Spatial and temporal distribution of groundwater depth and soil moisture in marsh wetland across the Heihe Wetland Nature Reserve

The wetland groundwater depth and soil moisture in the study area were monitored from 2015 to 2017 in order to accurately understand the hydrological processes in marsh wetlands across Heihe Wetland Nature Reserve. The cluster analysis showed that the 12 fixed observation points in the study area were divided into three regions according to the depth of groundwater burial (deep, medium, and shallow). The results indicated that the groundwater burial depth in the different areas varied considerably in space, and the seasonal variation was greater in summer and the fall, but less in winter and spring, The annual average groundwater depth in 2016 (42.28 cm) > 2017 (38.88 cm) > 2015 (34.33 cm). The interannual variation was not significant (P > 0.05). The soil water content in the different regions also showed large spatial differences. The shallow groundwater region varied between the different soil layers. The annual average value for soil water content in 2015 (46.79%) > 2016 (45.36%) > 2017 (43.10%), but these differences were not significant (P > 0.05), and there was a downward trend. The correlation analysis showed that the correlation between soil water content in the 0–20 cm soil layer and groundwater depth was the highest, and a regression equation was established to roughly estimate groundwater depth from the soil water data. The results showed that the excavation of diversion canals in wetlands had a strong impact on the spatial and temporal distributions of the groundwater depth and soil moisture, and that it disturbed the normal hydrological cycle, which leads to the degradation of the wetland ecological environment. The results revealed the hydrological change process occurring in the Heihe marsh wetland areas, provide a basis for the rational development and utilization of groundwater resources, and will improve the maintenance of a healthy wetland ecosystem.