Spatiotemporal variability of shallow groundwater depth in intensive agricultural areas

Revealing the spatiotemporal variation characteristics of shallow groundwater depth (GWD) can provide scientific basis for evaluating and managing groundwater resources. The data for groundwater depth in 1990 and 1999 at Quzhou County, Hebei province were measured in situ and obtained from history data. Descriptive statistics and geostatistics were used to analyze the data. The results indicated that average groundwater depth in 1990 and 1999 were 4.64 m and 9.81 m, respectively. The semi-variation analysis showed that their spatial correlation distances in 1990 and 1999 were 13.6 km and 10.4 km, respectively, which showed a descending trend. The increasing trend of GWD from north to south across the county was caused by the change of topography and land use types in this region. During the past 10 years, the area where GWD was higher than 9.81 m increased from 0 to 323.99 km2, while the area where GWD was lower than 4.64 m decreased from 281.8 km2 to 15.33 km2. The main factors affecting GWD descending trend were land use change and overdraw of groundwater by farmers in this area.