Abstract:

The groundwater exploitable quantity is an important basis for the development, use and management of water resources, and is subject to constraints imposed by the ecological environment and geological conditions. Taking the Puyang irrigation area of the Sanjiang plain as an example, this paper determined the lower limit of the ecological water depth for groundwater development and utilization, aiming to mitigate risks such as the prevention of wetland vegetation degradation, land subsidence, quaternary aquifer dredging, and the disconnection between groundwater and surface water. Based on this, a numerical simulation model of the irrigation area is constructed using MODFLOW to simulate and evaluate the groundwater exploitable quantity. The lower limit of ecological water depth in the irrigation area is between 2.27 and 9.84 m; Based on groundwater numerical simulations, the annual average recharge amount of the irrigation area during the study period (2013-2017) was 25 515.9×104 m3, the discharge volume was 26 194.1×104 m3, and the change of storage volume was -678.3×104 m3, indicating a negative equilibrium, but the burial depth of groundwater level had not yet reached the lower threshold, suggesting that the groundwater still has potential for exploitation. Furthermore, a long-term prediction model was established and calibrated based on the control criteria of ensuring a balance between recharge and discharge and the threshold of the lower limit of the buried depth of the ecological groundwater level, combined with the meteorological and hydrological conditions during the study period. The maximum recoverable groundwater in the irrigation area was determined to be 29 343.2×104 m3/a.

Key words: groundwater resources, groundwater ecological depth, groundwater exploitable resources, Sanjiang plain