Decrease In Water Level Research Articles

Determination of the time of lowering depression surface in transition zones with a smooth and instantaneous decrease in water level in reservoir

The Republic of Uzbekistan pays great attention to the development and implementation of a program for the development of hydropower based on ensuring the share of hydropower in the energy potential and the integrated development of hydropower potential. Over the last three years, hydropower plants have been built or reconstructed in more than a dozen small and medium-sized earth dams to accomplish this task. Typically, unstable filtration is observed in the body of earth dams because of deviations from the normal filling and emptying of water reservoirs. The main goal of the research is to determine the time to lower the depression surface in the Tupalang earth dam transition zones, which characterizes the intensity of unstable filtration during a smooth and sudden drop in reservoir water level. The calculations were made according to the theoretical dependences of V.P.Nedriga for two cases of smooth and sudden lowering of the water level in the reservoir, starting from the normal backed level (NBL). In the calculations, the values of the main parameters were taken to be the coefficient of water loss of the soil (0.3), the coefficient of filtration of the transition zones (9.5 m/day), and the coefficient of laying the slope of the transition zones (0.2). Calculations showed that the time of lowering the depression surface in the transition zones with a gradual decrease in the water level in the reservoir was 84.1 days, and with an instantaneous decrease in the water level during the operation of a dam with a height of 120 m 3.86 days, and during the operation of a dam with a height of 185 m 6.82 days.

Changes in Radiation Exposure Rate of Fish of the Cooling Pond of the Chornobyl NPS and Lake Azbuchyn after Water Level Lowering

Changes in the absorbed dose rate of external and internal exposure of the representatives of fish fauna of the cooling pond of the Chornobyl NPS and Lake Azbuchyn after the interruption of water supply into the cooling pond at the end of 2014 were investigated in 2014-2021. Changes in hydrological regime resulted in the decrease in water level in the cooling pond by 6.5-7.0 m, whereas in Lake Azbuchyn - by 2.5-3.0 m. In this case, <sup>90</sup>Sr concentration activity in the water and biota increased. It has been found that in 2021 dose load from the incorporated <sup>90</sup>Sr on fish of the cooling pond increased on the average by a factor of 4.5, whereas in Lake Azbuchyn - by a factor of 7.5 as compared to previous period (prior to a decrease in water level). The external dose rate for fish of the cooling pond remained almost unchanged, whereas in Lake Azbuchyn it increased as a result of replacing littoral and sub-littoral zones of the lake with the sections of the bottom characterized by an essentially higher level of radio-nuclide contamination.

УРОВЕННЫЙ РЕЖИМ ТРЕХ КРУПНЕЙШИХ ОЗЕР ЕВРОПЫ: ПРОШЛОЕ И НАСТОЯЩЕЕ

The largest lakes in Europe, as well as all water objects in the region, are under the influence of climate change. The most pronounced changes in the water regime of lakes are noted in the intra-annual distribution of the water level. The increase in the average annual air temperature (by 1.3℃ on average) and annual precipitation layers (from 35 to 77 mm/year on average) in the second climatic period practically did not affect the average annual water levels of lakes Ladoga and Peipus, whereas the average annual water level of Lake Onega in the second climatic period (1991 – 2020) increased by 10% compared to the first period (1961 – 1990). At the same time, the inflow to Lake Onega has not changed and is about 16.7 km3/year. For more than 140 years, there have been pronounced trends toward a decrease in the average annual water level of Peipus and Ladoga and toward an increase in the average annual water level of Onega. For the significance level =0.1, the trends of changes in the levels of the studied lakes are significant. The increase in the level of Onega is explained by the fact that this lake is under the influence of the Verkhne-Svirskaya HPP and is characterized by a retaining regime. The influence of the retaining regime also determined the heterogeneity of the average annual water levels of Lake Onega. In addition, the relative proximity of this reservoir to the White Sea results in a more pronounced influence of the Arctic air mass transfer on the conditions for the formation of runoff in the Onega catchment.

Scouring effect of the middle and lower reaches of the Yangtze River and its impact after the impoundment of the Three Gorges Project

三峡及其上游干支流梯级水库建成运用后,大坝下游“清水下泄”引起了长江中下游河道发生长时间、长距离的冲刷。2001-2021年期间宜昌至长江口已累计冲刷了50.3亿m³,需厘清河道冲刷对河势、防洪、航运等方面产生影响。分析表明:三峡工程运用后,长江中下游河势总体稳定,弯道段出现切滩撇弯、汊道段出现塞支强干等现象;河道槽蓄量的持续增加,进一步增大了河道调蓄和行洪能力,但水流顶冲点的变化和近岸河床的冲刷下切,使得河道崩岸频发,并影响河势稳定和防洪安全;在河道冲刷、河势控制与航道工程综合作用下,长江中下游航道条件总体得到改善,但河道不均衡冲刷使得坝下游砂卵石河段出现“坡陡流急”,沙质河段出现洲滩散乱、航槽移位等现象,影响航道条件;同流量下枯水位呈下降态势,逢极枯年份影响长江中下游用水安全;江湖关系发生新变化,“三口”分流道由原淤积转为冲刷,两湖湖区水位不同程度的降低,枯水位出现时间有所提前,不利于湖区水资源和生态环境的安全与可持续发展;三峡工程实施枯水期补水调度和“压咸潮”调度以及长江口北支淤积减缓,对于遏制长江口咸潮入侵有利,入海泥沙显著减少引起长江口近岸河床冲刷,影响沿岸码头的安全运行。;After the construction of cascade reservoirs in the Three Gorges and its upper reaches, the downstream clear water of the dam was discharged, and a long-term and long-distance erosion occurred in the middle and lower reaches of the Yangtze River. From Yichang to the Yangtze Estuary, a total of 5030 million m³ was scoured. Under the background of large-scale erosion in the middle and lower reaches of the Yangtze River, it has a profound impact on river regime, flood control and shipping. The analysis shows that the river regime in the middle and lower reaches of the Yangtze River is generally stable, and the river regime in some parts of the river changes greatly, resulting in the phenomenon of beach cutting and bending, and the phenomenon of strong trunk. The increase of channel storage capacity increases the capacity of river discharge and flood storage, but the change of flow top scour point and the erosion of nearshore riverbed also make the river bank collapse frequently, affecting the stability of river regime and flood control safety. Under the combined action of channel scour, river regime control and channel engineering, channel conditions in the middle and lower reaches of the Yangtze River improved overall. However, due to the unbalanced scouring of the river channel, the sandy pebble river section in the downstream of the dam has a 'steep slope and rapid flow’, and the sandy river section has phenomena such as scattered beaches and channel displacement, affecting the channel conditions; the continuous erosion of river bed results in the decrease of low water level, which affects the water supply safety of life, production and ecology along the middle and lower reaches of the Yangtze River in extremely dry years. The relationship between rivers and lakes has undergone new changes. The three diversion channels have changed from original siltation to erosion. The water levels in the two lakes have decreased to varying degrees, and the low water level has appeared earlier, which has adversely affected the water resources and ecological environment in the lake area. The regulation of water replenishment and saltwater intrusion in dry season of the Three Gorges Project and the slowing down of siltation in the north branch are beneficial to the control of saltwater intrusion in the Yangtze Estuary. The sediment discharged into the sea from the Yangtze Estuary is significantly reduced and the riverbed near the Yangtze Estuary is scoured strongly. It seriously threatens the safety of the main structure of coastal enterprise wharf.

СОВРЕМЕННОЕ РЕЛЬЕФООБРАЗОВАНИЕ В ЛАНДШАФТЕ ДЕЛЬТЫ ВОЛГИ (НА ПРИМЕРЕ ГРУППЫ БУГРОВЫХ УРОЧИЩ)2

Modern relief-forming processes, especially exogenous, are always associated with the landscape features of theregion where they are observed. Anthropogenic impact on geosystems of different ranks often contributes to these processes. Emerging landforms often result from the interaction of a number of factors. The article presents the results of studies of negative landforms, mainly in the form of dips, fissures, and trenches, which in recent years began to form in the vicinity of the Baer knolls and their surrounding geosystems, located within the central subregion of the Volga Delta landscape. The paper provides their morphological and morphometric parameters. Both natural prerequisites and anthropogenic factors of the occurrence of these landforms are considered. Natural peculiarities of the studied Volga Delta landscape subregion include the presence of ridges on the horizontal and subhorizontal surface, called Baer knolls in the scientific literature, which contributes to the occurrence of temporary surface runoff. Another factor of natural genesis is the presence in the studied group of tracts of the so-called ‘chocolate’ clays of Khvalynsky age, usually deposited on a complex of granulometrically heterogeneous rocks. To some extent, climatic fluctuations recorded in the study area contributed to the emergence of the landforms. Anthropogenic preconditions include significant changes in natural relief during the economic use of the Volga Delta landscape. As a working hypothesis, another reason for the emergence of the studied landforms is seen in a decrease in the ground water level due to the reduced volume and duration of spring floods in the lower Volga. Based on the obtained results and taking into account the absence of karst substrate in the Volga Delta and a short period of formation, the genetic type of the formed relief is defined as anthropogenic pseudokarst

A reduced-complexity shoreline model for coastal areas with large water level fluctuations

A new reduced-complexity, 1-D shoreline model has been developed, calibrated, and tested with a set of shoreline positions detected from high-resolution satellite images. Motivated by recent large interannual water level fluctuations and associated shoreline changes in the Great Lakes, the model is built on previous models that are based on the disequilibrium concept, with extensions for water level effects. Unlike other shoreline models, the model includes two different sources of disequilibrium, wave disequilibrium and water level disequilibrium. The model also includes a passive flooding term to account for the instantaneous effect of the water level changes on the shoreline position. Case studies forced by seasonally-varying waves and water levels varying on seasonal and interannual timescales highlight the model's ability to enhance wave-driven shoreline change when water level variations are additionally present. The model was applied to two sites along the Lake Michigan shoreline, Jeorse Park and West Beaches, with shoreline time series extracted from multispectral satellite imagery. When calibrated and applied to an eleven year period of decreasing water levels, the new model shows significant skill in simulating and forecasting the shoreline position in the two study areas, with modest improvement over existing models. The simulation results additionally highlight the dominance of water level disequilibrium over wave disequilibrium for the study sites. When applied to a nearly forty year simulation of West Beach, the new model shows excellent ability to model the shoreline response to water level and wave fluctuations over a range of timescales. Comparison models are seen to be incapable of capturing the water level effects, particularly when water level trends differ from the calibration period. Overall, the model results and parameters show the importance of the newly introduced water level disequilibrium in modulating wave-driven shoreline change. Finally, while the shoreline model was motivated by Great Lakes coastal processes, it may provide new predication abilities for coastlines where water level fluctuations and trends play a role in shoreline changes. • A new shoreline model is developed, tested, and compared to existing models. • The model is based on the concept of combined wave and water level disequilibrium. • The model is applied to two case studies along the Lake Michigan shoreline. • The model successfully simulates shoreline changes enhanced by water level changes.

Analisis Potensi Debit Air Tanah Melalui Pumping Test Metode Step Draw Down pada Sumur Bor Irigasi di Desa Bonto Rannu, Kecamatan Kajang, Kabupaten Bulukumba, Sulawesi Selatan

The rice fields in Bonto Rannu Village, Kajang District, Bulukumba Regency are dominated by rainfed rice fields. This species has limitations in the dry season because irrigation/agricultural irrigation completely depends on rainwater. Therefore, it is necessary to identify alternative irrigation sources to sustain farmers' farming activities in Bonto Rannu Village. This study aims to analyze the number of groundwater wells by testing in the form of a pump test (pumping test) with the step draw-down method. The optimum discharge (Qopt) of well 1 is 0.01876 m3/s or 67.53 m3/hour with an optimum Sw of 2.891 m. This shows that groundwater in well one can be pumped at 67.53 m3/hour with a decreased water level of 2.891 m, with the pump condition still technically safe. As for well 2, the optimum discharge (Qopt) is 0.00318 m3/s or 11.45 m3/hour with an optimum Sw of 2.100 m. These data indicate that there are limited groundwater reserves.

Suchozemští plži přírodní rezervace Plané loučky a přírodních památek Častava, Hvězda a Kurfürstovo rameno v CHKO Litovelské Pomoraví [Terrestrial gastropods of Plané loučky Nature Reserve and Častava, Hvězda, and Kurfürstovo rameno Nature Monuments in Litovelské Pomoraví PLA

In 2022, four small-scale protected areas (SPA) within Litovelské Pomoraví Protected Landscape Area were surveyed for terrestrial molluscs. All localities are floodplain forest fragments with oxbow lakes, pools and marshes in the Morava river catchment. The most species-rich SPA was Hvězda Natural Monument (NM), with 38 species recorded. The threatened species Cochlicopa nitens (Endangered), known from this area from previous surveys, was not recorded despite high sampling effort. This sensitive hygrophilous species disappeared probably due to droughts occurring in earlier years. However, other sensitive hygrophilous species such as Euconulus alderi (Nearly Threatened) and Vertigo antivertigo were recorded. The latter was also found in Plané loučky Nature Reserve (NR; 27 spp. in total) and Častava NM (19 spp. in total). Relatively common floodplain forest species Perforatella bidentata was recorded in Plané loučky NR and Hvězda NM; however, it was absent in Častava NM and Kurfürstovo rameno NM (20 spp. in total). The partial absence of this species and the complete absence of substantially declining floodplain species Pseudotrichia rubiginosa (Nearly Threatened) and other sensitive taxa indicate habitat degradation caused mainly by stream regulations and water level decrease and manipulation. The presence of invasive plant species known to decrease terrestrial mollusc species diversity and abundance are of the essence as well. Highly invasive species Arion vulgaris was the most abundant species in all of the surveyed SPAs, except for Hvězda NM, where it was present in lower numbers. Over some twenty years, this species spread from anthropogenic areas to natural habitats to become one of the most prominent features of floodplain biocoenoses in Litovelské Pomoraví and elsewhere. To improve the habitat conservation status, it is important to maintain favourable water level in streams and water bodies adjacent to SPAs, especially during the critical periods of summer droughts. Furthermore, it is advised to focus the management on neophyte extirpation.

Features of movements of climbing perch Anabas testudineus in water flow and on land

Climbing perch Anabas testudineus in contradistinction to most fish is able to move not only in water but also on land. In the experiments, we study the diurnal locomotor activity of fish, the features of their movements in flow of clean water and polluted water by urea and thiourea, and the effect of decreasing water level on the crawling and moving on land. The behavior of fish in clean water aimed to move downstream at the beginning of the test and moving upstream in the end of the test. Fish exposition (12 days) under 0.05% urea and thiourea change their behavior in the water flow, which is expressed in the chaotic movement of fish relative to the current. Decreasing water level to the critical value (<3 cm) initiates climbing perch to crawling and moving on land. Two types of fish responses to decreasing water level were found: waiting, or crawling to land and moving. Based on the study diurnal locomotor activity, we found that the probability of climbing perch movements is higher in the daytime than in the dark.

Knowledge, Perception, and Intention of Professionals Related to The Transformation from Gray to Green Infrastructure in Egyptian Cities.

Green infrastructure (GI) has become one of the most important urban trends that helps to preserve and develop the city’s ecosystem. With global climate change and increased carbon emissions, the need to transition from gray infrastructure to green infrastructure has increased. Or the integration of green infrastructure and existing gray infrastructure in existing cities. In Egypt, which faces significant environmental and urban challenges from an increasing population, rising temperatures, decreasing water levels, and high pollution in cities, the value of green transformation could minimize these impacts and increase the quality of life. This research aims to study the knowledge of Egyptian researchers and specialists in the fields of architecture and engineering about GI techniques. Understand their perception and ability to deal with GI. In addition to studying the challenges and opportunities facing Egypt’s green transformation from a specialized perspective. The results confirmed the lack of awareness of green infrastructure among the selected sample. The research confirmed the existence of social and economic obstacles facing the green transition. The research sets recommendations for increasing knowledge and expertise in the Egyptian market’s green transformation field.

Analytical study of falling-head test in confined aquifer with consideration of non-instantaneous injection

A falling-head test is a common method to estimate aquifer properties in which the water level in a well is increased suddenly, which is a key assumption for the data to be analyzed by traditional methods such as Cooper et al. and Hvorslev methods. However, there are situations where the water level increases in the well occurs for a relatively long period before it falls. In this case theoretically, there is no existing method to analyze the data. Hydrogeologists or geotechnical engineers still use the traditional methods to analyze the data even the water level increase is not instantaneous. This study derives a semi-analytical solution to describe water level change in this case. The mathematical model consists of the injection stage and water level fall stage. It is found that the water level mound induced by non-instantaneous injection leads to slower decrease of water level in the well comparing to the instantaneous injection. This study further analyses the errors of the estimated hydraulic properties if the data are analyzed by traditional methods. If calculated by Cooper et al. method, the storativity is underestimated but there is no impact on estimated hydraulic conductivity. The hydraulic conductivity calculated by Hvorslev method is underestimated and the error of underestimation increases with injection time and aquifer parameters. The actual hydraulic conductivity can be a few times of the estimated value for typical aquifer parameters in Hong Kong. Furthermore, a field experiment is conducted to compare the instantaneous method, non-instantaneous method and field data. The present solution fits the data well, and the errors of estimated parameters by instantaneous injection method are consistent with the conclusions in the error analysis.

Dry-Season Water Level Shift Induced by Channel Change of the River–Lake System in China’s Largest Freshwater Lake, Poyang Lake

As a large open lake that connects to the middle reaches of Yangtze River, Poyang Lake, China, has experienced dramatic water level changes, especially during the dry periods (November–March) in recent years. For better understanding the shift of dry-season lake level, we quantified the variations induced by channel changes of the river–lake system (CCORLS). Attempts were achieved through establishing two Long Short-Term Memory (LSTM) based water level prediction models, combined hydrological data in the periods of 1956–2000 and 2006–2016. The results indicated that: (1) With reference to earlier (1956–2000) dry periods, the recent (2006–2016) mean water levels had an overall decreasing trend, with values of 0.04–1.26 m across the lake. (2) The response of water level to CCORLS was spatially heterogeneous, triggering a sharp reduction in the central to northern lake, an obvious reduction in the lake outlet, and a relatively smaller reduction in the southern lake. (3) The bottom topography alteration of Poyang Lake made a dominating contribution to decline the lake water levels, while the Yangtze River’s mainstream channel near the lake played a minor role in the decrease of water level. Results shed light on the impact of systematic watercourse changes on the water level of a lake connected a river and enhanced understanding of the characteristics and mechanisms behind the hydrological changes of large freshwater lakes.

The Effect of Mining Activities on the Paleokarstic Features, Recent Karstic Features, and Karst Water of the Bakony Region (Hungary)

This study describes the direct and indirect effects of mining on the karst of the Bakony Region. For this, the results of geological and mining research of the last century, the results of hydrological research of fifty years, as well as the investigations of several decades on the karst of the mountain region are used. Direct effects include the exploitation of filling materials (limonite, kaolinite, manganese ore, and bauxite) from paleokarst features, dolomite rubble, activities exploring or destroying cavities, and the pollution of cavity systems with mining waste (dirt). An indirect effect is karst water extraction. Mining activities (coal and quarrying) resulting in the development of pseudokarstic features are also mentioned here. It can be stated that the effects on the karst and karst features may be permanent and even renewing, but the original state may also have returned or can be expected in the near future. Damages may be local or regional. A regional effect is the decrease in karst water level, which has the most significant effect on the environment, but it has already reached its original state by now.

Geographic Information System (GIS) as a basis for the next generation of hydrogeological models to manage the geothermal area Waiwera (New Zealand)

Abstract. The geothermal hot water reservoir below the small town of Waiwera in New Zealand has been known to the indigenous Māori for many centuries. Overproduction by European immigrants led to a water level decrease and consequently artesian flow from the wells and the seeps on the beach ceased. The Te Kaunihera o Tāmaki Makaurau Auckland Council established the Waiwera Thermal Groundwater Allocation and Management Plan to allow the geothermal system to recover. For a sustainable operation, the management regime can be informed by hydrogeological models based on monitoring data. The underlying geological model has been revised according to field observations and an existing numerical model transferred to the newly developed software package TRANSPORTSE. Monitoring and digitally derived data have been integrated in a geographic information system (GIS).

Assessment of the impacts of climate change on livestock water sources and livestock production: Case study, Karamoja region of Uganda

AbstractThe study examined the impact of climate change on livestock water sources and livestock production using the Karamoja region of Uganda as a case study. The study's objectives were to determine the general public's perception of climate change, identify the major climatic factors affecting livestock productivity in Karamoja, and assess the extent to which climate change has affected water sources for animals and productivity of livestock in the study region. A cross‐sectional survey design, as well as a quantitative and qualitative data analysis, was used in the study. The total population of the study unit was 258, and the sample size was 222, which was chosen specifically through a purposive and random sampling technique. From the results and discussion of the study sample, while the general public was aware of and understands climate change, the study concluded that the likely causes of climate change were numerous, including deforestation, charcoal burning, natural events such as lake currents, carbon emissions, and land degradation. In Karamoja, climate change is causing erratic and uneven rainfall, drying of surface water bodies such as dams and rivers, high temperatures, deforestation, and outbreaks of livestock diseases. The major climatic factors identified that affect livestock water sources and productivity are higher temperatures, which have led to decreases in water levels and drying of seasonal surface water sources that livestock depend on, as well as flooding of some regions during heavy rains. The results from the regression model also showed that climate change has affected livestock water sources and productivity, with an 84.7% impact. The following adaptation measures have been proposed: diversification of livestock and crop varieties, agroforestry, awareness and sensitization campaigns, increased government and partner investment in water harvesting and agroforestry schemes, and improved capacity of all organizations and institutes involved.

Impacts of Climate Change on Water Resources, Agricultural Production and Food Security: Evidence from Turkiye

Since agricultural production depends mainly on nature and uses surface and groundwater reservoirs, changes in existing water resources significantly affect this sector. Again, changes in global climate bring changes in water levels, consequently affecting agriculture, food supply, and income sources of households in different areas. However, to date, no such research has investigated the farmers who are the producers and the most vulnerable group to the impacts of climate change. Therefore, this paper explores climate change impacts on the water resources of Sarayonu, which in turn affects the agricultural food production and food security of the producers' households and the country's market. This qualitative study conducted in-depth interviews with the farmers from the Sarayonu district of Konya province in Turkiye. The study results show that ground and surface water resources are negatively affected by climate change. Consequently, the study area observed a decrease in water level over the last 15 years. Thus, these changes in water resources have been significantly affecting the agriculture sector, which alters the food supply for the market in general and the producers in particular. When people have less water, they have low quality and quantity crop yields, resulting in food crises and economic difficulties.

Optimization of the Operation of Groundwater Intakes Using Two-Column Wells

The average number of wells at a typical water intake is 30–40; while the power of the submersible pump is usually 32–40 kW; which means that only at one well water intake the power consumption of electric pumping equipment during the hours of greatest water consumption can reach 900–1600 kW. In the structure of operating costs of well water intakes; the share of electricity costs reaches 85 %. Taking into account the requirements for reducing costs and water tariffs of housing and communal services enterprises as well as of water utilities; energy saving is an urgent task. The article considers the optimization of the operation of groundwater intakes with uneven water supply due to the use of two-column water intake wells instead of typical single-column ones. It is shown that the use of powerful pumps in single-column wells of such water intakes causes a sharp decrease in the dynamic water level in the borehole. On the one hand; this provokes the formation of colmating deposits in the filters due to their aeration; reduces the specific flow rate of the well and shortens the intervals between regenerations. On the other hand; this increases the geometric pressure of submersible pumps and energy consumption for lifting water. The theoretical foundations of determining the supply of pumps installed in single- and two-column water intake wells supplying water to the pressure filter of the water treatment plant are considered. An example of a comparative analysis of the operation of one working well with one powerful pump as part of a water intake of two single-column wells (working and reserve) to cover the entire water supply schedule and two two-column working wells containing one less powerful pump in each column is given. The energy efficiency of these pumping systems is investigated. As a result of calculations; it was found that when combining the operation of pumps of two-column wells during periods of peak; main and partial loads; the annual energy savings will amount to 33 %.

Устойчивость откоса грунтовой плотины при сработке водохранилища

Introduction. One of the possible factors acting on the stability of the slopes of an earth dam is the change of water levels in the reservoir or the downstream reservoir. A hazardous event can be a rapid drawdown of the reservoir due to, for example, an emergency or a technological necessity. Examples of collapse of ground dam slopes caused by changes in water level in the reservoir are given, as well as the results of estimation of the effect of reservoir drawdown on the stability of the upstream slope. A homogeneous enclosing dam made of loam on a non-rock base with a height of 29 m and upper and lower slopes of 1:3.5 was considered. The research was conducted for two cases of drawdown: slow drawdown with the rate of vertical water level decrease v = 0.25 m/day and fast (emergency) drawdown with the rate of v = 4.4 m/day. Materials and methods. Calculations of filtration of soil dam for steady and unsteady modes and assessment of stability of the dam slope are carried out by numerical method of finite elements using PLAXIS software package. The research statement and theoretical foundations, laid in calculations of filtration and stability of slopes are given. Results. Researches have shown that at decrease in a water level of a reservoir with the big speed the danger of infringement of stability of a slope increases. Conclusions. According to the practice of designing, the evaluation of change in the upper slope stability coefficient of the uniform ground protecting dike taking into account decrease of the water level in the reservoir taking into account filtration forces of unsteady filtration has been carried out. Variants with different rates of drawdown are considered. It is established that at high rates of drawdown the coefficient of slope stability decreases. The obtained results testify to necessity of taking into account filtration forces of unsteady filtration in evaluation of slope stability when designing homogeneous dams made of low-permeable soils.

Late Miocene reorganization of lake hydrological systems on the northern Tibetan Plateau linked to topographic growth

The hydrological cycles of lakes on the Tibetan Plateau (TP) have had profound impacts on the climatic and environmental evolution of the Asian interior and hence they are crucial for the well-being of the large human population of this region. The late Miocene is regarded as the most recent interval when the TP was extensively occupied by large paleolakes. However, it is unclear when and how these mega paleolakes shrank and the environment evolved into its present domination by desert and semi-desert. To address these issues, we conducted detailed analyses of diffuse reflectance spectroscopy, sedimentology, paleomagnetic-based tectonic rotation, and biogeochemistry of a Middle to Late Miocene sedimentary sequence in the Xining Basin in the North-eastern (NE) TP, supplemented by a spatiotemporal comparison of our results with equivalent records from adjacent regions. The results reveal a clear transition of the lacustrine system in the Xining Basin at ∼ 11 Ma, characterized by decreased water level and an increase in the oxidation state of the depositional environment. Combined with a summary of sedimentary evidence from seven different basins in the NE TP, we propose that a fundamental reorganization of lake hydrological systems occurred in the NE TP at ∼ 11 Ma. This reorganization was synchronous with tectonic deformation and topographic growth in the NE TP, as revealed by our new tectonomagnetic and other available tectonic evidence. Therefore, tectonic activity—rather than changes in climate or solar insolation, as previously proposed—was the principal factor responsible. This hydrological reorganization was of profound significance for the regional hydrological cycle and the climatic and ecological environment of Asia, because the elevated topography prevented the NE TP from regaining its Middle Miocene paleohydrological configuration.

Multidimensional ecosystem assessment of Poyang Lake under anthropogenic influences

Watershed anthropogenic activities, including pollutant discharge, sand mining, and upstream reservoir operation, have increased nutrient loads and decreased water levels and sediment concentrations in Poyang Lake, and thus affected the aqueous ecosystem. In this study, we developed an ecological model from the framework of AQUATOX to simulate the physical, chemical, and biological evolution of Poyang Lake under watershed anthropogenic influences, and used model output for a multidimensional ecosystem assessment of ecosystem structure, function, service, material flow, temporal dynamics, and collapse probability. The potential impacts of a proposed Poyang Lake water conservancy project (PYWCP) to build a sluice near the outlet of Poyang Lake to regulate lake level were explored. Results show that the watershed anthropogenic activities have worsened the Poyang Lake ecosystem. Specifically, the phytoplankton biomass increased, while benthos and fish decreased; the exergy, capacity of nutrient change, and the total biomass-gross primary production ratio decreased; as the lake's volume decreased, fishes’ trophic levels and food web robustness decreased, the food web shrank, single species dependence increased, and ecosystem stability decreased. The PYWCP could mitigate most of these effects, however, it would not recover Poyang Lake to historical conditions, and close monitoring with attention to sluice operational scheduling are required.