Content uploaded by Ferdinand Schanz
Author content
All content in this area was uploaded by Ferdinand Schanz on Apr 06, 2021
Content may be subject to copyright.
The effects of deep-water siphoning on a small, shallow lake: A long-term case study
... Underwater-light profiles were used to define the layer of 1% surface light intensity calculated from the vertical attenuation coefficient. The mixing depth (z mix ) was calculated from the depth with maximum relative thermal resistance against mixing by individual temperature profiles (RTR; Wetzel, 2001), the stability of stratification in the water column by Schmidt stability according to Livingstone & Schanz (1994). The metalimnetic layer defined as the water stratum of steep thermal gradient demarcated by an almost homoiothermal epilimnion and hypolimnion ( Wetzel, 2001) was calculated by RTR-values and was in average of about 5-8 m for Ammersee in 2001. ...
... Of these, air temperature is arguably the most important (HENDERSON-SELLERS,1988; HONDZO & STEFAN, 1992), as it is not only a critically important causal variable, involved explicitly in most of the processes that determine LSWT (e.g., EDINGER et al., 1968), but has also been shown to be correlated to a certain extent with the other three relevant meteorological forcing variables (LIVINGSTONE & PADISÁK, 2007 ). Thus, short-term fluctuations in LSWT generally reflect short-term fluctuations in air temperature quite well even in extremely heterogeneous (in terms of topography) mountain areas such as the Swiss Alps (LISTER et al., 1998; LIVINGSTONE & SCHANZ, 1994; LIVINGSTONE et al., 1999), and many studies have shown that LSWT can often be modelled well empirically in terms of air temperature alone (e.g. MCCOMBIE, 1959; WEBB, 1974; SHUTER et al., 1983; MATUSZEK & SHUTER, 1996; KETTLE et. ...
In 25 lochs in the Grampians and Northwest Highlands of Scotland, miniature thermistors with integrated data loggers were employed in 2000 and 2001 to measure lake surface water temperatures (LSWTs). Results indicate that LSWTs fluctuate coherently in response to climatic forcing, and that additionally, they differ little in an absolute sense, implying that daily mean LSWTs can be upscaled easily. Regional coherence in LSWT is substantially higher in summer and autumn than in winter and spring. LSWT decreases approximately linearly with increasing altitude above sea level during winter and spring, but not otherwise; this contrasts strongly with the results of studies in other mountain regions, which show the most pronounced linear decrease in LSWT with altitude to occur in summer. LSWT showed no dependence on latitude at any time of the year, but showed a significant dependence on longitude which can be interpreted as distance from the maritime influence of the Atlantic especially during autumn and spring. In summer, no consistent dependence of LSWT on either altitude, latitude or longitude was found, implying that any differences in LSWT that may exist among the lochs in summer are predominantly the result of lake-specific local effects. The duration of the period during which LSWT ≤ 4°C depends on altitude and longitude, but not on latitude. The timing of the onset of this period in autumn occurs essentially simultaneously throughout northern Scotland, whereas the timing of the end of the period in spring becomes later with increasing altitude and increasing distance towards the east. This suggests that the duration of inverse stratification or circulation at temperatures less than the temperature of maximum density will tend to be less in low-lying lochs and/or lochs close to the Atlantic coastline than in high-altitude lochs and/or lochs located further from the Atlantic coast, and that this difference is entirely due to differences in climatic forcing that occur in spring. © 2009 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart.
... [10,11,14]. Different attitude and actions have been taken, including attempts to limit the loads of discharged pollutants from point and surface sources [5,6,13]. Another approach is interference in biological activities by modifi cation or enhancing, the natural processes occurring directly in the water bodies. ...
The inter-reservoir enrichment phenomenon was exploited to curtail the reservoir eutrophication process. The Plawnowice reservoir (South Poland Upper Silesia Region) has an area of 225 ha, volume of 29 mln m(3), and a depth of 15 meters. According to the monitoring results in the years 1993-1998 the reservoir was qualified as hypereutrophic. Beginning in December 2003 a bottom pipe for hypolimnetic withdrawal was installed. In the period 2004-2010 a negative phosphorous balance was achieved. The discharge load of total phosphorous was in the beginning twice as high as the inflowing. During the first eight years with an inflow of 75 Mg P, the removed load of total phosphorus was 103 Mg P. In effect the net balance was 28 Mg P. The load, in respect to the surface area, of 2.2 to 3.3 gP/m(2) per year, was reduced to a negative load of - 0.48 to - 3.3 gP/m(2). The hypolimnetic maximum concentration of orthophosphates equal to 1.254 mg P-PO4/dm(3) in 2004, was reduced to 0.236 mg P-PO4/drn(3) in 2011. The respective factors and rate of eutrophication curtailing, including changes of phosphorus compounds have been discussed. Also changes of pH and visibility of the Secchi disc are presented. It was concluded that the presented method of hypolimnetic withdrawal is a lasting and effective process.
... with Y t = value at time t, Y = mean of the series and S Y = standard deviation of the mean. Schmidt stability was calculated according to Livingstone and Schanz (1994). ...
The cyanoprokaryote Planktothrix rubescens has been studied for over four decades in an alpine lake, Mondsee, Austria. We hypothesise that impacts of climate change can be distinguished from other environmental constraints controlling its population dynamics. During thermal stratification, P. rubescens formed a deep chlorophyll maximum in the metalimnion. Seasonal and diurnal depth distributions indicated that Planktothrix lived well below the euphotic zone, at low light levels and moderate temperatures. Photosynthetic parameters indicated a shade adapted population. The eutrophication and rehabilitation periods of Mondsee were characterised by fluctuations controlled by phosphorus, with periods below the P-threshold associated with low biovolumes and relatively stable populations. Positive net changes of Planktothrix biovolume occurred during the spring–summer transition and in autumn. During summer, the population usually declined to an annual minimum. The standardised residuals of annual biovolumes responded positively to the climate signal of the Winter North Atlantic Oscillation and the timing of the onset of stratification. An inverse relationship existed between off-set and persistence of stratification. P. rubescens only benefits from climate warming early in the year, during late spring overturn and early summer. Longer periods of summer stratification did not favour biovolume development.
The two volumes of this handbook provide a comprehensive account of the emerging and vibrant science of the ecological restoration of both habitats and species. Ecological restoration aims to achieve complete structural and functional, self-maintaining biological integrity following disturbance. In practice, any theoretical model is modified by a number of economic, social and ecological constraints. Consequently, material that might be considered as rehabilitation, enhancement, re-construction or re-creation is also included. Principles of Restoration defines the underlying principles of restoration ecology, in relation to manipulations and management of the biological, geophysical and chemical framework. The accompanying volume, Restoration in Practice, provides details of state-of-the-art restoration practice in a range of biomes within terrestrial and aquatic ecosystems. The Handbook of Ecological Restoration will be an invaluable resource to anyone concerned with the restoration, rehabilitation, enhancement or creation of habitats in aquatic or terrestrial systems, throughout the world.
Lake Kortowskie is restored by the hypolimnetic withdrawal method: rich in nutrients near-bottom waters are removed by a pipeline directly to the outflow instead of the natural outflow of surface waters. It has been found out that the amount of water discharged through the pipeline and therefore the amount of removed phosphorus depends on the surface inflow. The water balance of the lake in summer is unfavourable whereas the phosphorus balance very favourable. The latter is determined by the diminishing phosphorus loads entering the lake, and by the increasing amounts of phosphorus released from the bottom sediments. Any disturbance at the interface bottom sediments-overlying water results in continuous release of "new" phosphorus amounts to the water. In the same time near-bottom water withdrawal to the outflow cause deficiency with this element in the lake ecosystem. For optimising the restoration process such rate of pipeline outflow should be established, to reach maximal phosphorus removal at an existing hydrological balance.
This study represents the first attempt to estimate internal phosphorus (P) loading over many years in polymictic eutrophic Lake Winnipeg, Manitoba, North America's 7th largest lake. Using long-term data, internal load was quantified by several approaches in Lake Winnipeg's North and South Basins and the connecting Narrows. Internal P loading occurred almost every year in the summer and fall and perhaps under ice in the winter during the study period 1999–2012 and even before (probably as early as a decade before 1969). Several independent approaches (Lint_1, in situ estimates involving TP concentration changes, Lint_2, mass balance, and Lint_3, based on sediment P release rates and active release area) identified an appreciable loading from the sediments that is consistent with redox related processes. Mean gross internal load (Lint_2 and Lint_3) was about 1.3 times the external load for the whole lake in 1999–2012, while the net estimate (Lint_1) was 0.75 times. Internal loads varied between basins: South Basin contributed 18–23% to total internal load and the Narrows about 16–20% for approaches Lint_1 and Lint_3, while South Basin and Narrows combined contributed about 21% in the mass balance approach (Lint_2). North Basin contributed 57–79% to total internal load. Internal load from upstream sections probably affects the North Basin because of the relatively high flushing rate. The potential effect of internal load on phytoplankton and cyanobacterial biomass is highlighted by several significant positive correlations. Internal load can be expected to rise because forecasted regional climatic warming will increase sediment oxygen demand and P release.
The inter-reservoir enrichment phenomenon was exploited to curtail the reservoir eutrophication process. The Plawnowice reservoir (South Poland – Upper Silesia Region) has an area of 225 ha, volume of 29 mln m3 , and a depth of 15 meters. According to the monitoring results in the years 1993 – 1998 the reservoir was qualified as hypotrophic. Beginning in December 2003 a bottom pipe for hypolimnetic withdrawal was installed. In the period 2004 – 2010 a negative phosphorous balance was achieved. The discharge load of total phosphorous was at the beginning twice as high as the inflowing. During the first eight years with an inflow of 75 Mg P, the removed load of total phosphorus was 103 Mg P. In effect the net balance was 28 Mg P. The load, in respect to the surface area, of 2.2 to 3.3 gP/m2 per year was reduced to a negative load of – 0.48 to – 3.3 gP/m2. The hypolimnetic maximum concentration of orthophosphates equal to 1.254 mg P-PO4/dm3 in 2004, was reduced to 0.236 mg P-PO4/dm3 in 2011. The respective factors and rate of eutrophication curtailing, including changes of nitrogen compounds have been discussed. Also changes of pH and visibility of the Secchie disc where presented. It was concluded that presented method of hypolimnetic withdrawal is a lasting and effective process.
Chain Lake is a small ( 46 ha), shallow (mean depth 6 m, max depth 9 m) eutrophic lake in the interior of British Columbia. Canada. It suffers from severe blue-green algae blooms fed by internally loaded phosphorus. A hypolimnetic withdrawal system began operation in 1994, and is operated annually during the ice free period of the year. It is gravity driven (no mechanical pumps) and can operate at rates up to 80 L· s·1. A monitoring program implemented as part of the withdrawal installation evaluated total phosphorus export, lake water quality effects, and downstream environmental impacts. The withdrawal does not accelerate hydraulic flushing of the lake (residence time 0.5-3 years) but preferentially drains the water column below 5 m every 100 days and drains the deepest region of the lake (6-9 m) approximately every two weeks. Total phosphorus export in the first year of operation was 30 kg, and optimization of the operation strategy should increase export to 60 kg per year, resulting in a net export of total phosphorus from the lake. Long term monitoring of water quality has been performed by resident volunteers for nine years ( 1994 - 2002) using Secchi measurements. Only a few data are available prior to the withdrawal operation. A nonparametric trend test found statistically significant increases of the monthly median Secchi depth for June (p<O.05) and August ( p<O.10). Optimization of the withdrawal operation to maximize phosphorus export can be done by earlier start-up after ice off and increasing flow rates during the most anoxic periods. Downstream concerns with respect to the withdrawal operation include: dissolved oxygen depletion observed at the withdrawal site and up to 500 m downstream; nutrient enrichment with elevated concentrations of phosphorus observed in the withdrawn water; and elevated levels of ammonia, iron, and manganese observed in the withdrawn water in the first year of monitoring. The effects of anoxic water discharge were partially mitigated by a fountain aerator at the discharge point which increased the dissolved oxygen in the withdrawal stream by up to 2.0 mg L-1 •
The moss, Warnstorfia exannulata (Schimp.) Loeske, was first reported forming a carpet beside a water pool in Ny-Ålesund (78°56′N), Svalbard in 1959. Fifty years later, in 2008, it was found growing as an aquatic in a pool. The moss is sensitive to seasonal changes and exhibits a pattern of seasonal growth: summer stems with densely arranged leaves and lateral branches, and winter growth with short-leaved stems and no lateral branch. The mean daily increase in stem length is 0.68 mm in summer and 0.07 mm in winter. The longest specimens were up to 8 years old. The growth of the moss reflects closely seasonal temperature and growth conditions. World distribution is discussed and global distribution mapped.
ResearchGate has not been able to resolve any references for this publication.