Over the past several decades, the use of groundwater modelling has been increasing in order to better evaluate the complexities inherent in hydrogeological calculations. Information required for groundwater modelling is for example elevation of soil and bedrock layers, which often is collected by drilling. This is both time consuming and expensive, making it impossible to collect an unlimited number of data points. It is not uncommon that smaller hydrogeological investigations are based on only three or four sample points. To approximate values of unknown points in the study area, the known values of the measured data is interpolated. The interpolation can be done with different methods, and the estimations of the elevation of geological layers at the unknown points might vary with different methods. How the uncertainty of the interpolations then affects the modelling results is generally unknown when simulating groundwater flow. The aim of the thesis work is to investigate how hydrogeological results from groundwater models are affected by choice of interpolation method and by sample size of which the interpolation is based on. The hydrogeological models were simulated within the framework of a Swedish railway project where an unusually large number of probing data was available. The study focuses on two-dimensional, steady-state groundwater flow modelled in the software SEEP/W. Consequently, the objective of the modelling work was to simulate groundwater flow where the difference between the models was how the geometry of the geological layers was defined. The definition of the geometry was done with interpolations of the probing data with different interpolation methods and with interpolation based on different sample sizes. Twelve different interpolation methods in the software Surfer was used to interpolate the total of 357 data points. The interpolations that were estimated to be reliable were then used in the groundwater modelling. Groundwater models were also simulated based on a reduced amount of data in order to investigate the importance of sample size. The total amount of data points was reduced to 50%, 25%, 5% and 1% of the initial sample size before it was interpolated and then used to define the geometry in the groundwater models. The study showed that although the choice of interpolation method and sample size affected the results of the modelled groundwater flow rate, none of the deviations between the model results were larger than what would be considered as acceptable in a hydrogeological context. The models based on at least 90 data points showed good precision while the precision of modelled groundwater flow decreased when sample size decreased. Thus, when interpolating data for groundwater modelling, the sample size should be determined by the required precision of the study. For the modelling of the 1% data, only one of the six models was possible to simulate. This since at least three data points are required for each geological layer in order to perform interpolations, and this was only obtained in one of six randomly selected data sets. The study indicates that around 10-20 sample points is a minimum for a study area with similar conditions as the reference project in order to have a high probability of obtaining enough data of all geological layers of interest. Finally, the study indicates that there are other parameters in groundwater modelling, for example hydraulic conductivity and boundary conditions, that might have an equal of higher impact on the model results. These parameters should therefore also be determined with a high precision in order to gain accurate modelling results. / Under de senaste årtiondena har användandet av grundvattenmodeller ökat för att bättre kunna hantera komplexitet inom hydrogeologiska beräkningar. För att kunna skapa en grundvattenmodell krävs exempelvis data över hur lager av jord och berg är beläget. Dessa geologiska data samlas vanligen i borrpunkter, vilket är både tidskrävande och dyrt. Detta gör det omöjligt att erhålla ett obegränsat antal mätpunkter och det är vanligt att mindre hydrogeologiska undersökningar endast utgår ifrån tre till fyra mätpunkter. Utifrån det begränsade antalet mätpunkter interpoleras kända nivåer av jord- och berglager för att approximera nivåer i okända punkter. Interpolering görs med hjälp av olika matematiska metoder och resultatet av dessa kan variera mellan olika metoder. Hur osäkerheter i interpolering sedan påverkar resultat från grundvattenmodellering är vanligtvis okänt. Syftet med examensarbetet är att undersöka hur hydrogeologiska resultat från grundvattenmodeller påverkas av val av interpolerings metod samt av antal mätpunkter som interpoleringen är baserad på. Grundvattenmodellerna skapades inom ramen av ett svenskt järnvägsprojekt där ovanligt stora mängder sonderingsdata fanns tillgängligt. Undersökningen fokuserar på steady-state grundvattenflöden i två dimensioner, modellerat i programmet SEEP/W. Undersökningen utgick därmed från sonderingsdata i referensprojektet för att skapa ett antal grundvattenmodeller, där skillnaden mellan dessa var hur nivån av de geologiska lagren definierades. Detta gjordes med hjälp av olika interpoleringsmetoder och med interpolering baserad på olika mängder data punkter. Tolv olika interpoleringsmetoder i programmet Surfer användes för att interpolera de totalt 357 data punkterna. De interpoleringar som kunde antas vara rimliga användes sedan för att definiera geometrin i olika grundvattenmodeller. Grundvattenmodeller skapades även utifrån en reducerad mängd data för att undersöka betydelsen av antal mätpunkter vid interpolering. Antal mätpunkter reducerades till 50%, 25%, 5% och 1% och interpolering av dessa användes sedan för att definiera geometrin i olika grundvattenmodeller. Studien visade att även om modeller baserade på olika interpoleringsmetoder och interpolering av olika antal mätpunkter genererade något olika resultat med avseende på modellerat grundvattenflöde, så var inget av resultaten mer avvikande än vad som i ett hydrogeologiskt sammanhang skulle klassas som acceptabelt. Vidare visade resultaten att modeller baserade på 90 data punkter eller mer hade en bra precision av modellerat grundvattenflöde samt att minskat antal mätpunkter ledde till minskad precision. Antal mätpunkter i en undersökning bör därmed väljas utifrån hur bra precision som bör uppnås. Dock kan ett lägre antal mätpunkter försvaras om erhållen precision vägs mot hur resurskrävande insamling av data är. Modelleringen av 1% data visade att endast en av de sex modellerna gick att skapa. Detta var på grund av att minst tre datapunkter för varje geologiskt lager krävdes för att interpolera data och detta uppnåddes alltså bara i en av de slumpade data seten. För att ha en hög sannolikhet att erhålla tillräckligt med data för varje jord- eller berglager av intresse indikerar denna studien på att 10 till 20 mätpunkter är tillräckligt i en undersökning med liknande förutsättningar som i referensprojektet. Slutligen så indikerar studien på att det finns andra parametrar, exempelvis hydraulisk konduktivitet och randvillkor, som kan ha liknande eller större inverkan på modellerat grundvattenflöde och för att få noggranna resultat bör även dessa parametrar bestämmas med hög precision.

When building tunnels in rock, an inflow of groundwater is likely induced. Depending on the hydraulic properties of the rock and the surrounding soils, the inflow may cause a decline in the groundwater level above the tunnel line with possible consequences for nearby well facilities or groundwater dependent environments. Discharge of the inflowing groundwater represents an operation of water (vattenverksamhet in Swedish) according to the Swedish environmental law, meaning that permission must be applied for at the Environmental Court. In the application, the operator presents an area of influence for groundwater, which defines the area where the groundwater levels could change due to the planned operation. In this work, the area of influence has been defined as the area where the groundwater level is lowered by more than five centimeters. As part of the project Tvärförbindelse Södertörn in southern Stockholm, the Swedish Transport Administration is planning for the construction of a tunnel in rock adjacent to Glömstadalen in Huddinge municipality. The aim of this master thesis was to investigate the extension of the area of influence of the tunnel through two-dimensional groundwater modelling. A site-specific model was created in the program SEEP/W by establishing a cross-section orthogonal to the tunnel and through examination of the hydrogeological conditions in the area. Steady-state modelling of both unsaturated and saturated flow was then carried out including and excluding the tunnel. Through this, the change in groundwater levels due to the tunnel could be reviewed. Since the development of the model required simplifications and assumptions of the site-specific conditions, a simple sensitivity analysis was also performed where a few model parameters were altered to examine how the area of influence changed. The modelling results showed that the tunnel, when sealed suitably, at most changed the groundwater levels 680 meters north and 840 meters south along the studied cross-section. The smallest effect on the groundwater levels was observed 400 meters north and 560 meters south of the tunnel. Differences in the extension of the area of influence were noticed depending on how the outflow of groundwater in Glömstadalen was represented, and which sealing properties around the tunnel were used. Furthermore, the modelling showed that the hydraulic conductivity of the rock is of major importance for the location of the groundwater table, and therefore it is considered relevant to perform hydraulic tests in the rock to increase the reliability of the model.

K&uuml / &ccedil / &uuml / k Menderes River Basin located in western Turkey has been facing continuous groundwater level decreases for the past 30 years. In dry periods, irrigation demand is completely met by pumping from groundwater system, which reduces water levels significantly. This provides enough storage to be recharged in wet seasons when streams are running. However, increased runoff in wet season are not utilized neither for irrigation nor for recharge and lost to the Aegean Sea without being infiltrated. Hence, surface artificial recharge methods can be useful to collect excess water in recharge basins, thus allowing infiltration to increase groundwater storage in wet seasons to be later utilized in dry seasons. A 2-D groundwater model is set up by using SEEP/W software. The material functions and parameters used in the model for saturated/ unsaturated conditions are taken from previous studies. Calibration was done to check the accuracy of input data and to control the validity of model. The amount of excess water that will be collected in recharge basins was estimated from flood frequency analysis. Concerning different probabilities, different scenarios were simulated to observe the increase in groundwater levels. Simulation results suggest that significant increase in groundwater storage could be achieved by applying artificial recharge methods. In addition to recharge basins, to reinforce the effect of artificial recharge, simulations were repeated with the addition of an underground dam at downstream side of the basin. Simulation results indicate that the increase in groundwater storage is not sufficient to warrant construction of the underground dam.

The devastating levee failures associated with hurricanes Katrina and Rita, and the more recent Midwest flooding, placed a spotlight on the importance of levees and our dependence on them to protect life and property. In response to levee failures associated with the hurricanes, Congress passed the Water Resources Development Act of 2007 which established a National Committee on Levee Safety. The committee was charged with developing recommendations for a National Levee Safety Program. The Secretary of the Army was charged with the establishment and maintenance of a National Levee Database. The National Levee Database is a critical tool in assessing and improving the safety of the nation's levees. However, the NLD data model, established in 2007, lacked a structure to store seepage and slope stability analyses – vital information for assessing the safety of a levee. In response, the Levee Analyst was developed in 2008 by Dr. Norm Jones and Jeffrey Handy. The Levee Analysis Data Model was designed to provide a central location, compatible with the National Levee Database, for storing large amounts of levee seepage and slope stability analytical data. The original Levee Analyst geoprocessing tools were created to assist users in populating, managing, and analyzing Levee Analyst geodatabase data. In an effort to enhance the Levee Analyst and provide greater accessibility to levee data, this research expanded the Levee Analyst to include modifications to the data model and additional geoprocessing tools that archive GeoStudio SEEP/W and SLOPE/W simulations as well as export the entire Levee Analyst database to Google Earth. Case studies were performed to demonstrate the new geoprocessing tools' capabilities and the compatibility between the National Levee Database and the Levee Analyst database. A number of levee breaches were simulated to prototype the enhancement of the Levee Analyst to include additional feature classes, tables, and geoprocessing tools. This enhancement would allow Levee Analyst to manage, edit, and export two-dimensional levee breach scenarios.