Numerical modeling of the salinity distribution and environmental flows assessment in the Yellow River Estuary, China

Predication of environmental flows is a critical issue in water resourcesmanagement integrated with ecological considerations. It is also a complex issue due to therelationship between ecological and hydrological processes with different temporal andspatial scales in estuarine ecosystems. The salinity gradient is a basic characteristic for anestuary ecosystem, which is largely affected by the alteration of freshwater inflows becauseof human activities. In this paper, a numerical model was developed for simulating thesalinity distribution under the action of river discharge and tide current in the Yellow RiverEstuary. Environmental flow requirements were determined for critical periods in theYellow River Estuary after identifying the salinity objectives for ecosystem health, and thesalinity variability within sensitive habitats in response to fresh water inflow changes. Thetemporal variation of the environmental flows was determined using average monthlynatural river discharge. The impacts of freshwater inflow alteration were assessed based onthe comparison between different environmental flows and river discharges. It is concludedthat the minimum annual environmental flow requirements can be fulfilled by riverdischarge under the action of water and sediment regulation since 2001. River dischargecan meet environmental flow requirements in June, however, it cannot meet the mediumeven the minimum water requirements in other periods of time.