SSS11.2

EDI
Linking hydrological connectivity to sustainable watershed management: methods, approaches, and challenges

The management of soil and water resources for sustainable development is critical for human well-being. Over the recent decades, many studies have demonstrated the role of water and sediment connectivity processes in relation to watershed management. Habitat and species protection, improved flood resistance and resilience, and ecosystems management are all vital to maintaining the health of ecosystems. Especially when external factors influence watershed processes and characteristics to maintain optimal connectivity or disconnectivity in diverse ecological niches (hydrology, ecology, geomorphology) is the goal of watershed management. Given the high complexity of hydro-geomorphic systems and the different mechanisms that might influence the efficiency of water and sediment flowing through a watershed, understanding the hydrological and sediment connectivity is critical. Meanwhile, analyzing changes in connectivity over time helps to understand the effects of natural and man-made disturbances on water-sediment flux and related processes. However, we still have very little understanding about connectivity and link all the processes involved. Models are valid tools in this task, but they need to be improved. In this session, we welcome studies focused on connectivity with watershed management. Any contributions related to new methods, approaches to the understanding of connectivity are welcomed. Field monitoring, laboratory simulations, development and application of geomorphometric indices and models are included. This session emphasizes the importance of connectivity in appropriately managing sediment and water-related concerns, and aims at providing important information on when, where, and how to managers in order to control hydrological and geomorphic processes and ultimately achieve sustainable watershed management.

Co-organized by GM4
Convener: Peng Li | Co-conveners: Stefano Crema, Liqin Qu, Omer Yetemen, Peng ShiECSECS, Hu Liu, Yang YuECSECS
Presentations
| Thu, 26 May, 08:30–11:50 (CEST)
 
Room G1

Presentations: Thu, 26 May | Room G1

08:30–08:36
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EGU22-428
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Presentation form not yet defined
Hu Liu, Chan Liu, Yang Yu, Wenzhi Zhao, Zhao Zhange, Li Guo, and Omer Yetemen

Groundwater-dependent ecosystems (GDEs) exist all over the world, especially in water-limited regions. To achieve better water management, it is necessary to map and identify GDEs. Central Asia (CA) is one of the most arid regions in the mid-latitudes and one of the major regions with shallow groundwater tables. However, the role of groundwater in the impacts of climate change and regional anthropogenic activities on environmental risks, especially regional desertification, is inadequately understood due to the limited available research on GDEs. In the present study, a remote sensing-based method was used for mapping GDEs in regional CA, and three means—overlay analysis, correlation analysis, and the water balance method—were adopted to validate the accuracy of the mapping outcomes. Our results indicated that: 1) GDEs were concentrated around large lakes and in central Kazakhstan (between 46°N and 50°N latitudes), and areas "Very Likely" and "Likely" to be GDEs accounted for 36.89%, and 28.85% of the total natural vegetation areas, respectively; 2) at the watershed scale, the Sarysu Basin had the largest proportion (94.02% of the area) of potential GDEs while the Ysyk-Kol Basin had the lowest proportion (17.84%); 3) all the three validation methods indicated a good performance for our GDE mapping results. We concluded that the remote sensing-based GDE identification method can be considered a potential approach for mapping GDEs regionally. Better recognition of relationships among groundwater availability, ecosystem health and groundwater management policies should be developed by conducting further studies, to protect GDEs and to prevent regional land degradation. 

How to cite: Liu, H., Liu, C., Yu, Y., Zhao, W., Zhange, Z., Guo, L., and Yetemen, O.: Mapping Groundwater-dependent Ecosystems in Arid Central Asia: Implications for Controlling Regional Land Degradation, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-428, https://doi.org/10.5194/egusphere-egu22-428, 2022.

08:36–08:42
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EGU22-838
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Virtual presentation
Double-diffusive convection in two-layered sorbing porous media
(withdrawn)
Nikolay Kolchanov and Ekaterina Kolchanova
08:42–08:48
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EGU22-2835
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Virtual presentation
Peng Shi, Lulu Bai, Zhanbin Li, and Peng Li

Grass coverage and check dam construction are important measures for soil and water conservation in Loess Plateau. They have a significant effect on the reduction of runoff and sediment, but the synergistic effects of their regulation of hydrological processes are not well understood. To understand the synergistic effects of grass and check dam construction on water erosion process, physical models of 10 slope-gully systems were established including grass cover slopes (0% and 33%) and dam land settlement slope-gullies (0,1, 2, 3 and 4 m during settlement). The single grass coverage reduced runoff and sediment of 155.91 L and 15155.33 g, respectively. Sediment reduction increased with siltation depth: 4 m (18056.73 g) > 3 m (15990.79 g) > 2 m (14173.79 g) > 1 m (6027.13 g), and the runoff reduction followed as: 4 m (122.21 L) > 3 m (87.48 L) > 2 m (50.37 L) > 1 m (28.77 L). Grass coverage and sedimentation had synergistic effects on water erosion, and the synergistic effects of sediment reduction increased with sedimentation process: 4 m (19.83%) > 3 m (18.68%) > 2 m (17.39%) > 1 m (16.70%). The results indicated that grass coverage on the slope and dam land sedimentation had a synergistic effect on hydrological process, which should not be ignored in the evaluation of soil and water conservation measures regulation.

How to cite: Shi, P., Bai, L., Li, Z., and Li, P.: Synergistic effects of grass coverage and dam land sedimentation on runoff and sediment yields in slope-gully system on the Loess Plateau of China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-2835, https://doi.org/10.5194/egusphere-egu22-2835, 2022.

08:48–08:54
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EGU22-3413
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Presentation form not yet defined
Siyu Cai and Zhe Li

This paper used a long series of daily flow data of Ankang section from 1960 to 2020 to diagnose eco-hydrological variations in the upper reaches of the Hanjiang River. Aiming at the problems of the single hydrological variable used in watershed hydrological variation diagnosis, a method for extracting the most Ecologically Relevant Hydrologic Indicators (ERHIs) based on sensitive indicators of similar years and diagnosing the variation period was proposed. In this method, 32 hydrological indexes in the IHA index system were used to diagnose hydrological variation instead of the traditional single index, and the IHA index were refined into wet season index and dry season index based on different hydrological characteristics. Ten years were randomly selected from the long series flow data as the sample years and ten similar years corresponding to each sample year were selected for the determination of ERHIs. The indexes with strong variation were selected from ERHIs to diagnose hydrological variation. Through comprehensive variation diagnosis calculation, the indexes with strong variation were the annual average duration index of low flow and the annual minimum 1-day flow index, with the period of variation from 1973 to 1977, and from 1973 to 1986, respectively. Combined with the climate change and human activities in the past 60 years, it is found that the time period of climate change and water conservancy project construction is consistent with the time period diagnosed in this paper. Therefore, the variation period from 1973 to 1986 is reasonable. Through this study, it can be concluded that the method has strong practicability in the diagnosis of hydrological variation, and the conclusion is consistent with the practice, which can fully reflect the characteristics of hydrological changes in the Hanjiang River Basin.

How to cite: Cai, S. and Li, Z.: Study on the variation and diagnostic methods of eco-hydrological regime in Hanjiang River Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-3413, https://doi.org/10.5194/egusphere-egu22-3413, 2022.

08:54–09:00
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EGU22-4291
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Presentation form not yet defined
chen Zhang

With the promotion and development of the South-to-North Water Diversion Project, a flood forecasting of the Chao River Basin in Miyun is crucial. Many hydrological researchers have done little research in the northern China, especially Chao River Basin. Because of the climate and environmental factors in the Chao River Basin, the watershed often has more rainfall but no runoff flow, which exacerbates the difficulty of northern flood forecasting. With the rapid development of technology in surface observation and remote sensing technologies, data sources have been enriched. Today, how to improve algorithmic techniques and how to use multi-source data to reduce the uncertainty on the flood forecasting have been paid more and more attention.

The data assimilation method can improve the timeliness and the accuracy of numerical forecasting, which has been applied widely and developed rapidly in the hydrology field. In this paper, the ensemble Kalman filter algorithm was used for assimilation prediction.Considering that the watershed underlying surface caused by human activities changes frequently, the parameters are not static. In order to ensure the authenticity and accuracy of the study, the parameters were added into the variables, serving as the state variables to be estimated simultaneously, and the observed flow data were updated and corrected in real time considering the uncertainty of the model itself, the model parameters and the observed data, and the ensemble Kalman filter and the Xin'anjiang model were coupled and assimilated. As the Xin'anjiang model is based on the theory of full-scale production, it is mainly applied in the humid and semi-humid areas, while the Miyun basin is semi-humid and semi-arid climate. The Xin'anjiang model was modified to a saturated storage and excess infiltration mixed model, and data assimilation used multi-sources of soil data and streamflow, which can improve the accuracy of flood forecasting.

The Chao River Basin consists of three hydrological stations, which are Dage Station, Gubeikou Station and Xiahui Station from the upstream to the downstream. According to return period or frequency, the flood grades were divided into small floods, medium floods and large floods, which were compared with non-assimilation, streamflow assimilation-only, combined assimilation of streamflow and romote sensing soil data, combined assimilation of streamflow and correct soil data. Results showed that the accuracy of multi-source data assimilation of small floods after adding streamflow and soil data was increased, while the precision of medium floods and large floods was high enough when the floods were streamflow assimilation-only. And from the perspective of assimilation results, small floods were better than medium floods and large floods, and the effect of upstream assimilation was better than downstream. In order to study the influencing factors of the assimilation effect, the Gubeikou Hydrological Station was taken as an example to analyze the effects of parameter mean, variance, the number of samples and the correlation between parameters and variables on the assimilation processes. This study can provide reference for different levels of flood assimilation prediction methods and related assimilation processes.

How to cite: Zhang, C.: Application of Ensemble Kalman Filtering to the Flood Prediction of Chao River Basin in North China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4291, https://doi.org/10.5194/egusphere-egu22-4291, 2022.

09:00–09:06
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EGU22-4321
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ECS
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Virtual presentation
Zhenni Wu, Jantiene Baartman, João Nunes, and Manuel López-Vicente

Hydrological and sediment dynamics have changed a lot on the Chinese Loess Plateau during the last six decades due to large scale land use changes and numerous water regulation actions. Understanding the mechanism of sediment transport change and its effects is of great importance to food and environmental security. Computer-implemented numerical approaches are useful to map and assess spatio-temporal patterns in sediment dynamics. This study evaluates monthly and annual sediment connectivity in the Wei River Basin (134,800 km2) at the basin and sub-basin scales using the aggregated index of sediment connectivity (AIC). For the first time, this index is applied on this relatively large regional scale. The two objectives are to (1) evaluate the performance of the AIC at the regional scale and (2) analyse the role played by each input in the sediment patterns over the months of the year. The Jing sub-basin shows the highest sediment connectivity, while the Beiluo sub-basin has the lowest sediment connectivity on average, due to better ecological restoration in Beiluo sub-basin. Within the year, sediment connectivity is highest in April and lowest in January, due to the rainfall regime and land cover variations. Among the inputs of the AIC, the rainfall factor has the highest effect on sediment connectivity, implying that functional connectivity (graded by rainfall and soil cover) dominates over sediment dynamic more effectively than structural connectivity (mainly determined by topography and soil permeability). This study provides one of the first large-scale estimates of spatial and temporal sediment connectivity, which can be further employed to implement regional ecological construction and catchment management.

How to cite: Wu, Z., Baartman, J., Nunes, J., and López-Vicente, M.: Intra-annual sediment dynamic assessment in the Wei River Basin, China, using the AIC functional-structural connectivity index, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4321, https://doi.org/10.5194/egusphere-egu22-4321, 2022.

09:06–09:12
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EGU22-4456
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ECS
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Virtual presentation
heng wu

Rational land use can enhance soil nutrient sequestration and control erosion, but the mechanisms of the ecological restoration on soil aggregate-associated carbon and nitrogen are still not well understood. A large-scale ecological restoration program was launched in the Loess Plateau during 1990s. The ecological restoration programs involved converting slope farmland to forest, grassland, shrub land and terrace. We studied their effects in relation to slope land as control on soil aggregate structure and stability, and their associated organic carbon and total nitrogen contents to 60 cm soil depth in the Loess Plateau. Our results indicate that the restoration practices reduced soil aggregate fragmentation, increased soil structure stability and transformed micro-aggregates into small and large aggregates. Comparing with the soil aggregate >0.25mm in slope land, the amount of that in forest, grass land, shrub land and terrace increased by 71%, 66%, 46%, and 35%, respectively, which improved soil health overall. The mean weight diameter (MWD) of aggregate indicated that soil aggregate stability (SAS) increased and soil hydraulic erosion resistance improved. In conclusion, ecological restoration directly or indirectly affected SAS through the influence of soil organic carbon (SOC) and total nitrogen (TN) in different soil layers. The results would provide a scientific basis for soil quality control and rational use of land resources.

How to cite: wu, H.: Changes in soil aggregate fractions, stability and associated organic carbon and nitrogen in different land use types in the Loess Plateau, China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4456, https://doi.org/10.5194/egusphere-egu22-4456, 2022.

09:12–09:18
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EGU22-4542
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ECS
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Presentation form not yet defined
Yi Zhang

As a major carbon emitter, China’s decarbonisation will contribute to global climate action. The verification of topsoil C distribution in China and its influence factors was an urgent problem for the carbon neutrality of China. . To address this issue, topsoil (0-20 cm) and climate data for 7,857 sites were selected. The soil organic carbon (SOC) distribution in forestland, grassland, and farmland in seven districts of China was analyzed. The correlations and contribution rates of external (elevation-E, temperature-T, and rainfall-R) and internal factors (fractal dimension-D, soil total nitrogen-STN, soil total phosphorus-STP, pH, and C/N ratio) were explored. We found that SOC in China gradually increased from the west to east, with a mean value of 11.20 g kg-1. The SOC content in northeast China was higher than elsewhere in the country. The SOC of different land use types followed the order of forestland > farmland > grassland (P <0.05). All of the factors influencing SOC, with the exception of R, had distinct differences in their spatial patterns and land use types. The most important internal factor was STN, followed by STP, while the most important external factor was T, followed by R. The factor that made the greatest contribution to the SOC was STN. There was a relationship between the SOC distribution and the Hu Huanyong Line, the 6.5-10.5℃ T contour line in the south of China. These results provide theoretical support for soil C cycle and prediction research, which will enable the issues surrounding climate change in China to be confronted.

Key words: soil organic carbon, distribution pattern, internal factors, external factors, China

How to cite: Zhang, Y.: Topsoil organic carbon in China is mainly affected by internal nitrogen and external temperature, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4542, https://doi.org/10.5194/egusphere-egu22-4542, 2022.

09:18–09:24
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EGU22-4638
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ECS
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Virtual presentation
xiaojun Liu

Land use change is a major influencing factor in ecological and environmental issues, and sedimentation and runoff variations caused by land use change have emerged as important research areas. The aims of this study were to determine changes in landscape patterns, and runoff and sedimentation characteristics, and to investigate the relationship between landscape metrics (LMs), runoff, and sedimentation in two watersheds. Four key results were obtained. (1) Grassland (GRA) was the dominant landscape in the two watersheds. Unused land (UNL) in the Tuweihe watershed and farmland (FAR) in the Gushanchuan watershed experienced the greatest transformations, with changes in area of 453.94 and 52.85 km2, respectively, between 1985 and 2010. (2) The landscape in the watersheds tended to become regular, connected, and aggregated. The landscape stability of the Tuweihe watershed was higher than that of the Gushanchuan watershed. (3) Annual runoff and sediment levels gradually decreased. The runoff in the Tuweihe watershed was greater than in the Gushanchuan watershed, but the sediment yields of the two watersheds were similar. There was a significant relationship between annual runoff and sedimentation (P <0.01). (4) The LMs had a significant linear relationship with runoff and sedimentation (P <0.01). The correlation coefficients for LMs and runoff were higher than those for LMs and annual sedimentation yield. Shannon’s evenness index (SHEI) and the patch cohesion index (COHESION) had the greatest effects on runoff and sedimentation. Our results suggested that the relationship between the LMs, and runoff and sedimentation could provide a scientific basis for the prevention and treatment of water loss and soil erosion.
Keywords: land use/cover change; landscape; runoff; sedimentation; Yellow River

How to cite: Liu, X.: Landscape analysis of runoff and sedimentation based on land use/cover change in two typical watersheds on the Loess Plateau, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4638, https://doi.org/10.5194/egusphere-egu22-4638, 2022.

09:24–09:30
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EGU22-4745
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On-site presentation
yaotao Xu

[Objective] to clarify the spatial distribution pattern of land use and the change of eco-environmental quality effect caused by its transformation in Ningxia. [Method] Based on the four high-precision remote sensing interpretation images of land use status from 1990 to 2018, the regional land use classification system of Ningxia was constructed according to the leading function of "Sansheng" land, and the geographic information Atlas method, eco-environmental quality index, center of gravity transfer model and the ecological contribution rate of land use transformation were adopted. [Results] from 1990 to 2018, the production land increased by 14.3%, the living land increased by 29.1%, and the grassland ecological land decreased by 138.1km2 per year; The overall eco-environmental quality index of Ningxia has deteriorated, from 0.455 in 1990 to 0.438 in 2018. The area of medium quality area accounts for about 65% of the whole region, forming the main body of eco-environmental quality; According to the center of gravity model, the eco-environmental quality in northern Ningxia has been improved; From 1990 to 2018, the improvement and deterioration of regional ecological environment in Ningxia coexisted, and the trend of ecological environment deterioration was greater than that of improvement. [Conclusion] the quality of ecological environment in Ningxia has decreased, and the run of agricultural production land on forage ecological land is the main reason.

How to cite: Xu, Y.:  Functional transformation of Ecological-production-living land use and Eco-environmental effects in Ningxia, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-4745, https://doi.org/10.5194/egusphere-egu22-4745, 2022.

09:30–09:36
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EGU22-5243
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Presentation form not yet defined
Yangfan Feng

 In order to scientifically understand the effect of the construction of check dams on the erosion dynamic process and the ability to reduce gully erosion in the wind-water cross erosion area, in this study, the Xiliugou Basin, one of the ten tributaries, was taken as the research area, and the differences of flood process, erosion dynamics and energy in gully after the construction of check dams were simulated and quantitatively calculated by coupling the distributed hydrological model MIKE SHE and the one-dimensional hydrodynamic model MIKE 11. The reduction of gully erosion by check dams was also estimated. The results showed that: (1) The check dams decreased the flood peak and flood volume of the outlet section by 40.90% and 35.85%, respectively. (2) The average flow velocity, runoff shear force and runoff power along the main gully of the watershed were dropped by 21.66%, 22.02% and 34.31%, respectively. (3) During the planned operation period of the project, the check dams reduced the amount of gully erosion by 3.31 million tons under the condition of multi-year average precipitation. The construction of check dams has significantly changed the flooding process of Xiliugou Basin, which alleviated the erosion dynamic along the main channel as well as provided effective erosion mitigation effects.

How to cite: Feng, Y.: SIMULATION  on the Gully Erosion Reduction Ability of Check Dam—A Case Study of Xiliugou Basin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5243, https://doi.org/10.5194/egusphere-egu22-5243, 2022.

09:36–09:42
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EGU22-5412
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Virtual presentation
Wiebke Bebermeier, Robin Saase, and Brigitta Schütt

In the dry zone of Sri Lanka, human-made reservoirs, being connected by canals and spillways serve since 2000 years for the collection, storage and distribution of rainfall and runoff and provide irrigation water for the cultivation of paddy (Bebermeier et al. 2017). These systems, known as tank-cascade system, focus on numerous state of the art watershed management strategies like flood prevention, soil erosion control, water quality control and are based on an elaborated governance system (Schütt et al. 2013).

In this presentation we will analyse the dependence these reservoirs (locally called tanks or wewas) in the headwaters of the Aruvi Aru catchment on precipitation as a means of evaluating their efficiency. The the Aruvi Aru is located in the dry zone of Sri Lanka, and numerous human made reservoirs characterize its catchment. Methodologically the study is based on a correlation of climatically and hydrologically drought indices, by applying the Standardized Precipitation Index (SPI) after McKee et al. (1993) to precipitation data at different time scales and to water-level data of five major tanks in the catchment. Achieved results show that near normal present-day average precipitation is appropriate to fill the investigated tanks. As main driving factor of water level changes, the precipitation of the last 6–12 months was identified. Two other factors were responsible for water level changes of the tanks: these are: (i) catchment size together with the buffering capacity of the upstream catchment and (ii) management practices. As the overall conclusion of our study shows, the tanks functioned efficiently within their system boundaries (Saase et al. 2020). In consequence this water harvesting and management system, being well adopted to local conditions, has a high capacity to mitigate effects of climate change in the dry zone of Sri Lanka.

References:

Bebermeier, W., Meister, J., Withanachchi, C.R., Middelhaufe, I. and Schütt, B., 2017. Tank Cascade Systems as a Sustainable Measure of Watershed Management in South Asia. Water, 9(3). https://doi.org/10.3390/w9030231

McKee, T.B.; Doesken, N.J.; Kleist, J., 1993. The relationship of drought frequency and duration to time scales. In Proceedings of the Eighth Conference on Applied Climatology, Anaheim, CA, USA, 17–22 January 1993; American Meteorological Society: Anaheim, CA, USA; pp. 179–184.

Saase, R. Schütt, B. and Bebermeier, W. 2020. Analyzing the Dependence of Major Tanks in the Headwaters of the Aruvi Aru Catchment on Precipitation. Applying Drought Indices to Meteorological and Hydrological Data. Water, 12(10), 2941; https://doi.org/10.3390/w12102941

Schütt, B., Bebermeier, W., Meister, J. and Withanachchi, C.R., 2013. Characterisation of the Rota Wewa tank cascade system in the vicinity of Anuradhapura, Sri Lanka. Erde, 144(1): 51- 68.

How to cite: Bebermeier, W., Saase, R., and Schütt, B.: Analyzing the Dependence of Major Tanks in the Headwaters of the Aruvi Aru Catchment on Precipitation. Applying Drought Indices to Meteorological and Hydrological Data as a means to evaluate their efficiency , EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-5412, https://doi.org/10.5194/egusphere-egu22-5412, 2022.

09:42–10:00
Coffee break
10:20–10:26
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EGU22-6799
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Virtual presentation
Lulu Bai and Peng Shi

Quantitative analysis of sediment sources is crucial for soil and water conservation. For instance, composite fingerprint identification technology is widely used to study sediment sources in small dam-controlled watersheds, but its use in historical reconstructions of soil erosion in sediment source areas is uncommon. As soil erosion is a major issue in some areas of China, we propose the combination of flood couplet construction with the fingerprint method to estimate soil erosion in sediment source areas of a typical check dam on the Loess Plateau, which is known for its severe soil erosion. A flood couplet, based on the activity of 137Cs in the sediment, was constructed, and the historic soil erosion was calculated using soil bulk density and storage capacity curves. The contribution rate of the sediment sources was calculated by using the fingerprint method, and the amount of erosion in the sediment source areas was estimated. We found 29 flood events (1956–1990); the total sediment volume was approximately 56121 m3, and the sediment yield was approximately 77430 t. The best fingerprint combination (Cr, Ni, V, and TOC) allowed to a 97.2% the recognition of the sediment sources. The contribution rates of ditches, cultivated land, grassland, and shrub land were 44.89%, 26.38%, 10.49%, and 18.24%, respectively. Meanwhile, the average sediment yield of ditches, farmland, grassland, and shrub land were 1227, 751, 512, and 279 t, respectively. These results provide an effective scientific basis for the rational allocation of soil and water conservation measures in small watersheds.

How to cite: Bai, L. and Shi, P.: Soil erosion of sediment sources and their impact factors in a check dam control watershed on the Loess Plateau of China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-6799, https://doi.org/10.5194/egusphere-egu22-6799, 2022.

10:26–10:32
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EGU22-7179
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Virtual presentation
Jin Hua Huang

In order to scientifically understand the spatial distribution characteristics of hydrological hydrodynamics in river basins under different conditions (land use, rainfall), the flood process of Wan'an Small Watershed was simulated by coupling the distributed hydrological model MIKE SHE and the one-dimensional hydrodynamic model MIKE11, revealing the variation characteristics of hydrodynamic parameters at different scales of main ditch and branch ditch in the basin. The results show that: (1) Different rainfall types and underlying surface conditions changed the distribution of erosion dynamics in small watershed channels, and the erosion dynamic parameters of ditches with smaller cumulative rainfall and rain intensity decreased greater. (2) The erosion power of runoff in small watersheds is characterized by the change trend of large upstream, small downstream, large tributaries and small main ditches, and the changes in the upper and middle reaches are more drastic than those in the downstream. (3) The impact of land use change on heavy rainfall over short duration is small, and the variation of erosion dynamic parameters of main ditch is significantly greater than that of branch ditch. The research results can provide a scientific reference for the planning of soil and water conservation in the Yangtze River Basin.

Keywords: MIKE model; Model simulation; hydrological hydrodynamics; rainfall types; 

How to cite: Huang, J. H.: SPATIAL and temporal distribution characteristics of erosion dynamics in watersheds under the influence of different rainfall types and underlying surface, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7179, https://doi.org/10.5194/egusphere-egu22-7179, 2022.

10:32–10:38
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EGU22-8631
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ECS
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Presentation form not yet defined
Peng Liu and Yanqing Li

Abstract: The contrastive analysis of soil bulk density, moisture content, organic matter spatial heterogeneity karst hillslopes can serves as theoretical guidance for preventing soil degradation in Nandong subterranean stream basin. This study analysis the 0-20cm, 20-40cm soil bulk density, moisture and organic matter spatial heterogeneity Zhumashao depression basing on classical statistics and geostatistics methods. Research results showed that: the soil organic matter aberrance in Zhumashao depression is the largest, up to 70.62%, the variation of bulk density and water, respectively 15.25% and 11.29%. According to the statistical analysis of different types of land use, the soil moisture content can be ordered as follows, cultivated land <grassland<shrubs, and the bulk density can be ordered as shrubs <grassland<cultivated land, and organic matter content can be ordered as cultivated land<grassland<shrubs. The bulk density of the northern slope is higher than the southern slope, and the coefficient of variation is lower than the southern slope. The soil moisture and organic matter are lower than the southern slope, and the coefficient of variation is higher than the southern slope. It also showed a significant negative correlation between soil bulk density and soil moisture, as well as a significant negative correlation between soil bulk density and organic matter, and the correlation coefficients were -0.609 and -0.581, respectively. In 0-20 cm, the soil moisture, bulk density, organic matter and the spherical model are fitter and fitting degree of R2 were 0.911, 0.977, and 0.922, respectively. In 20-40 cm, the soil moisture, bulk density, organic matter and Gauss model match better and fitting degree of R2 were 0.647, 0.730, and 0.881, respectively. The nugget coefficient shows that the spatial correlation of 0-20 cm factors, 20-40 cm is weak, which may be related to human activities in space. Through the analysis of normal kriging interpolation, soil bulk density in the south slope of the depression is less than those in the north slope, as well as the water and organic matter is more than those in the north slope. The soil moisture and organic matter at the bottom of the depression have the minimum value, while the bulk density has the maximum value. The water content and organic matter at the bottom and middle slope are the lowest, and the bulk density is the highest; the moisture and organic matter are higher on the downhill and uphill, and the bulk density is lower.

Key words: spatial heterogeneity; karst slope; land use, soil moisture, bulk density, organic matter

 

How to cite: Liu, P. and Li, Y.: Spatial heterogeneity of soil bulk density and moisture content,organic of karst depression slope, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-8631, https://doi.org/10.5194/egusphere-egu22-8631, 2022.

10:38–10:44
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EGU22-9360
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ECS
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Virtual presentation
Yang Yu, Min Shu, Yiying Hui, Daoming Ma, Danyi Huang, and Ming Gong

Water is the main factor restricting and maintaining biological activities, and hydrological connectivity is closely related to many ecological processes. As a process that characterizes the transfer of energy and organisms among landscapes during the water cycle, hydrological connectivity establishes the interconnection between the material and energy flow of the landscape during the water cycle. Using bibliometric methods, hydrological connectivity related researches were searched via Web of Science and CNKI database, combining with Bibexcel, Ucient and Citespace procedures to obtain high-frequency words and keyword co-occurrence network views, we reviewed the research progress of hydrological connectivity abroad. The results showed that: 1) Regarding hydrological connectivity, the volume of publications both at home and abroad has shown an upward trend. The number of the publications showed significantly increased. 2) In terms of the frequency of keywords, many studies tend to focus on the research on hydrological connectivity of different types of ecosystem structure and function changes. 3) The analysis of the frequency of outbreak words showed that hydrological connectivity and climate change, biodiversity and ecosystem services have become research hotspots in this field. 4) According to the co-occurrence network view, we found that hydrological connectivity and ecological processes, the impact of different types of ecosystem hydrological connectivity on material transport, and the impact of changes in ecosystem structure and function on hydrological connectivity are the current research hotspots. Carrying out multi-scale hydrological connectivity mapping and multi-scale hydrological connectivity quantitative assessment and model simulation based on geographic information technology and long-term field monitoring data are the trends of future hydrological connectivity research directions.

How to cite: Yu, Y., Shu, M., Hui, Y., Ma, D., Huang, D., and Gong, M.: Research progresses and trends of hydrological connectivity based on bibliometrics, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-9360, https://doi.org/10.5194/egusphere-egu22-9360, 2022.

10:44–10:50
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EGU22-10684
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Presentation form not yet defined
Racha Elkadiri, Henrique Momm, John Simpson, and Katy Moore

Conservation agriculture has proved to be beneficial in terms of securing yield, sustainability of natural resources, and biodiversity of the natural and cultivated ecosystems. The effectiveness of existing and planned conservation practices in targeted watersheds in Tennessee, USA, were evaluated. Two watershed systems were selected in coordination with the U.S. Department of Agriculture - National Resources Conservation Service (NRCS) including four watersheds in Northern Middle Tennessee and six watersheds in West Tennessee.

Our objective was accomplished using the Annualized Agricultural Non-Point Source (AnnAGNPS) watershed pollution model to generate watershed simulations for our study areas. The main inputs databases needed include: (1) a 3-m LiDAR based Digital Elevation Model (DEM), (2) weather data from 23 NOAA stations and from AGNPS Climate Generator (agGEM), (3) soil data from the Web Soil Survey (WSS) and complementary soil description of physical and chemical properties from the USDA Soil Data Access website, (4) land use and land cover data describing crop type from 2009 to 2019 from the National Agricultural Statistics Service’s Cropland Data Layer (CDL), and (5) typical farming management practices that were generated by integrating spatiotemporal crop type information at raster grid cell scale (from CDL), average crop yield at county scale (from USDA-NASS), and one-year farming management schedule (from USDA-NRCS). In addition to the AnnAGNPS simulation representing existing conditions, 34 additional AnnAGNPS simulations representing alternative scenarios of conservation practices were evaluated. Eight scenarios depicting the effectiveness of sediment retention ponds under various stream order, stream length, and sediment yield conditions; 4 scenarios were run to depict the effectiveness of crop rotation under various sediment yield-based conditions; 4 scenarios were run to depict the effectiveness of the conservation reserve program (CRP) under various sediment yield-based conditions; and 18 scenarios were run to depict the effectiveness of riparian forest buffer under various buffer width, and sediment yield- based conditions.

Preliminary results indicate that the vegetative riparian buffer is a very effective practice that could eliminate up to 80% of the total watershed sediment yield if implemented in every stream of the watershed. Alternatively, creating and maintaining a riparian buffer in just agricultural fields could decrease the sediment yield by 42% to 50% depending on width and by 5 to 6% when implemented in the top sediment producing fields. The projected reduction from sediment retention ponds of sediment yield is 95% in the case of 233 ponds strategically placed across the Western TN watershed system. Crop rotation simulations show that this conservation practice could decrease sediment yield by up to 12% in the extreme scenario of applying it in every soybean agricultural field in the study area, making it less effective than the other simulated conservation practices. CRP decreases the sediment yield by more than 81% percent in the most optimistic scenario and by 10% in the least optimistic scenario.

Findings from this study support efforts in guiding future conservation strategies development contributing to water quality and sediment erosion improvement in the state of Tennessee and across the US.

How to cite: Elkadiri, R., Momm, H., Simpson, J., and Moore, K.: Evaluation of the Effectiveness of Soil Conservation Practices in Agricultural Watersheds in Tennessee, USA, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10684, https://doi.org/10.5194/egusphere-egu22-10684, 2022.

10:50–10:56
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EGU22-10804
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Presentation form not yet defined
Liqin Qu, Tingwu Lei, Chenyan Zhou, and Zhiqiang Liu

Sediment transport capacity is not only an important parameter for rill erosion modeling but also a critical parameter for estimating other rill erosion model parameters. Sediment capacity is difficult to be measured, especially at gentle slopes with limited rill length. In this study, a special flume with variable slope gradients in different sections was implemented to feed and to transport sediments. Silt loam soil materials, collected from Beijing, were used in the laboratory experiments to measure sediment transport capacity to verify the method,. The experiments were designed under slope gradients of 5, 10, 15, 20 and 25° and flow rate of 2, 4, 8 and 16 L/min. Measured sediment transport capacity values were compared with reference measurements from other rill erosion experiments with similar soil materials. At high slope gradients of 15, 20 and 25°, the newly-suggested method produced almost the same transport capacity values as measured through rill erosion process data. Under the low slope gradients of 5 and 10°, limited length of eroding rill used in the previous experiments was not capable of producing sufficient sediments to make the flow reach sediment transport capacity. Data analysis indicates that rill erosion with a 8 m long flume produced maximum sediment concentrations about 36% lower than the values measured with the new method under low slope gradients of 5 and 10°. The sediment transport capacities at lower slopes measured with the new method followed the same trend as those at higher slopes. The experimental results indicated that the new method is capable of supplying sufficient sediments to ensure the flow approach transport capacity measurement. The method proposed in this study can provide a feasible approach for estimating sediment transport capacity as an  important model parameter for soil erosion prediction.

How to cite: Qu, L., Lei, T., Zhou, C., and Liu, Z.: Measuring Sediment Transport Capacity of Concentrated Water Flow with a New Erosion Feeding Method, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-10804, https://doi.org/10.5194/egusphere-egu22-10804, 2022.

10:56–11:02
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EGU22-11687
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ECS
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Presentation form not yet defined
Huanyong Liu and Qi Yang*

Abstract:In order to grasp the temporal and spatial variation of runoff and sediment transport and the relationship between runoff and sediment in the Yellow River, the Mann-Kendall test was used to analyze the trend of runoff and sediment load based on the data of runoff and sediment load from 1950 to 2020 at Tongguan station. This paper adopted a method based on moving correlation coefficient to diagnose the variation of watershed runoff and sediment, which was verified with cumulative curve method and regression analysis method. The Pearson III distribution was selected to fit the runoff and sediment distribution before and after the variation, and the combined runoff and sediment distribution was established based on Copula function. The variation characteristics of runoff and sediment at Tongguan station were compared and analyzed to study the wetness-dryness encountering of runoff and sediment at different times. Results show that: (1) The annual runoff at Tongguan station underwent a stepwise decrease until about 1990, and the amount of sediment load continued to decrease after 1983. (2) Taking 1985 as the segmentation point, the mean value of runoff and sediment decreased from 1986 to 2020 compared with that from 1956 to 1985. When the design frequency P≤90%, the runoff and sediment load decreased, while when P>90%, the runoff decreased and sediment load increased. (3) In both time periods, the synchronous frequency of runoff and sediment load wetness-dryness was greater than the asynchronous frequency of wetness-dryness, and the probability of wetness-dryness combination was the smallest, and the frequency of each combination was more uniform after the variation period. The implementation of soil and water conservation measures and the control of water and sediment by large-scale water conservancy projects were the main reasons that led to the change of the wetness-dryness of water and sediment. This work was supported by the National Key Research and Development Program [grant number 2016YFC0500802].

Keywords: runoff; sediment load; Copula function; the Yellow River Basin

How to cite: Liu, H. and Yang*, Q.: Variation characteristics of runoff and sediment in the middle reaches of the Yellow River based on Copula function, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11687, https://doi.org/10.5194/egusphere-egu22-11687, 2022.

11:02–11:08
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EGU22-11767
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ECS
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On-site presentation
Alice Bernini, Rike Becker, and Michael Maerker

The use of hydrological models can be a suitable basis for the development of sustainable land use and respective water management policies, according to the sustainable development goals (SDGs) of EU. In this study, a process-based numerical model was developed, to determine the hydrological dynamics of a micro-scale basin in a flat and intensely used agricultural area that is partly irrigated, in the Lombardy Region, Italy. In this area, agriculture has a fundamental role in the local hydrological cycle, indeed, landuse and land management practices date back to medieval times with the construction of irrigation channels and reuse of water along the fluvial terrace cascade of the Ticino River. From a hydrological point of view the study area is very complex: there is almost no natural surface runoff, but prevailing vertical soil water dynamics. The water infiltrates on the highest and oldest fluvial terrace level and reemerges in form of springs (risorgive) at the base of the terrace escarpments and is further used for irrigation on the next terrace level.

The objective of this study is to assess the hydrological dynamics of this complex area that is getting under increasing pressure related to climate changes and socioeconomic transformations.  In order to achieve the study goals, we applied the Soil Water Assessment Tool (SWAT), a complex hydrological model that works at the basin scale and generates variable spatio-temporal outputs and is being applied successfully worldwide for soil and water management studies. We present the methodological approach for deriving the model input and boundary conditions. Moreover, we show the effects of selecting different model entity configurations as well as calibration and validation procedures. First preliminary results show that SWAT is able to simulate the general hydrological dynamics of the area according to the use of satellite soil moisture and evapotranspiration data. In addition, through local soil moisture measurements carried out in the field, qualitative evaluation of infiltration capacities have been made and with these measurements it will be possible to validate the model. Hence, the model results obtained, provide information on the soil water dynamics that can be used as a basis for studying future scenarios (i.e., impacts of climate change or different management such as different irrigation schemes).

How to cite: Bernini, A., Becker, R., and Maerker, M.: Assessment of the soil-water dynamics in an intensively used agricultural lowland area of Lombary, Italy, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11767, https://doi.org/10.5194/egusphere-egu22-11767, 2022.

11:08–11:14
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EGU22-11889
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ECS
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Presentation form not yet defined
Jingjing Xu and Qi Yang

Abstract: Making clear the sediment reduction benefits of soil and water conservation measures is the primary in the researches of ecological benefits of soil and water conservation. In order to make the sediment reduction benefits of China clear, relevant monitoring and research results were collected which focus on determining the amount of sediment reduction per unit area for single measure by provincial administrative units. Taking the average of all the results of sediment reduction benefits when single measure exists more than one result. Then, the basic characteristics and factors in the existed measures in eight soil and water loss zones dominated by water erosion in China have been discussed. The results indicated that the sediment reduction modulus of soil and water conservation measures in the order: 4146.17 t·km-2·a-1 in terraces < 3064.73 t·km-2·a-1 in soil and water conservation forests < 2819.16 t·km-2·a-1 in fruit-bearing forests < 2273.77 t·km-2·a-1 in artificial grass planting < 1973.31 t·km-2·a-1 in blockading administration; the sediment reduction modulus of eight soil and water loss zones in the order: 2400.87 t·km-2·a-1 in the Southwest Karst Region < 2493.93 t·km-2·a-1 in the Northern Earth and Rock Mountain Region < 2741.69 t·km-2·a-1 in the Southern Red Soil Region < 2831.48 t·km-2·a-1 in the Northern Wind-blown Sandland Region < 3061.22 t·km-2·a-1 in the Southwest Purple Soil Region < 3088.04 t·km-2·a-1 in the Northeast Black Soil Region < 3187.89 t·km-2·a-1 in the Loess Plateau Region < 3259.82 t·km-2·a-1 in the Qinghai-Tibet Plateau Region. Therefore, terrace was completely worthy of promotion in suitable regions. This review reflected the effect of the soil and water conservation in China in recent years, and provided substantial contribution on the control of regional water and soil loss. This work was supported by the National Key Research and Development Program [grant number 2016YFC0500802].

Key words: sediment reduction benefits; soil and water conservation measures; soil and water loss zones; China

How to cite: Xu, J. and Yang, Q.: A Review of Sediment Reduction Benefits of Soil and Water Conservation Measures in China, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11889, https://doi.org/10.5194/egusphere-egu22-11889, 2022.

11:14–11:20
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EGU22-11976
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ECS
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Virtual presentation
Laurène Marien, Rossano Ciampalini, Feliciana Licciardello, Emanuela Rita Giuffrida, Amandine Valérie Pastor, Frederic Huard, and Damien Raclot

Soil is an essential natural resource, non-renewable on a human time scale, which is degraded mainly by water erosion, especially in the Mediterranean context. Erosion can cause significant soil losses at the plot and catchment level through the transfer of sediments which, in a framework of global changes (climate and land use), may severely increase in intensity.

This study was part of the MASCC/Arimnet2 project, which aimed to assess the vulnerability of Mediterranean agricultural soils to global changes and contribute to the definition of sustainable agricultural conservation strategies for Mediterranean agro-ecosystems. In the challenge of reconciling agricultural production, environmental protection and the effects of climate change, we believe that some trade-offs are possible.

We assessed the impact of global change scenarios on soil loss in a mixed pasture watershed in the Cannata basin (Sicily) by 2050, testing strategies to maintain agricultural production and protect soil resources. With the LANDSOIL model, we simulated soil erosion on different climatic (RCP4.5) and land use scenarios derived from a combination of plausible socio-economic conditions. The land use scenarios have been designed according two principal axes: agricultural production and soil conservation. All scenarios tend towards an increase in crops (wheat and orchard) over different degrees represented by the productivity axis. We also adopted a main differentiation between intensive and extensive practices for pasture, and between conventional and conservative practices for wheat and orchard. 

The simulation results show that climate change can lead to a decrease in erosion. The evolution of erosion is also strongly influenced by land use. Environmental protection and sustainability scenarios limit soil erosion compared to the most productive scenarios which, on the contrary, may result in an increase. Reducing intensive grazing in favor of conservation wheat and arboriculture, increases the cultivated area and can decrease soil erosion by 2050 horizon. The use of a suitable land use scenarios can contribute to environmental protection, sustainability, and provide levers to meet food production requirements.

 

Key words

Global change, climate, erosion, land use, modelling, agricultural practices, pasture.

How to cite: Marien, L., Ciampalini, R., Licciardello, F., Giuffrida, E. R., Pastor, A. V., Huard, F., and Raclot, D.: Impact of global changes on soil erosion in an Italian basin of mixed pastures (Sicily), EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11976, https://doi.org/10.5194/egusphere-egu22-11976, 2022.

11:20–11:26
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EGU22-12473
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ECS
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Virtual presentation
Mingyang Liu, Xiangzhou Xu, and Guang Ran

The megacities in China experienced increasing impacts from the urban floods due to the climate change in the past ten years. However, it is still unknown how to deal with the potential hazards under the impact of extreme precipitation. This paper briefly reviews the general characteristics and challenges of urban flooding in China with a case study of the extreme rainstorm in Zhengzhou on 20 July 2021. Results indicate that, to comprehensively protect a megacity with existing building standards and emergency plans is difficult under the extreme rainstorms, and the disruption of weak lifeline facilities, e.g. the road network, may further disrupt the provisions from neighbouring cities. This study offers a unique perspective reflecting a multi-scale approach from a single local city to regional area, an urban cluster or even a country on the urban floods control, urban infrastructure design and policy development. In more details, the measures are anticipated to increase the control rate of annual rainfall via the development of sponge city, improve monitoring and forecasting in the urban area, and enhance the risk-response strategies from the local government. The study strongly suggests expand the experiences and achievements of the flood management from a disaster area to adjacent or distant cities coupled with different pathways including government cooperation, water conservation practices, information exchange or human migration. The policymakers in a megacity are also encouraged to update the viewpoints for the policies and strategies to control floods. Hopefully a clue for relatively effective water management and land use for the sustainable urban development may be obtained from the study.

How to cite: Liu, M., Xu, X., and Ran, G.: How megacities respond to urban pluvial floods in China: Policy recommendations, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12473, https://doi.org/10.5194/egusphere-egu22-12473, 2022.

11:26–11:32
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EGU22-12695
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ECS
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Presentation form not yet defined
Jin Tian and Xiangzhou Xu

Vegetation has long been recognized as an efficient way of preventing soil erosion. However, the effects of plants on gravity erosion are still broadly unknown. This study conducted a plant-root modelling experiment with the Pinus tabuliformis and Amorpha fruticosa under heavy rainfall on a micro-plot with a slope of 4° in the Wangdong Village, Shaanxi Province. The results showed that: (1) As the depth of the soil increases, the soil becomes more compacted and the influence of tree and shrub roots on soil consolidation ability increases. In the shallow soil with the depth of 20 cm , the maximum soil shear strength was 17 kpa and the maximum soil hardness was 21 N/cm2 next to Pinus tabuliformis, while in the deep soil with the depth of 40 cm, the maximum soil shear strength was 22 kpa and the maximum soil hardness was 44 N/cm2. In the shallow soil, the maximum soil shear strength was 16 kpa and the maximum soil hardness was 20 N/cm2 next to Amorpha fruticosa, while in the deep soil the maximum soil shear strength was 19 kpa and the maximum soil hardness was 48 N/cm2. (2) The differences of the root types make the plants differ in their soil consolidation abilities, for the tree root have a stronger consolidation ability than shrub roots. In the shallow soils, the soil water content next to Pinus tabuliformis was slightly lower than that of Amorpha fruticosa, while in deeper soils they were close to each other, so the soil cohesion next to Pinus tabuliformis was slightly higher than that of soil next to Amorpha fruticose. The maximum soil cohesion next to Pinus tabuliformis was 22 kpa and that of soil next to Amorpha fruticosa was 19 kpa. The maximum soil hardness next to Pinus tabuliformis was 44 N/cm2 and that of soil next to Amorpha fruticosa was 48 N/cm2.

How to cite: Tian, J. and Xu, X.: Effects of transported plant on soil physical properties, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-12695, https://doi.org/10.5194/egusphere-egu22-12695, 2022.

11:32–11:50