Winter Low Water Research Articles

Geographical specificity of the river’s regime in Bulgaria

This paper presents the types of river regime based on the three characteristics and two categories. The types are isolated from the number of cases with a high water and low water phases. The subtypes were detached from the duration of a high water and low water phases. There are three types (and seven subtypes) of river regime in Bulgaria. Mildness-Continental type is with spring high water phase, summer-autumn low water phase and transitional water during winter. Continental-Mediterranean type is with winter-spring high water phase and summer-autumn phase of low flow. Transitional type is with spring-summer high water phase and increase in flow during November and December, steady low water phase from July (August) until October and with the winter low water phase.

Aspects of the biology of Salicornia bigelovii Torr. in relation to a proposed restoration of a wind-tidal flat system on the south Texas, USA coast

Wind-tidal flats are the dominant coastal wetland type in southern Texas, USA. Succulent vascular plants are colonizing the flats in some locations, often where past dredge disposal along navigation channels and other activities have interrupted natural water communication between hypersaline bays and large areas of wind-tidal flats. The objective of this study was to test the feasibility of proposed removal of a causeway at Laguna Atascosa National Wildlife Refuge to restore the historic hydrologic regime and eradicate encroaching vascular plants, mostly Salicornia bigelovii, on the assumption that high sediment salt excluded these vascular plants under natural conditions. Assessment in spring 1998 of the density of Salicornia in relation to elevation and sediment salt of bare and vegetated zones on the vegetated flats on one side of the causeway and entirely barren flats with unimpaired connection to Laguna Madre on the other side of the causeway suggested that sediment salt > 0.1 g ml−1 excluded vascular plants. However, bimonthly sampling in 1999–2000 revealed that sediment salt concentrations were > 0.1 g ml−1 throughout the vegetated zone in July and more locally in the period of winter low water, with little impairment to established plants. This indicates that if control is desired, it must be exerted at germination and early establishment during and after fall high water. Continuous monitoring of water levels on either side of the causeway suggests that, even with removal of the causeway, flooding with hypersaline lagoon water will be too infrequent to counteract the freshening effect of a permanent hydraulic connection to the main agricultural drain of the lower Rio Grande Valley that has developed at the other end of the salt flat. Monitoring Salicornia distribution over six years documented huge variation between years but no trend toward increasing dominance of the flats. The results of this study illustrate that the most obvious alterations to a site may not be the most influential on function and that the scale of analysis may have to extend far beyond the site in space and time to evaluate a proposed restoration properly.

Mass‐dependent energetics and survival in Harbour Seal pups

Summary Winter survival rate in Harbour Seal pups is significantly correlated with the autumn body mass of pups. Multi‐type mark–recapture statistics were applied to individual re‐sighting histories of branded seals, and survival probability was estimated with weight as a covariate. The probability of surviving to an age of 1 year is only 0·63 for the smallest pups at 17 kg, whereas pups at 32 kg have a survival probability of 0·96. An energetic model for juvenile Harbour Seals reveals how metabolic rate is related to body mass, skin surface area, blubber thickness and water temperature. There is an increasing thermal stress with decreasing body size of pups. Low winter water temperatures induce a negative energy balance in small pups, which is a probable cause of the observed mass‐dependent survival. This study explicitly links a physical property of the environment, sea‐water temperature, to energetics and life history. The approach opens possibilities for studying aspects of life‐history evolution, such as optimal weaning weight and pupping time, in marine mammals.

Overwintering Yellow Perch Fry in Alabama

Abstract Wild harvests of yellow perch Perca flavescens have failed to keep up with the strong market demand for the fish. Moreover, yellow perch has many attributes that make it attractive for commercial aquaculture in the USA. One drawback to yellow perch culture in the north-central region of the United States is that low winter water temperatures inhibit somatic growth. In this study, yellow perch juveniles were stocked at three densities (30, 60, and 90 per tank) in 600-L tanks in Auburn, Alabama, in early January and maintained throughout the winter until mid-April. Water in the tanks was circulated through an earthen pond and returned to the research system by means of a water pump. Tanks were aerated by means of submersible air diffusers and a regenerative air blower. Fish were offered a commercial, slow-sinking feed at 5% of body weight, and temperature was measured hourly by a remote data logger. Survival was greater than 99% in all treatments. When water temperature was below 20°C, absolute gro...

Seasonal Ichthyodiversity and Growth Patterns of Juvenile Flatfish on a Nursery Ground in the Southern Bight of the North Sea (France)

The demersal fish community on a flatfish nursery ground, of the Southern Bight of the North Sea, was sampled monthly between May 1998 and 1999. The studied coastal area is a multispecific nursery area. Although 32 fish species were caught, only nine species had a major influence on the variation in total densities through the year and can be considered as key species. Juvenile sole and plaice exhibited similar seasonal growth patterns with rapid growth during late spring and summer, a growth arrest during autumn and winter and a restart of growth in March. Comparisons of observed growth in length with predicted maximal growth under optimal food conditions suggested that during the summer, growth of 0-group sole and plaice was only determined by prevailing mean water temperature. During autumn and winter, while growth in length of sole followed model predictions, observed length of plaice was less than model predictions, suggesting growth limitation. Analyses of the factors that may be responsible for differences between observed and expected length growth indicated that autumn and winter growth arrest of plaice was not only related to low winter water temperature. It is suggested that for visual feeders such as plaice, the interaction of decreasing food availability and day length during autumn and winter can reduce the access to food resource and therefore feeding success and growth.

The effect of wood and temperature on juvenile coho salmon winter movement, growth, density and survival in side‐channels

AbstractIn British Columbia, side‐channels have been built to compensate for lost salmonid habitat. Most are structurally simple with little in‐stream wood; however, they support high densities of juvenile coho salmon. We longitudinally divided in halves the top 100 m of two dead‐end artificial side‐channels, one side‐channel with low winter water temperatures (surface‐fed) and one with relatively higher water temperatures (groundwater‐fed), closed the downstream end of each side‐channel with two‐way traps, and treated only one half of each channel with bundles of wood. Trapped fish were marked daily and coho salmon movement, growth and smolt output were monitored for two years. Wood addition increased juvenile coho winter carrying capacity and spring smolt output only in the ‘colder’ surface‐fed side‐channel. In contrast, in the groundwater‐fed side‐channel, with relatively higher water temperatures, the wood treatment slightly reduced the channel's carrying capacity and the spring output of coho salmon smolts. Copyright © 2003 John Wiley & Sons, Ltd.

Preliminary reports from the Caulerpa taxifolia invasion in southern California

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 233:307-310 (2002) - doi:10.3354/meps233307 Preliminary reports from the Caulerpa taxifolia invasion in southern California Susan L. Williams*, Edwin D. Grosholz Department of Environmental Science and Policy and Bodega Marine Laboratory, University of California at Davis, PO Box 247, Bodega Bay, California 94923-0247, USA *E-mail: slwilliams@ucdavis.edu ABSTRACT: We report the first preliminary in situ observations of the invasive strain of the tropical green seaweed Caulerpa taxifolia in Huntington Harbor, California. Although patch size had regressed from the previous, presumably summer, extent, C. taxifolia exhibited new frond growth within patches despite low winter water temperature. The growth patterns, size of fronds, density, and biomass were similar to those reported from other invasion sites in the Mediterranean Sea and Australia. The seagrass Ruppia maritima also grew at the site. In patches mixed with C. taxifolia, the biomass of R. maritima was 20 times lower than in patches without C. taxifolia. KEY WORDS: Invasive species · Caulerpa taxifolia · Ruppia maritima Full text in pdf format PreviousExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 233. Online publication date: May 21, 2002 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2002 Inter-Research.

Spatio‐temporal variability in abundance of the parrotfish, Sparisoma cretense, in SE Apulia (SE Italy, Mediterranean Sea)

Spatio‐temporal variability in the abundance of the parrotfish, Sparisoma cretense, was investigated along the SE Apulian rocky coast (SE Italy, Mediterranean Sea). Underwater visual census surveys were carried out in three different times (August 2000, March 2001 and May‐June 2001) at four locations between Otranto (Lower Adriatic) and S.M. di Leuca (Ionian Sea), at three sites at each location, and at four depth levels from the surface down to about 30 m. The species was never observed near the surface nor in the deepest zones, while it was more abundant at 12–15 m (mean ± SE: 0.69 ± 0.05 individuals 100 m‐2) than at 5–7 m depth (0.27 ± 0.04 ind. 100 m‐2). This general pattern was observed during all three sampling times and at each location surveyed. Significant differences in the abundance of S. cretense were detected among depths, locations and, to a lesser extent, among times, while no differences were observed among sites within locations. This study provides evidence that, besides a given variability over a spatial scale of kilometres (i.e., among locations), this fish lives exclusively between about 5 and 15 m depth, suggesting that it could have specific habitat requirements in terms of physical conditions (e.g., water temperature, wave action) and substrate features (e.g., benthic cover). In addition; taking into account that juvenile parrotfishes appeared for the first time in August 2000 along the coast of SE Apulia, where neither adults nor juveniles had been previously recorded, these data could support the hypothesis that S. cretense is establishing a true population in this region. The results presented here, in fact show that the low winter water temperature did not affect survivorship of this ther‐mophilous fish.

Epilithic diatom communities during the colonization of artificial substrates in the River Garonne (France). Comparison with the natural communities

Along 200 km of the River Garonne (France), epilithon colonization of artificial substrates was followed over a four week period in eight sites with different human influences. Salinity and nutrient concentrations increased progressively downstream, but polluted sites and reservoirs acted as discontinuities with regard to physico-chemical features. Two experiments were carried out during the winter and the summer low water period. The relative abundance of each species was used to determine how community structure fluctuated in time and along the longitudinal stream gradient. Natural epilithon was investigated in the same way at the end of the experiments. Achnanthaceae, in winter, and Fragilariaceae, in summer, were the major colonizers after seven days and were then replaced by Naviculaceae and Bacillariaceae. The winter low water period was characterized by Diatoma vulgaris, Diatoma ehrenbergii, Fragilaria arcus, Gomphonema olivaceum and Navicula lanceolata; the summer low water period was marked by Achnanthes minutissima, Cocconeis placentula var. euglypta, Cyclotella meneghiniana, Cyclotella pseudostelligera, Navicula capitatoradiata, Navicula recens, Navicula subminuscula, Navicula saprophila, Nitzschia palea and Nitzschia paleacea. Along the longitudinal gradient, there was a progressive substitution of Achnanthaceae and Fragilariaceae by Naviculaceae and Bacillariaceae. The impact of pollution was more visible during the summer low water period. In summer, the epilithon communities architecture was probably partially due to grazing. The diatom flora (132 taxa) was typical of a limestone region river. The SHANNON Index and the analysis of the diatom communities on artificial substrates and on the natural rocks showed a great similarity.

Evolution, Water Balance, Potential Hazards, and Control of a Pro-Glacial Lake in the French ALPS

Lake Arsine, a pro-glacial lake in the French Alps, first appeared 30 years ago and has since been growing steadily. In 1985, it reached an area of 5.9 ha, a maximum depth of 39 m, and a volume of 0.8 × 106 m3. This lake is dammed partially by a glacial moraine and partially by a tongue of dead ice covered by a moraine 1–2 m thick. The glacier calves into the lake, which collects all the melt water from the surrounding glacial area of 250 ha. No open outlet exists and seepage reaches a value of 5 × 106 m3 year−1. A 1 year water balance shows that seepage increases rapidly with water level, from less than 0.03 m3 s−1to more than 0.75 m3 s−l for a rise in water level of 10 m. The seasonal lake-volume fluctuations of 0.5 × 106 m3 are small compared with the inflow volume of 5 × 106 m3.Progressive clogging of the bottom by glacial flour has led to a gradual rise of 8 m in 16 years in the summer level, while at the same time the height of the dam has decreased by 10 m due to the melting of dead ice. Consequently, by the end of July 1985 the freeboard was only 2 m and overflow on to the dead ice was thought likely to occur in the very near future. To eliminate this flood hazard, a 250 m long channel was dug in an ice-free zone which had been profiled by geophysical prospecting. This work was carried out between 14 April and 13 June 1986, in order to benefit from the low winter water level.Geotechnical studies of the moraine have shown that no large landslide is to be feared. A crude model of the waves created by calving shows that the new water level is safe and the channel is capable of handling the maximum likely discharge of 15 m3 s−1 resulting from the highest possible wave of 3.5 m.

Evolution, Water Balance, Potential Hazards, and Control of a Pro-Glacial Lake in the French ALPS

Lake Arsine, a pro-glacial lake in the French Alps, first appeared 30 years ago and has since been growing steadily. In 1985, it reached an area of 5.9 ha, a maximum depth of 39 m, and a volume of 0.8 × 106 m3. This lake is dammed partially by a glacial moraine and partially by a tongue of dead ice covered by a moraine 1–2 m thick. The glacier calves into the lake, which collects all the melt water from the surrounding glacial area of 250 ha. No open outlet exists and seepage reaches a value of 5 × 106 m3 year−1. A 1 year water balance shows that seepage increases rapidly with water level, from less than 0.03 m3 s−1to more than 0.75 m3 s−l for a rise in water level of 10 m. The seasonal lake-volume fluctuations of 0.5 × 106 m3 are small compared with the inflow volume of 5 × 106 m3. Progressive clogging of the bottom by glacial flour has led to a gradual rise of 8 m in 16 years in the summer level, while at the same time the height of the dam has decreased by 10 m due to the melting of dead ice. Consequently, by the end of July 1985 the freeboard was only 2 m and overflow on to the dead ice was thought likely to occur in the very near future. To eliminate this flood hazard, a 250 m long channel was dug in an ice-free zone which had been profiled by geophysical prospecting. This work was carried out between 14 April and 13 June 1986, in order to benefit from the low winter water level. Geotechnical studies of the moraine have shown that no large landslide is to be feared. A crude model of the waves created by calving shows that the new water level is safe and the channel is capable of handling the maximum likely discharge of 15 m3 s−1 resulting from the highest possible wave of 3.5 m.

Barging on the Columbia

BARGING ON THE COLUMBIA James G. Ashbaugh Portland State College Columbia River barging as discussed in the following paper is limited to that part of the river between Portland, Oregon—Vancouver, Washington, and Pasco, Washington. Transportation on the Columbia River has had a long and colorful history. Almost one hundred years ago, the Oregon Steam Navigation Company was formed and during its twenty-year life it completely monopolized navigation on the Columbia. The role played by this company's vessels, most of which were stern-wheelers, was extremely important in the pre-railroad era in the Pacific Northwest. The fact that it was able to operate at a profit as long as it did is attributable more to the lack of competing transportation, than to ease of navigation on the Columbia. Only in its estuary portion from Cascade Rapids to the sea was the Columbia easily navigable. Above this point it flows for a considerable distance across the Columbia Plateau before cutting a gorge through the Cascade Range. Although the river drops less than a foot a mile between Pasco and the sea, much of the total drop occurred at two places—The Dalles and Cascade Rapids. Portages were required around these places. Moreover, during the winter low water period, many stretches of the river were often too shallow for any but the smallest vessels. The availability of fuel also added to the expense of operation and above The Dalles timber is scarce. One of the early uses for barges in this part of the river was transporting wood to fueling stations. Some of the boats used as much as fifty cords of wood on the trip up river. It is therefore understandable why river transportation was badly hurt by railroad transportation after 1883. From this time until the inauguration of a river development program by the federal government in the 1930's, river transportation on the Columbia above its estuary was insignificant. The construction of Cascade Locks in 1896 and the Celilo Canal in 1915 to by-pass the Cascade Rapids and The Dalles, helped increase river traffic but did not materially weaken the near monopoly of railroad transportation. While barging on the Columbia above the Cascade Rapids was declining, that on the estuary part of the river was developing in response to local needs. Perhaps foremost among uses for barges within this area was the hauling of pulp and paper products and lumber. It must be remembered that this part of the river is navigable by ocean-going vessels as far upstream as Portland and Vancouver and barges are mainly utilized to bring freight to and from places not accessible to deep-draft ships. Among such places are the paper factories at West Linn on the Willamette River and Camas on the Columbia. With the development of dams on the Columbia and improved navigation made possible by the slack water created, the area served by barges has been greatly expanded. The first project completed was Bonneville Dam. This not only made available a larger lock than the old one around Cascade 13 Rapids but created slack water to The Dalles. It was opened for navigation in 1938. After World War II, as the first step in the implementation of a plan to make navigation possible to Lewiston, Idaho, on the Snake River, McNary Dam was constructed. Built three miles east of Umatilla, Oregon, it creates a slack water pool 61 miles in length to Pasco and Kennewick, Washington. The next one built was The Dalles Dam which not only inundates both Celilo Falls and the old Dalles-Celilo Canal, but also provides a slack water navigation pool 25 miles long to the site of the John Day Dam. Still under construction, John Day Dam will create a slack water pool 76 miles long to McNary Dam. This last unit, when completed in 1967, will eliminate the last stretch of river that is difficult to navigate. Four others on the Snake River will extend navigation to Lewiston, Idaho. With the exception of the one at Bonneville, navigation locks are or will be 86 feet wide by 675 feet in length. The locks at Bonneville are 76 by 500 feet...