三峡库区森林流域林地的地表糙率系数

2 0 0 2— 2 0 0 3年期间 ,作者选择三峡库区响水溪流域 1 1块具有典型代表性的林地 ,在野外小区径流实验基础上 ,通过曼宁公式 ,对地表糙率系数进行了定量研究 .结果表明 ,地表糙率系数介于 0 0 1 82～ 0 2 5 75之间 ,其中板栗林地小区糙率系数值最小 ,杉木、马尾松、阔叶林混交林地小区糙率系数值最大 .大小依次排序为杉木、马尾松、阔叶林混交林 >尖杉、马尾松、阔叶林混交林 >石栎纯林 >柳杉纯林 >马尾松、阔叶林混交林 >柳杉、楠竹混交林>尖杉纯林 >荒草地 >楠竹林 >杉木纯林 >板栗林 .

植被分布对地表糙率影响

[目的]分析在植被淹没或非淹没状态不同植被覆盖密度影响下,地表糙率的变化规律与特征,为进一步研究植被对地表糙率的影响提供参考。[方法]试验以塑料棒模拟植被分布,模拟出不同密度,分别进行放水试验。[结果]在植被淹没与非淹没状态下地表糙率的变化不同,在非淹没状态时,地表糙率随着平均水深的增加呈减小的趋势,在淹没水深小时,地表糙率随着平均水深的增加而先增大后减小,而当淹没水深很大时,地表糙率趋向于一个稳定值。[结论]地表糙率取值随植被覆盖密度的增大而增大;同一下垫面情况下,不同的水流方向,地表糙率取值不相同。

地表糙率对坡面流流速影响的试验研究

地表糙率是影响坡面流流速特征及变化过程的重要因素。本研究采用变坡试验水槽在粗糙粒径（d≤10mm）、单宽流量（0.04-0.24 L·s^-1·m^-1）和坡度（2°-12°）范围内,利用定床阻力冲刷试验系统研究坡面流平均流速与粗糙粒径、流量和坡度之间的关系。结果表明：随着地表糙率的增加,水流克服阻力做功增加,能量降低,流速呈指数函数减小。地表糙率不同会导致坡面流速的主要控制因素不同,当粗糙粒径较小（0≤d≤2.5mm）时,糙率、流量和坡度对流速均有显著影响,解释方差分别为19.8%、44.8%和27.8%;当粗糙粒径较大（2.5〈d≤10mm）时，糙率和坡度对流速的影响很小（影响程度分别占8．8％和1．5％），流量为主要影响因素（占84．1％）。经多元回归分析发现，糙率对流速的影响最大（54．6％），流量次之（30．8％），坡度最小（6．6％），三者可以较好模拟定床条件下的水流流速（R^2=0．919），且流速与糙率负相关，与流量和坡度正相关。该研究结果有助于深入了解不同糙率的定床阻力下坡面流流速的时空分布特征，为坡面土壤侵蚀过程物理模型的建立提供科学依据。

3种地表随机糙率测量方法比较

为定量比较3种地表随机糙率测量方法的异同,采用砾石覆盖、枯落物覆盖及不同农事活动3种下垫面条件,分别利用三维激光扫描法、照相法和测针法测量了不同处理下的地表随机糙率,以激光扫描法测量结果为基准值,通过绝对误差、相对误差和均方根误差比较了3种测量方法的差异。结果表明:激光扫描法测量精度最高,但仪器价格昂贵,且用于野外测量时需要注意光照影响;照相法精度较高,测量快捷方便,与扫描法的平均绝对误差为0.65 mm,平均相对误差为14.0%,但需手动测量各控制点间的相对距离,也需要避免光照影响;测针法易于操作、成本最低,但费时费力、精度不高,与扫描法的平均绝对误差为1.82 mm,平均相对误差为34.1%。因此,3种方法各有利弊,需根据实际情况选择合适的测量方法测定地表随机糙率,当精度要求不是非常严格时,推荐优先使用照相法。研究结果对随机糙率测量方法的正确选择,提高地表糙率测量精度,具有重要的指导意义。

林下地被物保水保土作用研究进展

较为系统地总结了部分前人关于林下枯落物和苔藓对水土保持、环境保护等方面作用的研究成果,林下枯落物和苔藓均具有较强的吸持降水、涵养地表径流、增加地表糙率、改良土壤特性等作用。部分学者的研究成果还表明,苔藓对环境变化具有指示和监测作用。

Research of the electrical anisotropic characteristics of water-conducting fractured zones in coal seams

Water flooding disasters are one of the five natural coal-mining disasters that threaten the lives of coal miners. The main causes of this flooding are water-conducting fractured zones within coal seams. However, when resistivity methods are used to detect water-conducting fractured zones in coal seams, incorrect conclusions can be drawn because of electrical anisotropy within the water-conducting fractured zones. We present, in this paper, a new geo-electrical model based on the geology of water-conducting fractured zones in coal seams. Factors that influence electrical anisotropy were analyzed, including formation water resistivity, porosity, fracture density, and fracture surface roughness, pressure, and dip angle. Numerical simulation was used to evaluate the proposed electrical method. The results demonstrate a closed relationship between the shape of apparent resistivity and the strike and dip of a fracture. Hence, the findings of this paper provide a practical resistivity method for coal-mining production.

Eddy covariance measurements of water vapor and CO_2 fluxes above the Erhai Lake

Measurement of turbulence fluxes were performed over the Erhai Lake using eddy covariance(EC) method.Basic physical parameters in the lake-air interaction processes,such as surface albedo of the lake,aerodynamic roughness length,bulk transfer coefficients,etc.,were investigated using the EC data in 2012.The characteristics of turbulence fluxes over the lake including momentum flux,sensible heat flux,latent heat flux,and CO2 flux,and their controlling factors were analyzed.The total annual evaporation of the lake was also estimated based on the artificial neural network(ANN) gap-filling technique.Results showed that the total annual evaporation in 2012 was 1165 ± 15 mm,which was larger than the annual precipitation(818 mm).Local circulation between the lake and the surrounding land was found to be significant throughout the year due to the land-lake breeze or the mountain-valley breeze in this area.The prevailing winds of southeasterly and northwesterly were observed throughout the year.The sensible heat flux over this plateau lake usually had a few tens of W m-2,and generally became negative in the afternoon,indicating that heat was transferred from the lake to the atmosphere.The sensible heat flux was governed by the lake-air temperature difference and had its maximum in the early morning.The diurnal variation of the latent heat flux was controlled by vapor pressure deficit with a peak in the afternoon.The latent heat flux was dominant in the partition of available energy in daytime over this lake.The lake acted as a weak CO2 source to the atmosphere except for the midday of summer.Seasonal variations of surface albedo over the lake were related to the solar elevation angle and opacity of the water.Furthermore,compared with the observation data,the surface albedo estimated by CLM4-LISSS model was underestimated in winter and overestimated in summer.