The Research On Water Exploitation And Change Of Eco-system In Hexi Corridor Since Qing Dynasty

The Hexi Corridor has a special geographical location, with Qilian Mountains to the south, Deserts of Tenggri, Badanjilin and Kumtak to the other three sides. As a result, it is especially dry with only an annual 200mm precipitation while the annual evaporation is 2600mm. Thus, the three inland rivers (Rivers of Shiyang, Hei or Black and shule) are very crucial to the existence of oasis. With water, this area is oasis and without water it would become deserted Gobi. Since Qing Period, this area has transformed from oasis to desert or reversely due to the tremendous water conservatory works. The present thesis makes a research on the rules and interrelationship between water conservatory work and deserticafation and draws the conclusions as below:A. Through the study of the sources, tributaries, amount of flow, flow courses and drainage area and the changes of the three main inland rivers, such conclusions about the rivers in Hexi Corridor can be drawn: 1..The tributaries shrink and the unified water system splits. 2.The natural rivers have gradually become artificial rivers.3. Lakes with terminal of Rivers gradually shrink and even dry.4. Artificial dams take the place of natural rivers and lakes.B. through the study of regulations and managerial rules of the water works in Qing Period, We can sum up principle of fairness and the principle of efficiency, Through the study of the techniques of water exploitation works,we know that the construction of water works in Qing Period is easy and practiced and done according to the local geographical and natural conditions. There were a varity of ways to do the exploitation works and it was beneficial to the people. However, the efficiency is not satisfying and soil erosion is very prevalent.C. Through the study of the interrelation between forests and rivers, such rules can be found: the amount of river flow is in proportion to the amount of forest. Namely, if the forests are luxurious, the rivers are affluent and the annual flow amount is big,D. Through the study of cases about water, analyzing natural causes and social causes of cases about water, We can take in historical experience and lessonsE. Through the study of action that garrisoned troops or peasants opened up wasteland and water systems ,which met a military demand as well as improve mass welfare . water exploitation works resulted in oasis being larger than desertsF. Through the study of unreasonable water exploitation works ,we know causing desertification, the main cause and rules of changes of desert is present. There were three types of landscape for desertification; wind-erosion type, wind-accumulation type and salinity-causing type. there was a balance between oasis and deserts , The law of desertification Change is that desertification mainly occurred in the downstream of inland rivers. The more the river flowed, the more the area of desertification became. The saline area was distributed mainly in the alluvial fan margin depression, around lake, river downstream. Once desertification occurs, it was difficult to reverse the situation.