黄土高原土壤养分的损失

The soil nutrient losses due to excessive soil loss on Loess Plateau were studied by means of runoff plots and systematical determination of soil nutrients both in sediments and runoff.The results show that the amounts of nutrient losses depended on the amounts of ersoion sediments.Along with sediment,11-197kg nitrogen/hectare and 9-174kg phosphorus/hectare were lost,accounting for 92.46-99.47 percent of the total amount of nitrogen loss and 99.85-99.99 percent of the total amount of phosphorus loss respectively.The nutrient losses,very small in runoff,were mainly attributed to erosion of a few rainstorms during a year.The nutrient level in sediment was mostly higher than that in the original soil.Planting grass evidently redued the losses of soil nutrients.The N level was lower in runoff than in rainfall so that the N loss from runoff could be made up by rainfall.Fertilizer application to crops raised the nutrient level in runoff.     

中国黄土高原丘陵沟壑区天然降雨下不同土地利用方式的水土流失效应（英文）

The Loess Plateau,which is located in the arid and semi-arid areas of China,experiences significant soil erosion due to intense human activities and soil erodibility.It is necessary to explore and identify the land-use types or land-use patterns that can control soil erosion and achieve certain agricultural production capabilities.This study established runoff plots with two slope gradients(5°and 15°) in north of Yan'an,one area of the Loess Plateau,with 3 single land-use types(cultivated land,CL;switchgrass,SG;and abandoned land,AL) and 2 composite land-use types(CL-SG and CL-AL).Prom 2006 to 2012,we continuously monitored the rainfall characteristics,runoff depth,soil loss,vegetation coverage,and soil physical properties.The results indicated a general trend in the number of runoff and soil loss events for the 5 land-use types:CL = CL-SG CL-AL SG AL.The general trend for runoff depth,soil loss,their magnitudes of variation,and the slopes of rainfall-runoff regression equation was CL CL-SG CL-AL SG AL,whereas the rainfall threshold for runoff generation exhibited the opposite trend.Results of nonparametric test regarding runoff depth/EI_(30) and soil loss/EI_(30),where EI_(30) is the product of rainfall kinetic energy and the maximum rainfall intensity over 30 min,and the runoff depth-soil loss relationship regression indicated that the effect of CL-AL was similar to that of SG;SG was similar to AL;and CL-AL,SG,and AL were superior to CL with regard to soil and water conservation.Runoff depth and soil loss significantly increased as the slope gradient increased.Runoff depth and soil loss were significantly correlated with the soil particle size composition and bulk density,respectively.The strongest significant correlations were found between runoff depth and vegetation coverage as well as between soil loss and vegetation coverage,which showed that vegetation coverage was the primary factor controlling soil erosion.Therefore,the composite land-use type CL-AL and the artificial grassland(SG) are appropriate options because both soil conservation and a certain degree of agricultural production are necessary in the study area.     

中国亚热带丘陵地区典型流域的营养元素释放

Agriculture is still the biggest contributor of non-point source(NPS) pollution to water bodies and runoff discharges of nutrients and other chemicals are one of the most importtant pathways.This study was conducted during 1998-1999 in a typical watershed with complex agriculture and forestry systems as well as dotted farmer villages,in a transitional region between the mid-and northern subtropical zones of China.Continuous sampling of stream water was performed regularly at a weekly frequency,with additional sampling after all major rainfall events.The discharges of N and P nutrients and suspended materials were measured and the total and area-averaged annual discharges of all components were calculated .The results showed an uneven seasonal distribution of nutrient discharges with summer storms contributing most to the total fluxes.This study demonstrated a high dependence of runoff vlume on rainfall but the overall runoff coefficients were dependent on land use type and watershed size.The area-averaed annual discharges varied greatly among the sub-watershed with differnt sizes and land use structures.This is the first study estimating the area-averaged annual discharges of N and P in the hilly areas of subtropical china,which were 1.5gm^-2 a-1 and 0.1gm^-2a^-1,respectively.providing important reference values for the assessment of regional agricultural non-point source pollution.     

三峡库区坡耕地磷素流失特征分析

Eutrophication in the Three Gorges Reservoir has become a serious issue, and phosphorus (P) is the nutrient thought to be primarily responsible although there are few studies about P loss from the mostly sloping farmlands of the area. This work investigated the amounts and forms of P loss from 9 farmlands with the slopes of 4°, 9°, and 17° in a small watershed, Wangjiagou in Fuling District, Chongqing of China. The slope of the relationship between runoff and rainfall increased with field slope; i.e., there was a significant interaction between the effects of rainfall and field slope on water export. For sediment export by surface runoff, there was no interaction between field slope and rainfall, and the intercept of the relationship between rainfall and sediment loss was significantly different for the 3 slopes. The main P loss was from sediments, regardless of slope. In the runoff water, particulate P was the largest P fraction, and its loss was greatest from the steepest land and least from the flattest. The release of total P and available P from sediments followed the same trend. The P loss during May to July in Wangjiagou was more than 60% of the annual total.     

Water Budget Analysis of Red Soils in Central JiangxiProvince, China

The daily soil water budgets in the red soil areas of central Jiangxi Province, southern China, were investigatedwith a large-scale weighing lysimeter and runoff plots. From 1998 to 2000, peanuts (Arachis hypogaea L.) and rape(Brassica napus L.) were planted in the lysimeter and in 1999, peanuts were planted in the runoff plots. The soil waterbudget components including rainfall, runoff, percolation and evapotranspirat.ion were measured directly or calculated by Richards‘ equation and water balance equation. The results showed that most rainfall, including rainstorms, occurredfrom March to July, and induced the greatest soil water percolation during the year. The evapotranspiration was stilllarge from July to September when rainfall was ininimal. Thus, the lack of synchronization in soil water inputs and losseswas disadvantageous to crops growing in this region. Among the soil water losses, percolation was the largest, followed byevapotranspiration, and then soil runoff. Runoff was very small on farmland with crops. It was significantly different, fromthe uncultivated uplands where large-scale runoff was usually reported. The soil water storage fluctuated sinusoidally,with a large amplitude in the rainy season and a small amplitude in the dry season.     

大型蒸渗仪和径流小区中红壤的水量平衡

The daily soil water budgets in the red soil areas of central Jiangxi Province, southern China, were investigated with a large-scale weighing lysimeter and runoff plots. From 1998 to 2000, peanuts (Arachis hypogaea L.) and rape (Brassica napus L.) were planted in the lysimeter and in 1999, peanuts were planted in the runoff plots. The soil water budget components including rainfall, runoff, percolation and evapotranspiration were measured directly or calculated by Richards' equation and water balance equation. The results showed that most rainfall, including rainstorms, occurred from March to July, and induced the greatest soil water percolation during the year. The evapotranspiration was still large from July to September when rainfall was minimal. Thus, the lack of synchronization in soil water inputs and losses was disadvantageous to crops growing in this region. Among the soil water losses, percolation was the largest, followed by evapotranspiration, and then soil runoff. Runoff was very small on farmland with crops. It was significantly different from the uncultivated uplands where large-scale runoff was usually reported. The soil water storage fluctuated sinusoidally, with a large amplitude in the rainy season and a small amplitude in the dry season.     

伊朗西北部半干旱农田径流模型的建立

Transformation of rainfall into runoff over an area is a very complex process which exhibits both temporal and spatial variability;runoff in a defined area can be affected by factors such as topography, vegetation, rainfall characteristics and soil properties. This study was conducted to develop an empirical model using the rainfall characteristics and soil properties for predicting runoff from dry-farming lands in a semi-arid agricultural area in Hashtroud, Northwest Iran. Runoff plots(1.83 m × 22.1 m) in triplicate were installed in thirty-six sloped dry-farming lands in the study area. Runoff under natural rainfalls was measured in each plot during a2-year period. The results showed that runoff for 41 runoff-producing rainstorm events with duration longer than 30 min was largely associated with a rainfall index obtained by multiplying the positive square root of rainfall depth(h0.5) by the logarithm of the maximum 30-minute intensity(LogI30)(R2= 0.81). Runoff significantly varied among the plots(P 0.001), which was considerably related to the effective soil properties(R2= 0.74), i.e., soil permeability(Per) and aggregate stability(AS). A multiple linear regression model was developed between runoff and the rainfall index(h0.5logI30) and the effective soil properties(AS and Per). Evaluation of the model using 34 runoff-producing rainstorm events that occurred during the next two years resulted in high values of the efficiency coefficient and R2(0.88 and 0.91, respectively), which revealed that the model developed in this study could be used in predicting runoff from the dry-farming lands in the semi-arid regions.     

Streamflow and Soil Moisture of Agroforestry and GrassWatersheds in Hilly Area

A study was conducted in a hilly area of Sichuan Province, Southwestern China, to compare the streamflow and soilmoisture in two upland watersheds with different land use patterns. One was an agroforestry watershed, which consistedmainly of trees with alder (Alnus cremastogyne Burkill) and cypress (Cupressus funebris Endl.) planted in belts or stripswith a coverage of about 46%, and the other was a grassland primarily composed of lalang grass (Imperata cylindricavar. major (Nees) C.E.Hubb.), filamentary clematis (Clematis filamentosa Dunn) and common eulaliopsis (Eulaliopsisbinata (Retz.) C. E. Hubb) with a coverage of about 440/o. Streamflow measurement with a hydrograph established atthe watershed outlet showed that the average annual streamflow per 100 mm rainfall from 1983 to 1992 was 0.36 and1.08 L s^-1 km^-2 for the agroforestry watershed and the grass watershed, respectively. This showed that the streamflowof the agroforestry watershed was reduced by 67% when compared to that of the grass watershed. The peak averagemonthly streamflow in the agroforestry watershed was over 5 times lower than that of the grass watershed and lagged byone month. In addition, the peak streamfiow during a typical rainfall event of 38.3 mm in August 1986 was 37% lowerin the agroforestry watershed than in the grass watershed. Results of the moisture contents of the soil samples from 3slope locations (upper, middle and lower slopes) indicated that the agroforestry watershed maintained generally highersoil moisture contents than the grass watershed within 0-20 and 20-80 cm soil depths for the upper slope, especially forthe period from May through July. For the other (middle and lower) slopes, soil moisture contents within 20-80 cm depthin the agroforestry watershed was generally lower than those in the grass watershed, particularly in September, revealingthat water consumption by trees took place mainly below the plow layer. Therefore, agroforestry land use types mightoffer a complimentary model for tree-annual crop water utilization.     

湿润速率和粘粒含量对红壤沟间侵蚀的影响

An aggregate stability test and a simulated rainfall test were conducted on four representative Ultisols from southeastern China. The soils selected, with clay contents ranging between 117 and 580 g kg-1 , were derived from shale and Quaternary red clay. The stability of aggregates (2–5 mm in diameter) obtained from the soil samples were determined by the Le Bissonnais method. For determination of infiltration, runoff, and erosion, the soil samples were packed in 30 cm × 60 cm trays, wetted at rates of 2, 10, and 60 mm h-1 , and then exposed to simulated rainfall at 60 mm h-1 for 1 h. The results indicated that both aggregate stability and slaking caused by fast wetting increased with increasing clay content. The effect of wetting rate (WR) on infiltration and seal formation varied with clay contents. In the soil with low clay content (sandy loam), the infiltration rate was affected slightly by WR due to low aggregate stability and slaking. In the soils with medium clay content (silt clay loam and clay), WR affected infiltration significantly due to the high aggregate slaking force. In the soil with high clay content, the effect of WR on infiltration was significant, but not as evident as in the soils with medium clay content, which may be related to high aggregate stability by wetting partially compensating for slaking force. The effect of WR on soil loss was similar to that of runoff, but more pronounced. The findings from this study indicated that the relationship between wetting rate and clay content should be considered when predicting interrill erosion in Ultisols.     

四川丘陵区农林系统和农草系统流域的径流和土壤水分特征

A study was conducted in a hilly area of Sichuan Province, Southwestern China, to compare the streamflow and soil moisture in two upland watersheds with different land use patterns. One was an agroforestry watershed, which consisted mainly of trees with alder (Alnus cremastogyne Burkill) and cypress (Cupressus funebris Endl.) planted in belts or strips with a coverage of about 46%, and the other was a grassland primarily composed of lalang grass (Imperata cylindrica var. major (Nees) C. E. Hubb.), filamentary clematis (Clematis filamentosa Dunn) and common eulaliopsis (Eulaliopsis binata (Retz.) C. E. Hubb) with a coverage of about 44%. Streamflow measurement with a hydrograph established at the watershed outlet showed that the average annual streamflow per 100 mm rainfall from 1983 to 1992 was 0.36 and 1.08 L s^-1 km^-2 for the agroforestry watershed and the grass watershed, respectively. This showed that the streamflow of the agroforestry watershed was reduced by 67% when compared to that of the grass watershed. The peak average monthly streamflow in the agroforestry watershed was over 5 times lower than that of the grass watershed and lagged by one month. In addition, the peak streamflow during a typical rainfall event of 38.3 mm in August 1986 was 37% lower in the agroforestry watershed than in the grass watershed. Results of the moisture contents of the soil samples from 3 slope locations (upper, middle and lower slopes) indicated that the agroforestry watershed maintained generally higher soil moisture contents than the grass watershed within 0-20 and 20-80 cm soil depths for the upper slope, especially for the period from May through July. For the other (middle and lower) slopes, soil moisture contents within 20-80 cm depth in the agroforestry watershed was generally lower than those in the grass watershed, particularly in September, revealing that water consumption by trees took place mainly below the plow layer. Therefore, agroforestry land use types might offer a complimentary model for tree-annual crop water utilization.     

径流曲线法在黄土区小流域地表径流预测中的初步应用

径流曲线法是目前国际上预测无径流观测资料地区降水地表产流的主要模型,由于气候、水文及下垫面的差异,在黄土高原地区的应用受到限制。利用黄土高原地区3个小流域的303场降雨径流资料,针对黄土高原降雨地表径流特点优化模型中的初损率λ,并提出降雨强度修正函数,将降雨强度因子引入径流曲线法。优化后的模型效率E达到0．812,实测径流深与预测径流深的线性回归决定系数R2达到0．822。改进后的SCS．CN模型可用于黄土区小流域降雨地表产流预报,对黄土高原无资料地区侵蚀产流预报、指导水土保持工程配置和设计具有重要的理论和工程实践意义。     

黄土高原北部水蚀风蚀交错区产流条件及径流系数

为了揭示黄土高原北部水蚀风蚀交错区的产流机制并推求径流系数,为该地区地表水资源的深入研究提供基础数据,选取具有黄土高原北部水蚀风蚀交错区典型气象与水文特征的六道沟流域为研究区。通过分析实测水文数据,从机制上分别研究了试验流域在表层土壤（5—10 cm）达到饱和及不饱和条件下的产流过程,在长历时低强度降雨条件下,产流的必要条件是表层土壤达到饱和且雨强≥0.12 mm/min;在短历时高强度降雨条件下,表层土壤未达到饱和状态时,产流的必要条件是降雨强度≥0.52 mm/min;径流系数与平均降雨强度之间存在着显著的正相关关系;以运动波理论的基础方程式结合GIS技术开发了适用于试验流域的分布式降雨—径流数值模型,模型的误差<3%;基于2005—2009年（5 a）的降雨—径流数值计算,得到试验流域在这5 a的平均径流系数为0.11,从而推求出多年平均径流系数为0.10～0.15。     

基于SCS模型的新疆博尔塔拉河流域径流模拟

为探索SCS(soil conservation service)模型在干旱区地表径流模拟中的适用性,以新疆博尔塔拉河上游温泉流域为例,利用2013年融雪期18场次降雨量、日径流量及卫星同步观测基础数据,基于度日模型、土壤水分吸收平衡原理及地表温度-植被指数特征空间反演土壤水分等方法,探索适用于流域尺度耦合降雨、积雪融水混合补给径流的SCS模型参数改进算法,采用国产"高分一号"16m分辨率遥感影像和landsat8 OLI 30m多光谱遥影像为模型提供面状数据。分别利用参数算法改进后SCS模型与原SCS模型进行径流模拟,前者模拟值较后者更接近实测值,二者模型验证期Nash效率系数分别为0.66和0.38,相对误差系数分别17%,27%;研究结果表明,利用遥感反演地表参数,结合土壤饱和含水量计算SCS模型参数的方法在面积大且数据缺乏的温泉流域具有可行性和实用性。     

基于前期雨量和降雨历时的SCS-CN模型改进

径流曲线法（Soil Conservation Service Curve Number，SCS-CN）对前期产流条件（Antecedent Moisture Condition，AMC）的概化，导致径流预测出现相应的突然跳跃，同时还忽略了降雨历时作为重要组成部分对地表径流的影响，影响了模型径流预测的精度。密云水库是北京市地表饮用水的重要来源，对其上游流域进行降雨径流预测有着重要的生态意义和经济意义。该研究将SCS-CN模型与前期雨量和降雨历时结合，采用API（Antecedent-Precipitation Index，前期降雨指数）模拟土壤前期水分条件，并且提出了一种考虑次降雨事件中土壤前期雨量和土壤入渗量的静态渗透方程，对SCS-CN模型进行了改进。其中，潜在最大蓄水等于前期土壤水分和土壤潜在蓄水量的和，最大静态渗透速度是流域土壤水分达到蓄满时的静态渗透速度，静态渗透系数是与土壤结构、土地利用等相关的无量纲。利用2006-2010年及2014-2020年石匣流域径流小区的200次降雨径流事件监测结果，对新改进的模型与原SCS-CN模型以及两种改进的SCS-CN模型进行了校准、验证和性能比较。结果表明，4种径流模型中，该研究改进的模型表现最好，纳什效率系数为0.77，决定系数为0.79，均方根误差为3.21 mm，相比于SCS-CN模型纳什效率系数、决定系数和均方根误差分别提高了319%、97.5%和107.5%。参数敏感性分析表明，潜在最大蓄水和静态渗透系数是最敏感的两个参数，最大静态渗透速度的参数敏感性一般，初损率的参数敏感性最差。该研究改进模型在密云水库上游潮白河流域降雨径流模拟中具有一定的适用性，可为其他地区产流计算提供参考依据。     

不同坡度黄土微地形条件下SCS-CN模型参数研究

基于自然降雨数据研究径流曲线数（SCS-CN）模型参数难以排除坡度的干扰,从而影响模型计算径流量的精度。为了准确探究黄土微地形条件下不同坡度（5°,15°,25°）对模型的初损率（λ）和径流曲线系数（CN）的影响及其变化规律,从而为后续SCS-CN模型参数研究提供科学依据和优化径流预测模型。通过开展人工降雨试验（90 mm/h雨强、人工掏挖耕作）,探究黄土微地形不同坡度下SCS-CN模型的λ值和CN值。结果表明5°坡度下,λ=0.2,CN=75.58时模拟效果最佳;15°坡度下,λ=0.15,CN=77.28时模拟效果最佳;25°坡度下,λ=0.1,CN=72.91时模型的模拟效果最佳。λ=0.2这一标准参数值不能满足不同坡度条件下的径流模拟,且随着坡度增加呈现显著的递减趋势。     

Research on the SCS-CN initial abstraction ratio using rainfall-runoff event analysis in the Three Gorges Area,China

The Soil Conservation Service Curve Number (SCS-CN) method is widely used for predicting direct runoff from rainfall. The ratio of initial abstraction (Ia) to maximum potential retention (S) was assumed in its original development to be equal to 0.2 in SCS-CN method. The constant initial abstraction ratio is the most ambiguous assumption and requires considerable refinement. The objectives of this study were (1) to determine the initial abstraction ratio, in an experimental watershed in the Three Gorges Area of China, by analyzing measured rainfall-runoff events; (2) to compare the performance of the traditional and modified Ia/S values with observed rainfall-runoff data. The dataset consisted of 6 years of rainfall and runoff measurements from the experimental watershed. The results indicated that the Ia/S values, using event rainfall-runoff data, varied from 0.010 to 0.154, with a median of 0.048. The average initial abstraction ratio of the watershed was equal to 0.053. The standard SCS-CN method underestimates large runoff events, yielded a slope of the regression line of 0.559 and an intercept of 0.301. The modified Ia/S value was about 0.05 that better predicted runoff depths with an R² of 0.804 and a linear regression slope of 0.834. It also improved model efficiency coefficient (E) to 0.768 compared with 0.482 for traditional Ia/S value. This Ia/S-adjusted SCS-CN method appears to be better appropriate for runoff prediction in the Three Gorges Area of China.     

岔巴沟流域汛期径流模拟及地表产流特征分析

气候变化是影响流域水文循环过程的重要驱动因素,近年来,气候变化导致极端降雨—径流事件的频繁发生对人类社会经济发展构成了严重的威胁。因此,迫切需要开展流域水文模拟和产流特征分析。土壤和水评估工具(SWAT)是一种具有物理机制的分布式水文模型,已被广泛用于评价变化环境下的水文过程。以黄土高原岔巴沟流域为研究区,通过利用与黄土高原地区产流模式更为接近的Green-Ampt下渗法驱动SWAT模型模拟了岔巴沟流域日尺度的水文过程,并以水文响应单元为分析对象,结合4个降雨—径流事件的地表产流量和地表径流系数分析了降雨强度和前期土壤含水量对不同土地覆被产流特征的影响。结果表明：(1)基于Green-Ampt下渗法驱动的SWAT模型率定期和验证期E_NS为0.76,0.74,R²为0.78,0.75,模型能够较好地模拟日尺度流域水文过程;(2)流域不同土地覆被下地表径流系数随最大雨强的增加呈显著上升趋势,且最大降雨强度大于16 mm/h后地表径流系数显著增加,当土地覆被为耕地时降雨转化为地表径流的比例最大,其次为草地和林地;(3)前期土壤含水量的大小可以揭示大...     

密云水库上游流域径流曲线模型的参数修订

为探讨同时率定CN值和初损率2个参数得到的模拟结果是否比单独率定一个参数更为理想,且在不同土地利用类型下SCS-CN模型是否均适用,选取了密云水库上游石匣小流域为研究区域,根据石匣小流域坡面试验小区2006—2010年实测降雨-径流数据和SCS-CN模型的计算公式,在0.05~0.40范围内,等间隔选取8个不同的初损率值,并利用算术平均值法反推各初损率值条件下对应的CN值,以纳什效率系数为SCS-CN模型的适用性评价参数,确定裸地、耕地、草地和林地4种不同土地利用类型下模拟效果最佳的CN值与初损率,最后对4种不同土地利用类型下的SCS-CN模型进行了适用性评价。结果表明:(1)4种不同土地利用类型条件下,当初损率为0.05时纳什效率系数值最高,分别为裸地(0.75)、耕地(0.48)、草地(-1.11)、林地(-0.24);(2)在石匣小流域内利用SCS-CN模型对该研究区域的径流值进行预测时,裸地条件下的CN1值为86,耕地条件下的CN1值为74,草地条件下的CN1值为58,林地条件下的CN1值为63,4种不同土地利用类型的初损率取值均为0.05;(3)通过同时率定2个参数可以使得SCS-CN模型的模拟效果得到一定的提高;(4)在石匣小流域内,SCS-CN模型在裸地和耕地条件下可以较好地模拟地表径流,但草地和林地条件下其模拟结果不理想。     

基于混合产流模式的黄土高原流域水沙过程耦合模拟

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流域次降雨侵蚀产沙的BP神经网络模拟

在分析黄土高原韭园沟流域多年观测资料的基础上,应用BP神经网络建模方法,建立了流域次降雨侵蚀产沙的神经网络模型。通过输入模型变量流域次降雨量、平均降雨强度、径流深和洪峰流量模数,对流域次降雨侵蚀产沙量进行了训练和预测。预测结果表明,所建BP神经网络模型预测精度较高,可近似揭示复杂非线性流域次降雨侵蚀产沙系统的产沙规律,为建立较高预报精度的黄土高原流域次降雨侵蚀产沙预报模型提供了依据。