Multi-scale relationship between land use/land cover types and water quality in different pollution source areas in Fuxian Lake Basin

Abstract

The spatial-temporal evolution of land use and land cover (LULC) and its multi-scale impact on the water environment is becoming highly significant in the LULC research field. The current research results show that the more significant scale impact on LULC and water quality in the whole basin and the riparian buffer scale is unclear. A consensus has not been reached about the optimal spatial scale problem in the relationship between the LULC and water quality. The typical lake basin of the Fuxian Lake watershed was used as the research area and the scale relationship between the LULC and water quality was taken as the research object. High resolution remote sensing images, archival resources of surveying, mapping and geographic information, and the monitoring data of water quality were utilized as the main data sources. Remote sensing and Geometric Information Technology were applied. A multi-scale object random forest algorithm (MSORF) was used to raise the classification accuracy of the high resolution remote sensing images from 2005 to 2017 in the basin and the multi-scale relationship between the two was discussed using the Pearson correlation analysis method. From 2005 to 2017, the water quality indicators (Chemical Oxygen Demand (COD), Total Phosphorous (TP), Total Nitrogen (TN)) of nine rivers in the lake’s basin and the Fuxian Lake center were used as response variables and the LULC type in the basin was interpreted as the explanation variable. The stepwise selection method was used to establish a relationship model for the water quality of the water entering the lake and the significance of the LULC type was established at p < 0.05.The results show that in the seven spatial scales, including the whole watershed, sub-basin, and the riparian buffer zone (100 m, 300 m, 500 m, 700 m, and 1,000 m): (1) whether it is in the whole basin or buffer zone of different pollution source areas, impervious surface area (ISA), or other land and is positively correlated with the water quality and promotes it; (2) forestry and grass cover is another important factor and is negatively correlated with water quality; (3) cropping land is not a major factor explaining the decline in water quality; (4) the 300 m buffer zone of the river is the strongest spatial scale for the LULC type to affect the Chemical Oxygen Demand (COD). Reasonable planning for the proportion of land types in the riparian zone and control over the development of urban land in the river basin is necessary for the improvement of the urban river water quality. Some studies have found that the relationship between LULC and water quality in the 100 m buffer zone is more significant than the whole basin scale. While our study is consistent with the results of research conducted by relevant scholars in Aibi Lake in Xinjiang, and Erhai and Fuxian Lakes in Yunnan. Thus, it may be inferred that for the plateau lake basin, the 300 m riparian buffer is the strongest spatial scale for the LULC type to affect COD.

Assessment of the impact of land use in an agricultural catchment area on water quality of lowland rivers

“…A decrease in the area of arable land by 69% resulted in a 4-fold reduction of nutrient concentrations (Kowalik et al, 2015). Li et al (2019) found negative correlation between presence of forests and grasses in watershed and values of trophic parameters, total phosphorus and total nitrogen. Walsh & Wepener (2009) when analyzing water quality indexes in Southern Africa showed that in areas with intensive farming river waters fall into water quality classes ranging from poor to moderate.…”

Spatiotemporal Patterns of Impervious Surface Area and Water Quality Response in the Fuxian Lake Watershed

“…Province, Fuxian Lake is China's largest deepwater freshwater lake, the first large lake in the source of the Pearl River, and is the Nanpanjiang River system [22]. Its geographical location is 24°21′28″-24°38′00″N and 102°49′12″-102°57′26″E ( Figure 1).…”

“…e industry is dominated by phosphorus chemical industry, building materials, food processing, and aquatic products, of which phosphorus chemical industry is the pillar industry of this area. e land use type of Fuxian Lake Basin has always been dominated by forests and water areas [22]. However, with the improvement of the urbanization level of the basin, human activities have increased disturbance on the natural environment, such phenomena as reclamation of lakes, deforestation, overexploitation of tourism resources, and the rapid increase of functional buildings result in significant change in land coverage types in Fuxian Lake Basin.…”

“…Favored by experts and scholars at home and abroad, it has become one of the hot spots of the research on international lakes, and it is also one of the plateau lake basin systems with the research value of the most ecological fragile areas in geosciences of China. However, with the global changes intensified, the level of urbanization increased and the social and economic development accelerated in the basin, the lake body of Fuxian Lake has shrunk, the water level has decreased significantly, and the water area has gradually narrowed in recent years [22]. e land use/land cover changes in the basin are significant, soil erosion and land degradation are serious, and the ecological environment quality of the basin is generally declining [23][24][25].…”

Correlation Studies between Land Cover Change and Baidu Index: A Case Study of Hubei Province

“…Yang Yuejuan et al, explored the impact of land cover change on the ecological functions of agricultural and pastoral areas in the North [22]. Li Shihu studied the relationship between land cover types and water pollution in the lake basin of Fuxian County under a multi-scale relationship [23]. Li Fei et al, studied the relationship between surface vegetation and heat islands in Hangzhou, China, from 2000 to 2015 [24].…”