Decrease In Water Level Research Articles

Considerations in designing climate change assessments for complex, non-linear hydrological systems

Bias correction of climate model simulations is vital to allow climate change impacts to be assessed for water resources systems. However, there has been limited research to date on the implications of system non-linearity on bias correction approaches. Here we bias correct regional climate model simulations of precipitation and evapotranspiration and use the output to force hydrological and water balance models of five small, interconnected lakes located south west of Sydney. We show that substantial, non-linear storage within the lakes amplifies biases that are not evident when the climate forcing or even the hydrological model simulations are evaluated using daily distributions of the climate variables and streamflow.The non-linearity in the stage-storage relationships of the lakes means that each lake responds differently to the same climate forcings. For example, ensemble mean projections for one lake suggest increases in water level across the full distribution of lake levels, whilst other lakes are projected to have decreasing water levels up to the median of the distribution, but increases during wetter conditions. These differences are explained by the varying influence of potential evapotranspiration increases depending on the surface area of the lakes at different depths. Using bottom up climate change assessments, we further explore these non-linear responses of the lakes to different climate forcings. We show that bottom up climate change assessments can provide information on the relative role of potential evapotranspiration changes compared to precipitation changes, providing more guidance to ecosystem managers than just using bias corrected climate model simulations alone. The paper discusses opportunities for future work to improve representation of climate attributes important for storage dominated water resource and natural ecosystems.

Numerical simulation of deposit-landslide instability induced by water level decrease: a case study of RS deposit in Lancang River

Changes in reservoir water level often trigger landslides along the reservoir banks, which are common geological hazards that significantly affect the construction and operation of hydropower projects. In this paper, the stability of the RS reservoir landslide in the southwestern region of China is investigated. A discrete element seepage analysis model is constructed based on the theory of changes in the infiltration surface of the deposit caused by water level drawdown. The model is then embedded into a continuous-discontinuous three-dimensional numerical simulation method to systematically investigate the influence of reservoir water level decrease on the stability of the RS deposit. The results indicate that, under the condition of a sudden drop in reservoir water level decrease, the deposit experiences destabilization failure. Its sliding velocities are mainly influenced by seepage forces and gravity, while sliding displacements are influenced by seepage forces and topographic conditions. The landslide process shows distinct stratification characteristics. The portion of the deposit that slides into the river channel is mainly distributed between an altitude of 2655 m and 2870 m. The research results provide a scientific basis for studying the mechanism of slope failure and landslide disaster chain under the condition of reservoir water level lowering.

The State, Climate Change and Energy Transition in Zimbabwe, 1992–2022

This article examines the legislative, investment and policy environment that the Zimbabwean state is spearheading to transition the country from an overreliance on fossil fuels in response to the drawbacks of climate change. The need for this energy transition has become even more urgent due to decreasing water levels that can no longer sustain the country’s hydroelectric power outputs. A transition to other renewable energy sources and biofuels will lower the country’s carbon emissions. The article observes that while a lack of capital in large part hinders the country’s energy transition to invest in big renewable energy projects, the few small-scale projects underway are very opaque, (occasionally) transient and indistinct to the point of obscuring many potential benefits for the country’s citizens. This article relies on a review of primary material and sources from various repositories and a thorough review of secondary literature. This article was published open access under a CC BY licence: https://creativecommons.org/licences/by/4.0 .

Numerical investigation for the influence of suspended sediment on salinity distribution in the Qiantang Estuary, China

Numerous studies have demonstrated that high suspended sediment concentration (SSC) can change density distribution and affect water mixing, but few scholars have investigated this impact on numerical simulations of estuarian salinity distribution. The Qiantang Estuary is a macro-tidal estuary with high SSC, which has a more significant influence on water density than that of salinity. Therefore, this paper established a three-dimensional (3D) numerical model coupling flow, salinity and SSC based on Delft3D and first analyzes the impact of SSC on salinity distribution under different runoff and tidal conditions in the Qiantang Estuary. The results indicated that simulated salinity generally decreases when considering the impact of SSC, suggesting a weakening effect on saltwater intrusion. The distribution of salinity difference (ΔS) and SSC show a strong spatial and temporal correlation, and ΔS peak increases and shifts upstream as the tidal range increases or runoff discharge decreases. The mechanism of SSC influencing saltwater intrusion can be summarized as follows: On the one hand, SSC increases the water density, which weakens the driving force for saltwater to move upstream, causing a decrease in flood current velocity and water level, and thereby diminishing the advective transport of salinity. On the other hand, SSC enhances density stratification, which weakens vertical turbulence and reduces the dispersive transport of salinity. These combined effects reduce both the advective and diffusive salinity fluxes during the flood tide, ultimately leading to a decrease in upstream salinity. Therefore, neglecting this effect in estuaries with high SSC can cause significant deviations in salinity simulation results, especially under low-flow and high-tide conditions.

Integrating standardized indices and performance indicators for better drought assessment in semi-arid coastal aquifers

Aquifers in arid and semi-arid coastal regions, such as along the Mediterranean rim, are severely affected by droughts. The natural decrease in water levels is often exacerbated by excessive abstraction, resulting in both degradation of water quality and the risk of seawater intrusion. In these regions it is crucial to conduct thorough monitoring of wells, employing a wide range of indicators to forecast and mitigate the consequences of decreased precipitation and intensified pumping. This study proposes an analysis and monitoring methodology involving the calculation of performance indicators based on the Standardized Groundwater level Index (SGI), supplemented with information on the optimal accumulation time of the Standardized Precipitation Evapotranspiration Index (SPEI). Atmospheric reanalysis datasets and in-situ groundwater level observations are used together to derive the groundwater system memory and find consistent optimal SPEI accumulation times at each individual location. The inverse of memory derived from the autocorrelation of the SGI is used to estimate each well's ability to recover from drought conditions. This value provides the most reliable indication of resilience and sustainability. In the Algarve, the average regional variability of groundwater level is well captured by the SPEI-12 index. However, groundwater memories and optimal SPEI accumulation times are spatially very heterogeneous varying between SPEI-5 and SPEI-48. Wells with shorter memories (<6 months) demonstrate greater sustainability, whereas those with longer memories (>16 months), whether situated inland or along the coast, exhibit lower resilience and lower sustainability. Coastal wells with groundwater levels close to sea level, exhibiting minimal resilience, are of particular concern and require intensified monitoring efforts to adapt management strategies.

Seasonal Dynamics of Salt Licks and Their Use by Wildlife in Amazonia

In certain Amazonian regions, 25% of hunting occurs at salt licks, sites rich in natural minerals often near creeks prone to periodic flooding. Here, animals engage in geophagy for mineral supplementation and detoxification what enables local hunter to observe their behaviour while waiting their target. Our study evaluates seasonal salt lick availability and wildlife usage, using interviews and obtained information on 31 vertebrate species across 56 salt licks in the Central Amazon. While soil and water consumption attract wildlife, species also visit for bathing, predation, and other behaviors. In general, the season with the highest wild species abundance was the receding floodwaters season, because the creeks’ water level decreases and so the salt lick is exposed. Conversely, during the flood pulse, interviewees perceived that the majority of salt licks are not visited by most species because they are often covered by water. Most of the interviewees (74,46%) said that salt licks are one of the main places where they hunt, however the hunting at salt licks is only done during the receding floodwaters season. Our findings shed light on the ecological significance of salt licks in Amazonia and their role in supporting diverse wildlife communities.

Performance evaluation of the SMART passive safety injection system against the SBLOCA scenario with the SMART-ITL facility

A set of system performance tests has been performed and the thermal-hydraulic behaviors were investigated for the passive safety injection system (PSIS) of the SMART design. Major thermal-hydraulic characteristics of core cooling in reactor coolant system and safety injection (SI) in PSIS were investigated using the SMART-ITL. The parametric effects of break size, break location and train number on the PSIS performance were discussed with the relevant SMART-ITL data. Compared with the 2.0 inch SI line break test, the 0.4 inch SI line break test has a milder change of system parameters. The pressure is reduced more quickly, the decrease of water level is slower and the break mass flow rate is higher during the pressurizer safety valve line break than during the SI line break. Major thermal-hydraulic parameters were compared among single, two and full train operation of the PSIS focusing on the effect of train number. It was shown that multiple trains of CMT and SIT were operated independently and the reactor vessel (RV) inventory increased proportionally with the addition of each train. Sufficient SI water was injected into the RV in a passive manner to cool down the reactor core efficiently during the full train test.

Assessments of Land Subsidence in the Tehran Metropolitan Using Satellite Radar Interferometry Technique

Background and objective Many cities in the world have land subsidence problems because of environmental issues related to urban development. The arid and semi-arid climatic conditions prevailing in most of the interior regions of Iran and the need for the increasing industrial, agricultural, and drinking water exploitation from underground water resources, as well as urban development, have increased the occurrence of land subsidence in Iran, especially in the metropolis of Tehran. This study aims to assess land subsidence in Tehran, Iran, using the satellite radar interferometry (InSAR) technique. Method In this research, 31 images of Sentinel-1 were processed using the time series of persistent scatter interferometry (PSI) in 2022, and a map of the average annual rate of land subsidence in Tehran metropolis was prepared. Finally, after validating the results of interferometry with GPS station observations, the relationship between land subsidence and exploitation of underground water resources was examined as the most important factor in ground surface changes in the study area. Results The findings showed a decreasing trend in land subsidence from plain to urban areas. The highest land subsidence, with a rate of -43 mm per year occurred in the southern and southwestern parts of Tehran. Districts 10, 11, 12, 16, 17, 18, 19, and 20, which comprise about 26% of Tehran’s population, were experiencing land subsidence. The drop in the water level of observation wells was considerable in the areas where the highest rate of land subsidence occurred. Another finding of the research was the decrease of the underground water level from the north to the south of Tehran, indicating that the water depth in the southern areas of Tehran decreased due to human activities such as water pumping. Conclusion There is an increasing pressure in the aquifer through pumping water from wells in the study area for various industrial, agricultural and drinking water uses which has led to the increase in the occurrence of land subsidence.

HYDROLOGICAL REGIME OF THE IKVA RIVER (SOUTHERN BUG BASIN)

This article reveals the issue of a detailed study of the hydrological regime of small plain rivers in the presence of data from regular observations. The Ikva River, the object of our study, belongs to the Southern Bug basin and is its small tributary, on which a hydrological indicators monitoring station has been operating since 1939. Since 1955, a continuous series of observations has been available, which allowed us to carry out a detailed analysis and description of the main hydrological characteristics – levels (H, cm) and water flows (Q, m3/s), to evaluate their fluctuations in time, cyclicity and the relationship Q= f(H). The construction of the corresponding graphs confirmed that the Ikva River is characterized by cyclic flow fluctuations, and since 1965 we have already observed two complete cycles of fluctuations in water level lasting about 30 years. At the moment (2022), the flow indicators record the minimum of the low-water phase of the second cycle, so we can expect an increase in the flow in the near future and the transition to a new cycle. We have also determined that the amplitude of water level fluctuations of the Ikva River at the post in the village of Stara Sinyava over many years is 60 cm, and varies from a minimum of 75 cm (1957) to 135 cm (1981), that is, a little more than 0.5 meters in total. This agrees quite well with the literature data and estimates of other authors, considering the plain nature and small size of this object. The long-term course of the water levels of the Ikva River is characterized by a slight increase, while the long-term fluctuations of the average water flow at this station also do not have a large amplitude: from 0.66 m3/s (2020) to 3.64 m3/s (1979) i.e. 2.98 m3/s. At the same time, the general trend line for multi-year cost fluctuations shows, on the contrary, a tendency to decrease them. Therefore, we can state that the graphs of multi-year costs and levels are not synchronous, which is evidence of the manifestation of vertical channel deformations in the area of the post. As the water level increases, the decrease in water consumption is a direct sign of siltation of the riverbed in this area and the raising of the bottom level due to accumulative processes over a long period. The largest amplitudes are characterized by the parameters of the maximum runoff, that is, the amplitudes of the maximum levels (∆Нmax = 168 cm) and maximum flows (∆Qmax = 92.9 m3/s), which is not surprising, because we are talking about the characteristics of the period of floods and inundations, which are always marked by significant fluctuations in time. An interesting fact, identified for us for the first time, is that the characteristics of the minimum flow of the closed period of the channel are characterized by higher amplitudes than the characteristics of the open period. Therefore, the summer low water is more pronounced than the winter low water, which means that in the warm period (summer), the lack of precipitation more clearly provokes a decrease in water levels and flows in the channel system than during the winter period. The reason can be both winter thaws and the specifics of the groundwater regime. Key words: hydrological regime; water level; water flows; hydrological cycle; low water phase; high water phase; relationship Q=f(H).

Landscape Pattern Changes of Aquatic Vegetation Communities and Their Response to Hydrological Processes in Poyang Lake, China

Hydrology is an important environmental factor for the evolution of wetland landscape patterns. In the past 20 years, Poyang Lake, the largest freshwater lake in China, has experienced significant inundation shrinkage and water level decrease, posing a significant threat to the local vegetation community. To explore the potential relationship between aquatic vegetation and hydrological processes in the recent hydrological situation, in this study, the landscape patterns of aquatic vegetation communities in Poyang Lake were studied using time-series Landsat remote sensing images and a support vector machine classifier. The stepwise regression analysis method was adopted to analyze the relationship between the vegetation area and hydrological factors. The results indicated that the area of submerged and emergent vegetation in the entire lake decreased significantly from 2001 to 2017, whereas the area of moist vegetation showed a remarkably increasing trend. The average distribution elevation of the submerged vegetation increased by 0.06 m per year. The corresponding landscape patterns showed that the degree of fragmentation of aquatic vegetation communities in Poyang Lake increased. Several hydrological factors were selected to quantify the potential impact of water level fluctuations. The correlation analysis results indicated that hydrological conditions during the rising- and high-water periods may be the key factors affecting the area of aquatic vegetation. This study systematically investigated the evolution of vegetation communities in Poyang Lake wetlands over the past two decades, which contributes to the protection and management of this unique ecosystem.

Effect of topography and hydrological change on solute transport at the sediment-water interface in seasonal lakes

Study regionThe Poyang Lake is located in northern Jiangxi Province, which is the largest fresh water in China. The upstream connection with rivers and downstream access to the Yangtze River create seasonal hydrological regimes, resulting in over 100 seasonal lakes within the floodplain. These lakes provide important habitats for migratory birds to forage and nest during dry seasons, and contribute to floodwater regulation during wet seasons, maintaining lake ecosystem. Study focusThis study has combined laboratory experiments and numerical simulations to mechanically analyze the effect of the depth, width, slope of seasonal lakes, water level amplitude and dry season periods on water recharge patterns, exchange fluxes and solute transport characteristics at the sediment-water interface. New hydrological insights for the regionReducing the lake area by 33% through adjustments in depth or slope significantly reduces solute transport range (12.81% and 6.5% within 120 min) and high velocity area. The sensitivity of the solute amount in the lakebed to depth is the highest, followed by slope and width. Decreasing water level amplitude during dry seasons increases the flow velocity within the beach, facilitating short-term solute transport towards the lakebed. Extending the duration of dry periods increases cumulative flux of solutes entering the lakebed. These findings contribute to the ecological restoration efforts in floodplains and water pollution control measures.

Exploring the relationship of the winter-spring crop’s rice yield with meteorological drought and water resources in Ben Tre province

Recent environmental changes have significantly impacted rice cultivation in Ben Tre province, the Vietnamese Mekong Delta (VMD) coastal province. This research employed the Mann-Kendall (MK) non-parametric method and Sen’s slope (SS) technique to detect trends in the rice yield of the winter-spring crop (WSC) in Ben Tre province and environmental parameters from 2009 to 2020. These environmental parameters include the meteorological drought index and key water resource metrics, potentially affecting the region’s rice yield. Furthermore, it established the relationship between these environmental parameters and rice yield using multiple linear regression. The results indicated an average decrease of 0.13 ton/ha/year in the WSC’s rice yield, with a severe reduction to 2.86 ton/ha in 2016. This decline in rice yield is likely attributed to environmental shifts, particularly during years with extreme hydrological events. The study found that during the months of dry season, from January to April, there was a decrease of 0.14 per year in the minimum Standardized Precipitation Evapotranspiration Index (SPEI-4min) at the Ben Tre meteorological station; an increase in the minimum daily discharge at the Tan Chau station (QTCmin) by 81 m3/s/year; a decrease in the mean daily water level at the My Thuan station (QMTmean) by 0.22 cm/year; and an increase in the maximum daily water level at the Ben Trai station (HBTmax) by 0.67 cm/year. However, the maximum daily salinity concentration at the Tra Vinh station (STVmax) showed no significant trend, oscillating between 6.5 and 15 g/l, potentially because the three-hourly monitoring intervals might not have fully captured peak salinity levels. The regression model identified SPEI-4min (with a Correlation Index (CI) of 0.450) and STVmax (CI = 0.372) as the primary factors influencing rice yield. Additionally, QTCmin and HBTmax were also significant, though to a lesser extent, with correlation indices of 0.310 and 0.303, respectively. Conversely, QMTmean had a relatively minor influence, with a correlation index of 0.136. These findings are crucial to developing adaptive strategies and policies for improving the resilience of rice production in the study province and throughout the VMD.

Water Level Fluctuation Effect on Fish Reproduction Success

Alteration of water levels of the lake/reservoir due to changes in river discharges, upstream abstraction, and drawdown regulation due to hydropower generation has been reported as among the major challenges to fish physiology and ultimately reproduction. Variations in lake/reservoir water levels influence biodiversity and the abundance of lake/reservoir biota. Variations have the greatest impacts in the littoral zones hence, interfering with fish spawning, incubation, and hatching of eggs, as well as the development of larvae, postlarvae, and juveniles. This particular paper reviews the literature available on the effect of the reservoirs/lakes’ water level fluctuations on fish reproduction success using the documentary view method. The literature argues that water level fluctuations have both positive and negative impacts depending on frequency, magnitude, and duration and the species exposed. Extreme fluctuations tend to bring more adverse impacts. It further indicates that extreme and untimely water level fluctuation has direct impacts on the aquatic habitats and ultimately impacts fish assemblage and their populations. Few articles indicate the range of decrease or increase of water level, duration of such events, and effects they have on reservoir/lake ecosystem functions and fish physiology. Nevertheless, quantification of moderate and extreme water level fluctuation and associated effects is lacking. Although water level fluctuation is an important environmental cue for aquatic organisms, literature shows that the reduction of extreme water level variations especially multiannual variations is vital for fish reproduction. Therefore, upstream water use and reservoir operations should take into consideration the effects of water level fluctuations on reservoir structure, biological functions, and ultimate effects on fish reproduction.

Multi-objective optimization of farmland water level and nitrogen fertilization management for winter wheat cultivation under waterlogging conditions based on TOPSIS-Entropy

Aiming at the problems of reduced winter wheat yield and aggravation of nitrogen leaching pollution caused by the waterlogging in the Middle-Lower Yangtze Plain, China, a two-year field experiment with three farmland water levels (W40, W60, W80) and three nitrogen application rates (N150, N225, N300) as well as a non-waterlogged treatment (CK) was carried out, to investigate the coupling effects of farmland water level and nitrogen application rate on the plant growth, grain yield, crop water productivity (WPC) and nitrogen load with waterlogging conditions. Three man-made waterlogging events were applied at winter wheat jointing-booting stage, heading-flowering stage and grain filling stage, respectively. The results indicated that with the farmland water level decreased from −40 cm to −60 cm and the nitrogen application rate increased from 150 kg∙ha−1 to 225 kg∙ha−1, the plant height, aboveground dry matter, leaf area index, spike length, grain yield, effective panicles, grain number per ear, 1000-grain weight and WPC in the waterlogging field increased significantly. However, since the nitrogen application rate exceeded 225 kg∙ha−1 and farmland water level lowered more than −60 cm, the favorable effects of nitrogen application rate and farmland water level for winter wheat growth and production reduced. Additionally, both the nitrogen load and partial factor productivity of nitrogen (PFPN) increased with the decline of farmland water level, while the nitrogen load increased and the PFPN decreased with the increasing nitrogen application rate. The raise of nitrogen rate from 150 kg∙ha−1 to 225 kg∙ha−1 was beneficial to plant growth, however, the increase of nitrogen application resulted in the decrease of PFPN and increase of drainage nitrogen loads. Compared with the water farmland water level of −40 cm and nitrogen application rate of 150 kg∙ha−1, the increase of nitrogen application rate and the decrease of farmland water level in the range of 50%-100% resulted in yield raise by 5.78%-32.29% approximately and the increase of nitrogen load by 36.20%-178.44% approximately. The comprehensive evaluation with TOPSIS-Entropy method for plant growth, grain yield, WPC, PFPN and nitrogen loads suggested that, the appropriate nitrogen application rate for winter wheat in the waterlogging areas of Middle-Lower Yangtze Plain in China was 225 kg∙ha−1, and the proper farmland water level was lowering to −80 cm in wet year and −60 cm in dry year within 3 days after waterlogging.

Comparative study on volume conservation among various SPH models for flows of different levels of violence

The weakly-compressible smoothed particle hydrodynamics (WCSPH) models offer distinct advantages in simulating free-surface flow. Within the rapidly evolving WCSPH field, Classical WCSPH model, based on the artificial viscous term, and its derived models, which additionally introduce numerical diffusive terms into the continuity equations - including the δ-SPH, δ-SPHC, δ-SPHC+, δ-LES-SPH, and δ-SPHF models have gained prominence recently. The numerical diffusive term is found to alter the particle distributions in the free-surface region, leading to a change in the mean water level that reflects the volume conservation, which might result in inaccuracies in some simulations. This study evaluates the volume conservations of the aforementioned WCSPH models for flows at quasi-hydrostatic states evolved from varying levels of flow violence under prolonged simulations, through a series of numerical tests involving hydrostatic, standing-wave, and dam-break cases. For the hydrostatic and standing-wave cases, the performance of different types of WCSPH models remains consistent overall. The Classical WCSPH and δ-LES-SPH models exhibit minimal changes in volume, with almost no decrease in the mean water level occurring. The δ-SPH, δ-SPHC, δ-SPHC + models demonstrate decreases in the mean water level converging to around 0.2 times the SPH particle diameter (Δx), indicating favorable volume conservation. Conversely, the δ-SPHF model consistently exhibits a decrease in the mean water level exceeding 1 Δx at t = 2000s in a linear fashion, resulting in a noticeable reduction in volume. Under the dam-break case, most of the mean water levels simulated by different models experience a small increase, which is close to the decrease observed under the hydrostatic and standing-wave cases with corresponding models. Only the δ-SPHF model continues to show a continuous decreasing tendency. In summary, considering volume conservation, the δ-LES-SPH model demonstrates the best performance (excluding the Classical WCSPH model as it cannot simulate violent flow), followed by the δ-SPHC, δ-SPHC+, δ-SPH and δ-SPHF models.

Analysis of the Impact of Hydraulic Gates on a Stabilized Tidal Inlet Structure: Mathematical Model and Data Measurements

Tidal inlet structures are engineering projects with associated benefits related to flood control, water quality enhancement, and coastal protection. This study analyzes the performance of hydraulic gates on a stabilized inlet in estuarine systems by developing a simplified hydraulic model that considers inlet and outlet water levels. The proposed model was applied to the stabilized tidal inlet structure in Cartagena de Indias, Colombia. This model offers a practical tool for engineers and designers operating estuarine systems. The analysis focuses on the coastal lagoon of Ciénaga de la Virgen. The proposed model was successfully calibrated using two water sensors, with extreme input and outlet flow rates of approximately 260 m3/s and 110 m3/s, respectively. The average daily output volume in the system is 3,361,000 m3, while the average daily input volume is 3,200,000 m3. Consequently, the manipulation of the opening gates results in a decrease in the estuarine water level, potentially by as much as 25 cm, which local authorities can use to make decisions to reduce extreme water levels during flooding events.

Distinct differences of vertical phytoplankton community structure in mainstream and a tributary bay of the Three Gorges Reservoir, China.

The vertical distribution of phytoplankton plays a crucial role in shaping the dynamics and structure of aquatic communities. In highly dynamic reservoir systems, water level fluctuations significantly affect the physiochemical conditions and the phytoplankton community. However, the specific effects on the vertical characteristics of phytoplankton between the mainstream and the tributary bay of the reservoir remain unstudied. This study investigated the vertical aspects of phytoplankton density, biomass, α and β diversity through monthly sampling over two years in the mainstream (Chang Jiang, CJ) and a tributary bay (Xiang Xi, XX) of the Three Gorges Reservoir in China. Phytoplankton density and biomass were significantly higher in XX, indicating an increased risk of algal blooms in the tributary. The phytoplankton community in CJ showed more stable species-environment relationships, a lower Shannon index and a higher evenness index, suggesting a relatively simple structure and a more uniform distribution of phytoplankton among different water layers. Conversely, XX showed greater differences between water layers (higher β diversity), with significant negative correlations with water level and positive correlations with DO difference, dissolved silica (DSi) difference, and stratification. Peak phytoplankton density and biomass, as well as high β diversity in XX, occurred during periods of decreased water levels with strong stratification in spring and summer. A structural equation model complemented by path analysis revealed that a decrease in water level could increase β diversity either directly through internal processes with extended residence time or indirectly by modifying stratification and the vertical distribution of DSi in XX. Therefore, a proposed water quality management strategy for XX was to increase the water level or reduce β diversity by implementing artificial mixing during stratification periods. Overall, this study lies in its comprehensive investigation of the vertical characteristics of the phytoplankton community in both the mainstream and the tributary bay of the Three Gorges Reservoir, elucidating the significant impact of water level fluctuations and providing insights for targeted water quality management strategies in the tributary bay to mitigate potential ecological impacts.

Biomonitoring of the surface waters of the Volyntsevo reservoir using the fluorimetry method

The article examines the state of the drinking Volyntsevo reservoir and its tributaries in conditions of significant changes in the hydraulic regime and pollution by waste mine waters. The state of algoflora of a water body is considered, the results of studying the species composition of phytoplankton, the content of basic photopigments and photosynthetic activity of microalgae are presented. The study presents the results of the application of the method of fluorimetric assessment of the state of phytoplankton cells as the main bioindicator of the state of the aquatic environment. The research was conducted in the vicinity of Yenakievo for the Volyntsevo reservoir and the Bulavin river. These water bodies are subject to significant man-made impacts: as a result of intensive water use of reservoir resources, there has been a significant decrease in water levels and, as a result, a deterioration in water quality. The conducted studies have shown a significant excess of the permissible standards for the content of magnesium ions, sulfates, total hardness and alkalinity in water samples. The negative impact of surface water pollution on the species composition of algoflora, as well as the photosynthetic activity of phytoplankton cells, has been shown. The obtained materials can serve as a basis for further monitoring of drinking reservoirs in the region. The current situation requires constant monitoring observations aimed at identifying and eliminating all sources of pollution of the studied water bodies.

A CMIP6 Multi-Model Analysis of the Impact of Climate Change on Severe Meteorological Droughts through Multiple Drought Indices—Case Study of Iran’s Metropolises

This study extensively explores the impact of climate change on meteorological droughts within metropolises in Iran. Focused on Tehran, Mashhad, Isfahan, Karaj, Shiraz, and Tabriz, this research employed CMIP6 climate models under varying climate change scenarios (SSPs) to forecast severe meteorological droughts spanning the period from 2025 to 2100. The investigation utilized a diverse set of drought indices (SPI, DI, PN, CZI, MCZI, RAI, and ZSI) to assess the drought severity in each city. This study is crucial as it addresses the pressing concerns of rapidly decreasing water levels in Iran’s dams, serious declines in underground aquifers, and the compounding issues of land subsidence and soil erosion due to excessive groundwater withdrawal in the face of severe droughts. This study culminated in the generation of box plots and heatmaps based on the results. These visual representations elucidated the distribution of the drought values under different indices and scenarios and provided a depiction of the probability of severe drought occurrences until the end of the century for each city. The resulting findings serve as invaluable tools, furnishing policymakers with informed insights to proactively manage and fortify metropolitan resilience against the evolving challenges posed by a changing climate.

Variability in surge levels in communities adjacent to the Houston Ship Channel industrial Corridor to changes in Hurricane characteristics

ABSTRACT The sensitivity of hurricane-driven storm surge in the Houston Ship Channel Industrial Corridor to variations in storm characteristics is studied. Hurricane surge from Hurricane Ike from 2008 was simulated using the Delft3D Flexible Mesh model. Use of the HURDAT2 wind parameter database allowed alteration of relevant hurricane characteristics to develop these alternate scenarios. Moving the actual landfall location of Ike toward the southwest at a distance of 50 km yielded a 123% increase at Manchester relative to observations during the storm. Relocation of the landfall location 200 km further southwest caused a 40% decrease in water level at the Galveston Bay entrance relative to observed values, but with a corresponding 50% water level increase at Manchester. Reduction of the storm forward speed to 25% of the actual speed over the nearshore led to a 25% increase in water level in Manchester over recorded values, while a 57% reduction of the storm forward speed over land increased water levels in Manchester by 30%. Incorporating river flow also identified locations where Galena Park’s residual floodwater is likely to remain after flooding. The results of this work can be used to guide modeling efforts of storm impacts on areas with narrow waterways.