Brisbane, Australia | 20-24 October 2019

The Influence of Cascade Hydropower Development on the

Reproductive Process of Fish with Semi-buoyant Eggs

Qinghui Zeng, Peng Hu

China Institute of Water Resources and Hydropower Research

Brisbane, Australia | 20-24 October 2019

Abstract

1、Background

2、Methods and materials

3、Results

4、Discussion

5、Conclusions

Brisbane, Australia | 20-24 October 2019

1 Background

※ Construction of cascaded hydropower stations disrupt the connectivity among river channels and changesthe natural flood pulse pattern.

※ Changes in the hydraulics have a serious impact on the survival and reproduction of local fish, especially forfish with semi-buoyant eggs, whose survival and reproduction require a specific hydrodynamic condition.

※ It is necessary to thoroughly assess the potential impacts of cascade hydropower development on thereproductive process of fish with semi-buoyant eggs.

Brisbane, Australia | 20-24 October 2019

2 Methods and materials

Eight hydropower stations are planned in the middle reach of Jinsha River. So far, except for Longpanhydropower station and Liangjiaren hydropower station, the construction of the other six hydropower stationshas been completed.

Study Area

Brisbane, Australia | 20-24 October 2019

Bathymetry of the Ludila reservoir High-resolution triangle mesh for the Ludila reservoir

Model configuration——MIKE 21

➢ The trajectories of the semi-buoyant eggs and larvae were identified using hydrodynamics coupled to aLagrangian particle movement modeling based on the MIKE 21 Flow Model.

2 Methods and materials

Brisbane, Australia | 20-24 October 2019

Hydrodynamic condition required of fish with semi-buoyant eggs

the velocity threshold of satisfying the fish migration requirement

According to China’s nationalstandard on fishway design, the basicflow velocities (rheotactic speeds) ofmajor migration fishes are 0.2 m/s.

the minimum flow velocity requirement to keep semi-buoyant eggs and larvae in the drift

The lower limit to the velocity inspawning rivers was 0.25 m/s, and eggsand larvae will sink to the bottom andperish if the velocity is less than this value.

2 Methods and materials

Brisbane, Australia | 20-24 October 2019

Scenario definitions

Two basic scenarios were designed to explore whether fishes with semi-buoyant eggs can reproducenaturally under the conditions of (a) different water discharges of Longkaikou hydropower station; and (b)different operating water levels of the reservoir.

2 Methods and materials

Brisbane, Australia | 20-24 October 2019

The calibrated hydrodynamic model showed good agreement between the simulated and observed data for the water surface elevation

3 Results

Hydrodynamic calibration

Brisbane, Australia | 20-24 October 2019

3 Results——Scenario analysis

The impact on migration of fish

➢ The proportion of suitable migration area increased with the increase of water discharge under the same water level condition of the reservoir.

➢ It is difficult to form a fish migration passage in the reservoir in all potential scenarios.

Brisbane, Australia | 20-24 October 2019

The impact on the incubation of semi-buoyant eggs

✓ Dark blue particles:not hatched yet.✓ Cyan particles: hatched successfully but the larvae did not develop the ability to swim.✓ Yellow particles:old enough to survive without the support of the turbulence of the flow.

3 Results——Scenario analysis

Brisbane, Australia | 20-24 October 2019

The impact on the incubation of semi-buoyant eggs

➢ The drifting time was not enough for the eggs to hatch in these three scenarios.➢ The result indicated that the reservoir did not have sufficient hydraulic characteristics to support the

successful recruitment of fish with semi-buoyant eggs in all of the potential operating conditions.

3 Results——Scenario analysis

Brisbane, Australia | 20-24 October 2019

4 Discussion

Limiting cases

➢ the reservoir hydrodynamic conditions met the requirements for fish migration

➢ there still existed an area in which the hydrodynamic conditions could not meet the minimum flow velocity required to keep semi-buoyant eggs and larvae in the drift

Brisbane, Australia | 20-24 October 2019

Limiting cases

(WL=1223 m, Q=20000 m3/s)

➢ All of the eggs arrived at Ludila

hydropower station within 56 h.

➢ the reservoir formed a passage in which the hydrodynamic conditions met the requirements for fish migration and could keep semi-buoyant eggs and larvae in the drift.

4 Discussion

Brisbane, Australia | 20-24 October 2019

➢ Even if the hydrodynamic conditions can keep them in the drift in impossible high-discharge conditions, there was not enough drifting time and distance in the reservoir.

➢ It is possible that they can reproduce successfully after the protection of the tributary

Location of Yanggong river

4 Discussion

Brisbane, Australia | 20-24 October 2019

5 Conclusions

➢ The reservoir on the main stream did not have sufficient hydraulic

characteristics to support the successful recruitment of fish with semibuoyant

eggs.

➢ However, if we select one or two tributaries to protect fish habitats and

eliminate the small hydropower projects on them, it is possible that fish with

semi-buoyant eggs can reproduce successfully in the tributary together with

the main stream.

Brisbane, Australia | 20-24 October 2019