The Response Relationship between Land Use/Land Cover and Watershed Lagged Effect based on Different Time Scales--A Case Study in Central Guizhou of China*

: As we all know, the drought occurrence indicates that there is no rainfall or little rainfall in a certain period. However, 10 the no or little rainfall does not mean that the droughts must be occur, and the occurrence of droughts shows a certain lag in the 11 different areas. This paper analyzes the characteristics of watershed lagged effects and human activities in Central Guizhou of China 12 (CGC) by the Lagged Index ( LI ) and Landscape Index ( LI ) based on the land use data, rainfall and runoff data during the periods of 13 1971-2016.The results show that ① the influence difference of the same land use type on the lagged intensity was particularly 14 significant （ P <0.001 ） in the different ages (1970s-2010s). Among them, it gradually increased for the impacts of the wood land, grass 15 land and cultivated land on the lagged intensity with the increasing of ages, and reached the maximum in the 2000s, and reached the 16 maximum in the 2000s, while it did not change significantly for the water land and construction land. ② The impact of land use type 17 transfer on watershed lagged effects is particularly significant ( P <0.001).Among them, it gradually increases for the wood land 18 transfer with the prolongation of lagged periods, and reaches the maximum for the construction land transfer in the lag-1 period ( X t-1 ), 19 and is not significant for the rest type transfer. ③ The impact differences of the principal components ( Zs ) on watershed lagged effects 20 are particularly significant for the morphological characteristics of land use types in different lagged periods ( X t-0 - X t-3 ), and different 21 ages (1970s-2010s),


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As we all know, the drought occurrence indicates that there is no rainfall or very little rainfall in a certain period, 30 while it does not mean that the drought must be occur without rainfall or little rainfall in some periods. There is a 31 certain lag for the occurrence of droughts in different regions, and its lag time and intensity are greatly affected by 32 watershed water-stored capacity. Therefore, the drought is more influence by the watershed water storage (soil, aquifer, 33 lake, river) whether than by the rainfall deficit. It means that drought may occur in high flow seasons (van Loon, 2013).

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Meanwhile, the lagged effect of hydrological drought on meteorological drought has particularly significant differences 72 in the different basins, and the climate and land use/land cover are the main factors affecting the propagation process 73 from the meteorological to hydrological drought(Zhao et al., 2019; Zhou et al., 2019). The response of vegetation to 74 rainfall varies with the changing of soil types. It is found that there is a linear relationship between the NDVI and 75 rainfall when the rainfall is lower than the saturation threshold. However, the NDVI value increases slightly only with 76 additional rainfall when the rainfall exceeds the threshold (Nicholson et al.,1994;Niu et al., (2018). 77 Therefore, this paper will firstly judge the lagged response of runoff to rainfall by the distribution-lagged summer, accounting for about 80% of the annual precipitation. The study area is located in the wide and gentle slope 93 zone that is the Karst Hilly Landform of Yunnan-Guizhou Plateau, and the Second Step of Eastern Slope and Dividing Yangtze River Basin. It mainly includes the main stream of Sancha River and its tributaries, Baiyan River, Laolongqiao 96 River, Boyu River, Chengguan River, Maotiao River and Nanming River, etc. The south of the ridge line belongs to the 97 Beipanjiang and Hongshui river water systems in the Pearl River Basin. It mainly includes the Wanger River and Baling 98 River of Beipan River tributaries, and the Maoying River and Getu River of the Hongshui River tributaries, etc.

Land use/land cover data 118
The land use/land cover changes were represented by the land use data of 1975,1985,1995,2005 and 2015 in this 119 paper, which was mainly come from the resource and environmental science and data center(http://www.resdc.cn) 120 (Resource and Environment Science and Data Center, China) (Fig.2)

Lagging index 129
Firstly, we analyzed and judged the lagged effect using the cross y, x of Eviews 9.0. It was judged that the lagged 130 effect of runoff on rainfall in Karst drainage basins is overall shown as three periods (lag months 3).

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Secondly, the PDL of Eviews 9.0 was used to build the distribution-lagged regression model, namely, 132 LS y  PDL(x, k, m, d)

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The distribution-lagged regression model was calculated as follows: Where t y represents the runoff volume at the t-th time, represents the lagged-flow volume at the s-th reference period, i-th lagged period. 145 i V , i S represent the mean value and standard deviation of lagged-flow volume at the i-th lagged period, respectively.

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LI is positive, indicating normal (i.e., no lagged effect). LI is negative, and the larger the absolute value, the more       However, it is just the opposite of influences on lagged frequency (Fig.10). (2)The impact difference of different Zs on 295 lagged effect is particularly significant(P<0.001)for the morphological characteristics of single land use type in 296 different lagged periods (Xt-0-Xt-3), different ages (1970s-2010s) and different time scales (1-12 months). Among them, the F value of the largest impact on lagged intensity/frequency is found in the grass land in the Xt-0-Xt-3, followed by the 298 water land and wood land, and the smallest in the cultivated land and construction land. And that of the impact on 299 lagged intensity/frequency is more larger in construction land than in cultivated land and woodland in the 1970s-2010s, 300 and the smallest in the water land and grass land (Fig.9). The F value of the impacts on the lagged intensity/frequency is 301 the grass land>water land and cultivated land>wood land and construction land in the 1-12 month scales (Fig.10).

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Meanwhile, the influence differences of the Zs on lagged intensity/frequency are also significant(P<0.001)in the 303 Xt-3,1970s-2010s and 1-12 month scales, respectively (Figs.8,9,10). (3) For the Zs of morphological characteristics 304 of single land use type in the Xt-0-Xt-3, the R absolute value of the impacts on lagged intensity is the grass land and water 305 land (lag-2 period)>cultivated land (lag-2 period) and wood land (lag-1 period)>construction land (lag-2 period). The R 306 absolute value of the impacts on lagged frequency gradually increases for the Zs of grass land, water land, wood land 307 and construction land with the prolongation of lagged periods, and reaches the maximum in the lag-3 period (Xt-3).And 308 it is the largest for the cultivated land in the lag-2 period (Xt-2) (Fig.8). The R absolute value of the Zs impacts on the 309 lagged intensity was the largest for the grass land in the 1970s-2010s, and gradually decreased for the cultivated land, 310 water land and wood land with the increase of years (ages). And that of the Zs impacts on the lagged frequency was the 311 largest for the cultivated land and grass land with the maximum in the 1980s,and gradually declined for the wood land 312 and water land with the increase of years (ages),and varied little for the construction land (Fig.9). The R absolute value 313 of the influences on lagged intensity is to increase for the Zs of land use types in the 1-12 month scales. Among them, it 314 is the largest for the grass land and water land, and reaches the maximum in the 9-month scale, followed by the wood 315 land (the maximum in the 9-month scale) and cultivated land (the maximum in the 6-month scale),and the smallest for   effect result of human activities on the watershed media. The spatial pattern of land use types is determined by the type, 340 quantity, shape, spatial distribution and combination of land use/land cover, and the patch is the basic component unit of 341 spatial pattern of land use/land cover (Liu, et al.,20012 & 2002). The patches of different land use types, such as the 342 cultivated land, woodland, grassland, construction land, etc., show the different graphic characteristics due to different 343 formation mechanisms, and the graphic characteristics are mainly shown the shape and spatial distribution of land 344 use/land cover patches. Human activities eventually lead to the changes of land use types, quantity and morphological 345 characteristics. This study prove that the land use and change all have an impacts on the watershed lagged effect, and 346 show the positive and negative differences. Human activities not only lead to the increasing or decreasing of land use 347 types, and the interconversion between the different land types, but also lead to the complexity of the boundary 348 distribution of land types, which will affect the integrity of watershed water-stored spaces, and further influence the 349 watershed lagged effect characteristics. Landscape index is the most effective quantitative index of the land types' 350 morphological characteristics. For example, the larger the patch density index is, the more concentrated and fragmented 351 the land type distribution is, on the contrary, the more scattered and continuous. The larger the largest patch index is, the 352 smaller the intensity and frequency of human activities are, which shows that the more concentrated the land type 353 distribution is, and the simpler the boundary condition is. Conversely, the larger the intensity of human activities, the 354 higher the frequency. It means that the more scattered the land type distribution is, and the more complex the boundary 355 condition is. The smaller the patch shape index is, the more complex the morphological characteristic of land types is, 356 on the contrary, the simpler it is. The larger the patch fractal dimension index is, the more complex the land use types is, 357 and the more circuitous the boundary distribution is. On the contrary, the simpler the land use type distribution is, the  The R absolute values of the Zs impacts on the lagged frequencies reached the maximum in the grass land and wood 384 land in the lag-1 period (Xt-1) and lag-2 period (Xt-2) with the prolongation of lagged periods, and the minimum in the cultivated land and water land in the lag-1 period (Xt-1) and lag-2 period (Xt-2), respectively.