考虑降雨和蒸发条件的非饱和朗肯土压力计算分析

降雨和蒸发会引起非饱和土体中水分的改变,从而导致基质吸力的变化。针对降雨和蒸发对非饱和土压力的影响,将稳定状态下非饱和土中的水流控制方程运用到朗肯土压力计算中,同时考虑中间主应力的影响,推导出降雨和蒸发条件下主动土压力公式和被动土压力公式,克服了朗肯土压力的不足。研究结果表明:降雨条件下,随着中间主应力参数b的增大和降雨强度的减小,主动土压力逐渐减小,被动土压力逐渐增大;蒸发条件下,随着中间主应力参数b和蒸发强度的逐渐增大,主动土压力逐渐减小,被动土压力逐渐增大。在进行土压力计算时,考虑降雨、蒸发和中间主应力的影响,更符合实际情况,更能发挥非饱和土体的自身性能。     

Evaporation modelling using neural networks for assessing the self‐sustainability of a water body

Studies addressing the self‐sustainability of water bodies are crucial from the perspective of sustainable water resources management. An artificial water body is vulnerable to drastic water level changes resulting from various hydroclimatical and geological factors. It is incumbent therefore to rigorously investigate the effects of these factors in order to assess the response of the water body, consequent to a wide range of scenarios. This study focuses on the self‐sustainability of a water body, based on the water budget approach, and taking into account various hydroclimatical and geological factors in the study area. As the available evaporation data shared a very short (~2 years) common time frame with the other variables, evaporation was modelled using regression and artificial neural network models. The study results indicated the water body would be self‐sustainable under the extreme climatical and hydrological conditions considered. While seepage exhibited substantial impacts on the storage of the water body, evaporation was found to have only marginal impacts.     

The utility of thermal satellite images and land-based meteorology to estimate evaporation from large lakes

Evaporation measurements over lakes are limited by physical constraints, logistics and financial demands. Thermal satellite images and land-based meteorology can be combined to derive evaporation rates from large lakes. The Dead Sea is a large hypersaline lake that can be used to examine the utility of thermal satellite images along with land-based meteorology to assess evaporation rates. Sea surface tmperature was retrieved for a 12-month period using band 10 onboard Landsat 8. Monthly SST was combined with nearby land-based meteorology to estimate evaporation from the sea surface using a mass transfer method and two variations of the Penman procedure. The Mass transfer gave an annual evaporation rate of 1005 mm whereas the Penman and the Priestley-Taylor methods gave 1308 and 1140 mm, respectively. These values are commensurate with extensive field measurement and theoretically derived evaporation values. Analysis shows a tradeoff between wind speed increase over the smoother lake surface and the drop in the saturation water vapor pressure deficit across the lake-atmosphere boundary. Wind speed has profound effects on evaporation differences during the warm season but diminish appreciably in the cold season when the vapor pressure deficit is small. Thermal images were able to resolve the presence of large pockets of cool water over the Dead Sea resulting from freshwater input. Modifications to evaporation caused by freshwater input to a hypersaline lake are investigated from a thermodynamic perspective. The alteration to evaporation depends on the simultaneous departure of surface temperature and the activity of the brine.     

论巨型水轮发电机冷却方式的选择

回顾了二滩水电站水轮发电机空冷方式的选择；论述了近年来对水轮发电机空冷方式新的认识：“能空冷就不要水冷”；介绍了龙滩、小湾和拉西瓦水电站水轮发电机空冷方案的确定历程及所采取的相应措施：提出“要水冷，不如上蒸发冷却”。     

风对北大港水库水质咸化影响的理论分析与实验研究

从理论上分析了风加快北大港水库水体水质咸化速度的原因，一是由于风对水体的扰动作用，加快了盐份从底部土壤向整个水体的扩散速度，二是风可加快水体的蒸发速度，加速了水体的蒸发浓缩作用，并通过有风、无风的对比实验定性地证明了此结论。     

不同覆盖材料对干旱区春小麦棵间蒸发的影响

为深入分析不同覆盖材料对干旱区春小麦棵间蒸发的影响,采用微型蒸发仪研究了石羊河流域地膜覆盖和秸秆覆盖条件下的春小麦棵间蒸发.研究表明:试验区春小麦棵间蒸发表现为生长初期和末期较高,生长中期较小的特点.相对无覆盖措施,地膜覆盖和秸秆覆盖日均棵间蒸发量分别降低15.6%和36.1%.无覆盖措施、地膜覆盖和秸秆覆盖的累计棵间蒸发量分别占春小麦生育期降水量及相应总灌水量之和的30.4%,26.2%和19.9%.拔节之前,地膜覆盖和秸秆覆盖条件下春小麦的棵间蒸发受表层土壤水分的影响程度基本一致,拔节之后,秸秆覆盖表现出相对地膜覆盖更好的保墒效果.     

高精度蒸发自动测试仪的研制

本文介绍了综合运用水文学、机械工程学以及现代电子学技术,成功研制的一种能满足有关国家测量规范精度要求的高精度蒸发自动测试仪器。现场试用后,通过对自动测量数据和人工测量数据进行的对比分析证明,该蒸发仪能够实现蒸发量的高精度自动测量。     

鄂尔多斯市水资源的气候特征演变

采用鄂尔多斯市鄂托克旗站和东胜站1957-2010年的月均温和月降水资料,分析了气温和降水的演变规律。采用高桥浩一郎的陆面蒸散发经验公式估算陆面蒸散发并分析演变规律。结果表明:鄂尔多斯市自20世纪90年代开始显著增温,东部东胜站增温幅度大于西部鄂旗站。四季中各季的显著升温也出现在90年代。夏季增温相对缓慢,其它三季变暖比较显著。两站年降雨量均呈减小趋势,东部东胜站减少量大于西部鄂旗站。春冬两季降雨量变化趋势不明显,夏秋两季降雨量呈减小趋势。蒸散量均呈现上升趋势,20世纪90年代以后上升趋势明显。东部东胜站多年平均年蒸散量大于西部鄂旗站。春、夏、冬三季蒸散量均呈上升趋势,而在秋季均呈下降趋势。降水量显著影响降蒸差,可利用降水量呈下降趋势,东部的东胜站下降趋势更明显。     

干旱区水面蒸发特性及消减技术研究

根据现代节水灌溉兵团重点试验站Φ20 cm蒸发器、E601型蒸发器和20 m2蒸发池的蒸发实测资料分析了各蒸发器间的蒸发特性及其折算系数的年内变化规律,得到了水面蒸发折算系数在非冰期呈逐月增大趋势。同时对各蒸发器蒸发量进行相关性分析,得出20 m2-E601蒸发量相关系数为0.996,20 m2-Φ20 cm蒸发量的相关系数为0.978,两者相关性均显著。该结果可供玛纳斯河流域水量平衡研究、水资源评价和生态需水计算时参考。同时鉴于我国西北干旱地区降水量少、蒸发量大,试验采取在水面覆盖聚苯乙烯泡沫塑料板的方法以便减少水面蒸发。研究表明:5-11月份水面平均蒸发消减率可达51.25%。这为干旱区水资源高效利用提供了理论依据。     

不同蒸发计算方法对水文过程模拟影响的分析

为研究不同蒸发输入对流域水文模拟的影响,以印江河流域印江水文站以上集水区域为对象,将蒸发站蒸发皿实测资料和P-M公式计算的参考作物蒸散发作为模型蒸发输入,应用于垂向混合产流模型进行日径流过程模拟。研究结果表明,以P-M公式计算的参考作物蒸散发为蒸发输入的垂向混合产流模型,其模拟精度总体上要高于以蒸发皿实测蒸发为输入的模拟精度,能够更合理地模拟印江河流域的日径流过程。