Effects of wind farm construction on concentrations and fluxes of dissolved organic carbon and suspended sediment from peat catchments at Braes of Doune, central Scotland

This paper assesses the impacts of disturbance associated with the construction of a wind farm on fluxes of dissolved organic carbon (DOC) and suspended sediment from a blanket peat catchment in central Scotland during the period immediately following completion of construction. Six streams draining the site were sampled on six dates from October 2006, when construction was completed, and an additional three control streams to the west of the site were sampled on the same dates. Turbidity and stage were recorded semi-continuously in the two largest streams (one disturbed and one control), which were also sampled during storm events. Absorbance (400 nm) and DOC concentrations were determined on all samples, and suspended sediment was determined on the event samples. Absorbance and DOC were closely correlated in both the disturbed and undisturbed streams, with slightly greater absorbance per unit DOC in the disturbed streams. DOC concentrations in disturbed tributaries were always greater than those in undisturbed streams, with mean differences ranging from 2 to around 5 mg L-1. DOC and stage were positively correlated during events with maximum concentrations in excess of 30 mg L-1 at peak flow. Suspended sediment concentrations were markedly elevated in the disturbed stream with maximum concentrations at peak flow some 4-5 times greater than in the control. The colour of the sediment suggested that it was highly organic in nature at peak flow, and suspended particulate organic carbon represented a further loss of C from the site. Using flow-weighted mean DOC concentrations calculated for the storms monitored in autumn 2007, dissolved carbon losses can be estimated for the catchments of the disturbed and control streams. From these data the additional DOC loss related to disturbance associated with the wind farm is estimated at 5 g m-2

The spatial dynamics of vertical migration by Microcystis aeruginosa in a eutrophic shallow lake: A case study using high spatial resolution time-series airborne remote sensing

Abstract: Time-series airborne remote sensing was used to monitor diurnal changes in the spatial distribution of a bloom of the potentially toxic cyanobacterium Microcystis aeruginosa in the shallow eutrophic waters of Barton Broad, United Kingdom. High spatial resolution images from the Compact Airborne Spectrographic Imager (CASI-2) were acquired over Barton Broad on 29 August 2005 at 09:30 h, 12:00 h, and 16:00 h Greenwich mean time. Semiempirical water-leaving radiance algorithms were derived for the quantification of chlorophyll a (R2 = 0.96) and C-phycocyanin (R2 = 0.95) and applied to the CASI-2 imagery to generate dynamic, spatially resolving maps of the M. aeruginosa bloom. The development of the bloom may have been fostered by a combination of the recent improvements in the ambient light environment of Barton Broad, allied to the acute depletion of bioavailable nutrient pools, and stable hydrodynamic conditions. The vertical distribution of M. aeruginosa was highly transient; buoyant colonies formed early morning and late afternoon near-surface aggregations across the lake during periods of nonturbulent mixing (wind speed <4 m s-1). However, the extent of these near-surface aggregations was highly spatially variable, and nearshore morphometry appeared to be crucial in creating localized regions of nonturbulent water in which pronounced and persistent near-surface aggregations were observed. The formation of these near-surface scums would have been vital in alleviating light starvation in the turbid waters of Barton Broad. The calm water refuges in which persistent near-surface accumulations occurred may have been an important factor in determining the persistence of the bloom

Assessing the performance of morphologically based river typing in Scotland using a geomorphological and ecological approach

Traditionally, the interactions between geomorphic character and aquatic biodiversity have been widely acknowledged, but poorly quantified. However, the coupling of these disciplines is currently rising up legislative and political agendas, such as the European Union Water Framework Directive (EU WFD). The Directive requires Member States to classify rivers into types based on their natural morphology and geomorphic processes, and to link the biota to river types existing under natural conditions. Typing now forms the basis for evaluating environmental sensitivity to river engineering and determining reference conditions for river restoration. The Scottish Environment Protection Agency (SEPA) has adapted the Montgomery and Buffington (1997) channel typology developed in the Pacific Northwest of the USA for use in Scotland. The modified typology identifies eleven distinct channel types (e.g. bedrock, plane-bed, wandering and meandering). In this study, 43 reference condition sites in the upper River Dee catchment in the Cairngorms, Scotland were chosen to determine the geomorphic validity of the proposed typology, and assess whether channel types support a distinct macroinvertebrate community. Agglomerative Hierarchical Cluster Analysis failed to clearly identify eleven channel types based on catchment controls or on physical habitat characteristics. Four clusters were observed based on catchment drivers and six on physical habitat. Boundaries appear to be fuzzy, relating to a collective number of interacting environmental variables, geological discontinuities, and the geographic complexity of a river system. Multivariate ordinations and Analysis of Similarity indicated that macroinvertebrate communities only differed significantly between bedrock and step-pool reaches. A redundancy analysis showed differences in macroinvertebrate abundances among channel types were related to hydraulic, catchment drivers, physical habitat and physico-chemical variables. The results of the study have important implications for the use of geomorphic typologies in predicting aquatic biota.EThOS - Electronic Theses Online ServiceNatural Environment Research Council (NERC) : Scottish Environment Protection Agency (SEPA)GBUnited Kingdo

Ecological effects of the feeding and construction activities of the Eurasian beaver (Castor fiber) in Scotland : implications for reintroduction

Beavers have been described as a “keystone species” and “ecosystem engineers”, and in this dual role have great potential to physically modify their environment through tree-felling, foraging and construction activities. The resultant change in habitat heterogeneity can affect the flora and fauna that share the habitat with them. There has been recent interest in reintroducing the Eurasian beaver to the United Kingdom after an absence of over 400 years. To date, no research (aside from this thesis) has focussed on beaver ecology and behaviour in Scotland. This study has investigated the ecological effects of a small number of beavers in two enclosed but semi-natural Scottish sites at Bamff in Perthshire. The research conducted over a three-year period, with particular emphasis on the effects of tree-felling, foraging and construction activities. Trees were felled for both dietary and construction purposes, with felling rates being influenced by habitat availability, quality and the degree of habitat modification required. Highest rates were evident during the initial colonisation period of marginal sites (c. >300 trees / beaver / calendar year), and lowest rates in later years of occupation of more optimal sites (c. 55 – 70 trees / beaver / calendar year). Preferences were generally for willow and aspen trees, with conifers almost entirely avoided, and smaller trees preferred over larger ones. Proximity of trees to waterbodies was also an important factor, with nearer trees favoured, and generally most felling occurred within 50 m of water. Such behaviour followed the principles of optimal central place foraging. These preferences were less predictable however when intense construction activity was undertaken, with larger trees preferred and generic preferences for deciduous trees apparently invalid. In such cases, close proximity to the construction site was of prime importance. Increased cover of herbaceous plant species was observed in beaver-created canopy gaps in riparian woodland, whilst macrophyte diversity within waterbodies increased slightly in areas of herbaceous grazing. The diversity of terrestrial ground invertebrates was highest in areas of heavy tree-felling, and invertebrate richness and abundance was greatest in areas of herbaceous grazing under an intact tree-canopy. Furthermore, the abundance, diversity and richness of macroinvertebrate communities were increased by beaver-generated woody debris in ponds and streams. Overall, 30% of all macroinvertebrate species collected were found only in beaver-affected areas, due to the refugia and food supply provided by beaver dams, caches and lodges, as well as hydrological effects of these structures. These results are discussed with reference to future plans to return the beaver to Scotland. The habitat usage and modification of riparian ecosystems in northern Britain is likely to be similar to that found in this study, and the results are believed to be relevant, applicable and transferable to many areas of Scotland.EThOS - Electronic Theses Online ServiceScottish Natural Heritage (CASE studentship)GBUnited Kingdo

Best Practices for Monitoring and Assessing the Ecological Response to River Restoration

Nature-based solutions are widely advocated for freshwater ecosystem conservation and restoration. As increasing amounts of river restoration are undertaken, the need to understand the ecological response to different measures and where measures are best applied becomes more pressing. It is essential that appraisal methods follow a sound scientific approach. Here, experienced restoration appraisal experts review current best practice and academic knowledge to make recommendations and provide guidance that will enable practitioners to gather and analyse meaningful data, using scientific rigor to appraise restoration success. What should be monitored depends on the river type and the type and scale of intervention. By understanding how habitats are likely to change we can anticipate what species, life stages, and communities are likely to be affected. Monitoring should therefore be integrated and include both environmental/habitat and biota assessments. A robust scientific approach to monitoring and appraisal is resource intensive. We recommend that appraisal efforts be directed to where they will provide the greatest evidence, including ‘flagship’ restoration schemes for detailed long-term monitoring. Such an approach will provide the evidence needed to understand which restoration measures work where and ensure that they can be applied with confidence elsewhere

Determining tributary sources of increased sedimentation in East-African Rift Lakes.

This research article published by Elsevier B.V., 2020Temporal and spatial sediment dynamics in an East-African Rift Lake (Lake Manyara, Tanzania), and its river inputs, have been evaluated via a combination of sediment tracing and radioactive dating. Changes in sedimentation rates were assessed using radioactive dating of sediment cores in combination with geochemical profile analysis of allogenic and autogenic elements. Geochemical fingerprinting of riverine and lake sediment was integrated within a Bayesian mixing model framework, including spatial factors, to establish which tributary sources were the main contributors to recent lake sedimentation. The novel application of Bayesian source attribution on sediment cores and subsequent integration with sedimentation data permitted the coupling of changes in the rate of lake sedimentation with variations in sediment delivery from the tributaries. These complimentary evidence bases demonstrated that Lake Manyara has experienced an overall upward trajectory in sedimentation rates over the last 120 years with distinct maxima between 0.80 and 0.85 g cm yr in the 1960s and between 0.84 and 1.81 g cm yr in 2010. Increased sedimentation rates are largely a result of a complex interaction between increased upstream sediment delivery following changes in land cover and natural rainfall fluctuations. Modelling results identified two specific tributaries as responsible for elevated sedimentation rates, contributing 58% and 38% of the recently deposited lake sediment. However, the effects of sedimentation were shown to be spatially distinct given the domination of different tributaries in various areas of Lake Manyara. The application of source-tracing techniques constrained sedimentation problems in Lake Manyara to specific tributary sources and established a link between upstream land degradation and downstream ecosystem health. This novel application provides a solid foundation for targeted land and water management strategies to safeguard water security and environmental health in Lake Manyara and has potential application to fill knowledge gaps on sediment dynamics in other East-African Rift Lakes

Water and nitrate exchange between a managed river and a peri-urban floodplain aquifer: quantification and management implications

The management of rivers for navigation, hydropower and flood risk reduction involves the installation of in‐channel structures. These influence river levels and can affect groundwater flow within hydraulically‐connected riparian floodplain aquifers. A comprehensively monitored, peri‐urban, lowland river floodplain in the southern United Kingdom was used to explore these dependencies and to examine the implications for the flux exchange of water and nitrate between the river and the floodplain alluvial aquifer. The study demonstrated that rivers maintained at high levels by management structures, result in raised groundwater levels in the adjacent aquifer and complex groundwater flow patterns. Engineered river management structures were shown to promote flow from river to aquifer through the river bed but the majority of the associated nitrate was removed in the hyporheic zone. High‐ nitrate groundwater recharge to the alluvial aquifer also occurred through overbank flood flows. Across the floodplain, substantial denitrification occurred due to anaerobic conditions resulting from carbon‐rich sediments and the shallow water table, the latter linked to the river management structures. An upper limit on the total annual mass of nitrate removed from river water entering the floodplain aquifer was estimated for the study site (2.9 x 104 kg), which was three orders of magnitude lower than the estimate of annual in‐channel nitrate flux (1.8 x 107 kg). However, this capacity of lowland floodplains to reduce groundwater nitrate concentrations has local benefits, for example for private and public water supplies sourced from alluvial aquifers. The insights from the study also have relevance for those considering schemes that include the installation, removal or redesign of river management structures, as the resultant change in groundwater levels may have consequences for floodplain meadows and the nutrient status of the aquatic system

Suspended solids transport dynamics in regulated rivers

Suspended solids, turbidity and discharge data for thirty-seven reservoir releases, three major periods of dam overspill, and 20 unregulated tributary flood events, on seven different river systems, are analysed in order to examine suspended solids transport dynamics within regulated rivers and to assess the effectiveness of reservoir releases material. Within Great Britain, two sudden releases of water to the in removing within-channel accumulations of out of every five major reservoirs cause regulated river. Reservoir releases also provide, with their fixed and constant discharges, a unique opportunity to undertake field experiments investigating the importance of channel suspended solids sources, suspended solids supply limitation, the nature of the suspended solids load on turbidity and flow routing within upland boulder bed channels. The reservoir release suspended solids loads relate to sediment source depletion and changing sources along the channel. Close to the· dam, suspended loads are usually small with fine organic matter dominating the seston, which. scanning electron microscopy revealed to be predominantly autochthonous organic matter, with algal fragments derived from extensive and ·rapid periphyton growth within the regulated rivers. Downstream, minerogenic particles dominate the seston. This represents the flushing of channel bed accumulations derived from· unregulated tributaries. Seasonal variation in the nature of the suspended solids loads is also revealed. The quantity of material transported relates to the relationship between reservoir release or dam overspill frequency and that of unregulated tributary flood events. Marked hysteresis between suspended solids transport and discharge was characteristic on all the regulated rivers. In addition, hysteresis in the relationship between turbidity and suspended solids concentrations was also apparent, this relating to spatial and temporal changes in seston composition. Finally, the results obtained allow not only the nature of suspended solids transport within regulated rivers to be described and the effectiveness of reservoir releases for flushing in-channel accumulations of material to be ascertained but also the formulation of management guidelines and recommendations. These guidelines relate to effective environmental management of regulated river habitats in rivers experiencing reservoir releases

Detection of estuarine and tidal river hydromorphology using hyper-spectral and LiDAR data: Forth estuary, Scotland

High spatial resolution hyper-spectral imagery (CASI) and light detection and ranging (LiDAR) imagery acquired for the tidal River Carron and Forth estuary, Scotland, were used in conjunction with field surveys to assess the feasibility of monitoring hydromorphology and human alterations with satellite and airborne remote sensing data. The study was undertaken in the context of the European Union Water Framework Directive (WFD) that requires member states to monitor hydromorphological elements as a component of the ecological status of rivers, estuaries and shorelines. Visual assessment and automated classifications of the imagery were compared with field survey data for an estuarine reach comprising saline waters, mudflats, a tidal reach of a tributary river and an urban/industrialised shoreline. The morphology of the estuary and inflowing tidal waters together with most artificial features of interest could be clearly seen in the CASI imagery at 1 m spatial resolution. Supervised classification of the imagery produced an overall accuracy value of 72%. Downgrading the imagery to simulate the spatial resolution of 4 m IKONOS satellite data surprisingly improved the accuracy to 74%. Simulation of 10 m SPOT imagery resulted in an image where many artificial features of interest such as roads, pipelines and jetties were rendered invisible. Adding LiDAR data as an additional data set aided manual and automated identification of features and visualisation of the hydromorphology of the rivers and estuaries in the study area. Shadows cast from tall objects were a feature of the winter imagery and reduced automated classification accuracy. Overall, the study demonstrates that high spatial resolution remotely sensed digital imagery has the potential to be a useful tool for panoptic mapping of the geomorphology and human impact on tidal rivers and estuaries. In the context of the WFD, remote sensing provides a potential way forward for monitoring the physical status of rivers and estuaries at the national scale. The possibilities and constraints, in light of the findings of this study, are discussed