Abstract:In the process of preventing flood there are three serious mistakes, .e.，"neglecting South but saving North","storing flood and reclaiming"， and"abandonning the upper but protecting the lower",of which constructing Three-Gorge Dam having been brewed would make greater mistake than the former two because of the uncorrect guidline of"abandonning the upper' but protecting the lower".The measures to harness Yangtze River should be practiced in order and in comprehensive planinng, including to。? :elerating the flood-prevention engineers on plain seriously, to eliminatr the retards in channel, to establish law strictly and to implement it，to dispel hidden danger in order to prevent the bursting of JinJiang embankment reso- lutly, to give up land planted for lake in order to recover "village rich in fish and rice"，to harness Duntinhu Lake actively,to build reserviors on branch rivers in combination with multiple use,to strengthen soil conservation in practice and to raise the level of science and management.

Abstract:It is accounted that in 1982 the soil erosion area in Yangtze Riverwatershed has been raisen to 739,400km~2,being amounted to 41% of the totalarea and 1 times more than that in 1957.Although the annual sedimentload observed at Yichang station is 600 million tons,the total soil loss ofthe whole watershed can reach 2 billion ton,much more serious thanthat in the watershed of Yellow River. Soil conservation and protecting-forest system is connected with the social-economic development, thethrowing of poorness and obtaining of riching as well as the long-termbenefit in improvement of ecological environment of the region, it is alsorelated to the control and safty for long time of the wide area at middle-lower reaches.

Abstract:This paper studies the relationship of landslides and collapses to rockproperties and structural characteristics of slope (structural types of rockbody, structural shapes of slope profile, shapes of slope, and angles ofslope), and sums up the laws of development of landslides and collapsesin the reservior area of the Three Gorges project of the Yangtze Riverfrom semi-quantitative point. The laws supply an important basis forslope stability evaluation and the prediction of distructures of the otherandslides and collapses.

Abstract:Comparing the deposit of Yellow river with Yangtze, we may see thatin the cathment area of Yellow river which is well known by its high de-posit, there is much loess to bear eroding for hundreds of years, and while in Yangtze valley,many places the soil layer is too thin to bear anyeroding. After a hard rain,most slope area become rocky land which can-not be used any more. The facts of soil crises, land crises and channelcrises are the convinced examples. To harness Yangtze valley, the overalland mass point of view must be taken, and main energy cannot only beput on the large projects in major channel such as Three Gorges Dam,butalso on the controlling the increasing loss soil and water which has brou-ght disaster and crises to mass and national economic construction. Weappear that the government should pay more attention to and strenghtenon the work of soil and water conservation in Yangtze valley.

Abstract:Planting trees and grasses is one of main measures for soil and waterconservation. There is not its own character in the work and expectingbenefits yet in the south of Shaanxi, for people pay little attention tothe method of planting and selecting tree and grass seeds. Now it is thetime for us to spread the advanced method of soil preparation for affores-tation planting trees in strip (or strip planting), and extend plantingtrees and grasses that is suitable for growing in the area, have bettersoil and water conservation benefits and economic value.

Abstract:At present the chech dam for building farmland constructed in loessarea,generally,is designed and checked according to the oppotunity of onetime in 10 year and one time in 30 years respectively,which has been dem-onstrated in practice to be lower and thought as the major reason to causedam bursting.Having been studied,the optimum designed standard of floodis one time in 20 years and one time in 50 to 100 years for designed floodand flood check respectively.On total consumption of money and material,it will save 15-20% of that,compared with the two adjucent standard ofdesigned flood.It is suggested that the major engines of the check dam bedesigned on the standard of one time in 25 years,and checked on one timein 100 to 300 years,if done as this,it would be economical.

Abstract:The western area of 1oss plateau of China,including the area of GansuProvince,Ninxia Hui Autonomous region and Haidon district of QinghaiProvince, lies in the arid and semi-arid climatic zone. The soil moisturegenerally is the state with low storage and low usability,all kinds of landremainds moisture potentiality in soil usable to the crops on the ground indifferent extent.The way to raise the use ratio of soil moisture is to adjustthe variety structure in the area of farming,forest and grass,to raise theground temperature in effective method,to raise the level of fertilizer ap-plication,using fertilizer to transform water,to develop larger mixed forestwith arbor tree and brush and to change the tillage style.

Abstract:The development of animal husbandry in the loess plateau ravine de-mands to supply high output and high quality pasture and build pasture ba-se. For this, two fine varieties,Sainfoin (O.vicialflia Seop) and Milkretch(A.adsurgens Poll),has been introduced in Changwu county,Shaaxi Prov.The experiment shows that the surviving rate over winter of both kindsof pastures are 100% and the growth is well developed. The Sainfoin maystand strong dry condition, and it contains more rich nutrient and coarseprotein in every period compared with Milkretch, and it is also palatablefor animals, it is a good protein forage. But the yield of Milkretch ishig-her than that of Sainfoin. The experiment shows that both of the pas-ture are of great value to spread, especially the Sainfoin.