Monitoring And Evaluation Of Soil And Water Conservation And Ecological Restoration In Small Watersheds In Earth-rock Mountain Areas

Soil and water loss makes the ecological environment worse and the soil structure destroyed,which is an important bottleneck restricting the development of agriculture and even the society.This study took the small watershed of Liyu earth-rock mountainous area in Jinzhong,Yushe County,Shanxi Province as an example.Based on Envi5.1,the Normalized Difference Vegetation Index(NDVI)of the 4 issues of the high-fraction Satellite Remote Sensing Image of liyu watershed on October 13,2014,September 29,2016,November 1,2018 and October 28,2019 was extracted.Furthermore,the vegetation coverage(FC)of stage 4 was estimated by dichotomy method,and the temporal and spatial variation characteristics of FC in small watershed were revealed.The effect of Comprehensive Management of Soil and water conservation in Liyu small watershed was analyzed by field investigation and analytic hierarchy process.The rainfall and flood situation in the study area was simulated by Mike SHE and Mike11 model,estimation of soil erosion modulus by Arcgis10.0.The conclusion is as follows:(1)After the implementation of soil and water conservation measures,NDVI and FC in the study area generally increased at first and then decreased,and the distribution of FC in each year increased from southwest to northeast.The average FCs of 2014,2016,2018 and 2019 were 0.2235,0.6735,0.3919 and 0.2092,respectively.The vegetation improved significantly in 2016,with the largest growth rate of 201.34%.FC in 2018 decreased by 41.81%compared with 2016;Affected by severe drought and human factors in 2019,vegetation degradation in 2019 was more obvious than that in 2016.(2)Fc in the study area is closely related to rainfall,altitude,slope,slope aspect and land use type.FC has a close relationship with rainfall,with a correlation coefficient of 0.6468,and a negative correlation with air temperature,with a correlation coefficient of 0.3825.Topographic factors have different effects on different vegetation types.Pinus tabulaeformis is suitable to grow on the eastern slope greater than 45°,and it is better to grow on the western slope and the northwest slope with a slope of 20°-35°.Prunus almond has higher Fc on the sunny slope of northeast slope,east slope and south slope,while the economic forest has higher Fc on the western slope and southwest slope with a slope greater than 45°.There was a positive correlation between the area of water area,forest land,grassland and cultivated land and the basin FC,while there was a negative correlation between the area of construction land and unused land and the basin FC.(3)After the restoration of soil and water conservation measures,the soil erosion in the watershed changed from moderate to slight and mild erosion.The average annual soil erosion modulus in 2014,2016 and 2018 were 377 t/km~2,476.09 t/km~2 and 208.73 t/km~2,respectively,all of which were slight erosion and light erosion,and there was no moderate or above erosion intensity in the basin.Before the implementation of soil and water conservation measures,the average annual erosion modulus in the basin was 2670 t/(km~2·a),which was mainly moderate erosion,indicating that the soil and water conservation measures played a powerful role in the inhibition of soil and water loss.(4)The flood peak discharge increases gradually with time under the condition of heavy rain in different recurrence periods.Under the condition of one rainstorm in five years,2016 decreased by 30.89%and 44.76%compared with 2014 and 2018 respectively,and 46.54%and 56.08%compared with 2016,and 29.23%and 37.72%respectively compared with 2014 and 2018 respectively,under 100-year heavy rainfall conditions,it decreases by 21.52%and 29.37%respectively,and by 6%and 10.00%respectively under200-year heavy rainfall conditions.(5)The scores of economic,ecological and social indicators and comprehensive benefits of the study area increased year by year.In 2014,2016 and 2018,the economic benefit score was 0.0066,0.0412 and 0.2098,the ecological benefit score was 0.1189,0.3361 and 0.3681,the social benefit score was 0.0398,0.1371 and 0.2004,and the comprehensive benefit score was:0.0749,0.226 and 0.295.It shows that after soil and water conservation measures,it has really brought positive influence to society,ecology and people’s life.