Damming rivers: How it harms fish and what can be done
Editors’ voice It is a blog from the Publications Department at the Arabian Gulf University.
River dams play an essential role in flood management, energy production and water supply around the world. In order to achieve social and economic development, more than half of the world’s large rivers (>1000 km) no longer flow freely. However, dam construction operations have significantly changed the geophysical conditions of rivers, which in turn has affected river ecosystems. The impact of river dam construction on fish and associated conservation measures has particularly drawn the attention of stakeholders, researchers and environmentalists.
A recent study in Geophysics assessments Comprehensively review the effects of river damming on fish habitats. It analyzed the advantages, disadvantages and cost benefits of major mitigation measures providing a global perspective on fish conservation in dammed rivers. We asked the authors to provide an overview of these impacts, mitigation measures, and their recommendations for future research.
How does building dams on rivers affect fish species and their habitats?
Dam construction affects fish habitats in several ways. First, it reduces the longitudinal, lateral and vertical connectivity of rivers, affecting fish migration, spawning and foraging. Second, the construction of dams alters the sediment regime and morphology of rivers, thus altering fish microhabitats. Third, reservoir operations significantly distort hydrological regimes and river water temperatures, affecting fish reproduction, foraging and wintering. Finally, flood flows from large dams oversaturate the total dissolved gas in the downstream water, causing fish gas bubble disease and even death.
All of these changes in fish habitats significantly impact the populations and community structure of global fish species, such as salmonids, Chinese carp, sturgeon, and eels.
What conservation measures are being taken to mitigate the negative impacts of river dam construction on fish?
A variety of conservation measures have been adopted. For example, different types of fish passage facilities have been installed at river dams to restore biological connectivity for fish. Based on nature-based solutions, reservoir ecological processes have been implemented to mitigate the effects of changes in river hydrology and water temperature on fish. Small dams and levees in tributaries have been removed to rehabilitate and replace lost fish habitat in the main tributaries of the dams. For some commercial and endangered fish species, artificial breeding and release have been applied to maintain genetic diversity and restore fishery resources.
These conservation measures have different applicability, efficiency and cost-effectiveness. It is important to choose appropriate conservation measures based on the practical engineering conditions of the dam, the characteristics of the target fish, and the cost-effectiveness of the conservation measures.
Our review has highlighted river biogeophysical studies and provides important guidance for fish conservation in dammed rivers, supporting coordination between river development and ecosystem conservation. It is of interest to geophysical researchers, managers and policy makers working in this field.
What additional research, data, or models are needed to help conserve fish in dammed rivers?
In the future, climate change and human activities may further complicate the problem. To deal with the combined impacts of climate change and human activities, we recommend the following:
- Develop master plans for damming basin-wide rivers to reduce impacts on fish habitats;
- Establish dedicated monitoring networks in dammed rivers to systematically collect hydrological and ecological data;
- Conduct evaluations of the effectiveness and efficiency of conservation measures to achieve further improvements; And
- Consider the complex impacts of climate change and land cover changes on dammed rivers in any conservation measures.
– Qiwen Chen (firstname.lastname@example.org, 0000-0003-0905-7591); Jianyun Zhang (email@example.com, 0000-0001-5586-4058); And Qinyuan Li (firstname.lastname@example.org, 0000-0002-2958-6813), Nanjing Hydraulic Research Institute, China.
Editor’s Note: It is the policy of AGU Publications to invite authors of articles published in Geophysics Reviews to write a summary for the Eos editors.