水保所知识产出(1956---)知识库

Numerous studies have been conducted to understand the mechanism of groundwater recharge for water re-
sources management. But the roles of wide-spread village ponds on the Chinese Loess Plateau on groundwater
recharge remains uncertain. Here, to evaluate the groundwater recharge under village ponds, we measured
environmental tracers ( 2 H, 18 O, Cl - ) in rainwater, groundwater, and pore waters of the deep unsaturated zone
under three land-cover types (cropland, a village pond, and two apple orchards with stand ages of 10 and 27
years). The results show that shallow groundwater is recharged by both diffusive recharge and focused recharge.
Specifically, diffusive recharge occurs beneath farmlands, grasslands, orchards and similar land-cover types, but
diminishes in old orchards due to deep root water uptake. The diffusive recharge beneath crop field had an
infiltration velocity of 10.3–12.5 cm yr −1 ; the resulting recharge rate was 30–33 mm yr −1 , accounting for 5–6%
of the annual precipitation. However, focused recharge occurs mainly beneath village ponds with low-lying
terrain, and had an infiltration velocity of 26 cm d −1 during the rainy season; the resulting mean recharge
rate was 134 mm yr −1 in the catchment of the pond, accounting for 23.1% of the annual precipitation. Given that
the water table is generally more than 30 m below the soil surface, it takes hundreds of years for rainwater to
reach the water table via the diffusive recharge but only days to months via the focused recharge. Diffusive
recharge contributed 55–68% to the total recharge while focused recharge contributed 32–45%. However, the
conversion of croplands to apple orchards and the decrease in the number of village ponds are occurring, which
diminishes diffusive recharge, and reduces focused recharge, respectively. These findings are critical to under-
standing hydrological processes and protecting groundwater resources. We should preserve, reclaim, and
construct village ponds to ensure groundwater recharge, in addition to optimizing areal ratio of large farmland to
apple orchards in the region for the sustainable utilization of groundwater resources.