No description available.

Vattenståndet i Fyrisån mättes dagligen vid Uppsala vattenverk vid Islandsfallet under tiden 1876 till 1969. Ur dessa data kunde vattenföringen för samma period rekonstrueras. Ett problem vid rekonstruktionen var att tröskelhöjden i fallet tidvis under åren varit uppbyggt för att få ut större mängd kraft ur vattenverkets turbiner. Detta begränsade vattenföringsberäkningen till högvattenföringar. Vid högvattenföring var tröskeln oftast nedrasad och dagens avbördningskurva användbar. Avbördningskurvan baserades på vattenföringsmätningar som gjordes vårarna 1984, 1985, 1986 och 1990, perioder på året då vegetationsdämningen är försumbar. Högsta vattenföring inträffade 1888 med 106 m3/s, vilket motsvarar ett vattenstånd på 364 cm i Uppsala kommuns lokala höjdsystem. Medelhögvattenföringen i ån är 44 m3/s. Vattenföringen i Fyrisån har en stor årstidsvariation beroende på att avrinningsområdet är väldigt sjöfattigt, bara 2% av arealen är sjöartäckt. Detta leder till en större skillnad mellan hög- och lågvatten än normalt för en å i mellansvenska låglandet. / The water stage was measured once a day at the old municipal water works immediately upstream the last falls (Islandsfallet) in the River Fyris during the period 1876 to 1969. From these data it was possible to reconstruct a discharge series for the same period. One problem with the reconstruction was the temporary raising of the threshold of the falls in order to increase the capacity of the turbines in the water works. This limited the reconstruction to high water discharges. The temporary threshold was normally washed away during high discharge situations which allowed the use of the present day stage-discharge relation. This relation was based on discharge measurements made in the springtime of 1984, 1985, 1986, and 1990; periods of the year when the vegetation does not dam up the flow. The highest discharge occurred in May 1888. lt was 106 m3/s which corresponds to a water level of 364 cm in the Uppsala Local Municipal datum system. The average high discharge in the river was 44 m3/s. The discharge has a large seasonal variation, due to the fact that only 2 % of the contributing basin consists of lakes. This explains the bigger difference between flood discharge and low water discharge compared to what is normal for a river in the Central Swedish Lowlands.

No description available.

While streams and rivers emit large quantities of CO2 to the atmosphere, both the mechanisms controlling CO2 evasion as well as the sources of CO2 are still uncertain. One potential source of stream CO2 is in-stream degradation of dissolved organic matter (DOM). Streams and rivers transport, stores and transform large quantities of DOM, which can be more or less biologically reactive (bioreactive) meaning how easily accessible the organic material is for biological degradation. Little is known about the dynamics controlling DOM bioreactvity in agricultural stream water. This project investigated potential physico-chemical and land-use controls of DOM bioreactivity and its link to CO2 evasion in ten Swedish agricultural streams by correlating estimated values of DOM bioreactivity as well as CO2 evasion rates with different parameters for physico-chemical and land-use controls measured during eleven field excursions. A direct positive correlation was found between DOM bioreactivity and CO2 evasion rates during spatial correlation but not when all measurements were used. DOM bioreactivity was found to correlate to parameters for DOM quality and quantity, concentrations of dissolved oxygen (D.O.) and total dissolved solids (TDS) as well as stream width, water depth, specific discharge, temperature and electric conductivity. Nutrients, fraction land-use, catchment size, vegetation cover and turbulence were not found to be potential controls of either DOM bioreactivity or CO2 evasion. CO2 evasion was found to have fewer significant correlations with parameters for DOM quality compared to DOM bioreactivity, indicating a weaker link between CO2 emissions and DOM quality in the stream water, and was not tied to variables affected by increased discharge. Spatial and temporal analysis indicated that while CO2 evasion rates were more site specific, bioreactivity was more influenced by temporal variations where periods of increased bioreactivity and increased variability between sites occurred during periods of increased specific discharge, supporting existence of a hydrological influence on DOM bioreactivity.

Wave heights and periods of surface waves in the Baltic Sea have been modelled for a two-year period (1999-2000) with the wave model Hypas on an 11x11-km grid scale. There is a clear seasonal variation with higher waves during winter and lower during summer. This is mainly a reflection of the wind climate in the area where the winters are windier than the summers. The largest waves are found in the Skagerrak and over the deeper, eastern areas in the Baltic Proper. In the Baltic Sea, the surface waves influence the bottom sediment by initiating resuspension down to 80 m depths. This process is dependent not only on the waves but also on the varying grain size diameters. Fine and medium sand resuspend more often than other sediment types, and these sediments cover together about 25% of the Baltic Proper area. On average sediment is here resuspended 4-5 times per month with a duration for each event of 22 hours. The highest resuspension frequencies are found on the eastern and southern side of the Baltic Proper. During resuspension sediment grains are lifted up into the water mass and matters earlier bound in the sediment can be released. This may stimulate both production and degradation of organic matter.

En funktionskontroll har utförts av en nyinstallerad hydrologisk mätutrustning i Fyrisån som rinner genom Uppsala, där analyser av inhämtade vattenprover har jämförts med mätvärden från mätutrustningens sensorer. Genom en interkalibrering med en äldre mätstation har en avbördningskurva tagits fram till mätstationen vilket visade sig vara en enkel metod som gav tillförlitliga värden. De parametrar som sensorn loggar dygnet runt studerades i syfte att hitta samband mellan dessa och transporten av näringsämnen i Fyrisån, mellan fosfor och turbiditet kunde ett sådant samband anas. Fyrisåns vattenkemi speglar markanvändningen i avrinningsområdet där den kalkrika marken ger en förhöjd konduktivitet och jordbruksmarkerna tillför kväve. Då Fyrisån passerar Uppsala sker en ökning av lösta och suspenderade partiklar samt närsalter. Även årstidsvariationer gällande vattenkvalitén observerades där vattenstånd och turbiditet ökar vid nederbörd samt snösmältning. Konduktivitet visar på ett motsatt förhållande där konduktiviteten minskar vid ökat vattenstånd. / A functional assessment has been carried out for newly installed hydrological monitoring equipment in the river Fyris, in Uppsala, Sweden. Collected water samples were analyzed and compared with measured values from the measuring equipment's sensors. A rating curve was produced for the station by implementing an intercalibration with an older measuring station; this proved to be an easy method which yielded reliable values. The different parameters that the sensor registered every 30th minute were studied in order to find correlations between these and the transport of nutrients in the river Fyris. A correlation between phosphorus and turbidity was observed. The water chemistry in the river Fyris reflects the land use in the catchment area, and the elevated conductivity is caused by calcareous soils and nitrogen is derived from agricultural practices. When the river Fyris passes the city Uppsala an increase in dissolved and suspended particles and nutrients can be seen. Seasonal variations regarding the water quality can be observed as the water level and the turbidity increases during precipitation and snowmelt. The conductivity indicates an inverse relationship with decreasing values as the water level rises.

Under hösten 1994 startades en undersökningsserie av Stockholm Vatten AB där bl.a. syrgastäring och PO4-P-läckage av sediment analyserades från ett antal sjöar i Stockholms tillrinningsområde. Som ett led i undersökningsserien analyserades i denna rapport syrgastäringshastigheten och PO4-P-läckaget av homogeniserat sediment vid 13 provpunkter i Stockholms innerskärgård under våren 1995 med hjälp av en ny analysapparatur. Samtidigt undersöktes analysapparaturens reproducerbarhet, biomassa av bakterier samt potentiell aktivitet hos denitrifierande bakterier i sediment från respektive provpunkt. Resultaten tyder på att syrgastäringshastigheten beror på från vilken bottentyp sedimentet är hämtat samt den organiska halten hos sedimentet. Likaså verkar storleken på PO4-P-läckaget från sedimenten bero på från vilken bottentyp sedimentet är hämtat men även på de fysikaliska betingelserna som karaktäriserar provpunkten. Reproducerbarheten hos den nya analysapparaturen kan anses vara relativt god vid beräkning av både O2- och PO4-P-koncentrationen i vattenpelaren ovanför sedimentytan. Vid koncentrationer hos syrgasmättnaden, där bl.a. syrgastäringshastigheten har beräknats, är variationskoefficenten låg, dvs. för koncentrationer ≥50 %. På liknande sätt är variationskoefficienten låg vid PO4-P-koncentrationer över 100 µg/l. Biomassan av bakterier varierade mellan 0,48 och 2,66 mg/g TS med de lägsta halterna längst in i provtagningsområdet och de högsta längst ut i området. Den potentiella aktiviteten hos denitrifierande bakterier uppvisade ett oregelbundet resultatmönster i undersökningsområdet. / During autumn 1994 an investigation-sequence was started by Stockholm Vatten AB where oxygen demand and PO4-P-leakage were analysed of sediments from few lakes in the drainage area of Stockholm. As a contribution to the investigation-sequence the oxygen demand and the PO4-P-leakage of homogenised sediments at 13 locations in the archipelago of Stockholm were analysed during spring 1995 in this report, using a new method. Parallel to these analyses there was a test of the reproducibility of the analysis-device, determination of bacterial biomass and potential activity of denitrified bacteria in sediments from each sample location. The results indicate that the oxygen demand is dependent on type of the bottom the sample were taken and on the organic content of the sediments. The magnitude of the PO4-P-leakage seems also to be dependent on the type of the bottom as well as the physical conditions that characterise the location. The reproducibility of the new analysis-device seems to be relatively good for measurements of both O2- and PO4-P-concentrations in water above the sediments. The coefficient of variation was low at O2-saturation where the oxygen demand were measured, i.e. O2-saturation ≥50%. In the same manner, the coefficient of variation was low at PO4-P-concentrations above 100 µg/l. The bacterial biomass varied between 0,48 and 2,66 mg/g DS, with the lowest concentrations in the inner parts of the test-area and the highest concentrations in the outer. The result of the potential activity of denitrified bacteria showed an irregular pattern in the test-area.

<p>The aim of this thesis was to estimate and possibly quantify ocean flow by utilizing conventional and novel observational methods as well as model results. Motionally induced voltages, from a cable-based observational system in the Baltic Sea, were analysed to determine their utility for ocean monitoring. The data set was examined as regards the influence of single- and multi-layer flow. Correlation analyses undertaken in the first study showed that the geoelectric installation is capable of providing good estimates of the net flow across the Visby-Västervik transect. The second study focused on possible effects of multi-layer flow on the signal. Comparisons were made with tidal-gauge geostrophic flow estimates, and a good agreement was found, except for a few brief winter periods characterized by significant discrepancies. The velocity fields from a three-dimensional model showed that these events coincided with strong surface and bottom currents, and hence the attenuated voltage signal was suggested as being caused by the non-uniform velocity distribution.</p><p>The third study dealt with the deep-water flow through the Understen-Märket trench. Observational data indicated that this flow could be described by applying hydraulic theory. Since the passage is narrow compared to the internal Rossby radius of deformation, rotational effects could be neglected to lowest order. The theoretical predictions proved to agree well with the observational results.</p><p>The final study examined the effects of the heat flux and the wind forcing on the circulation in Bahía de Concepción, Chile, where three field surveys were undertaken during the extended austral summer 2002. Hydrographic and current measurements were compared to local tidal-gauge records. Rough estimates of the barotropic and the baroclinic flow across the transect indicated an unusual vortex circulation during periods of weak wind forcing and strong surface heating; results which were corroborated by numerical simulations.</p>

The aim of this thesis was to estimate and possibly quantify ocean flow by utilizing conventional and novel observational methods as well as model results. Motionally induced voltages, from a cable-based observational system in the Baltic Sea, were analysed to determine their utility for ocean monitoring. The data set was examined as regards the influence of single- and multi-layer flow. Correlation analyses undertaken in the first study showed that the geoelectric installation is capable of providing good estimates of the net flow across the Visby-Västervik transect. The second study focused on possible effects of multi-layer flow on the signal. Comparisons were made with tidal-gauge geostrophic flow estimates, and a good agreement was found, except for a few brief winter periods characterized by significant discrepancies. The velocity fields from a three-dimensional model showed that these events coincided with strong surface and bottom currents, and hence the attenuated voltage signal was suggested as being caused by the non-uniform velocity distribution. The third study dealt with the deep-water flow through the Understen-Märket trench. Observational data indicated that this flow could be described by applying hydraulic theory. Since the passage is narrow compared to the internal Rossby radius of deformation, rotational effects could be neglected to lowest order. The theoretical predictions proved to agree well with the observational results. The final study examined the effects of the heat flux and the wind forcing on the circulation in Bahía de Concepción, Chile, where three field surveys were undertaken during the extended austral summer 2002. Hydrographic and current measurements were compared to local tidal-gauge records. Rough estimates of the barotropic and the baroclinic flow across the transect indicated an unusual vortex circulation during periods of weak wind forcing and strong surface heating; results which were corroborated by numerical simulations.

In this thesis a number of issues related to oceanographic problems have been dealt with on the basis of applying asymptotic methods.  The first study focused on the tidal generation of internal waves, a process which is quantifed by the conversion rates. These have traditionally been calculated by using the WKB approximation. However, the systematic imprecision of this theory for the lowest modes as well as turbulence at the seabed level affect the results. To handle these anomalies we introduced another asymptotic technique, homogenization theory, which led to signifcant improvements, especially for the lowest modes.  The second study dealt with the dynamical aspects of a nonlinear oscillator which can be interpreted as a variant of the classical two-box models used in oceanography. The system is constituted by two connected vessels containing a fluid characterised by a nonlinear equation of state and a large volume differences between the vessels is prescribed. It is recognised that the system, when performing relaxation oscillations, exhibits almost-discontinuous jumps between the two branches of the slow manifold of the problem. The lowest-order analysis yielded reasonable correspondence with the numerical results.  The third study is an extension of the lowest-order approximation of the relaxation oscillations undertaken in the previous paper. A Mandelstam condition is imposed on the system by assuming that the total heat content of the system is conserved during the discontinuous jumps.  In the fourth study an asymptotic analysis is carried out to examine the oscillatory behaviour of the thermal oscillator. It is found that the analytically determined corrections to the zeroth-order analysis yield overall satisfying results even for comparatively large values of the vessel-volume ratio. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.