小尺度热点地区土地利用/覆被变化研究--以淮南市为例

利用指数模型方法,从区域土地利用/覆被变化(LUCC)的速度、土地流向、空间结构和土地利用程度等方面对淮南市1996～2003年间土地利用变更数据进行了定量描述和分析,揭示了淮南市土地利用及变化的特征,并针对在工矿和居民点整理复垦、土地利用程度等方面存在的问题提出了相应建议,为实现土地资源的合理利用提供科学依据.     

Georelational Analysis of Soil Type, Soil Salt Content, Landform, and Land Use in the Yellow River Delta, China

The Yellow River Delta, one of China’s three major river deltas, is becoming a major region for the development of agriculture and fisheries. Protecting the delicate ecology of newly formed aquatic systems as well as the evolution of soils, natural vegetation, and fauna on older upland environments in the delta is a priority in planning for the wise use of the delta’s resources for future agricultural development. In this article, we use a Geographic Information System (GIS) to analyze relationships between land-use/land-cover characteristics in the Dongying municipality, one of the most intensely developed areas of the delta, and spatial variations in soil salinity and landforms. This analysis reveals that soil salt content decreases from regionally high values in isolated depressions to relatively moderate values in embanked former back swamps, with the lowest values occurring in abandoned river courses. Comparing the present land use on this soil salinity–landform pattern shows that it is basically at odds with general concepts of land suitability for agricultural utilization of saline soils. Crop-based agriculture in the region is probably overdeveloped, whereas more appropriate agricultural development, like cattle and forest production, is underrepresented. Future development should focus on converting farmland in embanked former back swamps and abandoned river courses into grasslands and forests. Crop-based agriculture (up to 151,000 ha) could be planned at the low-salinity terrace uplands and flood plains. The article provides guidelines for decision-makers regarding agricultural land use and wetland protection in the Yellow River Delta.     

INFLUENCE OF REMOTE SENSING IMAGERY SOURCE ON QUANTIFICATION OF RIPARIAN LAND COVER/LAND USE1

ABSTRACT: This paper compares approaches to quantifying land cover/land use (LCLU) in riparian corridors of 23 watersheds in Oregon's Willamette Valley using color infrared aerial photography (AP) and Thematic Mapper (TM) imagery. For each imagery source, LCLU adjacent to stream networks were quantified across a range of lateral and longitudinal scales. Single‐date AP data had higher LCLU class accuracies than the multi‐date TM data, except for row crops. Correlations among LCLU classes for the two imagery sources increased with increased spatial extent. In general, LCLU proportions for AP and TM differed, but lateral/longitudinal patterns were similar. An aggregated vegetation class comprised of forest, shrub/scrub, and grass/forb was strongly associated with a fish index of biotic integrity (IBI) for both AP and TM data, although AP correlations were higher. Highest fish IBI correlations for both data sources were with the aggregated vegetation class close to the stream and for the longest longitudinal scales. The row crop class was strongly associated with stream nitrate for both data sources, although correlations for the TM data were higher. Stream nitrate correlations were strongest for the widest lateral and longest longitudinal scales. Overall, both single‐date AP and multi‐date TM imagery appear to have potential for use in estimating indicators of stream ecological condition.     

FOREST GROWTH IMPACT ON PEAK SNOW PACK MEASUREMENTS AT LONG TERM SNOW COURSES1

ABSTRACT: Snow course surveys in late winter provide stream‐flow forecasters with their best information for making water supply and flood forecasts for the subsequent spring and summer runoff period in mountainous regions of western North America. Snow survey data analyses are generally based on a 30‐year “normal” period. It is well documented that forest cover changes over time will affect snow accumulation on the ground within forests. This paper seeks to determine if forest cover changes over decades at long term snow courses decrease measured peak snow water equivalent (SWE) enough to affect runoff prediction. Annual peak SWE records were analyzed at four snow courses in two different forest types having at least 25 years of snowpack data to detect any decreases in SWE due to forest growth. No statistically significant decreases in annual peak SWE over time were found at any of these four snow courses. The wide range of annual winter precipitation and correspondingly highly variable peak snowpack accumulation, as well as many other weather and site variables, masked any minor trends in the data.     

水压在隧道工程水环境中的力学效应机理初探

隧道工程水环境和隧道工程的设计、施工及维护密切相关 ,往往是诱发工程事故的主要原因 ,其中水压是最重要的基本要素之一 ,对工程的影响主要通过其力学效应表现出来。笔者通过所建立的数学模型 ,初步解释了水压对于隧道工程力学效应 ,评价了其对隧道工程设计、施工和维护的影响     

Computer-aided classification of forest cover types from small scale aerial photography

The US National Park Service must map forest cover types over extensive areas in order to fulfill its goal of maintaining or reconstructing presettlement vegetation within national parks and monuments. Furthermore, such cover type maps must be updated on a regular basis to document vegetation changes. Computer-aided classification of small scale aerial photography is a promising technique for generating forest cover type maps efficiently and inexpensively. In this study, seven cover types were classified with an overall accuracy of 62 percent from a reproduction of a 1120,000 color infrared transparency of a conifer-hardwood forest. The results were encouraging, given the degraded quality of the photograph and the fact that features were not centered, as well as the lack of information on lens vignetting characteristics to make corrections. Suggestions are made for resolving these problems in future research and applications. In addition, it is hypothesized that the overall accuracy is artificially low because the computer-aided classification more accurately portrayed the intermixing of cover types than the hand-drawn maps to which it was compared.     

OPERATIONAL APPLICATIONS OF SATELLITE SNOW COVER OBSERVATIONS1

ABSTRACT: Several federal and state water resources agencies and NASA have recently completed an Applications Systems Verification and Transfer (ASVT) project on the operational applications of satellite snow cover observations. When satellite snow cover data were tested in both empirical seasonal runoff estimation and short term modeling approaches, a definite potential for reducing forecast error was evident. Three years of testing in California resulted in reduction of seasonal stream flow forecast error was evident. Three years of testing in California resulted in reduction of seasonal stream flow forecast error from 15 percent to 10 percent on three study basins; and modeling studies on the Boise River basin in Idaho indicated that satellite snow cover could be used to reduce short term forecast error by up to 9.6 percent (5 day forecast). Potential benefits from improved satellite snow cover based predictions across the 11 western states total 10 million dollars for hydropower and 28 million dollars for irrigation annually. The truly operational application of the new technology in the West, however, will only be possible when the turnaround time for all data is reduced to 72 hours, and the water management agencies can be assured of a continuing supply of operational snow cover data from space.     

A HYDRAULIC TRANSIENT MODEL OF THE UPPER ST. LAWRENCE RIVER FOR WATER RESOURCES STUDIES1

ABSTRACT: A one-dimensional hydraulic transient model has been designed for water resource studies of Lake Ontario and the Upper St. Lawrence River. The model simulates water surface profiles and flows in the St. Lawrence River between Lake Ontario and the Moses-Saunders Power Dam under both open water and ice-covered conditions. Errors in water surface elevations were found to be less than 0.2 feet during quasi-steady conditions on the river. Comparable errors occurred during the ice-covered conditions. A sensitivity analysis found the model to be most sensitive to the roughness coefficients and the flow through the power dam.     

西安地裂缝的数值模拟研究

在分析总结西安地裂缝基本特征的基础上,采用二维有限单元法,对西安地裂缝进行了数值模拟,并从土动力学角度探讨了地裂缝的形成机制．结果表明,西安市区超采地下承压水导致地面不均匀沉降是西安地裂缝产生和发展的主要原因。故认为只有通过对地下承压水的合理开采,控制西安市区地面的不均匀沉降,才是减缓西安地裂缝活动的根本对策。     

平水铜矿的地压危害与安全对策

重点叙述了地压对矿山生产和人身设备的危害;研究了地压控制的系统性安全对策;总结了所取得的经验与效益。