A refined groundwater flow model of the shallow aquifer in Tianjin Municipality, China

The assembly of a groundwater flow model for the shallow aquifer in Tianjin Municipality is outlined in this paper. Tianjin Municipality was selected because of its complicated hydrogeological conditions and rich data, which could be used to test a refined groundwater flow model for the shallow aquifer. When a shallow groundwater flow model is being assembled its recharge and discharge functions need to represent inflows from rainfall, irrigation return flows, seepage from rivers and reservoirs, and lateral inflows and outflows from evaporation, abstraction of groundwater for irrigation and industrial, and urban use. When abstracting groundwater, the water exchanges between a shallow aquifer and a deep aquifer also need to be considered. The real irrigation areas of Tianjin Municipality were input into the groundwater flow model, and the rivers and reservoirs were refined to the level of secondary tributaries and small scale reservoirs. The model calibration was carried out based on consideration of representative parameter values and their spatial distribution, the groundwater flow fields, the temporal variation in groundwater heads and the water balance for the years 2006–2008. It was concluded from a comparison of the observed and simulated groundwater heads that the precision of the model is high and that the simulated groundwater levels align with the real groundwater conditions. It is also concluded that the groundwater flow model for the shallow aquifer in Tianjin Municipality will be a useful tool for further studies about the relationship between shallow and deep aquifers and the surface environment.