samband med historiskt låga grundvattennivåer under 2016-2017, genom initiering av ett projekt medmålet att kalibrera grundvattenmodeller till mätstationer i SGUs grundvattennät. Appliceringen avmodeller har stor samhällsnytta då förebyggande av och åtgärder mot låga grundvattennivåer kanplaneras och vidtas utifrån väderprognoser och klimatscenarier. En modellstruktur skapades i CoupModel och användes för att simulera grundvattennivåer i 22grundvattenstationer av olika karaktär och modellen kalibrerades och validerades mot observationer avgrundvattennivå. Resultatet av studien visade att CoupModel kan användas som verktyg försimulering och prognostisering av grundvattennivåer, men att modellstrukturen som användes behöverutvecklas. Systematisk över- och underestimering av observerade nivåer förkommer hos allasimuleringar och ingen relation kunde ses mellan modellens prestation och plats eller typ avgrundvattenstation. CoupModel presterade i de flesta fall bättre än HBV-modellen, men kräversamtidigt mer information om en grundvattenstations jordprofil och fler parametrar att kalibrera.

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Uppsatsens syfte är att undersöka om kommuner i Mälarregionen drabbades av låga yt- och grundvattennivåer under sommaren 2017, hur situationen hanterades, deras dagliga arbete med vattenfrågor och om handlingsplaner fanns för låga nivåer före 2017. Vi vill även se hur kommunerna ställer sig till klimatförändringar samt sammanställa vilka roller och ansvar som olika myndigheter har när det kommer till vattenförsörjning. Arbetets undersökningsområde begränsades till 39 kommuner i fyra län: Södermanlands, Upplands, Västmanlands och Örebro län. För att besvara syftet skickades en enkät ut till kommunerna och intervjuer genomfördes med två av kommunerna. En litteraturstudie genomfördes för att kunna besvara ansvarsfördelningen mellan olika myndigheter. Enkäten besvarades av 26 kommuner. Det viktigaste resultat var att kommunerna, trots vattennivåer under det normala, inte upplevde vattenbrist i den omfattningen som vi trott. Fem kommuner angav att de drabbades av vattenbrist. Den huvudsakliga åtgärden som infördes var bevattningsförbud. Från enkäten framkom att det i stor utsträckning saknats handlingsplaner för att hantera en situation med vattenbrist innan 2017. Majoriteten av kommunerna tror att deras vattenförsörjning kan påverkas av klimatförändringar, men bara 14 angav att de har en handlingsplan för det. Resultatet som framkom från intervjuerna gällde främst processen för införandet av skyddsområden. Även i litteraturstudien framkom det att arbetet med vattenskyddsområden inte går i den takt som är nödvändig för att nå målen förhållbar och långsiktig dricksvattenförsörjning. / The aim of this paper is to examine how municipalities in the Mälar region of Sweden were affected by the low surface and groundwater levels in the summer of 2017, how municipalities handled the situation, how they work with water related questions in their daily work and whether they had an action plan for dealing with shortage of water prior to 2017. Lastly, we also aim to compile the roles and responsibilities for different authorities when it comes to water supply. The area of study was limited to 39 municipalities in four counties: Södermanlands, Upplands, Västmanlands and Örebro county. To answer the aim, a survey was sent out to all municipalities and interviews were done with two of the municipalities. A literature study was done in order to answer the division of responsibilities between different authorities. The survey was answered by 26 municipalities. The main result we got from the survey was that even though the water levels were below normal, the municipalities didn’t experience water shortages in the extent we had expected. Five municipalities indicated that they had been affected by the water shortages. The main measure that were done was the irrigation ban. From the survey it was found that most of the municipalities were lacking action plans to deal with a water shortage situation before2017. The majority of the municipalities believe that their water supply can be affected by climate change, but only 14 indicated that they have an action plan for it. The results obtained from our interviews primarily marks the division of responsibilities for water conservation areas. As conducted from the literature study, the processes to constitute water conservation areas does not seem to be smooth and quick enough to meet the goals of sustainable and long-term water supply.

Lidköpings kommun i Västra Götalands län tar ut en del av sitt råvatten till dricksvattenproduktion från grundvattenmagasinet Rådaås. Det görs genom tre olika uttagsbrunnar (Brunn 1, Brunn 2 och Brunn 3) som körs en i taget. På senare tid har kommunen börjat misstänka att salthalterna i uttagsvattnet ökar, och det finns ett intresse för att förstå vad problemet beror på och vad som kan göras åt saken.  Syftet med detta arbete är att undersöka förekomst och ursprung hos saltvattnet i magasinet och att undersöka hur brunnsdrift i samband med grundvattennivåer påverkar halten i uttagsvattnet. Eftersom det sedan tidigare finns misstankar om att det rör sig om relikt saltvatten utgör det en hypotes för detta arbete. Relikt saltvatten är salt grundvatten som avsatts under en tid då området varit täckt av salt hav, till exempel delar av Sverige under Östersjöns utveckling sedan den senaste istiden.   För att undersöka förekomst av saltvatten i magasinet funktionstestades och provtogs samtliga tillgängliga grundvattenrör för kloridhalt. Resultatet visar att kloridhalten ökar med grundvattenrörens djup och att de högsta salthalterna finns i en djuphåla eller ränna i berggrunden strax under Brunn 1 och 2. För att undersöka ursprunget hos det salta grundvattnet provtogs några av grundvattenrören och samtliga uttagsbrunnar för jodid. Med hjälp av jodid-/kloridkvoten kunde det fastställas att saltvattnet är av relikt ursprung.  För att undersöka hur brunnsdrift påverkar salthalten i uttagsvattnet togs start- och slutprover på kloridhalt i början och slutet på varje driftsperiod och brunn under tre månader. Mönstret i kloridhalt jämfördes med grundvattennivåer. Resultatet visar att kloridhalterna i uttagsvattnet ökar under driftsperioden för samtliga brunnar, men återhämtar sig då brunnen är vilande. Generellt är salthalten högst för Brunn 2 och lägst för Brunn 3. Det kan bero på att Brunn 2 ligger sist av de tre brunnarna i grundvattnets strömningsriktning medan Brunn 3 ligger först samt längst bort från rännan i berggrunden.  Resultatet från detta arbete visar också på att grundvattenuttaget ur Rådaåsmagasinet sedan 1990-talet har orsakat en höjning av salthalterna i råvattnet. Rekommendationer som ges till Lidköpings kommun för att minska eller bibehålla nuvarande salthalt är att installera kontinuerlig övervakning av konduktivitet i uttagsbrunnarna och av grundvattennivå i de två rör som ligger brunnarna närmast. Detta för att i realtid kunna följa hur uttagssätt och grundvattennivå påverkar salthalten. En idé är också att strategiskt placera ut en eller flera nya uttagsbrunnar och på så sätt undvika saltansamlingar i djupa jordlager. / Lidköping municipality in Västra Götaland county, Sweden, extracts some of its raw water for drinking water production from Rådaås aquifer. It is done by using three different pumping wells (Well 1, Well 2 and Well 3) which are run one at a time in a cyclic manner. Recently, the municipality personnel have started to suspect that the salinity of the raw water is increasing. They are therefore interested in understanding the cause of the problem and what could be done to mitigate it.  The purpose of this study is to investigate the occurrence and origin of saline groundwater in the Rådaås aquifer and to determine how operation of the pumping wells along with groundwater levels affect the salinity in the raw water. Since there is already a suspicion of the saline water being relict salt water, that is a hypothesis for this study. Relict salt water is saline groundwater deposited during times when an area was covered by marine water, for example some areas of Sweden during the development of the Baltic Sea since the latest ice age.    To investigate the occurrence of saline groundwater in the aquifer, all available piezometers were tested for functionality and sampled to analyse chloride concentration. The results show that the chloride concentration increases with the depth of the piezometer and that the highest concentrations are found in a depression or furrow in the bedrock just below Well 1 and 2. To investigate the origin of the saline groundwater, some of the piezometers and all pumping wells were tested for iodide. Using the iodide/chloride ratio, it was concluded that the salt water is relict. To investigate how operation of the pumping wells affect the salinity of the raw water, samples of chloride concentration were extracted in the beginning and in the end of each pumping period and well during three months. The resulting pattern of chloride concentration was compared to groundwater levels. The results show that the chloride concentrations in the raw water increase during the pumping periods for all wells, but recover when the well is resting. In general, Well 2 shows the highest salinity and Well 3 shows the lowest. The reason may be that of the three, Well 2 is located last in the groundwater flow direction, while Well 3 is located first and is also furthest away from the furrow in the bedrock.    The results of this study also show that groundwater withdrawal from Rådaås aquifer since the 1990’s has caused an increase of salinity in the raw water. Recommendations given to Lidköping municipality to reduce or maintain the salinity of the raw water are to install continuous surveillance of conductivity in the pumping wells and of groundwater levels in the two most adjacent piezometers. This is to enable live monitoring of how operating the pumping wells along with groundwater levels affect the salinity. Another idea is to strategically place one or more new pumping wells to insure that they avoid deep layers of soil where salt water is accumulated.