Environmental Flow

The demand for sustainable water management has promoted the development of methodologies for estimating environmental flows (EF). In this paper, the EF in an Andean river (Pance, Colombia) for conservation and a Mediterranean river (Wadi-Zomar, Palestine) for restoration purposes is made. Different methodologies are applied given the objectives for each river. The authors used hydrological indices proposed for watersheds with different water regimes and adaptations and validations were made to the local context. These methods allow for estimating the EF at various points in the river and the assessment of disruption scenarios for decision-making. In the Wadi Zomar River, three sampling points were selected. The water samples were then examined for the presence of pathogens. No one indicator or simple hydrological parameter is entirely suitable for all environmental systems and pathogens. In the base flow conditions, the amount of pollutant load varied temporally according to the am...

Knowledge of wetland hydrology and quantification of water inputs and outputs are Prerequisites to understanding wetland environments and determining their vulnerability to change. To get a better understanding of the dynamics of wetland change in the Usangu Plains, a study was conducted to: a) investigate the effects of human interventions on the wetlands, and b) determine the amount of dry season inflow required to maintain environmental flows downstream of the wetlands. The study integrated hydrologic data, remote sensing and GIS techniques to study the dynamics and spatial response of the wetlands. A monthly water balance model was developed for the wetlands to determine the major components of the water budget. The results of the analyses indicate that the wetlands have changed appreciably in size over recent years and the inflow volumes have decreased with time as a result of increased human interventions. The dry season vegetated swamp cover, a major component of the swamp, d...

In the last decade there has been an increasing awareness of the importance of channel morphology in the healthy functioning of Australian rivers. However, the relationship between channel morphology and the flow and sediment regime of a river is often poorly understood. As a result, within-channel features such as bars, banks and benches are often considered static. Benches are an actively accreting fine-grained bankattached feature within the river channel which contribute a significant store of suspended-grained sediment and have been identified as ecologically important. As managers design and release environmental flows, they need to know how much these flows will modify benches. Benches are a characteristic feature of Australian rivers, and this paper describes initial findings of a field study of the relationship between flow, sediment transport, and bench morphology in the mostly unregulated Ovens River, and highly regulated River Murray, southeastern Australia. We discuss t...

Environmental flow requirements for the Rusape River, a tributary of the Save River, in Zimbabwe, were estimated using a rapid results approach. Thirty years of hydrological data with daily time steps from gauging stations upstream and downstream of the Rusape Dam were analysed using DRIFT Software. The dam appeared to have caused an increase in intra-annual and inter-annual flood events downstream compared to upstream, including significant dry season releases, while inter-annual floods were larger. The water releases from the dam differ from the natural flow in both volume and frequency, especially in the dry season and may have had a negative impact on the local ecosystem and subsistence farmers.The building block method (BMM) was applied, using the hydrological analyses performed, in order to estimate environmental flow requirements, which are presented in mean monthly flows. The flow regime that is recommended for the Rusape River should reduce or reverse these impacts, whilst ensuring sufficient water resources are released for economic needs. The EFR proposed can be achieved within mean monthly flows observed. However, it should be stressed that the EFR proposed have been developed from a rapid method, and are only a first estimate of the EFR for the Rusape River. This study represents a step in developing a management plan for the Save Basin, shared between Zimbabwe and Mozambique.

The establishment of environmental flows and the management of flood releases from existing dams is a complicated process involving numerous stakeholders. Whilst the benefits of environmental flows have been demonstrated in many parts of the world, there is much less experience with managed flood releases from reservoirs. In this paper, we will present the experience of a WWF sponsored project

The populist view of economic development and the environment is that advances in one will necessarily result in a decline in the other. Evidence in the Australian context is that the dual goals can be achieved simultaneously. As economic development progresses, the increasing levels of income stimulate greater demand for environmental improvements. The population engages in more environmentally focused consumption and calls for its governments to introduce more policies designed to rehabilitate and protect environmental assets. Concurrently, the increasing levels of wealth allow for increasing expenditure on research and development into production processes that generate greater productivity and less environmental damage. The Australian agricultural sector provides numerous examples of concurrent improvements in productivity and environmental condition. Zero tillage broad acre grain cultivation practices have led to lower rates of soil erosion and have enriched soil biota while de...

Australia’s largest river system, the Murray-Darling Basin, is the focus of scientific and political attention, due mainly to the competing issues of economic productivity versus environmental flows. Central to this dialogue is the need to know about the Basin’s natural condition and the degree to which the system has deviated from this pre-disturbance, baseline status. This study examines the patterns of ecological change in Lake Cullulleraine, a permanently connected artificial wetland adjacent to Lock Nine on the Murray River, south-east Australia. A 43-cm sediment core was collected in January 1998 and diatoms were analysed at 1-cm intervals for use as aquatic ecological indicators. The sediment core was dated using 210Pb. Changes in the diatom community have occurred since the time of lake formation in 1926, particularly shifts between Aulacoseira subborealis, Staurosira construens var. venter, Aulacoseira granulata, Staurosirella pinnata and Pseudostaurosira brevistriata. An electrical conductivity (EC) transfer function was applied to the fossil diatom assemblages and inferred EC values were compared to long-term, historical EC data from the River. Despite the presence of good analogues between fossil and modern diatom assemblages, inferred EC did not reflect measured EC accurately. In recent decades, patterns in the two data sets were reversed. Despite clear changes in the fossil record, quantitative palaeo-environmental interpretation was limited because the dominant taxa occupy broad ecological niches. Despite these limitations, changes in the Lake Cullulleraine record, particularly in the planktonic taxa, can be interpreted in terms of landscape change. Furthermore, because of the good chronology from the site, the record may be useful for dating changes observed in sites with poor chronological control.

Management of scarce water resources through the use of environmental flows, particularly in developing countries in data-poor arid areas, raises many scientific challenges. These include transforming hydrological data into an ecologically relevant format, providing quantified predictions of river responses to flow change, describing the impacts of river change on common-property users of the rivers, providing the information in a format