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Abstract: The aim of this study was to evaluate four metrics to define the spatially variable (regionalised) hillslope sediment delivery ratio (HSDR). A catchment model that accounted for gully and streambank erosion and floodplain deposition was used to isolate the effects of hillslope gross erosion and hillslope delivery from other landscape processes. The analysis was carried out at the subcatchment (~40km2) and the cell scale (400m2) in the Avon-Richardson catchment (3300km2), south-east Australia. The four landscape metrics selected for the study were based on sediment travel time, sediment transport capacity, flux connectivity, and residence time. Model configurations with spatially-constant or regionalised HSDR were calibrated against sediment yield measured at five gauging stations. The impact of using regionalised HSDR was evaluated in terms of improved model performance against measured sediment yields in a nested monitoring network, the complexity and data requirements of the metric, and the resulting spatial relationship between hillslope erosion and landscape factors in the catchment and along hillslope transects. The introduction of a regionalised HSDR generally improved model predictions of specific sediment yields at the subcatchment scale, increasing model efficiency from 0.48 to >0.6 in the best cases. However, the introduction of regionalised HSDR metrics at the cell scale did not improve model performance. The flux connectivity was the most promising metric because it showed the largest improvement in predicting specific sediment yields, was easy to implement, was scale-independent and its formulation was consistent with sedimentological connectivity concepts. These properties make the flux connectivity metric preferable for applications to catchments where climatic conditions can be considered homogeneous, i.e. in small-medium sized basins (up to approximately 3000km2 for Australian conditions, with the Avon-Richardson catchment being at the upper boundary). The residence time metric improved model assessment of sediment yields and enabled accounting for climatic variability on sediment delivery, but at the cost of greater complexity and data requirements; this metric might be more suitable for application in catchments with important climatic gradients, i.e. large basins and at the regional scale. The application of a regionalised HSDR metric did not increase data or computational requirements substantially, and is recommended to improve assessment of hillslope erosion in empirical, semi-lumped erosion modelling applications. However, more research is needed to assess the quality of spatial patterns of erosion depicted by the different landscape metrics. [Copyright &y& Elsevier]

Abstract: A catchment-scale framework was developed to assess the contribution of sediment sources from farm management actions, gully and streambank erosion on the suspended sediment loads delivered to rivers and associated wetlands and floodplains for two catchments (Avon Richardson, 2885 km2 and Avoca, 4550 km2) in Victoria, south-eastern Australia. After considering commonly available data sets, outputs from the point-scale model (HowLeaky2008) were coupled to a catchment scale framework (CatchMODS). Spatially constant, linear scaling factors were used to link point-scale water surplus to streamflow and gross soil loss to hillslope erosion. The model was calibrated against discharge and suspended sediment loads estimated at water quality monitoring gauging stations. Following calibration, estimates of annual and monthly streamflow and 10-year average annual sediment loads were in good agreement with observations. Catchment-scale outputs, particularly sediment loads, were sensitive to scaling factors. The high sensitivity coupled with limited data hindered tight identification of sediment scaling parameters, therefore sediment outputs were uncertain, particularly in the Avoca catchment. Propagation of uncertainty in parameter estimation to model estimates was assessed qualitatively. The boundaries of model estimations were assessed by retaining predictions of behavioural parameter sets, defined as parameter sets that resulted in efficiencies of sediment load and specific sediment yield estimations not more than 5% lower than the efficiency of the optimal parameter set. Under current management conditions, mean annual suspended sediment load at the Avon-Richardson catchment outlet was estimated to be 3350 (3300–3700) t y−1, of which hillslope erosion contributed 65% (60–80%) and gully erosion 35% (20–40%). In the Avoca catchment, annual suspended sediment load was estimated to be 4000 (3500–5100) t y−1, of which hillslope erosion contributed 17% (5–24%), gully erosion 72% (55–93%), and streambank erosion 11% (1–21%). In the Avon-Richardson catchment management scenarios showed that alternative farming systems focussed on retaining vegetation cover throughout the year would yield a 50 per cent reduction of suspended sediment load, estimated at 1700 t y−1. In contrast, fencing and revegetation of connected gullies was estimated to yield the largest reduction in suspended sediment load (1770 t y−1, 44% of current load) in the Avoca catchment. The framework provides an improved tool to make more informed decisions about how much suspended sediment loads can be reduced in response to farm management actions, gully and streambank protection. Its primary strength lies in the ability to propagate farm management impacts to the catchment scale. Other valuable features for use by natural resource management agencies include a high level of transparency, availability of user-friendly interfaces, and a modular structure that provides flexibility and adaptability to new systems. [Copyright &y& Elsevier]

• In EU nutrient pollution harms aquatic ecosystems condition and their services. • Current nutrient load to European seas is 3.3–4.1 TgN/y and 0.26–0.30 TgP/y. • EU policy measures could decrease the nutrient export to the seas −14% N and −20% P. • Widening the nutrient imbalance in coastal ecosystems, affecting eutrophication. • Further nutrient reductions could be possible by a combination of measures. Intensive agriculture and densely populated areas represent major sources of nutrient pollution for European inland and coastal waters, altering the aquatic ecosystems and affecting their capacity to provide ecosystem services and support economic activities. Ambitious water policies are in place in the European Union (EU) for protecting and restoring aquatic ecosystems under the Water Framework Directive and the Marine Strategy Framework Directive. This research quantified the current pressures of point and diffuse nitrogen and phosphorus emissions to European fresh and coastal waters (2005–2012), and analysed the effects of three policy scenarios of nutrient reduction: 1) the application of measures currently planned in the Rural Development Programmes and under the Urban Waste Water Treatment Directive (UWWTD); 2) the full implementation of the UWWTD and the absence of derogations in the Nitrates Directive; 3) high reduction of nutrient, using best technologies in wastewaters treatment and optimal fertilisation in agriculture. The results of the study show that for the period 2005–2012, the nitrogen load to European seas was 3.3–4.1 TgN/y and the phosphorus load was 0.26–0.30 TgP/y. Policy measures supporting technological improvements (third scenario) could decrease the nutrient export to the seas up to 14% for nitrogen and 20% for phosphorus, improving the ecological status of rivers and lakes, but widening the nutrient imbalance in coastal ecosystems (i.e. increasing nitrogen availability with respect to phosphorus), affecting eutrophication. Further nutrient reductions could be possible by a combination of measures especially in the agricultural sector. However, without tackling current agricultural production and consumption system, the reduction might not be sufficient for achieving the goals of EU water policy in some regions. The study analysed the expected changes and the source contribution in different European regional seas, and highlights the advantages of addressing the land-sea dynamics, checking the coherence of measures taken under different policies. [ABSTRACT FROM AUTHOR]

Abstract: Knowledge of erosion rates and sediment yields from gullies is critical for the effective prioritisation of management efforts aimed at reducing the impact of gully-derived sediments on water quality. This paper describes a rapid assessment method for estimating sidewall gully erosion rates for already established gully networks. It combines a conceptual-empirical model of the cycle of gully initiation and stabilisation with an easy-to-apply technique for assessing gully extent and dimensions. The method is illustrated using a case study of the Avon-Richardson Catchment of north-central Victoria, Australia. It is estimated that a total of 4.6×106 tonnes of sediment have been generated in that catchment from gully erosion since the latest major phase of gullying in the mid 1800s. This is equivalent to 8.9tha−1 y−1 if sediment generation was evenly distributed spatially and temporally across the 3300km2 catchment over 160years prior to 2010. Current rates of gully erosion are estimated to be 4700ty−1 (equivalent to 1.4tha−1 y−1). The results are comparable with observed rates of sidewall erosion in the Avon-Richardson Catchment. Further testing is required to build confidence in its applicability to assess sediment yields and for assisting regional authorities to plan remediation efforts. [Copyright &y& Elsevier]

We review several papers that have afforded insights into determinants of positive outcomes (e.g. the adoption of tools, improved learning and/or collaboration) from modelling projects. From a subsequent internet search in the environmental domain we identified 33 such factors that are then invoked in a transferable survey-based method to facilitate structured reflections by model developers on 15 projects. Four factors were considered most necessary to realize overall success for any modelling project. Three factors related to aspects of stakeholder engagement in the modelling process; the other to critical thinking around problem framing and the role(s) of models. The latter factor was considered reasonably well-achieved across the projects. Harder to control were the stakeholder engagement factors which, along with project management considerations, can constrain or enable achievement of other factors. The paper provides further evidence of the critical need to consider non-technical aspects in the design and implementation of modelling projects. [ABSTRACT FROM AUTHOR]