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Muhammad Nawaz Bhutta Muhammad Latif Jacob W. Kijne 《Irrigation and Drainage Systems》1991,5(3):229-247
This study was conducted on Gugera Branch of Lower Chenab Canal, Punjab, Pakistan. Sample distributaries off taking from Gugera Branch were selected for the study. The existing conditions of water distribution among the distributaries were studied. Field data were collected during the whole of 1988. Field observations suggested that the variability at the head of distributaries is much greater than the variability in the Gugera Branch under existing operational practices. The distribution of water among the distributaries is rarely in accordance with design criteria. Some channels get priority over other channels. The annual closure period varied from 17 to 41 days for different channels. The discharge at the head of distributaries remained lower than the standard operational range for 69 to 183 days in a year. The data suggested that a regulating gate at the head of the distributary can reduce discharge variation up to 2.4 times compared with a Karrees System (wooden stop logs used for water regulation). The data indicated that the adjustments in the head gate of a distributary on daily basis can substantially improve discharge conditions at the head of distributary. Rotational schedules are not being followed as per design and need to be improved. Most of the existing head discharge relationships of discharge measuring structures are not reliable. A frequent calibration of these structures is recommended. 相似文献
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M. ŘÍHA J. KUBEČKA M. PRCHALOVÁ T. MRKVIČKA M. ČECH V. DRAŠTÍK J. FROUZOVÁ E. HOHAUSOVÁ T. JŮZA M. KRATOCHVÍL J. PETERKA M. TUŠER M. VAŠEK 《Fisheries Management and Ecology》2011,18(4):339-347
Abstract Diel changes in littoral fish assemblage were studied in four reservoirs in the Czech Republic (Central Europe). The sampling was performed by beach seining in an unstructured littoral zone. Perch, Perca fluviatilis L., roach, Rutilus rutilus (L.), bream, Abramis brama (L.), carp, Cyprinus carpio L., ruffe, Gymnocephalus cernua (L.), pikeperch, Sander lucioperca (L.), eel, Anguilla anguilla (L.) and A. brama × R. rutilus hybrids exhibited higher densities at night. Only bleak, Alburnus alburnus (L.) exhibited higher densities during the day. The number of species was higher in night hauls, and mean body size of roach and bleak was also higher at night. Diel changes in fish densities resulted in the change in species composition between day and night. The study has implication for the sampling design to assess littoral fish assemblages using beach seine netting and recommends night sampling for a representative assessment or sampling during both diel periods for a robust assessment. 相似文献
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Stein AJ Nestel P Meenakshi JV Qaim M Sachdev HP Bhutta ZA 《Public health nutrition》2007,10(5):492-501
OBJECTIVE: To estimate the potential impact of zinc biofortification of rice and wheat on public health in India and to evaluate its cost-effectiveness compared with alternative interventions and international standards. DESIGN: The burden of zinc deficiency (ZnD) in India was expressed in disability-adjusted life years (DALYs) lost. Current zinc intakes were derived from a nationally representative household food consumption survey (30-day recall) and attributed to household members based on adult equivalent weights. Using a dose-response function, projected increased zinc intakes from biofortified rice and wheat were translated into potential health improvements for pessimistic and optimistic scenarios. After estimating the costs of developing and disseminating the new varieties, the cost-effectiveness of zinc biofortification was calculated for both scenarios and compared with alternative micronutrient interventions and international reference standards. SETTING: India. SUBJECTS: Representative household survey (n = 119 554). RESULTS: The calculated annual burden of ZnD in India is 2.8 million DALYs lost. Zinc biofortification of rice and wheat may reduce this burden by 20-51% and save 0.6-1.4 million DALYs each year, depending on the scenario. The cost for saving one DALY amounts to $US 0.73-7.31, which is very cost-effective by standards of the World Bank and the World Health Organization, and is lower than that of most other micronutrient interventions. CONCLUSIONS: Not only may zinc biofortification save lives and prevent morbidity among millions of people, it may also help accommodate the need to economise and to allocate resources more efficiently. Further research is needed to corroborate these findings. 相似文献
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CUE-MATE诱导新疆褐牛同期发情试验 总被引：1，自引：1，他引：0
[目的]为了探索新疆褐牛同期发情处理的有效时间段和最佳处理方法.[方法]采用CUE-MATE孕酮栓+PGF2α法进行新疆褐牛同期发情试验,[结果]表明:同期发情主要集中在取栓后的2 d,平均发情率为72.5%,情期受胎率为66.7%;3月的同期发情率显著高于5月和7月(P＜0.05),达到90.8%,但情期受胎率低于5月和7月,为61.0%,差异不显著(P＞0.05);母牛卵巢上以有黄体的同期发情率最高,达到95.3%,其次是有卵泡的,无黄体、卵泡的最低,三者差异显著(P＜0.05);有卵泡的情期受胎率略高于有黄体的,差异不显著(P＞0.05),无黄体、卵泡的同期发情率和受胎率都最低,差异显著(P＜0.05);育成牛的同期发情率略高于经产牛,为92%,差异不显著(P＞0.05);育成牛的情期受胎率显著高于经产牛(P＜0.05),为73.9%.[结论]环境温度、营养水平及母牛卵巢上有无黄体、卵泡影响发情率的高低,CUE-MATE孕酮栓+PGF2α法可用于诱导新疆褐牛的同期发情. 相似文献
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Drainable surplus assessment in irrigated agriculture: field application of the groundwater approach
To assess the drainable surplus of an irrigated area, a methodologybased on a groundwater-balance approach was developed and appliedin Schedule I-B of the Fourth Drainage Project near Faisalabad inPakistan. To determine the seasonal net recharge in this area, anumerical groundwater model was run in inverse mode. The data inputfor the model consisted of the geometry of the aquifer system, theaquifer parameters, and historical watertable elevations. The seasonalnet recharge values, calculated from the individual recharge anddischarge components, were tuned with the results of the inversemodelling. The advantage of such an integrated approach is that allthese components are linked. The design net recharge was estimatedfrom the historical net recharge of the wettest monsoon in the studyperiod. Its rainfall recharge values were then substituted for those of adesign monsoon. In this substitution procedure, the rainfall rechargemethodology and parameters were adopted from the tuning procedure.From this design net recharge, estimates could be made of the requireddrainable surplus, with and without drainage simulation. 相似文献
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Natural resource managers in Pakistan today preside over a massive investment in water distribution infrastructure. An historical bias towards large-scale irrigation systems and a focus on water use for arable crop production appears to have contributed to an imbalance in food production in the region. This has resulted in the diminished supply and elevated price of fish and meat products, compounded by the disruption of natural fisheries. The situation is inconsistent with the regions food security needs and an important potential role exists for increased aquaculture development. Physically and organizationally, the integration of various fish production approaches into existing land and water use practices would also appear to be fundamentally feasible. There would appear to be strong economic justification for diversified water use involving fish production, especially small and medium-scale carp production in ponds, using ground water. More broadly, within the context of the limited potential for further expansion of water resources, integrated aquaculture could contribute a vital productive element to various components of the water distribution arid irrigated farming systems in the Punjab. These include: supply canals, provided diverse institutional and engineering objectives can be accommodated; groundwater (including potential application of saline groundwater); the farm sub-system, especially integrated rice and fish production options in conjunction with alternative pest control strategies such as Integrated Pest Management; and irrigation drainage systems, where water quality permits. Therefore urgent broad research objectives should include the definition, investigation and development of a series of distinct economic and environmentally sustainable approaches to integrated animal protein production from aquatic resources, presently managed principally for agricultural production. Approaches should involve both the replacement of lost fishery potential resulting from large-scale irrigation development and flood control management, and the development of net gains in aquatic output, and should focus particularly on efforts to promote recycling of agricultural residues, reduced pesticide use and efforts to make better use of scarce water resources through the integrated aquaculture production across a broad range of water resources. An increasing number of countries are approaching full development of their surface water resources, and like Pakistan many face the development of new management approaches to increase diversity and improve productivity in relation to water use. The lack of research in support of the development of integrated aquaculture, which lags many years behind comparable agricultural research, may be constraining the breadth of choice available to natural resource managers to meet their food security needs. 相似文献
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根据国家最新公布的<封山(沙)育林技术规程>,即由GB/T 15163-2004替代GB/T 15163-1994后,因封山育林的对象、内容、技术、要求等发生了变化,因此要处理好以下新的问题:①封山育林的内涵及对象.②封山育林对象与适宜条件的关系.③与封育目的目标的关系.④与封山育林技术的关系.⑤与合格标准的关系. 相似文献