Temporal And Spatial Distribution Of Crop Evapotranspiration In Shiyang River Basin

Shiyang River Basin is one of the three largest interior river basins in the HexiCorridor of Northwest China, with the development of industry and agriculture, waterdemand increased dramatically, and contradiction of water supply and demand becamemore and more severe. "No irrigation, no agriculture"is a typical trait for Shiyang RiverBasin and agriculture is a leading water consumer. In 2000, the total consumption of allsocial and economic departments was 2.854 billion m3, among it, 2.455 billion m3 wasconsumed on irrigation, which amounted to 86.02% of the total water volume. Study ontemporal and spatial distribution of regional crop evapotranspiration is of great scientificsignificance on improving benign cycle of compound system of waterresources-ecology-economy-society, realizing sustainable development of agriculture inthe basin, and sustainable utilization of water resources in arid areas. The followingcontents were studied in the thesis: â‘ The meteorological factors' variation trend of Shiyang River Basin in the recent 50years was analyzed. Except the precipitation of Tianzhu station basically had no variation,mean temperature, mean maximum temperature and precipitation of other stations allshowed a trend of increase. Sunshine hours of Gulang had unobvious increase, and those ofLiangzhou had unobvious decrease, while those of other stations all had obvious increase.Annual evaporation of Gulang had a trend of increase, which was contrary to that of otherstations. Variation of average relative humidity of every station was not obvious, averagewind speed of Gulang was relatively stable, that of Tianzhu increased obviously, and thatof other stations declined very obviously. â‘¡Penman-Monteith method which recommended in FAO-56 was adopted tocalculate monthly ET0 of Shiyang River Basin and its nearby stations over years. It can bedrawn that ET0 of Shiyang River Basin varied relatively significant over months, and totalET0 from May to August covered a large percentage, to about 50%, of total ET0 of a wholeyear. The variation of ET0 over years was also relatively great, except that of Liangzhouand Sunan showed a trend of significant decrease over years, that of other stations allshowed an inverse trend of increase. ET0 of Gulang reached peak value step by step afterits lower value in later 1970's, and that of Minqin, Tianzhu, Yongchang was low in later1980's, while that of Liangzhou and Sunan was low in later 1980s', and that of everystation in 1990's increased to some extent compared with the values in 1980's. ET0 hasgreat correlation with average relative humidity, annual evaporation and average windspeed in every station. Spatial variation of ET0 values is also obvious and the value isincreasing from mountainous area to oasis plain in Shiyang River Basin. ET0 has asignificant negative correlation with altitude. â‘¢Single crop coefficient method recommended in FAO-56 is adopted to calculatespring wheat evapotranspiration in Shiyang River Basin. During the whole growth periodof spring wheat of every station, ETc values varied relatively great over years, the trends ofETc increase or decrease were not obvious in these stations. ETc values were low duringthe later 1980's and had an increase to some extent during 1990's. Variation of ETc overyears was milder than that of ET0 in every station. Spatial variation of ETc was alsorelatively significant during the whole growth period of spring wheat in the basin. AverageETc over years showed a trend of increase from mountainous area to oasis plain, whichwas same to average ET0 over years in the basin. â‘£Digital Elevation Model (DEM) of Shiyang River Basin was obtained usingGeographic Information System software MapGIS6.5 & ARCVIEW3.1. The spatialdistributed models of reference crop evapotranspiration and spring wheatevapotranspiration of Shiyang River Basin were built using surface analysis and spatialinterpolation function. As to the two models, the...