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1.
On the basis of different sets of aerial photos the dynamics of the reed bed areas of Lake Constance were investigated in relation to the dynamics of the water levels. The objectives of the study were to quantify the changes of reed areas due to different flood events in the last decades and their recovery in the time periods between these events. The results should given information of the relevance of water level variations on reed bed dynamics and the regeneration times of reed beds after extreme disturbance events.Following the extreme flood at Lake Constance in 1999 the reed belts of Lake Constance lost approximately 30 ha (24%) of the lakeside reed beds. The loss is comparable to the situation in the late 1960s, when approximately 40 ha died back due to the extreme flood in 1965 and the high spring water levels in the subsequent years. In the time period between the extreme floods of 1965 and 1999, the reed areas expanded to nearly 85% of the area before 1965. The expansion rates increased with increasing distance to the flood event of 1965. Especially in periods with series of years of low spring water level the expansion rates were high.The damage degrees of the reed areas in the years 2000 and 2002 showed a clear relation to the elevation (i.e. average water level) of the stands. The damage degree increased with decreasing elevation. Furthermore the regeneration process of severely damaged stands was related to the elevation level of the stands. Whereas stands at high elevation regenerate fast, those at low elevation died off completely in the years after the extreme flood. This supports the hypothesis that the water level flutuations play a major role in the reed dynamics of Lake Constance.As a consequence of the climate change an increase in the frequency of high spring water levels is expected. Thus, it seems unlikely that reed stands will ever expand again to the same area as before 1965.  相似文献   

2.
Oxygen uptake rates by the sediment have been determined in a natural stratified sediment-water system from Lake Constance (Obersee, max. depth). After oxic preconditioning of the system the uptake rates ranged between 855 and 1,062 mg·m?2·d?1; after anoxic preconditioning of the system they ranged between 3,405 and 3,794 mg·m?2·d?1. These data, and the electron activity buffer capacity and oxygen consumption intensity as found in Lake Constance profundal water, show that the oxic-anoxic transition will happen here at the earliest after 142 days (about 4.5 months) of total oxygen isolation. Reoxygenation requires at least 3.7 times higher O2 input than supposed for a ‘normal’ winter circulation in Obersee.  相似文献   

3.
The laser‐induced breakdown detection (LIBD) is a very sensitive method for the direct detection of colloids based on the plasma generation on single particles by a focused, pulsed laser beam and the detection of the produced shock wave or plasma light emission. For the determination of colloid sizes the light emission of single plasmas is detected by a microscope CCD‐camera system. With known mean particle diameter and breakdown probability the particle concentration can be calculated. The application of the LIBD to monitor the change of colloid concentration and size during the purification steps of drinking water at the Bodensee (Lake Constance, Germany) water purification plant is shown. The breakdown probability, correlating to colloid number density, decreases with every purification step. By addition of FeCl3 as a precipitating agent and with an additional filtration step, not only suspended matter, but also colloids are effectively removed. After this process a remaining particle concentration of 50 ng/L and a mean particle diameter of 27 nm are found.  相似文献   

4.
The density of river waters running into Lake Constance and that of different layers of the Lake itself are calculated and compared. The amount of riverine waters that contribute to the different water layers of the lake is estimated. It is concluded that from April to November the main portion of the riverine waters runs below the thermocline.   相似文献   

5.
A method for the trace-level determination of bromate in raw and drinking water is reported. The procedure combines the quantitation of bromate by ion chromatography with a concentration step which in the main is composed of an unselective enrichment of all water constituents by means of a rotatory evaporator and a selective removal of the chloride ions. With this method, the reliable determination of bromate in raw and drinking waters is possible down to concentrations of at least 1 μg/L. The method is used for systematic examinations in several German waterworks which use ozone for the preparation of drinking water. The resulting data clearly prove that during the ozonation of bromide-containing waters, bromate is produced, whereby the concentration of bromate in the ozonated raw water can exceed 10 μg/L. Some correlations between the amount of bromate and the respective conditions of ozonation are pointed out.  相似文献   

6.
The chloride concentration in Lake Constance, by volume the second largest lake in Europe, has increased by a factor of 2.4 during the past 40 years. Based on a chloride budget for the year 2006, we estimated total chloride imports to the catchment at 101 kt year−1. Road deicing salts contributed 52%, waste water 23%, farming 11%, soil weathering 9%, precipitation and solid waste incineration 3% to this import. River monitoring programs in Switzerland, Germany, and Austria in 2006 traced an average total chloride export from the catchment into Lake Constance of almost 70 kt and an export from the lake of 56 kt. About one-third of this load to the lake originated from the Alpine Rhine catchment (Switzerland), and about 60% from various smaller tributaries in Austria and Germany. The average annual import of chloride to Lake Constance for the years 1995–2007 was 60 kt, the export almost 57 kt. This budget is in good agreement with the observed increase in the chloride content of the lake and thus confirms the appropriateness and quality of the long-term monitoring program conducted by Swiss, German and Austrian laboratories. For the year 2006, we estimated that about 65% of the chloride spread onto roads for deicing and manure on cultivated land reached the lake within the year of their application. The missing 35% remained transiently in the soil and groundwater of the catchment.  相似文献   

7.
Previous genetic studies on perch (Perca fluviatilis L.) in northern and southern regions of Europe have shown low heterozygosity. No such investigation has been conducted in the central part of Europe. The genetic variability ofP. fluviatilis in four Swiss lakes (Lake Constance, Lake Zürich, Lake Geneva and Lake Maggiore) was investigated. These four lakes belong to three different drainage systems (Rhine, Rhone and Po) without connections. A total of 136 fish were analysed electrophoretically. Only one locus (SOD *) was highly polymorphic in Lake Constance among the 27 loci studied. The expected heterozygosities for each population and for the total population were higher than in the previous studies but low (H S= 0.38–2.7%;H T=1.22%) and Nei's genetic distances were small (0.000–0.003). However, the jack-knifed mean of the Wright'sF STwas calculated as 0.142, which indicates modest genetic differentiation among the perch populations in Switzerland, due to the differentiated population in Lake Constance.  相似文献   

8.
The Ponto-Caspian mysid Limnomysis benedeni was first recorded in Lake Constance in summer 2006, and a stable population developed at the site of discovery. Although this mysid is common in the Rhine and Danube rivers, little is known about its ecology and impact in systems of invasion. We investigated the autecology of L. benedeni in habitat-choice and food experiments. In the habitat-choice experiments, highly structured habitats, i.e., stones covered with zebra mussels (Dreissena polymorpha), macrophytes, and especially stonewort, were strongly preferred. In food experiments, L. benedeni fed mostly on food sources with a small particle size, e.g., biofilm on leaf litter, biodeposited material of zebra mussels, epilithon, and phytoplankton. We also compared the L. benedeni population data from Lake Constance with that from rivers. In Lake Constance, female L. benedeni were nearly 30% larger and carried more than three times more eggs in spring (9.4±0.6 mm and 28.4±5.7 eggs) than in summer (6.7±0.8 mm and 8.7±2.9 eggs). The mysids present in spring might be the generation that over-wintered; in summer, this generation was probably replaced by a new generation of smaller individuals. The large brood size and the detritivorous feeding strategy might allow L. benedeni to colonize Lake Constance rapidly.  相似文献   

9.
Formation of Artefacts and its Suppression during the Determination of Volatile Halogenated Hydrocarbons in Water by Means of Headspace Gas Chromatography under the Standard Conditions of DIN 38407-F5. Part II: Increased Trihalomethane Formation in Chlorinated Swimming-pool Water A comparison of two analytical standard procedures for the determination of trihalomethanes (THM) in water (headspace gas chromatography and pentane extraction/gas chromatography) yielded strongly differing results. Under the conditions recommended by the German Standard Method DIN 38407-F5 (60…80°C for at least 60 min) degradation of thermo-labile chlorination products occurs resulting in elevated THM concentrations. The reactions involved are partly pH-dependant, and these can be suppressed by sample acidification. The degradation of trihalogen acetic acids, however, can only be influenced by minimizing the equilibration time and temperature. Other intermediate chlorination products (haloacetonitriles) are also degraded to THM after preceding hydrolysis to the corresponding carboxylic acids. Comparative results obtained with a purge and trap method at ambient temperature, i.e. without thermal stress during the enrichtment step, are lower than with static headspace GC but still high in comparison to the pentane extraction method. Presumably volatile THM-precursors are also trapped and subsequently decomposed upon thermal desorption from the trap. As the static headspace GC is the most rational method of LHKW determination available, the recommended experimental sample handling conditions should be modified in a way that deterioration reactions are reduced as far as possible.  相似文献   

10.
The suspended solids taken out of the affluents of Lake Constance have been isolated and the concentrations of C, N, P, Ni, Cr, Cd, Zn, Co, Fe and Mn within the material have been determined. The loads in every river were calculated by the relations between water discharge, concentration of suspended matter and concentration of the elements. Test showed, that the material from the Bregenzer Ach and the Neuer Rhein adsorb phosphate out of the water. The suspended solids of the other rivers give phosphate to the water.

hier: Sinkstoffe=Schwebstoffe.  相似文献   

11.
Murchison Bay in the Northern part of Lake Victoria has for decades received a daily wastewater load of 0.2% of its volume from Kampala City, through the Nakivubo channel. In spite of this, the Water Treatment Works abstracts raw water from this bay and has been able to produce drinking water of sufficient quality for the capital. This study monitored various physical−chemical components within the bay during 2000−2003 to understand the processes responsible for the acceptable quality of raw water. Four sampling stations were located along a transect from the channel mouth towards the open lake.Resultsshowed that the wastewater did not accumulate in the bay, instead was already strongly diluted 2.5 km from the channel mouth. This caused an abrupt reduction in conductivity and the concentrations of the nutrients total phosphorus (Tot-P), orthophosphate (PO4-P) and total nitrogen (Tot-N).Inshore−offshore exchange of water was mediated by flows from daily and sub-daily water level fluctuations and wind-driven currents. As a daily average, 2% of the Murchison Bay flowed in and out and the incoming wastewater was diluted 9.7 times.During the dry season from June to August (D2), when the weather was influenced by the south-east monsoon, the thermal stratification in the main lake disappeared and cooler and deoxygenated water from deeper depths entered the bay influencing its water quality.The daily flushing of water in and out of the bay due to water level variation was identified as the main factor diluting the bay water.  相似文献   

12.
The current and future state of the Earth’s water resources under present-day trends in water use is discussed. The activity of international institutions in the organization of management of lake ecosystems and drainage basins was analyzed from the viewpoint of sustainable development. The work of International Committee on Lake Environment, International Joint Commission (USA and Canada), International Commission on Lake Constance Protection, Autonomous Bilateral Management of Lake Titicaca, Commission on Chad Lake Basin, and Fishery Organization of Lake Victoria. Recommendations are proposed for the organization of international management of water bodies and their drainage basins.  相似文献   

13.
The Deschampsietum rhenanae is an endemic and endangered lakeshore community growing in the upper littoral of Lake Constance, the occurrence of which has been reduced dramatically during the last 100 years. The existence of this community depends on the seasonal water level changes of the unregulated, prealpine Lake Constance. Long-term monitoring indicates that the typical species of the Deschampsietum rhenanae and their competitors may be strongly affected by extreme water levels. An earlier onset of the water level increase in spring could potentially pose a threat to the Deschampsietum rhenanae, especially if the water level rises before seed ripening in the Deschampsietum rhenanae.  相似文献   

14.
The population dynamics and distribution of Daphnia pulicaria were studied in Lake Constance (Lower Lake). This Daphnia was absent in the year 2004, absent during most part of the year 2005 and absent in spring 2007 but present from November 2005 to July 2006. Abundance was high from January to late May of the year 2006; maximum abundance was 95,000 ind. m−2 (30 May). Males and ephippial females were observed in January and late May. Ovigerous females constituted between 30% and 70% of adult females from November 2005 to April 2006; in June and July their percentage decreased to <20%. Mean number of eggs per egg-bearing female ranged between 2 (in November 2005) and 9.8 (in April 2006) and maximum egg number was 20. Birth and growth rates were low (generally <0.15); death rate was highest in June (0.275). Females of D. pulicaria were larger than females of Daphnia galeata/hyalina but carried somewhat fewer eggs. D. pulicaria generally preferred the deep cool water layers. The species was abundant in the northern parts of the Lower Lake (Gnadensee and Zeller See), rare in the southern parts (Rheinsee) and absent in the Upper Lake. We conclude that the life history and occurrence of large-bodied D. pulicaria in Lake Constance can be governed by fish predation pressure. This suggestion is supported by analyses of stomach contents from Coregonus lavaretus; stomachs contained high proportions of D. pulicaria in the first half of the year 2006. The disappearance of D. pulicaria in early summer and the comparatively low proportion of adults for most part of the investigation period also indicate that fish predation is involved in the dynamics of this Daphnia. The preference for deep cool water can be strategy to reduce predation risk. The low density of D. pulicaria in the southern basin of Lower Lake (Rheinsee) may be explained by the influence of the Rhine River which flows through this basin.  相似文献   

15.
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16.
“引江济淮”工程对安徽菜子湖水龄分布的影响   总被引：2，自引：1，他引：1  
菜子湖是"引江济淮"工程的重要输水通道,其水体输运和物质交换将因输水工程发生改变.本文基于环境流体水动力学模型（EFDC）建立了菜子湖水龄模型,在将模型与实测水文数据验证满足精度的前提下,设计14种方案计算菜子湖在季风影响下的水龄,工程实施期间菜子湖在丰、平、枯季的水龄与流场,以及枯水季调水情景下同风速8种风向和强风向3种风速时的水龄.数值试验的模拟结果表明：菜子湖湖体水龄分布具有时空差异性,无风条件下,春、夏、秋、冬季的湖体的平均水龄分别为120.93、33.19、92.92、101.48 d,而在季风影响下,春、夏、秋、冬季平均水龄分别为75.23、32.45、81.80、66.16 d;西部L2湖水龄较长,东部L1湖和南部L3湖水龄较短;输水工程将改变L1和L3湖的流场,对L2湖流场几乎无影响;输水工程实施后,菜子湖水龄分布主要受风场及输水影响,不同风向对菜子湖各湖区影响不同,西南风有助于L1湖水体交换,北风有助于L2湖水体交换,东风有助于L3湖水体交换,而当风向为东北风时,3个湖区水龄均较小;枯水季调水有利于L1湖和L3湖水体交换,但对L2湖水体交换作用不明显.  相似文献   

17.
Despite decreasing nutrient loading of Lake Constance over the past few years, annual sedimentation rates of dry matter remained nearly constant at a level of about 1000 gm–2y–1. The phosphorus content in settling material varied between 0.13 and 0.22% of dry weight. Phosphorus was transported to the lake bottom mainly by POM and by coprecipitation with authigenically formed calcite (estimated from results of laboratory studies). Adsorption to sinking particles of allochthonous origin was of minor importance. The effect of a self-cleaning mechanism is discussed with regard to continuously declining contents of dissolved phosphorus in Lake Constance since 1981, due to external sanitation measures in the drainage area.  相似文献   

18.
东太湖水环境现状及保护对策   总被引：17，自引：4，他引：13  
根据2002年4月至2003年4月东太湖的水质监测结果,分析了东太湖的水质现状、空间分布特征及变化趋势．其中TN变化范围0．57-3．91mg／L,平均值1．61 mg／L,NH4 -N变化范围0．01-0．42mg／L,平均值0．14mg／L,NO3--N 变化范围0．044-0．549mg／L,平均值0．16mg／L,而TP平均值为0.103mg／L,与以前的调查结果相比,TN、TP和NH4 -N 均明显增加,CODMn有所下降,水质状况总体较差,但不同水域因其影响因子不同,水质亦有明显差别,湖心区水质最好．目前,东太湖水体总体上处于中富营养状态,部分湖区已达到富营养状态．最后根据东太湖水环境的现状,提出一些措施和建议．  相似文献   

19.
In the chlorination of drinking water about 90% of chlorine show an oxidizing effect, 10% result in halogenated reaction products, ca. 1% of them consisting of trihalomethanes. When chlorine dioxide is applied, in most the trihalomethanes remain below the detection limit, but increasingly polar organic reaction products originate, on the other hand. Chloramine is rarely applied, mostly for securing transport with storage reservoir waters. Only little information about reaction products is available. By the application of ozone one obtains a wide spectrum of reaction products, the aldehyde contents can be influenced by activated carbon. Especially critical is the formation of persistent epoxides, above all from pesticides. Due to antimon burners, the ultraviolet irradiation is gaining in interest, and in many cases its biocidal effect is superior to that produced by chlorination and ozonization, except for the problem of re-germination in the water supply network. The costs of ultraviolet irradiation, however, are much higher than those of the other techniques, of which chlorination causes only about one quarter of the costs of the other chemical disinfection techniques.  相似文献   

20.
Concomitant with the increased eutrophication observed during the last 20 years in Lake of Constance, also an increase of saprobity was expected. To prove this, viable counts of zymogenic heterotrophic bacteria (TVC) as well as of fecal indicators were determined in vertical profiles during the cycle of a year and compared with concomitant concentrations of dissolved organic matter (DOM). There was an inverse relationship between DOM and epilimnetic peaks of TVC, but also between DOM and viable counts of Cytophagaceae, which were most abundant at low water temperatures. The average epilimnetic TVC-values exceeded comparable 20 years old data by a factor of 10. On the other hand, fecal Coli and Streptococci, by accumulating in the bottom water, showed mostly a distribution which was reverse to earlier findings of this group and recent distribution patterns of TVC as well. Altogether, the results support the view that the abundance of zymogenic bacteria in Lake of Constance is mainly controlled by its epilimnetic primary production of degradable organic matter.  相似文献   

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