4.2.2 Soil water changes in the sub–basins
The simulation results of soil water in the Qinhe River Basin exhibited
decreasing trends for the two change periods, which can be primarily
attributed to the continuous decrease in precipitation. However, the
ratio of soil water to precipitation has shown a continuous upward
trend. Specifically, the S/P (Soil Water/Precipitation) of the entire
basin increased from 0.22 to 0.24, and the S/P average of the sub-basins
where the reservoir is located increased from 0.22 to 0.25. These
findings indicate that the water conservation capacity of the entire
basin has improved, and the water conservation capacity of the
sub-basins where the reservoir is located is better.
Interestingly, in the last 30 years of the 20th century, despite the
continuous reduction in precipitation, the change in soil water was
relatively small, mainly due to the improved vegetation in the basin,
which is associated with water and soil conservation measures. The
utilization of soil water by plants promotes stability. However, this
also demonstrates that the vegetation-carrying capacity of the basin
reached a stable state in the 21st century.
Overall, these results reveal that the implementation of water and soil
conservation measures, including water conservancy projects, in the
Qinhe River Basin has positively impacted its ecology. The simulation
results of soil water in a typical sub-basin hosting a reservoir are
shown in Figure 6. The study highlights the importance of water and soil
conservation measures in the Qinhe River Basin and their positive impact
on its ecology. Specifically, the basin’s water conservation capacity
has improved, and its vegetation-carrying capacity has reached a stable
state in the 21st century. These findings underscore the significance of
sustainable water and soil management practices in maintaining the
health of river basins.