Abstract:Soil erosion not only causes the thining and poorness of soillayer, and frequent drought, but also various kind of disastrous consequences such as overflowing from rivers subsequent to soil erosion, flooding disasters, fertile land to be destroyed and the casualties of man or domestic animals. Soil conservation work must be performed to fundamental problems and the outward ones simultanenously, but harnessing the fundation is the major aspect. The so-called harnessing fundation refers to the way that the ecological no-till should be carried out on either sloping field or rain-fed and water-irrigated field. So, both soil erosion is eliminated and soil loss held back, and we could see the marvelous sense that grasses and trees are growing vigrously, all season looks green and abandant harvest of all food crops could be obtained wherever and whenever, accompanied with the comprehensive development of farming, forestry, husbandry and sideline production. The so-called harnessing outward problems refers to such activities as increasing agricultural capital to make capital construction of farmland greatly, planting trees and building forest in large scale, deeping and clearing all channels in order to make farmland be easy to irrigate or drain, and rivers be unblocked for shipping.

Abstract:The typical soil erosion and degenerating type and its serious consequences in Huangpuchuan basin is expounded all-sidedly in this paper by statistic data. It says that the soil resources will be exhausted after 50 years because of heavy soil and water loss and wind erosion and desertification. So, it is of great urgency to rescue and protect soil resources. Meanwhile, it shows that the reason of soil degenerated by erosion is the unreasonable use of land by comparing present situation of land utilization and its adaptability. At last, it gives the effective measures to utilize, protect, and improve soil under the policy to develop self-sufficient orsemi-self-sufficient agriculture, protective forestry, and commodity stock raising according to ecology idea. It provides regalar scientific basis to work out the plan of land reform.

Abstract:In this paper, the components of particle sizes and the contents of soil nutrients are used to compare correlation between river sediments and soils from the eroded fields, as well as to assess the soil degradation by soil erosion. The results studied are also used to demonstrate the source and stratum of sediment yield in the drainage area. The mechanical composition of the sediments in the Yellow River and its most tributaries is similar to that of loess deposits in the eroded areas with coarse silts (0.05—0.01mm) and fine sands (0.25—0.05mm) in the predomination. Coarse particles larger than 0.25mm couldn't be seen in the sediments of the Sanmen Gorge dam-site and little amounts there are in the loess deposits. The river sediments of the Huangpuchuan Stream and the Kuyehe River contain considerable amount of coarse particles larger than 0.25mm originated from the local denudated sandrock. Coarse particles larger than 0.25mm can be used to distinguish the stratum of sediment yield. The amount of total nitrogen contents of river sediments in most tributaries is 0.04% on the average, which is close to or higher than the lowest value of those in soils. The contents of available phosphorous in sediments are obviously enriched, and most of them is over those in soils, some even as many as 2—3 times. The enrichment ratio of available phosphorous can be used as an important index to illustrate soil degradation caused by soil erosion. The data of river sediments are obtained in 1983 with lopsided dry season.

Abstract:The simulation model on the agriculture system in Tongwei County was checked by the comparing 180 pairs of simulated data in a base-run with statistic data in previous 15 years, the result indicates that the model is an available prediction with an availability of 85%. Four selective developing layouts for agriculture in the county, the crop-leading, the forest-leading, the breeding-leading and the comprehensive developing type wore simulated in IBM PC/XT computer for the period of 1985—2030 year. A dynamic change tendencys of several major objective, the areas of land use and the productive values for crop planting, forest and livestock breeding, and the total yields of crop were separately discussed at three developing steps in the year of 1990, 2000 and 2030. An optimum selection of the four layouts was determined utilizing a multi-purpose comprehensive Fuzzy-adjudgment technique. The comprehensive layout is the best one in a general benefit and effect for economic, ecology, social and exercisable respects. Therefore, the layout can be used as an agriculture developing model in the county. By the end of this century and the year of 2030, the predicted values of total product of the layout would increase by 1.56 times. A dynamic simulatijon optimization technique is a useful tool to make a comprehensive agriculture developing plan for a region.

Abstract:Up to now, 1,203 landslides have been researched in Yangtze River Valley. Most of them distribute along with the up reaches of Yangtzi River on the western part of this valley in large scale and great number. The others are in the middle part of the valley, the major scales are small to middle, but on the slopes of the two banks of Yangtzi River in the section between Fuling and Nanjunguan, the large and the largest landslides with a purt of volume over thousands cubic meter are distributed. The eastern part is with fewer landslides, its major scales is in 10 to 100 thousands cubic meters. All of those mentioned above is from neotectonic action, stability of rock, shape of slope, rainfall intensity, the side erosion of river and the human activities. As the economy and engineering activity is increasing, the landslide event is tending to develop sharply.

Abstract:Yunnan is one of the provinces with the most serious landfall-landside disasters in China. There are 5,000 landslides in this area, 200 ones of them are disastrous. In general, they are in middle or small scales and few landslide bodies are over 1 million m³. Most of the landslides are revival ancient landslides, but few are new-bron and in an active term. They are tending to increase year by year. The preventive measures are: to research the evolution laws of landslide, to stress forecast and prediction, to organize evacuation and dispersion, to build forest and dredge the waterways, to control the typical landfall-landslides in a comprehensive way, and to get effects and extend the experiences.

Abstract:From Shandouping to Chongqing, 214 landslides and collapses are distributed on the banks (the length is 600km) of the Yangtzi River Valley where Three Gorges Dam would be built. The area is more than 100km² and the total volume is 13.52 million m³. There can be 0.36 land slide and collapse in 1.0km of the valley and the volume is 2.2532 million m³. Among 214 landslides and collapses, large or the largest ones (over 10 million m³) are 36. All of them are distributed at the banks of structure, the dipping ends of anticline and the raise ends of syncline, the composite sectors for crossing a few structure line groups, the strong uplifted area for neotectonics and the borders of the structure basin. The destructive ways of the valley and bankslope: the bedding landslide are main; the dissecting landslides are less; and then there loose accumulational landslides of the Quaternary Period occupy 20% of the total volum, the collapses are only about 8%. These landslides and collapses, especially large or the largest landslides are distributed in vital part of reservoir area and will endanger the security of Three Gorges Dam or even the whole of the reservoir.

Abstract:The Three Gorges Project should not be started in the near future, at least during the Seventh Five Plan. The reasons are from: 1, its investment is as high as sixty billion yuan; 2, the flood prevention on the middle and lower reaches can not be solved, and the flood harm on the upper reaches may be strengthened; 3, the problem in choking with silt is solved with difficulty; 4, more disadvantages than advantages in shipping; 5, the less economic benefits for its enormal investment, longer building time and low rate of beneficial result; 6, the problem of emigration from reserior area is conducted with difficulty; 7, it may bring a disastrous consequences. At last, six abstracts of reports of on-the-spot investigation are enclosed.