Landscape index for indicating water quality and application to master plan of regional lake cluster restoration

Abstract

Understanding the relation between landscape pattern and water quality is essential to making a master plan for restoration of regional lake and wetland clusters, which has not yet been well resolved. Here, we studied the impacts of landscape pattern changes on water quality over lake clusters, taking the aquaculture area in the Lixia River hinterland of China as a case. Multi-temporal Landsat series of remote sensing data from 1985 to 2018 was used and space-for-time substitution (SFTS) method was applied to explore the relationship between landscape pattern and water quality. Results showed that wetland and free water surface were the dominant classes of the lake cluster in 1985 and 1990, but they began to rapidly decrease from 1995 to 2000. The enclosure aquaculture increased rapidly since 1995 and became the dominant class between 1995 and 2018. The patch density of aquaculture water (PD_A) increased from 0.09n/km2 in 1985 to 0.34n/km2 in 2018, with the largest degree of fragmentation in 2000. However, the growth rate of PD_A declined significantly after the enactment of the lake ecological protection policies. The SFTS results showed that PD_A had positive correlation with total nitrogen (TN) (r = 0.26), ammonia nitrogen (NH3-N) (r = 0.21), and Chlorophyta (r = 0.33), and the water quality degraded with increasing PD_A. Hence, PD_A could be a water quality indicator of lakes in the Lixia River hinterland. The study is expected to provide a viable method to design regional restoration plan for degraded and over-developed wetland areas.

Keywords

• Lake cluster
• Enclosure aquaculture
• Landscape pattern changes
• Water quality