This study investigates the source of nutrients in an agricultural landscape in Kenya. Kapshoi furrow has its intake from Embobut River and flows through the village of Sibou until it reaches the plots in the lowland in Keu. The pH, electrical conductivity (EC), sediment transport, total nitrogen (N) mass flux and total phosphorus (P) mass flux all change when the furrow flows through the village. The most possible cause for the nutrients peaks is the farmers' goats, sheep and cows that walk freely in and around the furrow. This is counter to some existing local theories. The likely cause for the pH decrease and the EC increase are inflow of groundwater (springs) to the furrow. To secure safe drinking water it would be good to uphold the old rules in Sibou of (1) not to live in close proximity of the furrows and (2) not to bathe or do the dishes in the furrow water. This might be difficult due to a fast growing population.

The active layer constitutes an important subsystem of permafrost environments. Thermal andhydrological processes in the active layer determine local phenomena such as erosion, hydrologicaland ecosystem changes, and can have implications for the global carbon-climate feedback.Despite their importance for environmental and climate change, active layer dynamics are stillonly poorly understood. The importance of hydrology for active layer processes is generallywell acknowledged on a conceptual level, but the physical interdependencies between soil moisture,subsurface water flows and active layer depth are largely unresolved. This thesis usedstate-of-the-art numerical modeling to study the influence of ground surface temperature, soilmoisture content and advective heat flow on near-surface permafrost temperatures and activelayer depths. The investigation was performed for a dry, loess-covered river terrace in centralAdventdalen, Svalbard, and fed by high-resolution hydro-climatic field data for the period2000-2014. Nine scenarios were considered in order to independently test the influence ofdifferent initial soil moisture contents (6%, 12%, and 19%) and infiltration patterns (no infiltration,constant infiltration, and early summer peak infiltration). Results indicated that the permafrost-hydrological system at the study site is largely influenced by cryosuction processes due tostrong capillarity of the highly unsaturated soil. Zones of increased ice content developedprimarily near the permafrost table, creating a ‘transition zone’ between the lower part of theactive layer and the upper permafrost. Infiltration based on snow melt and summer precipitationwas found to be negligible for the seasonal active layer development. The active layer depthgenerally decreased with increasing initial soil moisture content due to a higher consumption oflatent heat. However, cryosuction into the permafrost table and water percolation could potentiallycounterbalance latent heat effects, at least in systems characterized by higher soil moisturecontents. Both model simulations and field observations showed a clear tendency of increasingactive layer depth during the study period, whereas inter-annual variations in active layer depthwere comparably small. Given the moisture migration into the ‘transition zone’, the modelresults further suggested that the site might be capable to buffer thaw and thus obscure increasingground surface temperatures to a certain degree. This could have implications for the suitabilityof active layer depth as a proper indicator for climate change.

A good understanding of the local and regional water cycle and how it is modified by landscape changes may help policymakers take the pertinent decisions in order to avoid adverse effects of future hydro–climatic changes. This knowledge is of particular interest in the most vulnerable areas of the world such as the African continent. In this context the aim of this project is to model hydrological responses to possible changes in climatic conditions in Lake Babati, northern Tanzania. For this reason a water balance model specially designed to simulate lake level changes was adapted to Lake Babati and calibrated with the available local meteorological and hydrological data record covering the last decades. The necessary ambient condition changes to produce a dry–out and an overflow of the lake were investigated and the response of the system to future IPCC climate change projections was studied. The results show that for instance a temperature change of less than 3ºC or a precipitation change of around 100 mm/year could eventually bring the lake from a dry–out situation to an overflow situation. Furthermore, the IPCC derived scenarios show a clear tendency of the lake to increase its volume and reach the overflow level in a relatively short time.

No description available.

Messinia is a region in Greece renowned for its rich nature, olive agriculture and water availability. In the light of increasing anthropogenic and climatic pressure, this study assessedlocal water resources in catchments in south western parts of the region. The main objectives were to evaluate the balance between supply and demand, the sustainability of current waterconsumption, capacity of further land use intensification and to review local water management. The method was dual with both quantitative (water balance calculations and linear modeling) and qualitative (interviews and a questionnaire survey) approaches.It was confirmed that, on an annual basis, rainfall is comparatively high, there is a surplus of water leaving the catchments and aquifers are “superfluous”. The climate however, brings seasonal imbalance and notable shortages during summer that affect operation of local actors, especially with agriculture and tourism being the principal water users. Unofficial sources indicated that current consumption may not be sustainable, either because of over-exploitation or climatic changes, but further studies are required to draw reliable conclusions. Modeling showed the importance of land management, that unconsidered water consumption may impact the water balance substantially but also that, while minimizing evapotranspiration,there is capacity of intensification if water withdrawals are increased. Considering accessibility, competitive interests and sustainability however, such development is not necessarily feasible.The municipal water management appeared to be well established and, given that measures are taken concerning for example stakeholder integration and regulation of private and agricultural consumption, there is capacity of handling increasing water stress. Finally, stressing the crucial role of freshwater availability, the study highlighted the importance of further hydrological research and thus the need for improved data quality, particularly regarding river discharge.

No description available.

The quality of the Earth’s water resources have deteriorated due to human impacts. A key scientific challenge is to understand, quantify and predict the water-borne spreading of pollutants at relevant scales for freshwater management and water quality restoration programs. However, understanding the natural processes controlling large-scale hydrological transport of pollutants may be masked by river regulation schemes (in the form of dams and reservoirs), which are common in many large rivers. The main objective of this thesis is to increase the current knowledge regarding large-scale spreading of metals in hydrological systems. This objective is addressed through studying net impacts of mining (a main contributor to global metal pollution) on the spreading of metals in water systems and through investigating the mitigation opportunities of wetlands across the landscape. The main study region of this thesis is the Lake Baikal basin of Russia and Mongolia, which includes the large unregulated Selenga River and its delta-wetland areas. In addition, a set of global wetland sites are also studied. A multi-method approach is used in the four studies of this thesis. The methods include field-measurements, data synthesis, metal mass flow and water flow-path quantifications, as well as geochemical modelling. Results show that mining in the upstream part of the Lake Baikal basin is a significant contributor to riverine mass flows of several metals. The mass flows increased by an order of magnitude over the mining site. The observed speciation between dissolved (more bioavailable) and suspended (less bioavailable) phases could be well predicted for some metals (Fe, V, Pb and Zn) using a geochemical equilibrium model. However, the model failed to reproduce the speciation of other metals (Cr, Cu, Mn and Mo). In these cases, non-equilibrium processes may need to be considered, and adsorption databases may need to be developed, in order to make dependable predictions. Results also suggest that the concentration of dissolved organic carbon, which exhibits seasonal variability and long-term increasing trends due to climate change effects in the Arctic, can have a large impact on metal pollution transport. Further, observations showed that individual wetlands of the Selenga River delta locally retained between 77-99 % of incoming metal loads. However, a systematic analysis of current knowledge showed that large-scale net effects can differ considerably from the functions observed at individual wetlands on smaller scales. Along large-scale flow-paths, through which wetlands are connected with each other as well as with the larger landscape, key processes which can considerably contribute to such scale differences in function may occur. A survey of the current wetland research showed that relatively few studies have considered the larger scales at which key pollutant pressures and water quality changes take place. This thesis highlights the need for more research on large-scale wetland systems, which can aid in evaluating net pollution effects at landscape scales. This in turn can facilitate evaluations of how and when wetland systems may function as large-scale nature-based solutions. / Kvaliteten på jordens vattenresurser har försämrats på grund av mänsklig påverkan. En viktig vetenskaplig utmaning är att förstå, kvantifiera och förutsäga den vattenburna spridningen av föroreningar, på skalor som är relevanta för vattenresursförvaltning och åtgärdsprogram. De underliggande, naturliga processer som styr storskalig hydrologisk föroreningstransport kan dock maskeras av att de flesta stora floders flöden är reglerade med hjälp av dammar och reservoarer. Målet med den här avhandlingen är att öka kunskapen kring hydrologisk storskalig spridning av metaller. Detta görs genom att studera nettoeffekter av gruvverksamhet (en viktig källa till globala metallföroreningar) på metallers spridning i vattensystemet, samt att undersöka våtmarkers möjligheter att rena förorenade flöden i landskapet. Avhandlingens huvudstudieområde är Bajkalsjön och dess tillrinningsområde (i Ryssland och Mongoliet), vilket inkluderar den oreglerade Selengafloden och dess delta-våtmarksområden. Även en grupp av globala våtmarksområden har studerats. Flera metoder användes i de fyra studierna som ingår i denna avhandling, inklusive fältmätningar, datasyntes, massflödes- och flödesvägskvantifieringar, och geokemisk modellering. Resultaten visar att gruvdrift i uppströms-delar av Bajkalsjöns tillrinningsområde bidrar betydligt till förhöjda halter av flera metaller i flodsystemen. Massflödenena ökade en storleksordning över gruvområdet. Den observerade metall-specieringen mellan lösta (mer biotillgängliga) och partikulära (mindre biotillgängliga) faser kunde modelleras väl för vissa metaller (Fe, V, Pb och Zn) med en geokemisk jämviktsmodell. Modellen lyckades dock inte reproducera specieringen av andra metaller (Cr, Cu, Mn och Mo). I dessa fall kan icke-jämviktsprocesser behöva beaktas, och adsorptions-databaser kan behöva utvecklas för att förbättra prediktionerna. Resultaten visar också att koncentrationen av upplöst organiskt kol, som uppvisar stora årstidsvariationer samt långsiktigt ökande trender på grund av klimatpåverkan i Arktis, kan ha stor inverkan på metallföroreningars transport. Observationer visade att enskilda våtmarker i Selengafloden lokalt kunde minska inkommande massflöden av metaller med 77 till 99 %.  En systematisk genomgång av aktuellt kunskapsläge visade dock att storskaliga nettoeffekter kan skilja sig mycket från de funktioner som observeras vid enskilda våtmarker på mindre skalor. Längs storskaliga flödesvägar, genom vilka flera våtmarker är kopplade till varandra och till det större landskapet, kan viktiga processer ske, vilket avsevärt kan bidra till sådana skal-skillnader i funktion. En genomgång av aktuell våtmarksforskning visade att relativt få studier beaktade dessa större skalor där föroreningsspridning och vattenkvalitetsförändringar sker. Denna avhandling belyser behovet av ökat forskningsfokus på storskaliga våtmarkssystem. Detta kan hjälpa till att förstå föroreningars nettoeffekter på landskapsskalor, vilket underlättar vid bedömning av hur och när våtmarkssystem fungerar som storskaliga, så kallade naturbaserade lösningar.

Successfully modeling one system response (e.g. hydrograph or solute transport) sometimes gives the false sense of well-characterizing the modeled system. This is partly because of the well-known equifinality issue; during the calibration process multiple parameter combinations can produce similarly good results. One step forward towards a better-defined system is using measured (at relevant scale) values for the model parameters, as well as using multiple conditions to constrain the model. But when not enough, or relevant, field measurements are available, virtual experiments (VE’s) can be used as a supplementary method to model calibration. The advantage of VE’s over model calibration is that they can also be used to explore assumptions both on the system hydrological processes, and on the model structure. One goal of this study was to utilize both field measurements and models for better characterization of the S-transect hillslope, located in Västrabäcken catchment, Northern Sweden. This included (a) characteristics in space: system vertical boundaries, hydraulic parameters, pore water velocity distribution, spatial correlation of flowpaths, soil water retention properties; (b) characteristic of system’s dynamic behavior: storage – discharge relationship, transit time distribution, turnover time; and (c) outputs’ sensitivity to external forcing, and to small scale structure assumptions. The second goal was to comment on the value of field measurements and virtual experiments for extracting information about the studied system. An intensely monitored study hillslope was chosen for this work. Although the hillslope has already been the subject of multiple field and modelling studies, there are still open questions regarding the characteristics listed above. The models used were the Vertical Equilibrium Model (VEM), and the Multiple Interacting Pathways (MIPs) model. It was found that the hillslope was well connected; from the near-stream areas up to the water divide the storage – discharge relationship could be described as an exponential function. Also, the dynamic storage (which controls the hydrograph dynamics) was much smaller comparing to the total hillslope storage. The unsaturated soil storage was found to be more sensitive to water table positions than vertical flux magnitude. The dynamic condition of external forcing (precipitation and evapotranspiration) affected the transit time distribution (TTD) shape. And, opposite to expectations, TTD was not sensitive to micro-scale structural assumptions tested here.

In this study, GIS methods were used in order to evaluate different wetness indicators — topographic indices and airborne gamma radiation measurements — from their ability to distinguish wet areas from other areas. As a surrogate measure of extreme wetness, the occurrence of mires from land use maps were used. The evaluation of each wetness indicator was made in two ways. First, mire and non mire values for each measure was tested for similarity. Then, predicted mire maps were produced by defining mire area class limits (threshold values), which gave the same fraction of mire area in the catchments as in the land use maps. The predicted mire maps were then compared to the map showing mires from land use surveys. The best predictions were made by the drainage efficiency index (46.8% correct mires of all mire cells), which was proposed as an alternative to the ln(α/tanβ) index (the TOPMODEL index) and slope. This index quantified the downslope drainage ability for any point in the catchment, which is likely to be important for the wetness status. Mire predictions from K-40 gamma radiation were correlated to the different geological regions in the area and did not reproduce an accurate overall mire pattern. The TOPMODEL index class limits were strongly correlated to the fraction of mire area, which prevented it from being a good indicator of mires. It did not reproduce accurate amounts of area in the subbasins from a global threshold value. However, the general pattern of the predicted mires agreed relatively well with the pattern of actual mires from the land use map. / I en studie undersöktes förmågan hos olika mått på markfuktighet — topografiska index samt flyguppmätt naturlig gammastrålning från K-40 att särskilja våta områden från övrig mark. Som ett mått på extremt fuktig mark användes förekomsten av myrar från Gröna Kartan. Utvärderingen av de olika fuktighetsmåtten gjordes först genom att jämföra frekvenskurvorna för myrmark respektive övrig mark och kvantifiera skillnaden mellan dessa fördelningar för varje fuktighetsmått. Därefter uppskattades ett tröskelvärde för varje fuktighetsmått, vilket delade frekvensfördelningen i två klasser. Tröskelvärdet valdes så att förhållandet mellan arean i våt respektive torr klass blev densamma som mellan myrmark och övrig mark ur Gröna Kartan. Med utgångspunkt från dessa tröskelvärden framtogs kartor med simulerade myrar för varje fuktighetsmått, vilka jämfördes med myrarna i Gröna Kartan. De simulerade myrarna från ett topografiskt index som kvantifierade dräneringsförhållanden nedströms i terrängen gav bäst överensstämmelse med de verkliga myrarna (46.8% rätt klassade myrceller av det totala antalet myrceller). Simuleringen av myrar från K-40 gammastrålning var starkt beroende av berggrundstypen i området, och det övergripande mönstret gav ingen god överensstämmelse med Gröna Kartans myrar. Tröskelvärdena för ett av de topografiska index som granskades, ln(α/tanβ) index (TOPMODEL index), visade ett mycket tydligt beroende av andelen myr i området som simulerades, vilket gjorde att det svart att sätta ett gemensamt tröskelvärde for alla delområden i studien. Trots detta överensstämde myrmönstret från detta index i huvudsak med myrområdena från Gröna Kartan. / <p>Delar av examensarbetet publicerades senare som ”Water Resources Research technical note”: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004WR003130</p>

Flow in fractured rocks has been intensively studied in the last decades, in part due to plans in manycountries to site repositories for high level nuclear waster in deep geologic formations. All investigated crystalline rocks have been found to be fractured and the majority of water flows through these fractures andfracture zones. Therefore, it is of interest to be able to understand and model flow rates, flow pathwaysand discharge through realistic rough-surfaced fractures. Conventional experiments using rock samples havedifficulty controlling and observing fracture properties, in particular the highly variable fracture aperturevoid space. Therefore, taking advantage of 3D printing technologies, two samples were created representinga constant and varying aperture fracture. This allows the properties of the fracture to be controlled andidentical geometries for both experiment and simulation to be prepared. Development of a laboratory experiment allowed for flow tests over different hydraulic gradients to be conducted through the printed samples.Discharge was numerically simulated through 9 single fracture cases, 5 of which have a constant aperture,assuming the Navier Stokes equations and using a computational fluid dynamics solver (OpenFOAM). Theresult of the simulation based on the Navier Stokes equations was within 5% of the experimental result forhydraulic gradients of 0.01 and 0.05, this suggests that the results from the experiment and simulation arereliable. In order to observe the transition from Darcy to non Darcy flow through a single fracture the hydraulic gradient was systematically increased. The results from both the experiment and the simulation werecompared to the simplified cubic law assumption using various estimates of aperture. Inertial forces influencethe discharge and have more importance on varying aperture geometry, therefore the transition to non Darcyflow in smooth apertures occurs at a higher hydraulic gradient. Calculation of the cubic law using the meanaperture value including zeros can reduce the difference between simulated discharge. A two-fracture systemwith one intersection was also simulated to investigate the influence of intersection geometry on discharge,which seems to be dependent on flow velocities, with low and high flows producing less variable discharge.Uncertainties between numerical simulation and laboratory experiments can be reduced by using 3D printedfracture networks, hence they can be a beneficial for understanding complex interactions that can happenwithin networks.