An Analysis on the Stream Construction of the Xinfengjiang River Basin

The Xinfengjiang River basin is one of the most important drinking water source in Guangdong Province.In this paper,characteristics of the change of basic stream construction,stream bifurcation,and stream fractal dimension are analyzed by using the data of 1968 and 2005.Combined with land use data,meteorological data,and hydrological data of the basin,the impacts of natural and human factors on spatial evolution of stream construction are discussed.The results show that:(1) during 1968-2005,the river network structure appeared as a trend from comprehension to simplicity.The values of stream number,density,rank,bifurcation,and fractal dimension all decreased to a certain extent.The first rank streams had greater decrease,that made the grade of the river network in the basin reduce from 7 in 1968 to 6 in 2005.The total length of the river network was shortened by 620.35 km,and the number of rivers had a reduction of 818.(2) The ratios of bifurcation in the first and fourth grades of river network reduced,while those in the second and third grades of river network increased.That means the nature bifurcation characteristics of river network were deteriorated.(3) The fractal dimension value decreased from 1.945 to 1.698 during 1968-2005.The value in 2005 was still at normal level,as compared with the fractal dimension values in other regions.(4) There was significant semi-logarithm linear correlation between grade of river network,number of rivers,and mean length of rivers.The correlation coefficient is between 0.977 and 0.998.The results accorded with Horton law and river network length law.(5) The changes of river network in the Xinfengjiang River basin were influenced by the natural factors and human factors.Human factors,such as land use change and damage of vegetation,did more harm to river network than natural factors did in a short period.It is necessary to adopt some methods to protect this important water source area from adverse influence of intensive human activity.