Analysis On Evolvement Characteristics Of Drought Under Changing Environment In Aksu River Basin

Drought is one of the most common meteorological disasters, which is a threat of human living environment. And the dual influences of climate change and human activities, intensify the extent of drought damage. Aksu River basin is located in the northwest arid areas, and it is one of the main areas of food crop production in southern Xinjiang. But the frequent drought disaster has always been the main meteorological disasters to the region in the production of farming and animal husbandry. And Aksu River basin is located in arid areas, many widely used drought evaluation indexes are not good because of the special climate characteristics. Therefore, based on the analysis of Aksu River basin water cycle evolution and water balance characteristics, this paper built the water resources evaluation system in the drought situation, which is used to evaluate the evolvement rule of Aksu River basin drought, and provide reliable basis to the rational allocation of water resources, ease the contradiction of supply and demand of water.According to the meteorological and hydrological dates of Aksu River basin from 1961 to 2011 to analyze the evolution laws of water cycle elements. According to the different underlying surface conditions and water conservancy project of water supply network dividing the study area, and form the drought evaluation units. On the basis of different evaluation units, analyzing the characteristics of the area water balance, and adapted to the different partitions of drought evaluation index, build a new drought evaluation law under drought situation. At the end, this paper also analysis Aksu river basin comprehensive drought evolution characteristics. And the main conclusions are as follows:(1) The analysis of Aksu River basin water cycle evolution.Nearly 51 years, the temperature, precipitation of Aksu River basin, both have varying degrees of increase. But the evaporation has a downward trend. In recent 10 years the groundwater buried depth of plain area increases year by year. Runoff increased slightly but it has a uneven water supply, more than half of annual water flow are concentrated in the summer. All the Mutation points are concentrated in the 1980 s to 1990 s, rainfall and temperature mutations happen the earliest time, it also suggests that the rainfall and temperature are the most direct response factor to climate change.(2) The division of evaluation units and analysis of water balance.According to the underlying surface conditions of Aksu River basin and the distribution of the meteorological factors, divide the evaluation units of the studied area. And eventually formed four mountains, two desert and five oasis areas. Analysis of the characteristics of water balance of the three parts, it can be seen from the results that the mountain water flux increased, but not the out of the mountain pass runoff, and the excess water or stored in the form of ice snow in the mountains or seep into the underground supplement groundwater. Desert water balance mainly include precipitation, evaporation and groundwater level change. And the groundwater buried depth increases year by year, and there are parts of underground water level has dropped under the suitable water level for plant growth. Analysis the change of obtained water, drainage water and water consumption of oasis area. With the expansion of the cultivated land area and the continuous improvement of the water supply facilities, oasis area is characterized by obvious "nature- society" water cycle characteristics.(3) The built of drought indexes of Aksu River and the analysis of drought evolution law.Based on the partition of different water balance characteristics built of drought indexes of Aksu River. Mountains mainly include the meteorological drought, so choose the compound drought index as the mountains drought evaluation index. The vegetation growth of desert area is mainly related to the distribution and groundwater depth, so build ecological drought desert drought evaluation index EI with the core of groundwater buried depth. Oasis area drought is a result of the combined action of hydrological factors and artificial water supply network, so build water drought index DI with the core of the comprehensive water lacking rate. Analysis results showed that the drought in mountain areas has relieved, but in oasis and desert areas are both increased. With the expansion of the cultivated land of Aksu River basin, and the time nonidentity of glacial snowmelt runoff and peak water demand make the Aksu River basin water supply and demand contradiction is widening. Though there is a certain ease of mountains meteorological drought, it is not effective enough for comprehensive drought. So you must reasonable allocation of water resources according to the coming water and water features, analysis of water allocation plan under different water situation, combined with administrative districts and three red line, the water quantity allocation to different water distribution unit to relieve the increasing the drought of Aksu River basin.