Undervalued Groundwater Resources Over the Major Tectonic Lines of Southeastern China

Rising water demand for agricultural, industrial, and domestic sectors continue to stress water resources worldwide. In southeastern China, coastal cities and megacities typically rely on thousands of reservoirs, incurring high construction and maintenance costs. However, rural areas in this region, underlain by shallow, low-permeability bedrock due to regional metamorphism, host exploitable groundwater resources along major tectonic fault lines. To understand groundwater dynamics in these fractured aquifers, this study investigates a local site in Longquan (Zhejiang Province, China). Field investigations informed a three-dimensional geological model, which provided the basis for numerical flow modeling analysis using the USGS-MODFLOW code. Results indicate that permeable damage zones along the tectonic fault lines are recharged by a weathered bedrock blanket layer and are laterally bounded by low-permeability bedrock, limiting the spatial extension of the aquifer. The sub-tropical climate and hydrostratigraphic conditions make groundwater exploitation feasible, despite the modest groundwater yield of the damage zones (2.2 × 105 m3 per km of damage zone). Intensified fracturing also produces recognizable morphological changes, transitioning from steep, incised valleys to rounded hills with flatter streambeds. This distinctive morphological feature was identified in 140 basins across southeastern China, suggesting the presence of strategic groundwater resources throughout this region. Harnessing these fracture-controlled groundwater resources may bolster economic growth in rural communities and help narrow the development gap with more urbanized coastal areas.