Revegetation Reduces Soil Moisture and Groundwater but Not Water Yield in Humid Karst Areas

Abstract

While vegetation restoration results in increased carbon storage and benefits ecosystems, its effects on water availability in ecologically fragile karst areas are unclear. Here, we investigate the long-term spatial-temporal variations of climate parameters, vegetation greenness, hydrological variables (evapotranspiration, runoff, soil moisture), water yield, and terrestrial water storage in the Southwest China Karst (1982–2018), where large-scale ecological restoration projects (ERPs) were implemented in the past few decades. The generalized linear mixed model (GLMM) was employed to quantify the contributions of climate change and vegetation greening on the changes in water availability in this humid region. We found that vegetation greening in the Southwest China Karst was significant during 1982–2018. Climate change resulted in a remarkable change from a wetting trend to a drying trend during 1993–2013. We show that the vegetation-greening and climate change across this humid region strongly increased the evapotranspiration (ET, +2.08–2.67 mm yr⁻¹) and reduced the terrestrial water storage (TWS, −2.19–2.96 mm yr⁻¹) over the past almost four decades, while the water yield was almost unchanged. Vegetation greening accounted for a ∼26.43%–52.09% decrease in TWS, and we attribute this water depletion to decreases in soil moisture and groundwater during dry years (1993–2013). These findings show that future “green projects” in humid karst areas should consider the impact of revegetation on the sustainable water supply.