A Ramsar wetland in crisis - the Coorong, Lower Lakes and Murray Mouth, Australia

2011 ◽  
Vol 62 (3) ◽  
pp. 255 ◽  
Author(s):  
Richard T. Kingsford ◽  
Keith F. Walker ◽  
Rebecca E. Lester ◽  
William J. Young ◽  
Peter G. Fairweather ◽  
...  
Keyword(s):  
Environmental Flows ◽  
Large River ◽  
Freshwater Ecosystems ◽  
Water Levels ◽  
Environmental Benefits ◽  
Low Flow ◽  
Freshwater Turtles ◽  
Murray Darling Basin ◽  
High Conservation ◽  
Sulfate Soils

The state of global freshwater ecosystems is increasingly parlous with water resource development degrading high-conservation wetlands. Rehabilitation is challenging because necessary increases in environmental flows have concomitant social impacts, complicated because many rivers flow between jurisdictions or countries. Australia’s Murray–Darling Basin is a large river basin with such problems encapsulated in the crisis of its Ramsar-listed terminal wetland, the Coorong, Lower Lakes and Murray Mouth. Prolonged drought and upstream diversion of water dropped water levels in the Lakes below sea level (2009–2010), exposing hazardous acid sulfate soils. Salinities increased dramatically (e.g. South Lagoon of Coorong >200 g L–1, cf. modelled natural 80 g L–1), reducing populations of waterbirds, fish, macroinvertebrates and littoral plants. Calcareous masses of estuarine tubeworms (Ficopomatus enigmaticus) killed freshwater turtles (Chelidae) and other fauna. Management primarily focussed on treating symptoms (e.g. acidification), rather than reduced flows, at considerable expense (>AU$2 billion). We modelled a scenario that increased annual flows during low-flow periods from current levels up to one-third of what the natural flow would have been, potentially delivering substantial environmental benefits and avoiding future crises. Realisation of this outcome depends on increasing environmental flows and implementing sophisticated river management during dry periods, both highly contentious options.

scholarly journals Scavenging by threatened turtles regulates freshwater ecosystem health during fish kills

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Claudia Santori ◽  
Ricky-John Spencer ◽  
Michael B. Thompson ◽  
Camilla M. Whittington ◽  
Thomas H. Burd ◽  
...  
Keyword(s):  
Water Quality ◽  
Ecosystem Health ◽  
Freshwater Ecosystems ◽  
Freshwater Ecosystem ◽  
Freshwater Species ◽  
Freshwater Turtles ◽  
Fish Kills ◽  
Murray Darling Basin ◽  
Ecological Implications ◽  
Mesocosm Experiments

Abstract Humans are increasing the frequency of fish kills by degrading freshwater ecosystems. Simultaneously, scavengers like freshwater turtles are declining globally, including in the Australian Murray–Darling Basin. Reduced scavenging may cause water quality problems impacting both ecosystems and humans. We used field and mesocosm experiments to test whether scavenging by turtles regulates water quality during simulated fish kills. In the field, we found that turtles were important scavengers of fish carrion. In mesocosms, turtles rapidly consumed carrion, and water quality in mesocosms with turtles returned to pre-fish kill levels faster than in turtle-free controls. Our experiments have important ecological implications, as they suggest that turtles are critical scavengers that regulate water quality in freshwater ecosystems. Recovery of turtle populations may be necessary to avoid the worsening of ecosystem health, particularly after fish kills, which would have devastating consequences for many freshwater species.

scholarly journals Accounting for environmental flow requirements in global water assessments

2014 ◽  
Vol 18 (12) ◽  
pp. 5041-5059 ◽  
Author(s):  
A. V. Pastor ◽  
F. Ludwig ◽  
H. Biemans ◽  
H. Hoff ◽  
P. Kabat
Keyword(s):  
Flow Regime ◽  
Environmental Flows ◽  
Environmental Flow ◽  
Ecological Condition ◽  
Freshwater Ecosystems ◽  
Low Flow ◽  
Human Needs ◽  
High Flows ◽  
The Mean ◽  
Global Vegetation

Abstract. As the water requirement for food production and other human needs grows, quantification of environmental flow requirements (EFRs) is necessary to assess the amount of water needed to sustain freshwater ecosystems. EFRs are the result of the quantification of water necessary to sustain the riverine ecosystem, which is calculated from the mean of an environmental flow (EF) method. In this study, five EF methods for calculating EFRs were compared with 11 case studies of locally assessed EFRs. We used three existing methods (Smakhtin, Tennant, and Tessmann) and two newly developed methods (the variable monthly flow method (VMF) and the Q90_Q50 method). All methods were compared globally and validated at local scales while mimicking the natural flow regime. The VMF and the Tessmann methods use algorithms to classify the flow regime into high, intermediate, and low-flow months and they take into account intra-annual variability by allocating EFRs with a percentage of mean monthly flow (MMF). The Q90_Q50 method allocates annual flow quantiles (Q90 and Q50) depending on the flow season. The results showed that, on average, 37% of annual discharge was required to sustain environmental flow requirement. More water is needed for environmental flows during low-flow periods (46–71% of average low-flows) compared to high-flow periods (17–45% of average high-flows). Environmental flow requirements estimates from the Tennant, Q90_Q50, and Smakhtin methods were higher than the locally calculated EFRs for river systems with relatively stable flows and were lower than the locally calculated EFRs for rivers with variable flows. The VMF and Tessmann methods showed the highest correlation with the locally calculated EFRs (R2=0.91). The main difference between the Tessmann and VMF methods is that the Tessmann method allocates all water to EFRs in low-flow periods while the VMF method allocates 60% of the flow in low-flow periods. Thus, other water sectors such as irrigation can withdraw up to 40% of the flow during the low-flow season and freshwater ecosystems can still be kept in reasonable ecological condition. The global applicability of the five methods was tested using the global vegetation and the Lund-Potsdam-Jena managed land (LPJmL) hydrological model. The calculated global annual EFRs for fair ecological conditions represent between 25 and 46% of mean annual flow (MAF). Variable flow regimes, such as the Nile, have lower EFRs (ranging from 12 to 48% of MAF) than stable tropical regimes such as the Amazon (which has EFRs ranging from 30 to 67% of MAF).

scholarly journals Predicting Subseasonal Hydrological Droughts for Swiss Lakes and Large Rivers – Combining Mesoscale Hydrological EPS and Machine Learning Approaches  

2021 ◽  
Author(s):  
Annie Yuan-Yuan Chang ◽  
Simone Jola ◽  
Konrad Bogner ◽  
Daniela I.V. Domeisen ◽  
Massimiliano Zappa
Keyword(s):  
Machine Learning ◽  
Warning System ◽  
River Basins ◽  
Large River ◽  
Water Levels ◽  
Machine Learning Algorithms ◽  
Low Flow ◽  
Drought Event ◽  
Learning Approaches ◽  
Meteorological Forcing

<p>Although Switzerland is not commonly associated with the occurrence of droughts, in recent years, Switzerland has experienced several unprecedented drought events. Considering that many sectors in Switzerland depend heavily on its water resources, hydropower production, navigation and transportation, agriculture, and tourism, it is important to establish a reliable warning system for early drought recognition. Drought forecast at subseasonal timescales, particularly the onset of a drought event, remains a challenge which is linked to the limited skill of subseasonal meteorological forecasts especially in Europe. The goal of this research is to develop a model to produce skillful subseasonal prediction of low-flows in large river basins and water levels of the major lakes in Switzerland. The envisaged methodology combines monthly hydro-meteorological forecast outputs from the hydrological model PREVAH (Precipitation-Runoff-Evapotranspiration HRU model) with machine learning algorithms. An operational setup of PREVAH has been previously implemented for Switzerland with meteorological forcing from 51 ensemble members and 32 days lead time from the operational extended-range prediction system of the European Centre for Medium-Range Weather Forecasts (ECMWF). Although the PREVAH forecasts are considered semi-idealized (assuming natural flow conditions) and they do not go through an in-depth calibration process, they provide a robust representation of the hydrological processes at the catchment level. The proposed machine learning model is expected to mimic the flow routing mechanism and match PREVAH forecasts from its 300 catchments with measured streamflow and lake level in river basins. The proof-of-concept will focus on the river Aare until the station of Brügg-Aegerten, downstream of the lake of Biel. The findings of this work will highlight the potential of directly linking mesoscale hydro-meteorological forecasts with streamflow and providing subseasonal low-flow predictions in an operational set-up.</p>

scholarly journals The Pongola Floodplain, South Africa – Part 1: Two-dimensional hydrodynamic modelling in support of an environmental flows assessment

Water SA ◽  
2018 ◽  
Vol 44 (4 October) ◽  
Author(s):  
AL Birkhead ◽  
CA Brown ◽  
AR Joubert ◽  
A Singh ◽  
T Tlou
Keyword(s):  
Environmental Flows ◽  
Monitoring Network ◽  
Companion Paper ◽  
Water Levels ◽  
Low Flow ◽  
Hydrodynamic Modelling ◽  
Two Dimensional ◽  
River Channels ◽  
Meandering River ◽  
Hydraulic Behaviour

The Pongola Floodplain in the Makhathini Flats is an area of low topographic relief between the 1973-commissioned Jozini Dam, and the Usuthu River which borders Mozambique. The floodplain system is characterised by a complex mosaic of meandering river channels, levees, and floodplains interspersed with pans (or depressions) and wetlands. The landmark 1982 study of the floodplain, Man and the Pongolo Floodplain, suggested a pattern of flows to ‘maintain the floodplain’ based on socio-ecological criteria. Since 1998, however, annual releases have been primarily targeted at the needs of recession agriculture and inundation of the floodplain in the Ndumu Reserve. No releases have been specifcally aimed at maintaining the floodplain ecosystem and the services it delivers to support the livelihoods of local communities. In 2013, the Department of Water and Sanitation commissioned an Ecological Reserve study of the Usuthu/Mhlatuze Water Management Area, which incorporates the Pongola Floodplain. This paper describes two-dimensional hydrodynamic modelling using RMA2 to inform this flow assessment. Four computational Pongola Floodplain models have been developed since 1979, including cell-based, one- and two-dimensional approaches. The RMA2 model is based on existing topographical, hydrological and hydraulic information, and was calibrated and verifed for the period 2008 to 2010 using water-level data from the local hydrometric monitoring network. Generally, good replications have been achieved in terms of peaks, rising and recession limbs, recession of ponded pan water-levels, and low-flow river stages. The RMA2 modelling represents an advancement of previous hydrodynamic studies of the floodplain and contributes to an improved understanding of its hydraulic behaviour. Model application was for the 15-year period 1990 to 2004, and simulations included naturalised, present management (2014), and 7 potential dam operational scenarios. The results were post-processed for analyses in the DRIFT DSS, described in the companion paper.

Environmental flows and water quality objectives for the River Murray

2002 ◽  
Vol 45 (11) ◽  
pp. 251-260 ◽  
Author(s):  
C. Gippel ◽  
T. Jacobs ◽  
T. McLeod
Keyword(s):  
Water Quality ◽  
Environmental Flows ◽  
Flow Regulation ◽  
Environmental Flow ◽  
Environmental Benefits ◽  
Flow Management ◽  
Management Actions ◽  
Murray Darling Basin ◽  
Ministerial Council ◽  
Water Quality Objectives

Over the past decade, there intense consideration of managing flows in the River Murray to provide environmental benefits. In 1990 the Murray-Darling Basin Ministerial Council adopted a water quality policy: To maintain and, where necessary, improve existing water quality in the rivers of the Murray-Darling Basin for all beneficial uses - agricultural, environmental, urban, industrial and recreational, and in 1994 a flow policy: To maintain and where necessary improve existing flow regimes in the waterways of the Murray-Darling Basin to protect and enhance the riverine environment. The Audit of Water Use followed in 1995, culminating in the decision of the Ministerial Council to implement an interim cap on new diversions for consumptive use (the “Cap”) in a bid to halt declining river health. In March 1999 the Environmental Flows and Water Quality Objectives for the River Murray Project (the Project) was set up, primarily to establish water quality and environmental flow objectives for the River Murray system. A Flow Management Plan will be developed that aims to achieve a sustainable river environment and water quality, in accordance with community needs, and including an adaptive approach to management and operation of the River. It will lead to objectives for water quality and environmental flows that are feasible, appropriate, have the support of the scientific, management and stakeholder communities, and carry acceptable levels of risk. This paper describes four key aspects of the process being undertaken to determine the objectives, and design the flow options that will meet those objectives: establishment of an appropriate technical, advisory and administrative framework; establishing clear evidence for regulation impacts; undergoing assessment of environmental flow needs; and filling knowledge gaps. A review of the impacts of flow regulation on the health of the River Murray revealed evidence for decline, but the case for flow regulation as the main cause is circumstantial or uncertain. This is to be expected, because the decline of the River Murray results from many factors acting over a long period. Also, the health of the river varies along its length, from highly degraded to reasonably healthy, so it is clear that different approaches will be needed in the various river zones, with some problems requiring reach or even point scale solutions. Environmental flow needs have been determined through two major Expert Panel reports that identified the ecological priorities for the river. The next step is to translate these needs into feasible flow management actions that will provide the necessary hydrological conditions. Several investigations are underway to recommend options for flow management. Two important investigations are described in this paper: how to enhance flows to wetlands of national and international significance, and how to physically alter or change the operation of structures (including a dam, weir, lock, regulator, barrage or causeway), to provide significant environmental benefits. Early modelling suggests that the only option which has a positive environmental effect in all zones of the River is a reduction in overall water consumption.

scholarly journals Water Temperature and Hydrological Modelling in the Context of Environmental Flows and Future Climate Change: Case Study of the Wilmot River (Canada)

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2101
Author(s):  
Christian Charron ◽  
André St-Hilaire ◽  
Taha B.M.J. Ouarda ◽  
Michael R. van den Heuvel
Keyword(s):  
Climate Change ◽  
Water Temperature ◽  
Environmental Flows ◽  
Low Flow ◽  
Future Climate Change ◽  
Climate Change Scenarios ◽  
Water Abstraction ◽  
Surface Water Flow ◽  
Modelling Studies ◽  
Rcp 8.5

Simulation of surface water flow and temperature under a non-stationary, anthropogenically impacted climate is critical for water resource decision makers, especially in the context of environmental flow determination. Two climate change scenarios were employed to predict streamflow and temperature: RCP 8.5, the most pessimistic with regards to climate change, and RCP 4.5, a more optimistic scenario where greenhouse gas emissions peak in 2040. Two periods, 2018–2050 and 2051–2100, were also evaluated. In Canada, a number of modelling studies have shown that many regions will likely be faced with higher winter flow and lower summer flows. The CEQUEAU hydrological and water temperature model was calibrated and validated for the Wilmot River, Canada, using historic data for flow and temperature. Total annual precipitation in the region was found to remain stable under RCP 4.5 and increase over time under RCP 8.5. Median stream flow was expected to increase over present levels in the low flow months of August and September. However, increased climate variability led to higher numbers of periodic extreme low flow events and little change to the frequency of extreme high flow events. The effective increase in water temperature was four-fold greater in winter with an approximate mean difference of 4 °C, while the change was only 1 °C in summer. Overall implications for native coldwater fishes and water abstraction are not severe, except for the potential for more variability, and hence periodic extreme low flow/high temperature events.

Relationship between Waterway Depth and Low-Flow Water Levels in Reaches below the Three Gorges Dam

2019 ◽  
Vol 145 (1) ◽  
pp. 04018032 ◽  
Author(s):  
Yunping Yang ◽  
Mingjin Zhang ◽  
Wanli Liu ◽  
Jianjun Wang ◽  
Xiaoxing Li
Keyword(s):  
Water Levels ◽  
Three Gorges Dam ◽  
Low Flow ◽  
Three Gorges ◽  
The Three Gorges ◽  
The Three Gorges Dam

scholarly journals LifeDNAquatic: A priori settings and refined pipelines of eDNA metabarcoding to generate "big data" for solid fish, mussel and amphibian SDMs

2021 ◽  
Vol 4 ◽  
Author(s):  
Micaela Hellstrom ◽  
Kat Bruce ◽  
Rein Brys ◽  
Bernd Hänfling ◽  
David Halfmaerten ◽  
...  
Keyword(s):  
Big Data ◽  
A Priori ◽  
Large River ◽  
Freshwater Ecosystems ◽  
Distribution Data ◽  
Sampling Strategies ◽  
Distribution Models ◽  
Spatial Changes ◽  
Landscape Scales ◽  
Field Planning

Sound environmental management decisions - in accordance with the EU WFD for aquatic ecosystems – mainly depend on reliable species presence- and distribution- data. Here we present a workflow from sampling strategies to results and decision making using eDNA metabarcoding analyses for fish, amphibians, and mussels from habitat to landscape scales with focus on sampling strategies for "big data" in marine and freshwater ecosystems in Sweden. The project LifeDNAquatic highlights a solid eDNA pipeline and comparison of methods, which cover field planning and the entire pipeline generating data for Species Distribution Models (SDMs). Intense sampling over a large river catchment highlights previoulsy unanswered questionsand and provides insights to a priori settings for sampling strategies to retrieve "big data". The results provide novel insights to DNA distribution in the environment, seasonal and spatial changes in eDNA composition, and validation of data.

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