Regreening Practices and Effectiveness Evaluation for Rocky Slope Drawdown Zones in Pumped Storage Power Station Reservoirs

Abstract

[Objective] Reservoir construction has severely degraded the ecological environment of reservoir banks. The high-frequency, large-amplitude water level fluctuations make ecological restoration in the drawdown zone particularly challenging. After the operation of Henan Tianchi Pumped Storage Power Station, the water level exhibits significant weekly regulation fluctuations, resulting in large areas of exposed concrete on reservoir banks, severe fragmentation of the drawdown zone, and extreme habitat stress that greatly impedes vegetation restoration. This study focuses on the ecological restoration of the rocky slope drawdown zone in the Henan Tianchi Pumped Storage Power Station reservoir to ensure water resource security. [Methods] To address the severely impaired ecological function of the drawdown zone, this study conducted systematic analysis of habitat characteristics, including hydrological patterns, bank characteristics, non-point source pollution, and plant communities. Focusing on the critical need for ecological restoration in rocky slope drawdown zones of pumped storage reservoirs, this study investigated regreening approaches targeting growth substrate construction, plant community rehabilitation, and vegetation management. [Results] After more than one year of implementation, vegetation in the drawdown zone showed robust growth. No slope failure or soil erosion was observed. Plants exhibited strong resilience in terms of post-submersion recovery, expansion, and colonization, achieving an overall survival rate of 83.2%. Bamboo Willow (Salix sp), Bamboo Willow cuttings (Salix sp), Zhongshan Fir (Taxodium hybrid), Wallich Willow (Salix wallichiana), Chaste Tree (Vitex negundo), Lax-flowered Myricaria (Myricaria laxiflora), Variegated Willow cuttings (Salix variegata), Small Dogwood (Swida paucinervis), and Chinese Distylium (Distylium chinense) all achieved survival rates exceeding 85% and exhibited long-term tolerance to complete submersion. Planting Variegated Willow (Salix variegata) using cuttings was recommended to enhance its survival rate. Through practical restoration efforts within the test area, 13 plant species tolerant to submersion, drought, and barren conditions were selected: Zhongshan Fir (Taxodium hybrid), Bamboo Willow (Salix sp), Wallich Willow (Salix wallichiana), Lax-flowered Myricaria (Myricaria laxiflora), Variegated Willow (Salix variegata), Small Dogwood (Swida paucinervis), Chinese Distylium (Distylium chinense), Chaste Tree (Vitex negundo), Bermuda Grass (Cynodon dactylon), Indian Shot (Canna indica), Lamb’s Quarters (Chenopodium album), Violet Orychophragmus (Orychophragmus violaceus), and Cosmos (Cosmos bipinnatus). [Conclusion] Ecological restoration of rocky slope drawdown zones in pumped storage reservoirs requires an integrated approach combining engineering and biological measures. Engineering measures provide the essential soil substrate for plant growth and ensure vegetation survival. Based on a comprehensive consideration of topography, geology, and water level fluctuation patterns, the geogrid + ecological bag + hanging net composite technique is applied in permanently exposed and alternately submerged zones, while the long-fiber ecological bag + mesh reinforcement composite technique is used in permanently submerged zones. Vegetation measures should adopt a tree-shrub-herb configuration model tailored to the degree of submersion stress and the desired landscape effect. ①Permanently exposed zone. Trees: Bamboo Willow (Salix sp), Zhongshan Fir (Taxodium hybrid), Wallich Willow (Salix wallichiana)+Shrubs: Chaste Tree (Vitex negundo) +Herbs: Cosmos (Cosmos bipinnatus), Violet Orychophragmus (Orychophragmus violaceus), Lamb’s Quarters (Chenopodium album), Indian Shot (Canna indica), and Bermuda Grass (Cynodon dactylon). ②Alternately submerged zone. Trees: Bamboo Willow (Salix sp), Zhongshan Fir (Taxodium hybrid) +Shrubs: Variegated Willow (Salix variegata), Small Dogwood (Swida paucinervis), and Lax-flowered Myricaria (Myricaria laxiflora) +Herbs: Bermuda Grass (Cynodon dactylon). ③Permanently submerged zone. Shrubs: Variegated Willow (Salix variegata), Small Dogwood (Swida paucinervis), and Chinese Distylium (Distylium chinense) +Herbs: Bermuda Grass (Cynodon dactylon). The findings hold significant implications for scientifically guiding regreening efforts in rocky slope drawdown zones of pumped storage power station reservoirs.

Keywords

• rocky slope drawdown zone|ecological restoration|vegetation|regreening practice|pumped storage power station|henan tianchi