于桥水库藻类群落演替过程及影响因素

解析湖库藻类群落演替过程及影响因素对于湖库富营养化控制具有重要作用,而当前我国大部分湖库缺乏历史藻类群落监测数据.为研究典型水库藻类群落演替过程及主要驱动因素,在于桥水库采集沉积物柱芯,采用137Cs定年和藻类色素反演的方法,重建了于桥水库藻类群落近80年历史演替过程,揭示了气候变化和人类活动对藻类群落演替的影响规律.结果表明:①于桥水库历史主要藻类为绿藻、蓝藻、隐藻、甲藻、硅藻和裸藻,藻类群落演替经历了3个阶段,第Ⅰ阶段为1938—1958年,藻类生物量较低;第Ⅱ阶段为1958—1983年,藻类生物量逐渐升高;第Ⅲ阶段为1983—2019年,藻类生物量显著增长,主要以蓝藻和绿藻为优势种.②1959年建库后水动力条件改变导致藻类群落显著变化,藻类生物量和多样性增加;20世纪80年代开始流域营养物负荷提高导致藻类生物量显著升高.③1951年以来气象资料时段的相关分析显示,TP含量、气温与藻类色素含量具有显著相关性（P < 0.05）,表明TP负荷增加和气候变暖对藻类群落演替和生物量增加起到显著促进作用.      

山地梯田景观的灾害防御机制与效益分析——以紫鹊界梯田为例

湖南新化县紫鹊界梯田于2005年12月被国务院确定为第六批国家重点风景名胜区之一,梯田坡度在25~40°,共500余级,10万多丘。分析其生态与社会条件表明,紫鹊界梯田之所以可持续利用的灾害防御机制是:发挥了稻田“隐形水库”的集雨功能,趋利避害;分级截流分散蓄水,实现了区域内水资源的重新分配;传统耕作维护了梯田结构。与水平双季稻田相比,该梯田提高了截水量和光能利用率,延长了农闲蓄水时间。     

三峡库区高阳镇塌岸探讨及其防护

随着三峡库区蓄水及移民迁建工程实施，库岸防护问题尤其是城镇库岸防护问题变得日益突出，以湖北兴山县高阳镇为例，探讨该段岸坡变形破坏的特征及其形成原因，并进行了塌岸预测，最后就其防护治理设计提出了以浆砌石护坡与抗滑桩结合的综合治理措施。     

珊溪水库地震震后趋势的快速判定

2002年7月28日珊溪水库库区发生了M_L3.5地震,之后记录到M)L≥1.0地震50余次,最大地震是9月5日M_L3.9地震。7月28日M_L3.5地震发生后,应用“跟踪式后续地震的模糊预测方法”进行了震后趋势跟踪预测。首先,选用多个地震序列资料作为样本,按预测要求,确定震级大小的分类标准,构成分类矩阵,然后,计算每个序列的6项地震活动性指标构成样本矩阵,而用刚刚发生的地震序列构成待判矩阵,应用一种模糊软聚类方法进行判断,得到未来某一时间段内将发生的地震震级属于哪一类。如果使用几个时间段资料、对不同预报期分别建立几组样本矩阵和分类矩阵,则可实现跟踪式震后趋势快速预测。对9月5日M_l3.9地震和震后趋势预测比较准确。本文简单介绍了预测方法和预测效果。     

三峡库区泥石流活动发展趋势的分析预测

三峡水库135m高程蓄水将近，库区泥石流活动对城、镇、移民新村的安全问题备受政府关注。2009年水库175m水位蓄水后，泥石流活动的发展趋势如何?对三峡库区蓄水前、后泥石流环境的变化特点，特别是蓄水后库岸再造过程对泥石流活动的影响，库区工程建设中人类不合理活动可能形成的人为泥石流等因素作了较全面的分析，提出了库区泥石流活动发展趋势的11项预测结果和一点建议，供有关部门讨论和实施库区地质灾害防治规划参考。     

APPLICATION OF THE HEC-4 MONTHLY STREAM FLOW SIMULATION MODEL1

ABSTRACT: The HEC-4 monthly stream flow simulation model, developed by the Hydrologic Engineering Center, Davis, California, is used to extend the available historical stream flow records in the Central Ohio area. The principal objective of this paper is to examine the effectiveness of the HEC-4 model in generating synthetic monthly flows. Important statistical parameters are evaluated in order to relate the statistical properties of the historical and generated flows. In doing so, it is observed that the mean, standard deviation, and skewness of the generated flows are consistently larger than the corresponding estimates based on historical flows. However, results show that these statistics, as well as the lag-1 serial correlation, are generally well maintained by the generated sequences. The degree to which any statistical dissimilarities would be critical, from an engineering design point of view, is demonstrated by utilizing their low flow characteristics. Estimates of reservoir safe-yields, based on a nonsequential mass-curve analysis of the historical and generated low flows, indicate a nominal difference in this particular study.     

RESERVOIR SEDIMENTATION AND ITS CAUSES IN ILLINOIS1

ABSTRACT: During the years 1930 to 1978 a research program has been carried out in Illinois dealing with reservoir sedimentation. Detailed surveys have been made on 107 lakes. A generalized graph allows annual reservoir capacity loss in percent to be estimated based on size of watershed, lake capacity, and watershed ratio. For the 258 square miles of land on the watershed of Lake Springfield, complete soil maps were measured using a graphic digitizer. A computer readable map was produced. The Universal Soil Loss Equation was solved to provide upland soil losses for each acre of the watershed. Average watershed soil loss was 3.96 tons per acre per year, and 24 percent of this was delivered to the lake.     

A QUASI-LINEAR SPATIALLY DISTRIBUTED CELL MODEL FOR THE SURFACE RUNOFF SYSTEM1

ABSTRACT: The paper presents a spatially distributed model consisting of cells that are interconnected in a pattern similar to the major drainage network of the watershed. Each cell receives as input the rainfall excess for the area represented by the cell as well as inflows from cells located upstream. Outflow from the cell is derived by routing the total input through the cell assuming it to be a linear reservoir during the storm. The time constant of the cells is however allowed to vary from storm to storm so that the model may be described as a quasi-linear model. The model was tested with rainfall excess and direct surface runoff data available for a medium size watershed with satisfactory results. The time constant was found to be related to the rainfall excess of the storms studied, its value decreasing with the increase in the total rainfall excess.     

IMPLEMENTATION OF AN OPTIMIZATION MODEL FOR OPERATION OF A METROPOLITAN RESERVOIR SYSTEM1

ABSTRACT: A deterministic dynamic programming optimization model with a refining sectioning search procedure is developed and implemented to find least cost withdrawal and release patterns for water supple from a multiple reservoir system serving a metropolitan area. Applications are made to teh four reservoir system operated by the city of Dallas, Texas. A realistic cost structure, including nonlinear power consumption, block rate unit power costs, and flow dependent power consumption for intracity water distribution, is utilized. Applications are made to find least cost operating patterns and, as well, by inclusion of a water loss penalty function, supply patterns which will reduce evaporation water losses for the Dallas system.     

LEAF LITTER BREAKDOWN IN A RECENTLY IMPOUNDED RESERVOIR1

ABSTRACT: The impoundment of Richard B. Russell Lake resulted in the inundation of 3490 ha of forested area or 33 percent of the total area of the lake. Estimates of the total inundated leaf litter biomass were combined with a leaf litter decomposition study to determine the nutrient load and dissolved oxygen demand to the reservoir. Hickory leaf bags broke down most rapidly at the 3-m and 28-rn depths, followed by short-needle pine, white oak, a hardwood litter mixture, beech, and red oak. Leaf bags incubated at the 3-m depth exhibited significantly higher breakdown rates than those at the 28-m depth for most leaf types, due to differences in dissolved oxygen and temperature. Respiration rates of litter were also higher at the 3-m depth. Most leaf types accumulated nitrogen and phosphorus and lost organic carbon after an initial leaching period. Richard B. Russell Lake exhibited extensive anoxia and the buildup of total organic carbon, nitrogen, and phosphorus during summer stratification. Leaf litter breakdown accounted for 64 percent of the organic carbon increase but acted as a sink for nitrogen and phosphorus. The dissolved oxygen demand of the litter accounted for over 50 percent of the demand incurred in the lake.