Detection of critical LUCC indices and sensitive watershed regions related to lake algal blooms: a case study of Taihu Lake.

Chen Lin,Ronghua Ma,Zhihu Su,Qing Zhu

doi:10.3390/ijerph120201629

Abstract

Taihu Lake in China has suffered from severe eutrophication over the past 20 years which is partly due to significant land use/cover change (LUCC). There is an increasing need to detect the critical watershed region that significantly affects lake water degradation, which has great significance for environmental protection. However, previous studies have obtained conflicting results because of non–uniform lake indicators and inadequate time periods. To identify the sensitive LUCC indices and buffer distance regions, three lake divisions (Meiliang Lake, Zhushan Lake and Western Coastal region) and their watershed region within the Taihu Lake basin were chosen as study sites, the algal area was used as a uniform lake quality indicator and modeled with LUCC indices over the whole time series. Results showed that wetland (WL) and landscape index such as Shannon diversity index (SHDI) appeared to be sensitive LUCC indices when the buffer distance was less than 5 km, while agricultural land (AL) and landscape fragmentation (Ci) gradually became sensitive indices as buffer distances increased to more than 5 km. For the relationship between LUCC and lake algal area, LUCC of the WC region seems to have no significant effect on lake water quality. Conversely, LUCC within ML and ZS region influenced algal area of corresponding lake divisions greatly, while the most sensitive regions were found in 3 km to 5 km, rather than the whole catchment. These results will be beneficial for the further understanding of the relationship between LUCC and lake water quality, and will provide a practical basis for the identification of critical regions for lake.

Highlights

Lake ecosystems supply essential goods and services to sustain ecosystems and the livelihoods of people living in their watersheds [1,2]
With respect to the complete study site reflecting 50 km buffer regions, agricultural land was dominant before 2000, while construction land was mainly present in the northeastern part of Zhu Shan Lake (ZS) region
In 2012, construction land and agricultural land covered most of the region; the proportions of these two types exceeded 75% in Mei Liang Lake (ML) (Table 1)

Summary

Introduction

Lake ecosystems supply essential goods and services to sustain ecosystems and the livelihoods of people living in their watersheds [1,2]. In spite of their critical importance, many lakes in China are approaching their limits in terms of ecological environmental quality and lake eutrophication as a result of land use/cover change (LUCC) [3]. By way of non-point source pollution, results from conversion of land uses from native cover to agriculture and urban uses [8]. The original forestland, arable land and urban land have been identified as the land uses most sensitive to lake quality changes

Objectives

Methods

Results

Discussion

Conclusion