where Q is the increasing quantity of water storage from different ecosystems such as forest or grass ecosystem by the comparison with bare land, A is the area of ecosystem, J is the annual rainfall
runoff (P> 20 mm) of average years in the study area,J0 is the annual total rainfall of average years in the study area, K is the proportion of rainfall runoff on total rainfall,R0 is the effectiveness coefficient of bare land reducing runoff. Rg is the effectiveness coefficient of other ecosystems reducing runoff. In this study, the values of K and R refer to the relevant studies (Zhao et al., 2004).
Using Formula(1) and after standardization, we calculated the importance index of water
storage for each spatial unit using the module of spatial analysis in
software ArcGIS9.3. And then using the standard deviation (1 SD)
classification, the importance index of water storage is to divide into
four rankings (extremely important, moderately important, generally important, and not important).
We used a disjunction function to calculate the ecological
importance index of the space maintaining water security (EIIw) for
each grid, where the four indexes represent four aspects of maintaining regional water security.
The equation is as follows:
where Q is the increasing quantity of water storage from different ecosystems such as forest or grass ecosystem by the comparison with bare land, A is the area of ecosystem, J is the annual rainfall
runoff (P> 20 mm) of average years in the study area,J0 is the annual total rainfall of average years in the study area, K is the proportion of rainfall runoff on total rainfall,R0 is the effectiveness coefficient of bare land reducing runoff. Rg is the effectiveness coefficient of other ecosystems reducing runoff. In this study, the values of K and R refer to the relevant studies (Zhao et al., 2004).
Using Formula(1) and after standardization, we calculated the importance index of water
storage for each spatial unit using the module of spatial analysis in
software ArcGIS9.3. And then using the standard deviation (1 SD)
classification, the importance index of water storage is to divide into
four rankings (extremely important, moderately important, generally important, and not important).
We used a disjunction function to calculate the ecological
importance index of the space maintaining water security (EIIw) for
each grid, where the four indexes represent four aspects of maintaining regional water security.
The equation is as follows:
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