| Objective and scientific evaluation of effectiveness of soil and water conservation in the region can not only assess the suitability of management strategies, methods and the validity accurately and control measures reliability but also provide important reference for management’s decisions and sustainable development of control measures. In this study, we evaluate the benefits of soil and water conservation since 1979 in Gullied Loess Plateaus based on the annual statistical data of the Soil and Water Conservation measures from 1980 to 2015, the first national water census in Gansu Province, and used 08 National Standard as a guide. Furthermore, the results of the Soil and Water Conservation which the Gullied Loess Plateaus has achieved for more than 30 years, the indicator system of comprehensive harness benefit of the Soil and Water Conservation, as well as the water diversion and soil conservation, economic, social and ecological benefits were analyzed, and soil and water conservation benefit of different times and counties were also evaluated by catastrophe progression method. The results have showed that:(1) By 2015, the controlled area has reached 56.37% in Gullied Loess Plateaus, and the number of soil and water conservation measures was as follow: 372300 hm~2(Terrace), 900 hm~2(dam field), 401000 hm~2(water conservation forest), 29900 hm~2(economic forest), 84500 hm~2(artificial grass), 39800 hm~2(closing measure).(2) The various measures of the Soil and Water Conservation of Gullied Loess Plateaus had cumulatively decreased runoff by 4.48×108 m~3 from 1980 to 2015, and reduced sediment by 0.72×108t. The total economic benefits of various measures of the Soil and Water Conservation had cumulatively generated to 293.28×108 yuan from 1980 to 2015, the economic benefit of terrace reached 85.67×108 yuan, forests 83.33×108yuan, water conservation forests 80.64×108 yuan and artificial grass 43.64×108 yuan. Moreover, the conservation measures have mitigated natural disasters and improved productivity and land use structure, adjusted the structure of production in rural areas as well as improved the people’s living standards. Additionally, it also reduced siltation of downstream river, improved soil fertility, soil structure and soil resistance to erosion by the storing rainfall runoff. Then effectively reduced the area of drought, floods and the lower Yellow River flood control pressure. As an illustration, the vegetation coverage increased to 33.98 percent that is 515 400 hm~2 in 2015 than 4.49 percent and 68 100 hm~2 in 1979.(3)Evaluation value of soil and water conservation benefits in Gullied Loess Plateaus increased from 0.298 in 1988 to 0.856 in 2011. Evaluation value of soil and water conservation benefits of all counties varied from 0.128 to 0.824 between 1988 and 2011. Benefits of soil and water conservation was poor integrally in 1988, Evaluation values of Jingchuan and Zhengning County whose values were 0.285 and 0.299 respectively were much higher than other counties. In 2000, Zhengning Country was the highest while Zhengyuan Country was the lowest. In 2011, Xifeng was the highest while Zhengyuan was the lowest. Compared to 1988, Xifeng County and Chongxing County whose evaluation values had increased by 0.663 and 0.673 respectively performed better than 2011. Evaluation value of Zhengyuan County increasing by 0.462 showed poorer performance. After 23 years of comprehensive treatment for soil and water loss, benefits of soil and water conservation of Gullied Loess Plateaus increased significantly. Otherwise, terraced construction had little contribution on improvement of benefits of soil and water conservation while Grain for Green Project had much contribution after 2000. |
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