Multidimensional Aspects of Sustainable Biofuel Feedstock Production

Bioenergy is becoming increasingly relevant as an alternative to fossil fuels. Various bioenergy feedstocks are suggested as environmentally friendly solutions due to their positive impact on stream health and ability to sequester carbon, but most evaluations for bioenergy feedstocks have not evaluated the implications of bioenergy crop production holistically to date. Through the application of multi-objective optimization on 10 bioenergy feedstock rotations in a Michigan watershed, a Pareto front is searched to identify optimal trade-off solutions for three objective functions representing stream health, environmental emissions/carbon footprint, and economic feasibility. Various multi-criteria decision-making techniques are then applied to the resulting Pareto front to select a set of most-preferred trade-off solutions, which are compared to optimal solutions from each individual objective function. The most-preferred trade-off solutions indicate that a diverse mix of rotations are necessary to optimize all three objectives, whereas the individually optimal solutions do not consider a diverse range of feedstocks, thereby making the proposed multi-objective treatment an important and pragmatic strategy.

Stream Health Estimation for the Plum Creek Watershed

Overall health of a stream is one of the powerful indicators for planning mitigation strategies. Currently, available methods to estimate stream health do not look at all the different components of stream health. Based on the statistical parameters obtained from daily streamflow data, water quality data, and index of biotic integrity (IBI), this study evaluated the impacts on all the elements of stream health, such as aquatic species, riparian vegetation, benthic macro-invertebrates, and channel degradation for the Plum Creek watershed in Texas, USA. The method involved the (1) collection of flow data at the watershed outlet; (2) identification of hydrologic change in the streamflow; (3) estimation of hydrologic indicators using NATional Hydrologic Assessment Tool (NATHAT) before alteration and after alteration periods; (4) identification of the most relevant indicators affecting stream health in the watershed based on stream type; (5) preliminary estimation of the existence of stream health using flow duration curves (FDCs); (6) the use of stream health-relevant hydrologic indices with the scoring system of the Dundee Hydrologic Regime Assessment Method (DHRAM). The FDCs plotted together for before and after the alteration periods indicated the likely presence of a stream health problem in the Plum Creek. The NATHAT–DHRAM method showed a likely moderate impact on the health of Plum Creek. The biological assessments carried out, the water quality data monitored, and the land cover during pre- and post-alteration periods documented in a publicly available federal document support the stream health results obtained from this study.

Understanding the sources and transit times of water contributing streamflow from intermittent headwater catchments in semi-arid areas

<p>Intermittent headwater catchments constitute a significant proportion of many stream networks. In semi-arid climates, intermittent headwater streams flow only following periods of sustained rainfall. There is commonly a rapid response of streamflow to rainfall; however, whether this is the input of recent rainfall or displacement of water stored in the catchments for several years is not well known. Understanding the sources and transit times of water that contribute to streamflow is important for the maintenance of stream health and predicting the response of land-use changes.</p><p>The study focuses on two intermittent streams from two contrasting land-use (pasture and forest) in southeast Australia. The native eucalyptus forests in this region were originally cleared for grazing following European settlement <sup>~</sup>180 years ago and then partially replaced by plantation in the last <sup>~</sup>15 years. Stream water and groundwater from the riparian zone adjacent to the streams were sampled between May and October 2018.</p><p>The stream water has <sup>3</sup>H activities of 1.30 to 3.17 TU in the pasture and 1.84 to 3.99 TU in the forest, with higher activities recorded during the higher winter flows. Groundwater from the riparian zone has <sup>3</sup>H activities of 0.16 to 0.79 TU in the pasture and 2.01 to 4.10 TU in the forest. Aside from one riparian zone groundwater sample, all <sup>3</sup>H activities of groundwater in the riparian zone are lower than those of recent local rainfall (<sup>~</sup>2.79 TU). The single high <sup>3</sup>H activity in riparian zone possibly reflects recharge by winter rainfall with higher <sup>3</sup>H activities.</p><p>The mean transit times (MTTs) of water were estimated using a range of tracer lumped parameter models. The riparian zone groundwater has greater MTTs of hundreds of years in the pasture and up to 9 years in the forest. At high streamflow, the stream water has MTTs of <6 years in the pasture and the forest. The MTTs of stream water at low streamflow vary from 15 to 42 years in the pasture and from 3 to 16 years in the forest. The long MTTs of water from streams indicate that the source water is not just recent rainfall, rather water stored in the riparian zone is mobilised at the commencement of flow and recent rainfall makes a larger contribution at higher flows. The observation is consistent with the major ion geochemistry of the stream water, which most closely represents that of the riparian zone groundwater. The differences in MTTs of stream water between two contrasting land-use imply that the streamflow has been being most likely impacted by land-use changes. Thus, it is necessary to improve the strategies for catchment management to protect stream health from land-use practices.</p>