Small Watershed Comprehensive Soil Erosion Control

This paper studies a comprehensive management of soil and water losses in a small watershed, optimum arrangement of its measures and difficult technical questions to counter the natural conditions and soil and water losses in the Loess Plateau. The studies will obtain better benefits in ecological conditions, economy and society to promote a further development of soil and water conservation in China. The author makes a stress on four studies as followings.(1) Studying the law of soil and water losses from a small watershed in the Loess Plateau.(2) Studying the calculation of sediment yield from a small watershed in the Loess Plateau.(3) Studying the methods of planning a comprehensive management for soil and water losses from a small watershed in the Loess Plateau.(4) Studying the measures of a comprehensive management for soil and water losses from a small watershed in the Loess Plateau.The author applies the theories of probability statistics, systematic engineering, ecology, soil and water conservation, morphology, sediment mechanics and so on to the studying, analyzes and discusses the management combining the cases of small watersheds in the Loess Plateau. The results have been obtained as followings.1. Countering to the characters and the state of management for small watersheds in the Loess Plateau, a systematic classification has been first made for the measures of the management and their functions have been analyzed based on the methods used in China and abroad. It is important in theory and practice to carry out a rational comprehensive management for a small watershed and make a scientific evaluation.2. Following the laws of nature and economy, the author raises the principle, target, way and step for the management by using the theories of soil and water conservation and ecology according to the characters of soil and water losses in the Loess Plateau and the theory that human beings and nature should get along harmoniously. To make a plan for a comprehensive management has been first set up according to the land functions in a small watershed. This is a great break in thinking and has an important value of application in planning a comprehensive management of a small watershed.3. The eroding methods and intensities in a small watershed have been classified and zoned according to the laws of soil and water losses and the natural geographical characters in the Loess Plateau. These are helpful to make out a good plan and arrangement for a comprehensive management of a small watershed based on the local conditions.4. The way of calculating sediment yield from a small watershed in the Loess Plateau has been proposed through summarizing and absorbing the studying achievements on soil and water losses in China and abroad. The four indexes of erosive modulus, tolerant erosion, gully density and sediment delivery ratio have been first considered as the majors to measure the degrees of soil and water losses from a small watershed. This study has a greet significant to analyze erosive problems and make out a plan of a comprehensive management for a small watershed.5. The author fully analyses the major eroding factors, ways and mechanics in the Loess Plateau which make an influence on the slopes and in gullies in a small watershed. Based on it, the principle and requirement to arrange the measures of controlling erosion on the slopes and in the gullies have been proposed. With universal soil loss equation and computer technology a policy-making system has been established for the comprehensive management of the slopes in a typical small watershed and a study has been made for an optimum-planning model of the dam system built in gullies. They becomea better conference to make a plan of a comprehensive management of a small watershed in the Loess Plateau.6. The author points out that the erosion occurring along production roads is the major serious man-made erosion and to control road erosion should be one of the main management compositions according to the experience from implementing a comprehensive management in the Loess Plateau for many years. The principal and main activities for controlling road erosion raised out from this study are imbued with an important lighting to build production roads and control their erosion in small watersheds.7. The author make a deep analysis of the reasons deteriorating ecological conditions and soil and water losses based on a great deal of observed and tested results from experiments and a comprehensive management undertaken in the Loess Plateau. To conserve an area for rehabilitation has been first considered as a great strategic activity to control erosion and improve the ecological conditions in the Loss Plateau. A systematic measures and methods have been put forward for conserving areas. They have great function to speed up natural vegetation recovery in small watersheds in the Loess Plateau.