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The diploma thesis deals with monitoring of metrological characteristics of ultrasonic sensors located at the FAST and in-situ and the evaluation of the time development in the values of the discharge and the outflow volumes reported by the ultrasonic sensors.

Benthic invertebrates inhabiting boreal rivers are exposed to very large seasonal variations in their physical environment. The extremes are in winter when the littoral area freezes solid and in spring when water flow increases rapidly. In the North Swedish river Vindelälven, the invertebrates fell into three main categories according to their seasonal lateral distribution. One category of animals was stationary in the littoral zone and let itselt freeze into the ice, adopting a "take it" alternative. The category consisted of many species belonging to several higher taxa. By overwintering in ice, the animals avoided predation for nearly half the year and they were in the productive littoral at the same time as they thawed out from the ice in spring. On the other hand the animals had to withstand sub-zero temperatures. A typical representative for this category of animals was the semivoltine snail Gyraulus acronicus. It is a less mobile species connected to dense stands of macrophytes, which are found only in the littoral zone of the river. Nearly the whole population was found overwintering successfully enclosed in ice. Its shell and epiphragm could serve as mechanical protection when frozen into the ice. G. acronicus was cold-hardy only during late autumn and early winter, but it could stand prolonged sub-zero exposure during the proper time. A second category of animlas avoided being frozen by performing lateral movements to deeper parts of the river, adopting the Vleave it" alternative. No species tested in this category were found cold-hardy. It consisted of mobile species known to utilize sedimentated detritus which was only found in greater amounts in the littoral zone of the river. In springtime, prior to spring flood peak, these species colonized promptly the former frozen zone. This behaviour was most pronounced in several lentie mayfly species. An extreme case of migratory behaviour was found in the mayfly Pararneletus chelifer which not only moved towards the river bank but continued up into small tributaries. The shoreward movements of mayflies both allowed the nymphs to avoid the high current velocities in the central part of the river during spring flood time and to utilize the food resources in the flooded areas. A third category of animals avoided the ice by living stationary in the sublittoral zone, adopting the "never face it" alternative. This category was dominated by filter feeders. / <p>Diss. (sammanfattning) Umeå : Umeå university, 1982, härtill 5 uppsatser</p> / digitalisering@umu

River environments are complex and dynamic ecosystems, and provide valuable ecosystem services such as clean water. The species rich riparian vegetation performs many important ecosystem functions such as reducing erosion and filter inputs from upland areas. Regulated flow regimes have decreased riparian plant species richness, cover and plant performance. To restore the integrity of riparian ecosystems, mitigation measures such as re-regulation of water-level regimes toward more natural seasonal fluctuations may be needed. The aim of this study was to assess potential responses of riparian plants to changes in water-level regulation in run-of-river impoundments to better match natural flow regimes. The elevational extent of plant species on riverbanks of two run-of-river impoundments in the Ume River were surveyed and their probability of occurrence along the gradient of inundation duration was modelled and compared to their distribution in the free-flowing Vindel River. Most species showed similar tolerance to flooding in the Ume and Vindel Rivers. Changes in elevational extent in response to three simulated environmental flow regimes were predicted by using the relationship between plant occurrence and inundation duration. A simulated spring flood and low water levels during the latter part of the growing season is predicted to result in the largest increase in elevational extent, with increases of 70-80% for several riparian species. However, only 47% of the riverbanks along run-of-river impoundments in the Ume River is deemed to be suitable for plant establishment, since many riverbanks are steep and devoid of fine-grained substrate as a result of erosion. / Älvmiljöer utgör komplexa och dynamiska ekosystem som tillhandahåller värdefulla ekosystemtjänster så som rent vatten. Den artrika strandvegetation bidrar till många viktiga ekosystemsfunktioner som närings- och giftupptag och till minskad erosion. Vattenregleringen med förändrade flödesregimer har minskat artrikedom, täckningsgrad och tillväxt av strandväxter. För restaurering av strandekosystemen kan omreglering till mer naturliga säsongsvariationer i vattenståndet vara nödvändigt. Den här studien syftade till att förutsäga hur utbredningen av strandväxter längs stränder i vattenkraftsmagasin potentiellt skulle förändras vid användande av miljöanpassade flöden för att mer likna naturliga flödesregimer i outbyggda älvar. Jag undersökte växternas utbredning i höjdled på stranden längs två magasin i Umeälven och beräknade sannolikheten för varje arts förekomst längs strandens översvämningsgradient. Av de arter som förekom i både Umeälven och den närliggande, outbyggda Vindelälven jämfördes växternas utbredningsgränser i respektive älv. De flesta arterna uppvisade liknande översvämningstolerans i Umeälven och Vindelälven. För att förutsäga förändringar i utbredning som respons på tre olika simulerade miljöanpassade vattenståndsregimer, jämfördes arternas översvämningstolerans vid nuvarade vattenstånd med simulerade vattenståndsregimer. En simulerad vårflod och lågt vattenstånd under sensommaren förväntas ge de största responserna i artutbredning med ökningar på 70-80% för ett flertal strandväxter. Endast 47% av älvstränderna i magasinen i Umeälven bedöms vara lämpliga för växtetablering eftersom stora delar av strandsträckorna är branta och saknar finkornigt substrat till följd av erosion.

A 1-D tidal, salinity and water quality model that analyzes the impacts of freshwater diversions with median and high flow on the water level, salinity and nutrient concentration of the Barataria Basin over a 2 period is presented here. The model predicts that the salinity of Lower Barataria decreases with the introduction of freshwater diversions. The model also predicts that nutrient concentration increases in Barataria Basin and decreases in Northern Gulf of Mexico with the introduction of diversions. The model shows the impact of freshwater diversions on water level except in the neighborhood of the diversion sites are small.

La zone littorale, de grande importance pour le fonctionnement écologique du lac, est souvent la première zone réceptrice de la contamination provenant du bassin versant. Cette pollution est majoritairement piégée dans les sédiments de surface. Pour autant, les conditions environnementales variables qui règnent en zone littorale sont susceptibles de favoriser la biodisponibilité des contaminants par le jeu des réactions physico-chimiques et biologiques. Cette thèse s’appuie sur l’étude de deux grands lacs péri-alpins, le Lac du Bourget et le Lac d’Annecy, pour mieux comprendre le comportement des polluants sédimentaires (ETM, HAP et PCB) en zone littorale lacustre. Nos travaux visent notamment (1) à caractériser la contamination littorale et l’influence des sources locales dans cette contamination, (2) à évaluer l’écotoxicité des sédiments littoraux et les changements de mobilité et de biodisponibilité des polluants sédimentaires sous l’influence de changements abiotiques de la zone littorale tels que ceux induits par le marnage lacustre. Nos résultats montrent que la contamination des sédiments et organismes autochtones présente une hétérogénéité spatiale significative sur le littoral des deux lacs, tant en intensité qu’en composition (i.e. profil de contamination). L’implication de sources locales (e.g. eaux pluviales drainées sur le bassin-versant) dans cette hétérogénéité spatiale a été mise en évidence. L’écotoxicité des sédiments de la zone littorale, évaluée via la réponse de biomarqueurs enzymatiques (AChE, GST), physiologiques (e.g. taux d’ingestion chez D. magna) et des traits de vie (e.g. taux de croissance, reproduction et survie) présente également une hétérogénéité spatiale significative. La biodisponibilité des ETM sédimentaires a été plus spécifiquement étudiée aux interfaces sédiment-eau-biote. Elle varie selon l’élément, le biote exposé (benthique ou pélagique) et sous l’effet du marnage. L’assèchement et remise en eau du sédiment littoral s’accompagnent d’une réduction de la fraction biodisponible des ETM. L’abaissement de la hauteur d’eau, en revanche, entraîne une accentuation de la remise en suspension de particules sédimentaires susceptibles d’exercer un risque écotoxicologique sur le biote littoral. Nos résultats soulignent la complexité de la contamination littorale et de son transfert dans les grands lacs péri-alpins et encouragent les approches écotoxicologiques dans l’évaluation de l’état écologique. / The littoral zone of lakes is of great ecological importance and yet receives a large array of contaminants from the watershed. This pollution is mainly trapped by the surface sediment, but its bioavailability may be allowed by physico-chemical and biological reactions in this zone of high environmental fluctuations. This work aims at improving knowledge about the behavior of sediment-borne contaminants (trace metals, PAHs and PCBs) in the lake littoral zone by using two large perialpine lakes; Lake Bourget and Lake Annecy. More precisely, our goals were to (1) characterize the littoral contamination and the influence of local sources in this contamination, (2) assess the ecotoxicity of the sediment-borne contamination and the main changes in its mobility and bioavailability under abiotic changes in the littoral zone, such as those related to water-level fluctuations in lakes. The contamination of the sediments and native organisms exhibited a significant spatial heterogeneity along the lake littoral, in both intensity and profile’s composition. The involvement of local sources of contamination (e.g. stormwater runoff) as drivers of this spatial heterogeneity has been highlighted. The ecotoxicity of littoral sediments was assessed through the responses of enzymatic biomarkers (AChE and GST), physiological traits (e.g. ingestion rates in D. magna) and life-history traits (e.g. growth, reproduction and survival rates). Our results also underscored a significant spatial heterogeneity of the littoral sediment ecotoxicity. A greater focus on the bioavailability of trace metals at the sediment-water-biota interfaces showed that bioavailability depends on the metal, the exposed biota (benthic vs pelagic) and fluctuate under water-level fluctuations. Drought and re-immersion of surface sediments were followed with a reduction of the bioavailable fractions of the trace metals. However, decreases in the water-level led to increase suspended sediments in the water column, which may exert an ecotoxicological risk for the littoral biota. Our results underline how complex the littoral contamination and bioavailability are and promote ecotoxicological approaches in the assessment of the ecological status of large lakes.

Understanding the role of freshwater wetlands in the global carbon cycle has become more important as evidence of climate change grows. In this paper, we examine the burial and decomposition of particulate organic matter (POM) in a temperate, siliciclastic, seasonal wetland. High POM abundances are found in silt layers, while sand units preserve very little POM. The POM distribution with depth is compared to the biogeochemistry of sediment porewater with depth. POM acts as a driver for reduction reactions within the wetland soil. Porewater biogeochemistry and POM decomposition are controlled by seasonal changes in the level of the water table which cause seasonal shifts in the oxic/anoxic boundary. At the oxic/anoxic boundary, reoxidation of FeS minerals in the soil cause rapid POM decomposition at the average minimum water table level in the late summer and early fall. Variation in the minimum depth of the water table from year to year may account for fluctuating POM numbers in the upper silt layers. The results from this study can be used to predict seasonal water level fluctuations in ancient wetland and to explain recurrence horizons in peat.

A mesocosm experiment was conducted in Lake Eymir between June &ndash / September 2009 in order to elucidate the effects of water level changes and fish predation on periphyton growth and macroinvertebrates in semi-arid shallow lakes. Twenty four cylindrical enclosures, each with 1.2 m diameter, open to lake bottom and atmosphere, were placed at three different depths, i.e. 0.8 m (low water level, LW), 1.6 m (high water level, HW) and 2.3 m (however, data regarding the enclosures at 2.3 m were excluded in this study due to complications after fifth sampling) to simulate water level fluctuations. At each water level, four replicates were stocked with omnivorous&ndash / planktivorous fish (Tinca tinca and Alburnus escherichii) and the other four replicates were left fishless to observe the effect of fish predation. Ten shoots of submerged macrophytes (Potamogeton pectinatus) were planted and six polyethylene strips were hung in the water column in each enclosure to monitor macrophyte and periphyton growth. The mesocosms were sampled for physical, chemical and biological parameters weekly in the first month and fortnightly thereafter. Benthic macroinvertebrate samples were taken before the start, in the middle and at the end of the experiment with Kajak corer. Macrophytes were harvested after the last sampling for determination of dry weight, epiphyton, and the associated macroinvertebrates. All macroinvertebrate samples were sieved through 212 &mu / m mesh size before identification and counting. Over the course of the experiment, an average of 0.46 &plusmn / 0.03 m water level decrease in the mesocosms triggered submerged macrophyte growth in all LW enclosures, overriding the negative effects of fish predation. The results indicate that while fish predation pressure had negative influences on macroinvertebrate communities in terms of both abundance and richness, structural complexity created by dense vegetation in the LW mesocosms weakened the top-down effect of fish on macroinvertebrates by acting as a refuge in this semi-arid shallow lake.

Iškritus krituliams ant žemės paviršiaus, dalis jų susigeria į gruntą, o kita dalis nuolydžio kryptimi teka link žemiausių reljefo vietų. Susigėrimo intensyvumas priklauso nuo grunto laidumo. Sunkiuose gruntuose vandens susigeria ir patenka į gilesnius grunto sluoksnius gana sunkiai dėl mažo grunto laidumo. Intensyviausiai vanduo nuo žemės paviršiaus teka drenažo tranšėjomis ir šalia jų. Šios vandens tekėjimo sąlygos tranšėjose susidaro pakitus grunto struktūrai, jas užverčiant. Laikui bėgant, drenažo tranšėjoje atsiradę plyšiai užnešami smulkiomis grunto dalelėmis. Tai įtakoja grunto vandens laidumo savybių prastėjimą. Norint pagerinti vandens nutekėjimą iš viršutinio dirvožemio sluoksnio, padėtų natūralios gamtoje sutinkamos medžiagos, įterptos skersai virš vamzdinio drenažo. Drenažo tranšėjų užpylimui naudojant poringas medžiagas, dalis atitekėjusio vandens akumuliuotųsi naujai įrengtose skersinėse drenažo tranšėjose. Tokios technologijos taikymas leistų padidinti sausinimo efektyvumą nekeičiant jau paklotų drenažo vamzdžių. Modeliuojant skersinių drenažo tranšėjų tankio įtaką vandens lygiui tarpdrenyje, nustatyta, kad papildomas jų įrengimas turi įtakos gruntinio vandens lygiams tarpdrenyje tik esant atstumui iki 30 m. Esant didesniam atstumui, jų poveikis gruntinio vandens lygio nuslūgimui tampa nežymus, siekia vos 1-2%. Didžiausią įtaką gruntinio vandens slūgimui tarpdrenyje turėjo skersinės drenažo tranšėjos įrengiamos 20 m tarpais, kai drenažo tranšėjos užpildo... [toliau žr. visą tekstą] / After rainfall, part of it is absorbed by the ground whereas the rest part flows upon the direction of the inclination towards the lowest points on the relief. Intensity of absorption depends on conductivity of the ground. In the hard ground water is absorbed and enters the deeper layers of the ground with difficulty due to low conductivity of the ground. Water flows most intensely through drainage trenches and next to them. These conditions of water flow in trenches form when the ground structure alters and overloads them. The time passing by, cracks, having occurred in the drainage trench, are filled with small ground particles. It influences deterioration of ground water conductivity qualities. In order to improve water runoff from the upper soil layer, natural substances found in nature, if inserted across, above the drain, could help. Using porous substances in order to cover drainage trenches, part of the water would accumulate in newly equipped cross-section drain trenches. Applying such a technology would allow increasing the efficiency of drainage without changing the already laid drainage pipes. Modeling the influence of cross-section drainage trench density on ground water level between drains, it was determined that additional installation could affect ground water level between the cross-section drains trench, the distance being up to 30 meters. When the distance is larger, its impact on the ground water level recession becomes insignificant and reaches only 1-2%... [to full text]