XU Bingxiang, YU Kunxia, LI Zhanbin, LI Peng, PAN Minghang, HANG Penglei, HUANG Gaohua, YANG Jianhua, ZHANG Wenjing
Comprehensive risk assessment of check dam system in Jiuyuangou watershed
[Background] Sick and dangerous check dams will seriously threaten people's lives and economic and property safety, and restrict the healthy development of soil and water conservation and ecological construction in the Loess Plateau. To promote the ecological protection and high-quality development of the Yellow River Basin, it is particularly important to identify the risk factors of check dams, ensure the safety of people's lives and production,and promote local economic development.[Methods] Check dams in the Jiuyuangou watershed,which is a demonstration basin of check dam construction on the Loess Plateau, were taken as the research object. To build a multi-objective and multi-level risk early assessment system, 10 risk assessment indicators were selected from the 4 criterion levels of loss risk, structural risk, flood risk and operation management through data collection, hydrological statistics, and numerical simulation, the indicator weights were determined based on expert scoring results using fuzzy analytic hierarchy process, and the risk status of check dam systems in the Jiuyuangou watershed were finally evaluated based on the comprehensive score.[Results] 1) The operation management risk level was the highest among the four criterion levels, which was a severely dangerous state for most check dams due to the ineffectiveness of check dam management. The structural risks were of most check dams in a mildly risky state as most check dams were rarely damaged, and the junction of the discharge structure and the dam body also worked well. The flood risk and loss risk increased with the increase of the rainfall return period. The flood risk of most check dams was in a moderately risky state, but the risk rate increased greatly when the designed rainstorm increased from 10 years reappearing period to 300 years reappearing period, the loss risk of most check dams were generally safe when designed rainfall was 10 years reappearing period and became mildly dangerous under 300 years reappearing period.2) When the designed rainstorm increased from 10 years reappearing period to 300 years reappearing period, the severely dangerous check dams increased from 0 to 5.3%, the mildly dangerous check dams decreased from 60.5% to 42.1%. The risk of check dam system in Jiuyuangou watershed increased with the increase of the designed rainstorm.[Conclusions] This study assessed the operation risks of the check dam system in the Jiuyuangou watershed under different rainfall return periods, which may provide a scientific basis for the operation and management of check dams,toensure the safe andstable operation of check damsand lay a foundation for the establishment of safety emergency mechanisms and operational measures.
LUO Weidong, GAN Shu, YUAN Xiping, GAO Sha, HU Lin, YUAN Xinyue
Morphological characterization of complex micro-landscapes based on UAV high-resolution DEM: Take the mountainous area on the southern rim of Dinosaur valley as an example
[Background] In order to improve the acquisition rate and accuracy of terrain factors required by soil erosion models, it is urgent to carry out in-depth analysis and research on the morphological characteristics of mountains.[Methods] The mountainous area at the southern margin of the Dinosaur valley, Lufeng county, Yunnan province, where the tectonic erosion landforms are mainly dominated, was selected as the test area. The images of the test area were obtained by drones and a point cloud was constructed. The point cloud was filtered and calculated from the ground point data through the natural field interpolation method. A high-resolution DEM model was constructed based on the pixel values. Based on this model, according to the principles of terrain factor validity, computability, and mutual independence of factors, 4 single-factor indicators of slope, surface roughness, standard curvature, and surface cut depth were selected for the micro-topography. After quantification, different weights were finally assigned to the above 4 single-factor indicators and a TCI model was constructed, which was divided into 5 levels according to low complex, relatively less complex, medium complex, relatively more complex and highly complex with a step size of 2.[Results] Considering the degree of dispersion of elevation values and the degree of dispersion of errors from the true value, a DEM with a resolution of 0.5 m with SD and R of only 0.016 7 and 0.017 3, respectively was selected. The weights of the 4 topographic factors of slope, surface roughness, standard curvature and surface cutting depth calculated by the coefficient of variation method were 0.282, 0.171, 0.259 and 0.288, respectively. Statistics on the distribution areas of the 5 levels in the TCI model showed that the overall area of relatively more complex and high complexity was relatively concentrated, mainly distributed on both sides of the mountain, and the two together accounted for 22.95% of the survey area. The two sides of the mountain were uneven due to the influence of the subtropical monsoon climate. At the same time, the field survey found that red soil and purple soil with severe desertification were widely distributed, indicating that the soil was eroded by weathering in this area.[Conclusions] The TCI model constructed using the terrain factors obtained by constructing high-resolution DEM with UAV can accurately reflect the terrain information of the region, and has certain research value for the analysis of soil erosion problems.
LOU Mengjie, SHI Mingchang, GUO Hongyang, YANG Jianying
Water conservation analysis of Baiyangdian-Daqing River basin based on InVEST model
[Background] Baiyangdian-Daqing River basin is a momentous water source and ecological barrier in Xiong'an New Area and plays important roles in regional ecology. The distribution pattern of water producing function and the special spatial distribution pattern of water conservation capacity in this area were revealed, which provides a basis for determining priority protection area, planning water conservation forest, and improving water producing capacity of the basin.[Methods] Taking Baiyangdian-Daqing River basin as the study area, we quantitatively evaluated water yield and analyzed water conservation using the water yield module of InVEST model. Then, the spatial distribution difference of water conservation under different conditions was obtained by geostatistical method. Water conservation was normalized to identify the importance level of regional water conservation function.[Results] According to InVEST model calculation, the present situation of water production in Baiyangdian-Daqing River basin is 3.58×109 m3, the present situation of water conservation is approximately 1.71×108 m3, and the average water yield is 83.91 mm. Basin water production and water conservation show obvious spatial heterogeneity. The spatial distribution characteristics of water production and water conservation are consistent, which increases slowly from the Tai-hang Mountains in the northwest to the shallow mountain area in the middle of the basin, and then decreases gradually from the shallow mountain area to the plains in the southeast of the basin. Geostatistical results show that water conservation capacity of different land cover types is significantly different, and the order of water conservation capacity from high to low is shrub > arbor > mixed forest > farmland> grassland > construction land > bare soil > bare rock. The normalized results indicate that low and moderate grade area of water conservation covered the largest area, which accounted for 60% of the study area, while the high importance area of water conservation is located in the hilly area, the importance level of shallow mountain area lower than hilly area. The importance and potential of the conservation function of the basin are comprehensively evaluated based on the natural conditions of the basin and related researches. The results show that the central hilly area has abundant rainfall, is little affected by human activities, and is covered with a large area of bare soil and shrubs, which has great water storage potential.[Conclusions] Thus, the spatial distribution of water yield and water conservation function is not uniform due to the influence of precipitation difference, landform, land use, human disturbance, and other factors. Baiyangdian-Daqing River basin is a key link in the eco-city construction of Xiong'an New Area. Through comprehensive evaluation of the conservation function of the basin, the allocation of water resources in the basin is optimized to enhance the sustainable utilization of water resources, and to improve the service efficiency of the ecosystem, and accelerate the clean watershed treatment.
JIA Yanfeng, WANG Jianan, FAN Haoming, SHI Hao, ZHOU Lili, MA Renming
Effects and optimal allocation of soil and water conservation measures on the multi-agent combined soil erosion in the Mollisol region, Northeast China
[Background] The Mollisol region is an important food production base for China, where is suffering from multi-agent combined soil erosion. Soil erosion caused food production reduced by 14.1%. Although the area of soil conservation measures there exceeded 104 m2, these measures were mostly aimed to a single erosion, ignoring the complex characteristics of soil erosion. There were still 218 667 km2 of soil erosion in the Mollisol region, Northeast China in 2019. Whether these soil conservation measures for single erosion can effectively prevent and control the combined erosion of multiple agents needs to be answered urgently.[Methods] Total 115 literatures concerned in soil conservation measures and its benefits about the Mollisol region, Northeast China during 1990-2020 were collected. The effects of conservation measures to prevent water erosion, wind erosion, and freeze/thaw-snowmelt erosion on the sloping farmland were analyzed separately. Taking the slope farmland <5° in the Manchuanmangang for an example, the effect of the current configuration of measures was evaluated and optimized based on the multiple agents erosion intensity.[Results] 1) The conservation measures for black soil sloping farmland were effective in control water erosion. Engineering measures had the best benefits, with a sediment reduction of about 90%, followed by biological measures with a support practice factor of 0.219, and tillage practices reduced sedimentation by more than 70%. 2) Although there were no measures for wind erosion in the non-wind-dominated area,biological measures and conservation tillage measures played a role in wind erosion control. 3) Considering from the two aspects of reducing freeze-thaw damage and regulating snowmelt runoff, measures such as contour farming, conservation tillage, terraces, buffer strip with bund, and vegetation buffer had the functions of weakening freeze-thaw damage, regulating snowmelt runoff, and reducing snowmelt erosion ultimately. 4) Soil losses caused by water erosion accounted for about 73% of the total combined erosion of the black soil area, thus 73% of the soil loss tolerance 1.46 t/hm2 was selected as the control index. And USLE was employed to evaluate and optimize the measures. Based on the current configuration optimization, it was recommended to add conservation tillage and vegetation buffers on the contour farming for 1°-3° slope farmland, and to increase conservation tillage measures on the contour farming and buffer strip with bund for 3°-5° slope farmland.[Conclusions] Although soil conservation measures for black soil sloping farmland have the ability to prevent and control multi-agent compound erosion, the contribution rate of multi-agent erosion should be considered in the configuration of measures in the future.
Research status and trends of vegetation pattern affecting erosion and sediment yield based on CiteSpace
[Background] Land degradation is one of the most critical environmental problems in the world. Soil erosion, a vital cause of land degradation, has been engaged more attention. Vegetation has become an important measurement for soil erosion control and sediment yield reduction. Current studies cannot fully meet the scientific and technological needs of scientific distribution and optimal distribution in the process of vegetation restoration to achieve the optimal eco-economic effect. At present, the impact of vegetation type and quantity on soil erosion and sediment yield has been relatively clear. However, how vegetation landscape patterns influence soil erosion and sediment yield is still unclear, which has become a hotspot.[Methods] CiteSpace, a bibliometric analysis tool, was used to analyze articles published between 2005 and 2020. All the articles were searched from the Web of Science Core Collection with subject "vegetation" "landscape pattern" "soil and water loss" and "erosion". Basic data, for example, articles number, nationality, the title of publication, institution, author, keywords, and burst time were statistically analyzed. Cluster analysis was carried out on the results, and the burst period of keywords was calculated. Combining with typical reports and reviews, the current situation and progress of assessment model methods, eco-hydrological effects, and coupling of different factors were reviewed. Suggestions for the trend of promoting this research topic were summarized in those bases.[Results] The number of published articles was increasing year by year. Keywords that were still in the burst period in 2020 were related to eco-hydrology. These keywords indicated that researchers were focusing on quantifying vegetation patterns and their internal structure. The key points of research from 2005 to 2020 were model evaluation, eco-hydrological benefits, and coupling factors. These studies were aimed to reveal the process and mechanism of vegetation patterns affecting erosion and sediment production and to quantify its relationship, and then to improve the prediction accuracy of the model or optimize the regulation mode, which may provide a basis for land use management and ecological environment governance. In the future, more attentions should be paid to 1) improve the connectivity theory and related indicators, and clarifying the process mechanism of erosion affected by vegetation patterns; 2) strengthen the optimization of models and optimize the characterization indices, and then to promote the ability of simulating the sediment responses to vegetation patterns; 3) focus on the balance of coupling factors and function, enriching the research connotation.[Conclusions] Vegetation pattern affects the local hydrological process by changing the local sediment connectivity and plays an important role in reducing erosion. The concept of connectivity introduced into related research will provide new perspectives to the study on the response of sediment to vegetation pattern changes. In the future, it is necessary to improve the relevant indicators, to improve the accuracy of the model, and to emphasize the coupling influence and function weight.
History of soil and water conservation technology in the loess hilly and gully region of Inner Mongolia
[Background] The loess hilly and gully region of China is one of the regions with the most serious soil erosion in China and even in the world. The loess hilly and gully region of Inner Mongolia is an ecologically fragile and sensitive agro-pastoral ecotone. The research on the evolution of soil and water conservation technology in this area may have guiding significance in the development of soil and water conservation and the construction of beautiful China.[Methods] This paper systematically studied the evolution of water and soil conservation technology in the loess hilly-gully region of Inner Mongolia in the past 70 years using a large number of first-hand historical archives. Then this paper clarified the inheritance and innovation of soil and water conservation technology in 5 historical stages:1956-1962, 1963-1978, 1979-1985, 1986-1996, and 1997 to the present, and explored the evolution trend and driving factors of soil and water conservation technologies.[Results] 1) The soil and water conservation technology was mainly composed of multiple technologies from 1956 to 1962. Water and soil conservation technology mainly focused on the construction of basic farmland from 1963 to 1978. From 1979 to 1985, comprehensive management of small watershed was the main soil and water conservation technology. From 1986 to 1996, the soil and water conservation technology was used to control gullies and build key dams. Since 1997, soil and water conservation technology has been developing in an all-round way with ecological environment construction as the main focus. 2) Water and soil conservation technology experienced a tortuous process of split after long-term integration and then integration after loug-term split. 3) Water and soil conservation technology experienced step-by-step progress from local regulations to industrial standards and then to national standards. 4) Social and human factors led to differences in the implementation quantity and focus direction of water and soil conservation technologies.[Conclusions] The evolution of soil and water conservation technology in the time dimension is driven by national macro policy, the formulation of technical standard, project implementation and the establishment of supporting institutions. However, historical and cultural factors, technical personnel's cultural quality, local economy and state support strength lead to spatial differences in water and soil conservation technologies of similar natural environments. This study may provide theoretical support and scientific reference for the development of soil and water conservation technology in the hilly loess region of Inner Mongolia and similar regions in China.
