The Research On Driving Factor Of Scale Effect In The Water And Sediment Change Of Kuye River

The changes of underlying surface affect the hydrology, water and sediment of drainage basin; different spatial and temporal scales and features changes of underlying surface will also produce varying degrees of effects on sediment discharge and runoff of Kuye River. As climate factors and human activities are two important factors affecting the water and sediment changes of Kuye river, in this thesis, the author analyzes and compares the known survey data and research materials and chooses three different scales from Kuye River from 1980 to 2013 as research object to study the effects of underlying surface changes under different scales on the water and sediment evolution. The author used Grey Relational Analysis to calculate the relevance between the driving factors and made the following research achievements:1. Collecting and systematically analyzing the precipitation materials of current precipitation stations from 1980 to 2013.2. Collecting and analyzing precipitation, runoff and sediment discharge materials of Xinmiao hydrometric station, Wangdaoheng Tower hydrometric station, Wenjiachuan hydrometric station. Adopting double mass curve method to map out the double mass curves of runoff-precipitation and sediment discharge-precipitation at different periods of Kuye River from 1980 to 2013.3. Adopting double mass curve method to analyze that changes of runoff and sediment discharge of the three stations and the two obvious turning points occurred in 1988 and 1997, primarily dividing out three typical periods of water and sediment changes of 1980-1988,1989-1997,1998-2013 and mapping out double mass curves of each typical period.4. Using Mann-Kendall test method to verify the typical periods to be 1980-1988, 1989-1997,1998-2013.5. By calculating water and sediment reducing effects, it can be known that the water and sediment reducing effects of three periods increase along with the evaluation period, which indicates that the soil and water conservation measures, including forestry and agricultural practices and water conservation engineering measures, play sustainable role for soil and water conservation. Along with the increasing degree of governance, the soil and water conservation effects grow more obvious. Observing from the whole evaluation period of Xinmiao station, the water reducing effect is 64%, and sediment reducing effect is 38%, with the former greater than the latter; Observing from the whole evaluation period of Wangdaoheng Tower station, the water reducing effect is 6.6%, and sediment reducing effect is 30%; observing from the whole evaluation period of Wenjiachuan station, the water reducing effect is 14.2%, and sediment reducing effect is 58%, with the latter greater than the former;6. Using Grey Relational Analysis method to calculate the relevance of the driving factors of the changes. Calculating the two driving factors of the runoff, which is precipitation and vegetation coverage by Grey Relational Analysis method, the relevance of the vegetation coverage is obvious higher than that of precipitation and the relevance is not much affected by the scales. The three typical periods all follow the corresponding rule. As for the two driving factors of sediment discharge, precipitation and vegetation coverage, the relevance of the vegetation coverage is obvious higher than that of precipitation and the relevance is not much affected by the scales. The three typical periods all follow the corresponding rule.