Determination of dissolved organic matter in streamwater using visible spectrophotometry: A comment

A discussion querying the need (Grieve, 1985) for further studies on the use of the technique, which is already well established. The use of chemical oxygen demand is also questioned.     

A procedure of selection of meteors from major streams for determination of mean orbits

A procedure of selection of meteoroids from major streams is suggested and applied to the IAU Lund photographic database modified by a check for internal consistency among orbital elements (3411 orbits). Limits for choice of stream members were defined by break points on the plots of the cumulative numberN _C vs. the Southworth-HawkinsD discriminant. For the break points were considered the points from which the dependenceN _C vs.D changes to a quasi-linear one, and with the increasingD, N _C changes only moderately. Except for the Taurids which desire a separate analysis, theN _C vs.D diagrams are presented for the following major meteoroid streams: Quadrantids, Lyrids, Aquarids, Capricornids, N and S Aquarids, Perseids, Orionids, Leonids and Geminids. The mean orbits, velocities and radiants of the streams are derived and compared with the osculating orbits of their parent bodies. The limitingD _B was found to be a function of the number of the stream membersN _CB. Omitting the exceptionally concentrated Geminids, the relation is in the formD _B = 0.058 *ln(N _CB) – 0.04.     

Effect of upstream ponds on stream temperature

Many tributaries feeding streams are connected to ponds that heat up during summer months; however, the influence of these ponds on receiving stream temperature was not known. Stream temperature affects microfauna and fish habitats in aquatic ecosystems. Three tributaries with headwater ponds exposed to sunlight and one tributary unassociated with a large, upstream pond were selected for study within the Pennypack Creek watershed in the Philadelphia Metropolitan Area. Temperature loggers were installed in the pond (when applicable), associated tributary, and in the Pennypack Creek up and downstream of its confluence with the tributary. Although diurnal temperature fluctuations were apparent, the study showed no significant differences in temperature up and downstream of tributary discharge to Pennypack Creek. Pond water temperatures were up to 4°C warmer than the Pennypack Creek; however, temperatures downstream and upstream of the tributaries leading out of the ponds were within 1°C of each other.     

Predicting the ecological status of rivers and streams under different climatic and socioeconomic scenarios using Bayesian Belief Networks

Freshwater systems have increasingly been subjected to a multitude of human pressures and the re-establishment of their ecological integrity is currently a major worldwide challenge. Expected future climate and socioeconomic changes will most probably further exacerbate such challenges. Modelling techniques may provide useful tools to help facing these demands, but their use is still limited within ecological quality assessment of water resources due to its technical complexity.We developed a Bayesian Belief Network (BBN) framework for modelling the ecological quality of rivers and streams in two European river basins located in two distinct European climatic regions: the Odense Fjord basin (Denmark) and the Sorraia basin (Portugal). This method enabled us to integrate different data sources into a single framework to model the effect of multiple stressors on several biological indicators of river water quality and, subsequently, on their ecological status. The BBN provided a simple interactive user interface with which we simulated combined climate and socioeconomic changes scenarios to assess their impacts on river ecological status.According to the resulting BBNs the scenarios demonstrated small impacts of climate and socioeconomic changes on the biological quality elements analysed. This yield a final ecological status similar to the baseline in the Odense case, and slightly worse in Sorraia. Since the present situation already depicts a high percentage of rivers and streams with moderate or worse ecological status in both basins, this means that many of them would not fulfil the Water Framework Directive target in the future. Results also showed that macrophytes and fish indices were mainly responsible for a non-desirable overall ecological status in Odense and Sorraia, respectively. The approach followed in this study is novel, since BBN modelling is used for the first time for assessing the ecological status of rivers and streams under future scenarios, using an ensemble of biological quality elements. An important advantage of this tool is that it may easily be updated with new knowledge on the nature of relationships already established in the BBN or even by introducing new causal links. By encompassing two case studies of very different characteristics, these BBN may be more easily adapted as decision-making tools for water management of other river basins.     

Remote sensing of stream depths with hydraulically assisted bathymetry (HAB) models

This article introduces a technique for using a combination of remote sensing imagery and open-channel flow principles to estimate depths for each pixel in an imaged river. This technique, which we term hydraulically assisted bathymetry (HAB), uses a combination of local stream gage information on discharge, image brightness data, and Manning-based estimates of stream resistance to calculate water depth. The HAB technique does not require ground-truth depth information at the time of flight. HAB can be accomplished with multispectral or hyperspectral data, and therefore can be applied over entire watersheds using standard high spatial resolution satellite or aerial images. HAB also has the potential to be applied retroactively to historic imagery, allowing researchers to map temporal changes in depth.We present two versions of the technique, HAB-1 and HAB-2. HAB-1 is based primarily on the geometry, discharge and velocity relationships of river channels. Manning's equation (assuming average depth approximates the hydraulic radius), the discharge equation, and the assumption that the frequency distribution of depths within a cross-section approximates that of a triangle are combined with discharge data from a local station, width measurements from imagery, and slope measurements from maps to estimate minimum, average and maximum depths at a multiple cross-sections. These depths are assigned to pixels of maximum, average, and minimum brightness within the cross-sections to develop a brightness–depth relation to estimate depths throughout the remainder of the river.HAB-2 is similar to HAB-1 in operation, but the assumption that the distribution of depths approximates that of a triangle is replaced by an optical Beer–Lambert law of light absorbance. In this case, the flow equations and the optical equations are used to iteratively scale the river pixel values until their depths produce a discharge that matches that of a nearby gage.R² values for measured depths versus depths estimated by HAB-1 and HAB-2 are 0.51 and 0.77, respectively, in the relatively simple Brazos River, Texas. R² values for HAB-1 and HAB-2 are 0.46 and 0.26, respectively, in the Lamar River, a complex mountain river system in Yellowstone National Park. Although the R² values are moderate, depth maps and cross-sections derived from the HAB techniques are consistent with typical stream geomorphology patterns and provide far greater spatial coverage and detail than could be achieved with ground-based survey techniques. Improved depth estimates can be achieved by stratifying the river into different habitat types that normalize for differences in turbulence and substrate.     

Mobile policies and policy streams: The case of smart metering policy in Australia

Geographers have become increasingly engaged with the notion of policy mobility. It is argued that in a globalised world policies have become more internationally mobile: we now live in an era of ‘fast policy’. Drawing on core concepts of mobility, neoliberalisation, and globalisation - and with a background primarily in geography and urban studies - policy mobility scholars have developed new ideas about how policies circulate internationally. In the process, however, theories of policy change developed within political science have been rather overlooked. In this paper it is shown how a political science theory with a shared interest in flows – the Multiple Streams Approach (MSA) – is complementary to policy mobilities scholarship. Two issues in particular are illuminated by the MSA: first, what constitutes policy, and, second, the role of the nation state in structuring the possibilities for, and timing of, policy change. In turn, policy mobilities scholarship highlights the different geographies of the multitude of objects, ideas, problems, processes, organisations, and regulations that constitute policy. It also raises questions about the validity of analytically separating politics from policy proposals, as advocated by the MSA. These issues are considered using the empirical case of smart electricity metering policy in Australia, in the period 2000–2015.     

On separation of major meteoroid streams from the sporadic background

The paper deals with a search for chosen photographic meteoroid streams compiled from the IAU Meteor Data Center Lund catalogue from which less than 2% of the orbits had to be removed due to internal inconsistency among the orbit parameters. Additional 35 orbits were removed due to extremely high hyperbolic velocities. The final set consists of 3411 orbits. Members of the Quadrantids, Lyrids, Perseids and Geminids were searched for, firstly, by a stream-search procedure utilizing the Southworth-HawkinsD-criterion. This choice, as a rule, represents the most abundant filament of the stream. Secondly, rate distribution histograms ofD were divided into region of shower meteors and region of sporadic background meteors. The searched database with a relatively low abundance of sporadic meteors in the analyzed periods simplified this choice, and followingly, fitting the obtained values by means of power and exponential functions, the limitingD _s for particular showers were derived. The derivedD _s appears as the optimum value, as for higherD, the number of sporadic meteors included in the stream sample increases more rapidly than the number of additional shower meteors, and for smallerD, the number of shower meteors decreases quicker than the number of omitted sporadic meteors. The following counts of shower meteorsN and limitingD _s were found: Quadrantids (39, 0.22), Lyrids (11, 0.15), Perseids (595, 0.53) and Geminids (224, 0.32). Efficiency of the procedure was tested comparing the number of sporadic meteors in the region of radiant area and the neighbouring regions of the same size.