Ecological responses of spawning habitat suitability to changes in flow and thermal regimes influenced by hydropower operation

Abstract

Large reservoirs and dams can fundamentally alter downstream flow and thermal regimes by resetting the flow and water temperature release boundary conditions, resulting in significant impacts on fish habitat suitability. Therefore, it is critically important to understand how the volume and temperature of dam releases to influence downstream hydraulic and temperature dynamics and predict the ecological responses of fish habitat suitability to these changes. In this study, a physically based coupled model framework was developed to identify the temporal and spatial variations of hydraulic and water temperature regimes and the spawning habitat suitability of four major Chinese carps (FMCC) in the middle reach of the Yangtze River below Three Gorges Reservoir (TGR) responded to different upstream boundary conditions established by dam operation. The results showed that the dam discharge volume from TGR mainly affected the downstream hydraulic regime, while dam discharge temperature would have most impact on downstream water temperature. The spawning habitat suitability of FMCC obviously decreased due to TGR operation, and the declined water temperature suitability and the delayed and narrowed window of suitable water temperature were the main influencing factors. For the purpose of maximizing the spawning habitat suitability of FMCC in the downstream reaches below TGR, dam discharge volume ranged from 10,000 to 22,500 m 3 /s, and dam discharge temperature varied from 22 to 23.5 C would be recommended as the outflow conditions in the ecological operation of TGR.

Hydrothermal Impacts of Water Release on Early Life Stages of White Sturgeon in the Nechako River, (B.C. Canada)

“…These human-induced changes can lead to various negative consequences for the aquatic environment. For instance, they can result in increased severity of algal blooms, habitat fragmentation, altered sediment dynamics, changes in hydrology, shifts in thermal regimes, and disruptions to spawning activities (Buxton & Bradley, 2022;Chen et al, 2022;Li et al, 2022;Qiu et al, 2023;Song, 2023;Tang et al, 2022;Wang et al, 2022).…”

Statistical evaluation of a long‐memory process using the generalized entropic value‐at‐risk

“…The un‐normalized skewness and kurtosis refer to the third‐ and fourth‐order centered moments without non‐dimensionalization by the variance. The streamflow discharge is a fundamental indicator of a streamflow environment and an indispensable background driver of water quality indices (Diamond et al, 2022; Laroche et al, 2022) and habitat suitability indices for aquatic fauna (Qiu et al, 2022; Rinaldo & Rodriguez‐Iturbe, 2022). Its statistical evaluation is therefore an indispensable step toward the water environmental assessment.…”