RESUMEN
To explore the relationship between land use and water quality in basins with different land use patterns at different spatial and temporal scales, the Wuding River Basin and Yanhe River Basin were taken as research objects. Based on land use data in 2020 and water quality monitoring data during two periods, the redundancy analysis method was adopted to quantitatively explore the impact of land use on water quality at multiple scales. The results showed thatï¼ â The main land use types in the two basins were cultivated land and grassland, and the difference was mainly in the proportion of bare land and forest land. â¡ The water quality in spring was better than that in autumn, and the water quality in the middle and lower reaches was worse. ⢠The interpretation rate of land use on the riparian scale was the highest in the two basins. ⣠The effect of land use on water quality was more significant in the Wuding River Basin in autumn than in spring, whereas the Yanhe River Basin showed the opposite trend. ⤠Different land uses had different impacts on water quality. Bare land, cultivated land, and Shannon diversity index ï¼SHDIï¼ in the Wuding River Basin had significant impacts on water quality, whereas grassland, cultivated land, artificial surface, patch density ï¼PDï¼, and SHDI were significant in the Yanhe River Basin. Cultivated land and artificial surfaces in the Wuding River Basin had a negative impact on water quality. Grassland and bare land had a negative correlation with most chemical indicators. Artificial surfaces and grasslands in the Yanhe River Basin had a negative impact on water quality, whereas forest land had a significant purification effect. The research results provide important information for sustainable land use and multi-scale landscape planning, which can be used to improve water quality.
RESUMEN
Yanhe River Basin is located in the hilly gully area of the Loess Plateau with serious soil erosion. Strong human activities in the middle and lower reaches lead to fragile ecological environment. Soil erosion status varies among different geomorphic units within the watershed (loess liang hilly and gully region, loess mao hilly and gully region, and broken platform region). In this study, we surveyed the benthic community from the Yanhe River Basin in April (spring) and October (autumn) of 2021. To evaluate the water ecological health status of the watershed and investigate the effects of different geomorphic units on the benthic integrity of the benthos, we constructed the benthic-index of biotical integrity (B-IBI) based on the biological data. We identified a total of 113 species of 73 genera in 4 phyla of benthic fauna, with aquatic insects as the dominant taxa in both seasons. Through screening 26 candidate indicators, we found that the spring B-IBI consisted of three indicators: relative abundance of individuals of dominant taxonomic units, family biotic index (FBI), and relative abundance of predator individuals, and that autumn B-IBI was composed of the number of taxonomic units of Ephemeroptera, FBI value, and the relative abundance of predator individuals. Results of the B-IBI evaluation showed that 83.3% of the sampling sites in the upper mainstem and tributaries were at a healthy condition, while only 28.6% sampling sites in the middle and lower mainstem and tributaries were at a healthy condition. In addition, the health status of the watershed was better in spring than in autumn. The Kruskal-Wallis nonparametric tests showed that benthic density, species number, and B-IBI percentile scores in the fragmented loess area were significantly higher in spring than in autumn, and significantly lower in autumn than in the loess liang hilly and gully region and loess mao hilly and gully region, being mainly caused by the increasing erosion due to the concentrated rainfall in wet season. Results of the redundancy analysis showed that key environmental factors affecting benthic community structure in spring were boulder substrate, chlorophyll-a, oxidation reduction potential, turbidity, conductivity, and dissolved oxygen, and were nitrate-nitrogen, oxidation reduction potential, and pH in autumn.
