Sensitivity of streamflow patterns to river regulation and climate change and its implications for ecological and environmental management

Impacts of changes in climate and water demand on flow in a subtropical river catchment below a major dam

River flow regime is important for ecosystem integrity and biodiversity, and is impacted by artificial water exploitation and regulation, extreme events and climate change. Environmental flows are designed to mitigate these impacts. In this work, we used catchment hydrological output simulated by the Soil & Water Assessment Tool model, evaporation rates calculated with the General Lake Model and a water resource management tool to calculate a water balance for a sub-tropical reservoir located in southeast Queensland, Australia under extreme dry conditions impacted by climate change. Two environmental flows, the 90th percentile of the daily flow duration curve (Q90) and the 90th percentile monthly flow for each season (Q90M), were used to assess water availability for multiple purposes including environmental releases and water supply from a subtropical water supply reservoir. Risks for the downstream river system were assessed using a flow alteration screening method by comparing a 20-year baseline period of no-dam from 1990 to 2009 with future climate change and water regulation conditions with the dam in place. A significant decrease in maximum flood peak, persistence of high-flow duration and the annual discharge from the reservoir occurred with future climate change and water demand scenarios compared with the no-dam baseline. The future changes in flow regime indicate a medium-to-high ecological risk for high flow conditions and moderate ecological risk during low flow conditions compared with the no-dam condition. An increased water demand in combination with future climate change leads to high ecological risks occurring by the end of this century under the high emission scenario of representative concentration pathway 8.5, regardless of the water regulations and environment flow management. The findings of this work indicate moderate to high inability to meet water demand under future climate-induced hydrological change. Therefore, catchment managers will need to take further actions to mitigate impacts from future climate change and population growth on water resources in this subtropical system.

River regulation and climate change reduce river flows to major Australian floodplain wetland

Freshwater ecosystems, including rivers and floodplain wetlands, face severe stress from unsustainable water resources development, with climate change exerting further pressure. This study compares the relative effects of river regulation and projected climate change on river flows to the semi-arid Lowbidgee Floodplain (3250 km2), the largest wetland ecosystem on the heavily regulated Murrumbidgee River, Australia's second longest river, within the Murray-Darling Basin. We modelled annual natural streamflow in the lower Murrumbidgee River before major dam constructions and water diversions (1890-1927), linking river flows to runoff from the upper Murrumbidgee catchment. Extending this analysis to the full rainfall-runoff dataset (1890-2018), we compared modelled natural flows to observed river flows affected by dams and water withdrawals. Additionally, we modelled climate change impacts on river discharge and overbank flows, which reduced inundation of riparian habitats. Current river regulation has reduced median annual streamflow by 43% from 2565 × 106 m³ to 1490 × 106 m³ during 1958-2018, relative to modelled natural flows, with a more pronounced 55% reduction in the last three decades (1988-2018). The return period of major overbank flows, essential for river-floodplain habitat connectivity, more than doubled from once every 2.0 years to once every 4.4 years (1916-2018). Mean climate change projections indicated an additional 7-10% decrease in median annual streamflow by 2047-2075, relative to 1977-2005. The annual duration of major floods declined from an average of 11.3 days under natural flow conditions to 4.5 days under the current regulated river flow regime, with a further reduction to 1.6-1.8 days (83-85% decrease) projected by 2047-2075, due to climate change. We recommend prioritising mitigation of river regulation effects, as these pose the most immediate threats to riverine ecosystems, including their native biodiversity, in the Murrumbidgee River catchment. Our 'natural flow' model offers critical insights for shaping environmental policy and managing environmental flows to mimic natural flow regimes, supporting the conservation and restoration of freshwater ecosystems, like the Lowbidgee Floodplain wetlands. Our approach is transferable to other large river systems globally, using available or modelled streamflow data.

Impacts of LULC and climate changes on hydropower generation and development: A systematic review

There is a growing concern on a global scale that the world should transition towards the utilisation of energy-efficient technologies. Hydropower plays a very significant part in the fight against climate change, and as a result, it lessens the impact that climate changewill have on our ability to achieve the Sustainable Development Goals (SDGs). Both the effectiveness of hydropower generation and the amount of streamflow are impacted by climate change as well as land use and land cover (LULC). Accordingly, the purpose of this study is to conduct a literature review on the topic of the past and future effects of climate, land use, and land cover changes on hydropower generation. This review will be based on the entries found in a number of reliable databases. A systematic literature review was carried out to analyse how LULC and climate change will affect hydropower generation and development. The research was based on 158 pieces of relevant literature that had been reviewed by experts and indexed in Scopus, Google Scholar, and ScienceDirect. The review was carried out to determine three goals in mind: the impact of climate change on hydropower generation and development; the impact of climate change on streamflow; and the combined impact of changes in climate and changes in LULC on hydropower. The findings bring to light the primary factors contributing to climate change as well as shifts in LULC which are essential to the generation of hydropower on all scales. The study identifies factors such as precipitation, temperature, floods, and droughts as examples of climate change. Deforestation, afforestation, and urbanisation are identified as the primary causes of changes in LULC over the past several decades. These changes have a negative impact on the generation and development of hydropower.

Can China's ecological civilization strike a balance between economic benefits and green efficiency? A preliminary province-based quasi-natural experiment

To encourage the building of a development route for ecological civilization construction which commensurates with China's unique national conditions, early demonstration and pilot ecological civilization zones should be built. This study aims to investigate the effects of ecological civilization construction policies on regional total factor productivity, green total factor productivity, and the methods of action by using panel data from 30 provinces in Mainland China from 2005 to 2020. Our findings indicate that the pilot eco-civilization policies have a more significant effect on the promotion of green total factor production, while the effect on total factor productivity is average. Furthermore, the main purpose of the ecological civilization construction pilot is to improve the level of green innovation, optimise the industrial structure and promote the allocation of factors to achieve a win-win situation for regional economic development and green benefits. Moreover, under different levels of economic growth, the pilot eco-civilization policies have a more significant effect on the promotion of green total factor at various stages of economic growth and industrialization. There are also clear discrepancies in how well ecological civilization construction programmes are implemented. Thus, in order to support high-quality regional economic development, it is crucial to continue to advance and promote the pilot eco-civilization initiatives.

Reservoir Regulation for Ecological Protection and Remediation: A Case Study of the Irtysh River Basin, China

Hydrological processes play a key role in ecosystem stability in arid regions. The operation of water conservancy projects leads to changes in the natural hydrological processes, thereby damaging the ecosystem balance. Ecological regulation is an effective non-engineering measure to relieve the influence of water conservancy projects on ecosystems. However, there are still some problems, such as an insufficient understanding of hydraulic processes and difficulty evaluating the application effects. In this study, the theory of ecological reservoir regulation coupled with hydrological and ecological processes was examined and ecological protection and remediation were investigated using the valley forests and grasslands in the Irtysh River Basin as a case study. The results demonstrated that (1) to meet the demand of the hydrological processes in the valley forests and grasslands, in terms of ecological regulation, the peak flow and flood peak duration of the reservoir, named 635, in the Irtysh River Basin should be 1000 m³ s⁻¹ and 168 h, respectively, and the total water volume of ecological regulation should be 605 million m³. Ecological regulation can guarantee that the floodplain range reaches 64.3% of the core area of ecological regulation and the inundation duration in most areas is between 4–8 d; (2) an insufficient ecological water supply would seriously affect the inundation effects. The inundation areas were reduced by 2.8, 5.1, 10.3, and 19.3%, respectively, under the four insufficient ecological water supply conditions (528, 482, 398, and 301 million m³), and the inundation duration showed a general decreasing trend; (3) the construction of ecological sluices and the optimization of the reservoir regulation rules could effectively relieve the influences of an insufficient ecological water supply. At water supply volumes of 528 and 482 million m³, the regulation rules should assign priority to the flood peak flow; at water supply volumes of 398 and 301 million m³, the regulation rules should assign priority to the flood peak duration. Consequently, this study provides a reference for ecological protection in arid regions and the optimization of ecological regulation theories.