水保所知识产出(1956---)知识库

Accurate estimation of groundwater recharge in regions with limited water and thick unsaturated zones is
challenging because of the limited water flux. This study aims to employ multiple tracers and methods to
investigate the mechanism of groundwater recharge in the thick loess deposits of China. We collected soil
samples under different vegetation, unconfined groundwater, and precipitation to determine the water isotopes
(δ 2 H, δ 18 O, and 3 H), chloride (Cl - ), nitrate (NO 3 – ). Then, these tracers were employed to estimate recharge rates
with methods considering the differences in shallow- and deep-rooted vegetation, as well as those in unsaturated
and saturated zones. Results indicated that local precipitation predominantly recharges groundwater through
matrix flow at a velocity of 14.5 cm year −1 with the residence time of > 200 years. The recharge rates range from
0 to 37 mm year −1 , equivalent to 0–7% of annual average precipitation. However, the deep-rooted vegetation
greatly reduced deep drainage compared with shallow-rooted vegetation, which will perturb the current hy-
draulic connectivity between unsaturated and saturated zones. The multiple tracers and methods can comple-
ment each other to enhance the understanding of groundwater recharge mechanisms. The indicated relationship
between recharge form and land use suggests the urgency in developing strategies to balance the agroforestry
system and water resource sustainability.