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A comparison of high‐resolution specific conductance‐based end‐member mixing analysis and a graphical method for baseflow separation of four streams in hydrologically challenging agricultural watersheds 下载免费PDF全文
Quantifying the relative contributions of different sources of water to a stream hydrograph is important for understanding the hydrology and water quality dynamics of a given watershed. To compare the performance of two methods of hydrograph separation, a graphical program [baseflow index (BFI)] and an end‐member mixing analysis that used high‐resolution specific conductance measurements (SC‐EMMA) were used to estimate daily and average long‐term slowflow additions of water to four small, primarily agricultural streams with different dominant sources of water (natural groundwater, overland flow, subsurface drain outflow, and groundwater from irrigation). Because the result of hydrograph separation by SC‐EMMA is strongly related to the choice of slowflow and fastflow end‐member values, a sensitivity analysis was conducted based on the various approaches reported in the literature to inform the selection of end‐members. There were substantial discrepancies among the BFI and SC‐EMMA, and neither method produced reasonable results for all four streams. Streams that had a small difference in the SC of slowflow compared with fastflow or did not have a monotonic relationship between streamflow and stream SC posed a challenge to the SC‐EMMA method. The utility of the graphical BFI program was limited in the stream that had only gradual changes in streamflow. The results of this comparison suggest that the two methods may be quantifying different sources of water. Even though both methods are easy to apply, they should be applied with consideration of the streamflow and/or SC characteristics of a stream, especially where anthropogenic water sources (irrigation and subsurface drainage) are present. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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基于DEM的单位汇水面积尺度转换(英文) 总被引:5,自引:1,他引:4
Specific Catchment Area (SCA) is defined as the upstream catchment area of a unit contour. As one of the key terrain parameters, it is widely used in the modeling of hydrology, soil erosion and ecological environment. However, SCA value changes significantly at different DEM resolutions, which inevitably affect terrain analysis results. SCA can be described as the ratio of Catchment Area (CA) and DEM grid length. In this paper, the scale effect of CA is firstly investigated. With Jiuyuangou Gully, a watershed about 70 km2 in northern Shaanxi Province of China, as the test area, it is found that the impacts of DEM scale on CA are different in spatial distribution. CA value in upslope location becomes bigger with the decrease of the DEM resolution. When the location is close to downstream areas the impact of DEM scale on CA is gradually weakening. The scale effect of CA can be concluded as a mathematic trend of exponential decline. Then, a downscaling model of SCA is put forward by introducing the scale factor and the location factor. The scaling model can realize the conversion of SCA value from a coarse DEM resolution to a finer one at pixel level. Experiment results show that the downscaled SCA was well revised, and consistent with SCA at the target resolution with respect to the statistical indexes, histogram and spatial distribution. With the advantages of no empirical parameters, the scaling model could be considered as a simple and objective model for SCA scaling in a rugged drainage area. 相似文献
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High-resolution Surface Relative Humidity Computation Using MODIS Image in Peninsular Malaysia 总被引:4,自引:0,他引:4
1 Introduction The Canadian Fire Weather Index (FWI) System can be used in applied forestry as a tool to investigate and manage all types of fire management (Chrosciewicz, 1978; McRae, 1980; Fyles et al., 1991; McRae et al., 1994). The development of the FWI system (Van Wag- ner, 1987; 1990) over the last two decades allows the routine prediction of fire behavior from weather data (Fyles et al., 1991). The FWI is calculated from point measurements of air temperature, relative humidity… 相似文献
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STREAMFLOW CHARACTERISTICS OF THE EASTERN QINGHAI-XIZANG PLATEAU 总被引:1,自引:0,他引:1
The eastern Qinghai-Xizang (Tibet) Plateau is the headwater area for many large Asian rivers. Permafrost occurs above 4,200 m a.s.l. and glaciers occupy the summits and high valleys of the east-west trending mountain chains. Annual runoff generally increases with precipitation which is augmented southward by the rise in topography. Rainfall, snow melt, glacier melt and groundwater are the primary sources of stream flow, and the presence of permafrost enhances the flashiness of runoff response to rainfall and snowmelt events. Peak flows are concentrated between June and September. And winter is low flow season. Three types of runoff patterns may be distinguished according to their primary sources of water supply: snowmelt and rainfall, glacier melt and snowmelt, and groundwater. Large rivers generally drain more than one environments and their runoff regime reflects an integration of the various flow patterns on the plateau. 相似文献
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重力测量系统中测量的重力,即重力加速度,是一种特殊的加速度,因而重力传感器是一种特殊的加速度计。在动态场合,现代重力仪一般采用基于陀螺仪构建的各种平台为重力传感器提供姿态基准。因此采用加速度计和陀螺仪这些惯性元件的动态重力测量系统可以看做是惯性技术的一种具体应用。从惯性技术的角度对动态重力测量的理论和现状进行了分析。首先介绍了在地球表面附近进行重力测量时涉及的参考坐标系。然后详细推导了动态重力测量的基本理论,即比力测量理论,指出比力方程是动态重力测量和惯性导航的共同基础。最后对不同载体对动态重力测量系统的影响与要求进行了分析。 相似文献
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以小球藻(Chlorella sp. CHX-1)为实验材料,采用外切中心复合设计试验法(CCC)研究了温度(16~34 ℃)和盐度(15~45)对小球藻生长的联合效应.结果表明:温度与盐度的-次、二次效应对小球藻比生长速率都有极显著影响(P 〈 0.01),温度、盐度之间的互作效应对小球藻比生长速率影响显著(P 〈 0.05),温度的效应大于盐度的效应.响应曲面法分析发现,随着温度和盐度的升高,小球藻的比生长速率呈先上升后下降的趋势.建立小球藻生长与温度、盐度的回归模型方程,该模型的决定系数0.991 7,矫正决定系数0.985 8,表明模型的拟合度极高;模型的预测决定系数0.949 8,可用于预测小球藻比生长速率的变化.通过模型优化和验证实验,得到在温度、盐度组合为25.9 ℃/28.4 时,小球藻比生长速率达到最大值0.652,满意度为0.981. 相似文献