Han River Basin Research Articles

Reservoir-based flood forecasting and warning: deep learning versus machine learning

In response to increasing flood risks driven by the climate crisis, urban areas require advanced forecasting and informed decision-making to support sustainable development. This study seeks to improve the reliability of reservoir-based flood forecasting and ensure adequate lead time for effective response measures. The main objectives are to predict hourly downstream flood discharge at a reference point, compare discharge predictions from a single reservoir with a four-hour lead time against those from three reservoirs with a seven-hour lead time, and evaluate the accuracy of data-driven approaches. The study takes place in the Han River Basin, located in Seoul, South Korea. Approaches include two non-deep learning (NDL) (random forest (RF), support vector regression (SVR)) and two deep learning (DL) (long short-term memory (LSTM), gated recurrent unit (GRU)). Scenario 1 incorporates data from three reservoirs, while Scenario 2 focuses solely on Paldang reservoir. Results show that RF performed 4.03% (in R2) better than SVR, while GRU performed 4.69% (in R2) better than LSTM in Scenario 1. In Scenario 2, none of the models showed any outstanding performance. Based on these findings, we propose a two-step reservoir-based approach: Initial predictions should utilize models for three upstream reservoirs with long lead time, while closer to the event, the model should focus on a single reservoir with more accurate prediction. This work stands as a significant contribution, making accurate and well-timed predictions for the local administrations to issue flood warnings and execute evacuations to mitigate flood damage and casualties in urban areas.

Research on the Coupling and Coordination of Land Ecological Security and High-Quality Agricultural Development in the Han River Basin

This study aims to investigate the coupling and harmonization between land ecological security (LES) and high-quality agricultural development (HAD) in the Han River Basin (HRB), China, with the objective of promoting harmonious coexistence between agriculture and ecosystems. Using 17 cities in the HRB as the research objects, an evaluation index system of two systems, LES and HAD, was constructed, analyzed, and evaluated via projective tracer modeling for multiple intelligent genetic algorithms (MIGA-PTM). The degree of coupling coordination (DCC) was used to quantitatively evaluate the coupling coordination development status of the two systems, the obstacle model (OM) was used to identify the main influencing factors, and the gray predictive model first-order univariate model (GM (1, 1)) was used to predict the DCC of the LES and HAD from 2025 to 2040. The results show the following: (1) the LES and HAD levels of the 17 cities in the HRB tended to increase during the study period, and there was a large gap between cities; (2) the spatial distributions of the DCCs of the LES and HAD in the HRB were uneven, with high values in the southern and low values in the central and northern parts, and the overall degree of coupling tended to fluctuate. The overall DCC showed a fluctuating upward trend; (3) the degree of obstacles, per capita water resources, greening coverage, and rate of return on financial expenditure are the main influencing factors; and (4) the prediction results of GM (1, 1) indicate that the LES and HAD of the HRB will be close to reaching the intermediate stage of coupling in 2035. This research offers critical insights into sustainable development practices that facilitate the alignment of agricultural growth with ecological preservation.

중국 요동반도 남부 선사시대 적석분의 고고학적 검토

Stone mound tombs, in which the deceased was placed upon the ground and the burial covered by stones, have a restricted spatial distribution and are observed mainly in the southern Liaodong Peninsula of China, the Amnok (Yalu) River basin, and the Han River basin. In this study, analysis was undertaken on the prehistoric stone mound tombs of the southern Liaodong Peninsula of China in order to lay down the foundations for future re-search on the relationship between the stone mound tombs of the different regions. The stone mound tomb was built from the end of the Neolithic Age until the introduc-tion of iron culture exclusively within the southern Liaodong Peninsula region; therefore, it can be regarded as a very conservative and exclusive tomb tradition. Stone mound tombs can be divided according to structure type into linear attached multiple tombs and clusters of single tombs featuring multiple burials. An increase in the latter can be observed over time. A change in burial method from single individual to multiple individual burials in tombs occurred, and cremation took place at multiple individual tombs. Linear attached tombs corresponded with single individual burials, and clustered tombs corresponded with multiple individual burials. Cremation also increased over time. The stone mound tombs of the southern Liaodong Peninsula were popularly used during the Bronze Age but their use came to an end around the period of the Warring States and the Qin-Han transition in the Chinese mainland. The stone mound tombs of Gangouzi, Changbai, in the upper-middle reaches of the Amnok River and the stone mound tombs of Seokchon-dongg, Seoul, are linear attached multiple tombs, the stone mound tombs in Jeongseon, Gwangju, and Yongin are clusters of single tombs featuring multiple burials. Therefore it can be said that there are similarities, in terms of structure and buri-al method, between these tombs of the Amnok and Han River regions and those of the southern Liaodong Peninsula, although a direct casual relationship cannot be posited. This relationship must be further explored within Korean archaeology, as the appearance and termination of the stone mound tomb tradition in the southern Liaodong Peninsula is re-spectively linked to the Neolithic Age to Bronze Age transition and the Bronze Age to Iron Age transition.

Articulating environmental sustainability dynamics with space-time cube

Conceptually, environmental sustainability involves maintaining crucial environmental functions while considering both present and future development. However, existing methods for expressing environmental sustainability are mainly derived from a steady state with minimal spatial explicitness. Furthermore, the environmental impact of certain events may exhibit a lag, particularly in basins. Here, we propose a framework that employs a space-time cube to articulate environmental sustainability. This cube can visualize the environment's evolution over time, identify hot and cold spots in space, and concurrently determine underlying influencing factors via spatial regression analysis. Unlike traditional methods, the space-time cube incorporates not only spatial dimensions but also temporal dimensions. We applied this framework to China's upper Han River basin, using the Remote Sensing Ecological Index (RSEI) as an indicator of environmental sustainability. It enabled us to chart the basin's ecological trajectory with spatial and temporal explicitness from 1990 to 2020. Our findings reveal that climate change (represented by temperature and precipitation changes) and human activities (represented by nighttime light) were the main factors driving changes in environmental sustainability from 2000 to 2020 in the basin. Therefore, our proposed spatial-temporal integration framework proves to be an efficient tool in articulating environmental sustainability.

Quantitative evaluation of the evolution of the ecohydrological regime and its drivers in the Han River Basin

ABSTRACT The hydrological regime of the Han River Basin has changed significantly under the double pressure of climate change and human activities, and the ecosystem's health is facing severe challenges. In this study, the ecohydrological regime of the basin was comprehensively assessed through various statistical methods and ecohydrological indicators. The results showed that the runoff volume of the Han River Basin decreased significantly, with an abrupt change in 1990, and the overall hydrological variability of the basin reached 42%. The ecological surplus decreased, the ecological deficit increased, and the ecological flow was strained for a long time. The optimal ecological flow thresholds for annual, spring, summer, autumn, and winter were 89, 97, 85, 83, and 98%, respectively. Quantitative separation of the effects of climate change and human activities on runoff reduction based on Budyko's hypothesis revealed that human activities were the main factor with a contribution of 59.73%, while precipitation and potential evapotranspiration contributed 31.08 and 9.19%, respectively. The study results can provide a scientific basis for water resource management and ecosystem restoration in the Han River Basin.

Risk-benefit comparative analysis of different control methods for reservoirs under the water to electricity mode

Abstract For some small hydropower stations that are not under the control of power dispatching department, there are many ways to implement the reservoir operation scheme formulated under the premise of determining power by water. This paper respectively selects the output, flow and water level process as the control conditions, explores the risks and benefits of reservoir operation with different control variables, and selects the optimal operation scheme through comprehensive comparative analysis. Simulation results of a hydropower station in the Han River Basin show that when the output is taken as the control condition, the waste water is small, the power generation benefit is high, and the risk of the water level outside boundary is within the acceptable range. Considering the risk and benefit of reservoir operation and taking output as the control condition, it has significant advantages over water level and flow.

Natural Flow Simulation in a Baisin considering Artificial Water Cycle

This study seeks to regionalize the parameters of the grid-based rainfall-runoff model (GRM) and simulate the natural flow considering an artificial water cycle. We established a water supply and demand network for the Han River basin, derived data related to the artificial water cycle through various organizations, and performed a water budget analysis by reflecting the simulated natural flow. When comparing the results of regionalization using only the Chungju Dam parameters and those using the Chungju Dam and Soyanggang Dam parameters, both results for the simulated flow showed good agreement with the observed flow, and the fitness evaluation results were also high (pentad: NSE 0.913–0.977, KGE 0.795–0.935, CC 0.974–0.995). The natural flow simulated by the GRM and TANK indicated that both models were able to reproduce the observed data well. Water budget analyses were performed for different time intervals, and daily analysis exhibited relatively lower fitness than pentad analysis (daily NSE 0.887-0.963, KGE 0.792-0.928, CC 0.960-0.990), but no significant difference was observed. The results indicated that the simulation of natural flow through the GRM was appropriate, and the model was sufficiently applicable to a disturbed watershed.

Research on water resources collaborative utilization based on complex networks: A case study of the Han River Basin

As China's social economy grows and the demand for water resources increases, the Han River Basin faces intensified supply-demand conflicts, reducing water resource utilization efficiency and threatening regional development. To address this, a network evolutionary game model based on complex network and evolutionary game theory was developed for collaborative water resource utilization. The study identified key dynamic factors influencing the game in the Han River Basin and analyzed its evolutionary rules. Simulations revealed that the profit-loss ratio and profit distribution rate significantly affect cooperative behavior. Furthermore, the network's topology exhibits small-world characteristics, and factors such as economic preferences, income distribution, and reward-punishment coefficients critically influence cooperation. Considering the current state of water resources and economic development, it is projected that comprehensive cooperation in the basin may take around 11 years to establish.

Non-Linear Response of Alpha and Beta Diversity of Taxonomic and Functional Groups of Phytoplankton to Environmental Factors in Subtropical Reservoirs.

Exploring the response of the diversity of phytoplankton species and functional groups to environmental variables is extremely important in maintaining biodiversity in aquatic ecosystems. Although there were more taxonomic units at the species level than at the functional group level, it remained unclear whether species diversity was more sensitive than functional group diversity to environmental variables. In this study, taxonomic composition and alpha-beta diversity of phytoplankton were investigated in 23 subtropical reservoirs located in the Han River Basin in South China during wet and dry seasons. Structural Equation Modelling (SEM) and Generalized Dissimilarity Modelling (GDM) were employed to validate the response of phytoplankton species and functional group alpha-beta diversities to environmental variables. The results indicated that the community compositions of phytoplankton in eutrophic reservoirs were similar between wet and dry seasons, while there were distinct differences for community composition in oligotrophic-mesotrophic reservoirs between the two seasons. Across all reservoirs, there were no significant differences in alpha and beta diversities of species and functional groups between wet and dry seasons. The SEM and GDM results revealed that total phosphorus was the primary driving factor influencing alpha and beta diversities of species and functional groups in the 23 reservoirs. Meanwhile, the non-linear results of species beta diversity were stronger than the non-linear results of functional group beta diversity, indicating that phytoplankton species exhibited a higher explanatory power in responding to environmental changes compared to that of functional groups. Compared to that of species beta diversity, the response of functional group beta diversity to environmental variables was significantly lower in the dry season. These research findings lead to re-evaluating the common practice relating to the use of phytoplankton functional groups to assess environmental conditions, which may overlook the explanatory power of subtle changes at the species level, especially during periods of habitat diversification in the dry season.

Spatial Analysis of Aquatic Ecological Health under Future Climate Change Using Extreme Gradient Boosting Tree (XGBoost) and SWAT

Climate change not only affects the water resource system but also has a great impact on the aquatic ecosystem, which is complexly linked to various organic and inorganic matter. It is difficult to simulate the current aquatic ecosystem and predict the future system due to the immensity and complexity of aquatic ecosystems; however, a spatial analysis of future aquatic ecological health is necessary if we are to adapt and take action against future climate change. In this study, we evaluated the aquatic ecological health of the Han River basin under the future climate change RCP4.5 and RCP8.5 scenarios using three indices: fish assessment index (FAI), trophic diatom index (TDI), and benthic macroinvertebrate index (BMI). For this, we developed the SWAT-XGBoost linkage algorithm, and the algorithm accuracy for the FAI, TDI, and BMI was 89.3~95.2%. In the case of the FAI and BMI assessment of aquatic ecological health, the upstream Han River was classified as a hot spot. In the case of the TDI, the downstream area of the Han River was classified as a cold spot. However, as the current TDI downstream was classified as grades D and E, continuous management is needed.

백제의 한자 수용과 문서 행정 시기

Baekje showed mature Chinese literature, such as writing poetry and literature using Chinese characters, no different from China, in the Sabi era. And document administration was thoroughly implemented. However, The period of Baekje's acceptance of Chinese characters and administration of documents cannot be specified due to a lack of related historical and archaeological materials, or it tends to be considered too late as the period of King Geunchogo, so I wrote this article to look into it. Baekje's acceptance of Chinese characters was examined through whether and when the Baekje constituent group accepted Chinese characters. Baekje was composed of the ruling class of the Buyeo and Goguryeo migrant groups and the under-dominated class of the Han tribes and Ye tribes. The Baekje ruling group split from Goguryeo, which accepted Chinese characters from the time of its founding and started document administration. The Baekje ruling group also knew about Chinese characters and document administration as the ruling group of Goguryeo at one time. Moreover, the Baekje ruling group established a site in the Han River basin after passing through the Chinese county area, where thorough document administration was implemented. The Baekje ruling group had an understanding of Chinese characters and document administration. In addition, the Han and Ye tribes, which were the dominant class of Baekje, were at the center of the Han River basin, and the Jin and Han societies, which were first located in the Han River basin, also accepted Chinese characters through the influence of Chinese residents and exchanges with Hansa-gun during each period of chaos in Chinese history, and knew or participated in the document administration of Chinese county. Baekje accepted and used Chinese characters from the beginning of its foundation because both the ruling and under-dominated groups of Baekje accepted Chinese characters. Since there was no direct record of the beginning of the administration of documents in Baekje, the beginning of the administration of documents was inferred by reviewing historical facts that presuppose the beginning of the administration of documents in Baekje. The establishment of educational institutions and the compilation of history books took place during the reign of King Geunchogo. In addition, Archaeological materials related to inscriptions from the Hanseong period are generally considered to be from the 4th century or later. This can be said to have begun the administration of documents from the time of King Geuncho's reign, as previous understanding. However, looking at the floor stone of the 道(直) name, the period of implementation of Baekje's ritual system and official ranking system, and diplomatic relations with China and counties, there is room to place the beginning of Baekje's document administration in the reign of King Goi. If we limit the period, Baekje document administration began at least from 260, the 27th year of King Goi's reign, when the official rank system was implemented. If interpreted more positively, document administration may have been implemented from the 7th year of King Goi's reign (240), when the military commander was established and the military authority of the central and local regions was reorganized. The reorganization of central and local military authority was carried out by the military command and control of all Baekje armies. This means unification of military government, and this can only be achieved through clear document administration.

Characterization of Drought Propagation in the Han River Basin Based on Chaos Theory and Nonlinear Dynamic System

This study characterized drought propagation in the Han River basin based on chaos theory and nonlinear dynamic systems. The nonlinear complexity of drought propagation, specifically between meteorological and hydrological droughts, was identified using convergent cross-mapping and phase-space reconstruction techniques. The analysis results on the causality of drought propagation between meteorological and hydrological droughts revealed that among the 24 middle-sized watersheds of the Han River basin, 11 watersheds had bidirectional causality, and the other 13 watersheds had one-directional causality. This study also confirmed that there were large correlations between the two drought types when 12 of the 13 watersheds with one-directional causality had a lag time of 4 months and the remaining watershed had a delay time of 7 months. The complexity of the interaction between different droughts was confirmed through adjustments of key parameters, such as the embedding dimension, time delay, correlation dimension, and Lyapunov exponent. The approach proposed in this study made it possible to analyze the nonlinear dynamic characteristics of drought propagation, which have not been analyzed in previous studies.

Evaluating the impact of various driving factors on future water supply and demands

ABSTRACT The mismatch between water supply and demand challenges sustainable human–environment development. Understanding future water supply–demand dynamics and underlying mechanisms is crucial for water resource sustainability. This study presents a framework for analyzing water supply–demand dynamics and their driving mechanisms under future land use/land cover (LULC) changes in China's Han River (HR) Basin using PLUS, InVEST, and geographic detector models. Results show precipitation increased slowly (0.64) from 2000 to 2020, while potential evapotranspiration slightly decreased (−0.02). By 2030, under the scenarios of the natural increase scenario (NIS), economic development scenario (EDS), and ecological protection scenario (EPS), significant changes are projected in forest, cropland, and construction land. The future impact of LULC on water supply is concentrated between 0.17 and 0.45%, while its effect on water demand is significant, approximately 10%. The water security index (WSI) in the HR Basin gradually declined from 0.118 to 0.078. Particularly in the EPS scenario, WSI improves (0.103). In the future, LULC will increasingly influence water yield in conjunction with other factors, but excessive precipitation will dampen the impact of other factors on water yield. This study enhances understanding of water resource balance evolution, enabling sustainable LULC development for ecological conservation and economic coordination.

Driving Factors and Trade-Offs/Synergies Analysis of the Spatiotemporal Changes of Multiple Ecosystem Services in the Han River Basin, China

Uncovering the trade-offs and synergy relationship of multiple ecosystem services (ESs) is important for scientific ecosystem management and the improvement of ecological service functions. In this study, we investigated the spatiotemporal changes of four typical ES types (i.e., water yield (WY), carbon storage (CS), soil conservation (SC), and habitat quality (HQ)) from 2001 to 2020 in the Han River Basin (HRB). Meanwhile, the trade-offs and synergies between paired ESs and the socioecological drivers of these ESs were further explored. The results showed that grassland, cropland, and bare land decreased by 12,141.3 km2, 624.09 km2, and 22.1 km2 during the study period, respectively, which can be attributed to their conversion to forests in the HRB. Temporally, the WY, CS, and SC all showed a continuously increasing trend. Spatially, WY and HQ exhibited bipolar clustering characteristics, with WY exhibiting low-value clustering in the upstream and high-value clustering in the downstream, while CS showed the clustering characteristics of a scattered distribution of cold and hot spots from 2001 to 2020. The spatial patterns of aggregation locations in CS and HQ were relatively similar, with clusters of higher ES values mainly distributed in the western and central regions and clusters of lower ES values mainly located in the eastern and southeastern regions, while the aggregation of WY was spatially concentrated. Overall, the CS showed a significant positive correlation with HQ, but a significant negative correlation with WY. Spatially, WY and HQ, CS, and SC showed a substantial trade-off relationship in the northwest and southeast parts of the study area, while HQ, CS, and SC mainly exhibited a synergistic relationship in most parts of the study area. Slope and temperature had high influencing factor coefficients on multiple ESs; the mixed effect of terrain and natural factors was significantly greater than the impact of a single factor on ESs, and terrain factors played an essential role in the changes in ESs. The findings can provide technical and theoretical support for integrated scientific ecosystem management and sustainable development at the local scale.

Comparative Study of Low Flow Frequency Analysis Using Bivariate Copula Model at Soyanggang Dam and Chungju Dam

A univariate analysis that relies solely on precipitation data in low flow frequency analysis is a technique to express meteorological drought, so it is limited to analyzing the characteristics of hydrological drought related to available water resources. In addition, if the data for the model calibration are insufficient, the uncertainty of a single variable limits the construction of a reliable model. To improve this problem, a frequency analysis was performed by constructing a bivariate copula model as a multivariate model with a high correlation between variables targeting reservoir inflows. The methodology utilizes the theory of runs to identify low flow events, establishing a threshold based on the mandatory regional water supply plan, and determining the low flow duration and cumulative water deficit. The Gumbel copula function, effective in capturing correlations between hydrological variables, was applied to derive a joint bivariate probability distribution, facilitating the calculation of combined low flow event return periods. This study compared low flow frequencies at Soyanggang dam (’74–’22) and Chungju dam (’86–‘22), which are in the same Han River basin but have different capacities and water demands, using a bivariate copula model. The top four extreme low flow events for the two adjacent dam basins did not occur in the same year and, in the years of the extreme low flow events at one of the two dam basins, there was an insignificant magnitude at the remaining dam basin. This result is noteworthy because it shows that the possibility of extreme low flow events appearing simultaneously in both watersheds is not as high as expected. The operational efficiency can be improved by setting the coordinated operation rules of the two reservoirs using the copula dependency structure.

백제 무령왕의 고구려 공격과 북방 경계

During his 23-year reign, King Muryeong of Baekje (501-523) primarily focused on military activities. According to the Samguk Sagi (History of the Three Kingdoms), King Muryeong's military operations were primarily concentrated in the northern regions, including Goguryeo and Malgal. This marks a clear difference from the military activities of his predecessor, King Dongseong, who engaged with neighboring countries such as Goguryeo, Silla, and Tamna. Upon his ascension to the throne, King Muryeong immediately attacked Goguryeo. This marked the first preemptive attack on Goguryeo since the 15th year of King Gaeru's reign (469). Subsequently, he continued to engage in battles against Goguryeo. Goguryeo's King Munjamyeong responded to Baekje's aggression by either leading Malgal forces or actively countering with Malgal's support. However, after suffering a crushing defeat at the hands of the cavalry led directly by King Muryeong in the Battle of Wicheon, Goguryeo ceased further warfare with Baekje. At that time, Goguryeo was focused on diplomatic relations with the Northern Wei and consolidating its internal affairs. Additionally, tensions with Silla, which was expanding northward, posed a significant challenge. Given these circumstances, Goguryeo was not in a position to engage in full-scale warfare with Baekje. During the early years of King Muryeong's reign, there were attempts to advance northward, even reaching Sugokseong Fortress in Shin'gye, Hwanghae Province. However, most of the conflicts with Goguryeo occurred in Yeoncheon and Pocheon in Gyeonggi Province. Therefore, the northern border between Baekje and Goguryeo during King Myryeong's reign can be considered the line between the Imjin River and the Han River, north of the Han River in the northern region of Gyeonggi Province. During King Muryeong's reign, the Han River basin controlled by Goguryeo was limited to the southern Han River northeast of Baekje. The posthumous title 'Muryeong-wang' reflects the military achievements garnered from the wars with Goguryeo.

Evaluation of water shortage and instream flows of shared rivers in South Korea according to the dam operations in North Korea

Abstract The Korean Peninsula's mountainous terrain poses challenges to effective water resource management. Notably, two significant river basins, North Han River and Imjin River basins, are essentially shared rivers originating in North Korea. After the construction of various dams in North Korea, billions of tons per year of water annually decreased from the upper reaches of these rivers of North Korea to South Korea. This study conducted an impact analysis on two major river basins affected by dam operations in North Korea. Both before and after the Imnam Dam operation, significant reduction (27.7%) in the average monthly inflow was observed, and the total release of the Hwacheon Dam in South Korea decreased by 40.2%. The analysis of instream flow indicated that the operation of dams in North Korea had a substantial impact on fulfilling instream flow requirements for dams located in North Han River and Imjin River basins. To ensure instream flow, this study proposed two plans. The first plan involved the utilization of existing dams in the North Han River basin, while the second plan suggested connecting the dams in North Korea, taking into account the shared rivers.

Characterizing future changes in compound flood risk by capturing the dependence between rainfall and river flow: An application to the Yangtze River Basin, China

Compound floods induced by co-occurring multiple drivers may exacerbate the flood impacts and lead to larger flood damage. Exploring future changes in compound flood risk is imperative for flood management and disaster reduction. This study attempts to investigate future changes in compound flood risk across the Yangtze River Basin during 2030 ∼ 2100. Future river flow was projected using an improved hydrological model and pairwise series of extremes of rainfall and river flow were extracted from both observed and projected series. Subsequently, stochastic pairs of rainfall and river flow characterizing compound floods were proportionally sampled from their bivariate joint distributions. The damage from each compound flood was obtained from the flood damage function constructed by Random Forests (RF). Further, the expected annual damage (EAD) was calculated to investigate future changes in compound flood risk. Results show that: (1) Future annual maximums of rainfall and river flow are expected to increase by 14.51 % ∼ 66.13 % and 1.72 % ∼ 55.73 % in the mainstream and northern tributaries, while future annual peak discharge in the southern tributaries (except for the Dongting Lake Basin) is expected to decrease by 4.18 % ∼ 12.30 %. A similar spatial distribution of future changes is also found in the bivariate joint distribution of rainfall and river flow. (2) The high coefficient of determination (R2) of 0.84 indicates the satisfactory simulation and projection capacity of the constructed flood damage function. The positive stepped relationship between flood damage and rainfall or river flow reflects the superposition of multiple flood damage processes. (3) The Han River Basin, the Jialing River Basin, and the two-lakes (the Dongting and Poyang Lakes) area face great threat from compound floods in both historical and future periods. Future compound flood risk is expected to increase by 13.43 % ∼ 46.04 % in these regions except for the Poyang Lake Basin, while future risk is expected to increase by 2.03 % ∼ 46.04 % in the whole basin. The findings help improve the understanding of future flood risk variations in the Yangtze River Basin and provide essential information for damage reduction.

Response of blue-green water to climate and vegetation changes in the water source region of China's South-North water Diversion Project

The characteristics of water fluctuations within the basin have remained ambiguous in recent years due to climate and vegetation changes, posing a challenge to the planning and utilization of regional water resources. This study coupled the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model, which can consider vegetation dynamics information and evapotranspiration physical mechanisms, into the Distributed Time Variant Gain Model (DTVGM) to improve the hydrological simulation accuracy under changing environments. Based on different simulation scenarios of the coupled model, the effects of climate and vegetation changes on hydrological processes were fully investigated using blue and green water (BW and GW) as assessment metrics. The upper Han River Basin (UHRB), as water source for the Central Line Project of China’s South-North Water Diversion (CSNWD), was selected as a typical basin for the study, results indicated that: (1) The DTVGM coupled with PT-JPL could better reflect the spatiotemporal patterns of major hydrological processes (runoff, evapotranspiration, and soil moisture) in UHRB from 2001 to 2019; (2) The BW in UHRB exhibited decreasing trend from 2001 to 2019, while the GW on the contrary. Surface runoff (Rs), vegetation transpiration (Et), and soil moisture (W) contributed most in the components of BW and GW; (3) Vegetation change dominated by greening in UHRB, which facilitated the transformation of BW to GW in the basin, and it increased the proportion of GW mainly by promoting Et. BW was mainly influenced by precipitation, but vegetation change altered the original correlation between climatic factors and hydrological processes. This study can support the management of water resources in the basin under changing environments.

Identification of ecological restoration areas based on the ecological safety security assessment of wetland-hydrological ecological corridors: A case study of the Han River Basin in China

In recent years, wetland resources have been threatened by human activities such as mining, agriculture and construction land expansion, and problems such as shrinkage of wetland area and deterioration of water quality have emerged, impeding the exchange of materials between wetlands and reducing the ecological function of wetlands. Water systems are important channels for material exchange between wetland sources, and evaluating the ecological safety of wetland–water system ecological corridors can aid in efficiently delineating ecological restoration areas and identifying ecological problems. In this paper, the ecological safety of wetland–hydrological ecological corridors in the Han River Basin was evaluated, and ecological restoration areas were delineated by adopting the method of “identification of source areas - construction of resistance surfaces - extraction of wetland–hydrological ecological corridors” with the watershed as the research unit. The study identified wetland–hydrological ecological corridors with a total length of 7,589.77 km and delineated 31 sections of wetland–hydrological ecological corridors with a total length of 1,076 km; these corridors were located in the Hanzhong Canyon area, tributaries of the Danjiang River and Tangbai River, and tributaries of the main streams below Danjiangkou. Among them, 8 sections of the primary corridor account for 27 %, 14 sections of the secondary corridor account for 33 %, and 9 sections of the tertiary corridor account for 39 %. This study breaks administrative boundaries, emphasizes the correlation between wetlands and water bodies, highlights the integrity of ecosystems, and establishes a multidimensional systematic restoration methodology of “points, lines and surfaces”, which provides guidelines for the long-term planning of ecological corridors of wetlands and water systems in large-scale regions.