Impact Of Climate Change On Agricultural Irrigation Water Requirement In Continental River Basin

At present, the global climate is gradually warming as the main characteristics of thesignificant change, in China the climate have changed dramatically in recent years, with theaddition of the shortage and imbalance of water resources, cause the loss of agriculturalproduction and the pressure of food security. Studying the influence of climate change onirrigation water requirement has the vital significance for responding to climate changereasonably, developing water-saving agriculture and adjusting agricultural structure incontinental river basin.Shiyang river basin is a typical continental river basin, and it is located in the ecologicalfragile and climate-sensitive area, the production water occupies ecological water, anddesertification problems are prominent, which seriously restricting the sustainabledevelopment of agriculture and industry in this basin, so this article set shiyang river basin asan example. Using the Penman-Monteith formula to calculate the ET0during1951-2012.While ET0and precipitation in2020s,2050s and2080s are downscaled fromHadCM3(Hadley centre Coupled Model, version3) outputs under A2and B2emissionscenarios, as well as NCEP by SDSM (Statistical Downscaling Model) with the historicaldaily weather data collected from the11meteorological stations located in and aroundShiyang River Basin during1951—2012. The spatial distribution and temporal trend in ET0and precipitation are investigated by Inverse Distance Weighted Interpolation and Kendall test,respectively. Based on the present situation of planting structure, the average net irrigationwater requirement, the average total agricultural water consumption, and the total netirrigation water requirement in the administrative regions in Shiyang River Basin arecalculated and analyzed. The main research contents and conclusion are as follows:(1) The Penman-Monteith equation is employed to calculate daily ET0at present, thespatial distribution and temporal trend in ET0and precipitation are investigated by InverseDistance Weighted Interpolation and Kendall test, respectively. The results show that theannual mean ET0in Shiyang River Basin is1061mm, the annual mean ET0presents upward trend from southwestern Qilian mountain to northeastern oasis and plain, the annual meanprecipitation in Shiyang River Basin is241mm, its distribution trend is contrary to ET0, theannual mean ET0presents upward trend, and precipitation presents upward trend.(2) Using HadCM3outputs as well as NCEP, and the statistical downscaling modelSDSM, HadCM3projects an ET0increase of6%,14%,23%under A2scenario in the2020s,2050s and2080s, respectively; while it projects an ET0increase of7%,12%,17%under B2scenario; An obvious amplification is detected in the southeast region; In2050s and2080s,the increase under B2scenario are lower than those under A2scenario. It will be a significantincreasing trend in ET0in the future and more pronounced after2050s. ET0shows anincreasing tendency from southwest to northeast gradient.(3) Using HadCM3outputs as well as NCEP, and the statistical downscaling modelSDSM, HadCM3projects an precipitation decrease of5.1%,13.2%,19.3%under A2scenarioin the2020s,2050s and2080s, respectively; while it projects an precipitation decrease of6.2%,10.6%,13.2%under B2scenario; In2050s and2080s, the increase under B2scenarioare lower than those under A2scenario. It will be a significant decreasing trend inprecipitation in the future and more pronounced after2050s. Precipitation shows an increasingtendency from central section to west and southeast gradient.(4) I shows an increasing tendency from southwest to northeast gradient for wheat, maize,sweet pepper, cotton, sesame and apple. The crops except maize and cotton show anunremarkable increasing temporal trend. Using HadCM3outputs as well as NCEP, and thestatistical downscaling model SDSM, HadCM3projects an I increasing tendency fromsouthwest to northeast gradient for wheat, maize, sweet pepper, cotton, sesame and apple. Thecrops all show a remarkable increasing temporal trend, and the increase under B2scenario arelower than those under A2scenario.(5) The average total agricultural water consumption(Wt), and the total net irrigationwater requirement(IN) in the administrative regions in Shiyang River Basin are calculated, thepresent Wtand INare15.42×108m3and12.65×108m3in the whole basin, under A2emissionscenario, the Wtand INare15.53×108m3and13.45×108m3in the whole basin in2020s,16.65×108m3and15.02×108m3in2050s,18.18×108m3and16.94×108m3in2080s. Whileunder B2emission scenario, the Wtand INare15.56×108m3and13.55×108m3in the wholebasin in2020s,16.34×108m3and14.63×108m3in2050s,17.00×108m3and15.51×108m3in2080s.(6) Investigating the influence of climate change on dry and wet conditions andagriculture in Shiyang River Basin can provide countermeasures such as developing water-saving agriculture and adjusting agricultural structure.