| Abstract: | Under the Grain for Green Project in China, vegetation
recovery construction has been widely implemented on
the Loess Plateau for the purpose of soil and water conservation.
Now it is becoming controversial whether the recovery
construction involving vegetation, particularly forest, is reducing
the streamflow in the rivers of the Yellow River basin.
In this study, we chose the Wei River, the largest branch of
the Yellow River, with revegetated construction area as the
study area. To do that, we apply the widely used Soil and Water
Assessment Tool (SWAT) model for the upper and middle
reaches of the Wei River basin. The SWAT model was
forced with daily observed meteorological forcings (1960–
2009) calibrated against daily streamflow for 1960–1969,
validated for the period of 1970–1979, and used for analysis
for 1980–2009. To investigate the impact of LUCC (land use
and land cover change) on the streamflow, we firstly use two
observed land use maps from 1980 and 2005 that are based
on national land survey statistics merged with satellite observations.
We found that the mean streamflow generated by using
the 2005 land use map decreased in comparison with that
using the 1980 one, with the same meteorological forcings.
Of particular interest here is that the streamflow decreased on
agricultural land but increased in forest areas. More specifically,
the surface runoff, soil flow, and baseflow all decreased
on agricultural land, while the soil flow and baseflow of forest
areas increased. To investigate that, we then designed five
scenarios: (S1) the present land use (1980) and (S2) 10 %,
(S3) 20 %, (S4) 40 %, and (S5) 100%of agricultural land that
was converted into mixed forest. We found that the streamflow
consistently increased with agricultural land converted
into forest by about 7.4mm per 10 %. Our modeling results
suggest that forest recovery construction has a positive impact
on both soil flow and baseflow by compensating for reduced
surface runoff, which leads to a slight increase in the
streamflow in the Wei River with the mixed landscapes on
the Loess Plateau that include earth–rock mountain area. |