O&M SPENDING LEVELS IN THIRD WORLD IRRIGATION SYSTEMS: EXPLORING ECONOMIC ALTERNATIVES1

ABSTRACT: Third World irrigation and drainage systems have experienced major declines recently in both capability and performance. This is due initially to working them well beyond their design capaci-capacities; scouring, sedimentation, and overtopping result. Chronic O&M underfunding then adds heavily to this worsening malaise. International donors have assisted irrigation departments with rehabilitation projects and programs to improve O&M effectiveness on a grand (billions of dollars) scale. Despite their historical propensity to examine, almost fastidiously, program economic justifications (B/C, IRR, etc), the donors apparently have glossed over two basic analytic elements for (a) more spending on O&M as distinct from an equivalent spending on other means to provide farmers with an m³ of water; and (b) different levels of O&M spending on canals and drains. Surely those different levels provide differing benefits, in total, and at the margin. Which level is most economic? This paper identifies these latter analytical issues, posits methodologies key to an O&M spending level analysis, and discusses the information base. Particular attention is paid to identifying relevant costs and benefits, and to suggesting supplementary criteria for O&M spending level selection. The paper is an exercise in delineation of an imminently practical area of irrigation engineering economics.     

Purification and characterization of extracellular poly(3-hydroxybutyrate) depolymerases

Five extracellular PHB depolymerases of bacteria isolated from various sources were purified to electrophoretic homogeneity and compared with known extracellular PHB depolymerase fromAlcaligenes faecalis T1. The molecular mass of these enzymes were all around 40–50 kDa. Nonionic detergent, diisopropylfluorophosphate and dithiothreitol inhibited the PHB depolymerase activity of all these enzymes. Trypsin abolished PHB depolymerase activity, but not theD-3-hydroxybutyric acid dimer hydrolase activity of all the enzymes. These results showed that the basic properties of these PHB depolymerases resemble those of theA. faecalis T1 enzyme. Analysis ofN-terminal amino acid sequence of the purified enzymes revealed that these enzymes includingA. faecalis T1 enzyme fall into three groups.     

关于职工情境意识的研究综述

对情境意识的定义、活动机制、测量方法及强化方法等进行了述评。分析了关于情境意识研究的问题及趋势。     

五氯酚对环境污染及居民健康影响研究

中国长期以来使用五氯酚纳盐杀灭亡血吸虫的中间宿主──—钉螺．为评价它对环境的污染及居民健康危害，１９９０－１９９３年在我省开展了五氯酚环境污染及对居民健康影响研究．在研究区采集环境样品（空气、水体、土壤及底泥、蔬菜、肉、蛋、鱼等）共１７３份；生物材料（人血、尿）共４５７份，分析五氯酚浓度．结果在明，在五氯酚使用区，环境中ＰＣＰ浓度稍高于对照区，而生物材料尿、血中ＰＣＰ浓度明显高于对照区．全血胆碱脂酶活性用药区明显低于对照区，统计学分析有显著差异（Ｐ＜０．００１），证实了长期低剂量使用可造成环境及生物蓄积．     

AAS与ICP－AES间接测定天然水中硫酸盐

本文以与过量形成ＢａＳＯ＿４沉淀反应为基础，较详细地讨论了反应条件、从而拟定了用ＡＡＳ和ＩＣＰ－ＡＥＳ间接测定天然水中的方法、确定了方法的精密度，ＡＡＳ法的ＲＳＤ％为１．５，ＩＣＰ－ＡＥＳ法为３．２．两种方法对比分析的结果接近，误差为１．０％（相对）。用于天然水中的测定，获得满意的结果。     

Disturbance of natural vegetation by camping: Experimental applications of low-level stress

Previously undisturbed sites in four different vegetation types were camped on for one night and for four nights. Changes in vegetation cover and vegetation height were measured after camping and one year later. Results are presented separately for different campsite zones—parts of the site where campers slept, cooked meals, and stored their packs. Just one night of camping was sufficient to cause evident impact in all four vegetation types, although the amount of impact varied significantly between zones and between vegetation types. Vegetation impact on campsites used four nights was generally less than twice as severe as impact on the sites used one night. The effects of camping on vegetation were also predicted for 12 other vegetation types on the basis of vegetational responses to experimental trampling. These results suggest that impact can almost always be minimized by confining camping to a small number of campsites instead of dispersing use across many campsites.     

基于GIS的汕头市城市综合防灾系统的研究方案及实施框架

在研究汕头市地震、风、洪潮、火等多种灾害的危险性、成灾模式和损失估计的基础上,应用地理信息系统(GIS)技术建立可视化的计算机综合防灾系统,可以提高城市的防灾能力。本文针对基于GIS的城市综合防灾系统的建立,提出了较为具体的研究方案和实施框架,便于课题组各项研究工作的开展和统一。     

FACTORS CONTROLLING RUNOFF NUTRIENT LOSS FROM CULTIVATED LAND IN EASTERN SOUTH DAKOTA1

ABSTRACT A stepwise multiple regression was used to evaluate the relative importance of antecedent-, event-, and high-intensity-precipitation amounts; runoff volume; and precipitation nutrient contents and concentrations in determining nutrient losses in runoff. Plots were fertilized at high, medium, and low rates and had cultivation ridges oriented up-and-down slope or on the contour. Runoff volume was the important factor in determining the loss of NO₃, soluble PO₄, total PO₄, and soluble K ions in runoff from fallow, corn, or soybean plots. NH₄-N loss was controlled mainly by the precipitation content and antecedet precipitation since fertilizer had been applied. Nutrient losses were greater from plots fertilized at the high rate and from plots with cultivation ridges oriented up-and-down slope rather than on the contour.     

Development of a bird integrity index: using bird assemblages as indicators of riparian condition

We describe the development of a bird integrity index (BII) that uses bird assemblage information to assess human impacts on 13 stream reaches in the Willamette Valley, Oregon, USA. We used bird survey data to test 62 candidate metrics representing aspects of bird taxonomic richness, tolerance or intolerance to human disturbance, dietary preferences, foraging techniques, and nesting strategies that were affected positively or negatively by human activities. We evaluated the metric responsiveness by plotting each one against a measure of site disturbance that included aspects of land use/land cover, road density, riparian cover, and stream channel and substrate conditions. In addition, we eliminated imprecise and highly correlated (redundant) metrics, leaving 13 metrics for the final index. Individual metric scores ranged continuously from 0 to 10, and index scores were weighted to range from 0 to 100. Scores were calibrated using historical species information to set expectations for the number of species expected under minimally disturbed conditions. Site scores varied from 82 for the least disturbed stream reach to 8.5 for an urban site. We compared the bird integrity index site scores with the performance of other measures of biotic response developed during this study: a fish index of biointegrity (IBI) and two benthic macroinvertebrate metrics. The three assemblages agreed on the general level of disturbance; however, individual sites scored differently depending on specific indicator response to in-stream or riparian conditions. The bird integrity index appears to be a useful management and monitoring tool for assessing riparian integrity and communicating the results to the public. Used together with aquatic indicator response and watershed data, bird assemblage information contributes to a more complete picture of stream condition.