| Influenced by the changing environment,the trend,mean value and/or variance of hydrological series have changed significantly in Loess Plateau,which leads to the deviation from the assumption of stability and the inconsistency of height.With the accumulation of impacts,the driving factors of the inconsistency change also show the complex and changeable characteristics of interaction,which leads to the increasingly uncertain changes of the hydrological sequence,which seriously threaten the water safety guarantee and high-quality development of the region or watershed.Therefore,how to effectively identify the characteristics of hydrological inconsistency changes in complex change environment,quantitatively analyze the changes of driving factors and the complex impact of driving factors on runoff change have become the key to scientific response to the environmental impact of changes in arid and semi-arid areas and to effectively implement the high quality management of water resources in the watershed.This paper took the Tuwei River Basin with great vegetation cover change in Loess Plateau as the research object,analyzed the historical evolution law of hydrological meteorological and surface environment observation elements in the basin,estimated the key elements of water cycle,identified and diagnosed the inconsistency changes of hydrological meteorology and surface environment elements,established the cross driving relationship between runoff change and its driving factors(including hydrological and meteorological factors and surface environment factors),quantitatively analyzed the driving factor changes and the influence of driving factors on runoff change.At the last through setting up simulation scenarios,the coordinated evolution law of driving factors and runoff process under different scenarios was obtained.The main conclusions are as follows:(1)Mann-Kendall trend test results showed that the precipitation in Tuwei River Basin showed no significant downward trend from 1957 to 2010,the average temperature showed a significant upward trend,the potential evapotranspiration and runoff showed a significant downward trend,and the NDVI showed a significant upward trend.The main types of land use were grassland,cultivated land and unused land.Since 1995,most of the unused land had been converted into grassland,and the underlying surface of the basin had changed greatly.By using STL decomposition method,seasonal Kendall test and structural change method,the trend change of monthly scale data of each element and the regime shifts of hydrometeorological vegetation cover system were analyzed.It was found that during the period of 1957-1981,the hydrological and meteorological factors of the basin did not change greatly.Different from that,the precipitation,average temperature,potential evapotranspiration and average NDVI of the basin showed a significant upward trend from 1982 to 2010,while the runoff showed a significant downward trend.From 1957 to 1981,the change of elements in the hydrometeorological system was relatively consistent,which could be considered that the system was in a stable state.From 1982 to 2010,the change points of elements in the hydrometeorological vegetation cover system tended to disperse,and there was no stable corresponding relationship,and the endogenous relationship of the system was changing.(2)The groundwater storage change,actual evapotranspiration and underlying surface parameter of the watershed water heat coupled balance equation in the water cycle process were estimated by using digital filtering,RORA recession curve displacement method,watershed water balance formula and water heat coupled balance equation based on Budyko hypothesis.The results showed that before the 1990 s,groundwater storage change was almost all positive,that was,recharge was greater than discharge,while after the 1990 s,groundwater storage change was almost all negative,indicating that groundwater storage was gradually decreasing.The actual evapotranspiration showed a relatively weak downward trend under the condition of precipitation reduction in 1957-2010,which might be related to the impact effect caused by the increase of evapotranspiration caused by vegetation improvement.From 1957 to 2010,the underlying surface parameter of the watershed kept an upward trend,and tended to be obvious after 2000,and had a positive correlation with the average vegetation coverage.In the multiyear time scale,the correlation coefficient between them was as high as 0.85.Therefore,in the long-term scale,the larger the underlying surface parameter of the watershed should be related to the vegetation improvement of the watershed.(3)GAMLSS model was used to identify and diagnose the inconsistency features of hydrometeorological and surface environmental elements.The results showed that the mean square deviation(?)of annual precipitation was changed,the mean value(?)of annual potential evapotranspiration was changed,and the mean value(?)and mean square deviation(?)of annual groundwater storage change,annual actual evapotranspiration,annual underlying surface parameter and annual runoff were changed.The results of runoff inconsistency model showed that the inconsistency model with annual precipitation,annual actual evapotranspiration and annual underlying surface parameter as covariates,and the mean ? and mean square deviation ? changed with physical factors had better fitting effect on annual runoff than the inconsistency model with time as covariate,and the mean square deviation ? of annual runoff gradually decreased with time,which might be caused by the decreasing of the mean square deviation ? of annual precipitation with time,and the mean value ? and mean square deviation ? of annual runoff decreased with time,which might be related to the fact that the mean value ? and mean square deviation ? of annual evapotranspiration increased with time,the mean value ? and mean square deviation ? of annual underlying surface parameter increased with time.(4)Based on the recognition of the driving relationship between the driving factors and the driving relationship between the driving factors and runoff,using GAMLSS model,control variable method and watershed water balance formula,an inconsistency model with physical factors as covariates was constructed to quantitatively analyze the change of driving factors and the influence process of driving factors on runoff change,and the evolution law of runoffdriving factors system under different scenarios was discussed.The results showed that after2000,the contribution of the actual evapotranspiration and the underlying surface parameter to the groundwater storage change had increased,and the groundwater storage change gradually became negative.At the same time,the contribution of the underlying surface parameter to the actual evapotranspiration also increased,which led to the increasing of the actual evapotranspiration.For runoff,the change of precipitation and groundwater storage change had positive contribution to runoff change,while the actual evapotranspiration change had negative contribution to runoff change.After 2000,the contribution of the change of actual evapotranspiration and groundwater storage change to runoff change was greater,resulting in the gradual decrease of runoff.The results of quantitative analysis showed that the runoff increased by 1.23 mm when the precipitation increased by 10% compared with the multi-year average.When the underlying surface parameter increased by 10% compared with the multi-year average,the runoff decreased by 11.77 mm.When the precipitation and underlying surface parameter increased by10%,the runoff decreased by 11.76 mm.It can be seen that after the complex changes and interactions of driving factors,the impact mechanism on runoff is more complex,which may produce complex hydrological effects.Therefore,more in-depth research and exploration are urgently needed. |
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