Estimation and attribution of water storage changes in regulated lakes based on Budyko's supply-demand framework

Study region: Lake Dianchi, southwest ChinaStudy focus: Understanding changes in lake water storage (LWS) and its attribution to climate change and human activities is essential for adaptive management of water resources in regulated lakes. Although altimetric measurements, whether ground-or satellite-based, can reproduce LWS dynamics, they do not provide sufficient information on why LWS is changing. Neither the water balance method nor detailed hydrological modeling can capture exactly LWS change in most regulated lakes largely because of the scarcity of water output observations. Here, a simple water balance model, following Budyko's supply-demand framework, was proposed to estimate LWS change in regulated lakes without the need for water output information. The elasticity of LWS was theoretically derived from the Budyko-type model to attribute LWS change to its main driving factors.New hydrological insights for the region: Application of the proposed model to the Lake Dianchi for the period 1964-2022 indicated that the model accurately captured the variations of annual LWS in Lake Dianchi with a relative root mean square error of 4.23%, and correlation coefficient of 0.77. The attribution results suggested that lake regulation strategies were the chief determinant of LWS change in Lake Dianchi, while water transfer had a limited contribution. This study suggests that complex hydrological behavior in regulated lakes can be explored using Budyko's supply-demand framework with a low requirement for data.