Study On Temporal And Spatial Distribution Of Crop Evapotranspiration In Plain Of The Main Heihe River Middle Reaches

Heihe River basin is second big inland river basin in our country. Along with industry and agriculture rapid development in recent years, various departments' water consumption grows suddenly, the water used contradictory causes the downstream ground water level to drop prominently, the rivers are dry, ecological environment worsening. The evapotranspiration is an important water cycle factor, which is playing the vital role in producing regional meteorology drought, the hydrology drought as well as the agriculture drought. This research initially will explore the temporal and spatial distribution rule of area crops evapotranspiration, which will provide the reference for arid area scientific research questions and the production actual problem and irrigation farming development pattern, system formulation, agricultural structure adjustment, ecology construction, which has the vital scientific significance for promoting the water resources-ecology-economy-society multiplexed system positive cycle, realizing the agricultural sustainable development and the arid area water resources sustainable utilize. This article draws following conclusions:(1) Using FAO the Penman-Monteith formula and the near 40a meteorological data of Heihe middle reaches 4 meteorological stations(Ganzhou(Zhangye), Gaotai, Linze, Minle) and neighbor upstream 2 meteorological stations(Sunan and Shandan), this article calculated various stations evapotranspiration potential separately, determined evapotranspiration coefficient, and obtained the various stations actual evapotranspiration quantity in the recent 40a. Combining with three different issue' remote sensing images data of Ganzhou(Zhangye), Gaotai, Linze, Minle of Heihe River middle reaches, this article analyzed the land use change of in 1967, 1986 and 2000. The result indicated that the farmland total area of these four locals increases year after year, the increase rate is 16.87km~2/a, grassland area shows reducing tendency from 20 century 60's to the 90's, the average year reduces 38.25 km2. The saline and alkali land, the bare land, the bare rock gravel place area take on increase tendency. In 1967, in 1986 and 2000 farmland crops actual total evapotranspiration quantity was 11.13×10~8m~3, 13.16×10~8m~3 and 14.91×10~8m~3, respectively. Along with the recent years climate continuous getting warm and farmland area gradually increase, the total evapotranspiration quantity of farmland also assumes the increase tendency.(2) The evapotranspiration quantity of Heihe River middle reaches main current area four stations assumes the reduced tendency, in which Zhangye and Minle change scope is not big, Gaotai and Linze assume the tendency which reduces obviously. It presents as a whole increasing tendency from the upstream to the downstream, from the mountainous area to the plain in space. The annual evapotranspiration quantity of Heihe River middle reaches main current area four stations assumes as a whole reduces the tendency in the time distribution. The summer evapotranspiration quantity is bigger than other seasons far. The monthly mean crops actual evapotranspiration quantity maximum value appears in the summer (in June or in July), the minimum value appears in the winter (in December or in January).The terrain, the climate and the vegetation or the land use situation are the primary factor which affects evapotranspiration quantity space variability. Through analyzed Heihe River middle reaches main current area topographical conditions and nearby 6 meteorological stations' latitude and elevation indicated to the crops actual evapotranspiration quantity influence that, In January, October, November and December crops actual evapotranspiration quantity displays certain negative correlation relations with the latitude, and displays certain positive correlation relations with the elevation. In the recent 40a, The Heihe River middle reaches plain regional climate transforms to the warm wet climate, the precipitation increases, the air humidity increases, the wind speed reduces are the important reason that this area crops actual evapotranspiration quantity assumes reduced tendency. In addition, this area vigorously governed wilderness in recent years, returned land for fanning to forestry or grassland, also had certain influence to this area evapotranspiration quantity.(3) This article uses the surface, the analysis and the spatial interpolation function method of geographic information system software ARCVIEW3.2 to establish the spatial distributional model of reference crop evapotranspiration quantity in the basin. There are very big different among the results which is producted by regression method, the Spline interpolation and IDW. Because the scope of research area is much bigger, the scale of the model is also bigger, as well as meteorological stations are few, so the Spline and IDW aren't fit this river basin. The result which is gotten by regression method are best.