REUSE OF DOMESTIC WASTEWATER FOR IRRIGATION IN ARID ZONES: A CASE STUDY1

ABSTRACT: The domestic sewage of the city of Beer-Sheva, Israel, which is located in an arid region, is treated in a series of facultative ponds. The treated effluent is stored temporarily in an open surface earthen reservoir (about 0.5 ± 10⁶ m³ in volume) and then used for irrigation. The effluent is applied via sprinkler and trickle irrigation systems. The main crops irrigated are cotton, wheat, alfalfa, and corn. Total cotton yield is over 5500 kg/ha, and the wheat grain yield is over 7500 kg/ha. The amount of effluent applied is about 6500 m³/ha for cotton (including preplant irrigation), and the wheat receives about 4500 m³/ha via irrigation and an additional 2000 m³/ha from precipitation. Due to the nutrient content in the effluent, the above yields are obtained without any additional fertilization.     

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.     

MITIGATING IMPACTS OF A SEVERE SUSTAINED DROUGHT ON COLORADO RWER WATER RESOURCES1

ABSTRACT: We evaluated the effects of institutional responses developed for coping with a severe sustained drought (SSD) in the Colorado River Basin on selected system variables using a SSD inflow hydrology derived from the drought which occurred in the Colorado River basin from 1579–1616. Institutional responses considered are reverse equalization, salinity reduction, minimum flow requirements, and temporary suspension of the delivery obligation of the Colorado River Compact. Selected system variables (reservoir contents, streamflows, consumptive uses, salinity, and power generation) from scenarios incorporating the drought-coping responses were compared to those from Baseline conditions using the current operating criteria. The coping responses successfully mitigated some impacts of the SSD on consumptive uses in the Upper Basin with only slight impacts on consumptive uses in the Lower Basin, and successfully maintained specified minimum streamflows throughout the drought with no apparent effect on consumptive uses. The impacts of the coping responses on other system variables were not as clear cut. We also assessed the effects of the drought-coping responses to normal and wet hydrologic conditions to determine if they were overly conservative. The results show that the rules would have inconsequential effects on the system during normal and wet years.     

我国北方稻区稻飞虱的成灾机制：一个假说

本文通过对大量文献资料的综合分析，从飞虱的飞行特性和北迁运载气流入手，以东亚大气低层环流为背景审视飞虱在有限时间内远迁北方致灾的成因机制，提出了以北上低空急流的时空变化与南方大发生虫源迁出期（区）相吻合、其前沿所至与北方迁入区相一致作为北方稻虱成灾的启动因子的假说．并提出了验证该假说的研究方法和技术路线，为揭示北方稻虱成灾的奥秘，完善灾变监测技术和预警系统奠定了基础。     

PULSED TRICKLING EFFECTS ON SOIL MOISTURE DISTRIBUTION1

ABSTRACT Laboratory experiments were conducted to study effects of trickle emitter discharge rate on the distribution of soil moisture in a silty-clay loam soil. Both pulsed and continuous irrigation treatments were studied. A simulation model was used to evaluate the results obtained in the laboratory. The agreement between the predicted and measured soil moisture distribution patterns was quite good. For both pulsed and continuous applications, increasing trickle discharge rate resulted in a decrease in the horizontal component and an increase in the vertical component of the wetted soil profile. Compared to the continuous treatments, pulsed applications resulted in significant reduction in water loss below the root zone. Pulsed applications rates can replace continuous small discharge rates to reduce irrigation water runoff problems on heavy soils and with restricted infiltration allow the use of larger emitter orifices to decrease potential clogging of the trickle system.     

THE IMPORTANCE OF INSTITUTIONAL STRUCTURE IN CONTROLLING AGRICULTURAL RUNOFF1

Abstract: Agricultural runoff, such as dissolved mineral salts and selenium, creates pronounced downstream impacts to agricultural producers and to wildlife. The ability to manage these problems efficiently depends critically on the institutional pricing structure of irrigation water delivery agencies. An important characteristic of irrigation water delivery is whether irrigators pay per unit of water received or make one payment regardless of the quantity of water received. In this study we compare the effectiveness of agricultural runoff reduction policies in two regions that employ these different water pricing structures. We find that reduction policy is more effective and can be achieved at a lower cost when water is priced on a per unit basis and that growers have greater incentive to act on their own to reduce runoff problems. Operating under a per unit pricing system encourages water conservation and runoff reduction, which creates public benefits that are not achieved under the single-payment, fixed allotment method of irrigation water delivery.     

四川省区域经济不平衡发展特征分析

以地市州为基本经济单元,以1999年主要相对指标为依据,通过综合值测算法,将全省划分为四类经济发展水平不同的地区,对四类地区平均总量指标、相对指标进行了对比分析,并揭示了其空间分布特征,简要分析了各类地区经济发展的条件和方向;以1999年、1978年各地市州GDP为例,对比分析了四川省区域经济不平衡发展的动态性特征。     

三论灾害研究的理论与实践

在作者分别于 1991年发表的《论灾害研究的理论与实践》和 1996年发表的《再论灾害研究的理论与实践》的基础上 ,评述了最近 6年来灾害科学研究的进展 ,提出了灾害科学的基本框架 ,进一步完善了“区域灾害系统论”的理论体系 ,提出了当前灾害科学的主要学术前沿问题。文章并就资源开发与灾情形成机理与动态变化过程进行了综合分析 ,阐述了区域灾害的形成过程 ,进一步从区域可持续发展的角度 ,就建设安全社区 (区域 )提出了“允许灾害风险水平”的区域发展对策。     

MULTIOBJECTIVE DECISION MAKING TECHNIQUES FOR RESERVOIR OPERATION1

ABSTRACT: Six applications of multiobjective decision making techniques for finding optimal or satisfying operating rules for reservoir systems are presented. The examples include situations with hydropower vs. water supply (for irrigation), flood control vs. low flow augmentation, selection of an operating rule, low-flow vs. reliability, and low flow and recreation vs. water quality. The techniques applied include the constraint method, compromise programming, goal programming, Tchebycheff approach (max-mm), Consensus, and ELECTRE I and II.     

长江口地区的盐水入侵灾害及变化趋势

本文在总结长江口地区现状盐水入侵时空变化规律的基础上,着重分析了在未来海平面上升、长江东线南水北调和三峡水利枢纽工程以及长江口北支综合整治等因素影响下,南支河段盐水入侵强度的变化趋势。