A Dynamic Correction Model (DCM) was implemented to correct daily precipitation data from the network of precipitation gauges hosted by the Swedish Meteorological and Hydrological Institute (SMHI). The goal was to determine whether the DCM could be used to improve estimates of the influence of systematic errors on precipitation observations compared to a previous assessment made on the SMHI dataset using a Simple Correction Model (SCM). While the SCM in question only takes into account station exposure and temperature, reflecting the yearly average gauge level wind speed and the monthly average probability of snow respectively, the DCM would take into account sub-daily and daily observations of precipitation intensity, wind speed and temperature to correct precipitation according to the observed conditions at the time of the precipitation event. DCM corrections were performed on precipitation data from 165 stations throughout Sweden.The long term average result of aggregating daily DCM corrected precipitation was compared to the previous SCM correction for 24 stations while the daily corrected solid precipitation was evaluated against snow depth observations for 59 stations throughout Sweden.Since the systematic errors almost exclusively cause an underestimation of ground true precipitation the correction was expected to produce an increase in total precipitation. Since this undercatch is greater during solid precipitation, a pattern of higher correction was expected to be found in winter months compared to summer months, a pattern which could be expected to be stronger the further north in the country one looked. Furthermore, superimposed on this, areas which are more exposed to wind can be expected to require a larger correction due to the undercatch being also strongly correlated to wind speed. At the sub monthly time scale a variation in the undercatch could be expected when using the DCM with increased corrections required on days when precipitation falls as snow and on days when wind speeds are higher.For the comparison with previous SCM estimates the expectation was that long term totals (30 year average corrected precipitation) would be similar if the two methods are assumed to be equally valid. The DCM was further expected to improve correlations between newly fallen snow and change in snow depth.While the qualitative patterns in the corrections found met the expectations, large differences in the quantitative results of using the two different methods were found; the DCM had a tendency to overcorrect compared to the SCM, especially for the more exposed stations. This calls into question the assumption that both methods are equally valid and differ only in their temporal resolution, and further raises the question which if any of the methods is more valid and why. The evaluation of DCM corrected solid precipitation using snow depth showed a decrease in the correlation between precipitation and change in snow depth which was contrary to expectations. The greatest uncertainty in the DCM was attributed to the methods for assessing gauge level wind speeds.

No description available.

The amount of total organic carbon (TOC) in water is a rough indicator of the waterquality. Driven by the question how the TOC concentration would vary acrossstreams in Sweden under different climate conditions (e.g. more extreme dischargeevents), the temporal dynamics of TOC were examined for different stream subgroupswith six orders of magnitude catchment area span. In addition, the relationshipbetween dissolved inorganic carbon (DIC) export (both downstream and evasion) anddischarge conditions was also studied. Another question addressed was if the amountof TOC exported can be affected by export conditions dominating the previousseason. TOC export followed closely the discharge, which is in agreement withprevious studies, and all 42 catchments studied across Sweden were described by thispositive relationship regardless their size. A linear TOC export response to dischargewas identified during extreme discharge conditions. Furthermore, the TOC export wassignificantly related to the antecedent TOC export conditions for approximately halfof the 18 studied catchments with areas ranging between 2.5·10-3 and 67 km2.

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.