Comprehensive Benefit Evaluation Of Typical Small Watershed In Fangshan District In Beijing

Beijing’s mountainous area accounts for about 62%of the total area of Beijing,soil erosion and water loss has become an important factor restricting the development of mountainous area in Beijing.In recent years,the Beijing Municipal departments actively carry out soil and water loss prevention and control work,it results significantly.But lacking the benefit of small watershed comprehensive,scientific and reasonable evaluation.For the purpose of this study,five small watersheds of Puwa,Beijiao,Hongluogu Yunjusi and Beicheying in Fangshan District of Beijing were selected as the research object.Using GIS,field investigation,laboratory experiments,a combination of social questionnaires and data collection methods,by hydrological models,models of soil erosion,forest ecosystem services assessment specification methods,5 small watershed of hydrological effects,soil conservation,ecological service function,the main channel of small watershed hydrological characteristics and quantitative analysis of the environment,socio-economic situation,with a view to providing scientific basis for subsequent comprehensive management of small watersheds,Fangshan district,Beijing and theoretical reference.Specific research results are as follows:(1)Puwa,Beijiao,Hongluogu,Yunjusi and Beicheying small watershed after comprehensive management,compared with the small watershed before the comprehensive treatment,average annual runoff volume respectively reduced by 175,000 m3,148,000 m3,146,000 m3,263,000 m3 and 254,000 m3;Average annual runoff of small watershed in article 5 above coefficient around 0.02.Maximum peak flow reduce the 0.9m3/s,0.7m3/s,0.3m3/s,0.7m3/s and 0.6m3/s.This suggests that small watershed comprehensive management can effectively reduce the amount of surface runoff,reducing peak flow,lower coefficient of runoff in small watershed.After a small watershed,after July 21,2012 and July 20,2016,Fangshan district,two torrential rainfall-runoff simulation,5 small watershed in the "7.21" storm peak discharge rate cuts to 16%-35%,"7.20" storm and flood reduction rate for 16%-35%;Reduce storm-water runoff volume efficiency of 3.3%-7.1%and-103%respectively;In addition,5 of comprehensive harness of small watershed the hydrograph after than in the small watershed the hydrograph have some lag before,with peak time lag 30-150 minutes.(2)Use of soil water erosion models Fangshan 5,CSLE an assessment of the effects of small watershed comprehensive management of soil erosion intensity,Analysis for many years,for nearly 30 years the maximum average precipitation,as well as actual precipitation under three scenarios for the year 2005 and 2015,the spatial distribution of soil erosion modulus;Puwa,Beijiao,Hongluogu,Yunjusi and the small watershed in the Beicheying use the actual precipitation for the year,reduced soil erosion in 2015 than in 2005 respectively 2424,4406,53887,31206 tons and 10982 tons;Annual average precipitation,5 small degrees of erosion in the basin area of 0.93%-9.88%,Moderate erosion rate decreased by 0.24%-13.06%;Using a 30-year maximum rainfall,5 degrees of erosion in the watershed area of 3.09-4.01%,moderate erosion area 1.33%-7.89%.It is found that the soil erosion intensity is reduced in the next three years by 2015,and the soil erosion modulus changes obviously in the land use change.(3)On 5 article small basin comprehensive benefits real quality for calculation,Puwa,Beijiao,Hongluogu,Yunjusi and Beicheying small basin of conservation water maximum volume respectively is 175,000 m3/years,and 148,000 m3/years,and 254,000 m3/years,and 146,000 m3/years and 263,000 m3/years;annual of insurance fertilizer volume respectively for 10.16 tons,14.42 tons,136.37 tons,92.40 tons and 25.87 tons;plant annual solid carbon volume respectively for 2761.39 tons,2486.31 tons,2442.40 tons,1443.08 tonsv 2612.38 tons;releasing substances per year were 5774.92 tons,6656.26 tons,6538.70tons,3863.35 tons,and 6993.75 tons;forest produces the negative oxygen ion quality-4658.51×1018,2608.69×1018,3734.34×1018,2563.10×1018 and 3473.01×1018.(4)The results of the main channel evaluation of the small watershed show that the overall level of the main channel is better.There are 35.67%above Grade Ⅱ(good)and 60.07%above Grade Ⅲ,and 68.09%above Grade Ⅲ(middle),79.92%above Grade Ⅱ(above),and Grade Ⅶ(above)up to 97.59%;The level of the second grade(good)above the channel is 68.95%,the third floor(above)is 77.71%There are 54.25%above the river basin level(grade)and 54.6%for Grade Ⅲ and above 72.63%.The garbage collection,storage,transportation and treatment in the small watershed are unified management of the government,and the water quality index Ⅱ within the scope of surface water quality standards,a small number of channels in the water N03 exceeded the national drinking water requirements,the ecological environment is good.(5)According to the social and public data of 2015,the direct economic benefits and indirect economic benefits of the five small watersheds were calculated.After the comprehensive management of the small watershed,the economic production and investment ratio of the small puddle For the 23.56:1,24.08:1,69.95:1,15.44:1 and 26.33:1.5 small watershed 2007 to 2015,Engel coefficient decreased by 4.71%-12.21%,revenue growth of 21.60%-135.03%The proportion of agricultural land increased by 14%-23%,the per capita arable land area decreased by 0.018 hm2-0.03 hm2,the forest area increased by 0.146 hm2-0.699 hm2,and the survey occurred in 2015 was more than 85%.