XVIII IWRA World Water Congress Beijing China 2023
Sub-theme 1: Water-Human-Economy(Agriculture, Industry, City...) - Ecology Nexus under a Changing Environment
Author(s): Miss. Yanjia Jiang, Sichuan University
Main author: Miss. Yanjia Jiang, Sichuan University ; Co-authors:
Miss. Yaling Zhang, Sichuan University
Prof. Li Guo, Sichuan University
Keyword(s): Preferential flow, Micro-topography, Soil moisture, hot spots and hot moments
Oral: PDFAbstract1-1. Rules and mechanisms of natural hydrological cycling and socio-economic water cycling evolution under climate change
The dynamics and controls associated with soil moisture spatial organization are crucial to modeling water flux and land–atmosphere interactions across landscapes in the context of climate change. However, the influence of fast soil moisture variations in response to precipitation on the temporal stability of soil moisture spatial organization (TSSS) and the temporal instability (i.e., the hot spots where high temporal variation rates occur) and hot moments (i.e., the hot times when high temporal variation rates occur) have not been sufficiently explored. To address these issues, this study monitored daily soil moisture at multiple depths (5–162 cm) for three consecutive years at 33 sites across a 7.9 ha forested headwater catchment. The standard deviation of the relative difference in soil moisture between a given monitoring location and the catchment mean (i.e., SDRD, a measure of TSSS) was used to quantify the influence of controlling factors (e.g., soil wetness condition, and preferential flow) on TSSS over the wet and dry seasons, respectively. The soil moisture variation index (i.e., SMVI, a measure of hot spots and hot moments) was used to quantify the effect of controlling factors (e.g., the soil moisture temporal variation and soil-terrain attributes) on hot spots and hot moments following a period of precipitation. The results showed the following: (1) Multiple linear regression analysis demonstrated that the correspondence between soil–terrain attributes and TSSS was stronger in the dry seasons than wet seasons (R2 of 0.597 vs. 0.301, P < 0.05). (2) TSSS was significantly correlated with preferential flow frequency (r = 0.611, P < 0.05) across sites, and adding preferential flow frequency as a regression variable considerably improved TSSS prediction. (3) Redundancy analysis revealed soil thickness and topographic wetness index were the main significant factors in causing hot spots during wet seasons, respectively rock fragments content during dry seasons. (4) The heterogeneity of soil moisture decline motivated the hot moments over the catchment throughout the year. These findings confirm the role of fast soil moisture variations in response to precipitation in regulating TSSS in complex terrain.