Responses Of Agriculture Water Resources Supply And Demand Balance To Environment Change In Shiyang River Basin

Water resources is necessary to economic development and social progress.Under the influence of climate change and human activities,in China water resources problem have become increasingly prominent.Agriculture sector is affected by climate change directly,on the one hand agriculture water is diverted to non-agriculture sector and waster seriously,on the other hand the agriculture water resources requirement is uncertainty under the effect of climate change.All of this are changing the agriculture water resources supply and demand balance and endanger the healthy and sustainable development of agriculture.Shiyang river basin is a continental river basin whose irrigation agricultural was developed earliest and the development of economic and society were restricted seriously by water resources.Studying the driving factors of irrigation water requirement and responses of agriculture water resources supply and demand balance to environment change can provide reference and decision support to control the scale of agricultural development,promote the region's coordinated development,respond to climate change reasonaly.This paper taken Shiyang river basin as an example,calculated wheat and maize net irrigation quota by the Penman-Montieth equation and the single crop coefficient method under the collection of date and trend analysis.The global sensitivity equation of net irrigation quota to six pivotal meteorological factors was derived based on Taylor's formula.The change of irrigation water requirement was decomposed into 4 driving factors including planting scale effect,planting structure,climate change and water saving engineering.The factors decomposition model for irrigation water requirement was established based on the extended Kaya equation.The Logarithmic Mean Divisia Index(LMDI)decomposition method was used to quantitatively analyze the driving factors for changes in agricultural water requirement.Two different decomposition methods of LMDI,additive decomposition and multiplicative decomposition,were applied to calculate the effect value of four driving factors for irrigation quota change.At the last of this study,a system dynamic model for the agriculture water resources supply and requirement balance was established based on the relationship between the water system internals.This SD model considered economic and social development,population increase and climate change.Using this SD model the Change of the agricultural water shortage rate was predicted under environment change in each administrative region of Shiyang River basin.The main research contents and conclusion are as follows:(1)The spatial distribution characteristics of sensitivity spatial distribution were contrasted and analyzed.The results showed that the effective precipitation was the most sensitive to wheat and maize irrigation quota,followed by relative humidity,solar radiation and wind speed,the highest temperature and the lowest temperature were the least sensitive variable.the different sensitivity of irrigation quota to the effective precipitation and ET0 existed between wheat and maize in different areas of Shiyang River basin,because of the influence of growing periods,climatic and topographical conditions.As to wheat,all of the meteorological sensitivity factors were greater in the upper than the middle and lower,but except the factor of wind speed,and the sensitivity to effective precipitation was greater than ET0 in the upper,but it was opposite in the lower of Shiyang River basin.For maize,the sensitivity to effective precipitation and ET0 were on the decrease,but the sensitivity to effective precipitation was always stronger than ET0.(2)The effect value of four driving factors for irrigation water requirement change was calculated in different periods from 1995 to 2012 in Wuwei city,and the main driving factors could be obtained by comparing the effect values corresponding to different influential fators.The main results showed that: During 1995-2012,the planting structure in Wuwei city was adjusted by reducing the planting area of wheat and increasing planting area of maize and cotton which consume less irrigation water than wheat.Compared with 1995,The amount of irrigation water requirement in 2012 reduced by 5.023×108 m3 in Wuwei city which was resulted from 2.435×108 m3 of the planting scale effect,-3.994×108 m3 of planting structure effect,-1.286 ×108 m3 of climate change effect and-2.178×108 m3 of water saving engineering effect.From the effect value of different crops in the counties of Wuwei city,each crop has different effect on the change in irrigation water requirement.Wheat had the negative impact and played a prominent role to decrease in the irrigation water requirement during 1995 to 2012.In addition,four driving factors in different periods played different role to change in irrigation water requirement in the counties of Wuwei city and the main effect factor on changing in the irrigation water requirement was different.But the planting structure always had the inhibitory effect on increasing irrigation water requirement obviously except Liangzhou during 2000-2005.It proved that the planting structure trended to be reasonable ceaselessly over the recent years in the counties of Wuwei city.(3)Bason on the balance of agriculture water resources supply and demand,a SD model was eatablished and analyzed in different development pattern.The main results showed: The change of agriculture water resources was different under the same climate scenario with different development pattern,but the agricultural water requirement and supply had trended lower without significantly.Jinchang was the city which economic and social development rapidly and water for non-agriculture sectors had a great effect on agricultural water supply.For Wuwei city,the development of agriculture is prosperity and water requirement of non-agriculture sectors were increasing in recent years,but there did not much affect the agricultural water supply than Jinching city.Under the same climate scenario,economic and social development with low speed was the most water shortage,followed by economic and social development with middle speed and fast speed in Wuwei city.(4)The SD model for agriculture water resources supply and demand was analyzed under different emission scenarios.The future development was confirmed that refered to connotation of each emission scenarios.The main results showed: Responses of agriculture water resources supply and demand balance to A2 and B2 emission scenarios was different in each administrative region of Shiyang River basin.Water shortage rate of Jinchang city was more serious as a whole under A2 emission scenario than B2 emission scenario,but it was opposite in Wuwei city.In Wuwei city,there was only one medium water shortage year with water shortage rate was 24.9% under A2 emission scenario,but had more medium water shortage years under B2 emission scenario,especially in 2023,the water shortage rate was 33.2%.