SSS11.2

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.

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.

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.

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.

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.

 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.

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.

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.

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.

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.

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.

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.

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.