Sara Beavis

Relating stream-bank erosion to in-stream transport of suspended sediment

We seek an improved and quantitative understanding of the sources and transport of sediment and attached phosphorus in upland catchments and downstream reaches of the Namoi River in New South Wales, Australia. Study of the sources of phosphorus and related sediment was motivated by severe problems with blooms of blue-green algae and toxic by-products in the Darling and Namoi Rivers. Using atmospheric fall-out of radionuclides as tracers, Olley et al. (1996) concluded that much of the sediment deposited in the lower reaches came from subsoil rather than topsoil. With this insight, we focus on quantifying sediment sources from stream bank erosion, especially in seasonally erosional reaches of Coxs Creek and the Mooki River. The approach presented here integrates interdecadal aerial photography, interseasonal field measurements of bank erosion processes, continuous monitoring of stream flow and turbidity and event sampling of suspended solids and phosphorus, with an analytical model of in-stream suspended sediment transport. We compare a lateral source term in the calibrated transport model with field-based and aerial measurements of stream bank erosion. Calibration of the in-stream model is illustrated for two reaches of the Mooki River, with the changes in parameter values being related to aspects of the hydraulic geometry and particle size. The processes of stream flow and bank erosion due to undercutting, desiccation, block failure and mass wasting of aggregated particles interact to produce instream fluxes of suspended sediment that are transported and redeposited downstream. The combined approach demonstrated here has potential for predictive spatial modelling of sediment concentrations and loads. Copyright

Modelling upland and instream erosion, sediment and phosphorus transport in a large catchment

This overview presents background information to place the subsequent papers by Beavis et al., Dietrich et al. and Green et al. in the context of a unified approach. The modelling framework described here consists of two major components: an upland catchment model and an instream sediment transport model. The upland model simulates stream flow (Q), suspended sediment (SS) and associated phosphorus (P) using rainfall data, and is calibrated to daily stream flow time-series under historical conditions. The instream model routes SS and attached P from the outlet of upland catchments to gauging points downstream. The instream transport model can infer sources (resuspension and bank erosion) and sinks (deposition) within a reach. Aerial photographs are used to assess the on-site effects of climate and land cover/use on erosion and the drainage network. Changes in land cover/use and the effects on the drainage network are related to the parameters in the rainfall-runoff model so that associated effects on Q (and hence SS and P) can be assessed. This modelling framework is prototyped on the Namoi Basin in northern New South Wales, Australia, and is described briefly herein.

Structural controls on the orientation of erosion gullies in mid-western New South Wales, Australia

Abstract The role of geology in determining the drainage network of gullying has been evaluated by quantitative methods of analysis. At gully erosion sites in New South Wales, field evidence suggests that soil cracks are sites of preferential flow and erosion at both the surface and subsurface. Soil fabric and rock structure and weathering studies were undertaken to establish the inheritance of soil cracks from the underlying parent material. Gully orientation was correlated with the strike of joints and bedding planes in a range of rock materials, including sedimentary, intrusive and extrusive igneous, and thermal and regional metamorphic rocks. These units vary not only in terms of mineralogy but also in degree of weathering. However, all are steeply dipping structures (usually exceeding 60°). Correlations exist between gully orientation and joints in the underlying material, but the strength of the relationship varies according to the parent material. In the Ordovician hornfels, where no correlation between joints and gully orientation occurred, the evidence showed that gullying was controlled by faulting along the hornfels–granite boundary. These relationships support the view that throughflow processes are dominant in the development of gullies, since convergence of runoff would not be expected to align with subsurface soil discontinuities.

Erosional history of the Warrah Catchment in the Liverpool Plains, New South Wales

Since European settlement, considerable changes in land cover and land management have occurred in the Liverpool Plains as a response to agricultural expansion and development. As a consequence, erosion gullies have been initiated and subsequently have developed into extensive networks. Streams, erosion gully networks, rills, land cover and land management have been mapped and digitized on to a GIS using a number of aerial photographic time-slices. Information derived from the GIS-generated maps includes: (a) measurement of temporal and spatial changes in the fluvial and gully networks, and land use and land management practices; and (b) assessment of changes in the connectivity of gullies to streams. It has been shown that revegetation and erosion control works decreased the density of erosion gullies from 1943 to 1994. Copyright

Tracking multiple modes of endocrine activity in Australia's largest inland sewage treatment plant and effluent‐ receiving environment using a panel of in vitro bioassays

Estrogenicity of sewage effluents, and related ecotoxicological effects in effluent-receiving environments, have been widely reported over the last 2 decades. However, relatively little attention has been given to other endocrine pathways that may be similarly disrupted by a growing list of contaminants of concern. Furthermore, the Australian evidence base is limited compared with those of Europe and North America. During a low dilution period in summer, the authors investigated multiple endocrine potencies in Australias largest inland sewage treatment plant (STP) and the Lower Molonglo/Upper Murrumbidgee effluent-receiving environment. This STP receives 900 L/s of mostly domestic wastewater from a population of 350 000, and contributes a high proportion of total flow in the lower catchment during dry periods. A panel of in vitro receptor-driven transactivation assays were used to detect (anti)estrogenic, (anti) androgenic, (anti)progestagenic, glucocorticoid, and peroxisome-proliferator activity at various stages of the sewage treatment process. Total estrogenic and (anti)androgenic potency was removed after primary and/or secondary treatment; however, total removal efficiency for glucocorticoid potency was poorer (53-66%), and progestagenic potency was found to increase along the treatment train. Estrogenicity was detected in surface waters and bed sediments upstream and downstream of the effluent outfall, at maximum levels 10 times lower than low-hazard thresholds. Glucocorticoid and progestagenic activity were found to persist to 4 km downstream of the effluent outfall, suggesting that future research is needed on these endocrine-disrupting chemical categories in effluent-receiving systems.

Development of a spatial database for large-scale catchment management: Geology, soils, and landuse in the Namoi Basin, Australia

Abstract The ArcInfo Geographical Information System (GIS) was used to develop spatial databases for recording spatial data. The databases developed in this study provide a graphic and mapping display interface to assist the management of the Namoi Basin in New South Wales, Australia. In addition, the databases are used in the investigation of the impacts of spatio-temporal changes in landuse/management on hydrologic processes from catchment to basin scales. Climate, stream flow, and water quality data are being incorporated into the ArcInfo dataset to drive and test hydrologic models.

The cost of collaboration: how Caring for Our Country has shaped regional Natural Resource Management in an Australian river catchment

Funding arrangements for Natural Resource Management (NRM) in Australia have undergone a number of changes in the last decade, including the transition from the Natural Heritage Trust (NHT) to the Caring for Our Country (CfoC) program (recently merged with Landcare to become the National Landcare Programme). It has been suggested that CfoC eroded some of the gains in regional autonomy, community engagement and goodwill made under the NHT. This article presents the results of research conducted with regional NRM bodies and community-based stakeholders in the Upper Murrumbidgee catchment, south-eastern Australia. It explores the impacts of the CfoC grants structure on NRM bodies and communities, and examines the practical responses of resource managers to funding constraints. The research demonstrates that the structure of NRM funding delivery under CfoC played a key role in shaping the strategic and operational activities of regional NRM bodies and community groups. In particular, the short-term, single-issue focus of the program placed pressure on collaborations between regional NRM bodies and other groups, and could inhibit strategic and integrated approaches to NRM. At the same time, however, NRM planners and community stakeholders have actively managed the limitations of the CfoC structure to optimise catchment outcomes for communities and the environment.

Rainwater harvesting augmentation of domestic water supply in Honiara, Solomon Islands

Abstract Secure and sanitary water supply is essential for human health and well-being. The challenges in meeting this demand are great in Small Island Developing States where water resources may be limited due to social and environmental constraints. In Honiara, Solomon Islands, a number of factors have constrained access to fresh water including: rapid population growth and urbanisation; neglected water infrastructure; the ethnic tensions; water tariff increases of 170% in the past 3 years; sole reliance on groundwater; and poor supporting electrical infrastructure. Within this context, the case for using rainwater tanks as either a predominant source or for augmentation of existing domestic water supply has been explored. The effect of historical drought events on rainwater tanks has been examined. A water balance model has been developed and various household scenarios reviewed to determine the reliability of domestic rainwater tanks over a 28-year period. The development of this model has highlighted both opportunities and limitations in Honiara that can be used to inform decision-makers and planners in water resources management.

Salinisation processes in a sub-catchment of Wybong Creek, Hunter Valley, Australia

Salinisation in the Hunter Valley, New South Wales, Australia, is a significant environmental issue which affects the regional wine, horse and beef industries. The sub-catchment of Wybong Creek causes increased salinity, sodicity and chlorine concentrations in the Hunter River. Sampling was undertaken in the scalded area of Manobalai, located in the mid-catchment area of Wybong Creek, to establish whether salt stores within the regolith, or saline groundwater discharge from deeper formations, are sources of Na+ and Cl− dominated water to Wybong Creek. Ten soil cores were collected from eight sites in the Manobalai area, with bores and piezometers installed to characterise groundwater chemistry and hydraulic head. The regolith within the Manobalai field site was non-saline, though Na+ and Cl− were the dominant ions in most regolith layers. The most saline regolith samples have coarse textures and a high moisture content, and occur in the valley floor. Cores from the salt scald have salt concentrations ranging from 274 to 2089 mg/kg, with a maximum Na+ and Cl− wt.% of 0.17. Saline groundwater in piezometers has total dissolved solid concentrations of up to 7277 mg/L. In this saline groundwater, Cl−/Br− ratios of up to 1767, Na+/Cl− ratios of 0.6–1.2 and 87Sr/86Sr ratios up to 0.709446 indicate halite dissolution and a marine source of solutes to groundwater. The Wittingham Coal Measures, which previous studies have linked to salinity elsewhere in the Hunter Valley, contain halite efflorescences and were intruded by marine water in their geological past. Salinity is due to discharge of this regional groundwater body in the Wybong catchment and not, as commonly assumed within Australia, due to dryland salinity.

The relationship between climate and streamflow in the Namoi basin

Abstract The Namoi River Basin (42 000 km 2 ) is located in the Murray-Darling Basin, west of the Great Australian Dividing Range in northeast New South Wales (NSW), and includes some of the most fertile agricultural lands in Australia. One of the environmental concerns for this basin is erosion and its effects on downstream water quality. Models that relate climate, land use, and these concerns require measurements of climate (rainfall and temperature) and streamflow. These measurements were examined as a preliminary to the modelling. The residual mass technique was used to examine the temporal variation of annual rainfalls over the approximately 100 years of available data, and significant spatial variations were found in annual rainfall trends over the catchment. Streamflow was examined at key river gauging stations. The impact of recent large-scale irrigation operations was clearly observed. The impact of changing land use and land management on runoff ratios was examined for eight subcatchments. Temperature variations were examined for the four major towns in the catchment. The duration of the temperature data is too short to make any comments about long-term trends. Significant variations were observed in an east to west direction.