涝渍地暗管排水示范工程建设有关问题研究

结合中日专项技术合作四湖项目的具体实践,指出了暗管工程规划中排水调查的内容和重点,就如何评判暗管排水的必要性和确定暗管设计排水量进行了探讨,分析了暗管排水与规划单元排灌系统的关系。排水调查是农田基本建设实施过程中不可缺少的一个环节,就涝渍地治理改造而言,调查的重点是要弄清排水不良的原因和取得解决问题的基础资料。为了制定符合实际的农田排水规划实施方案,可从土壤类型、土壤承载力、降雨后地表积水状况、土壤透水性和地下水位等对规划单元内的农田是否需要暗管排水作出判断。对水田而言,在田面水排除后,领先暗管要排除地表残留水和过剩的土壤重力水,据此决定暗管设计排水量。对于旱田,渗入土壤中以重力水存在的过乘水需要通过暗管排除,据此决定暗管设计排水量。暗管工程适于江河中下游地势低洼、排水不良的农田,当明排不能有效地降低地下水位满足作物生长时,有必要采取暗管排水。     

Environmental Impacts of the Akosombo Dam and Effects of Climate Change on the Lake Levels

The Akosombo dam was constructed on the Volta river primarily for the generation of hydropower. The resultant Volta lake which was formed between 1962 and 1966 in Ghana will probably long be one of the greatest man-made lakes. It produces 912MW of electricity at its maximum operating capacity. The Akosombo hydroelectric project (HEP) was meant among others to open up Ghana to rapid industrialization and hence modern development. Other positive impacts of the HEP include fishing, farming, transportation and tourism. However, there are equally negative impacts, some of which the project did not envisage and these are felt on the physical, biological and human subsystems within the immediate project environments and places much more distant from them. Recently, there have been declines in the lake levels resulting most probably from inadequate rainfall and/or runoff from the river catchments that feed the lake, and also from the observed rising temperatures. Comparisons of the runoff from two most important tributaries of the Volta (White Volta and Oti) for two time periods of 1951–1970 and 1971–1990 showed reductions in mean streamflows of 23.1% on the White Volta and 32.5% on the Oti. Similarly, a plot of the mean annual temperatures for the upper Volta basin indicated a 1^C rise in temperature from 1945–1993.     

突发性环境污染事故应急监测准备与响应

突发性环境污染事故具有不确定性，因此要求应急监测准备工作常备不懈；应急监测准备和响应贯穿于事前、事发、事后几个阶段，包括日常准备、应急监测、结果发布、跟踪监测、经验总结等主要环节。     

输电线路建设项目水土保持方案编制的几点认识

针对输电建设项目的特点,阐述了输电线路与一般线形建设项目水土保持方案的不同之处,提出了输电线路水土保持方案编制的程序、内容及方法.     

IRRIGATOR INVOLVEMENT IN THE IMPLEMENTATION OF AGRICULTURAL NONPOINT SOURCE POLLUTION CONTROL PROGRAMS1

ABSTRACT: Recently, Congress designated irrigated agriculture under the “nonpoint source” category, covered by Section 208 of P.L. 92-500 and involves the use of “best management practices.” Generally, the most appropriate solutions for pollution abatement from irrigated agriculture involve the delivery and use of water rather than the treatment of irrigation return flows. 1. Technological alternatives should be utilized that are sensitive to local conditions and acceptable to the farmers. 2. Informational and educational programs to assist farm operators individually and collectively must be instituted prior to the start of the project; imaginatively conceived, and continuously modified and upgraded if motivation for change is to be encouraged. 3. Technical assistance personnel should be given short courses in skills needed for working effectively with irrigators. 4. Communication techniques used for working with farmers as individuals and groups should be designed into the implementation program and evaluated. 5. Credibility and trustworthiness of Federal and state agencies in the eyes of the irrigators provide the important final ingredient in effectively implementing change and reducing nonpoint source pollution from irrigated agriculture.     

IRRIGATION WATER AND SURFACE RUNOFF QUALITY AND QUANTITY IN CARSON VALLEY,NEVADA1

ABSTRACT: Best management practices for irrigated agriculture are not restricted to the control of sediments in the return flow. Salts and nutrient loading and oxygen depletion are also of environmental concern. Since knowledge of waste loading returned from agricultural irrigation is limited, specific characterization of irrigatin and runoff water quality should precede corrective measures. In 1974, 1975 and 1976, four study sites with in a 50,000-acre irrigated area were monitored to characterize the quantity and quality of irrigation water and surface return flow. Simple correlatins among constituents showed strong relationships among BOD, TP, PO₄,-P, and No₃-N. Least significant difference tests among seasonal means of change-in-load per irrigation showed that only TDS and PO₄-P were significant.     

CASE STUDIES OF AGRICULTURAL WATER CONSERVATION1

Farmers from four irrigation districts in Texas and California were questioned about water conservation practices they are now using, those they plan to adopt, and potential incentives that government might offer to induce still further water conservation on their part. While responses differed somewhat from place to place and among individual farmers, the general results were: a) farmers reported that “water conservation” is not new to them, it is something they practice regularly; b) recent innovations such as laser controlled land leveling devices have permitted some substantial water use reductions in recent years; and c) even greater incentive mechanisms that government could provide and that farmers would accept as useful incentives, such as long term low interest loans for water saving equipment, would probably not be able to reduce water use in agriculture much further than 15 percent below current levels. It is recommended nonetheless that Federal agencies and local water districts and individuals should nonetheless pursue water conservation training and education programs, demonstrations of conjunctive use and water banking opportunities for water saving, and increased loan programs for installation of water saving equipment.     

SOCIAL OVERHEAD CAPITAL COSTS OF IRRIGATION DEVELOPMENT IN WASHINGTON STATE1

ABSTRACT: Increased irrigation as a means of achieving economic development can impose significant social costs on the state or region of growth. The growth in population induced by additional irrigation will require new roads, water and sewage facilities, schools, fire and police protection, etc. Also the increased energy demands due to irrigation and growth in economic activity must be met. Capital investments required to service these needs of new development can become very large. This study attempts to measure such social overhead costs or irrigation development for some specific irrigation project areas of Eastern Washington. It is shown that investment costs in overhead items can reach $2,000 per acre irrigated or $70,000 per job created. Alternatively, the annual costs can equal $180 per acre or $6,700 per worker. These costs must be paid locally through increased taxes, utility rates, or costs for services.     

IMPROVING IRRIGATION RETURN FLOW QUALITY WITH A WATER RENTAL MARKET1

ABSTRACT: Current policies for correcting the problem of irrigation return flow pollution tend to attack the symptoms of the problem, rather than its cause. The present institutional arrangement for allocating irrigation water is seen as the source of the problem. This paper examines the water quality benefits of altering the institutional arrangement to allow for irrigation water transfers through a rental market. It is conceptualized that by creating a water rental market an opportunity cost would be associated with the use of irrigation water such that profit maximizing farmers would be induced to use his water supply more efficiently and rent the surplus to other irrigators, thus reducing return flow pollution. It is shown that a water rental market could increase water quality in the Yakima River in southcentral Washington by 31 percent as well as increase farm incomes and crop production.     

DEVELOPING COMPETITION FOR WATER IN THE URBANIZING AREAS OF COLORADO1

ABSTRACT: Rapid population growth in the metropolitan area of Denver, Colorado, is causing conflicts over water use. Two cities, Thomton and Westminster, have begun condemnation proceedings against three irrigation companies to secure agricultural water rights for municipal use. This is the first condemnation proceeding against irrigation water rights for municipal use. Should the suit succeed, over 30,000 acres of presently irrigated land will lose its water supply. There are about four hundred landowners in the area; two hundred of these are commercial farmers, including truck, dairy and specialty farms. Total agricultural production amounts to about $8 million per year. About 561 jobs related to agriculture will disappear along with about $4 million in not income. Only 6.4 percent of the farmland along the Front Range is irrigated. Continued urban growth will put pressure on the water supply of much of this land. The interested parties of the region should cooperate to lessen the impact of urban growth on agricultural lands and water by forming a metropolitan water district. Such a district could share costs of development of additional municipal water and develop systems where municipalities would recycle waste water back to the irrigated lands.