Soil Characteristics And Infiltration Simulation Of The Babao River Basin In The Upper Reaches Of The Heihe River

The Heihe River basin involved in the Qinghai,Gansu,Inner Mongolia province.It lies in the northwest inland,where water resources are particularly important.But because of lacking scientific utilization of water resource for many years in Heihe River and the climate change,Heihe River ecological environment is deteriorating trend.The upstream area of the Heihe River which lies in the Qilian Mountain area is not only the important water supply area of the Zhangye in the middle of the Heihe River,which lies in the hexi corridor in Gansu province,but also the water source of Ejina oasis in Inner Mongolia province which lies in the downstream of the Heihe River.How to make good use of heihe river basin of water is related to the economic sustainable development of the Zhangye in the middle of the Heihe River.At the same time,it is related to the evolution of the two big desert which lies in the both sides of the Heihe River.It is particularly important to research on the water source of the Heihe River basin for the sustainable development of ecology,economy and society environment in the basin.Soil water infiltration is not only a key link in the process of rainfall-runoff cycle,but also an important link of the process of transformation of the four kinds of atmospheric water,surface water,soil water and groundwater.To study the soil water infiltration of the Heihe River basin upstream is beneficial to promote the water conservation ability of Babao river basin.It will not only help promote the development of the basic theory research with the unsaturated soil water infiltration and migration,but also provide scientific basis for the comprehensive evaluation of the surface and groundwater resources,reducing natural disasters,strengthening to for ecological construction in heihe river basin.The Babao River basin in the upstream of Heihe Rive which is the important water supply area of Continental River in northwest area is used as the research object.Through collecting and dealing with the data of climate,vegetation,soil infiltration,and so on,the soil characteristics and soil infiltration process were systematically analyzed and researched.Based on the first-hand data of infiltration of in situ test,the infiltration process were fitted to use the different model,at the same time,the relationship between the infiltration rate and soil property index were analyzed.Based on the index of SSE,RMSE,R,ME,EF and W to quantitatively evaluate the stand or fall of model fitting,the optimal mode is found.At the same time,through the establishment of soil conversion function,realizes the point to surface conversion,the spatial distribution characteristics of the infiltration rate in the study area were analyzed.The main conclusions are as follows:(1)The high value of biomass distributes in the central basin in the study area,and relatively concentrates at the southern bank of the river.At the same time,the low value of biomass,according to the patch shape,distributes along the river main stream.This suggests that the vegetation grow wall in central basin,in which due to reasons such as terrain appear low vegetation coverage also appears.The study also found that the alpine grassland biomass in the basin is different with the different altitude.Precipitation in the study area did not change obviously.But the temperature is rising since 1997,which has intensified evaporation of soil and vegetation.The maximum biomass is present in schattenseite and slope slower regional,where the vegetation grew well.(2)Soil moisture content from the surface to down in the study area showed a trend of power function decline,and moisture content change between 20.35 and 47.55%.Shrub grassland soil moisture content was higher than that of meadow and grassland vegetation types.The soil water content in schattenseite is larger.The soil surface has a high organic matter value,up to 11.87 g/kg.The soil organic matter content showed the power function decreasing trend from the soil surface to down.The whole soil profile,the organic matter of thickets is higher than that of the meadow and grassland.Within 60 cm depth,the soil organic matter is bigger on the top of slope.The organic matter content of the schattenseite slope is higher.The change rule of soil moisture content and the soil organic matter in the study area show the consistency.Most soil of the study area belongs to the silty soil or silty loam soil.The most content of clay distributed between 5%?12%,the average content of clay is 8.28%,which showed that the content of clay is relatively stable.It also makes the changes of fractal dimension of the soil particle size distribution is small,between 2.556?2.717,with an average of 2.669,a Spannweite value of 0.161,the variation coefficient of 1.37%.Combined with the study results on the relationship between the soil fractal dimension and grassland degradation,the vegetation coverage of the research area is good,no obvious vegetation degeneration.The soil water characteristic curve of the study area showed the power function curve.The high and low difference of the curve is bigger,that shows the difference of water retention capability is large.(3)In Babao river basin,the change of soil initial infiltration rate and the steady infiltration rate between various points is bigger.At the experiment process with the water of 5 cm high,the initial infiltration rate lies in 0.057 cm/min?0.74 cm/min;the steady infiltration rate in 0.033 cm/min?0.356 cm/min.At the experiment process with the water of 10 cm high,the initial infiltration rate change from 0.063 cm/min to 1.150 cm/min;the steady infiltration rate from 0.040 cm/min to 0.671 cm/min.Compared with different depth infiltration rate of change under the same height of water,in addition to a different point of that 40 cm deep infiltration rate is greater than 20 cm depth,most is that 20 cm depth of infiltration rate is more than 40 cm depth.In Babao river basin,the initial infiltration rate changes from 0.287 cm/min to 0.446 cm/min,as the steady infiltration rate changes from 0.15 cm/min to 0.222 cm/min;Both at different depths and in different water head,the whole process of infiltration showed the following characteristics:0?10 min process of soil infiltration rate is obviously reduced;10?30 min soil infiltration rate decreased slowly;After 30 min infiltration rate gradually achieve stability;so the soil infiltration in Babao river basin are divided into:0?10 min stage of rapid change;10?30 min slowly changing stage;After 30 min steady stage three stages.(4)On the 5 cm high water,the initial infiltration rate and the steady infiltration rate of 20 cm depth tends to increase with increasing moisture content.But they show a decrease trend with the increase of moisture content at the 40 cm depth.On the 5 cm high water,relationship of the infiltration rate and moisture content is consistent at 20 cm depth and 40 cm depth,which show the infiltration rate decreases with the increase of moisture content.By analyzed the relationship of infiltration rate and organic matter,the result shows:the infiltration rate decrease with the organic matter increase at the 20 cm depth and 40 cm depth.The infiltration rate is negative correlation with clay and silts whichever depth,at the same time,it show positive correlation with sand.(5)Using Kostiakov model,Horton model and Philip model to fitting the infiltration process,the result shows as:under the condition of water 5 cm high,a value of Kostiakov model fitting parameters change in 0.07?0.07,the difference of every point's initial infiltration rate at 40 cm depth is smaller than the difference at 20 cm depth,as well as steady infiltration rate difference.In other ward,the initial infiltration rate and the steady infiltration rate of 40 cm depth is relatively stable.At the same time,the b value of Kostiakov model fitting parameters change between 0.15?0.34.The infiltration rate change at 40 cm which decrease with time is smaller than that at 20 cm depth.Under the condition of water 10 cm high,a value change in 0.07?0.07,At the same time,b value change in 0.16?0.40.There have a same rule with 20 cm depth:the initial infiltration rate and the steady infiltration rate of 40 cm depth are relatively stable.The difference of every point's initial infiltration rate at 40 cm depth is smaller than the difference at 20 cm depth.Under the condition of water 5 cm high,k value of Horton model fitting parameter changes between 0.032?0.328.At the 20 cm depth,some soil infiltration rate decreased quickly,some decreased slowly,and infiltration rate of 40 cm depth decreased relatively stable.Under the condition of water 10 cm high,k value changes between 0.032?0.328.There have a same rule with 20 cm depth:the decrease of infiltration rate at 40 cm depth is more stable than the that at 20 cm depth.Under the different water head and different soil depth,the changing law of infiltration rate that reflected by the model fitting parameters showed a high degree of consistency.Each characteristic factor has certain relations with soil infiltration model parameters.Horton model parameter k decreases with the increase of clay and silt content,soil organic matter.At the same time,it increased with the increase of sand content.There is no close relationship with soil water content.The s value of Philip model parameters had no obvious correlation with soil characteristic index.The a value of Kostiakov model parameters presented a negative correlation of the power function type with the soil organic matter,clay content.At the same time,b value showed negative correlation with water content and soil organic matter content,and showed positive correlation with silt content.Philip model parameter s and Horton model parameters k showed a positive correlation with soil initial infiltration rate,steady infiltration rate.Kostiakov model parameters a have a highly positive correlation with soil initial infiltration rate and steady infiltration rate.Using SSE,RMSE,R,ME,EF and W,the infiltration model fitting value in the different water head and different soil depth were assessed and analyzed.At the end of the day,we come to the conclusion the fitting degree of Kostiakov model used to study the grass soil infiltration in the Babao river basin is best.(6)Between the soil initial infiltration rate,steady infiltration rate and clay,silt,soil organic matter,water content,the conversion function model was established and used to analysis and evaluation.Through the model,the transformation of soil infiltration rate from point to region in Babao river basin was realized.It is concluded that the spatial distribution of soil infiltration rate showed the patch shape characteristics in the basin.