Figure 8. Variations of thermal properties with saturation. The range of porosity in this study is 0.375–0.482.
  1. Effects of coupling depth on the subsurface buffer
In Figure 9, samples are the daily ΔGST at each grid-cell in the whole modeling area for a pumping year, so the total number of samples is 613,565 (41×41×365). 1000 bins are used to obtain the number of samples (frequency) in each bin, and then the histogram was plotted with a semilog vertical coordinate. Only 6 years of pumping were plotted for easy observation. With the increase of coupling depth, it is evident to see that the increase/decrease of GST (pumping relative to no pumping), particularly the increase, becomes smaller after a same pumping period (Figure 9). For example, the maximum increase of GST after 1 (6) years of pumping is more than 4 (6) K for L4 while less than 1 (4) K for L14. The nonlinearity of ΔGST with time becomes mild with the increasing coupling depth. For instance, in Figure 9a, the increase of GST is significant in the first year while rapidly attenuated in the following years. In contrast, in Figures 9f, the increase of GST is much more uniform with time. The decrease of amplitude and nonlinearity of ΔGST with the increase of coupling depth can also be observed in Figure 5a. This indicates a more robust subsurface buffer with deeper coupling depth, which has more effective regulations on the GST.