To identify the key parameters and develop accurate experimental models of detachment and transport, splash detachment and transport of loess soil were investigated in relation to the rainfall characteristics and slope. The experiment was conducted under 25 combinations of five rainfall intensities (60, 84, 108, 132 and 156 mm h−1) and five slope gradients (0°, 5°, 10°, 15° and 20°), using a custom splash pan. Raindrop characteristics (diameter, velocity and kinetics) and splash mass were measured in downslope and upslope. The results indicated that rainfall intensity and slope contributed 94.77% and 0.46%, respectively, to the detachment rate, and 24.39% and 67.82%, respectively, to the transport rate. From a holistic viewpoint, the positive effect of slope became more visible on the detachment rate when the rainfall intensity exceeded 108 mm h−1, and on the transport rate when the slope exceeded 15°. Based on the rainfall simulator in this study, the rainfall kinetic energy (KE, J), raindrop median particle size (D50, mm) and raindrop terminal velocity (V, m s−1) all increased with increasing rainfall intensity (I) within the 60~108 mm h−1 range but decreased with increasing rainfall intensity within the 132~156 mm h−1 range. The rainfall intensity and raindrop characteristics (D50/V/KE) are the key parameters of splash detachment (Dr, g·m−2 min−1), and three detachment models were developed: (1) Dr = 0.1153 I1.09D500.79 (R2 = 0.99, NSE = 0.98, p < 0.01); (2) Dr = 0.0162 I1.11V1.22 (R2 = 0.99, NSE = 0.99, p < 0.01); and (3) Dr = 0.0813 I1.10KE0.18 (R2 = 0.99, NSE = 0.99, p < 0.01). The rainfall intensity and slope are the key parameters for splash transport (Tr, g·m−2 min−1), and the developed transport models could be expressed as: (1) Tr = 0.00657 I1.343S0.116 (R2 = 0.914, NSE = 0.874, p < 0.01) (slopes of 0°, 5° and 10°) and (2) Tr = 0.00218 I1.165S1.033 (R2 = 0.986, NSE = 0.986, p < 0.01) (slopes of 15° and 20°). The results of this study could enhance the understanding of soil splash detachment and transport on loess slopes.

Effective soil particle size composition can more realistically reflect the particle size sorting process of erosion. To reveal the individual contributions of rainfall intensity and slope to splash erosion, and to distinguish the enrichment ratio of each size and the critical size in splash, loessial soil collected on the Loess Plateau in May 2019 was tested under different rainfall intensities (60, 84, 108, 132, 156 mm h−1) and slopes (0°, 5°, 10°, 15°, 20°). The results demonstrated that 99

It is important to study the mechanisms associated with the spatial distribution of soil water and salt to control soil salinization and promote the sustainable development of farmland. Six plots in a slight farmland with different spatial locations were selected to determine the spatial distribution of soil water and salt and their correlation using the multifractal method. Each plot was applied using the grid method (15 m × 15 m, 3600 m2), where each sampling site was located at the center point coordinates. The 0–20 and 20–40 cm soil layers were sampled.The spatial variability of the soil water and salt were 1.41 and 1.73 fold higher in the upstream farmland than in the downstream farmland. The spatial variability of the soil water and salt was significantly correlated. In addition, the spatial variability of the soil water and salt significantly correlated in the 0–20 and 20–40 cm layers. The spatial distribution of both soil water and salt in the entire soil layer had similar characteristics at this sampling scale. Our results provide a theoretical basis to study the interactive mechanisms associated with the distribution of soil water and salt.

Biocrusts play a critical role in prevention of erosion, but little is known on the relationship between biocrust cover and raindrop detachment capacity at the slope scale. Evaluating the raindrop detachment capacity on biocrusted slope is essential for better knowledge of the rainfall-induced erosion of biocrusted slope. Thus, laboratory simulated rainfall experiments were conducted on plots (140 x 120 cm) representing moss-dominated biocrusted slopes to measure the amounts of raindrop detachment under a complete combination of different biocrust cover (0%, 20%, 40%, 50%, 60%, and 80%) and rainfall intensities (42, 60, 90, 120, and 150 mm h-1) at 26.79% slope gradient with two replications. The results showed that the biocrust cover, rainfall intensity, and their interaction all significantly affected the raindrop detachment modulus (RDm). The RDm in biocrust plot was significantly lower than in bare soil plot under rain events with the same rainfall intensities. The lower biocrust cover or the larger rainfall intensities led to higher RDm. Reduction benefit of raindrop detachment modulus (RB-RDm) were greater than its corresponding biocrust cover values. When the biocrust cover increased from 20% to 40%, the increase range and growth trend of RDm decreased with increasing rainfall intensity. Our results indicated that the development of biocrusts on slope is an effective way of reducing raindrop detachment by protecting soil in their covered area and increasing flow depth. When moss-dominated biocrust cover reached 40%, the raindrop detachment capacity effectively weakened even under rain events with large rainfall in-tensities. These findings may conducive to offer a scientific guidance for soil erosion control in the Loess Plateau and in other arid and semiarid regions.

The rate of soil detachment by water flow indicates soil erosion intensity directly. The exact relation between soil detachment rate and actual sediment load in water flow, however, is still unclear, and the existing relationships have not been adequately tested. The aims of the present study were to investigate the response of soil detachment rate to sediment load using rill flume data with loessial soil and to quantitatively examine the soil detachment equations in the WEPP and EUROSEM soil erosion models. Six slopes were combined with seven flow discharges to measure detachment rates under seven sediment loads using a rill flume with a soil-feeding hopper. Significant differences were found among the soil detachment rate by different sediment loads in low sediment load levels, but an insensitive response of soil detachment rate to sediment load was found under high levels of sediment load. The soil detachment rate was proved to be negatively linearly correlated with sediment load. The rill detachment equation in the WEPP model predicted the soil detachment rate by rill flow very well under our experiment condition. The soil detachment equation in the EUROSEM model underestimated the detachment rates under controlled conditions, but removing the setting velocity from the equation greatly improved prediction. Further experiments that could reflect the dynamic convective detachment and deposition process need to be conducted to compare with the present examination results and to further understand rill erosion processes.

The influences and quantifications of soil crust traits on the infiltration, hydrodynamic of runoff, and erosion rate of sheet erosion under the combined effects of raindrop impact and sheet flow scouring need further study. Loessial soil from the Loess Plateau was tested to produce different antecedent crusts under simulated rainfall intensities (0.5, 1.0, 1.5, 2.0, and 2.5 mm/min, typical storm intensity in the area), and then the effects of antecedent crusts on sheet erosion processes were quantified at a rainfall intensity of 1.5 mm/min. The results showed that the bulk density and hardness of antecedent crusts were higher than those of soil. Particle sizes of crusts were smaller than those of soil at light rain intensity but larger under heavy rain intensity. The bulk density, hardness, and particle size D 50 of the antecedent crust were all positively correlated with rainfall intensity, being well described by linear equations ( R 2 > 0.87), while the thickness was negatively linearly correlated with rainfall intensity ( R 2 = 0.88). Although the existence of antecedent crusts could decrease the infiltration and increase the runoff, resulting in the high flow velocity and stream power, antecedent crusts could still effectively reduce sheet erosion. The reductions in the average infiltration rate and average erosion rate and the increases of average flow velocity and stream power all increased with the increment of bulk density of antecedent crust. Relationships could be all well described by linear positive correlations ( R 2 > 0.79). When the bulk density of crust was enhanced by 27∼29%, the flow velocity and stream power could be increased by 8∼29% and 15∼70%, and the sheet erosion could be reduced by 61∼73%. The existence of crust could effectively reduce sheet erosion. These results could help understand the mechanism of the erosion process in the presence of physical crusts.

Water shortage and soil salinization in gully farmland comprising sediment deposited farmland (SF) and excavated farmland (EF) have become a widespread concern in the loess hilly region. A two-year field experiment was conducted to assess the soil water content (SWC) and salt content (SSC) and their effect on the spring maize yield and water use efficiency in SF and EF. Eight treatments comprising flat cropping without mulching (1), ridge planting without mulching (2), ridge planting with plastic mulching (3), and ridge planting with straw mulching (4) were tested in the SF and EF plots, respectively. The results showed that the yield was higher in SF than EF, whereas the water use efficiency was significantly higher in EF because the bottom water flux was 117.4% higher in SF than EF (P < 0.01). A significant positive correlation was found between the average SWC and yield (P < 0.01), thereby indicating that the yield was severely limited by the SWC. Thus, the higher water use efficiency in EF has important implications for alleviating water scarcity during agricultural production in this region. The risk of soil salinization was decreased greatly by treatment 3 where the SSC was decreased in EF and SF were 0.09 g kg–1 and 0.08 g kg–1, respectively. In addition, treatment 3 had the most significant impacts on the yield and water use efficiency. Our study provided appropriate land type and effective tillage measure for the sustainable development in dryland agricultural areas.

The variations in hydrodynamic parameters at different polysaccharides rates and the relationships between sheet erosion modulus and hydrodynamic parameters were analyzed to reveal the hydrodynamic mechanism of sheet erosion on loessial slopes. Artificially simulated rainfall experiments were carried out under three slope gradients (10°, 15°, and 20°), three rainfall intensities (1.0, 1.5, and 2.0 mm·min−1), and four dry-spreading rates of polysaccharides (0, 1, 3, and 5 g·m−2). The results showed that (1) four hydrodynamic parameters (flow velocity, shear stress, stream power, and unit stream power) all increased with both rainfall intensities and slope gradients at four rates of polysaccharides. (2) Polysaccharides could effectively reduce hydrodynamic parameters. In contrast to the bare slope, the average flow velocity, shear stress, stream power, and unit stream power diminished by 27.11 41.18

Understanding sheet erosion processes and improving estimates of soil erosion on bio-logical soil crustal (biocrustal) slopes requires a deep understanding of the factors influ-encing sheet erosion and its detachment-and transport-limited processes. Simulated rainfall experiments were conducted on plots of biocrust to simultaneously measure the rates of splash detachment and sheet erosion with 0%, 20%, 40%, 50%, 60%, and 80% of coverage at 90 mm h-1 rainfall intensity and 15 degrees slope. The splash detachment rate decreased rapidly during the first 5 min of rainfall and stabilised as rainfall continued, while the sheet erosion rate increased gradually and eventually became relatively stable. The rates of splash detachment and sheet erosion decreased substantially as biocrusts coverage increased and average values of them can be effectively weakened when bio-crusts coverage increased from 20% to 40%. Transport-limited processes, dynamic equi-libria between detachment-and transport-limited processes, and detachment-limited processes all occurred on biocrustal slope within the same rainfall event. The mean duration of transport-limited processes was longer (16.3 min vs. 9.1 min) when bare slopes were covered by biocrusts, and the latest change in the time from transport-limited to detachment-limited processes appeared at 40% biocrusts coverage. The existence of bio-crusts could effectively affect the sheet erosion and its detachment-and transport-limited processes, especially when the coverage was close to 40%. These results can improve our understanding of impacts of biocrusts on sheet erosion processes, and aid an effective way of reducing sheet erosion in arid and semiarid regions.(c) 2022 IAgrE. Published by Elsevier Ltd. All rights reserved.

天然高分子多肽衍生物Jag C162是一种新型高聚物,研究其对黄土坡面径流过程的影响可为土壤侵蚀的化学调控技术提供新的理论依据.通过室内人工模拟降雨试验,在不同坡度(10°,15°,20°)、降雨强度(1,1.5,2 mm/min)、Jag C162不同撒施剂量(0,1,3,5 g/m2)的组合条件下,研究了 Jag C162对坡面径流过程的调控效应.结果表明:(1)撒施中(3 g/m2)、小剂量(1 g/m2)Jag C162的初始产流时间相对裸坡显著滞后(p＜0.05),大剂量(5 g/m2)的初始产流时间则显著提前(p＜0.05).(2)不同剂量Jag C162的坡面径流率随径流过程的变化大致趋势为由快速增长逐渐趋于缓慢递增状态.不同剂量Jag C162径流率的大小顺序为:裸土＞1 g/m2＞5 g/m2＞3 g/m2.(3)Jag C162会显著改善＞0.25 mm 土壤水稳性团聚体含量,显著提高各粒级土壤水稳性团聚体的含量(p＜0.05),尤以1～2,2～5,＞5 mm粒径的团聚体含量的提高幅度大.因此,Jag C162可显著改善土壤团聚体结构,提高土壤入渗性能,减少地表径流量,从而减弱侵蚀发生的径流动力,达到调控土壤侵蚀的目的.

Abstract: Long-term soil salt accumulation could lead to salinization. Aimed to prevent soil salinization, we investigated soil salt dynamics, its interface with the groundwater table, rainfalls duration and the impact periods when salt is mostly accumulated. Total soil salt accumulation and dynamic distribution were monitored in the 0–80 cm layer in alluvial farmland from 2018 to 2020. We found soil salt contents increased by 0.15 g kg–1 and 0.07 g kg–1 in the 0–40 and 40–80 cm soil layers, respectively, which indicated that soil salinization occurred. We defined the rainstorm impact period (RIP) as period when soil salt dynamic distribution was affected by rainstorm event. The salinity time-trend during RIP was sequentially characterized by a first salt leaching, followed by a rapid and then slow salt accumulation, which took the first 4 days, from day 4 to 10, and then beyond, respectively. In the first leaching stage, salt migration content was determined by rainfall (P < 0.05) which could leach 41.5% of salt on average in the whole soil layer. In the rapid accumulation stage, lots of salt accumulated due to high evapotranspiration and shallow groundwater table. In the slow accumulation stage, salt accumulation rate was inhibited by deeper groundwater table. In addition, the total accumulated soil salt in the whole soil layer increased by 0.14 g kg–1 in the RIPs, which comprised only 14.5% of the overall study period, but the value accounted for 63.6% of the salt accumulation, thereby indicating that RIPs were the main periods when salt accumulated during the soil salinization process. Our results provided insights into soil salt dynamic distribution during RIPs, thereby facilitating the effective prevention and control of soil salinization.

Soil salinization is widespread and it hinders agricultural development in the loess hilly region of China. In this study, we determined the dynamic distribution of the soil salinity (SS) as well as its effects on maize (Zea mays L.) after rainstorm events in two land types produced by excavation and sediment deposition. Four treatments were tested comprising sediment deposited farmland without plastic mulch (S1) and with plastic mulch (S2), and excavated farmland without plastic mulch (E1) and with plastic mulch (E2). The results showed that the dynamic distribution of the SS exhibited similar characteristics included leaching, rapid accumulation, and relatively stability in the 0-40 cm soil layer after rainstorm events. A turning point where the leaching and accumulation of SS reached a balance in the 0-40 cm layer occurred on about the 4th day under the no plastic mulch treatments and on the 6th day under the plastic mulch treatments. The SS reached a relatively stable condition in the whole soil layer on the 12th day. Rainstorm events increased the accumulated SS by 0.36, 0.08, 0.44, and 0.20 g kg-1 under E1, E2, S1, and S2, respectively, during the year. Plastic mulch treatments decreased the average accumulated SS by 66.7% and the average SS by 22% by reducing water infiltration and soil evaporation. The average SS and accumulated SS in sediment deposited farmland were 8.9% and 47.6% higher, respectively, than those in excavated farmland because of the lower depth of the groundwater influence zone and more abundant capillary pores in the sediment deposited farmland. The average SS in the whole soil layer followed the order of: S1 (0.72 g kg-1) E1 (0.62 g kg-1) > E2 (0.53 g kg-1) > S2 (0.52 g kg-1) (P < 0.05), and these levels did not limit maize growth. However, the two land types without plastic mulch would be transformed into severe saline-alkali land after 10 years. Therefore, we conclude that E2 is the optimal treatment for this region because it resulted in the lowest accumulated SS. Our results are important for understanding the SS dynamics and controlling soil salinization after rainstorm events.

Sheet erosion has been the major erosion process on steep grassland since the Grain-for-Green project was implemented in 1999 in the Loess Plateau with serious soil erosion in China. Quantifying sheet erosion rate on steep grassland could provide scientific support for effectively controlling soil erosion and rationally managing grassland. Simulated rainfall experiments were conducted on grassland plot with vegetation coverage of 40% under complete combination of rainfall intensities of 0.7, 1.0, 1.5, 2.0 and 2.5 mm min(-1)and slope gradients of 7 degrees, 10 degrees, 15 degrees, 20 degrees and 25 degrees. Results showed that sheet erosion rate, varying from 0.0048 to 0.0578 kg m(-2) min(-1), was well described by binary power function equation (SE = 0.0026I(1.306)S(0.662)) containing rainfall intensity and slope gradient withR(2) = 0.940. The logarithmic equation of shear stress (SE = 0.084 + Ln (tau)) and the power function equation of stream power (SE = 1.141 & x277;(1.073)) could be used to predict sheet erosion rate. Stream power (R-2 = 0.903) was a better predictor of sheet erosion than shear stress (R-2 = 0.882). The stream power was an excellent hydrodynamic parameter for predicting sheet erosion rate. The study results can reveal the mechanism of sheet erosion process.

针对黄土丘陵区治沟造地新造地发展农业生产缺水的问题,提出适宜新造地的田间高效用水技术体系,包括田间雨水高效利用和排洪渠雨水存蓄利用两个部分.计算得出了丰水年玉米的灌溉需水量为460.5 mm/亩、平水年615.2 mm/亩、枯水年705.5 mm/亩;丰水年马铃薯的灌溉需水量为314.3 mm/亩、平水年346.2 mm/亩、枯水年364.8 mm/亩.提出了地下暗管输水、滴灌、垄沟种植、覆盖等技术的应用参数.制定了玉米和马铃薯在滴灌、喷灌和地下暗管输水条件下的灌溉制度,能为治沟造地新造地田间高效用水管理提供参考.

Determining the soil moisture content (SMC) distribution is indispensable for field management, especially in arid and semiarid regions. Effective parameters can contribute to the optimization of SMC models for accurate SMC prediction. Therefore, in this study, the relationships between the SMC and multifractal parameters (D-2, D-v, D-s, A(v), and F-v denote the correlation dimension, property of small probability and large probability, spectrum width, and symmetry of spectrum shape, respectively) of the soil particle size distribution (PSD) were explored in the hilly loess region of China. A grid method was adopted (20 m x 20 m, total = 384 points) to sample the SMC in the 0-40 cm and 40-80 cm soil layers on the second, eighth, and twelfth days after the first rainfall, which were defined as the early sampling (ES), medium sampling (MS), and late sampling (LS), respectively. We found that the variation in the SMC explained by the multifractal parameters increased as SMC decreased, where they accounted for 40.07% and 75.75% of the SMC in the 0-40 cm and 40-80 cm soil layers in LS, respectively. The variation in the SMC in the 0-40 cm explained by the multifractal parameters was lower than that in the 40-80 cm soil layer in all sampling stages. The equations fitted for the whole soil layer were significant in all sampling stages (P < 0.01). A(v) (31.95%) and D-v (13.59%) had negative correlations with SMC, and their relative importance values with respect to SMC were high in all sampling stages (P < 0.05). SMC at higher values had a positive correlation with F-v, whereas SMC at lower values had a significant positive correlation with D-2 and negative correlation with D-s, and these two parameters in the MS and LS stages explained more than 75% of the variation in the SMC in the 40-80 cm soil layer. These results suggest that the characteristics of the soil PSD can be described in detail by the multifractal parameters, which can directly reflect the SMC. Thus, we conclude that SMC is closely related to the multifractal parameters of the PSD (A(v), D-v, D-s, D-2, and F-v) and it can be applied to optimize SMC models.

The loess region of China is one of the most heavily eroded areas in the world. Soil detachment capacity by rill flow (D-c) is a key parameter for quantifying intensity of rill erosion in many process-based erosion models. However, only a limited number of studies have been devoted to soil detachment capacity for the various types of loess soil such as is found on the Loess Plateau, where there is variation from south to north and in terms of soil particle size composition. The objectives of this study were (1) to discriminate differences in soil detachment capacity by rill flow (D-c) among five loess soils, (2) to investigate the relationship between D-c and hydrodynamic parameters, and the relationship between D-c and soil properties, and (3) to establish an equation to model soil detachment capacity by rill flow for the loess region. Soil detachment capacity by rill flow for five typical loess soils found on the Loess Plateau of China was investigated through a flume experiment by varying five flow discharges and five slope gradients. The results show that D-c of SM sandy loess is the largest with a mean of 2.2145 kg m(-2) s(-1), followed by YL clay loess, DB sandy loess, AS loess, and CW loess. Stream power is the best hydrodynamic parameter to describe the dynamic process of soil detachment capacity by rill flow for these five loess soils. Soil detachment capacity by rill flow was negatively correlated with soil cohesion and effective silt content (P < 0.05), while it was positively correlated with effective median soil particle size (P < 0.01) and effective sand content (P < 0.05). Soil detachment capacity by rill flow for various hydraulic and soil conditions in the loess region could be modeled using a quaternary power function of slope gradient, flow discharge, soil cohesion and effective median particle size (NSE = 0.96), or it could be modeled by a ternary power function which calculates the variation of soil detachment capacity with stream power, soil cohesion and effective median size (NSE = 0.96). The results of this study reveal the mechanism of soil detachment by rill flow and advance development of a physically-based rill erosion model. Future research should focus on the impact of effective particle size on D-c to ensure a full understanding of soil erosion processes.

Sheet erosion has been the major erosion process on steep grassland since the Grain-for-Green project was implemented in 1999 in the Loess Plateau with serious soil erosion, in China. Quantifying sheet erosion rate on steep grassland could improve soil erosion estimation on loess hillslopes and provide scientific support for effectively controlling soil erosion and rationally managing grassland. Simulated rainfall experiments were conducted on grassland plot with vegetation coverage of 40% under complete combination of rainfall intensities of 0.7, 1.0, 1.5, 2.0 and 2.5 mm min-1 and slope gradients of 7°, 10°, 15°, 20° and 25°. Results showed that sheet erosion rate (SE), varying from 0.0048 to 0.0578 kg m-2 min-1, was well described by binary power function equation (SE = 0.0026 I1.306S0.662) containing rainfall intensity and slope gradient with R2 = 0.940. The logarithmic equation of shear stress (SE = 0.084 + Ln (τ)) and the power function equation of stream power (SE = 1.141 ɷ1.073) could be used to predict sheet erosion rate. Stream power (R2 = 0.903) was a better predictor of sheet erosion than shear stress (R2 = 0.882). However, predictions based on flow velocity, unit stream power, and unit energy were unsatisfactory. The stream power was an excellent hydrodynamic parameter for predicting sheet erosion rate. The sheet erosion process of grassland slope was also affected by the raindrop impact except the dynamic action of sheet flow. The combination of stream power and rainfall kinetic energy (KE) among different rainfall physical parameters had the most closely relationship with the sheet erosion rates, which is also better than the stream power only, and a binary power function equation (SE = 0.221 ω0.831KE0.416) could be used to predict sheet erosion rate on grassland slope with R2 = 0.930. The study results revealed the dynamic mechanism of the sheet erosion process on steep grassland in the loess region of China.

天然聚合衍生物(NPD)是一种新型的高分子聚合物,是坡面土壤侵蚀化学调控措施所采用的一种新型材料,通过室内人工模拟降雨试验,以裸坡为对照,研究了不同NPD施加措施(撒施和喷施)及不同施加量(1.0,3.0,5.0g/m2)条件下径流流速特征以及对侵蚀产沙的影响.结果表明:(1)施加NPD的坡面径流流速随降雨历时的变化与裸坡一致,均呈先增大后逐渐趋于稳定的趋势,且流速随降雨历时的变化过程可用对数方程描述.撒施在1.0 mm/min雨强下,延迟降雨初始产流时间8～19 min,而喷施在3个雨强下,初始产流的时间整体上较裸坡提前1～2 min;(2)与裸坡相比,施加NPD具有显著减小流速的效应,且雨强越大,减小流速的效应越差;施加不同剂量NPD减缓坡面径流流速的效益范围13.2％～54.3％.其中撒施3 g/m2剂量和喷施5 g/m2剂量对坡面径流流速的减小效应相对较好;(3)与裸坡相比,施加NPD具有显著的减沙效应,且减沙效应范围为30.6％～71.2％.无论是撒施还是喷施,整体表现为5 g/m2计量的减沙效应最好.(4)裸土坡面的侵蚀模数对平均流速的响应关系与撒施和喷施NPD坡面的侵蚀模数对平均流速的响应关系皆可用对数方程表示,且撒施和喷施对流速的减小作用均大于减沙作用.

Splash erosion is recognized as an important process of water erosion on agricultural land, but evaluating and modelling splash detachment capacity on steep slopes using loessial soil were not fully studied. The objectives of this study are: (1) to evaluate the effects of slope gradient (S) and rainfall intensity (I) on splash detachment capacity (SDr), (2) to select the key rainfall physical parameters and hydraulic parameters affecting splash detachment capacity, (3) to establish new and more accurate experimental models between splash detachment capacity (SDr) and these key parameters on steep slopes for loess regions. The experiment was conducted at slopes of 12.23%, 17.63%, 26.8%, 36.4%, 40.4% and 46.63% under rainfall intensities of 48, 60, 90, 120, 138 and 150 mm h(-1) , respectively, using simulated rainfall. Results showed that the equation between splash detachment capacity (SDr) with both parameters of rainfall intensity (I) and slope gradient (S) (i.e. SDr = 0.000126 In (0.36S(-0.3)I(1.3) - 14)) could predict SDr well with R-2 = 0.85 and Nash-Sutcliffe model efficiency (NSE) = 0.71. SDr was more sensitive to rainfall intensity than to slope gradient. The rainfall kinetic energy (KE) was the key rainfall physical parameter and the mean flow depth (h) was the key hydraulic parameter affecting SDr. The equation between SDr with both parameters of KE and h (i.e. SDr = 0.000164 In (0.0031KE(1.13) h(-0.3) - 4.5)) could satisfactorily predict SDr with R-2 = 0.85 and Nash-Sutcliffe model efficiency (NSE) = 0.81. The new equations (i.e. SDr = 0.000126 ln (0.36S(-0.3)I(1.3) - 14) and SDr = 0.000164 In (0.0031KE(1.13)h(-0.3) - 4.5)) could help in controlling water erosion in the loess region of China.

阻力系数是坡面流水动力学参数之一,是反映坡面流水力学特性的重要特征值。通过室内人工模拟降雨试验,研究了不同雨强（0.7,1.0,1.5,2.0,2.5mm/min）和坡度（7°,10°,15°,20°,25°）下,黄土区草地坡面片流阻力系数随雨强和坡度的变化特征。结果表明:（1）不同雨强和坡度下,草地坡面片流阻力系数随降雨历时的变化均呈先波动减小,后逐渐趋于稳定的趋势,且变化过程均可用二次多项式进行描述,相关性显著,决定系数0.5以上。（2）草地坡面片流阻力系数随雨强的增加而逐渐增大,可用指数方程描述,决定系数0.8以上;而片流阻力系数随坡度的增加而减小,可用对数方程描述,决定系数0.6以上。（3）草地坡面次降雨平均片流阻力系数对雨强及坡度的综合响应关系可用二元指数函数描述,决定系数0.923,且雨强对草地坡面片流平均阻力系数的影响大于坡度对阻力系数的影响。研究结果为草地坡面水流动力学特性及草地植被的阻流机制提供参考和理论基础,对于深刻认识黄土区草地坡面侵蚀动力和生态建设具有重要意义。