ABSTRACT
Preserving lacustrine ecosystems is vital for sustainable watershed development, and forecasting the environmental water availability of lakes would support policymakers in developing sound management strategies. This study proposed a methodology that merges the lake water level prediction and environmental water availability evaluation. The temporal fusion transformer (TFT) model forecasted the lake water levels for the next 7 days by inputting the streamflow and lake water level data for the past 30 days. The environmental water availability was assessed by comparing the forecasted lake water levels with the environmental water requirements, resulting in adequate, regular, scarce, and severely scarce environmental water availability. The methodology was tested in two case studies: Poyang Lake and Dongting Lake, the two largest freshwater lakes in the Yangtze River Basin, China. The TFT model performed well in forecasting the lake water levels, as shown by the high coefficient of determination and finite root mean square error. The coefficients of determination exceeded 0.98 during the model training, validation, and test for both Poyang Lake and Dongting Lake, and the root mean square errors ranged from 0.06 to 0.46 m. The accurate prediction of lake water level promoted the precise forecasting of the environmental water availability with the high Kappa coefficient exceeding 0.90. Results indicated the rationality and effectiveness of integrating the lake water level prediction and environmental water availability evaluation. Future research includes the applicability of the TFT model to other lakes worldwide to test the proposed approach and investigate strategies to cope with environmental water scarcity.
Subject(s)
Ecosystem , Lakes , Water , Environmental Monitoring/methods , ChinaABSTRACT
Spatial scale is a crucial factor in drought propagation and characterization. To investigate the response behavior of the meteorological drought-hydrological drought propagation to different watershed scales, three nested subbasins in the upper Huaihe River basin were selected as case study sites. The Standardized Precipitation Index and the Standardized Streamflow Index were adopted to characterize the meteorological drought and hydrological drought respectively. The relationship between meteorological drought and hydrological drought was then examined by wavelet coherency analysis and linear/nonlinear regression models. Results showed that (1) linear regression model captured drought propagation best in all subbasins, and the correlation strengthened as the watershed area increased with drought duration being highest correlated among the five drought characteristics; (2) with the watershed area growth, the coherence between hydrological and meteorological drought reduced, the lagging effect of hydrological drought attenuated, and the hydrological one tended to be more synchronized with meteorological one over the long period; and (3) the larger the watershed scale, the later (earlier) occurrence of the hydrological drought onset (termination), while the longer drought duration and larger magnitude for triggering hydrological drought.
