Research Of Ecological Environment Condition Based On The Fractal Theory And Information Entropy In The Wei River Basin

Wei River is the largest tributary of the Yellow River.Its ecological environment's healthstatus is directly related to the sustainable socio-economic development of the Wei RiverBasin. In recent years, the ecological environment of the Wei River was deteriorated seriously,which would restrict and hamper the regional socio-economic's healthy development. So it isnecessary to explore a new method to quantitatively study the change of eco-environmentalconditions in the Wei River basin and take some effective managemental measures for theeco-environment in the Wei River Basin. They can safeguard the Wei River healthy life, andpromote its sustainable socio-economic development.In this thesis, fractal theory was used to deal with the fluctuation characteristic of runoffseries in the main hydrological stations which located in the mainstream and tributaries of theWei River. The multi-fractal fluctuation characteristics of the daily, consecutive daily andmonthly runoff series in the Wei River were mainly calculated and analyzed by MF-DFA. Italso discussed that the relationship of morphologic information of north and south sub-basin,sediment yields in a basin and multi-fractal fluctuations in runoff process. On the basis of theprevious calculations and analysis, this thesis discussed that the relationship betweenmulti-fractal fluctuations characteristic in the typical time's runoff process in the Wei Riverand condition changing,including of woodland area, grassland area and arable land area, andanalyzed the important factors which affect runoff's fluctuation in the Wei River basin. Thefollowing conclusions can be obtained through the research:(1) The daily, consecutive daily and monthly runoff processes of partly hydrologicalstation of the main and tributaries of the Wei River had the multi-fractal characteristic.Therefore, it is not enough that using singular fractal to describe the fractal characteristics ofthe daily, consecutive daily and monthly runoff processes.(2) Through comprehensive analysis, we think that daily, consecutive3daily,consecutive7daily and consecutive15daily runoff were vulnerably affected by impactfactors (precipitation, evaporation, infiltration, forest vegetative ratio, water, etc.).They havepoor ability to reflect the cyclical changes in hydrological phenomena, so its fluctuation is great,the multiple fractal nature is obvious, but changes in annual runoff is relatively stable.(3) Through analyzing the geomorphic information entropy and the area changing ofnorth and south sub-basin of the Wei river, showed that the degree of landform development of the south bankside is more mature than the north bankside, north side of the basinlandscape is mostly stay in the stage of strong life, degree of down-cut erosion is great, it isconsistent to a larger sediment yields of the north side tributaries. But area of the maintributaries of the south side of the watershed is relatively smaller than the north side, lessfactors can affect runoff fluctuation degree, interactions among factors is less, so thefluctuations of the runoff process is violent, this is consistent with the multi-fractal fluctuationanalysis results of the north and south tributary runoff process.(4)The relationship between vegetational coverage and runoff, related with climate,topography, geology, soils, and other environmental conditions in the watershed. Differenttopographic and geologic conditions,lead to effect of vegetation cover on the runoff processare different.Through establish the relationship between multifractal parameters of Weihe River dailyrunoff process and the state of ecological environment, this article try to obtain fractalmeasurement method on evaluation of regional ecological environment,result shows: in WeiRiver watershed, higher forest coverage not means smaller runoff fluctuation, and, hightercropfield area means bigger runoff fluctuation and worse state of ecological environment, buthighter forest-grass vegetation coverage related to the smaller runoff fluctuation.So, forest-grass vegetation coverage could be take as important indicator to judge thestate of the ecological environment in Weihe area.That is, the high the forest-grass vegetationcoverage, the excellent of the eco-environmental, if on the contrary, the ecologicalenvironment is poor. From this, change more cropfield into grassland is the effective way toreduce the erosion degree and sediment yields in north bankside of the basin significantly,andmake the environmental conditions improved, to keep the healthy of the river, and to promotesustainable development of ecological environment and social economy of the Wei River, too.