Characteristics Of Drought Evolution And Its Impact On Agricultural Water Use In Northern Shaanxi Province

Northern Shaanxi is located in an arid and semi-arid area and agriculture is dominated by dry farming,which has great potential for agricultural development.However,due to natural conditions such as climate and human activities,the region has serious soil erosion and a fragile ecological environment.Under the backdrop of global climate change and the rapid development of energy and chemical production in northern Shaanxi,the threat of drought to the ecological environment and economy in northern Shaanxi is particularly serious.Clarifying the spatial and temporal characteristics of drought in the area and exploring the possible changes of drought situation in the future are of great significance for the local formulation of disaster prevention and mitigation strategies and industrial and agricultural production planning.Based on historical meteorological data and a multi model ensemble mean value,by detrending,Mann-Kendall trend test?MK?,empirical orthogonal function spatial analysis?EOF?and wavelet analysis,this paper analyzed the temporal and spatial variation characteristics of drought in northern Shaanxi during the historical time period?1960-2018?and the future time period?2020-2100?;compared the changes in crop production water footprint in typical years;evaluated the future trend of agricultural water demand in the region.The main research results obtained are as follows:?1?The application of the Standardized Precipitation Evapotranspiration Index?SPEI?in the region is superior to the Standardized Precipitation Index?SPI?and self-calibrated Palmer Drought Index?sc-PDSI?.In the historical reference period?1960-2018?,SPEI in northern Shaanxi showed a significant decrease trend.The interannual dry and wet changes in the northern Shaanxi region during the historical period?1960-2018?can be divided into two periods,that is,the humid period was mainly from 1960 to 1990,while the dry period was mainly distributed from 1990 to 2018.And the spring drought was prominent in the seasonal drought.The EOF spatial decomposition of SPEI index anomalies shows that the overall dry or wet changes in northern Shaanxi is generally consistent.The western and southeastern regions are sensitive areas where drought occurs.The dry and wet spatial distribution in Winter has the greatest impact on the whole year.The main period of drought change in the past 59years was 3.2a.And the main cycle of change is 3.2a.?2?The multi model ensemble mean value provides a better simulation of precipitation and temperature in northern Shaanxi.Under future scenarios,precipitation,temperature,and annual average ET₀ in northern Shaanxi all show a significant increase compared to the historical reference period,and the growth rate under the RCP8.5 scenario is greater than the RCP4.5 scenario.In terms of spatial distribution,the west is the region with the largest increase in precipitation and temperature,while precipitation in the north has decreased.ET₀ in northern Shaanxi will increase in all future periods,and the western region is still the region with the largest increase in ET₀ changes.Therefore,the western region is the region with the greatest impact of future climate change in northern Shaanxi.The western region may be the region with the greatest impact of future climate change.?3?In the future climate scenario,the region will continue to maintain a decreasing trend of drought index,and seasonal drought will intensify.Temperature is the main factor affecting the future drought in the region.By EOF analysis,under RCP4.5 scenario the northern eigenvalue is higher,which is a sensitive area for future droughts.The annual dry and wet spatial distribution in northern Shaanxi may be slightly affected by winter.And under RCP8.5scenario,the central eigenvalue is higher,which is a sensitive area for future droughts.The annual dry and wet spatial distribution in northern Shaanxi is greatly affected by spring and summer.Wavelet analysis shows that under the RCP4.5 scenario,the main cycle of drought change is 3.8a;while under the RCP8.5 scenario,there is no main cycle of drought oscillation,and drought will become a normalized event.?4?The demand for agricultural water in the north of Shaanxi will increase in the future.The demand for agricultural water is estimated from the difference between ET₀ and P?ET₀-P?,and the change in demand is analyzed using the MK trend test.Under the RCP4.5 scenario,the increasing trend in north in spring is obvious.Under the RCP8.5 scenario,the range of demand for agricultural water in the northern Shaanxi is increasing,showing a more severe water demand.Among them,the summer water demand has increased significantly,mainly concentrated in the north,west and south parts of northern Shaanxi,which is a serious threat to the growth of maize the main grain crops in northern Shaanxi.The risk of agricultural drought and climate drought in summer increases.