Assessing the potential of changing land use for reducing soil erosion and sediment yield of catchments: a case study in the highlands of northern Ethiopia

Reservoir sedimentation is the most serious threat for water harvesting schemes and hydroelectric power dams in Ethiopia. Designing watershed conservation strategies and management is crucial to reduce the rate of sedimentation. Because different landscape types have varying potentials for enhancing erosion processes, site‐ and process‐specific conservation measures are needed to target an appropriate intervention to the most needed locations. In this study, a GIS‐based distributed soil erosion/deposition model was used to simulate the potential of land‐use and cover (LUC) changes and conservation measures for reducing water induced soil erosion and potential sediment yield for two catchments in northern Ethiopia. LUC change and conservation measures targeted gully and stream buffers, protection of steep slopes and protection of areas with soil loss greater than a given threshold. The results show that land management measures targeted at hot‐spot areas of erosion and gully formation could reduce potential annual sediment yield from catchments by approximately 60% compared with the current losses. The study demonstrates the potential of a GIS‐based LUC‐redesign approach as a tool for optimizing land‐use and management strategies to reduce run‐off and erosion rates in the highlands of northern Ethiopia.     

Evaluation of soil and water conservation measures in a semi‐arid river basin in Tunisia using SWAT

The Merguellil catchment (central Tunisia) is a typical Mediterranean semi‐arid basin, which suffers from regular water shortage aggravated by current droughts. Over recent decades, the continuous construction of small and large dams and soil and water conservation works (i.e. contour ridges) have taken place within this watershed. However, little is known about the effect of these water‐harvesting systems on the water balance components of arid or semi‐arid basins. In this paper, we present the results of a study, which evaluates the impact of the contour ridges on water balance components and erosion at basin scale by using the soil and water assessment tool model (SWAT). Large dams were modelled as reservoirs, small dams as ponds and contour ridges as potholes that fill with water and increase the percolation into the aquifer. The model predicts that contour ridges produce annually a reduction of 32 and 21% in surface run‐off and river discharge, respectively, and an increase in aquifer recharge of 50%. At the same time, retention of a large proportion of entrained sediment (26%) was modelled.     

红壤丘陵区坡长对作物覆盖坡耕地土壤侵蚀的影响

坡长对坡耕地土壤侵蚀的影响随雨强的不同而变化,为解决南方红壤丘陵区坡耕地水土流失问题,该文采用野外人工模拟降雨的方法,研究了南方红壤丘陵区作物覆盖坡耕地上不同雨强下坡长对其土壤侵蚀的影响,并探讨了侵蚀增强的临界雨强和设置水土保持措施的合理坡长,结果表明:产沙量随坡长延长整体呈增大趋势,但存在一定的波动,二者的关系可用幂函数(决定系数0.84)表示。坡长延长相同长度时,产沙量不呈比例增加,但每隔4 m产沙量增量有减少的趋势,且径流侵蚀产生的泥沙中主要为粒径0.002~0.02 mm的粉粒及粒径0.002 mm的黏粒,加剧了耕地土壤粗化,因此,可每隔4 m设置水土保持措施,有效减少坡耕地水土流失。坡面径流侵蚀产沙量随着雨强的增大而增加,坡长越长,产沙量随雨强增加速度越快,二者呈幂函数关系(决定系数0.76),60 mm/h是红壤丘陵区侵蚀增强的临界雨强;雨强、坡长与产沙量均呈正相关关系,且雨强对坡耕地产沙量的影响较坡长大。对不同雨强下坡长对作物覆盖坡耕地土壤侵蚀的影响研究,可以为南方红壤丘陵区坡耕地水土流失的治理提供一定的理论依据。     

Soil crusts and deposits as sheet erosion indicators in southern Mali

Rills are indicators of erosion, easily recognized by farmers and extension workers. However, they are rare on fields in Mali with slopes of 0–3%, even though run‐off and sheet erosion may be a problem. The suitability of three other soil surface features as erosion indicators was therefore investigated: (1) structural crusts formed by rainfall impact without lateral soil movement; (2) in situ depositional crusts, formed by sedimentation leaving the finest particles on top; and (3) run‐off deposits of fine and coarse sand, formed after the removal of finer particles. Feature (1) occurred on the elevated parts and ridges, whereas (2) and (3) occurred in lower parts and in furrows. Soil cover with a run‐off deposit of coarse sand proved to be a suitable indicator and this was well explained by erosion risk: a 2% increase in slope related to a 9% increase in deposit cover. The extent of this deposit also related well to cotton yield from the previous season: a 30% increase in deposit cover was reflected in a 23% decrease in cotton yield. Only a few farmers confirmed that the deposits were produced by erosion. It is recommended that soil and water conservation programmes pay more attention to the presence of crusts and deposits.     

Impacts of rainstorms on soil erosion and organic matter for different cover crop systems in the western coast agricultural region of Syria

More and more cultivated coastal territories of Syria are being affected by increasing land degradation processes, specifically, by soil erosion due to non‐sustainable soil management. The use of cover crops can be considered an ideal solution to reduce the negative impacts of extreme rainfall events on soil erosion. However, there is no enough information about the main cultivated areas of Syria due to the current conflicts and the very few types of research conducted there. Therefore, the main aim of this research was to assess soil erosion (soil loss and sediment concentration) and hydrological response (run‐off and infiltration) considering the impact of different types of cropping systems on soil organic matter. To achieve this goal, using erosion plots, five grouped natural rainfall events and soil samples were collected, and infiltration measurements were performed between November 2012 and April 2013 (rainy season) on three different cropping systems (wheat, vetch, bean and control) with different sloping gradients (8% and 20%) in Tartous governorate (W Syria). Our results showed a cumulative rainfall amount from 68.8 to 201 mm during the study period. The highest sediment yield was generated in the control and wheat plots, registering 0.468 and 0.368 kg m^?2, respectively, with an inclination of 8%. For an inclination of 20%, the control and wheat plots registered 1.145 and 0.967 kg m^?2, respectively. In comparison with the control plots, there was a decrease in the total eroded organic matter, which ranged from 0.0579 (control) to 0.0289 (bean) kg m^?2 year^?1 in the plots with 20% inclination, and from 0.0233 (control) to 0.0069 (bean) kg m^?2 year^?1 with 8% inclination. To sum up, bean and vetch play an effective role to mitigate soil erosion, delay run‐off and reduce sediment yield. The output of this research provides first insights into the impact of different land uses on soil loss. Also, it could help rural inhabitants and farmers to correctly manage their soils against soil erosion processes.     

Impact of land‐use changes on soil hydraulic properties of Calcaric Regosols on the Loess Plateau,NW China

Vegetation restoration efforts (planting trees and grass) have been effective in controlling soil erosion on the Loess Plateau (NW China). Shifts in land cover result in modifications of soil properties. Yet, whether the hydraulic properties have also been improved by vegetation restoration is still not clear. The objective of this paper was to understand how vegetation restoration alters soil structure and related soil hydraulic properties such as permeability and soil water storage capacity. Three adjacent sites with similar soil texture, soil type, and topography, but different land cover (black locust forest, grassland, and cropland) were selected in a typical small catchment in the middle reaches of the Yellow River (Loess Plateau). Seasonal variation of soil hydraulic properties in topsoil and subsoil were examined. Our study revealed that land‐use type had a significant impact on field‐saturated, near‐saturated hydraulic conductivity, and soil water characteristics. Specifically, conversion from cropland to grass or forests promotes infiltration capacity as a result of increased saturated hydraulic conductivity, air capacity, and macroporosity. Moreover, conversion from cropland to forest tends to promote the creation of mesopores, which increase soil water‐storage capacity. Tillage of cropland created temporarily well‐structured topsoil but compacted subsoil as indicated by low subsoil saturated hydraulic conductivity, air capacity, and plant‐available water capacity. No impact of land cover conversion on unsaturated hydraulic conductivities at suction > 300 cm was found indicating that changes in land cover do not affect functional meso‐ and microporosity. Our work demonstrates that changes in soil hydraulic properties resulting from soil conservation efforts need to be considered when soil conservation measures shall be implemented in water‐limited regions. For ensuring the sustainability of such measures, the impact of soil conversion on water resources and hydrological processes needs to be further investigated.     

土壤侵蚀对坡耕地耕层质量退化作用及其评价趋势展望

土壤侵蚀是导致坡耕地耕层质量退化和土壤生产力不稳定的关键驱动因素。该文从水蚀区坡耕地侵蚀控制和生产功能角度,在解析地块尺度土壤侵蚀、水土保持、农业活动对坡耕地耕层生态过程作用特征的基础上,系统分析了土壤侵蚀对坡耕地耕层质量退化作用、影响效应及作用途径。认为:1)坡耕地耕层质量变化由降雨侵蚀、耕作活动交互作用的生态过程决定,2种作用的时间、空间尺度不同;耕层土壤参数在坡耕地农业生产中作用分为保水、保土、保肥和增产潜力,由地块尺度农作物-耕层耦合效应决定土壤生产能力、坡耕地水土流失特征及耕层侵蚀性退化方向及程度。2)土壤侵蚀对坡耕地耕层质量退化作用表现为土壤性质恶化、土壤质量劣化、土地生产力衰退3个方面,耕层土壤物理性质变异程度大于化学性质变异,径流作用导致的土地生产力衰退大于土壤流失作用。3)坡耕地耕层质量评价指标体系应兼顾侵蚀下降、产量提升2个目标,地块尺度诊断指标有效土层厚度、耕层厚度、土壤容重、土壤抗剪强度、土壤有机质、土壤渗透性可作为合理耕层评价最小数据集;坡耕地合理耕层适宜性分为5级,其诊断指标分级标准宜与土壤侵蚀分级和耕地地力分级衔接。4)坡耕地合理耕层评价未来应密切关注耕层质量诊断指标最小数据集、坡耕地合理耕层阈值/适宜值分级标准、坡耕地水土流失阻控标准拟定3个主要方向。研究可为深入认识坡耕地侵蚀性退化机制,辨识坡耕地合理耕层调控途径以及坡耕地合理耕层构建技术参数提供依据。     

不同改良剂对黄绵土水稳性团聚体的改良效果及其机制

通过室内土柱培养,采用聚丙烯酰胺(Polyacrylamide,PAM)、沃特保水剂、β-环糊精、腐殖酸等4种土壤结构改良剂对黄绵土水稳性团聚体进行改良。结果表明:4种改良剂均可促进>0.25 mm水稳性团聚体的形成,在浓度0.05%～0.40%范围内,其改良效果表现为PAM>β-环糊精>沃特保水剂>腐殖酸,且黄绵土团聚体分形维数显著降低,尤以PAM改良效果最明显;在低浓度条件下,4种改良剂均可有效地降低土壤密度;土壤粒径分布表明,PAM改良黄绵土水稳性团聚体的机制是使<1 mm粒径的团聚体团聚为更大的团聚体,尤其是团聚为>5 mm的团聚体,PAM在4种改良剂中对黄绵土改良效果最好。阐明不同改良剂对黄绵土水稳性团聚体的改良效果及机制,可为合理利用改良剂改良土壤结构提供理论依据。     

The comparative effects of surface applications of organic mulch versus chemical soil conditioners on physical and chemical properties of the soil and on plant growth

An experiment has been carried out to evaluate the influence of different soil conditioners on the physical and chemical properties of the soil and to compare the relative effectiveness of these conditioners in protecting the soil surface against water erosion with organic surface mulching.The results indicated that the physical conditions were highly affected by the different treatments, whereas practically no changes in the chemical status of the soil could be observed.After 2 years, total porosity and infiltration rate were highest in the organic mulch treatment.Surface treatment with organic material and chemical conditioning with bitumen and polyacrylamide had a positive influence on soil aggregation and therefore on water erosion control.Very high soil temperatures as compared to the other treatments were recorded for the soil with bitumen treatment when the solar radiation was high.Mulching and treating the soil surface with bitumen result in higher yields of cowpea and maize.     

北京市土壤侵蚀监测方法探讨

 为了科学定量评价北京市土壤侵蚀状况,通过北京市地面水土流失监测网络,开展水土流失定点观测,研究北京市土壤侵蚀监测的评价方法。结果表明：利用大量实测资料,基于美国通用土壤流失方程建立的北京土壤流失方程,可以作为北京市土壤侵蚀调查的模型工具;基T GIS和降雨侵蚀力模型的年度土壤侵蚀量推算方法,可作为从小区尺度转换到区域尺度的一种方法;由于网格法没有考虑水土保持措施因子,调查得到的土壤侵蚀量结果比采用抽样调查法得到的结果偏大。北京市土壤侵蚀监测方法的研究可为区域水土流失定量评价和动态监测提供借鉴作用。     

小流域水土流失治理优先度的评价与应用

中国水土流失防治任务仍然繁重,有计划分批次实施水土流失治理是现阶段条件下的必然选择,优先治理小流域识别是其首要解决的一项基础工作,然而目前相关成果较为缺乏,难以支撑小流域水土流失治理智能决策和精准施策。在当前大力推进智慧水土保持背景下,积极探索优先治理小流域识别方法非常迫切,对于科学、合理、高效促进水土流失治理工作具有重要意义。该研究立足于小流域自然禀赋条件,以中国水土流失重点区域——三峡库区秭归县为例,坚持科学性和可操作性相结合原则,以水土流失“减量和降级”双重目标和治理效益最大化需求为导向,综合水土流失面积和土壤侵蚀强度两个维度,提出小流域水土流失治理优先度定义及定量评价方法,为识别优先治理小流域提供科学依据和技术支撑。结果显示,秭归县2021年现状水土保持率为69.12%,远期（2050年）水土保持率为81.74%,总体提升12.62个百分点。秭归县2021年全域土壤侵蚀模数现状为758.50 t/(km²·a),最小可能土壤侵蚀模数为408.71 t/(km²·a),总体下降比例达46%。秭归县大部分区域均具有较大的水土保持率提升潜力和土壤侵蚀控制度,可完全治理和可降级的水土流失地块分布较为广泛,尤其在县域中西部的小流域存在较大的水土流失面积消减和土壤侵蚀强度降级空间。秭归县各小流域水土流失治理优先度的空间分布总体呈现中部高,东部和南部相对较低的分布格局,全县治理优先度大于0.6的小流域占总全县小流域的11.76%。通过典型县应用,该研究提出的小流域治理优先度涵盖了水土流失面积和土壤侵蚀强度两个维度,能更为全面满足小流域水土流失“减量和降级”双重目标和和治理效益最大化需求,直观反映了水土流失面积消减空间和土壤侵蚀强度降级空间的目标和相对大小,对支撑小流域治理决策更加准确、科学,治理优先度评价方法不仅可行,且易操作。     

基于RUSLE模型的青藏高原土壤保持功能定量评价

土壤保持功能是青藏高原生态系统的主要调节功能之一,准确评估青藏高原土壤保持功能的时空变化规律,是确保该地区顺利开展水土保持和生态环境治理工作的前提。本研究通过收集气象、土壤、土地利用、DEM和NDVI等数据,利用RUSLE模型对1982—2020年青藏高原土壤保持功能的时空特征进行动态评估。结果表明:1982—2020年青藏高原的土壤保持量呈波动增加趋势,土壤保持能力由南向北逐渐减弱,高值区主要集中在青藏高原东南部的川西和藏东的高山深谷;在过去的近40 a中,青藏高原土壤侵蚀强度发生明显转换,其主要特征是由高一级的中度侵蚀强度向低一级的轻度或微度侵蚀强度转换,说明青藏高原近40 a内土壤保持状况不断改善;不同地形条件下青藏高原土壤保持能力也有明显差异,主要表现为起伏度小的高海拔地区土壤保持能力普遍较弱;就不同的土地利用类型而言,林地区域的土壤保持能力最强,而未利用地土壤保持能力最弱。近40 a来,青藏高原土壤保持能力不断增强,但仍存在部分区域的土壤保持能力较弱。未来在重视和保护土壤保持能力较强的林地区域的同时,应加强起伏度小的高海拔地区水土治理工作,制定分级分区的土壤侵蚀防治措施,进一...     

Evolution of soil and water conservation in rain-fed areas of China

Rain-fed (dryland) farming is an ancient agricultural production system in China. It occurs widely across almost the whole country, especially in the Northwest and North China. The semi-arid Loess Plateau is the most important region of rain-fed farming in China, but unfortunately, soil erosion on the Loess Plateau area is the highest in China, and indeed amongst the highest in the world. This highlights the necessity for developing practices that can reduce soil and water erosion, improve soil water use efficiency, improve crop productivity, and reduce rural poverty in the region. Many techniques of soil and water conservation are being used in rain-fed areas of China, including such systems as mulch, ridge and furrow systems. The Appendix describes a unique system of soil and water conservation, called Shatian.Modern research on conservation tillage (No Till), although essential for reducing erosion, increasing crop productivity, and ameliorating poverty, is just beginning in China. Modern conservation tillage research started in the1990s' with support from Australia and other countries. The procedures, however, were modified to be in accord with local conditions and prevailing farmer experiences. With 10 years of experimentation, results show that the most successful conservation practice on the Western Loess Plateau is no till with stubble retention. This technique helps to conserve soil water, increases soil organic carbon, improves soil structure and water infiltration, reduces soil and water erosion, and improves crop productivity and sustainability of rain-fed farming systems. However, its adoption rate remains low due to barriers such as traditional attitude, insufficient rural extension, and so forth.     

上海市水力侵蚀现状与水土保持措施分析

为研究上海市水土流失及措施现状,以第一次全国水利普查水土保持情况普查结果为基础,结合上海市基本情况,分析上海市水力侵蚀现状和水土保持措施情况。结果表明,上海市水土流失面积超过了200km^2,水土流失以河道两岸和湖泊沿岸的坍塌淤浅为主要特征,建设项目施工造成的人为水土流失也是上海市水土流失的一个重要方面。上海市中心城区水土保持措施较完善,但郊区部分河道还没有采取有效护坡措施,基本处于自然状态,很容易发生水土流失;因此,河道边坡和湖泊岸线的护岸整治、海岸滩涂的保滩促淤治理是上海市水土保持工作的重点,同时还应加强建设项目的监管和水土保持监测,以防止人为水土流失。     

特定区域生产建设项目水土流失特征与防治技术管理

[目的]为了加强水土流失严重区,生态脆弱地区,水土流失重点预防和重点治理区,崩塌、滑坡危险区和泥石流易发区等特定区域生产建设项目水土保持的分类管理。[方法]通过对特定区域的水土流失特点及水土流失防治对策,结合有关水土保持法法律、法规和技术标准等拟定水土保持的分类管理要求。[结果]提出了特定区域生产建设项目水土流失防治技术要求。主要包括:提高水土流失防治标准和水土保持工程等级,严格控制地表扰动范围,最大限度减轻对区域水土流失影响等。[结论]不同区域生产建设项目水土流失防治应该执行特定的防治标准等级、防治工程设计标准等级和水土保持措施综合配置及相应的技术要求。     

桑树在紫色土水土保持效应方面研究

作为退耕还林的一种树种桑树在蚕业方面的经济效益有目共睹,而在水土保持方面的效益及应用研究较少,通过对玉米种植地、毛桑种植地和良桑种植地3个地块在8次降雨中的4次水土流失过程进行效益对比,分析侵蚀量、侵蚀时间与降雨因子的回归关系。结果表明:在4次降雨侵蚀过程中,毛桑区和良桑区的径流总量比玉米地块分别减少24.78%和37.83%,泥沙总流失量比玉米地块减少21.85%和33.55%;4次降雨过程中,3个地块的土壤养分流失依次是玉米地>毛桑区>良桑区,侵蚀量、侵蚀时间与降雨因子的回归关系均十分显著。     

漫川漫岗黑土区水土流失综合治理范式

漫川漫岗黑土区是我国东北商品粮主产区和黑土坡耕地最集中的地方,也是坡耕地水土流失最严重的地区。根据漫川漫岗黑土区水土流失规律和特点,在已有水土流失治理模式的基础上,通过总结该区水土流失综合调控机制,凝练基于粮食安全的黑土区长坡缓坡水土流失综合治理范式,并对形成的水土流失综合治理范式体系的结构进行解析,对其推广应用效益进行分析,以补充和完善黑土区水土流失综合调控理论。结果表明:1)漫川漫岗黑土区水土流失治理应以坡耕地水土流失控制为主,水土流失综合治理调控主要由地表径流调控、沟道侵蚀调控和土地生产力调控3部分构成;2)基于粮食安全的黑土区长坡缓坡水土流失综合治理范式,以生态安全保障和粮食安全保障2大体系为支撑,系统结构主要包括水土流失立体防护体系结构和生态农业技术体系结构及二者之间的耦合;3)该范式可为促进东北漫川漫岗黑土区生态、社会和经济更协调发展提供科学参考和实践样板。     

西南岩溶石漠化区水土流失现状与综合防治对策

以2005年在滇、黔、桂岩溶石漠化区科学考察活动取得的成果和近年来水土流失与石漠化的遥感解译资料为依据,分析西南岩溶石漠化地区的水土流失现状,揭示了西南岩溶石漠化地区水土流失问题的严重性与过程的特殊性。根据西南岩溶石漠化地区的生态环境特点与当前水土流失防治中存在的问题,提出了水土流失综合防治对策。     

Erosion modelling approach to simulate the effect of land management options on soil loss by considering catenary soil development and farmers perception

The prevention of soil erosion is one of the most essential requirements for sustainable agriculture in developing countries. In recent years it is widely recognized that more site‐specific approaches are needed to assess variations in erosion susceptibility in order to select the most suitable land management methods for individual hillslope sections. This study quantifies the influence of different land management methods on soil erosion by modelling soil loss for individual soil‐landscape units on a hillslope in Southern Uganda. The research combines a soil erosion modelling approach using the physically based Water Erosion Prediction Project (WEPP)‐model with catenary soil development along hillslopes. Additionally, farmers' perceptions of soil erosion and sedimentation are considered in a hillslope mapping approach. The detailed soil survey confirmed a well‐developed catenary soil sequence along the hillslope and the participatory hillslope mapping exercise proved that farmers can distinguish natural soil property changes using their local knowledge. WEPP‐model simulations show that differences in soil properties, related to the topography along the hillslope, have a significant impact on total soil loss. Shoulder and backslope positions with steeper slope gradients were most sensitive to changes in land management. Furthermore, soil conservation techniques such as residue management and contouring could reduce soil erosion by up to 70 percent on erosion‐sensitive slope sections compared to that under tillage practices presently used at the study site. The calibrated model may be used as a tool to provide quantitative information to farmers regarding more site‐specific land management options. Copyright © 2008 John Wiley & Sons, Ltd.     

Better land husbandry in Honduras: towards the new paradigm in conserving soil,water and productivity

Land shortages are forcing more smallholder farmers to cultivate tropical steeplands. Resulting accelerated soil erosion is being countered by the promotion of soil conservation (SC) technologies, such as cross‐slope barriers, which aim to reduce soil loss and preserve land productivity. However, farmer adoption rates tend to be low. This is often attributed to the farmers' conservatism or lack of education. Research in Honduras's steeplands demonstrates that farmers value SC, provided that it promotes agricultural production. Field research from 1995–98, involving farmed test plots on slopes greater than 35 per cent (19 degrees), demonstrates that at least one typical SC technology—live barriers of Vetiveria zizanioides (vetiver grass)—has little or no impact on maize yield. This means that farmers see little benefit from their investment in the SC method. They find that erratic rainfall, pests and diseases and a lack of economic resources are far greater threats to their livelihoods than soil erosion. Consequently, SC has a low priority. Keeping soil in place avoids major off‐farm disbenefits. However, the SC technique tested here made no discernible difference to slope foot sediment yields during the life of this study. In sum, a new approach is needed. Promoting ‘Better Land Husbandry’ strategies, which seek to combine farmers' concerns about productivity with conservationists' concerns about reducing soil erosion—often via cover‐management—seem to be the best way forward. Copyright © 2002 John Wiley & Sons, Ltd.