Sharp decline and sluggish rise of shallow groundwater level in the Central Hebei piedmont agricultural region

In response to the constant decline of shallow groundwater level in the Central Hebei piedmont agricultural region, this paper monitored the hour-scale dynamic variation data of water levels and analyzed the difference of groundwater level changes during irrigation and non-irrigation periods by employing time-series variation feature and trend analysis method. Results indicate that the shallow groundwater level declines by more than 1.0 cm/d during irrigation period and rises by less than 1.0 cm/d during non-irrigation period, which is closely correlated with precipitation amount and distribution as well as agricultural exploitation intensity. For irrigation periods with low precipitation, the declining lines and rising lines are below the local average annual water level variation line, while for irrigation periods with abundant precipitation, they are above the local average annual water level variation line. Large-scale intense agricultural exploitation has led to the water level decline by the scale of cm/d, while the water level rise with the scale of mm/d is attributed to the local thick unsaturated zone(thicker than 15m).