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281.
A case study on the responses of streamflow to climate change in the Toutun River basin was carried out based on data analysis of streamflow, precipitation, and temperatures during the past 50 years.Temporal series of the streamflow change in the Toutun River basin was analyzed and tested using the Mann-Kendall nonparametric test. Results revealed that the annual runoff of the Toutun River had been in a monotonic decreasing trend for the past 50 years. Compared with the 1950s and 1960s, the annual runoff in the 1990s decreased by 4.0×105 m3 and 7.2×105 m3. The precipitation did not show monotonic trend during the past 50 years, but the annual temperature increased by 1.12℃ since the 1950s. Further data analysis indicated that the monthly runoff of the Toutun River decreased significantly from August to October, with precipitation displaying the similar pattern of seasonal change. Analysis suggests that the reduction of streamflow in the Toutun River basin is possibly caused by the seasonal change of precipitation, especially the precipitation reduction in summer, and temperature increases. 相似文献
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地下水化学动力学基本理论在矿井水文地质中的应用 总被引:2,自引:0,他引:2
根据西峪煤矿水化学及相关水文地质资料,运用地下水化学动力学的基本理论和方法,对西峪煤矿奥陶系峰峰组岩溶含水层水文地质条件进行了定量评价,从而划分出了含水层的强、弱径流带,为煤矿的安全生产提供了依据。 相似文献
285.
水稻时域散射特征分析及其应用研究 总被引:14,自引:3,他引:14
通过对肇庆试验区1996年和1997年获取的多时相、多模式雷达卫星(RADARSAT)数据分析,从图像上直接提取地物的后向散射系数,结合实地测量水稻的生长结构参数,建立了水稻生长模型,分析了不同生长周期(从80天到120-125天)4种类型水稻的时域散射特性。利用1997年4月至7月获取的7景标准模式雷达卫星数据,对试验区内三个县和两个行政区共5000km^2面积范围内的作物进行分类和水稻产量预估算,水稻类型分类及面积量算精度达91%。结果表明:利用雷达遥感数据进行水稻种植面积量算和估产需要水稻生长期间三个时相的数据,即插秧期、抽穗期、收割前期。若能够获得多参数雷达图像,可以用插秧期和收割前期的两个时相图像来代替上述的三个时相图像同样可以达到种植面积量算和估产的效果。这一结果充分说明多时相雷达卫星数据对我国南方水稻长势监测及估产具有明显优势和潜力。 相似文献
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An in-situ experimental program in a jointed rock mass was designed and implemented to investigate the rock joint effects on stress wave propagation. Accelerometers were placed on rock surface along three lines at 0, 45 and 90° to the predominant rock joint strike direction. Eight blasts were detonated in a charge hole drilled in the rock mass. The equivalent TNT blast weight ranged from 2.5 to 50.0 kg and the loading density (charge weight divided by the charge chamber volume) varied from 1 to 20.0 kg/m3. A fully coupled detonation with a charge weight of 25.0 kg was also exploded to study the coupling effect. The recorded data are presented and analyzed in this paper. The effects of rock joints on characteristics of stress wave propagation such as peak value attenuation, spectrum, and spatial variations are discussed. 相似文献
289.
丘陵山区低空急流特性分析 总被引:1,自引:0,他引:1
利用丘陵区边界层实测资料,分析了该地区8-9月份低空急流的特征及其演变规律;并从测站所处的地理环境,山凰 地形的力差异以及适中的风平流作用等,探讨了测站上空逆温的形成及其对低空急流的形成和维持作用,根据地形热力差所导致的气压斜压性,研究了低空急流的生消可能机制。 相似文献
290.
On three-dimensionality of shelterbelt structure and its influences on shelter effects 总被引:5,自引:0,他引:5
Natural shelterbelts, unlike planar barriers, have a certain width, within which interactions among wind speed, drag force and pressure perturbations create a net sheltering effect. The variations of flow, drag force, permeability, and pressure perturbation for shelterbelts of different widths and different horizontal structures are numerically studied, and their influences on shelter efficiency are discussed. Comparisons are made of fourteen medium-dense shelterbelts, with the same overall leaf-area, that differ only in width or horizontal distribution of leaf-area density. The simulated results are consistent with both field observations and wind-tunnel measurements.The simulations demonstrate that the total drag force of the entire shelterbelt varies little with changes in width and structure. The results also show that shelter distance and the overall average wind speed reduction decrease only by 15–18% as width increases by a factor of 100, and changes even less for different internal structure. However, width greatly affects the location of minimum wind speed, pressure perturbation, and the permeability of shelterbelts. Horizontal changes of wind speed inside the uniform shelterbelts have four different patterns, which depend on shelterbelt width and height. The absolute pressure perturbation significantly decreases with increasing width. A possible cause of the insensitivity of shelter efficiency to width and internal inhomogeneous structure is the compensation between the effects of permeability and pressure perturbation on shelter efficiency. 相似文献