Abstract:According to erosivity and landform, soil erosions are divided into sheet erosion, gully erosion and gravity gully erosion. 1. Sheet erosion is the erosion caused by rain drop and overland flow. Because of the influence of landform and vegetation, sheet erosion mainly is the rill erosion. We use the equation of water balance and the relationship between vegetation and sediment yield are used to research the water balance on runoff plot, the influence of vegetation on sheet erosion, and sediment and runoff yield on plot; 2. Gully erosion is caused by concentrated flow coming from slope land and cliff; 3. Gravity gully is caused by mixed effect of gravity and runoff. In this paper we divided the gravity gully into three parts: Sheet flow effect part, gravity-runoff effect part, and transport-deposit part.

Abstract:By taking the formation of mud-rain and dust-rain and other mud "granular fine sand", and the inlaying of fine mineral grain into coarse sand and other phynomena, as the sole characteristic for the formation of loess plateau caused only by the blowing and carrying of wind, and after checking each different periods'loess,which were formated for 2.5 million years long, it was believed that the formation of the loess plateau was indeed the causes that the loess dust, which was carried by wind from west, met the moist airflow from east then continuously fell down then accumulated gradually. The loess layer accumulated this way, in which the structure appears frame touch, possessed fine aeration and permeability originally, later it is affected by the reproduction of vegetation, especially by the effect of root system of grass, the cha racter is strengthened. This is the sole background and source for the accumulation of loess up to 100 meters and formulating the complete loess plateau--ancient soil under the natural condition. The soil and water loss violently, the main reason was human's destroy on natural vegetation, thus it thoroughly destroyed the permeability and anti-scouring of soil. So recent harnessing measures on loess plateau are forced to be "no-site-retain all precipitation" as the strategic goat and adopt measures as "cereal crops are planted on plain and plateau land, forest and fruit tree are set on gullies, grass and shrub are located on hillside";and combining with the social and economic requirement, to arrange the reasonable land utilization and concrete productive measures.

Abstract:The surface erosion and fluvial silt in upper reaches of Changjiang River were analyzed systematically. It was considered that the development of surface erosion in upper Changjiang was affected by unreasonable social economic activities such as the agricultural cultivation, forest and prairie exploitation,roads building,and capital construction and so on which enlarges the area of soil and water loss in upper Changjiang River. The author also analyzed and forecasted that the erosion amount would reduce to 1.022 billion tons from present 1.568 billion tons in the end of this century based on recent steps. By regional forecasting the effect of surface erosion on fluvial silt, it was believed that the surface erosion could be reduced largely by harness the upper Changjiang River,but the fluvial silt may be not changed a lot. The silt amount of water carry will range from 0.488 to 0.502 billion tons at Yichang hydrometric station in 2000.

Abstract:Through the investigation to the 12 counties in northwest sichuan it is said that the increasing pollution from industry causes the further worsening of the ecological environment in the upper reaches of Yangtse river due to the serious destruction to the forest.For this it is suggested that, 1. to put the recovering of ecological balance in the upper reaches of Yangtse river at the position of the general strategy of the nation, paying attention to it;2. to raise th forest cover as the basis to recover the ecological balance;3. to accelarate the development of the water conservancy resource to protect forest with electricity and to conserve water with forest should thought as the essential matter to recover the ecological balance;4. to enhance the comprehensive harness and utilization, meanwhile to change the harm into benefit.

Abstract:Hill area in sichuan is the main production place of food,cook oil,cotton,flax,fruit,pig,etc.The main problem is soil and water loss in this area. Hill area with heavy storm make up more than 80% of the total area.The most important facts which affect erosion are loose soil with high erodibility and high population density of 606 person per square kilometer).According to the typical investigation, the dry slope farm land is about 45.58% of the cultivation land. The slope land is the chief source of the sediment.So the drain and store up method by means of terraced field, count plough, flood storing flood is the effective measures for hill region harness. In this paper we would make some suggestion for soil and water conservation of slope farm land, such as countcy side law, investment, compreshensive measures, etc.

Abstract:The population growth reaches one hundred million in the world and twenty million in China every year. The prospect of mankind is clousely togetber with food production and so is the arable land change.How to tackle the relationship of population-food-arable land should be an imporrant problem in face of the world. This paper applying the central link formulae and gray system in population-food-arable land relationship does an analysis of population growth and food production of Guyuan County for 9 years in the past and 12 years in the future refering to some countries in the world, and it was done under different rates controlling population growth.The conclusion is that if it is going on as the current rates of population growth and food production to the end of the contury, the food shortage for Guyuan County will be very serious, and it is only controlling population growth strictly, and increassing agricultural input energetically the state in the future may be better.

Abstract:On the basis of the Investigation (?) the soil types it is found that the soil moisture resources have the characteristics as follows.1. the water holding capability of soil is high and the field capacity of the main soils ranges from 19 to 22 percent, being as the middle and higher level;2. soil water storage keeps lower regime, generally about 60%～88% and 43%～56% of the field capacity;3. the use ration of the soil moisture is lower, the surplus available water in the depth of 0～5 m varies from 413.40 to 463.16 mm;4. a dry horizon of the biological utilization commenly exists in the loessial soils, i. e., temporary or permanent dry layer.According to the analysis of soil moisture regime, some measures improving soil water conditions have been suggested in this paper.

Abstract:Based on the understanding of the intension of soil and water conservation,and the present situation of scientific research institutes of soil and wa ter conservation in Fujian Province,the author took further steps to discuss how to improve the scientific research work of soil and water conservation in Fujian Province.