Upstream Area Research Articles

Analysis of Spatio-Temporal Relationship Between Ecosystem Services and Human Footprints Under Different Human Activity Gradients: A Case Study of Xiangjiang River Basin

Clarifying the relationship between human activities and the provision of ecosystem services has received significant interest in recent years because of a growing need for sustainable socio-ecological system development. Using multi-source remote sensing data, we assessed the spatial and temporal distribution of the human footprint index and five ecosystem services under four human activity gradients from 2010 to 2020 in the Xiangjiang River Basin. The five ecosystem services include water supply, soil conservation, food production, habitat quality, and carbon sequestration. The relationship between human footprint and ecosystem services was analyzed from quantitative and spatial perspectives. The results showed that over the past 10 years, water supply and habitat quality decreased by 4.59% and 16.49%, respectively. The other three services increased, and the upstream area of the basin had a higher level of ecosystem services provision. The human footprint index increased by 28.83% over the 10 years and was characterized by point and patchy clustering in the middle and lower reaches. In terms of quantitative characteristics, the relationship between human footprint and ecosystem services was primarily negative. The ecosystem services were sensitive to the human footprint index within the 0−0.4 range. In terms of spatial characteristics, the relationship was dominated by trade-offs. The risky “high–low” trade-offs were mainly distributed in the middle and lower reaches. As the gradients of human activity increased, the maximum fluctuation in ESs was 43%, and the maximum fluctuation in human footprint was 28%, making their relationship more complex. Our results identified response thresholds of ecosystem services to human activities, providing a guide for ecological management and sustainable development of basins.

Numerical study on characteristics of spiked electrode electrostatic precipitator

The characteristic of the spiked electrode electrostatic precipitator was numerically studied. The spiked electrode had significant effects on the distribution of electric field and charge density. The electric field and charge density were quite high in the area around the spiked electrode tips while decreased rapidly in other area far from the tips. Complicated electrohydrodynamic flow was observed and strong vortices were formed in the upstream and side areas of the spiked electrode. The gas velocity at the tip of the spiked electrode was as high as 28.1 m/s at the working potential of 45 kV. The working potential was more effective for the removal of large particle. The removal efficiency increased 42.4% for 10 µm particle and 15.2% for 0.25 µm particle as working potential increased from 22.5 kV to 45 kV. Low gas velocity was beneficial to the removal of all size particles. The removal efficiency increased by 10% to 15% for all size particles when the gas velocity decreased from 1.0 m/s to 0.6 m/s.

Quantification of streamflow response to climate change and human activities within upstream mountainous areas of the Daqing River Basin, Northern China

The Daqinghe River Basin is located in the North China Plain. In recent years, however, climate warming, drying, and intense human activities have led to declining ecosystem functions and shrinking wetlands in the region. Understanding streamflow changes in the upstream mountainous areas of the Daqinghe River Basin in this changing environment and identifying the driving factors can provide a scientific basis for water resources management and optimization in these areas. This study focuses on the Beihedian River watershed, the Xidayang Reservoir watershed, and the Wangkuai Reservoir watershed in the upstream mountainous areas of the Daqinghe River. It is based on hydro-meteorological data collected between 1963 and 2019. The methods used in the study include the linear tendency estimation method, the non-parametric Mann-Kendall trend test, the elasticity coefficient method, and hydrological simulation methods. The results of this study suggest that the streamflow, precipitation, and potential evapotranspiration (PET) in the three watersheds showed an overall decreasing trend. The minimum precipitation decrease rate ranged from −1.09 to −0.55 mm/a, and the minimum streamflow decreasing rate at the Beihedian Hydrological Station was −1.32 mm/a, with a minimum range of 0–176.03 mm. Change-point analysis revealed that the streamflow in the Beihedian River and Xidayang Reservoir watersheds experienced a significant change point around 1999, with a significant level of α=0.05. As for the Wangkuai Reservoir watershed, a significant change point was observed around 1980, which is likely attributable to land system reforms and protective forest projects. The attribution analysis which combined both climate change and human activities using the elasticity coefficient method and hydrological simulation methods indicated that climate change contributed an average of 32.93%, 34.50%, and 35.12% to the reduction in streamflow in the three watersheds, respectively. Human activities accounted for an average contribution of 67.07%, 65.50%, and 64.88%, respectively. Water conservancy projects, afforestation, and other human activities were identified as the primary factors contributing to streamflow decreases.

Combining APCS-MLR model to evaluate the distribution and sources of rare earth elements in a large catchment

Rare earth elements (REEs), functioning as indicators for environmental tracking, revealing the impacts of human activities on changes in aquatic ecosystems. However, systematic research on the geochemical characteristics of REEs in large river basins remains relatively scarce. Therefore, this research investigates the geochemical properties of REEs within the Yangtze River basin, analyzing the quantity and spatial distribution of REEs in surface aquatic environments across the upstream, midstream, and downstream segments of the Yangtze River, and quantitatively assessing their sources. Results indicate that the REE concentration in the upstream and downstream areas are significantly higher than in the midstream, with average concentrations of 0.69 μg/L, 0.56 μg/L, and 0.39 μg/L, respectively. REEs in the Yangtze River basin are enriched in light rare earth elements (LREEs), exhibiting a slight negative cerium (Ce) anomaly and a pronounced positive europium (Eu) anomaly. The Ce anomaly correlates with pH levels, and the Eu anomaly is largely attributed to the selective chemical decomposition and solubilization of feldspar minerals. Correlation analysis indicates that REE sources are related to manganese (Mn). Utilizing the Absolute Principal Component Scores-Multiple Linear Regression (APCS-MLR) model, the principal sources of REEs are further determined to be mineral sources (36.80%), industrial sources (45.61%), and mixed sources (17.59%). Further analysis suggests that mining and dissolution of Mn-bearing feldspar minerals, along with the discharge of industrial wastewater, considerably influence REE concentrations in the basin. This study reveals the anthropogenic and natural factors influencing the distribution of REEs in the Yangtze River basin, laying a foundational framework for investigating how human activities affect the dispersion of REEs in aquatic environments.

Spatial benefit difference of fertilizer reduction and substitution policy based on grid scale: A case study of the Heihe River Basin

Agriculture green development faces the challenge of balancing the application of both organic and chemical fertilizers. Formulating effective policies to harmonize these applications is essential for ensuring food security and environmental sustainability. However, there is a lack of studies investigating the economic and environmental benefits of policy implementation at the grid scale, and insufficient research has been conducted on the subsequent impacts these policies have on diverse crops. Therefore, this paper develops the SIMPLE-G-Heihe model to simulate the impacts of green agricultural policies on multiple crops planting in arid regions. This model addresses limitations found in the SIMPLE-G model, which supported a single crop and lacked organic fertilizer substitution simulation. The results show that: (1) Merely increasing subsidies for organic fertilizers is insufficient to significantly enhance yields, and improving the efficiency of fertilizer utilization should also be emphasized. (2) Combining improvements in fertilizer technology with subsidies for organic fertilizers can concurrently support economic advancement and environmental mitigation. Research indicates that integrating a 3% organic fertilizer subsidy with an 8% improvement in chemical fertilizer technology increases vegetable output value by 0.27% and reduces N2O emissions by 1.09%. (3) The upstream areas of the Heihe River Basin show a significant reduction in fertilizer use. Fertilizer input is mainly reduced for vegetables in the upstream areas, while for wheat and maize, the reduction is primarily in the midstream and upstream areas. The findings discuss the spatial heterogeneity and flexibility of policy impacts, providing valuable insights for the implementation of green agriculture strategies in China.

Nonlinear Tide‐River‐Surge Interactions and Their Impacts on Compound Flooding During Typhoon Hato in the Pearl River Delta

AbstractIn coastal areas, multiple hydrodynamic processes co‐occur, including the astronomical tide, river discharge, and storm surge. Their propagation and interaction within coastal tidal river result in strong nonlinear behavior in inland areas. This study employed a hydrodynamic model and continuous wavelet transform analysis to investigate the complex tide‐river‐surge interactions and their impacts on compound flooding in the West River of the Pearl River Delta during an extreme typhoon event. Validated model outputs provided insights into the spatial and temporal variations of river discharge, water levels, and currents. Wavelet analysis revealed river discharge modulates tidal properties, causing nonstationary tides and asymmetries, with high flows suppressing tidal ranges but facilitating energy transfers to overtides. During Typhoon Hato, storm surges dominated high‐frequency water level fluctuations that rapidly propagated upstream. Crucially, strong high‐frequency tide‐river‐surge coupling induced significant water level amplifications, with interaction intensities increasing landward. In upstream areas where riverine and coastal drivers converged, flood risks exceeded typical estimates due to this vigorous multi‐driver compounding. Findings highlighted how existing flood mitigation approaches over simplistically superposing individual sources may severely underestimate flood levels by neglecting such nonlinear interactions. A comprehensive accounting of the cumulative, multiplicative effects of tides, discharge, storm surge, and sea level rise is imperative. This quantitative unraveling of key physical drivers offers transferable insights applicable to compound flood risk evaluations and policy guidance for enhancing resilience in other estuary and delta regions. Future work should focus on holistically modeling multivariate extremes and their interactions.

Permafrost impacts on chemical weathering and CO2 budgets in the Tibetan Plateau: Micro-watershed perspective on a headwater catchment

Understanding the balance between alkalinity generation from carbonate and silicate weathering, and the effect of sulfide weathering, is crucial for comprehending the impact of these processes on atmospheric CO2 levels. However, the sequestration potential and the net balance of CO2 between the release from sulfide weathering and the consumption by silicate weathering in permafrost environments remain contentious. This study examines the Shaliu River, a typical permafrost-dominated headwater catchment in the Northeast Tibetan Plateau, from a micro-watershed perspective to elucidate the effects of permafrost on chemical weathering and CO2 budgets during ablation period. Silicate weathering in the Shaliu River contributes 25–32 % to solute load, while carbonate weathering contributes 39–45 %. Sulfuric acid (H2SO4) plays a key role in carbonate weathering, accounting for 74 % of it and 37 % of the river’s solute load, especially in the permafrost-covered upstream areas. In contrast, bicarbonate (HCO3–) impacts are more evident in the lower reaches without permafrost. By integrating silicate and carbonate weathering with H2SO4-driven reactions, CO2 budget analysis indicates that the Shaliu River basin acts as a carbon source. The MEANDIR inversion model consistently depicts the watershed as a carbon source, influenced by permafrost and lithology. This implies that sulfide oxidation to produce sulfuric acid (H2SO4) drives carbonate weathering may significantly counterbalance the carbon sequestration associated with silicate weathering over geological timescales. The study provides a comprehensive understanding of the carbon budget dynamics within the permafrost-dominated watersheds of the Tibetan Plateau, enhancing the comprehension of carbon cycle processes in high-altitude ecosystems.

Validation of physicochemical water quality results through cross-checking with biological indices

ABSTRACT Biological assessment of rivers is critical for evaluating ecosystem health, detecting ecological changes, validating physicochemical monitoring data, assessing the effectiveness of water treatment systems, conserving biodiversity, and guiding water resource management. In this study, the surface water quality of the Karkheh River basin was evaluated using the National Sanitation Foundation Water Quality Index (NSFWQI) and the Iranian Surface Water Quality Index (IRWQIsc) for qualitative analysis. For biological monitoring, the Biological Monitoring Working Party (BMWP) index, along with the Average Score per Taxon (ASPT) and the Hilsenhoff Biotic Index (HFBI), was employed to provide a comprehensive assessment. Water quality was analyzed across 18 sampling stations, revealing significant spatial variation. Upstream areas exhibited relatively good conditions, with NSFWQI and IRWQIsc values of 59 and 68, respectively. In contrast, downstream locations near urban and agricultural areas demonstrated poor water quality, with values of 27 and 33, respectively. Overall, approximately 70% of the river's length has been severely impacted, highlighting the need for targeted planning and management to mitigate pollution. The biological indices corroborated the physicochemical results, revealing severe ecological stress in polluted regions. The close alignment between the NSFWQI and biological indicators emphasizes the importance of a multifaceted approach in assessing aquatic health. Key factors contributing to the river's degradation include excessive water extraction, untreated wastewater discharge, and diminished self-purification capacity, particularly in downstream areas.

Application of time series and multivariate statistical models for water quality assessment and pollution source apportionment in an Urban River, New Jersey, USA

Water quality monitoring reveals changing trends in the environmental condition of aquatic systems, elucidates the prevailing factors impacting a water body, and facilitates science-backed policymaking. A 2020 hiatus in water quality data tracking in the Lower Passaic River (LPR), New Jersey, has created a 5-year information gap. To gain insight into the LPR water quality status during this lag period and ahead, water quality indices computed with 16-year historical data available for 12 physical, chemical, nutrient, and microbiological parameters were used to predict water quality between 2020 and 2025 using seasonal autoregressive moving average (ARIMA) models. Average water quality ranged from good to very poor (34 ≤ µWQI ≤ 95), with noticeable spatial and seasonal variations detected in the historical and predicted data. Pollution source tracking with the positive matrix factorization (PMF) model yielded significant R2 values (0.9 < R2 ≤ 1) for the input parameters and revealed four major LPR pollution factors, i.e., combined sewer systems, surface runoff, tide-influenced sediment resuspension, and industrial wastewater with pollution contribution rates of 23–30.2% in the upstream and downstream study areas. Significant correlation of toxic metals, nutrients, and sewage indicators suggest similarities in their sources.Graphical

Understanding future water-carbon-land coupled systems in the era of COP 27: The case of the Hanjiang river Basin, China

The 27th Conference of the Parties (COP 27) emphasized addressing this century's interconnected challenges of food, water, and energy. This study proposes a coupled ecosystem service and multi-scenario land-use change simulation model designed to investigate the future dynamics of water-carbon-land coupled systems in the Hanjiang River Basin (HJRB), the primary objective is to provide valuable insights that can inform strategic spatial management decisions, aligning with the ambitious objectives outlined in COP 27. Specifically, this study utilized the PLUS model, InVEST model, and redundancy analysis to comprehensively analyze the interplay between ecosystem services and land-use changes, with a specific focus on water, carbon, and land dynamics. The results showed that regardless of the simulated scenarios, there was a consistent pattern observed in the changes of land use types within the HJRB, with a decrease in farmland and an increase in forest. However, the water area showed an increasing trend in all scenarios, especially in the ecological land protection (ELP) and sustainable development scenarios. Furthermore, the ELP scenario effectively suppressed the expansion of building land and the erosion of ecological land. Ecosystem services under different scenarios showed similar spatial distribution patterns but presented varying degrees of change related to the impact of future land use and urban development on ecosystem services. The water yield (WY), carbon storage, and soil conservation in the upstream areas increased to varying degrees, while those in the downstream areas decreased. In conclusion, precipitation, land use/land cover change, DEM (Digital Elevation Model), and NDVI (Normalized Difference Vegetation Index) were the main driving factors affecting ecosystem services, with precipitation having the most significant and enduring impact on WY. This study supports the adoption of targeted spatial management measures to promote sustainable development and enhance human well-being.

Assessment of soil erosion risk and vulnerability in the transboundary Sio-Malaba-Malakisi watershed in Kenya and Uganda

Persistent soil erosion poses a significant threat to water quality, ecosystem viability and soil health in many regions of the world. Addressing this challenge requires a comprehensive understanding of local soil erosion rates, including the identification of vulnerable areas, to facilitate effective and integrated environmental management. In East Africa, however, many affected regions are data poor and lack measured hydrological data from which soil erosion estimates can be derived. This study used the physically based Revised Universal Soil Loss Equation (RUSLE) model to estimate the annual rate of soil erosion in the transboundary Sio-Malaba-Malakisi catchment, straddling Kenya and Uganda. Soil erosion events were quantified by integrating input factors derived from physical datasets using a Geographical Information System (GIS). The Analytical Hierarchy Process (AHP) technique was then used to assess the importance of selected physical factors influencing the soil erosion process in order to identify regions of increasing environmental vulnerability. The results obtained indicate a wide range of soil erosion rates across the region, with an estimated mean annual rate of 250 t ha−1 yr−1 for the whole catchment. Upstream areas characterized by intensive agricultural activity had erosion rates of up to 2000 t ha−1 yr−1, while downstream areas recorded erosion rates below 600 t ha−1 yr−1. Areas with intensive agriculture, unprotected soils, and a soil loss tolerance value above 12 t ha−1 yr−1 were found to be most vulnerable. Rainfall and vegetation cover were identified as key factors influencing erosion susceptibility. Regions with soil erosion rates above 50 t ha−1 yr−1 were identified as high priority regions for targeted soil and water conservation measures. The identification of vulnerability zones, including the classification of their severity, provides an opportunity to prioritize sustainable environmental management interventions; a process that can be replicated for such affected regions elsewhere.

Multi-objective calibration and evaluation of the ORCHIDEE land surface model over France at high resolution

Abstract. Here we present a strategy to obtain a reliable hydrological simulation over France with the ORCHIDEE land surface model. The model is forced by the SAFRAN atmospheric reanalysis at 8 km resolution and hourly time steps from 1959 to 2020 and by a high-resolution DEM (around 1.3 km in France). Each SAFRAN grid cell is decomposed into a graph of hydrological transfer units (HTUs) based on the higher-resolution DEM to better describe lateral water movements. In particular, it is possible to accurately locate 3507 stations among the 4081 stations collected from the national hydrometric network HydroPortail (filtered to drain an upstream area larger than 64 km2). A simple trial-and-error calibration is conducted by modifying selected parameters of ORCHIDEE to reduce the biases of the simulated water budget compared to the evapotranspiration products (the GLEAM and FLUXCOM datasets) and the HydroPortail observations of river discharge. The simulation that is eventually preferred is extensively assessed with classic goodness-of-fit indicators complemented by trend analysis at 1785 stations (filtered to have records for at least 8 entire years) across France. For example, the median bias of evapotranspiration is −0.5 % against GLEAM (−4.3 % against FLUXCOM), the median bias of river discharge is 6.3 %, and the median Kling–Gupta efficiency (KGE) of square-rooted river discharge is 0.59. These indicators, however, exhibit a large spatial variability, with poor performance in the Alps and the Seine sedimentary basin. The spatial contrasts and temporal trends of river discharge across France are well represented with an accuracy of 76.4 % for the trend sign and an accuracy of 62.7 % for the trend significance. Although it does not yet integrate human impacts on river basins, the selected parameterization of ORCHIDEE offers a reliable historical overview of water resources and a robust configuration for climate change impact analysis at the nationwide scale of France.

Mechanism and spatial spillover effect of digital economy on common prosperity in the Yellow River Basin of China

The digital economy has emerged as a new trend in economic development and has profoundly influenced the process of achieving common prosperity. However, current research on the correlation between the digital economy and common prosperity from the perspective of a river basin still needs to be strengthened. Based on this, the present study first theoretically elaborates the conceptual meanings of “digital economy” and “common prosperity”, as well as the mechanism by which the digital economy empowers common prosperity. Subsequently, a scientifically-constructed performance evaluation index system for the digital economy and common prosperity is established. Considering the Yellow River Basin as an empirical case study area, this study investigates the mechanism and spatial spillover effects of the digital economy in empowering common prosperity from 2005 to 2020. The research findings reveal that: (1) The Yellow River Basin exhibits a basin characteristic with downstream > midstream > upstream areas regarding the level of common prosperity and digital economy. It indicates that a distinct spatial correlation exists between the two factors. However, the ongoing decrease in both high-level and very high-level areas reflects the lengthy and challenging journey of enhancing the quality and efficiency of the digital economy in empowering common prosperity. (2) The digital economy not only directly impacts common prosperity, but also fosters its development through spatial spillover effects. Among the control factors, informatization and housing levels have a major stimulating effect. (3) There exists a clear regional heterogeneity in how the digital economy affects common prosperity in the Yellow River Basin. Specifically, common prosperity of downstream cities is significantly impacted by the digital economy. The spatial spillover effects of the digital economy on common prosperity exhibit a pronounced “neighborhood as a moat” characteristic. (4) The digital economy facilitates the achievement of shared prosperity through the implementation of mechanisms centered on sharing, affluence, and sustainability. These research findings illuminate the empowering mechanisms and spatial spillover pathways of the digital economy in promoting shared prosperity, aligning with national strategies for ecological conservation and high-quality development in the Yellow River Basin.

Patterns distribution, concentrations and sources of radioactive elements from black sand in the Red Sea coast, Egypt

In Egypt, the distribution of black sand in various coastal regions has been readily apparent by thorough research. Unfortunately, these investigations did not measure radioactivity in black sand, particularly in the vicinity of the Red Sea. Gamma-ray spectroscopy was used to detect the naturally occurring radioactivity from 238U, 232Th, 40K, and 226Ra in black sand samples from eight locations along the Red Sea coast: Ras Elbehar, Gemsa, Hurghada Elahiaa, Hurghada Titanic, Safaga, Qusier Elsharm Alqbly, Gabal Alrosass, and Marsa Alam. The resultant data were interpolated to represent the spatial distribution. Additionally, the potential rocks sources of radionuclides were geologically mapped to elucidate the relationship between rock components and radioactivity. The results showed that 226Ra, 232Th and238U were higher at samples collected from Ras Elbehar, Hurghada Elahiaa and Hurghada Titanic compared to the other sites. On the other hand, 40K showed the lowest mean value (75.3 ± 3.8 Bq/kg) in Hurghada Titanic samples, while it peaked (563 ± 28 Bq/kg) in Qusier Elsharm Alqbly samples. The interpolated results show notable differences in radioactive amounts between the north and south, which are indicative of several environmental conditions and human activities. Alkaline syenite, syenogranite, older granites (tonalite and granodiorite), and minor acidic volcanic/metavolcanic rocks make up the upstream area of the basin area draining into, for example, the Ras Elbehar locality (highest activity concentrations for 238U (1596 ± 80 Bq/kg) and 226Ra (886 ± 44 Bq/kg)), while alkali-feldspar granite, schist, and shale rocks make up the mid-stream area. The findings provide a basis for scientific forecasting on the impact of synthetic or naturally occurring radioactive isotopes introduced into aquatic environments.

Conceptual framework to incorporate drainage solutions in the urban open space system

Cities are increasingly dealing with challenges regarding the negative impact of rapid and mismanaged urbanization. Therefore, city planning must cope with the natural environment limitations, seeking a balance between the human activities and the well-functioning of the hydrologic cycle. This work aims to present a conceptual framework able to properly integrate the stormwater dynamics into the open spaces system in a functional way, establishing a Hydrological Interest Area, HIA, to structure urban expansion integrated into and respecting watershed natural processes. The initial step is to define a HIA, primarily consisting of open spaces that can be used for supporting urban drainage functions and to order land use in the urban expansion process. This delimitation offers the background for interpreting the watershed in three functional arches, especially covering the upstream, mid-reach and downstream areas of the basin, guiding the design of a set of flood mitigation interventions focusing on the use of Blue-Green Infrastructure. To illustrate and validate the proposed methodological framework, the design is evaluated by a flood modeling tool, using a hydrological-hydrodynamic cell-model. A case study was driven in the Bambu Watershed, a rapidly developing area in the municipality of Maricá, Rio de Janeiro, Brazil. The proposed intervention includes an urban expansion scenario for a low impact development on flood behavior alongside with four parks: an upstream park with reservoirs, two multifunctional floodable urban parks, and a park dedicated to lagoon restoration. This plan complements riverbed modifications designed to enhance water discharge. The simulation showed significant reduction of water depths with a consequent decrease in exposure of buildings and roads, especially in the most critical region of the watershed. This framework highlights the importance of a multifunctional approach in land use and serves as a robust foundation for controlling urban expansion and proposing projects.

Heavy Metal Identification in Water Resources and the Surrounding Environment of the Cirasea Riparian Zone, Indonesia

The Cirasea River can provide water for both the Bandung basin and agricultural irrigation. Intensive agriculture, industry, and land use changes could have an impact on water quality. The purpose of this study is to look at the origins of heavy metals in riparian water resources. Heavy metal analysis was performed on 13 groundwater and river water samples. Heavy metals in water sources were compared with sediment and soil. The samples were analyzed for heavy metals using an AAS instrument. The research method employs statistical, geographical, and heavy metal pollution index (HPI). The HPI for river water was 131, whereas groundwater was 93. River water with an HPI value of more than 100 is highly polluted, indicating that it is unsafe for human consumption and has negative health consequences. Data verification with heavy metals in sediments reveals the presence of heavy metals coming from geogenic circumstances in various locations in the upstream area. Heavy metals in downstream areas result from geological factors and anthropogenic activities in the surrounding area. The long-term effects of heavy metal pollution along the riparian zone will become apparent. More research is needed on communities that depend on groundwater supplies along the Cirasea watershed.

Measuring hydrologic regime alterations and hydrodynamic characteristics in the Xijiang River Basin by the IHA-RVA method

Abstract An objective assessment of hydrological alterations is crucial for comprehensive water resource management, environmental protection, river ecosystem restoration, and integrated watershed water resource management. To quantitatively assess the ecological hydrologic regime alterations in the Xijiang River Basin in southern China considering the impacts from Longtan Reservoir, daily runoff data from two hydrological stations, Dahuangjiangkou and Wuzhou, are selected from 1973 to 2020. The changes in the flow are analyzed, and the indicators of hydrological alternation/range of variability approach (IHA-RVA) are employed to assess the hydrological regime alternations in the studied basin. The main findings are as follows: (1) Both stations show a decreasing trend in annual runoff, with the moving T-test detecting a change point in the runoff series in 2002. (2) The two stations’ overall hydrologic alteration degrees are 57% and 60%, with a more remarkable variation in the upstream area. Hydrological station changes tend to wane as the distance from the reservoir increases, which indicates that with the increased reservoir-station distance, the impact of the reservoir on the hydrologic process diminishes.

Morphological properties of two-dimensional and three-dimensional bedforms in open channel flow: A flume experiments study

Bedforms are formed by sediment particles under the action of flow, which in turn affect flow and sediment movement. However, the fundamental mechanisms behind the formation and development of bedforms under varying flow conditions, the interconnection between sediment particle movement and bed morphology development, as well as the influence of bedforms on flow and sediment transport, are still not well understood. In the current study, the moveable bed load transport flume experiments under different flow conditions were done, and the development processes of two-dimensional and three-dimensional dunes formed under different flow intensities were simulated. The detailed structure of the bedforms was measured by laser scanning technology, the characteristics of the bedforms were analyzed in detail, and the relations between the formation of the bedforms and the movement of sediment particles are discussed. The results found that the correlation coefficients of the longitudinal profile curve can serve as a quick reference for distinguishing two-dimensional and three-dimensional dunes. When the crestline ratio is used as the criterion for two-dimensional and three-dimensional dunes, the relative amplitude of the dune crestline and the included angle with the flow direction should also be comprehensively considered. The lee side angles of dunes calculated using the triangle generalization method and local section tangent method are compared and show that the values obtained by the former method are only about half of that of the latter. It is also found that the lee side angles of dunes are related to the dune height. The superimposed dunes generally exist in the downstream area of the stoss side of the dunes. The local bed slopes on the stoss side of the dunes show reverse slopes. The superimposed dunes improve the local bed height and further increase the reverse slope degree of the stoss side. A streamwise ridge is an important form located in the upstream area of the dunes stoss side, and they are symmetrically distributed on both sides. Multiple streamwise ridges divide the stoss side of the dunes into relatively independent movement areas, restricting the movement of sediment particles to specific regions. According to the distribution characteristics of bed morphologies, the effects of dunes on sediment particle movement and flow energy consumption are analyzed.

Assessment of Siltation Impact and Mitigation Strategies for Sustaining Storage Capacity in Lwanyo Dam, Tanzania

The ongoing generation, transportation, and deposition of silt in the Lwanyo Dam has significantly reduced the storage capacity of the Lwanyo Reservoir, originally constructed to support irrigation and the surrounding ecosystem. The objective of this paper was to assess the extent of siltation in Lwanyo Dam, evaluate its impact on the dam's storage capacity, and propose measures to mitigate silt accumulation. The upstream catchment area, approximately 39.6 km², includes around 128,991 m² allocated for rain-fed crop cultivation and 5.89 km² for pastoral activities. Frequent overtopping of the reservoir has been observed, largely due to siltation reducing its live storage capacity. In the reservoir trial pits were excavated and assessed, and they indicate that average silt layers range in thickness from 0.54 m to 0.98 m per rainy season. The deposited material consists of a silt layer from 0 to 540 mm, followed by an intermediate clay layer from 540 mm to 3100 mm. The impounded silt depth was measured at 1270 mm, with an estimated siltation volume of 58,349.4644 m³. The reservoir's original storage capacity of 210,153 m³ has been reduced by 27.765% due to siltation. The reservoir’s structural design inadequately addresses silt management, lacking both silt flushing tunnels and upstream silt check dams. The analysis indicates that storage capacity decreases by 3.085% annually, and if this linear trend continues without any intervention measures, the dam will lose all storage capacity within 24 years. The study recommends urgent measures to mitigate silt accumulation.

An Analysis Management by Mike 21 Modelling at Rolak 70 Retention Pool in Jombang Regency, East Java Province, Indonesia

Some areas in Indonesia have high level of sedimentation problems that able to cause flooding, and one apparent solution is to build a retention pool. Sedimentation is deposition of material into the reservoir or dam due to environmental damage or erosion occurs in the river basin area. Sedimentation becomes the main factor in constructing the Rolak 70 Retention Pool, as an important component in controlling floods on the Konto River when the water discharge exceeds the maximum limit. From geography perspective, the modelling location is in waters located between 112° 11′ 22.85″ South Latitude and 7° 38′ 42.23″ East Longitude. The model area has northern boundary at the tip of Rolak 70 pool, while western boundary at the outlet of Rolak 70 pool. The lowest water depth value is located in upstream area of Konto River at coordinates of 112°11’27.81″ South Latitude and 7°38’49.27″ East longitude. Weight of soil sample taken from the research site was ± 1000 grams at each point, and the result of sediment sample test performed at the Soil Mechanics Laboratory of Civil Engineering Department, Sultan Agung University, Semarang showed that the research area is dominated by sand, followed by mud and gravel. There were several tests conducted include grain size analysis, hydrometer analysis, and specific gravity analysis to determine the D50 of the sediment. In the study area, several sampling points were taken, started from upstream area of the river in front of Rolak 70 building to the Rolak 70 Retention Pool. For this purpose, a MIKE 21 software modelling was used to determine distribution and lines of sedimentation in the study area. As visible from changes found in bed level morphology that occurred in Rolak 70 Retention Pool by cross section extraction, it can be seen that the largest change occurred in analysis for line 1 and the smallest bed level changes occurred in the analysis for line 6. Then, the result revealed that sedimentation tends to occur at large locations in upstream area of Rolak 70 Retention Pool, while the smallest sedimentation potential will happen at the downstream area of Rolak 70 Retention Pool. These results can be caused by changes of speed from the river flow which tends to decrease towards the end of Rolak 70 Retention Pool. So, the river flow has no more energy to carry heavy amount of sediments originating from the upstream area of the Konto River. By the existence of this retention pool, the need for rice field irrigation will not be disturbed by sediment deposits. In addition, the Rolak 70 Retention Pool can be used as temporary storage for material from Mount Kelud eruption where these materials can be utilized as building material or other useful purposes.