Accuracy of two sampling methods used to estimate sediment concentrations in runoff from soil-loss plots

The use of a bottle sampler and a soil pipette to quickly and accurately sample soil-water mixtures of known sediment concentrations was tested. Both devices failed to sample adequately soil-water mixtures containing 1–187 gl^?1 of solid particles. Poor sampling ability was attributed to rapid settlement of larger particles and to innate deficiencies in the sediment trapping ability of the samplers. These sampling devices should not be used to estimate sediment loads in runoff from soil-loss plots, and erosion data from plot studies which have used a sediment sampling procedure should be treated with caution.     

Observations of contemporary arroyo cutting near Santa Fe,New Mexico,U.S.A.

Arroyo cutting that began in the American Southwest in the 1880s is associated with sudden runoff, a circumstance characteristic of this semiarid region in which occasional intense rainfall exceeds the capacity of the ground to absorb water. This report describes two arroyos in an area of moderately dissected bolson deposits southwest of Santa Fe, Cañada de la Cueva and Pueblo Cañon, where arroyo cutting since 1970 has been closely related to runoff from summer rain. The area is vegetated chiefly by grama grass and scattered juniper. Cutting is monitored by repeated surveys of channel floors, cross-sections, and headcuts, and by repeated photographs taken as stereopairs. Rainfall and discharge are measured simultaneously in 5-minute intervals by dual digital recorders at a gauging station on Cañada de la Cueva (drainage area 4.64 km²). Discharge has been as much as 18.2 m³/s from rainfall of 25.2 mm. The maximum 15-minute intensity for this storm was 64.0 mm/hr, and runoff was 7.9 mm. The flood peak arrived in 20 minutes, by which time 80 per cent of the rain had fallen, and the flow subsided to a tenth of its maximum in less than an hour. This storm at Pueblo Cañon (drainage area 13.3 km² above the place of measurement) resulted in an estimated discharge of 140 m³/s, and features produced by hail on the channel floor suggest that the duration of flow could have been as brief as 30 minutes. Observed increments of headward cutting at Cañada de la Cueva range from 0.28 m for 1.8 mm of runoff to 4.9 m for 12 mm of runoff. Aggregate cutting in 5 years has been as much as 13.7 m, resulting in erosion of 570 m³ of alluvium. Headward cutting near the mouth of Pueblo Cañon has been observed in increments of 10.3, 14.6, and 20.7 m, for an aggregate of 45.6 m, as measured from 1971 to 1974. This cutting removed 1,770 m³ of alluvium.     

黄河流域代表水文站径流和降水量变化的初步分析

通过对1995—1990年共36a黄河上游和中游两个代表站径流量和区域降水量资料的季节和年际变化趋势的分析，初步揭示了黄河不同流域降水量和径流量之间的关系，发现虽然黄河上游区域平均降水量距平的变化在夏季和秋季呈下降趋势，但代表黄河上游的兰州水文站径流量在夏季和秋季却呈现出明显的上升变化趋势，而黄河中游区域平均降水量距平的变化在夏季和秋季呈下降趋势，代表黄河中游的花园口水文站径流量在夏季和秋季也呈现出明显的下降变化趋势。因此，在比较长时间的气候趋势上，黄河中游地区径流量异常与降水量异常变化趋势是一致的，降水量异常是影响径流量异常的主要因子。而在黄河上游地区径流量异常与降水量异常变化趋势并不一致，降水量减少的同时径流量却增加，这可能与伴随着降水量减少的全球增暖所引起的高原冰川和积雪融化等因素有关。因此，影响黄河上游径流量的因素除了降水等自然因子外，其它因子诸如上游的径流量、人类活动、全球增暖等也同样会影响黄河上游的径流量。     

Effects of the Herbicide Metazachlor on Phytoplankton and Periphyton Communities in Outdoor Mesocosms

The effects of the chloroacetanilide herbicide metazachlor have been investigated in outdoor artificial mesocosms. Decreasing phytoplankton densities were caused by the application, however, the communities recovered after 30 to 35 days. Periphyton growth was found to be affected not only by the herbicide application but by the presence of species with different ability to grow on artificial substrates. Zooplankton diversity was small due to low density of ingestible algae species. Oxygen saturation was found to be correlated with the dosage levels of the herbicide in the second half of the study.     

Hydrologic conditions responsible for triggering the Sto e landslide, Slovenia

In two events, on November 15 and 17, 2000, near the Mangart Mountain (2679 m a.s.l.), NW Slovenia, two translational landslides (debris flow slides) with a total volume of more than 1.5 million m³ occurred on the Sto e slope composed of morainic material filled with silt fraction. The first landslide was associated with a dry and the second landslide with a wet debris-flow, respectively. The rain gauging station in the village of Log pod Mangartom recorded 1638.4 mm of rainfall (more than 60% of the average annual precipitation) in the 48 days before the events (rainfall intensity of 1.42 mm/h in 1152 h). The recorded rainfall depth has a recurrence interval of more than 100 years. Other recorded rainfall depths of shorter duration (481.6 mm in 7 days, 174.0 mm in 24 h, 70 mm in 1 h) have recurrence intervals of much less than 100 years. A hydrological analysis of the event showed that the increase in runoff coefficients during the wet period in autumn 2000 before the landslide was as high as two- to threefold. An analysis using natural isotopes of δ¹⁸O and tritium of water samples from the Sto e landslide area has shown permanent but slow exfiltration of underground waters from a reservoir in the slope. In the case of low-intensity and long-duration rainfall in autumn 2000, relatively low permeable (10⁻⁷ m/s) morainic material was nearly saturated but remained stable (average porosity 21%, water content 20%, liquid limit 25%) until high artesian pressures up to 100 m developed in the slope by slow exfiltration from the relatively high permeable (10⁻⁵ m/s) massive dolomite. The Sto e landslide (two debris flow slides) was triggered by high artesian pressures built in the slope after long-duration rainfall. The devastating debris-flows formed from the landslide masses by infiltration of rainfall and surface runoff into the landslide masses and by their liquefaction.     

基于DEM的地质岩层体积求取方法的研究

地质岩层体积的求取一直是困扰地质学界的一难题．在对基于DEM的地质岩层体积求取方法进行说明的基础上．通过在陕西省长武县进行地质钻探和建立DEM．获得该地区各系岩层深度数据等基础数据及DEM．然后用GIS软件ARCVIEW中的三维分析模块．快速求取出本地区各系岩层体积，并对该方法的精度及注意的问题进行讨论．     

Distinct runoff processes in granite and sandstone drainage basins near Ulaanbaatar, Mongolia

Runoff processes in Mongolian drainage basins have received little study. The present work clarifies differences in runoff characteristics between granite (G-basin) and sandstone (S-basin) drainage basins near Ulaanbaatar. The drainage area of the G- and S-basins studied is 1.675 and 2.695 km² and the maximum relief is 450 and 500 m, respectively. These hydrological measurements reveal clear differences in runoff characteristics. First, the constant small discharge in the G-basin implies that the dominant runoff process is infiltration into bedrock or weathered mantle and that only baseflow occurs; quickflow and through-flow are not dominant. Second, clear peak discharges and rapid response of discharge to rainfall in the S-basin implies that surface flow occurs. Finally, the slow recession rate after peak discharge suggests that through-flow is more significant in the S-basin than in the G-basin.     

Differences in hillslope runoff and sediment transport rates within two semi-arid catchments in southeast Spain

This paper focuses on hillslope runoff and sediment transport within two catchments in southeast Spain. Five monitoring sites were established on hillslope concavities throughout the two catchments. The techniques used were mini-crest stage recorders, spray-painted lines, sediment traps and tipping bucket rain gauges (established during previous research). Results show that a storm event in the Rambla Nogalte on 30 June 2002 of 83.0 mm was responsible for a maximum runoff depth of 12 cm and a maximum hillslope sediment transport of 1886 cm³ m⁻¹. The same storm in the Rambla de Torrealvilla produced 53.4 mm of rainfall on the 1 July 2002, had a maximum runoff depth of 26 cm and resulted in 2311 cm³ m⁻¹ of sediment transport. There is evidence to suggest that measured sediment transport is related to runoff and a qualitative estimate of Morphological Runoff Zones (MRZ). Sediment transport and depth of runoff varied dramatically with lithology; marl sites produced most runoff and sediment transport, followed by the sites of mixed red and blue schist, then blue schist. These results are important for understanding the behaviour of slopes and show that for short lived storms with high, but not rare, rainfall intensities and total rainfall amounts, runoff can cause significant hillslope sediment transport in semi-arid areas.     

Spatial distribution of surface conditions and runoff generation in small arid watersheds, Zin Valley Badlands, Israel

High rill density may be regarded as indicative of frequent and integrated runoff along a drainage network. However, field observations of soil development and rill geometry in small, first-order catchments (0.1 to 1 ha) of the Zin Valley Badlands, northern Negev, Israel, suggest a pattern of partial area contribution and frequent flow discontinuities along hillslopes and channels. Changing soil properties, associated with an increase of slope angle and slope length, appear to be responsible for high infiltration on the slopes, leading to nonuniform runoff generation within small drainage basins. Runoff observation, sprinkling tests, and soil analysis along ridges and sideslopes were carried out to test this hypothesis. The results confirmed that infiltration capacity on the sideslopes is significantly higher than on the ridges. Under current rainfall conditions, only extreme rainfall intensities are sufficient to generate runoff along entire slopes. The discontinuous nature of most runoff events causes erosion on ridges and deposition on slopes, which enhances soil development on the valley sideslopes, creating a positive feedback on infiltration rate and depth. This demonstrates that the links between within-storm rainfall conditions and spatial distribution of soil characteristics have to be incorporated into our understanding of landscape development in badlands.     

多输入线性模型(MLM/MLPM)用于平原地区地表产汇流研究——以山东省赵牛河为例

本文介绍了两个系统模型（多输入线性模型MLM和多输入线性扰动模型MLPM）的基本思路，以赵牛河为研究流域，选取1960年～1967年逐日的降水、入流和出流、蒸发的资料，验算了两个模型。同时，结合一些计算结果，探讨了平原地区产汇流的一些特点。