Wind-driven hydrodynamic and depositional patterns in shallow lakes

Abstract

Lake Hulun, the fifth-largest lake in China, is a shallow lake (water depth <10 m) with typical wave-dominated landforms developed around the shoreline, with a semi-enclosed bay located in its southern corner. This novel study aims to understand wind-driven hydrodynamics and its related depositional patterns in the data-sparse Lake Hulun. To achieve this, a series of numerical simulations were conducted with a hydrodynamic and sediment transport model. The simulated hydrodynamic patterns are greatly influenced by wind direction shifts but are subject to little impact from wind speed changes which act mainly to accelerate flow. By varying the location and depth of the deepest part of the lake, this study reveals that the location of the depth centre has little impact on the overall hydrodynamic pattern of wind-driven waterbodies. When the wind direction is perpendicular to the long-axis shore, currents around the short-axis shore flow in a direction that follows the wind direction. This study considers the wind-induced longshore currents that are oblique to the long-axis shore as the main driving force in transporting sediments along the shore and erosion of the shoreline. The formation of semi-closed bays in both Lake Hulun, together with its nearby sister lake – Lake Buir – are attributed to the north-west prevailing wind direction. Further exploratory simulations confirmed that prevailing winds tend to induce parallel distributed submerged sediment accumulations in the nearshore zone, challenging the notion of sediment accumulation solely in deep water zones. This study provides valuable insights into the hydro-sedimentary dynamics in wind-driven waterbodies, offering a process-based perspective and contributing to current understanding of the palaeogeography of ancient lake systems.