The Impact Of Future Climatic Scenarios On Crop Production Water Footprint

Climate change has had a significant impact on crop production and agricultural water consumption.The assessment of the evolution and characteristics of regional agricultural water use under future climate scenario could provide bases for regional water resources management and reactions to climate change.Water footprint theory could help to clarify the type,quantity and efficiency of water resources consumed by agricultural production processes,and thus is an important factor to the sustainable utilization of water resources.This paper used the Statistical DownScaling Model(SDSM)to predict the climatic factors of Hetao Irrigation District(HID)under A2(under this scenario the global population continue to increase,and the economy grows fast)and B2(under this scenario the growth of population is slower than under A2,and sustainable development strategy is adopted)scenarios,and based on future climatic factors this paper calculated the reference crop evapotranspiration(ET0),crop water demand(ETc)and effective precipitation(Pe)during the growth period of crops.The future climatic factors were then inputted to the crop model AquaCrop to simulate the future crop yield in HID.The future crop production green water footprint(WFgreen)and crop production blue water footprint(WFblue)were quantified by future crop ETc,Pe and yield.In the end,the paper analyzed the supply and demand of water resources in HID in the future.The main conclusions and results are:(1)Climate in HID will become warmer and wetter.Temporally,the average annual temperature in HID under A and B scenarios would increase by about 3 ℃ and 2.2 ℃respectively,while the average annual precipitation would increase by 18 mm and 22 mm respectively.The average sunshine hours,relative humidity and wind speed in HID would remain almost the same in the future.Spatially,the spatial distribution of the meteorological factors would not much different from current.Affected by climate change,especially theincrease of temperature,averagely the ET0 in HID would increase by about 6% under A scenario and about 3% under B scenario by the end of this century.(2)The crop water irrigation water demand in HID in the future would rise because of climate change.The crop ETc will show an increasing trend,and the increment under A scenario will higher than that under B scenario.Oil plant has the greatest ETc increment among the 6 main corps in HID and its ETc will rise 7%-15%;while with the increment of 3%-10%,wheat has the lowest ETc increment.Pe would mainly show a do wnward trend in the future.With the combined affection of increased ETc and decreased Pe,crop irrigation water demand will show an increasing trend.If the planting structure remains unchanged in the future,by the year 2030,the net crop irrigation water demand in HID would increase 376 million m~3under A scenario and 276 million m~3 under B scenario respectively.The agricultural water pressure in HID will be increasing over time.(3)The WFgreen,WFblue and WF of crops will show a downward trend.In the future,the Pe would decrease will the crop yield increase,so the WFgreen of crops would fall.The increment of crop irrigation demand would be lower than the increment of crop yield,so the WFblue of crops would descend.The WFblue account for 85% of the total crop WF,so the changing rate of crop WF would be basically the same as that of WFblue.Among the 6 main crops in HID,the linear decline rate of WF of sunflower would be the largest,which is about0.02(m~3/kg)/10a;and the linear decline rate of WF of wheat would be the smallest,which is about 0.01(m~3/kg)/10 a.Sunflower would have the largest WF,which would be about1.98m~3/kg under A scenario and 2.06m~3/kg under B scenario;while maize would have the lowest WF,about half of that of sunflower.(4)There would be an increasing pressure on agricultural water use in HID in the future.The gray model showed that domestic water use in HID would be relatively small,which would remain at 100 million m~3;however,industrial water use would be doubled by the year2030,reach up to 318 million m~3.Besides,the simulation results showed that the amount of available agricultural water in the future would be decreasing,with an average decrease rate of 16 million m~3 per year.Under the conditions of an increasing crop irrigation demand and decreasing available agricultural water in HID,and by the year 2030,HID may face a water vacancy about 190 million m~3 to 340 million m~3,which will put threat to agricultural water security.(5)Reasonable adjustment of planting structure is conducive to regional agricultural water conservation.If the planting area of cash crops increase by 5%,fruits and vegetables increase by 3% and grain crops decrease by 9%,in the year 2030 the net irrigation water demand in HID would be 2.50 billion m~3 and 2.41 billion m~3 under A and B scenariorespectively.If the planting structure remains unchanged,the net irrigation water demand in HID would reach up to 2.69 billion m~3 and 2.59 billion m~3 in the 2030 under A and B scenario respectively.Thus,the adjustment of planting structure will have an impact on the regional agricultural irrigation water demand,and rational adjustment of crop planting structure is conducive to the alleviation of regional agricultural water pressure.