天山北坡中段暴雨洪水洪峰模数分布规律分析

暴雨洪峰模数法是水文分析计算中进行设计洪水计算较为常用的一种方法,由于其原理简洁,使用直观、方便,其精度也得到验证,因而在设计洪水计算中广为使用,本文根据新疆天山北坡中段各河流暴雨洪水资料,采用相关分析等方法推求洪峰模数与流域平均高程、河道纵坡降之间的关系,分析暴雨洪水洪峰模数在天山北坡中段地区上的分布规律,解决该区域小河(沟)在缺乏实测资料情况下设计暴雨洪水计算方法多样性[1]的途径。     

水面蒸发量分析计算

水面蒸发量计算是水文水利计算、径流预测预报、水资源调查评价等工作中必不可少的内容,是一个地域主要的水分支出项,与一个地域的水分收入项降水量,共同决定了一个地域的湿润状况,因此水面蒸发的研究是一项十分重要的工作。水文部门的蒸发站在结冰期使用D-20蒸发皿,非结冰期使用E-601蒸发器或80 cm套蒸发皿来测定水面蒸发量。文章采用了折算系数,折算成E-601并分析了水面蒸发量的时空变化规律。     

Identifying Temperature Thresholds Associated with Fish Community Changes in British Columbia,Canada, to Support Identification of Temperature Sensitive Streams

We collected fish samples and measured physical habitat characteristics, including summer stream temperatures, at 156 sites in 50 tributary streams in two sampling areas (Upper Fraser and Thompson Rivers) in British Columbia, Canada. Additional watershed characteristics were derived from GIS coverages of watershed, hydrological and climatic variables. Maximum weekly average temperature (MWAT), computed as an index of summer thermal regime, ranged from 10 to 23 °C. High values of MWAT were associated with large, warm, low relief watersheds with a high lake influence. Measures of community similarity suggested that the fish community changed most rapidly through a lower transition zone at an MWAT of about 12 °C and an upper transition zone at an MWAT of about 19 °C. These results were confirmed using existing fisheries inventory data combined with predictions of MWAT from a landscape‐scale regression model for the Thompson River watershed. For headwater sites in the Chilcotin River watershed (which drains into the middle Fraser River), the relative dominance of bull trout versus rainbow trout (based on inventory data) decreased with increasing predicted MWAT although the distinction was not as clear as for the Thompson River sites. The fish communities in these watersheds can be characterized in terms of very cold water (bull trout and some cold water species), cold water (salmonids and sculpins) and cool water (minnows and some cold water salmonids). The two transition zones (ca 12 and 19 °C) can be used to identify thresholds where small changes in stream temperature can be expected to lead to large changes in fish communities. Such clear, quantifiable thresholds are critical components of a management strategy designed to identify and protect vulnerable fish communities in streams where poor land use practices, alone or in combination with climatic change, can lead to changes in stream temperatures. Copyright © 2015 John Wiley & Sons, Ltd.     

Heterogeneous information exposure and technology adoption: the case of tissue culture bananas in Kenya

Classical innovation adoption models implicitly assume homogenous information flow across farmers, which is often not realistic. As a result, selection bias in adoption parameters may occur. We focus on tissue culture (TC) banana technology that was introduced in Kenya more than 10 years ago. Up till now, adoption rates have remained relatively low. We employ the average treatment effects approach to account for selection bias and extend it by explicitly differentiating between awareness exposure (having heard of a technology) and knowledge exposure (understanding the attributes of a technology). Using a sample of Kenyan banana farmers, we find that estimated adoption parameters differ little when comparing the classical adoption model with one that corrects for heterogeneous awareness exposure. However, parameters differ considerably when accounting for heterogeneous knowledge exposure. This is plausible: while many farmers have heard about TC technology, its successful use requires notable changes in cultivation practices, and proper understanding is not yet very widespread. These results are also important for other technologies that are knowledge‐intensive and require considerable adjustments in traditional practices.     

汕头市水文特性分析

按广东省水资源调查评价的要求和标准,根据汕头市多年统计资料,从降水、蒸发、干旱指数、径流和泥沙等方面对其水文特性进行了分析。     

灰关联分析与多元线性回归模型联合应用研究

依据50年(1954~2003)和田绿洲的气象资料,应用灰关联分析,发现影响绿洲蒸发能力的主要因子是相对湿度与平均气温;在此基础上建立了回归模型。该模型模拟预测绿洲蒸发能力的变化精度较高,但需进一步改进。这种途径比逐步回归分析减少了分析工作量和上机时间。     

均值与极差管理图在混凝土生产中的应用

混凝土拌和物质量的优劣,直接影响到枢纽运行安全及建筑物的使用寿命.为获得优质的混凝土,建立健全质量保证体系,提高拌和楼生产水平,是施工单位和工程监理人员的首要任务.混凝土标准试件强度一般按设计规定的龄期破型获取试验结果,故不能及时反映混凝土生产过程和强度指标是否处于受控状态.水灰比是决定混凝土强度和耐久性的主要因素,采用水灰比均值与极差管理图的控制方法,能快速、准确地发现生产过程中的异常情况,及时制定相应的改进措施,提高混凝土生产水平.实践证明:应用管理图进行混凝土生产过程质量控制,是一种简便、可靠的有效方法.     

干旱区潜水蒸发的影响因素和计算方法分析

潜水蒸发是干旱区天然植被耗水的主要来源,其大小决定着干旱区天然绿洲生态的规模.本文对干旱区潜水蒸发的影响因素和计算方法进行了系统地分析和讨论,以期为指导干旱区的生态建设提供参考.     

改进灰色模型在水量预测中的应用

灰色模型对生活用水量进行预测本身具有一定的局限,数据离散程度越大,灰度也愈大,其预测精度也越差.文中采用滑动平均法对灰色预测的原始数据进行了改进,并采取残差修正,避免了数值过度波动.通过预测实例,结果表明改进后的灰色预测模型能有效提高预测精度.     

阶梯式溢流面水力特性规律研究

通过调研、专题和实际工程物理模型试验研究,对阶梯式溢流面的水流流态、掺气特性、坡面均匀流水深、时均压力分布特征及消能效果进行了较系统全面的研究,分析了各种水力特性参数的主要影响因子及其规律.