Closed Water Bodies Research Articles

Migrations of hatchling European pond turtles (Emys orbicularis) after nest emergence

Distances between nest sites of Emys orbicularis and the nearest water bodies can be long. We studied whether a longer distance could affect the probability of hatchling survival, migration time, and body mass loss. In our research area (Lubuskie district, western Poland), nest sites were situated on a slope; the closest water body was in a distance of 72-290 m. Near the water body we constructed a 550 m long drift fence to recapture hatchlings migrating down the slope. We monitored 32 hatchlings from 7 different nests deposited in the years 2008-2010. The hatchlings started to emerge from their nests on 9 and 13 April 2009, 7 and 9 April 2010, 30 March, 7 and 8 April 2011. Then, hatchlings were radiotracked using transmitters glued on their carapaces. Individuals () recaptured near the fence travelled the distance between the nest site and the fence within 18-727 hours (0.75-∼30 days). Hatchlings from nests situated only a short distance away (72-81 m) were recaptured in higher numbers, compared to those from nests situated further away (227-290 m). During the journey the hatchlings lost on average ∼3.8% of their initial body mass. The hatchlings which migrated longer lose more of their initial body mass than those which migrated shorter.

水面被覆を伴う小規模閉鎖水域に作用する風による溶存酸素供給効果に関する研究

水面被覆を伴う小規模閉鎖水域に作用する風による溶存酸素供給効果に関する研究

МОЛЮСКИ В РАДІОЕКОЛОГІЧНИХ ДОСЛІДЖЕННЯХ ПРІСНОВОДНИХ ЕКОСИСТЕМ

Проаналізовано видоспецифічність і динаміку концентрування 90Sr, 137Cs та деякихтрансуранових елементів у двостулкових і черевоногих прісноводих молюсківЧорнобильської зони відчуження та зони безумовного (обов’язкового) відселення в період1998–2010 рр. Наведено результати оцінки дозових навантажень, частоти хромосомнихаберацій та аналізу складу гемолімфи молюсків. Потужність поглиненої дози опроміненняреєстровано в діапазоні 0,3–85,0 мкГр/год. У замкнутих водоймах відмічено підвищенучастоту хромосомних аберацій у тканинах ембріонів (до 27 %) та зміну гематологічнихпоказників у дорослих особин молюсків.Ключові слова: гематологічні показники, дозові навантаження, прісноводні молюски,радіонуклідне забруднення, хромосомні аберації, Чорнобильська зона відчуження.

諫早湾干拓調整池における降雨時の流れの予測に関する研究

Flood inflow is one of the factors which give influences to flow and material transport in closed water body. In this study, flows induced by flood in Isahaya flood regulation pond were predicted using a numerical simulation model composed by rainfall-runoff model and hydrodynamic model. In advance of the simulation, applicability of these models to Isahaya regions were examined. Simulated results shows that flows were formed in this pond by inflow of flood and gates operation to control the accumulated water level. On the other hand, at the water area apart from river mouths, effects of wind on flow are not negligible. This means that, in order to clear the material transport processes in this pond, influences of inflow of flood as well as wind should be considered in the wet weather condition.

Assessment of long-term changes in nitrogen pollution load potential from sewage treatment water in the Tedori River Alluvial Fan Area, Japan

Long-term changes (1974–2007) in the nitrogen pollution load potential (NPLP) arising from sewage treatment water were assessed in the Tedori River Alluvial Fan Area of Japan. The total NPLP from sewage treatment systems (STS) during the 34 year period was 439 t (103 kg) year−1 from about 260,000 users in 1974 increasing to a peak of 793 t year−1 in 1992 from about 363,000 users, and then decreasing to 676 t year−1 from about 400,000 users in 2007. The NPLP outflow into the area increased from 356 t year−1 in 1974 to a peak of 596 t year−1 in 1985 followed by a rapid decrease to 98 t year−1 in 2007. The NPLP outflow from the public STS to the Japan Sea began in 1979 and rapidly increased to 575 t year−1 in 2007 from about 362,000 users. This represents 85.5% of the total NPLP. The NPLP from septic tanks in the area was 356 t year−1 from about 107,000 users in 1974 gradually increasing to a peak of 587 t year−1 from about 177,000 users in 1985 before rapidly decreasing to 60 t year−1 from about 15,000 users in 2007. Although the current NPLP is about 98 t year−1 in the study area, the average NPLP during 34 years was very different at 424 t year−1. NPLP assessments affecting groundwater and closed water bodies should consider long-term processes of nitrogen pollution from STS over time periods compatible with the residence time of the receiving waters.

Effects of Water Environment in Closed Water Body on Diffusion of High-Dissolved-Oxygen Water into Bottom Layer and Its Improvement of Water Quality

Effects of Water Environment in Closed Water Body on Diffusion of High-Dissolved-Oxygen Water into Bottom Layer and Its Improvement of Water Quality

Response Characteristics of Internal Wave to Wind Stress in a Shallow Closed Water Body

Response Characteristics of Internal Wave to Wind Stress in a Shallow Closed Water Body

Phylogeography, genetic structure, and conservation of the endangered Caspian brown trout, Salmo trutta caspius (Kessler, 1877), from Iran

The Caspian Sea, the largest inland closed water body in the world, has numerous endemic species. The Caspian brown trout (Salmo trutta caspius) is considered as endangered according to IUCN criteria. Information on phylogeography and genetic structure is crucial for appropriate management of genetic resources. In spite of the huge number of studies carried out in the Salmo trutta species complex across its distribution range, very few data are available on these issues for S. trutta within the Caspian Sea. Mitochondrial (mtDNA control region) and nuclear (major ribosomal DNA internal transcribed spacer 1, ITS-1, and ten microsatellite loci) molecular markers were used to study the phylogeography, genetic structure, and current captive breeding strategies for reinforcement of Caspian trout in North Iranian rivers. Our results confirmed the presence of Salmo trutta caspius in this region. Phylogenetic analysis demonstrated its membership to the brown trout Danubian (DA) lineage. Genetic diversity of Caspian brown trout in Iranian Rivers is comparable to the levels usually observed in sustainable anadromous European brown trout populations. Microsatellite data suggested two main clusters connected by gene flow among river basins likely by anadromous fish. No genetic differences were detected between the hatchery sample and the remaining wild populations. While the current hatchery program has not produced detectable genetic changes in the wild populations, conservation strategies prioritizing habitat improvement and recovering natural spawning areas for enhancing wild populations are emphasized.

Wind-Induced Phenomenon in a Closed Water Area with Floating-Leaved Plant

In this study, in order to clarify wind-induced phenomena, especially vertical mixing of density stratification in a closed water area with floating-leaved plants, we conducted hydraulic experiments on wind flow characteristics, wind wave characteristics, entrainment phenomena and turbulent structure by using a wind tunnel test tank and simulated floating-leaved plants. From the experimental results of wind flow and wind wave characteristics, we quantified the impact of the occupancy rate of the plants on their resistance characteristics. From the experimental results of entrainment phenomena, we defined the parameter that could explain the magnitude of mixing between the density stratifications, and quantified the impact of the occupancy rate on vertical mixing between stratifications. From the experimental results of the turbulent structure of the upper layer, we clarified the differences in small-scale turbulence components at each occupancy rate and quantified the impact of the occupancy rate on the turbulence characteristics. For a summary of this study, we theoretically quantified wind-induced entrainment phenomena in a closed water area with luxuriant growth of floating-leaved plants. The results indicated that the impact of luxuriant growth of floating-leaved plants in a closed water body could be seen in the difference in small-scale fluid characteristics, and these characteristics could be expressed using the small-scale turbulent components. Keywords—Density Stratification, Floating-leaved Plant, Wind-induced Entrainment Phenomenon, Turbulent Structure

수온성층흐름에서 바람에 의해 발생하는 순환흐름을 해석하기 위한 수치모형개발

저수지와 같은 갇혀진 수체는 상류에서 유입되는 오염물질 뿐만 아니라 성층현상에 의해서도 오염될 수 있다. 갇혀진 수체에서의 연직순환은 이러한 오염을 줄이는데 중요한 역할을 하는데, 연직순환을 일으키는 인자로는 빛의 입사, 바람, 물의 온도 및 열의 확산 등이 있으며, 그중에서도 가장 중요한 것은 바람의 영향이다. 그러므로 성층화된 흐름에서 바람에 의해 발생하는 연직순환에 대한 수치모형을 개발하고 적용하는 것이 필요하다. 본 연구는 수온성층흐름을 해석할 수 있는 3차원 수치모형을 제시하였다. 유속성분은x-축과 y-축 방향에서의 운동량방정식으로부터 3단계에 걸쳐 계산되고, 자유수면 변위와 온도변화 등의 스칼라양은 각각 자유수면방정식과 이송-확산 방정식으로부터 계산된다. 본 연구에서 제시한 모형의 정확도를 검증하기 위하여 정사각형수조에서 진동하는 자유수면의 해석해와 비교하였고, 성층화된 흐름에서 발생하는 연직순환에 대하여 수치모의를 실시하였다. 그 결과, 본 연구에서 개발된 수치모형이 흐름 내부의 현상을 잘 묘사함을 알 수 있었다. The closed water bodies, such as reservoirs and lakes, could be contaminated by an inflow of pollutants in the upstream as well as a stratification caused by seasonal natural phenomena. The vertical circulation particularly plays an important role in reduction of environmental pollutants. The factors of the vertical circulation are the temperature, wind, thermal diffusivity and sunlight. The wind is probably the most significant factor among them. Thus, it is necessary to describe the validation and application of a three-dimensional numerical model of wind-induced circulation in a thermally stratified flow. In this paper, a three-dimensional numerical model for the thermally stratified flows is presented. The model is conducted in three steps to calculate the velocity components from the momentum equations in x- and y- axis directions, the elevations from the free surface equation and the temperature from the scalar transport equation. Numerical predictions are compared with available analytical solutions for the sloshing free surface movement in a rectangular basin. The numerical results generally show a reasonable agreement with analytical solutions. And the model is applied to the circulation for the wind induced flow in a thermally stratification. Consequently, the developed model is validated by two verifications and phenomena of the internal flow.

Thermal Convection in a Closed Water Body with Compound Cross Section

In a closed water body with compound cross section, we examined the effects of horizontal convection based on the horizontal density difference on the characteristics of thermal convection generated by radiational cooling at water surface. An experiment for measuring water temperature revealed that the fluid exchange was done by the horizontal convection based on the density difference between deep and shallow parts. Moreover, a flow visualization experiment to investigate the characteristics of thermal, which are developmental factors in vertical convection, found that the generation frequency and the generation interval of thermals was higher in the case of compound cross section than the case of even depth. That is, it was understood that the change of the development characteristics of the mixed layer (vertical convection) based on the effect of horizontal convection occurred by the change of occurrence characteristics of the thermals.

Effect of Horizontal Convection on the Natural Cooling Process at Water Surface in a Closed Water Body

Effect of Horizontal Convection on the Natural Cooling Process at Water Surface in a Closed Water Body

Coupling of two- and three-dimensional hydrodynamic numerical models for simulating wind-induced currents in deep basins

The main interest of the present study is the simulation of wind-induced currents in closed water bodies with shallow and deep regions. This paper describes a low time consumption numerical modelling technique for the simulation of free-surface flow over a geometrically complex bed. To achieve this, a technique employing coupled two- and three-dimensional flow solvers is developed for simulation of the flow. The conjunctive model consists of an upper part 2D Shallow Water Flow Solver (2D-SWFS) coupled with a 3D pseudo-compressible flow solver (3D-PCFS) for the deep regions with a proper interface boundary condition. The 2D-SWFS and 3D-PCFS solvers are coupled via an interfacial shear stress gradient and pressure effects. Time stepping is performed for the 2D solver, and an iterative procedure is employed by the 3D solver to satisfy the equilibrium constraints for the interfacial boundary. The model is able to consider 2D wetting and drying shallow regions without any underlying deep water. Both the 2D and 3D models use nodal based Galerkin finite volume method (GFVM) for solving the governing equations on the unstructured meshes. The accuracy of both models in solving the effective phenomena is examined by comparing the results of simulated test cases with readily available analytical solutions and experimental measurements. Finally, the accuracy of the conjunctive model is assessed by comparing its results for test cases with analytical solutions and experimental measurements from the literature. The new simulation method is then used to solve a wind-induced flow problem in a basin with deep water surrounded by shallow water parts.

Density Current Caused by Natural Cooling in a Closed Water Body with Shallow Area

Density Current Caused by Natural Cooling in a Closed Water Body with Shallow Area

Effect of Floating Vegetation on Wind Flow and Wave in Closed Water Body

Effect of Floating Vegetation on Wind Flow and Wave in Closed Water Body

Impact of luxuriant aquatic plants on thermal convection in a closed water body

The attenuation of heat flux at the water surface with aquatic plants was examined by hydraulic experiments to consider the influence of aquatic plants on the magnitude of thermal disturbance in the closed water body. First of all, the experiment measuring temperatures on surface of leaf revealed the thermal conductivity of the leaf which is peculiar physicality of each aquatic plant. Then, the hydraulic experiment examined attenuation of the underwater illuminance and the heat flux in the covered part which depending on the kind and the luxuriant density of the aquatic plants. As the result, it is clarified that the attenuation rate of the illuminance is large in the plant with a thick leaf, and that the heat flux at the water surface and the developmental velocity of the mixed layer decreased when the luxuriant density of the aquatic plants increased.

Mixing by wind-induced flow and thermal convection in a small, shallow and stratified lake

Thermal stratification is one of the important features in closed water bodies, which primarily depend on meteorological conditions, and has strong impact on the ecological environment in lakes or reservoirs. Data monitored in 3 days were analyzed for factors that affect heat mixing processes to examine the diurnal stratification cycles in the Shikinawa Lake, a study area in Fukuoka prefecture, Japan. We found that wind speeds and directions played an important role in the thermal mixing in the lake. High solar heating mainly caused stratification state, but with less effect under stronger wind action. Development of mixed layer depth in a natural lake due to wind-induced flow and thermal convection were calculated. Functional relationships between entrainment rate and Richardson number or Wedderburn number were found and represented in this paper. Besides, heats exchanged at the air–water interface and energy stored in the water column were also analyzed and discussed.

Formation and Disappearance of Thermal Stratification in a Small Shallow Lake

In closed water bodies which the inflow and outflow are usually small, vertical transportation based on the formation of water temperature stratification, the problem of water quality pollution due to the inhibition of mixing easily occur, especially the problems become serious in shallow water bodies. The main reasons that drive the formation and disappearance of water temperature stratification are mechanical disturbance caused by the acting of wind, or solar radiation in daytime, thermal disturbance due to radiational cooling at night. Clarifying the processes of formation and disappearance of stratification response to these two kinds of distur- bance is very important for management and improvement of the environment in the water bodies. So, in this research, a shallow closed water body with the overgrowth of aquatic plants was targeted for field observation and quantitative discussion on the processes of formation and disappearance of the thermal stratification.

Water environment conservation in a closed water body by high concentrated oxygen water

In this study, the method of using high concentrated oxygen water to purify the bottom sediment was confirmed to be effective. The high concentrated oxygen dissolver was developed and the lab scale experiment was performed. High rate, high efficiency oxygen dissolver was developed, the optimum running condition of the apparatus and the method of producing high concentrated oxygen water was discussed and determined in this study. In addition, the effective prevention of phosphorus release from anaerobic bottom sediment was also studied. As a result, it is found that high concentrated oxygen water was effective for prevention of phosphorus release from anaerobic bottom sediment. On the basis of the fundamental knowledge from the laboratory-scale study, pilot scale apparatus was set up and the pilot study was carried out. It is showed that the introduction of high concentrated oxygen water did not destroy the thermocline of dam reservoir.

137Cs in deep-water lakes: Analysis of the peculiarities of water contamination and purification

The assessment of 137Cs concentration in water based on the model of radionuclide absorption by the bottom sediment of a closed water body is applicable to deep-water lakes with slower water circulation (the time of water exchange exceeding 10 years). The low river runoff from such lakes does not determine their water purification from 137Cs because of the predominance of the process of 137Cs sorption by suspension and bottom sediment. The contamination of a deep-water arctic lake with global 137Cs is reconstructed.