[Spatial Response of River Water Quality to Watershed Land Use Type and Pattern Under Different Rainfall Intensities]

Qixiang River watershed, as a typical case study area, was divided into five types of buffer zones according to elevation and slope. Based on the remote sensing images, DEM and real-time monitoring data in April, May, June 2015, the relationship between land use type and pattern in all buffer zones and water quality under different rainfall intensities was explored. The results showed that land use type and pattern in different buffer zones had obvious discrepancies. The proportion of construction land was the highest in low flat area, secondary flat area and high flat area. The main land use type of moderately steep area and high steep area was forest land. Secondly, the low flat area appeared to have the greatest influence on the water quality. Thirdly, construction land had a greater influence on water quality than other land use types in low flat area. In addition, in secondary flat area, wetland was the key factor under small rainfall intensity. However, construction land was the key factor under moderate rainfall intensity and large rainfall intensity. In moderately steep area and high buffer zones, construction land influenced the water quality most under small rainfall intensity but forest land was the greatest factor under moderate rainfall intensity and large rainfall intensity. Fourthly, the relationship between the land use pattern and water quality was complicated. SH-MN had the greatest influence on water quality and the influence increased with increasing rainfall intensity in low flat area. Furthermore, PD, SH-MN and SHDI were the key factors in secondary flat area while SH-MN, SHDI and PD were the key factors in high flat area under all the three types of rainfall intensity. SH-MN and CONTAG influenced the water quality most in moderately steep area and high steep area under small and high rainfall intensity. CONTAG influenced the water quality most in moderately steep area and SHDI was the key factor in high steep area under moderate rainfall intensity.