ALTERNATIVE APPROACH TO THE FORMULATION OF BASIN HYDRAULIC GEOMETRY EQUATIONS1

ABSTRACT: Along a drainage network, there is a systematic variation of average flow parameters (width, depth, and velocity) at flows having the same flow duration. Hydraulic geometry equations mathematically express this interdependent relationship of stream-flow characteristics for a basin for annual flow durations varying from 10 to 90 percent. However, the equations proposed so far have had rather poor predictive performance for low flows. An independent investigation of the variation of discharge with drainage area and annual flow duration demonstrates a consistent relationship between these parameters. The relationship for the high to median-flow range differs, however, from that for the median— to low-flow range. The proposed equations provide a better predictive performance for low flows than previous formulations and a versatile means of estimating flow parameters for streams throughout a basin. The improved basin hydraulic geometry equations have a wide range of applications in areas such as stream habitat assessment, water quality modeling, channel design, and stream restoration projects.     

MODELING PERCOLATION LOSSES FROM A PONDED FIELD UNDER VARIABLE WATER-TABLE CONDITIONS1

ABSTRACT: A numerical simulation model was developed to predict the vertical and lateral percolation losses from a ponded agricultural field. The two-dimensional steady-state unsaturated/ saturated flow equation was solved using the finite-difference technique. A constant ponding depth was maintained at the soil surface with different water table conditions in an application of the model for rice fields bordered by bunds. Field experiments were conducted for two different water table depths to collect data on the spatial distribution of volumetric soil-moisture content for model verification. The measured soil-moisture content values were found to be in close agreement with those predicted by the model. The sensitivity analysis of the model with selected hydrologic conditions shows that the model is most sensitive to the values of saturated hydraulic conductivity, but relatively less sensitive to water table depth, ponding depth, and evaporation rate from the soil surface. It implies that, in a ponded rice field condition, the lateral and vertical percolation losses are mostly governed by the hydraulic conductivity of the soil. The vertical percolation losses were almost equal to the saturated hydraulic conductivity values and, in most cases, these losses increased with deeper water table depths. The lateral percolation losses also increased with deeper water table depths; however, these losses were relatively small in comparison to the vertical percolation losses. The vertical and lateral percolation losses increased with the increase in ponding depths. The lateral percolation losses through the bund decreased when the evaporation losses increased from the soil surface. The results of this study indicate that the percolation losses from a ponded field may be predicted accurately for a wide range of soil and hydrological conditions when the values of hydraulic conductivity, evaporation rate, depth of ponding, and water table depth are accurately known.     

对水工构筑物设计的几点看法

探讨了水工构筑物设计中的地下水位确定、伸缩缝设置、总体布置及设计与施工配合等问题。设计在满足国家有关政策、规范要求的同时,要做到技术先进、安全适用、经济合理。     

水力喷淋式凉水塔在初冷循环冷却水系统中的应用

介绍了喷淋式凉水塔结构、工作原理及冷却效果的影响因素.与机械通风式凉水塔的冷却效果比较表明,该凉水塔具有冷却效率高、运行成本低、操作简单等优点,值得推广应用.     

SBAR中好氧污泥颗粒化及其特性

采用气升式内循环间歇反应器对好氧污泥颗粒化的过程进行了研究,考察了不同水力循环时间下好氧污泥颗粒化过程及其特性,并且对反应器中形成的好氧颗粒污泥内部菌群形态进行了描述.结果表明,不同水力循环时间对好氧颗粒污泥生长特性产生了很大的影响,在较短水力循环时间下,颗粒污泥粒径增长速度快,形成的颗粒粒径多数在 1.0～2.0mm 之间,并且 VSS含量达 92.08%,强度也较高,而在较长水力循环时间中形成的颗粒粒径在 0.5～1.0mm 之间、VSS 含量在 83.92%,污泥强度下降.     

水雾灭火系统的设计

以自备发电机房的灭火设计为例,介绍了水雾灭火系统的实现方法和设备选型步骤,提出提高水雾灭火系统的实现方法和设备选型步骤,提出提高水雾灭火系统的性能和灭火效率,有赖于火灾科学基础研究的积累和突破。     

絮凝DAF中试工艺处理密云水库低温低浊水的影响因素

系统研究以硫酸铝和聚铝为絮凝剂时絮凝-DAF工艺中的水力学参数对除浊率的影响 .结果表明聚铝表现出了更优越的参数值 .在凝聚段 ,聚铝需要的高速混合时间为 15s,而硫酸铝则为 30s以上 ,2者对混合强度的要求为G=300～1000s^-1.聚铝的絮凝反应时间为 5.0min以上 ,硫酸铝为 7.5min以上 ,而且搅拌强度范围平均G值 =40～140s^-1;确定合适的总平均GT值≥2×10⁴.当应用聚铝为絮凝剂时 ,可以采用两级或三级等速搅拌 .对于仿MJ型的释放器 ,在实验的范围内释气压力为 2.5～3.3kg/cm² 时 ,5.0 %～8.3%的回流比较合适 .气浮接触区的水力条件和停留时间对絮凝气浮的除浊效果有较大的影响 .     

高应变率环境下材料的失效机理研究

采用双层约束爆炸方法对高应变率环境下材料的失效模式及其影响因素进行了研究。结果表明：材料存在拉伸断裂和绝热剪切断裂两种模式。碳含量越高,材料对绝热剪切越敏感;同种材料的淬、回火类组织比正火类组织绝热剪切敏感性高。材料的屈导比哕决定了材料的失效模式,哕越大,材料越倾向于以绝热剪切模式失效。     

沸石生物滴滤器处理分散式生活污水的性能及生物膜特征

构建沸石生物滴滤器处理农村生活污水,研究了滴滤器的挂膜启动特征、进水水力负荷对滴滤器处理生活污水性能的影响.滴滤器采用连续进水的方式挂膜,挂膜26d后,COD和氨氮去除率分别达到85%和68%以上,且COD和氨氮相邻两次监测结果的相对偏差均低于10%,表明滴滤器挂膜成功,并基本达到了稳定的运行状态.滴滤器表现出对进水水力负荷变化较强的适应性,水力负荷为300L/（m²·d）时,滴滤器对COD、氨氮、TN、TP的平均去除率分别达到90.8%、87.1%、67.2%、90.1%.滴滤器对有机物和氮磷的去除途径结果表明,微生物降解和转化作用对污水中COD、氨氮、TN的去除贡献率最大,填料的吸附则是TP去除的主要途径,铁屑的氧化是影响填料吸附去除TP的重要因素.生物量及生物膜的分布特征表明,滴滤器内生物膜中细菌的多样性十分丰富.