22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Effects of water table depth on the hydrological process in the unsaturated zone

24 Sep 2019, 15:15
15m
Multiuse room 1 ()

Multiuse room 1

Oral Topic 5.3 - Advanced modelling tools for subsurface hydrology: from the vadose zone to deep environments Parallel

Speaker

Dr Siyuan Huo (College of Resources and Environment, Yangtze University)

Description

Water table depth is a critical factor affecting infiltration recharge and groundwater evaporation, both of which are key aspects of the hydrological process in the unsaturated zone. To evaluate the effect of water table depth on the hydrological process in the unsaturated zone, a lysimeter experiment incorporating a 1-year-long bromide tracer test was conducted to determine the unsaturated zone flow process under different water table conditions. The experimental results clearly indicated that water table depth determines the storage capacity of the unsaturated zone, thereby affecting the hydrological process in the unsaturated zone. The decline of the water table increased the maximum water deficit that consumed the infiltrated water and reduced the actual recharge quantity. Evaporation only affected the unsaturated zone above the extinction depth of evaporation (EDE), and consequently, groundwater evaporation tended to be extinct in association with the decline of the water table. The relative position of the water table and EDE changed the unsaturated zone flow. When the water table was above the EDE, downward and upward fluxes were dominated by infiltration recharge and groundwater evaporation, respectively, but would restrict each other, as demonstrated by the negative relationship between an irrigation event and groundwater evaporation. Soil water moved predominantly downward when the water table was below the EDE; a deep unsaturated zone entailed a long infiltration path, which smoothed the temporal variability of the recharge rate and increased the time lag in recharge. Groundwater evaporation caused the upward transport of bromide, which proved to be significant for the evaluation of evaporation quantity. The application of the bromide tracer method should meet certain prerequisites such as application of a rain shelter and appropriate injection depth. The bromide tracer was proved to be efficient for tracing the unsaturated zone flow and presents an innovative method for evaluating groundwater evaporation.

Primary author

Dr Siyuan Huo (College of Resources and Environment, Yangtze University)

Co-authors

Prof. Menggui Jin (School of Environmental Studies, China University of Geosciences) Prof. Xing Liang (School of Environmental Studies, China University of Geosciences) Ms Xiang Li (Petroleum Engineering Colloge, Yangtze University) Ms Hongbo Hao (College of Resources and Environment, Yangtze University)

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