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In the face of mounting environmental and political challenges in river management, accurate and timely scientific information is required to inform policy development and guide effective management of waterways. The Murray–Darling Basin is Australia's largest river system by area and is the subject of a heavily contested series of water reforms relying comprehensively on river science. River scientists have specialised knowledge that is an important input into evidence‐based decision‐making for the management of the Murray–Darling Basin, but despite extensive literature on the interface between science and policy, there is little guidance on achieving policy relevance for practicing scientists. Here, we provide a set of important discussion points for water scientists to consider when engaging with policy‐makers and environmental water managers. We place our considerations in the context of a broader literature discussing the role of natural‐resource scientists engaging with policy and management. We then discuss the different roles for river scientists when engaging in this space, and the advantages and pitfalls of each. We illustrate the breadth of modes of engagement at the science‐policy‐management interface using the Murray–Darling Basin as an example. We emphasise the need for effective governance arrangements and data practices to protect scientists from accusations of operating as advocates when working to inform management and policy.

European settlement has led to increased loads of fine suspended sediment (SS) entering the River Murray, Australia's largest, and arguably, most important river. The River Murray's anthropogenic sediment history can be divided into four periods with varying source areas, sediment loads, and seasonal patterns. The Aboriginal period (before 1840) was characterized by clear water at summer low‐flows in the River Murray and its southern tributaries, with more sediment coming from the northern catchment than the southern, and the Darling River being turbid at all flows. There is little evidence that Aboriginal burning resulted in any measurable increase in SS. SS loads peaked in the 1870s and 1880s (the gold and gully period, 1850–1930) as valley floors were incised by gullies (mostly in northern tributaries), and gold sluicing flushed huge amounts of sludge into southern tributaries. Sedimentation in wetlands and on floodplains increased by 2–10 times in this period, and the biota in wetlands switched from clear water to turbid water communities. In the hiatus period (1930–1960) sediment supply from gullies and gold mining waned and low flow SS concentrations returned to low levels. Dam construction through the 1960s and 1970s (the regulation period, 1960 on) disconnected the River Murray from catchment derived sediment. Despite this, SS levels increased again: now largely derived from instream sources including bank erosion from long duration summer irrigation flows, the spread of bottom‐feeding carp (Cyprinus carpio), and wave erosion from boats. Erosion switched from winter to summer dominated. Significant investment in securing water for the environment in the Murray‐Darling Basin could be complemented by addressing in‐channel sediment sources in the River Murray itself to reduce turbidity. Overall, European era SS concentrations remain relatively low with small sediment delivery to the ocean (0.1 Mt per annum), despite high catchment erosion rates. This i

In this study, climate scenarios (dry, medium and wet) have been used to characterize changing climatic and flow conditions for the period 2050–2054 in the 4th order River Weiße Elster in Germany. Present and future periods of nitrogen turnover were simulated with the WASP5 river water quality model. Results revealed that, for a dry climate scenario, the mean denitrification rate was 71% higher during summer (low flow period between 2050 and 2054) and 51% higher during winter (high flow period) compared to the reference period. In the 42-km study reach, N-retention through denitrification amounted to 5.1% of the upper boundary N load during summer low flow conditions during the reference period. For the future dry climate scenario, this value increased by up to 10.2%. In our case study, the investigated climate scenarios showed that future discharge changes may have a larger impact on denitrification rates than future temperature changes.

Deflation basins, or shallow depressions formed by wind erosion, are found in many semi-arid regions around the world. Because these features are topographic lows they become sites of water accumulation and are often associated with wetlands that represent important refugia for biota in dry environments. Despite being important habitats little is known about the relationship between water and sediment in these features. This study assesses soil geochemical properties from 50 wet-climate and 39 dry-climate deflation basins in Tasmania. The results reveal clear differences between wet-climate and dry-climate deflation basin soils. Macronutrients typically have higher concentrations in wet-climate soils (with the exception of potassium and calcium) while metals and other trace elements typically have higher concentrations in dry-climate soils. These findings have important implications for wetland biological-soil associations, with high plant productivity likely in wet-climate deflation basins as a result of both favourable nutrient status and better water availability.

Wetlands, particularly those in semi-arid or arid environments, are hotspots of biological diversity and productivity. Water resource managers are therefore increasing their efforts to conserve wetlands from environmental degradation. To do this, they require a thorough understanding of the wetting and drying regimes of these wetlands, and how potential land use, climate change and water resource development might affect inundation patterns. Hydrologic models can help to enhance this understanding, and to predict and assess future impacts. However, for semi-arid environments, data to assist in model construction is scarce. This paper presents a new method for developing a water balance model for a semi-arid wetland, the Narran Lakes ecosystem in eastern Australia. This method combines hydraulic (improving our understanding of water movement through a wetland) and hydrologic (improving our predictive capability for inundation levels) models and satellite imagery (acting as calibration and validation data) to produce a predictive model of wetland inundation. We show that this coupled hydraulic-hydrologic model yields inundation patterns commensurate with those that actually occurred over more than 30 years. The model results indicate that current inundation levels are at historical lows, which is most likely associated with a naturally occurring drought and increasing water resource development upstream.

It can be challenging to accurately determine the topography of physically complex landscapes in remote areas. Ground-based surveys can be difficult, time consuming and may miss significant elements of the landscape. This study compares digital elevation models (DEMs) generated from three different data sources, of the physically complex Narran Lakes Ecosystem, a major floodplain wetland ecosystem in Australia. Topographic surfaces were generated from an airborne laser altimetry (LiDAR) survey, a ground-based differential GPS (DGPS) survey containing more than 20,000 points, and the 9? DEM of Australia. The LiDAR- and DGPS-derived data generated a more thorough DEM than the 9? DEM; however, LiDAR generated a surface topography that yielded significantly more detail than the DGPS survey, with no noticeable loss of elevational accuracy. Both the LiDAR- and the DGPS-derived DEMs compute the overall surface area and volume of the largest floodplain lake within the system to within 1% of each other. LiDAR is shown to be a highly accurate and robust technique for acquiring large quantities of topographic data, even in locations that are unsuitable for ground surveying and where the overall landscape is of exceptionally low relief. The results of this study highlight the potential for LiDAR surveys in the accurate determination of the topography of floodplain wetlands. These data can form an important component of water resource management decisions, particularly where environmental water allocations for these important ecosystems need to be determined

In semi-arid environments, dryland wetlands serve as key loci for biological diversity and productivity. This stems from their relative abundance of water and the comparative richness of their soils which are reinvigorated by the delivery of sediment and nutrients during relatively infrequent flood events. Therefore, to fully understand the nature of these environments, it is important to understand the links between the delivery of water and sediment (particularly with respect to varying sediment sources) to semi-arid wetlands and the physical and chemical properties of the surface sediments deposited within them. The purpose of this study was to

A trend in river science over the last 15 years has been the increased emphasis on larger systems. This has been refl ected in an expanding literature base describing the physical character and processes of large rivers. The 1989 special issue of Canadian Journal of Fisheries and Aquatic Sciences was one of the fi rst publications to deal specifi - cally with large river systems. Although papers from this symposium (Dodge, 1989) had a multidisciplinary focus, 11 of the 49 papers dealt with the form and process of large fl oodplain rivers. The geomorphological character of large lowland rivers was presented in Lowland Floodplain Rivers: Geomorphological Perspectives (Carling and Petts, 1992).

In response to the growing interest in developing terahertz imaging systems for concealed weapons detection, the Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has produced full-body terahertz imagery using coherent active radar measurement techniques. The proof-of-principle results were readily obtained utilizing the compact radar range resources at STL. Two contrasting techniques were used to collect the imagery. Both methods made use of in-house transceivers, consisting of two ultra-stable far-infrared lasers, terahertz heterodyne detection systems, and terahertz anechoic chambers. The first technique involved full beam subject illumination with precision azimuth and elevation control to produce high resolution images via two axis Fourier transforms. Imagery collected in this manner is presented at 1.56THz and 350GHz. The second method utilized a focused spot, moved across the target subject in a high speed two dimensional raster pattern created by a large two-axis positioning mirror. The existing 1.56THz compact radar range was modified to project a focused illumination spot on the target subject several meters away, and receive the back-reflected intensity. The process was repeated across two dimensions, and the resultant image was assembled and displayed utilizing minimal on-the-fly processing. Imagery at 1.56THz of human subjects with concealed weapons are presented and discussed for this scan type., The original document contains color images.

Contemporary methods for managing flood plain ecosystems are biased towards temporal patterns of flow. Such approaches disregard the inherent spatial complexity associated with the flooding and drying of flood plain ecosystems and the influence this has on their productivity and biodiversity. This study investigates how the character of inundated patches changes through two flood events in the Narran Lakes ecosystem, Australia. A series of Landsat thematic mapper (TM) images were used to elicit patterns in inundated-patch character over time. Characteristics including patch number, size, shape and proximity to other patches were calculated for each image and subjected to multivariate statistical analyses. Strong positive relationships were observed between patch number; richness of patch area, shape and. proximity and total surface area inundated. Hysteresis was also observed for the latter three relationships. This work highlights the importance of incorporating both spatial and temporal aspects of flood plain inundation in detennining environmental water allocations for flood plain maintenance.

t Flood plain wetland complexes are mosaics of physical units and the sediments contained within these various units often display spatial and temporal complexity. This paper reconstructs the environmental history of a mosaic of geomorphic units within a large terminal flood plainwetland complex in southeastern Australia in order to identify how the sediment character of the mosaic has changed through time. Sediment cores, up to 14 m in depth, were extracted from one flood plain and three lake units. Stratigraphy and multivariate analysis on these cores reveal a complex environmental history with sediment character highly variable in both time and space. All four geomorphic unitslake and flood plainhave undergone a convergent evolution from unique initial states. This study highlights how numerical methods, in association with standard sedimentological techniques, can assist in unravelling the environmental history of a temporally and spatially diverse landscap

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Vegetation zonation patterns are a common feature in flood plain wetland complexes and are important to the biodiversity and functioning of such systems. The purpose of this paper is to identify links between water regime, seed bank and the establishment of zoned vegetation communities in a series of small distributary channels within the Narran Lakes flood plain wetland complex, eastern Australia. Seed bank material from three distinct plant community zones within three distributary channels were collected and subjected to five inundation treatments over a period of 12 weeks to test the effects of location and inundation regime on the abundance of seedlings, species richness and species assemblages. The results of this study indicate that the water regime determines which species germinate and the seed bank influences the abundance of plants to emerge. This study provides insight into the implications of changing flooding regimes on plant community composition in flood plainwetland systems