Flood Season Research Articles

Assessing landslide damming susceptibility in Central Asia

Abstract. Central Asia regions are characterized by active tectonics, high mountain chains with extreme topography with glaciers, and strong seasonal rainfall events. These key predisposing factors make large landslides a serious natural threat in the area, causing several casualties every year. The mountain crests are divided by wide lenticular or narrow, linear intermountain tectonic depressions, which are incised by many of the most important Central Asia rivers and are also subject to major seasonal river flood hazard. This multi-hazard combination is a source of potential damming scenarios, which can bring cascading effects with devastating consequences for the surrounding settlements and population. Different hazards can only be managed with a multi-hazard approach coherent within the different countries, as suggested by the requirements of the Sendai Framework for Disaster Risk Reduction. This work was carried out within the framework of the Strengthening Financial Resilience and Accelerating Risk Reduction in Central Asia (SFRARR) project as part of a multi-hazard approach with the aim of providing a damming susceptibility analysis at a regional scale for Central Asia. To achieve this, a semi-automated GIS-based mapping method, centered on a bivariate correlation of morphometric parameters defined by a morphological index, originally designed to assess the damming susceptibility at basin/regional scale, was modified to be adopted nationwide and applied to spatially assess the obstruction of the river network in Central Asia for mapped and newly formed landslides. The proposed methodology represents an improvement to the previously designed methodology, requiring a smaller amount of data, bringing new preliminary information on damming hazard management and risk reduction, and identifying the most critical area within the Central Asia regions.

How much nutrient reaches a stream: Insights from a hybrid model and implications for watershed nitrogen export and removal

Excess nitrogen (N) discharged into streams and rivers degrades freshwater quality and threatens ecosystems worldwide. Land use patterns may influence riverine N export, yet the effect of location on N export and removal is not fully understood. We proposed a hybrid model to analyze N export and removal within the watersheds. The proposed model is satisfied for the riverine N modelling. The KGE and R2 are 0.75 and 0.72 in the calibration period which are 0.76 and 0.61 in the validation period. Human-impacted land use may modify the N yield in the watershed, and the net N export from built-up to the in-stream system was highest in the urbanized sub-watersheds (0.81), followed by the agricultural sub-watersheds (0.88), and forested sub-watersheds (0.96). Agricultural activities make a large contribution to the N exports in the watersheds, and the mean N input from the agricultural land use to in-stream were 2069–4353 kg km−2 yr−1. Besides, the excess inputs of N by overapplication of fertilizer and manure during the agricultural activities may increase legacy N in soil and groundwater. Biological processes for the riverine N removal may be controlled by the available substrate in the freshwater system, and temperature sensitivity of denitrification is highest in the flood seasons, especially for the human-impacted sub-watersheds. The riverine biological processes may be limited by other competitions. Our model results provide evidence that quantity and location of specific land use may control biogeochemistry within watersheds. We demonstrate the need to understand nutrient export and removal within watersheds by improving the representation of spatial patterns in existing watershed models, and we consider this study to be a new effort for the spatially explicit modeling to support land-use based N management in watersheds.

Analysis of extreme precipitation variation characteristics in mountain grasslands of arid and semi-arid regions in China

Introduction: With global warming, the disaster losses caused by extreme precipitation events are increasing. The poor natural conditions and climate change make the arid and semi-arid mountainous grassland area a sensitive region of climate change. The study on the spatio-temporal variation characteristics of extreme precipitation events in this region is helpful to improve the ability of climate prediction and disaster prevention and reduction in grassland.Methods: Based on the daily precipitation data of four meteorological monitoring stations in the Yinshanbeilu from 1970 to 2020, the trend analysis, M-K test and wavelet analysis were used to select seven typical extreme precipitation indicators to analyze the temporal and spatial characteristics of extreme precipitation.Results and Discussion: The results showed that the precipitation in the Yinshanbeilu increased in the past 51a, and the number of heavy rain days increased significantly. The significance test of CDD and CWD showed that the number of continuous dry days and continuous wet days decreased abruptly. The spatial analysis showed that the high value areas of R95p, R95d and PRCRTOT were all located in Siziwang Banner, and it could be concluded that the extreme precipitation risk was the highest in Siziwang Banner, while the low value areas of SDII, Rx1day, R95p and PRCRTOT were all located in Sonid Right Banner, which could be inferred that the Sonid Right Banner was relatively dry. The first main cycle of the seven indexes of extreme precipitation almost runs through the whole time series, and the starting point of the minimum main cycle changes inconsistent. In addition to the number of consecutive dry days, the other indices have a good correlation with annual precipitation, flood season and monthly precipitation from June to September, and July is the peak period of extreme precipitation events.

Tall wheatgrass response toward phosphorus deficiency: a constraint to its use as a forage resource in marginal soils

Tall wheatgrass is cultivated for pasture in marginal areas around the world due to its tolerance to abiotic stress including seasonal droughts and floods, as well as saline and alkaline soils. However, there is concern about its biomass productivity, which often does not exceed that of natural pastures. In this work we hypothesize that tall wheatgrass is a plant more sensitive to low P availability than commonly assumed. A glasshouse sand culture experiment was conducted to analyze morpho-physiological responses of tall wheatgrass to different P availability levels: 1 µmol L−1 phosphorus (severe deficiency, P1), 10 µmol L−1 phosphorus (representative value of soil solution in the region, P10) and 500 µmol L−1 phosphorus (full P supply, P500). Our results show that both limiting P conditions strongly decreased plant development and biomass accumulation, and altered above- and below-ground morphology, in comparison with P500 plants. The latter, in turn, had relative growth rate values comparable to those of other cultivated grasses under non-limiting conditions. In both P-deficient treatments, plant development was severely delayed starting from leaf number 3, even when P concentration in the pseudostem at early stages was similar or even higher than that of P500 plants. Our results suggest that developmental inhibition of tall wheatgrass at low P supply may be the consequence of a specific plant response to P concentration in soil solution, rather than to direct P starvation in plant tissues, and underlines the need of improvement of this species to enhance productivity in this environment.

Study on Response of Evapotranspiration Consumption of Forest and Grass Vegetation to Natural Precipitation in Northwest Loess Plateau

In this paper, the evapotranspiration balance of forest and grass vegetation in the Loess Plateau of Northwest China in different regions was analyzed using 6 indexes in 3 categoriess, namely, evapotranspiration ratio (Ea/Q, Ep/Q), evapotranspiration difference (Q-EA, Q-EP), and actual (potential) water supply ratio (1-Ea/Q, 1-Ep/Q). It is used to objectively reflect the suitability of different types of vegetation in different periods of growth based on precipitation. In another words this suitability reflects the support capacity of natural rainfall to vegetation consumed water through evapotranspiration under the specific climate environment of the Loess Plateau. The results show that: (1) The actual evapotranspiration water consumption of all types of vegetation in this region increased significantly in the first three months of the growth period from April to June, resulting in a relatively high moisture dryness index of vegetation with an average k value of 0.44. The main reason was that natural precipitation was less at this stage, and the gradually rising temperature strengthened the transpiration of most vegetation. The forest was the most stressed. At the end of May and the beginning of June, with the increase of natural precipitation, the average k value of all types of vegetation began to decline. From July to September, due to the flood season in this region, the precipitation increased sharply, and the moisture dryness index was in the lowest range of the whole growth period, and the average k value varied between 0.26 and 0.30 with the lowest value was 0.26 at the end of August and the beginning of September. (2) It is obvious that the water stress of forest is higher than that of shrub and grassland. It is fully indicated that the difference of transpiration caused by the difference of vegetation types leads to the difference of actual evapotranspiration water consumption of different vegetation types.

Variations in provenance and transport of terrestrial organic matter in the Changjiang River during the flood season

River is a crucial channel for the transport of terrestrial organic carbon (OCterr) into the sea, and has significant implications for the global carbon cycle. However, with the intensification of human activities within the watershed (such as dams and changes in land use), the sediment and OCterr output from rivers have significantly decreased. To study the influence of human activities on the provenance and transport of particulate organic carbon (POC) exported from the Changjiang River Basin (CRB), we collected suspended particulate matter samples during the rainy season of 2021. The POC content exhibited an increasing trend from the headwater zone to the estuary. Results of three-end-member mixing model indicated that both soil-derived and autochthonous OC (OCauto) contributed approximately more than 40.0 %. Notably, OCauto experienced a significant increase from the Three Gorges Dam (TGD) to estuary in the mainstem, attributed to the sediment interception effect of the TGD. The POC contents in the headwater zone and Jinshajiang River in 2021 were lower compared to those in 2007, which can be attributed to a decrease in cultivated land area and increase sediment trapping by cascade dams. Affected by TGD, the POC content in the middle and lower reaches as well as the delta zone first decreased in 2003 and then increased from 2007 to 2021. Additionally, the degradation of lignin phenols and n-alkanes was influenced by the TGD, which prolonged the retention time of terrestrial plants. Compared to previous studies, the decrease in soil-derived OC and increase in OCauto in CRB, influenced by dams and land use, could have long-lasting effect on carbon burial in the ECS.

Response of Streamflow to Future Land Use and Cover Change and Climate Change in the Source Region of the Yellow River

This study utilizes meteorological and leaf area index (LAI) data for three shared socioeconomic pathways (SSP1–2.6, SSP2–4.5, and SSP5–8.5) from four general circulation models (GCMs) of the sixth climate model intercomparison project (CMIP6) spanning from 2015 to 2099. Employing calibrated data and incorporating future land use data under three SSPs, the distributed hydrology soil vegetation model (DHSVM) is employed to simulate streamflow in the source region of the Yellow River (SRYR). The research aims to elucidate variations in streamflow across different future scenarios and to estimate extreme streamflow events and temporal distribution changes under future land use and cover change (LUCC) and climate change scenarios. The main conclusions are as follows: The grassland status in the SRYR will significantly improve from 2020 to 2099, with noticeable increases in temperature, precipitation, and longwave radiation, alongside a pronounced decrease in wind speed. The probability of flooding events increases in the future, although the magnitude of the increase diminishes over time. Both LUCC and climate change contribute to an increase in the multi-year average streamflow in the region, with respective increments of 48.8%, 24.5%, and 18.9% under SSP1–2.6, SSP2–4.5, and SSP5–8.5. Notably, the fluctuation in streamflow is most pronounced under SSP5–8.5. In SSP1–2.6, the increase in streamflow during the near future (2020–2059) exceeds that of the distant future (2059–2099). Seasonal variations in streamflow intensify across most scenarios, leading to a more uneven distribution of streamflow throughout the year and an extension of the flood season.

Design and Study of a Sediment Erosion Test Device for a Single-Flow Channel in the Guide Apparatus of a Reaction Hydraulic Turbine

Sediment erosion damage is one of the main causes of structural failure in reaction turbine units. To study the mechanism through which sediment erosion affects the water-guiding mechanism of a reaction turbine unit, this study obtained the average concentration and particle size of sediment during the flood season based on the statistics of the measured sediment data from the power station. Additionally, the characteristics of the solid–liquid two-phase flow of the diversion components of the reaction hydraulic turbine were numerically calculated. Based on the velocity triangle change in the guide apparatus and the flow similarity principle, a flow-around wear test device for the guide apparatus of the reaction turbine was designed. Furthermore, the similarity of the sand–water flow field between the guide apparatus of the prototype unit and the test device was compared and analyzed. The results demonstrated that the sand–water flow field of the diversion components of the prototype unit was axisymmetric and exhibited a potential flow distribution. Additionally, uniform sand–water flow occurred within the guide apparatus, with a small sand–water velocity gradient near the wall of the stay vanes (SV) and the guide vanes (GV). The maximum volume fraction of sediment particles was observed in the tailing area of the spiral casing, indicating an enrichment phenomenon of sediment particles. The velocity of the sediment particles on the surface of the guide vane in the single-channel sediment wear test device and prototype unit ranged from 6.2 to 7.8 m/s, and the velocity of the sediment particles on the surface of the stay vane ranged from 5.1 to 14.6 m/s, and the difference of the sediment particles’ velocity near the wall was 1 to 3 m/s. The trailing vorticity of the guide vane reached a maximum of 120 s−1. Consequently, the single-channel sediment erosion test device can unveil the sediment erosion mechanism of the guide apparatus of a reaction turbine.

Effects of vegetation restoration on runoff and its components in the mountainous Haihe River Basin

Study regionTwo typical mountainous Haihe River Basins: The Xiaojue Basin and the Yehe River Basin Study focusesThe mountainous Haihe River Basin has suffered from a water crisis duo to large-scale restoration. Quantifying the hydrological impacts of vegetation restoration is necessary for local water management. In this study, we used the Soil and Water Assessment Tool (SWAT) hydrological model, in combination with two vegetation restoration scenarios, to analyze the effects of vegetation restoration on runoff and its runoff components (surface runoff, baseflow, and total runoff) New hydrological insights for the regionOur results indicated a general decrease in surface runoff and an increase in baseflow as a result of vegetation restoration. At the seasonal timescale, total runoff and surface runoff decreases mainly concentrated in the flood season, and slightly increased in the non-flood season, and baseflow showed the opposite trend during the flood-season in the Xiaojue and Yehe River Basin. The magnitude of change in runoff components in the Yehe River Basin was higher than that in the Xiaojue Basin, and the Yehe River Basin has a larger water yield capability. This study advances our knowledge on the way in which vegetation affects runoff and offers recommendations for water resources management

Numerical Study on the Formation Mechanism of Plume Bulge in the Pearl River Estuary under the Influence of River Discharge

Previous studies have investigated the characteristics and influencing factors of plume bulge in the Pearl River Estuary (PRE) using observations and numerical simulations. However, the understanding of how river discharge affects plume bulge is not consistent, and the response mechanism of plume bulge to changes in river discharge has not been revealed in detail. In this study, a three-dimensional hydrodynamic Finite-Volume Coastal Ocean Model (FVCOM) is constructed, and five experiments were set to characterize the horizontal and vertical distribution of the plume bulge outside the PRE under different river discharge conditions during spring tide. The physical mechanisms of plume bulge generation and its response mechanisms to river discharge were discussed through standardized analysis and momentum diagnostic analysis. The results indicate that the plume bulge is sensitive to changes in river discharge. When the river discharge is relatively low (e.g., less than 11,720 m3/s observed in the dry season), the bulge cannot be formed. Conversely, when the river discharge is relatively high (e.g., exceeding 23,440 m3/s observed in flood season), the bulge is more significant. The plume bulge is formed by the anticyclonic flow resulting from the action of the Coriolis force on the strongly mixed river plume. The bulge remains stable under the combined effects of barotropic force, baroclinic gradient force, and Coriolis force. The reduction of river discharge weakens the mixing of freshwater and seawater, resulting in the reduction of both the volume and momentum of the river plume, and the balance between advective diffusion and Coriolis forces are altered, resulting in the plume, which is originally flushed out from the Lantau Channel, not being able to maintain the anticyclonic structure and instead floating out along the coast of the western side of the PRE, with the disappearance of the plume bulge. Due to the significant influence of plume bulges on the physical and biogeochemical interactions between estuaries and terrestrial environments, studying the physical mechanisms behind the formation of plume bulges is crucial.

Dynamic quantitative assessment of multiple uncertainty sources in future hydropower generation prediction of cascade reservoirs with hydrological variations

Hydropower is the dominant renewable energy source, which can significantly reduce carbon dioxide emissions while providing electric energy. It is a crucial way to achieve the dual-carbon goal of carbon peak and carbon neutrality. However, climate change inevitably threatens hydropower, either directly or indirectly. Global climate models (GCMs) and hydrological models (HMs) under different representative concentration pathways (RCPs) have been combined to investigate future hydropower generation responses to climate change. The contribution of multiple uncertainty sources to multi-scale hydropower generation uncertainties with hydrological variations remains unclear. Therefore, to address the above challenge, a three-step framework was proposed in this paper: (1) predicting future inflows to reservoirs using three HMs (HBV, SWAT and XAJ) with different structures driven by six GCMs (BNU-ESM, GFDL-ESM2G, GFDL-ESM2M, CanESM2, MIROC-ESM-CHEM and CSIRO-MK3-6-0) under three RCPs (i.e., RCP2.6, RCP4.5 and RCP8.5); (2) diagnosing future hydrological conditions using the Comprehensive Differential Split-sample Test; (3) predicting future hydropower generation of cascade reservoirs by developing a cascade hydropower generation model and dynamically quantifying the contribution of multiple uncertainty sources to multi-scale hydropower generation uncertainties with hydrological conditions based on the variance decomposition method through subsampling. The results indicate that GCMs, HMs, climate emission scenarios and their interactions significantly impacted the uncertainty of hydropower generation with hydrological variations. In the flood season, the relative contributions of GCMs and HMs were the largest, accounting for about 40 %. The interaction effects of multiple uncertainty sources gradually increased before, after and during the non-flood season, with its relative contribution accounting for about 36 %. These findings can facilitate the active response to the new challenges of strategic hydropower energy development under climate change, reducing the losses caused by climate change.

Spatial and temporal distribution of nitrogen, phosphorus, and heavy metals loads in Guanshan River Basin based on SWAT modeling

ABSTRACT This study takes Guanshan River Basin, a typical inflow river of the Danjiangkou Reservoir, as the research area, and the nonpoint source (NPS) pollution characteristics of nitrogen and phosphorus from 2013 to 2018 were evaluated by establishing a Soil and Water Assessment Tool (SWAT) model. The pollution characteristics of heavy metals were also evaluated by combining the SWAT and simple output coefficient method. The results show that the pollutant load in Guanshan River Basin contributes significantly to the Danjiangkou Reservoir. Temporally, pollutant loads were primarily concentrated in the flood season, which had a significant positive correlation with precipitation, water yield, and sediments in the abundant period. Among them, sediments were the most important driving factor, followed by water yield. Spatially, pollutant loads were mainly concentrated downstream of the basin, where cultivated land is widespread. In this regard, it is suggested that the input of chemical fertilizers, pesticides, and livestock manure in cultivated land should be controlled and soil erosion downstream of the basin should be prevented to mitigate nitrogen, phosphorus, and heavy metal pollution. This research offers a basis for the formulation and implementation of watershed management for the Danjiangkou Reservoir.

Assessment of Stormwater Harvesting Potential: The Case Study of South Korea

Stormwater harvesting (SWH) is emerging as a vital adaptive strategy for urban climate resilience. In South Korea, different types of storage facilities have been constructed under different regulations and laws. Each type of storage facility has its own original purpose of construction. Although these facilities have better outcomes, we aim to investigate the potential use of these facilities as additional water resources. In this study, we assess the stormwater harvesting (SWH) potential of different types of already-constructed storage facilities. Five different types of storage facilities and three different cases are considered in the present study. Case 1 excludes SWH volume during the flood and winter seasons, while in Case 2, only winter season SWH volume is excluded. In Case 3, the winter season and combined sewer overflows (CSOs) facilities are excluded. The Rainwater Utilization Facility is considered as a baseline for comparison in the present study. The results show that, in Case 2, the Sewage Storage Facility, Stormwater Runoff Reduction Facility, Nonpoint Pollution Reduction Facility, and Buffer Storage Facility has 53.5, 4, 2.4, and 1.2 times more stormwater average annual usage potential, respectively. The findings suggest that these facilities can be utilized as additional water resources. It should be mentioned that the primary objective for which each facility was constructed will remain unaffected. Nevertheless, forthcoming research should focus on a detailed exploration of the quality of the collected stormwater and the energy required to supply the stormwater for the end usage.

Farmers’ livelihood strategies for adapting to reduced water resources in the upstream Mekong Delta, Vietnam

The article analyzes the livelihood strategies of farmers to adapt to reduced amounts of water in the upstream Mekong Delta in Vietnam. The study was conducted in An Phu district, the upstream district of An Giang province, bordering Cambodia, the area first affected when the availability of water resource from the Mekong River changes. The study aims to learn about the impact of changes on livelihood patterns and agricultural livelihood strategies using qualitative and quantitative data collection methods including: household surveys, key informant interviews, participatory rural appraisal methods, and in-depth interviews with farmers. The results show that the decrease in water resources has led to transitions in the livelihoods of farmers. From 2011 to 2022, flood levels had changed, peak floods were lower, and duration of the seasonal floods was shorter. Farmers have gradually changed farming patterns and techniques and adopted different strategies, including from (1) rice to “safe rice” (44.73%); (2) rice to fruits (32.99%); (3) rice to vegetables (6.41%); (4) and vegetables to fruits (13.42%). The reason for these transitions are: reduced water resources availability for practical farming; higher profits are possible with alternative strategies; and, availability of new learning from neighbouring farmers. Better use of available water resources, protection of human health and the environment, and lower production costs are the pathways that farmers have been aiming to achieve effectively and safely on account of changes in their environmental conditions.

Assessing the Spatiotemporal Variations in the Hydrological Response of the Qin River Basin in Loess Plateau, China

In recent decades, the hydrological processes on the Loess Plateau have undergone significant changes due to the combined effects of climate change and human activities. This study investigates the Qin River basin, the core area of the Loess Plateau. Between 1971 and 2000, the hydrometeorology of the flood season in the Qin basin on the Loess Plateau in China changed abruptly in 1982 and 1992. This study uses distributed hydrologic modeling and statistical analysis to distinguish the spatial and temporal impacts of climate change and human activities. The fastest dynamic changes in land use occurred in grassland and construction land, accounting for 0.36% and −0.1%, respectively, from 1982 to 1991. From 1992 to 2000, it was 0.29% and 0.3%, respectively. The increase in basin area where the Normalized Difference Vegetation Index increased was 95%. However, except for significant changes in runoff from 1981 to 1992, there were no significant changes in precipitation, runoff, and temperature during other flood seasons. During the two studied variation periods, from 1982 to 1991 and from 1992 to 2000, the contribution rate of climate change to flood season runoff (CClimate) decreased from 83.26% to 74.47%, while the contribution rate of human activity disturbance to flood season runoff (Chuman) increased from 16.74% to 25.53%. In terms of spatial distribution, from 1982 to 1991, areas with a Chuman > 50% were primarily concentrated in the upper reaches of the basin, while from 1992–2000, these areas shifted to the lower reaches. This study offers valuable insights for water resource planning and soil conservation measures in the Loess Plateau and similar arid regions worldwide, aiming to ensure water resource safety and sustainability in response to climate change and human interference.

Influence of the hydrological regime of lake buyo on fish community of three floodplains in the Tai national park (southwestern Côte d’Ivoire)

Floodplains play an important role in the ecological functioning of the areas on which they depend. These plains are also of socio-economic interest to the local population, particularly in terms of fishing activities. The fish fauna of three Lake Buyo floodplains (Néma, Libériakôbro and Gah) was studied in relation to the lake's hydrological regime. The aim of this study was to evaluate the influence of the hydrological seasons of Lake Buyo on the structure of the fauna considered. Sampling of fish community was carried out monthly during an annual cycle using experimental fishing. The structure of the fish community was analyzed by determining taxonomic composition, taxon abundances (Ar) and the Shannon-Weaver diversity (H') and Pielou equitability (E) index. Temporal dynamics of the studied parameters were analyzed according to three hydrological seasons: flood season, high water season and recession season. Results showed that total specific richness of ichthyofauna of the studied plains was 38 species, and the richness observed at the different hydrological seasons varied significantly (p < 0.05). The Cyprinidae family was dominant in the abundances recorded at all seasons (48.34% ≤ Ar ≤ 85.5%). It should be noted that the studied ichthyofauna exhibited relatively low diversity and equitability with reference to diversity index (1.42 ≤ H' ≤ 1.46 and 0.28≤ E ≤ 0.29).

Determination Procedure of Ecotoxicologically Acceptable Cu Concentration in River Considering the Change of Environmental Factors

Objectives : In this study, considering the changes in the concentration of metal/metalloid and environmental factors over time of the target water system and the toxic effects of metals on various aquatic organisms, determined procedure of ecotoxicologically acceptable metal/metalloid concentration based on a biotic ligand model (BLM) was proposed in detail. As an application example, the ecotoxicologically acceptable Cu concentration for the Numedalslågen river in Norway was calculated.Methods : The Cu concentration and environmental factor time series data of the target water system were collected, and EC50[Cu]<sub>T</sub>, the total concentration of Cu in the water system showing a toxic effect of 50% on the target aquatic organisms, was calculated through BLM. In addition, the predicted no-effect concentration (PNEC) was obtained from the species sensitivity distribution using the acute-chronic ratio and adjustment factor, and the ecotoxicologically acceptable Cu concentration of the target water system was determined through the fixed monitoring benchmark (FMB).Results and Discussion : Ecotoxicologically acceptable Cu concentration of the target water system was determined as 1.15 μg/L. Dissolved organic carbon (DOC) showed the highest linear relationship with EC50[Cu]<sub>T</sub> (R<sup>2</sup> = 0.94-0.98) compared to various environmental factors, and the Cu toxicity effect on aquatic organisms tended to decrease as the DOC concentration increased. Ca showed a low linear relationship with EC50[Cu]<sub>T</sub> (R<sup>2</sup> < 0.04), which is presumed to be due to the decrease in Ca<sup>2+</sup> concentration due to the complexese formation of DOC and Ca<sup>2+</sup>, which reduced the competitive effect with Cu<sup>2+</sup>.Conclusion : The proposed procedure provides a useful method for calculating ecotoxicologically acceptable metal concentrations for the protection of aquatic organisms in water systems. In addition, it is expected that it can be used to calculate site-specific metal concentrations that can protect aquatic organisms in the target water system by reflecting the timing of sediment resuspension, which can cause rapid changes in the concentration of metals and environmental factors in the water system, and specific time points such as storm and flood seasons.

Spatial Sensitivity of River Flooding to Changes in Climate and Land Cover Through Explainable AI

AbstractExplaining the spatially variable impacts of flood‐generating mechanisms is a longstanding challenge in hydrology, with increasing and decreasing temporal flood trends often found in close regional proximity. Here, we develop a machine learning‐informed approach to unravel the drivers of seasonal flood magnitude and explain the spatial variability of their effects in a temperate climate. We employ 11 observed meteorological and land cover (LC) time series variables alongside 8 static catchment attributes to model flood magnitude in 1,268 catchments across Great Britain over four decades. We then perform a sensitivity analysis to assess how a 10% increase in precipitation, a 1°C rise in air temperature, or a 10 percentage point increase in urban or forest LC may affect flood magnitude in catchments with varying characteristics. Our simulations show that increasing precipitation and urbanization both tend to amplify flood magnitude significantly more in catchments with high baseflow contribution and low runoff ratio, which tend to have lower values of specific discharge on average. In contrast, rising air temperature (in the absence of changing precipitation) decreases flood magnitudes, with the largest effects in dry catchments with low baseflow index. Afforestation also tends to decrease floods more in catchments with low groundwater contribution, and in dry catchments in the summer. Our approach may be used to further disentangle the joint effects of multiple flood drivers in individual catchments.

Community Based Adaptation To Climate Change And Social Economic In Xe Champhone Wetland, Champhone District, Savannakhet Province

Climate change is key significant factor that impacts on multi-dimensions, which is relevant to social economic development, livelihood and environment, hence, Community Based Adaptation (CBA) to climate change is a mechanism of adapting based on the existing practices, knowledge, policy and experiences of the rice farmers to sustain their lives on changing climate, the objective of the study is to assess the social economic and find the practice management of rice farmers to adapt during flood and drought seasons. Hence, according to the research finds that, majority of the rice farmers are experienced and learnt from the previous effect and adjust themselves by using knowledge skills, experiences to build the resilience for their rice and crop planting in order to prevent and avoid the damages from climate change within the wetland. Besides that, the local communities still utilize the existing potential natural based adaptation to be flexible sustainably their agricultural activities and livelihood during rainy and dry season

Changes in Surface Runoff and Temporal Dispersion in a Restored Montane Watershed on the Qinghai–Tibetan Plateau

Surface runoff is a major component of the hydrological cycle, and it is essential for supporting the ecosystem services provided by grassland and forest ecosystems. It is of practical importance to understand the mechanisms and the dynamic processes of runoff in a river’s basin, and in this study, we focused on the restored montane Pailugou Basin in the Qilian Mountains, Gansu Province, China, since its water status is extremely important for the large arid area and local economies therein. Our purpose was to determine the annual variation in the surface runoff in the Pailugou Basin because it is important to understand the influence of climate fluctuations on surface water resources and the economy of the basin. In addition, little is known about the annual variations in precipitation and runoff in this region of the world. Daily atmospheric precipitation, air temperature and runoff data from 2000 to 2019 were analyzed by the calculation of the uneven annual distribution of surface runoff, the calculation of the complete adjustment coefficient, and the vector accumulation expressed by the concentration degree. We also used the cumulative anomaly approach to determine the interannual variation trend of runoff, while the change trend was quantified by the sliding average method. Finally, we used the Mann–Kendall mutation test method and regression analysis to establish the time-series trend for precipitation and runoff and to determine the period of abrupt runoff changes. The results indicated concentrated and positive distributions of surface runoff on an annual basis, with a small degree of dispersion, and an explicit concentration of extreme flows. The relative variation ranges exhibited a decreasing trend, and the distribution of the surface runoff gradually was uniform over the year. The runoff was highest from July to September (85% of the annual total). We also determined that annual surface runoff in the basin fluctuated over the 20-year period but showed an overall increasing trend, increasing by 3.94 × 105 m3, with an average increase rate of 0.42 × 105 m3 every ten years. From 2005 to 2014, the annual runoff and the proportion of runoff in the flood season (July to September) to the annual runoff fluctuated greatly. The correlation between the runoff and precipitation was significant (r = 0.839, p < 0.05), whereas the correlation between air temperature and surface runoff was low (r = 0.421, p < 0.05).