Satellite based estimation of watershed groundwater storage dynamics in a freeze thaw area under intensive agricultural development
Summary Understanding the temporal spatial characteristics of groundwater storage is critical for agricultural planning and management in the future, thereby causing more challenges in water resource management. However, the special hydrological features of the snow water equivalent, soil moisture, and total canopy water storage in the freeze thawing agricultural area requires the innovative methods for the water resource analysis. The watershed land cover variation and the expanding pattern of the farmlands over a decade were identified using the TM Landsat series data. Combined with the traditional measurements of the water resource, the monthly gravity field data from the Gravity Recovery And Climate Experiment (GRACE) was validated and applied. The water resources distribution based on the remotely sensed data demonstrated that the forest in the watershed center had a larger amount of water storage. The inter annual and seasonal variability of total water storage (TWS) over the agricultural area was analyzed and the higher value appeared in the thawing period of April. The correlations of the TWS streamflow, soil moisture and snow water equivalent with precipitation were all identified. The precipitation was the dominant factor for the watershed TWS and the groundwater dynamics. Under the similar precipitation condition, the lower groundwater storage in recent years was the consequence of the expanding of farmland. The watershed averaged decrease rate of groundwater level from 2003 to 2012 was 1.06 mm/year, which was much lower than the rates in other agricultural areas. The freeze thawing process with smelt snow and rainfall in summer had more time and chance to recharge the groundwater resource and provided the sustainable water resource. This study proved that the application of GRACE was an effective method for the temporal spatial estimation of the TWS anomalies in the freeze thawing agricultural area.