The Research On Water Resource Sustainable Development In Upper Reaches Of Li River

In the recent decades, the low water flow issue has attracted increasingly public concern, which are causing bottlenecks in the social and economic sustainable developments of the Li River areas. On the basis of the fruits of research on the Li River water resources, this dissertation is focused on the investigation and discussion of the protection, management and utilization of the Li River water resources.In support of this aim various research methods are applied in the paper. The Li River shall be discussed as an integrated part systemically and sustainably with the overall thinking of the different sub-systems within the hydrographic basin. We shall utilize comprehensively the theories and practices of hydrometry, ecology, environmental science and systematic engineering to divide the upper reaches of Li River into five sub-systems such as headwater forests, riverbed, changing volume in wet and/or dry seasons, faculties for retaining water and controlling flood, and the bearing capacity of the water resources so as to construct a systemic analysis framework for the research of this area. A sound cycle system of water resources protection and exploitation in the upper reaches of this river will be established. Through the topographical survey, literature research and analysis of the remote sensing images, we shall emphasize on the five factors of water conservancy, water flow, streams, water retaining and water utilization in the upper reaches of the river, which are interacted and interplayed.The research shows that it is the natural law and man-made factors that attribute to the low water flow of Li River. It belongs to the rainfall type river, and the rainfall is extremely unequally allocated in space and time, about 70 percent of which is in the upper reaches and 62.7 percent of the annual rainfall and the raining season are concentrated within four months (from April to July). The largest volume of rainfall may reach 415.8mm; the least volume falls in the months of December to January of the next year, about 100-110mm, which occupies only about 6 percent of the annual rainfall, which causes directly the seasonal change of the ground water flow of the river and so the flooding season and the dry season are created. In a word, the periodical change of the water volume is a natural law that won't be changed at people's will. In fact, the worsening dry and flooding problems of Li River in the recent decades are mainly caused by the man-made factors. From the 14 to the 19^th centuries, the Flooding City (Guilin City) had been flooded seven to eight times every one hundred years; as the history stepped into the 20th century, the flood increased sharply; till 1995, the Flooding City had been submerged for 23 times during 95years, which reached the peak record in history. Through the technical analysis and calculation of the remote sensing images of the 1980's, 1990's and the year of 2002, in combination with the ground survey, we find that the total area of the headwater forests in the upper reaches of the river has dropped from 24.68% of 1981 to 8.86 of 1998, and sharply to 4.12% in 2002, the reduced forest area is about 1046.77 km2, which is equal to 31 small reservoirs with a storage capacity 1,000,000 m³ of each. The retaining water and controlling flood effect has been greatly diminished by responding to the reduction of headwater forests area, unreasonable distribution of the standing forests, and decaying of the hydrographical function of the forests. Along the total 97 km reaches about 36 km of them are dug to get sand, therefore the riverbed and the banks are ruinously destroyed, which causes the river water to penetrate into the underground water net. According to the 2004 riverbed damagereport, the model calculation shows that the annual leakage volume of the river water reached as high as 0.092 billion m3. In the meantime, the amount of sand the flood carries increased 3 times in the past 10 years due to the excavated banks, serious loss of water and soil erosion, which attributes to the reduction of water volume in the upper reaches of Li River and lengthens the time of low water flow. The expansion of the urbanized area and the great growth of the population have also produced negative effects on the eco-environment of this area. According to the remote sensing images analysis and calculation, the civilized areas in this reaches are expanded so rapidly that the town areas grow from 6.71 km² of the year 1981 to 57.43 km² of 1998 and to the year of 2002 the total growth reaches 140.2 km2. The statistics shows that the four-year (1998—2002) growth is 2.44times while during the 21 years (1981—2002) the growth is as high as 21 times. For the purpose of the sustainable utilization of the water resources in the upper reaches of Li River, a certain number of constructive proposals are made in the research. The headwater forests area should be recovered and enlarged; water resource management must strengthened and the excavation must be forbidden; in order to adjust the water conservancy the reservoirs of Xiao Rongjiang, Chuanjiang and Fuzikou has to be constructed; the science and technology must be promoted to lessen the industrial and agricultural consumption of water resources; the economic leverage is to be used to monitor payable utilization of water resources; an organization must be established to manage, and to monitor the coordination of the water resources distribution and to make suggestions about the excursion patterns in the Li River.The remote sensing technology is applied for the first time to gain access to the information about the headwater forest areas, the residential areas and the variable areas of the surface water in three different periods of 1981, 1998, and 2002, which has provided the basic evidence for the management, restoration and protection of the eco-environment in the upper reaches of Li River. Through the systemic theory analysis innovatively it suggests that the interactions of natural law and human activities have caused the seasonal imbalance of the water volume of Li River. Therefore, the natural law must be respected and a new project for the water retaining and flood controlling will be put forward on the basis of ecological water conservancy and engineering water conservancy. In order to realize the ecological water conservancy, the existing headwater forests, especially the evergreen broad-leaved forests, must be properly maintained; meanwhile, the 2.65×104ha evergreen broad-leaved forests must be increased to enable the water volume of the low water flow months to grow by 4m³.s^-1so that the dry seasons will be reduces from 6 months to 2 months or below in the future. In addition to that, the existing reservoirs plus the programmed reservoirs of Fuzikou, Chuanjiang and Xiao Rongjiang will form a reservoir group to control flood and retain water, consequently the problem of the extremely imbalanced high and low water flow distribution in Li River will be effectively resolved. Through the assessment modeling of the sustainable utilization of the water resources in the upper reaches of Li River, it is calculated that the total water resources in the section is around 4.5 billion m3. The integrated assessment result Value b of the bearing capacity of water resources in 2002 is attached heavily to V₂, and the degree is 0.49568, and the degree to V₃ is 0.2715, while the degree to V₁ is 0.2339 with the integrated assessment result of 0.4826. The analysis shows that there is still large room to the exploit the water resources and their potentialities to serve the social economic development. If the water resources are kept to develop in their current trend, the potentialities of their bearing capacity...