Search results for "Water level"
showing 10 items of 51 documents
Discharge estimation in open channels by means of water level hydrograph analysis
2010
A new methodology, based on the synchronous measurement of stage hydrographs in two river sections located some kilometers from each other, was developed to estimate the discharge hydrograph in the upstream section. The methodology is based on the one-parameter calibration of a numerical flow routing algorithm, solving the Saint-Venant equations in diffusive or complete form. The methodology was validated using results of laboratory experiments carried out at the Polytechnic of Bari University. A known discharge hydrograph was generated in the upstream tank of a rectangular flume, where two water level sensors were located. Two different bed materials have been used, to account for differen…
Water Level Measurement Locations for Coastal Aquifer Management
2003
The coefficient of variation of the optimal cost (CVOC) method is applied to the Acqua dei Corsari coastal aquifer in Sicily's north coast to find the best point for a new water-level measurement location. The purpose of collecting data from the new measurement location is to reduce uncertainty associated with a stochastic management model for salt-water intrusion control. Assuming that uncertainty mainly stems from spatial variability of permeability, the structural parameters of the stochastic spatial permeability field are estimated using data from a nearby aquifer with similar geological properties. It is first shown through sensitivity analysis that the lack of previous information inh…
Long-term changes in hydrological regime of the lakes in Latvia
2013
Changes in the hydrological regime of the lakes of Latvia depend on natural and anthropogenic causes. This publication summarises the results of the research on the long-term changes in the water level, thermal and ice regimes in the seven largest lakes of Latvia: Liepājas, Usma, Ķīšezers, Burtnieks, Rāzna, Sventes and Lielais Ludzas, and their regional specifics from 1926 to 2002. For most of the studied lakes, the water level has been regulated, except for the lakes Liepājas, Burtnieks and Ķīšezers. Global climate warming has caused considerable changes in the hydrological regime of the lakes during the last decades and the surface water temperature has increased. At the same time, the nu…
Water-level fluctuations in Mediterranean reservoirs: Setting a dewatering threshold as a management tool to improve water quality
2005
Water-level fluctuations, often linked to seasonal climatic trends, are a natural phenomenon which occur in almost all aquatic ecosystems. In some climatic regions, as the Mediterranean one, they are particularly wide due to the occurrence of two well separated periods: the rainy winter and the almost completely dry summer. Precipitation is concentrated in the first period, whereas in the second strong evaporation losses take place. According to these climatic features, and to ensure a continuous supply of water throughout the year, man-made lakes store water during winter and are subjected to dewatering during summer to compensate the lack of precipitation. These ecosystems are thus charac…
Long-Term Consequences of Water Pumping on the Ecosystem Functioning of Lake Sekšu, Latvia
2020
Cultural eutrophication, the process by which pollution due to human activity speeds up natural eutrophication, is a widespread and consequential issue. Here, we present the 85-year history of a small, initially Lobelia&ndash
Red sky at night cyanobacteria delight: the role of climate in structuring phytoplankton assemblage in a shallow, Mediterranean lake (Biviere di Gela…
2009
The hypothesis that climate changes may strongly interfere with the peculiar hydrological patterns in the Mediterranean basin and alter the structure of the aquatic biota was tested in a shallow Sicilian lake. A phytoplankton survey, carried out monthly in the brackish and shallow Biviere di Gela, in 2005–2007, revealed a transformation in the structure of its phytoplankton assemblage as compared with similar data collected in 1987–1988. An analysis of the trends followed by precipitation and temperature over the last 40 years, showed reduced water inflows, due to increased air temperature and evapotranspiration rather than to a decrease in the amount of precipitation. A consequent reductio…
Does lake age affect zooplankton diversity in Mediterranean lakes and reservoirs? A case study from southern Italy
2010
Zooplankton assemblages of 51 lacustrine environments located in the middle of the Mediterranean Region were analysed to evaluate the existence of an ‘age effect’ in determining their structure. The analysed datasets refer to two different geographic areas, one comprising 30 natural and artificial lakes in Sicily and the other an arrangement of 21 analogous aquatic ecosystems located at the bottom of the Italian Peninsula, a more pristine area called Southern Apennine region. Most of the natural lakes are of post-glacial origin. The artificial lakes in both datasets were built in the last century and offer the opportunity to evaluate the possible short-term effects of ageing on the structur…
The end of the Messinian Salinity Crisis in the western Mediterranean: insights from the carbonate platforms of south-eastern Spain.
2010
International audience; How the Messinian Salinity Crisis (MSC) ended is still a matter of intense debate. The Terminal Carbonate Complex (TCC) is a late Messinian carbonate platform system that recorded western Mediterranean hydrological changes from the final stages of evaporite deposition till the advent of Lago-Mare fresh- to brackish water conditions at the very end of Messinian times. A multidisciplinary study has been carried out in three localities in south-eastern Spain to reconstruct the history of TCC platforms and elucidate their significance in the MSC. Overall, this study provides evidence that the TCC formed following a regional 4th order water level rise and fall concomitant…
Toxic cyanobacterial blooms in reservoirs under a semiarid Mediterranean climate: the magnification of a problem
2007
Sicilian reservoirs constitute the most important water resources available on the island. During summer 2001, the intense water utilization of Lake Arancio reservoir reduced the water level significantly. This coincided with the formation of intense blooms formed by the microcystin-producing cyanobacterium Microcystis aeruginosa. During summer 2003, Lake Arancio was continuously filled and the vertical stratification of the water column was maintained, resulting in 5-6 fold lower cell numbers of Microcystis aeruginosa. For both years a significant linear relationship between microcystin net production and Microcysytis cell division was observed, implying that Microcystis cell numbers can b…
Effect of water level and climatic factors on the radial growth of black alder
2011
Effect of water level and climatic factors on the radial growth of black alder Black alder (Alnus glutinosa (L.) Gaertn.) is a widespread tree species in Europe and the western part of the temperate climate zone. The area of forest in Latvia dominated by this tree species has substantially decreased due to wide-spread forest drainage. To predict future changes due to environmental change, it is extremely important to understand the function of ecosystems with black alder and their dynamics. Tree rings can be used as a proxy of past environmental factors. The aim of the study was to determine the effects of meteorological and hydrological factors on radial growth of black alder at two study …