长江流域农业用水效率研究:基于超效率DEA和Tobit模型

提高农业用水效率对于农业可持续发展和保障粮食安全具有重大意义。考虑降雨量中绿水资源对农作物生长的重要性,将绿水资源纳入农业用水总量,全面分析长江流域农业用水效率变动趋势。基于1998~2011年长江流域10个省份的面板数据,运用超效率DEA和Tobit模型对流域农业用水效率进行了测度和影响因素的检验。研究发现:(1)在研究期间内,长江流域农业用水效率呈现出波段式上升态势;流域各区段的用水效率呈下游、上游、中游依次递减的区域分布格局。(2)灌溉费、节水灌溉技术和农业对外开放度对流域农业用水效率有显著的正向效应;人均水资源量和年降水量均对流域农业用水效率有负向关系,但只有降水量在统计上显著。研究结果表明应当提高长江流域,尤其是中上游水资源禀赋较高地区的农业用水效率;在农业节水的具体政策方面,调整农业灌溉水价、加强农业技术创新能力和扩大农业经济对外开放程度能够取得较为显著的节水效应。

RESEARCH ON AGRICULTURAL WATER USE EFFICIENCY IN YANGTZE RIVER BASIN BASED ON SUPER-EFFICIENCY DEA AND TOBIT MODEL

Water resources in Yangtze River Basin is richer, but water of per capita is only 30 percent of the world average. How can we improve agricultural water use efficiency and overall agricultural production capacity in Yangtze River Basin? It is not only an urgent issue in the current water conservancy work, but of great significance to agricultural sustainable development and food security. Because green water resource of annual precipitation is of great importance to crop growth, the green water is included in total agricultural water consumption different from the one from current statistics. Ten provinces are taken into consideration except Tibet autonomous region (TAR) and Zhejiang province because TAR is taking as not agriculture but the livestock industry and most area of Zhejiang lies in Southeastern rivers. Thus the research objects include Shanghai, Jiangsu, Anhui, Jiangxi, Hubei, Hunan, Yunnan, Qinghai, Chongqing and Sichuan. Then some indicators, for example amounts of fertilizer, sown area of agricultural crops, agricultural machines, agriculture labor and agriculture water consumption, are selected so as to estimate agricultural water use efficiency of Yangtze River Basin. Based on the panel data of 10 provinces in Yangtze River Basin from 1998-2011, agricultural water use efficiency is estimated by the method of super efficiency DEA. On the basis of the efficiency estimation, the factors of agricultural use water efficiency are tested by Tobit model. Based on the water efficiency measurement method of Hu &Wang(2006), DEA model is used to measure agricultural water use efficiency from basin level. Moreover, according to features of water resources and agricultural water use, etc., dummy variables S1， S2， S3 are introduced in Tobit model. In order to know the deeper causes of the change of the agricultural water efficiency, some factors are observed including the water resource of per capita, annual precipitation, crop planting structure, water saving irrigation technology, irrigation fees and opening up of agriculture. Some conclusions are as follows: ①During the research period, agricultural water use efficiency shows rise trend in waves; the efficiency of upper，middle and low reaches in Yangtze River Basin is on the decrease. ②Irrigation fees, water saving irrigation technology and opening up of agriculture have significant positive effects on the efficiency. And annual precipitation has significant negative effects on the efficiency. In addition, water resource of per capita has negative effects on the efficiency, but not statistically significant. Results show that improving agricultural use efficiency in Yangtze River Basin, especially the middle and upper reaches, in which water resources is richer; in aspect of agricultural water saving policies, adjusting agricultural irrigation water price, strengthening agriculture technology innovation and expanding opening up of agriculture can get remarkable water saving effects.