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1.
Wouter Lannoeye Cornelis Stal Etefa Guyassa Amanuel Zenebe Jan Nyssen Amaury Frankl 《自然地理学》2016,37(6):430-451
AbstractWith the recent technological advances offered by SfM-photogrammetry, we now have the possibility to study gully erosion at very high spatial and temporal scales from multi-temporal DEMs, and thus to enhance our understanding of both gully erosion processes and controls. Here, we examine gully degradation and aggradation at a gully headcut and at four re-incisions along a gully reach in Northern Ethiopia. Environmental controls recorded are topography rainfall, runoff, land use and cover, land management, and soil characteristics. The overall vulnerability of the catchment to erosion is low as calculated from the RUSLE (average 11.83 t ha?1 y?1). This reflects the successful land management of the past years. The runoff coefficient was on average 7.3% (maximum 18.2%). Runoff events caused most geomorphic change in the gully, but slumping of the gully bank also occurred on dry days. Most geomorphic change was caused by one major rainfall event of 54.8 mm d?1, and smaller runoff events caused both degradation and aggradation, often asynchronous between studied sites. Although most research focuses on gully heads alone, re-incisions at lower locations can still cause important gully degradation, which ultimately will reach the gully head and cause instability. 相似文献
2.
径流计算是区域径流量预报和水土资源评价模型中的重要组成部分。SCS-CN径流模型是一种常用的径流计算方法。径流曲线数（CN）是SCS-CN模型中反映降雨前流域特征的一个综合参数。用北京密云石匣3个小区实测降雨径流资料,用平均值法、中值法、算术平均值法、S对数频率分布法以及渐近线法来反推CN值,并用反推的CN值计算了径流深。用模型效率系数、相关系数和合格率比较了这5种方法确定的CN值计算径流深的优劣。结果表明：从模型有效系数来看,渐近线法得到的模型有效系数最好;从相关系数和合格率来看,算术平均值法的结果最好。相对于渐近线法来讲,算术平均值法计算CN简单,因此建议在计算CN值时用算术平均值法。 相似文献
3.
Runoff and infiltration were investigated on abandoned fields of patchy vegetation in semi-arid Spain during 15 months of natural rainfall and by rainfall simulations. The aim was to ascertain sources and sinks of runoff and the effects of soils and plant cover. Soils of the catena developed from mica schists of the upper hillslopes, fan deposits of the lower hillslopes, and an alluvial terrace at the bottom. Runoff from natural events were from three sets of three pairs each of 10 × 2 m runoff plots. The pairs of each set had different densities of plant cover; the sets were vegetated with tussock grass, Stipa tenacissima, a shrub, Anthyllis cytisoides, and a bush, Retama sphaerocarpa. Nineteen natural rainfall events of intensities up to 18 mm/h produced 400 mm of rain during the study period. Because the rainfall threshold for runoff production was about 20 mm, only eight events produced runoff. The rainfall simulations used a sprinkler that produced 50 mm/h of rain for 30 minutes; runoff was recorded each minute in 0.24 m2 bounded plots.The depth and structure of the soil mantle provide the main controls on runoff rates, which are lowest on the lower fan deposits and highest on the thin upslope soils. The river-bank terrace, with a surface covered by crusts and mosses, also yields relatively high runoff. In general, vegetation density varies inversely with runoff. Nevertheless, shrub and bush litter favor runoff, as does a particular spatial distribution of individual plants on the hillslope. Settling of the upper few centimeters of soils of the alluvial fan following cessation of cultivation 15 to 40 years ago has produced a near-surface compacted layer favoring shallow subsurface runoff. Apparently contradictory results between runoff plots and rainfall simulations are the result of differing processes. 相似文献
4.
Surface crusts and seals can form from a variety of processes, both physical and biological, and have the potential to alter runoff and erosion, especially in regions with low vegetation covers. Despite the obvious links between seals and crusts these features have rarely been considered together. This study uses rainfall simulation experiments to investigate interrill soil crust and seal development in response to structural (or raindrop-impact-induced) and depositional (or runoff-induced) processes on a semiarid piedmont in southern New Mexico, USA, which has undergone substantive vegetation change (replacement of grasses by shrubs) over the last 100 years. The study design incorporates six double-paired runoff plots divided into four subplots, each of which was exposed to three rainfall simulation events. Crust development on these plots was assessed using penetration-resistance measurements while seal development was assessed using runoff coefficients. The penetration-resistance data indicate that subplots directly exposed to raindrop impacts (uncovered plots) have crusts that are 40% stronger than those positioned beneath a mesh cover (covered plots) that intercepts the kinetic energy of the rainfall. The crusts exposed to raindrop-impacts increased in strength following each simulation, whereas the crusts on the covered surfaces reached a plateau after two events.Runoff data indicate that seal development does not directly mirror crust formation. Runoff coefficients increased after each rainfall simulation event but were not significantly different between the covered and uncovered plots. Rather, the presence of stone lags or litter on the soil surface influenced the relation between runoff and seal development. Sediment yields from uncovered surfaces exceeded those from covered surfaces, indicating that raindrop impacts contribute to the delivery of sediment into flows. The results of this study indicate that the loss of vegetation cover on the piedmont has increased the extent of surface crust and seal development but that those crusts may be playing an important role in mitigating erosion. 相似文献
5.
《Geomorphology》1997,18(2):61-75
In badland areas of the Ebro Basin, in a semiarid climate, two erosion plots (257 m2; 5° slope and 128 m2; 23° slope) on exposed Tertiary clays were monitored over two years (Nov. 1991–Nov. 1993). This material is characterized by high sodium absorption ratios which lead to high soil dispersivity. The dominant erosion processes in both plots are rilling and sheet erosion. Rainfall intensity was recorded at a weather station, connected to a data-logger, sediment production for single events was collected in tanks, and ground lowering was measured every six months by erosion pins and microtopographic profile gauge techniques. Significant runoff was produced only by rainfall events above 5 mm. Another threshold at 20 mm rain was noted. For rainfalls higher than 20 mm, the 23° slope plot shows a greater runoff response than the 5° one. Rainfall events exceeding this threshold showed a higher sediment production for the steeper slope. In the relationship between precipitation and sediment concentration, an envelope curve can be drawn indicating that any rainfall event of a given amount and intensity has a maximum sediment concentration which we speculate to be a function of the runoff sediment transport capacity. Runoff response and sediment yield in the studied plots are controlled by the rainfall and soil characteristics and their seasonal variations. In both plots, the erosion pins show that erosion rates in rill areas are 25–50% higher than in the interrill areas. Sediment yield recorded by collector devices was higher than the rates measured by erosion pins. The erosion rates based on rill cross-sections by profilometers were higher than the ones recorded by collectors. 相似文献
6.
Hugo A. Loiciga 《The Professional geographer》1997,49(3):356-364
Runoff and precipitation scaling with respect to drainage area is analyzed for large river basins of the world, those with mean annual runoff in excess of 10 k3/yr. The usefulness of the specific runoff (runoff per unit drainage area, m/yr) to categorize runoff scaling laws across the complete spectrum of climatic and hydrologic conditions is evaluated. It is found that (1) runoff scales with drainage are in those river basins with specific runoff in excess of 0.15 m/yr (r2 = 0.88); (2) runoff scaling with drainage area shows remarkably high statistical correlation (r2= 0.97) in river basins with specific runoff equal to or larger than 1.0 m/yr; (3) runoff does not Inc.rease with Inc.reasing drainage area in river basins with specific runoff below 0.15 m/yr, where no discernible statistical association was found between runoff and drainage area; and (4) precipitation depth (m/yr) is inversely proportional to drainage area raised to a fractional exponent in river basins with specific runoff in excess of 0.15 m/yr. 相似文献
7.
Modelling runoff and erosion for a semi-arid catchment using a multi-scale approach based on hydrological connectivity 总被引：1，自引：0，他引：1
Runoff and erosion processes are often non-linear and scale dependent, which complicate runoff and erosion modelling at the catchment scale. One of the reasons for scale dependency is the influence of sinks, i.e. areas of infiltration and sedimentation, which lower hydrological connectivity and decrease the area-specific runoff and sediment yield. The objective of our study was to model runoff and erosion for a semi-arid catchment using a multi-scale approach based on hydrological connectivity. We simulated runoff and sediment dynamics at the catchment scale with the LAPSUS model and included plot and hillslope scale features that influenced hydrological connectivity. The semi-arid Carcavo catchment in Southeast Spain was selected as the study area, where vegetation patches and agricultural terraces are the relevant sinks at the plot and hillslope scales, respectively. We elaborated the infiltration module to integrate these runoff sinks, by adapting the parameters runoff threshold and runoff coefficient, which were derived from a rainfall simulation database. The results showed that the spatial distribution of vegetation patches and agricultural terraces largely determined hydrological connectivity at the catchment scale. Runoff and sediment yield for the scenario without agricultural terraces were, respectively, a factor four and nine higher compared to the current situation. Distributed hydrological and erosion models should therefore take account of relevant sinks at finer scales in order to correctly simulate runoff and erosion-sedimentation patterns. 相似文献
8.
The method of time series is applied to analyze the variation of precipitation and temperature from 1961 to 2002 in the mountainous areas of the Tarim River Basin, as well as water consumption in the headstream and mainstream areas. Those hydrologic parameters are verified. Quantitative results indicate that the precipitation and temperature in the headstream areas have an increasing trend to different extent. The increasing trend of precipitation is less significant than that of the temperature (α= 0.05). Runoff of three headstreams also increases especially from 1994 to 2002. Compared with the perennial runoff, the annual runoff has increased by 25.163×108 m3/a. However, inflows of the mainstream areas has only increased by 0.9985×108 m3/a. So the runoff at the different hydrologic stations in the headstream areas has a linear decreasing trend. It is shown that the degraded trend of eco-environment of the Tarim River Basin hardly changes in the special water period for ten consecutive years. Given runoff of three headstreams is accounted in normal period from 1957 to 2003, the annual runoff of the headstream areas would be only 22.57×108 m3. Therefore, more attention should be given to ecological safety of the Tarim River Basin. 相似文献
9.
In the Mediterranean area, forest fires have become a first-order environmental problem. Increased fire frequency progressively reduces ecosystem recovery periods. The fire season, usually followed by torrential rains in autumn, intensifies erosion processes and increases desertification risk. In this work, the effect of repeated experimental fires on soil response to water erosion is studied in the Permanent Field Station of La Concordia, Valencia, Spain. In nine 80 m2 plots (20 m long × 4 m wide), all runoff and sediment produced were measured after each rainfall event. In 1995, two fire treatments with the addition of different biomass amounts were applied. Three plots were burned with high fire intensity, three with moderate intensity, and three were unburned to be used as control. In 2003, the plots with the fire treatments were burned again with low fire intensities. During the 8-year interval between fires, plots remained undisturbed, allowing regeneration of the vegetation–soil system. Results obtained during the first 5 months after both fire experiments show the high vulnerability of the soil to erosion after a repeated fire. For the burned plots, runoff rates increased three times more than those of 1995, and soil losses increased almost twice. The highest sediment yield (514 g m− 2) was measured in 2003, in the plots of the moderate fire intensity treatment, which yielded only 231 g m− 2 of sediment during the corresponding period in 1995. Runoff yield from the control plots did not show significant temporal changes, while soil losses decreased from 5 g m− 2 in the first post-fire period to 0.7 g m− 2 in the second one. 相似文献
10.
未来气候变化对淮河流域径流深的影响 总被引：19，自引：2，他引：17
本文运用多元回归方法,建立有关气候-径流深的数学模型,并用该模型预测在未来气候变化的15种可能情景下淮河三个代表子流域径流深的变化。结果表明:年径流深随年降水量的增加而增加,随年均温度的升高而减少;不同流域对各种气候变化的响应存在着明显的差异,反映出整个淮河流域不同自然地理条件的影响;不同季节的径流深对各种气候变化的响应也存在明显的差异,体现了季风气候对径流的影响。文章还特别关注了暖干天气组合下径流深的变化,提出这种极端气候情景对工农业生产和国民经济建设有着严重的负面影响 相似文献
11.
北京地区径流曲线数模型中的径流曲线数 总被引：10，自引：0，他引：10
径流曲线数模型(SCS-CN模型)是国内外最受欢迎的地表径流评价方法,该模型只需综合参数--径流曲线数(CN),该参数反映降雨前流域的地表和土壤特征。本文的目的是确定北京地区径流曲线数模型中的径流曲线数。研究采用了北京密云、延庆、门头沟64个坡面径流小区的降雨径流资料,用算术平均值法计算出小区径流曲线数值,用定水头法测定了北京主要土壤类型和土地利用类型的饱和导水率,用经验公式确定出64个坡面径流小区的饱和导水率值,并根据饱和导水率确定了北京地区和坡面径流小区的水文土壤组类型,得到了北京不同水文土壤组、土地利用下的径流曲线数数据库。结果表明:北京地区主要水文土壤组为B类;土地利用、水土保持措施、植被盖度和前期土壤湿度等对径流曲线数有显著影响;根据北京径流小区径流资料得到的径流曲线数值比美国土壤保持局查算表提供的数值要大。本研究结果可为该区域的地表水资源量评价以及土地利用管理提供服务。 相似文献
12.
The Climate and Hydrology of the Upper Blue Nile River 总被引：2，自引：0，他引：2
DECLAN CONWAY 《The Geographical journal》2000,166(1):49-62
The Upper Blue Nile river basin is the largest in Ethiopia in terms of volume of discharge, second largest in terms of area, and contributes over 50 per cent of the long-term river flow of the Main Nile. This paper provides a review of the nature and variability of the climate and hydrology in the source region of the Blue Nile-the central Ethiopian Highlands. Annual rainfall over the basin decreases from the south-west (>2000 mm) to the north-east (around 1000 mm), with about 70 per cent occurring between June and September. A basin-wide time series of annual rainfall constructed from 11 gauges for the period 1900 to 1998 has a mean of 1421millimetres, minimum in 1913 (1148 mm) and maximum in 1903 (1757 mm). Rainfall over the basin showed a marked decrease between the mid-1960s and the late 1980s and dry years show a degree of association with low values of the Southern Oscillation Index (Sol). The October to February dry season in 1997/98 was the wettest on record and responsible for widespread flooding across Ethiopia and also parts of Somalia and Kenya. Available river flow records, which are sparse and of limited duration, are presented for the Blue Nile and its tributaries upstream of the border with Sudan. Runoff over the basin amounts to 45.9 cubic kilometres (equivalent to 1456 m3 s−1 ) discharge, or 261 millimetre depth (1961–1990), a runoff ratio of 18 per cent. Between 1900 and 1997 annual river flow has ranged from 20.6 cubic kilometres (1913) to 79.0 cubic kilometres (1909), and the lowest decade-mean flow was 37.9 cubic kilometres from 1978 to 1987. Annual river flow, like rainfall, shows a strong association with the SOI 相似文献
13.
The natural landscapes of semiarid areas worldwide comprise a series of scattered patches of shrubs within a matrix of biologically crusted soils (BSC). As BSCs are considered ecosystem engineers the relationships between the BSC and the shrub patches determine system functioning. The objective of our study was to investigate long-term effects of agricultural practices on biological soil crusts and their influence on hydrological aspects of a semiarid ecosystem. During 1991, we experimentally simulated five of the area's agricultural practices; 1) Scraping – the topsoil was removed to a depth of 2 cm, 2) Spraying – phototrophic organisms were chemically killed with herbicide, 3) Mowing – perennial vegetation was cut and spread to simulate grazing practices, 4) Car track – a heavy roller was used to simulate car-tracks, 5) Control – undisturbed natural plots. Sixteen years later, in 2007, these agricultural practices were found to have a long-term effect on the crusted soil surface and the related soil-surface properties. Mowing and car-track treatments led to decreased overland runoff and increased hydraulic conductivity, whereas scraping and spraying treatments led to increased overland runoff production and decreased hydraulic conductivity. We conclude that the practices had a long-term residual impact on BSC succession and related soil surface properties, which affected the hydrological processes and system functioning. 相似文献
14.
Mark R. Jury 《自然地理学》2016,37(2):120-131
This study explores the structure and modulation of the mean diurnal climate of Africa with a focus on satellite rainfall. Solar heating over tropical mountains and land-sea temperature gradients initiate moisture convergence in the afternoon-evening. The diurnal temperature range is from 5 °C along the coast to 20 °C in arid zones with low vegetation fraction. NCEP2 reanalysis reveals the diurnal circulation via continental-scale drainage and seabreeze flows. Factors modulating the diurnal cycle vary across four sub-regions: South Africa, East Congo, Ethiopia, and Guinea. In the Congo and Guinea coast the surface moisture and heat fluxes are important, while in South Africa convective available potential energy and vertical motion are influential. Ethiopia’s evening orographic convection is out of phase with surface fluxes. The diurnal residual calculated from NCEP2 fields exhibits a 2 km depth for thermal gradients and 200 km inland penetration of onshore flow by evening. 相似文献
15.
XU Jing-Ji YANG Cong LIU Chang-Meng SONG Xian-Fang HU Shan-Shan LI Fa-Dong TANG Chang-Yuan 《地理学报》2009,30(4):461-470
Simulated rainfall is a valid tool to examine the runoff generation on the slope.13 simulated rainfall experiments with different rainfall intensities and durations are completed in a 5 m ×10 m experimental plot in mountainous area of North China.Simultaneously,rainfall,surface runoff,soil-layer flow,mantel-layer flow and soil moisture are monitored respectively.From the results,it is found that the hydrographs in all layers have the characteristics of rapid rise and fall.The recessions of surface flow and soil-layer flow are much faster than that of mantel-layer flow.Surface flow,the main contributor,makes up more than 60% of the total runoff in the study area.It even exceeds 90% in the cases of high intensity rainfall events.Runoff coefficient(ratio of total runoff to rainfall amount) is mainly influenced by rainfall amount,rainfall intensity and antecedent soil moisture,and the relationship can be well expressed by a multiple linear regression function α = 0.002P + 0.182i + 4.88Wa-0.821.The relation between the rainfall intensity and the lag time of three flows(surface runoff,soil-layer flow and mantel-layer flow) is shown to be exponential.Then,the result also shows that the recession constant is 0.75 for surface runoff,is 0.94 for soil-layer and mantel-layer flow in this area.In this study area,the dominant infiltration excess runoff is simulated by Horton model.About 0.10 mm/min percolation is observed under the condition of different rainfall intensities,therefore the value is regarded as the steady infiltration rate of the study area. 相似文献
16.
塔里木河流域水资源变化的特点与趋势 总被引：1，自引：1，他引：0
The Tarim RiverBasin islocated in NorthwestChina,which is known in the world forits rich natural resources and fragile eco-environment.W ater resource rational distribution and highly effective utilization isthe key pointsto solve the severe eco-environm … 相似文献
17.
黄河中游流域环境要素对水沙变异的影响 总被引：15，自引：7，他引：15
目前 ,黄河中游地区流域的水沙变化主要以水文法和水保法研究为主。由于黄河中游具有明显的自然地带性分布特征 ,流域系统的水沙过程受到环境要素的综合影响。本文根据黄河中游河口镇至龙门区间已控一级支流的测站资料 ,采用地理环境要素法分析水沙变异及成因。研究表明 ,河龙区间流域径流量和输沙量与地理环境因子的影响密切相关。 2 0世纪 70年代以来 ,降雨减水减沙作用不断减小 ,随着水土保持措施的提高 ,人类活动减水减沙所占比重不断增大。 70年代与 80年代气候波动和人类活动影响的平均减水减沙作用分别为5 3 4 %、 2 8 6 %和 4 6 6 %、 71 4 %。 相似文献
18.
全球气候变化对贵州省径流模数的潜在影响 总被引：1，自引：0，他引：1
揭示全球气候变化对贵州省径流模数潜在影响可为该区优化配置水资源、确定水土保持治理的重点区域以及减少由降雨季节性分布不均引发旱涝灾害提供依据。该文以贵州省22个主要气象和水文站的降雨和径流等资料为基础,建立降雨和径流之间的统计关系。采用DELTA方法,根据HadCM3模型对A2情景(人口快速增长、经济发展缓慢)和B2情景(强调社会技术创新)下输出的不同时期的降雨量以及实测的贵州省降雨量和径流模数资料,推算出贵州省2006-2035年、2036-2065年和2066-2095年前后两个时期之间径流模数的增减量;研究结果为:A2和B2情景下未来3个时期径流模数逐渐增大,相对于基准期1961-1990年最大增幅分别达17.52%和10.58%。不同情景和不同时期径流模数变化的空间分布差异较大,A2情景下径流模数的变化比B2情景下更为剧烈。在贵州省石漠化严重的地区,当径流增加较多时,不仅需要考虑水资源的充分合理利用,还需兼顾防止水土流失的加剧。 相似文献
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20.
The semiarid loess area in north Shaanxi Province is one of the most serious areas of water erosion in China. The Chinese government initiated the project “Grain-for-Green” for soil erosion control in 1999, with significant effect. Vegetation, rainfall, soil, and topography are the most dominant natural factors affecting soil erosion; therefore, the aim of this research was to investigate the effects of these four factors on runoff and soil loss at the runoff-plot scale over five years and use the Gray relational analysis methods to compare the impacts of these factors. Five runoff-measuring sites were established in five different vegetation types. The results show that the relative impacts of the four factors on runoff were: rainfall > soil > topography > vegetation, and the relative impacts of the factors on sediment yield were soil > runoff > rainfall > topography > vegetation. We also analyzed the weights of these four factors on runoff and sediment yield during the wettest year alone. For that year, the relative weights of the factors on runoff were topography > rainfall > soil > vegetation, and the relative weights of the factors on sediment yield were runoff > soil > rainfall > topography > vegetation. 相似文献