极端天气下三峡库区土地利用对河流水质的多时空尺度影响

为探究极端天气下流域内水质对土地利用的响应关系,本研究基于不同空间尺度(1000 m河段缓冲区、500 m河岸带缓冲区及子流域)的土地利用指数以及旱季(2019年11月)、雨季-洪水期(2020年7月)和雨季-干旱期(2022年8月)的水质数据,探究流域内土地利用对水质的多时空尺度影响,从而得到保护流域水质和规划流域内土地利用格局的最佳时空尺度和对水质影响最显著的预测因子。研究表明:(1)流域水质受极端天气影响,降雨会增强水体的稀释能力,高温会加快水中微生物反应速率,具体表现为雨季-洪水期的水质较好,雨季-干旱期次之,旱季较差。(2)土地利用对水质指标的影响存在时空尺度效应,土地利用在子流域和旱季尺度下对河流水质影响最显著。(3)不同土地利用指数对流域水质影响存在差异,耕地、林地、斑块密度、最大斑块指数和边缘密度是影响水质指标最显著的解释变量。其中林地与多数水质指标具有负相关关系,建设用地、耕地、斑块密度与较多水质指标存在正相关关系。本研究结果为合理规划土地利用格局以及保护河流水质提供科学依据,对三峡库区环境可持续发展及生态保护具有一定意义。

Effects of land use on river water quality at multiple spatial and temporal scales in the Three Gorges Reservoir area under extreme weather conditions

To explore the cause-effect relationship between river water quality and land use in the basin under extreme weather, this study collected several datasets including land use indexes at multiple spatial scales (1000 m river buffer zone, 500 m riparian buffer zone and sub-basin), water quality data in dry season (November 2019), rainy season-flood season (July 2020) and rainy season-arid season (August 2022). Based on the collected datasets, we explored the effects of land use at multiple spatio-temporal scales on river water quality in the basin, and thus determined the best spatial and temporal scale for protecting water quality and planning land use pattern in the basin and the critical predictors of water quality. Our results showed that the river water quality of the basin was affected by extreme weather. Rainfall would enhance the dilution capacity of the water body. High temperature would accelerate the microorganism reaction rate in the water. The water quality is better in the rainy season-flood season, followed by the rainy season-arid season. The water quality in the dry season is poor. The impact of land use on water quality was affected by both spatial and temporal scales. Land use had the most significant impact on river water quality at the scales of sub-watershed and dry season. Cultivated land, forest land, patch density, largest patch index and edge density were the most significant explanatory variables affecting river water quality. Among them, forest land had a negative correlation with most water quality indicators, while construction land, cultivated land and patch density had a positive correlation with some of the water quality indicators. The results of this study provided a scientific basis for managing land use pattern and protecting river water quality, and was thus important for the sustainable development of human living environment and ecological protection.