The Influence of Tributary Runoff Components on the Dynamics of the Khanka Lake Level

For twelve rivers in the Lake Khanka basin, river runoff components were simulated using the HBV model structure with groundwater delay. Statistical smoothing methods were used to eliminate the effect of wind-induced setup and setdown on the measured levels, and the lake level observation data were decomposed into the main trend, seasonal, and residual components. The modeling results showed that the specific time period during which the bulk of groundwater reaches the discharge area is 2–3 years. Comparison of the components obtained from STL decomposition of the lake levels after removing the surge component with the model runoff components showed that only the main trend is statistically related to the groundwater runoff of the largest rivers in the catchment area. The analysis of the obtained results suggested that the existence of sufficiently long periods of stable high lake levels occurs with a combination of an increased annual inflow and groundwater travel formed in the catchment area due to precipitation in previous years; accordingly, the decrease in the lake level occurs with a delay of 2–3 years after the onset of the low-water phase.