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991.
黄河三角洲农牧业生产潜力 总被引:6,自引:0,他引:6
本文从对黄河三角洲的宜农地和宜牧地的分析入手,对该区农作物生产潜力、牧草及载畜量潜力进行了探讨。并针对目前农牧业生产水平和存在的问题,提出了相应的对策。 相似文献
992.
LIU Can-de HE Bao-yin LI Mao-tian REN Xian-you 《中国地理科学(英文版)》2006,16(1):79-82
1INTRODUCTIONThe quality of water is traditionally determined by col-lectingwatersamplesandanalyzingthesamplesin a lab-oratory. However, sampling is very much hard sledding,time-consuming, slow and expensive, and easily in thecontrol of weather conditions, and does not include allwater areas. Satellite estimates of water quality havefound widespread application. Remote sensing instru-ments have been applied in water quality monitoringwith varying success (DANA and RICHARD, 1999;RUDD… 相似文献
993.
Houjie Wang Zuosheng Yang Yoshiki Saito J. Paul Liu Xiaoxia Sun 《Global and Planetary Change》2006,50(3-4):212-225
The Huanghe, the second largest river in China, is now under great pressure as a water resource. Using datasets of river water discharge, water consumption and regional precipitation for the past 50 years, we elucidate some connections between decreasing water discharges, global El Niño/Southern Oscillation (ENSO) events and anthropogenic impacts in the drainage basin. Global ENSO events, which directly affected the regional precipitation in the river basin, resulted in approximately 51% decrease in river water discharge to the sea. The degree of anthropogenic impacts on river water discharge is now as great as that of natural influences, accelerating the water losses in the hydrological cycle. The large dams and reservoirs regulated the water discharge and reduced the peak flows by storing the water in the flood season and releasing it in the dry season as needed for agricultural irrigation. Thus, as a result, large dams and reservoirs have shifted the seasonal distribution patterns of water discharge and water consumption and finally resulted in rapidly increasing water consumption. Meanwhile, the annual distribution pattern of water consumption also changed under the regulation of dams and reservoirs, indicating that the people living in the river basin consume the water more and more to suit actual agricultural schedule rather than depending upon natural pattern of annual precipitation. The combination of the increasing water consumption facilitated by the dams and reservoirs and the decreasing precipitation closely associated with the global ENSO events over the past half century has resulted in water scarcity in this world-famous river, as well as in a number of subsequent serious results for the river, delta and coastal ocean. 相似文献
994.
Stream temperature is a complex function of energy inputs including solar radiation and latent and sensible heat transfer. In streams where groundwater inputs are significant, energy input through advection can also be an important control on stream temperature. For an individual stream reach, models of stream temperature can take advantage of direct measurement or estimation of these energy inputs for a given river channel environment. Understanding spatial patterns of stream temperature at a landscape scale requires predicting how this environment varies through space, and under different atmospheric conditions. At the landscape scale, air temperature is often used as a surrogate for the dominant controls on stream temperature. In this study we show that, in regions where groundwater inputs are key controls and the degree of groundwater input varies in space, air temperature alone is unlikely to explain within-landscape stream temperature patterns. We illustrate how a geologic template can offer insight into landscape-scale patterns of stream temperature and its predictability from air temperature relationships. We focus on variation in stream temperature within headwater streams within the McKenzie River basin in western Oregon. In this region, as in other areas of the Pacific Northwest, fish sensitivity to summer stream temperatures continues to be a pressing environmental issue. We show that, within the McKenzie, streams which are sourced from deeper groundwater reservoirs versus shallow subsurface flow systems have distinct summer temperature regimes. Groundwater streams are colder, less variable and less sensitive to air temperature variation. We use these results from the western Oregon Cascade hydroclimatic regime to illustrate a conceptual framework for developing regional-scale indicators of stream temperature variation that considers the underlying geologic controls on spatial variation, and the relative roles played by energy and water inputs. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
995.
Bruce E. Frey J.Rubén Lara-Lara Lawrence F. Small 《Estuarine, Coastal and Shelf Science》1983,17(2):213-218
The eruption of Mt Saint Helens on 18 May 1980 resulted in a massive increase in suspended particulate material in the Columbia River Estuary, producing a substantial increase in light attenuation. Since photosynthesis in the estuarine water column is partly controlled by the depth of light penetration in the water, photosynthesis was reduced by about 75% during the period of increased turbidity. It took about five weeks for the estuary to clear. Although primary production within the estuarine water column was greatly diminished during this period, the flux of particulate carbon through the estuary was high, and the total production we estimate to have been lost amounted to only about 2% of the total particulate carbon flux just after the eruption. That the high levels of turbidity in the estuary did not induce a severe fall in the phytoplankton population is evidence that phytoplankton biomass concentrations in the Columbia River Estuary are mostly a function of import from the Columbia River, rather than a function of in situ production. 相似文献
996.
The spatial division of industries of the pearl river delta in the 1990s: Characteristics and trends
The article analyzed the spatial division of industries of the Pearl River Delta (PRD) in the 1990s, a period that witnessed
the deepening of the reform and opening policies and continued rapid development of the region. By adopting the index of specialization,
the extent of specialization, its change and its spatial distribution in the region are measured and demonstrated. The research
revealed that, despite the trend of more balanced development of the secondary sector between the PRD and the rest of the
province, in the PRD, it is the unbalanced development that dominated and the spatial division of the secondary sector has
been shaped. The tertiary industry has also been experiencing unbalance development and the spatial division of the tertiary
sector has been emerging, its extent of concentration appearing even more evident than that of the secondary sector. The author
also discussed the linkage between the spatial division of the two sectors. In the end of the paper, the trends of the spatial
division of the industries in the PRD are forecasted.
Foundation item: Under the auspices of the National Natural Science Foundation of China (No. 49831030).
Biography: XU Yong-jian (1972 – ), female, a native of Changsha City, Ph. D.. Her research interest includes urban geography. 相似文献
997.
PROBLEMSOFTHEAQUATICENVIRONMENTANDCOUNTERMEASURESINRAPIDECONOMICDEVELOPMENTINTHEZHUJIANGRIVERDELTA¥WenYanmao(温琰茂);ChengGuopei... 相似文献
998.
999.
The 4.45 m-thick pure ice lens have been discovered firstly at depth from 19.81 -24.26 m in the bore No.6, which locates in north bank of the Ngoring Lake. In source region of the Huanghe (Yellow) River, 14C dating, X -ray diffraction, pollen analysis, micropalaeontology, chemical components, environmental isotope 2H, 3H, 18O and freezing point of the ice and water samples from the bore have been tested and microorganism in the ice have been also appraised with microscope. Combined with the research on geomorphy and Quaternary around the lake, the ice lens are determined as a kind of deep-buried lake ice, formed in 35,030-45,209 yr.B.P., and annual mean air temperature was about -10℃ during that time. 相似文献
1000.
Primary fish survey in the Huanghe River estuary 总被引:2,自引:0,他引:2
The survey in the Huanghe River estuary indicated that the 85 fish species found there comprised three faunal elements: warm-water
species (29.4%), warm-temperate species (55.3%) and cold-temperate species (15.3%). The seasonal changes of fish species,
density and biomass are obvious. The total biomass is highest (7 699t) in August and lowest (489 t) in January.Setipinna taty has mean density of 9 278 indiv/km2, and is the most important species constituting 25.5% of the total weight of fish caught.Trichiurus haumela was a dominant species in the 1950s, but no one was caught in this survey. There were obvious changes of the dominant fish
species during the recent three decades. The demersal fish biomass has dropped greatly to only 1/10 in over 50 years since
1930.
Contribution No. 2210 from the Institute of Oceanology, Academia Sinica. 相似文献