Estimation of suspended sediment loads and delivery in an incised upland headwater catchment,south‐eastern Australia     

Hugh G. Smith 《水文研究》2008,22(16):3135-3148

Historically upland headwater catchments in south‐eastern Australia have undergone extensive gully erosion that has removed large amounts of sediment to lowlands. Recent research suggests these upland areas may continue to dominate fine sediment loads in lowland rivers. Improved understanding of sediment transfer through upland headwater catchments may have implications for interpreting downstream sediment supply. In this study a nested catchment design was utilized to examine suspended sediment yields and delivery from a small tributary sub‐catchment (1·64 km²) to the study catchment outlet (53·5 km²). Monitoring of suspended sediment concentration and discharge was undertaken for a period of nearly two years and used to estimate suspended sediment loads. Estimated total suspended sediment exports over the period of monitoring were 24·16 t from the sub‐catchment and 550·3 t from the catchment, which are generally less than previous reported small catchment yields in south‐eastern Australia. The extent of sediment delivery was examined using between‐site ratios of specific sediment yield per unit area and incised channel length. Sediment delivery was high under average rainfall conditions, but seasonally dependent. Both suspended sediment yields and the extent of delivery peaked over spring months, supplemented by remobilization of sediment stored during summer months in the main catchment channel. The findings of this study suggest much of the suspended sediment exported from small incised upland sub‐catchments (1–2 km²) may be delivered to downstream reaches under average rainfall conditions, which, in conjunction with the findings of previous research supports the potential importance of contributions from these areas to suspended sediment loads in lowland rivers during high flow periods. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

水流流量计的设计与开发     

王杰  文斌  高瑜翔 《成都信息工程学院学报》2006,21(Z1):26-29

采用水压传感器、流速传感器、 STC89C58RD MCU等器件的明渠流量测量仪表能自动完成流态判别、流量公式和流量参数选择,实时获得明渠流量.具有成本低、精度高、安装使用简便、可广泛应用等优点.  相似文献   

Using a fluctuating tracer to estimate hyporheic exchange in restored and unrestored reaches of the Truckee River,Nevada, USA     

Andrew E. Knust  John J. Warwick 《水文研究》2009,23(8):1119-1130

The goal of this research was to compare hyporheic activity in recently restored and adjacent un‐restored reaches of the Truckee River downstream from the Reno/Sparks metropolitan area. The installation of rocky riffles and raised channel bed elevations in the restored reaches may have increased the degree of surface–subsurface interaction. A fluctuating chloride concentration signal served as the tracer, induced by the variable influx of higher salinity water several miles upstream from the study reach. The solute transport model, OTIS, was used in conjunction with the hydrodynamic model, DYNHYD5, to estimate transient storage parameters under unsteady flow conditions. The model was calibrated to chloride concentrations measured over a period of three days at six in‐stream locations representing restored and un‐restored reaches. An automated parameter estimation algorithm (SCE‐UA) was used to optimize parameters for multiple reaches simultaneously and generate a distribution of parameter estimates. Results suggest that the transient storage zone cross‐sectional area (A_s) is larger in the restored reaches than in the unrestored reaches, but the exchange coefficient (α) is smaller, leading to increased hyporheic residence time and hydrologic retention in the vicinity of channel reconstructions. Scenarios were used to simulate the potential effects of increased subsurface residence time on denitrification and in‐stream NO₃‐N concentrations. Monte Carlo analysis was performed to assess uncertainty in the simulation results and show the potential for greater nutrient retention in the lower Truckee River as a result of channel restoration. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

隔河岩遥测地震台网无线信道计算及测试     

倪焕明  宁积艮 《大地测量与地球动力学》1997,(4)

隔河岩遥测地震台网是由７个遥测地震台、２个中继站和１个接收记录中心组成的地方性遥测台网，其目的是监测隔河岩水库诱发地震活动。台网的合理布局保证了在台网检测范围内地震定位的精度优于Ⅰ类，重要地段的地震监测能力为ＭＬ≥０．５级。台网采用了２２３ＭＨｚ频段的无线传输地震遥测设备。测试结果表明，无线信道功率裕量均在３０ｄＢ以上，信道可靠性优于９９．９９％，各道信号实际连续率在９９．６７％以上，超过规范规定的要求。自１９９３年运行以来，获得了高质量的产出。  相似文献   

直流电源故障的微机检测     

韩玉英 《成都信息工程学院学报》2002,17(3):188-191

介绍了利用IMB－PC 8088CPU的单板机控制检测多路直流电源过压、欠压。在出现此类故障时能发出报警声，并在显示器上显示故障电源编号，同时切断故障电源，启动同类备用电源，以便维修。  相似文献   

Dispersion of guided waves in thin anisotropic waveguides   总被引：1，自引：0，他引：1  

Min Lou  Stuart Crampin 《Geophysical Journal International》1991,107(3):545-555

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Reduction of discharge hydrograph and flood stage resulted from upstream detention ponds     

Ching-Nuo Chen  Chih-Heng Tsai  Chang-Tai Tsai 《水文研究》2007,21(25):3492-3506

The models of physiographic inundation and flood routing for channel network were used in this study to analyse the influence of the Tainan Scientific Base Industrial Park (TSBIP) and Feng-Hua detention ponds on the inundated potential, inundated volume, flood damage, and flood stage of peak flow along the Yen-Shui creek in 2-day flood for the 2-, 10- and 50-year return periods, respectively. The computed results show that the TSBIP detention ponds are able to reduce the inundated area and flood damage. However, the decrease in inundated area is not obvious for the 50-year return-period flood. Construction of the Feng-Hua detention pond resulted in a significant decrease in the flood stage along the Yen-Shui creek in the downstream reach. Moreover, the decrease in peak flow and lag of time-to-peak become increasingly evident in the downstream direction for the 2- and 10-year return-period events. For the 50-year return period, the lag of time-to-peak is not apparent, but the decrease in peak flow is still noticeable. In respect to the performance of detention ponds, the slopes of hydrographs in the rising and recession segments are smoother than those without detention ponds. Meanwhile, the shapes of peak become flatter if the detention ponds are installed. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

EXPERIMENTS OF INFLUENCE OF DISCHARGE PROCESS ON CHANNEL PATTERN     

ZHANGJun-yong CHENLi 《中国地理科学(英文版)》2004,14(4):332-336

Based on experimental data and theory, by means of simplified discharge durations in a small flume,the influence of discharge process on channel morphology and channel pattern was analyzed in this paper. It was concluded that on the same original channel, different discharge and channel conditions would end with different river morphology, including thalwegs and radius of bends. Different discharge process resulted in two kinds of change:tiny change in the process of “big-small-big” and distinct change in the process of “small-big-small”. Flood discharge duration was verified to be the main cause in the discharge process. Proper discharge process will change the morphologies of river, even can led to channel pattern transformation. The influences based on the relationship between the flow and the channel itself, including slope and riverbed constitution. Although not be a main cause, original channel morphology may influence its final channel pattern. Neglecting the influence of channel itself will hamper the understanding of channel patterns.  相似文献   

我国地基雷达观测月球的现状和研究进展     

孙靖  杨嵩  周峰  丁宗华  刘磊  曹建峰  韩松涛  平劲松 《天文研究与技术》2022,(1)

地基雷达观测可以提供太阳系天体目标的地形地貌、物理特征、轨道动力等信息。聚焦利用地基雷达天文技术开展月球观测的原理方法和科学意义,介绍了基于我国现有深空雷达上行装置、射电望远镜条件以及非相干散射雷达等系统,初步开展的特高频段(Ultra High Frequency,UHF)和X频段的地基雷达观测月球试验。通过月球反射回波的信号处理,获得了延迟、多普勒频移等参数,得到了一致的与近表层物质密度相关的月面雷达反射率,并得到了月球的左右旋圆极化率,反映了与波长同尺度的月球近表层结构。文章积累的数据处理经验将为我国的小行星预警、行星历表等地基雷达观测研究提供技术基础。  相似文献   

Morphodynamics of an erodible channel under varying discharge     

David L. Adams 《地球表面变化过程与地形》2021,46(12):2414-2420

Alluvial channels arise through the interaction between morphology, hydraulics, and sediment transport, known as the ‘fluvial trinity’. Over relatively short timescales where climate and geology are fixed but discharge and sediment supply may vary, this process facilitates adjustments towards steady state, where the system oscillates around a mean condition. The relationship between changes in conditions and geomorphic response may be highly complex and nonlinear, especially in systems with multiple modes of adjustment. This study examines the adjustment of an erodible channel with fixed banks and a widely graded sediment mixture to successive increases in discharge. With each increase in discharge, components of the fluvial trinity adjusted towards a steady state. Particularly at relatively low discharges, adjustments were controlled by intrinsic thresholds and highlighted important morphodynamic processes. Notably, there was a strong interplay between channel morphology and sediment transport, and an effect whereby larger-than-average grains controlled channel deformation. These two processes occurred at the bar scale and were highly spatialised, which has two important implications: (1) reach-averaged representations of process provide only partial insight into morphodynamics; and (2) models of rivers that suppress these process feedbacks and size-dependent transport may not replicate morphodynamics that typically occur in field conditions. The experiments provide quantitative evidence for conceptual models describing exponential approaches towards steady state and the potential for transiency if disturbance frequency exceeds the recovery time. They also highlight how in natural rivers, particularly those with greater degrees of freedom for adjustment (notably, lateral adjustment and meandering), continuous changes in discharge may lead to nonlinear rather than steady-state behaviour. In these settings, more holistic analytical frameworks that embrace different aspects of the system are critical in understanding the direction, magnitude and timing of channel adjustments.  相似文献