濂水流域降雨变化和景观格局演变的径流效应

降雨和景观格局是影响流域径流过程的两大主要因素,开展二者的径流效应研究对流域水资源管理、生态建设等具有重要意义。本研究以赣南红壤丘陵区的濂水流域为对象,基于1958—2020年的降雨、径流和土地利用数据,分析降雨、景观格局和径流的变化特征,以及降雨、景观格局与年径流、洪枯径流的关系。结果表明: 研究期间,流域年降雨量、年径流量、年最大1 d径流量均呈非显著下降趋势,年最小1 d径流量呈非显著上升趋势且年际变化幅度最大;有林地为流域内占比最高的景观类型,其他林地的变化最剧烈;景观水平上,流域的Shannon多样性指数、Shannon均匀度指数、斑块密度、景观形状指数分别由1980年的1.125、0.541、0.667、16.925上升至2020年的1.348、0.614、0.731、18.172,景观蔓延度指数由1980年的68.237下降至2020年的64.293,流域整体景观多样性、破碎化程度、形状复杂程度提高,空间分布趋于均匀,连通性降低。降雨量与年径流、洪水径流、枯水径流的相关系数分别为0.907、0.594、0.558;类型水平上,耕地减少对年径流、洪枯径流的影响均较大,而景观水平上的整体变化促进了年径流和洪水径流减少、枯水径流增加。降雨变化和景观格局演变对年径流、洪水径流和枯水径流变化的贡献率分别为17.8%、82.2%,1.5%、98.5%和-8.8%、108.8%。研究成果可为流域景观格局配置、水土流失综合治理等提供理论参考。

Runoff effect of precipitation variation and landscape pattern evolution in Lianshui watershed,Jiangxi, China

Precipitation and landscape pattern are two main factors affecting runoff process of the watershed. Understanding their runoff effect is of great significance to water resources management and ecological construction of watershed. Based on the data of precipitation, runoff, and land use from 1958 to 2020, we analyzed the characteristics of precipitation, landscape pattern and runoff in Lianshui watershed in red soil hilly area of southern Jiangxi Pro-vince, established the relationship between precipitation, landscape pattern and annual runoff, flood runoff, low runoff, respectively. The results showed that the annual precipitation, runoff and annual maximum one-day runoff in the watershed showed a non-significant downward trend during the study period, while the annual minimum one-day runoff showed a non-significant upward trend but with the largest inter-annual variation range. Forested land was the landscape type with the highest proportion in watershed, and other woodland had the most dramatic variation. At the landscape level, Shannon diversity index, Shannon evenness index, patch density and landscape shape index increased from 1.125, 0.541, 0.667 and 16.925 in 1980 to 1.348, 0.614, 0.731 and 18.172 in 2020, respectively, while the landscape contagion index decreased from 68.237 in 1980 to 64.293 in 2020. The overall landscape diversity, fragmentation degree and shape complexity of the watershed increased, the spatial distribution tended to be uniform, and the connectivity decreased. The correlation coefficients between precipitation and annual runoff, flood runoff, low runoff were 0.907, 0.594 and 0.558, respectively. At the class level, the reduction of cultivated land had a greater impact on annual runoff, flood runoff, and low runoff, while the overall change at the landscape level promoted a decrease in annual runoff and flood runoff and an increase in low runoff. The contribution rate of precipitation variation and landscape pattern evolution to the change of annual runoff, flood runoff ,and low runoff were 17.8%, 82.2% and 1.5%, 98.5% and -8.8%, 108.8%, respectively. Our results could provide theoretical refe-rence for landscape pattern allocation and comprehensive management of soil and water loss.