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671.
Balram Panigrahi Sudhindra N Panda Bimal Chandra Mal 《Resources, Conservation and Recycling》2007,50(4):459-474
Hydrologic and economic analysis of the on-farm reservoir (OFR) was carried out in rainfed rice–mustard cropping systems in Eastern India followed by 2 years of field experiments in 1999 and 2000. The average contribution (average of 2 years) of direct rainfall and surface runoff from the diked crop fields contributed, respectively, about 79.5 and 20.5% to the total OFR inflow. The average contribution of evaporation loss, seepage and percolation loss and supplemental irrigation from the OFR contributed, respectively, about 10.0, 31.2 and 58.8% to the total OFR outflow. There was an average increase of rice yield of 44.0% over the rainfed rice because of application of 8.4 cm supplemental irrigation from the OFR. Thus, with an application of 4.5 cm supplemental irrigation from the OFR, 15.40% increase of mustard yield was recorded in 1999. Economic analysis indicated average net profit of Rs. 700 (US$ 1 = Rupees (Rs.) 44.75 in Indian currency) from a farm area of 800 m2. Average values of benefit–cost ratio, internal rate of return and pay back period of the OFR irrigation system were evaluated as 1.17, 14.8%, and 16 years, respectively. The study reveals that the OFR irrigation in small landholders is economically feasible system for rainwater harvesting and providing supplemental irrigation in rainfed farming system. 相似文献
672.
山西省地质旅游资源丰富,不同地域分布着各具特征的地质景观。地质旅游资源特征明显、种类繁多,蕴藏着巨大的旅游潜力。在认真探讨各类地质景观分布特征的基础上,针对这些资源的开发现状和保护程度,提出了该省地质旅游线路规划、资源开发规划及地质旅游区的环境治理和保护规划方案。 相似文献
673.
674.
Strongly decreasing atmospheric emissions and acidic deposition during the 1990s have initiated chemical reversal from acidification
in several drinking-water reservoirs of the Erzgebirge, SE Germany. We studied responses of phytoplankton, zooplankton and
fish stocks in five reservoirs and at enclosure scale after experimental neutralization of 1,200 m3 of lake water. About 4 months after this treatment, diatoms and cryptomonads replaced the predominating chrysophytes and
dinoflagellates. The colonization by acid-sensitive species of green algae, cryptomonads, rotifers and Cladocera (e.g. Bosmina longirostris) is explained by the occurrence of dormant stages or by survival of individuals in very low abundances. Analogous to the
enclosure experiment, three reservoirs showed significantly (p < 0.01) falling trends of chlorophyll a and phytoplankton biovolume, mainly due to the decline of dinoflagellates. Picoplankton and diatoms increased slightly in
two reservoirs. The zooplankton communities were dominated by rotifers and small Cladocera. Representatives of the genus Daphnia were lacking. Two reservoirs were re-colonized by zooplanktivorous fish populations of either perch (Perca fluviatilis) or sunbleak (Leucaspius delineatus). The latter exhibited extremely high fluctuating abundance and biomass and even suffered from a population crash. This natural
mortality was caused by a limited food supply. Hence, severe top-down control may delay the recovery of larger zooplankton
species like daphnids. Fishery management comprising the introduction of predatory fishes can help to control zooplanktivorous
fish populations and to prevent their mass mortality. 相似文献
675.
John A. Gordon 《Journal of the American Water Resources Association》1989,25(1):187-192
ABSTRACT: Stratified reservoir waters frequently contain objectionable quantities of dissolved manganese. The oxidation and removal of dissolved manganese during transport below Normandy Dam, Tennessee, was shown to be much more rapid than expected from chemical oxidation. Oxidation took place in only a day of travel time rather than months or years. Laboratory studies showed that removal was associated with a slime found on rock surfaces below the dam and led to the development of column technology as a possible method of treating natural waters containing manganese. Hydraulic loadings on the columns in the range of 390–780 m3/hr.ha accomplished a 90 percent removal rate of soluble manganese over an influent concentration range of 2 to 15 mg/l. 相似文献
676.
Hasan Yazicigil Mark H. Houck 《Journal of the American Water Resources Association》1984,20(3):417-424
A chance-constrained linear programming model, which utilizes multiple linear decision rules and is useful for river basin planning, is used to evaluate the effects of risk and reliability on optimal reservoir design. Streamflow forecasts or predictions can be explicitly included in the linear program. The risk associated with the predictions is included in the model through the use of cumulative distribution functions (CDF) of streamflows which are conditioned on the predictions. A multiple-purpose reservoir on the Gunpowder River in Maryland is used to illustrate the effectiveness of the model. In order to provide the decision makers with complete and useful information, trade-off curves relating minimum reservoir capacity (a surrogate for dam costs), water supply and flood control targets, and the reliability of achieving the targets are developed. The trade-off curves may enhance the decision maker's ability to select the best dam capacity, considering technological and financial constraints as well as the trade-offs between targets, risks, and costs. 相似文献
677.
入世后三峡库区的可持续发展研究 总被引:6,自引:1,他引:5
随着三峡工程的兴建,三峡库区的发展基础发生变化,库区的产业结构必然地要有所调整。百万移民促进新的城镇体系的建立。加入WTO对三峡库区的发展产生新的冲击,库区产业结构必须进一步调整。以大力发展林业为主,其次加强牧业的发展,再次大力发展水产养殖业,加强旅游业的发展,最后合理调整农业产业结构,同时要合理调整城镇体系。根据三峡工程和入世对库区的影响,提出三峡库区可持续发展的措施,建议:(1)以市场为导向,立体开发,提高资源利用率和商品率,确可经济的发展;(2)提高人才素质;(3)培养人们的生态价值观;(4)引进先进的科学技术,加强管理、环境保护和生态修复。 相似文献
678.
宋发新 《长江流域资源与环境》1995,4(1):18-23
库区经济发展是三峡工程移民能否长治久安的核心问题。三峡湖北库区地处三峡工程坝区库首的特殊位置,其经济发展战略必须立足于服务三峡工程,抓住四大机遇,开发当好资源,妥善安置移民,促进协调发展,战略目标分三阶段实施,提出了实现战略目标的基本对策。 相似文献
679.
James F. Booker 《Journal of the American Water Resources Association》1995,31(5):889-906
ABSTRACT: A severe sustained drought in the Colorado River Basin would cause economic damages throughout the Basin. An integrated hydrologic-economic-institutional model introduced here shows that consumptive water users in headwaters states are particularly vulnerable to very large shortfalls and hence large damages because their rights are effectively junior to downstream users. Chronic shortfalls to consumptive users relying on diversions in excess of rights under the Colorado River Compact are also possible. Nonconsumptive water uses (for hydropower and recreation) are severely affected during the worst drought years as instream flows are reduced and reservoirs are depleted. Damages to these uses exceeds those to consumptive uses, with the value of lost hydropower production the single largest economic impact of a severe sustained drought. Modeling of alternative policy responses to drought suggests three general policy approaches with particular promise for reducing damages. Consumptive use damages can be reduced by over 90 percent through reallocation from low to high valued uses and through reservoir storage strategies which minimize evaporation losses. Reservoir management to preserve minimum power pool levels for hydropower production (and to maintain reservoir recreation) may reduce damages to these nonconsumptive uses by over 30 percent, but it may increase consumptive use shortfalls. 相似文献
680.
Khalid Karim Maureen E. Gubbels Ian C. Goulter 《Journal of the American Water Resources Association》1995,31(6):1063-1077
ABSTRACT: A critical examination of the techniques used to assess and specify environmental instream flow requirements is provided. The strengths and weaknesses of individual techniques are evaluated on both an absolute and a comparative basis. Particular attention is given to the problem of specifying environmental flow requirements in Australia where the hydrology has distinctly different characteristics to those in countries where most of the models for prediction of instream flow requirements were developed. Broad recommendations as to the suitability and use of the different techniques for different conditions are provided. 相似文献