According the test in 1990,without plant-fencing the annual runoff amount is 4 210.44 t/hm~2,the runoff amount of silt is 1 726.61 t/hm~2.The annual amount of surface flow with plant-fencing is 7.2% of that without plant-fencing,the surface flow amount of silt is 1%.
The paper conducts identification,presentation and extraction on three approximate period series of natural annual runoff rate of 1470~2002,1919~2002 and 1949~2002 of Sanmenxia Station on the Yellow River by using the methods of autocorrelation and variance spectral density analysis.
Results showed that average soil water content,soil water storage capacity,yearly runoff,runoff coefficient of flood peak in Chinese fir plantation were 404.4 mm,1 220 t/hm 2,474.1 mm,0.19 respectively.
Whereas after clearcutting average soil water content and soil water storage capacity were found to reduce 6.1%and 29.51% respectively,while yearly runoff and runoff coefficient of flood peak increased about 13.42% and 29.63% respectively.
In addition, through plotting the hydrograph of mean annual and natural yearly runoff and the residual mass diagram of frequency factor from 1919 to 2002 in Sanmenxia Station, 2 continuous low water periods from 1922 to 1932 and from 1990 to 2002 are obtained.
(2)Pollution loading of dissolved N and P in ChaoHu lake watershed could be evaluated through export model of N and P after annual runoff volume was work out according to SCS model.
(3) The total annual runoff volume at 3 hydrological stations in the Kaxgar River Basin has been in a significant linear increase trend since recent 47 years,and the decennary increase rate is 3.0%.
The results shown that the effect of precipitation variations in 1970s and 1980s to the natural annual runoff volume is not clear, while it becomes greatly notable since 1990s and the effected range reaches to 10%~20%.
This paper analyzes the change trends of temperature and precipitation in the Kaxgar River Basin,alluvial plain and Pamirs and of the annual runoff volume at the debouchure hydrological stations in the river basin using the data observed by 7 meteorological stations and 3 hydrological stations in the Kaxgar River Basin.
In the Yarkant River Basin,the linear increase of annual runoff volume of the Tiznap River is significantly only,and that of the Yarkant River is not so significant although the annual runoff volume of the river is in a linear increase trend.
According the test in 1990,without plant-fencing the annual runoff amount is 4 210.44 t/hm~2,the runoff amount of silt is 1 726.61 t/hm~2.The annual amount of surface flow with plant-fencing is 7.2% of that without plant-fencing,the surface flow amount of silt is 1%.
Annual runoff amount of river basin is a significant basis for water resources evaluation and its allocation in reason,while the water reduction function of artificial afforestation is a foundation of estimating influences of soil and water conservation on annual runoff amount.
Annual runoff amount of river basin is a significant basis of water resources evaluation and its allocation in reason, while water reduction norm of soil conservation is a foundation of estimating influences of soil and water conservation on annual runoff amount of river.
The result of experiment on the spot indicated that when 30 thousand, 45 thousand and 75 thousand kg of barnyard manure per hectare are applied on the cultivated loess land with slope of 10 ~ 12 degree, the annual runoff amount decreased by 13.3%, 20.5% and 34% and the annual soil loss amount decreased by 32.3%, 33.7% and 35.4% respectively in comparison with the contrast area, the decrease rate increased positively with the manure amount applied;
The annual runoff amount and constant runoff amount have significantly negative correlation with year and all soil and water conservation measures. The relationships between annual runoff amount and annual precipitation, precipitation in flood period (during May to September) and effective precipitation (daily amount more than 10?mm) are very significantly positive, but the relation of constant runoff amount with annual precipitation, precipitation in flood period and effective precipitation are weak.
The stability of sample estimates of statistical parameters was analyzed for segments of the initial time series of annual runoff volumes of the Volga River at Volgograd for 1881/1882-1994/1995.
The conclusion is made that there are statistically significant variations in the annual runoff of the Volga, caused by both natural-climatic and anthropogenic variations in the hydrological cycle.
For example, variations in the annual runoff of the Yenisei River have a distinct nonmonotonic trend: the runoff systematically decreased till the late 1950s and increased since the late 1960s.
An analysis of the standing biomass data after 5?years of growth indicated that the yearly runoff floods contributed significantly to increase the total above ground biomass.