A Web-based system enabling the integration,analysis, and 3D sub-surface visualization of groundwater monitoring data and geological models

The 3D Water Chemistry Atlas is an intuitive, open source, Web-based system that enables the three-dimensional (3D) sub-surface visualization of ground water monitoring data, overlaid on the local geological model (formation and aquifer strata). This paper firstly describes the results of evaluating existing virtual globe technologies, which led to the decision to use the Cesium open source WebGL Virtual Globe and Map Engine as the underlying platform. Next it describes the backend database and search, filtering, browse and analysis tools that were developed to enable users to interactively explore the groundwater monitoring data and interpret it spatially and temporally relative to the local geological formations and aquifers via the Cesium interface. The result is an integrated 3D visualization system that enables environmental managers and regulators to assess groundwater conditions, identify inconsistencies in the data, manage impacts and risks and make more informed decisions about coal seam gas extraction, waste water extraction, and water reuse.     

Simulating wetland impacts on stream flow in southern Africa using a monthly hydrological model

The processes that occur in wetlands and natural lakes are often overlooked and not fully incorporated in the conceptual development of many hydrological models of basin runoff. These processes can exert a considerable influence on downstream flow regimes and are critical in understanding the general patterns of runoff generation at the basin scale. This is certainly the case for many river basins of southern Africa which contain large wetlands and natural lakes and for which downstream flow regimes are altered through attenuation, storage and slow release processes that occur within the water bodies. Initial hydrological modelling studies conducted in some of these areas identified the need to explicitly account for wetland storage processes in the conceptual development of models. This study presents an attempt to incorporate wetland processes into an existing hydrological model, with the aim of reducing model structural uncertainties and improving model simulations where the impacts of wetlands or natural lakes on stream flow are evident. The approach is based on relatively flexible functions that account for the input–storage–output relationships between the river channel and the wetland. The simulation results suggest that incorporating lake and wetland storage processes into modelling can provide improved representation (the right results for the right reason) of the hydrological behaviour of some large river basins, as well as reducing some of the uncertainties in the quantification of the original model parameters used for generating the basin runoff. Copyright © 2013 John Wiley & Sons, Ltd.     

Physical-hydraulic properties of tropical sandy-loam soil in response to rice-husk dust and cattle dung amendments and surface mulching

ABSTRACT

The effects of topsoil addition of rice-husk dust (RHD) and cattle dung (CD), alongside surface mulching with dry grasses/legume, on the infiltration characteristics and intrinsic structural properties of a deep, well-drained soil in southeastern Nigeria are assessed. Treatments are RHD-amended, CD-amended and “unamended”, each plot being either surface-mulched or left bare, with the unamended-bare plots as control. Amendments and mulch were applied at 20 t/ha equivalents. Their effects on the soil’s infiltration characteristics 7 months later were not evident; however, there was a tendency for differences: CD-amended ≥ RHD-amended ≥ unamended and surface-mulched ≥ bare-surface. By contrast, saturated hydraulic conductivity (K_s ) differed thus: CD-mulched ≥ unamended-mulched > the rest. Similar values were recorded for K_s (50.89 cm/h) and final infiltration rate (50.74 cm/h) only under CD-amended plots, which also showed the highest values (43.50 cm/h) for transmissivity of the soil. Soil penetrometer resistance was lowest in CD-amended plots (113.44 kPa) and highest in unamended plots (166.78 kPa). Topsoil addition of cattle dung and surface mulching could increase infiltration, though marginally, and permeability of coarse-textured tropical soils beyond the season of their application when their effects on soil structure have almost waned.     

Micromorphological analysis of poly‐phase deformation associated with the transport and emplacement of glaciotectonic rafts at West Runton,north Norfolk,UK

The ability of glaciers to detach and transport bedrock as glaciotectonic rafts is widely observed throughout Quaternary sections. However, the glaciological, hydrological and geological parameters controlling rafting are currently poorly constrained. There is a lack of structural and sedimentary evidence concerning rafting, and therefore the processes driving raft detachment, transport and emplacement are poorly understood. This paper contributes to our understanding by presenting a macro‐ and microstructural study of deformation associated with a chalk raft at West Runton, north Norfolk. Detailed thin‐section analysis reveals several discrete micro‐fabric orientations, representing poly‐phase deformation occurring during raft transport and emplacement. A four‐stage conceptual model for raft transport and emplacement is proposed, with deformation being partitioned into the relatively weaker Happisburgh Till member, the latter forming the host to the raft. Stage 1 is the main transport phase of the chalk raft, and was dominated by easterly (down‐ice) directed ductile shearing. During Stage 2 a narrow ductile shear zone within the Happisburgh Till member propagated upwards through the base of the raft, leading to the detachment of an elongate block of chalk. Attenuated lenses of diamicton in this shear zone possess kinematics recording an easterly directed sense of shear. As deformation progressed, during Stage 3, the detached block impinged on the ‘high‐strain’ zone wrapping the base of the raft, influencing the style of deformation partitioning and leading to localized, up‐ice‐directed kinematics. Stage 4 represents the final stages of raft emplacement, when the detachment zone at the base of the raft began to ‘lock‐up’. These results demonstrate the relative importance of the hydrological controls associated with raft transport and emplacement underneath an actively advancing glacier. Furthermore, the model represents an example of how micromorphological analysis can reveal detailed poly‐phase deformation histories in deformed glacial sediments.     

Climatic Influences on Autochthonous and Allochthonous Phytoplankton Blooms in a Subtropical Estuary, St. Lucie Estuary, Florida, USA

The St. Lucie Estuary, located on the southeast coast of Florida, provides an example of a subtropical ecosystem where seasonal changes in temperature are modest, but summer storms alter rainfall regimes and external inputs to the estuary from the watershed and Atlantic Ocean. The focus of this study was the response of the phytoplankton community to spatial and temporal shifts in salinity, nutrient concentration, watershed discharges, and water residence times, within the context of temporal patterns in rainfall. From a temporal perspective, both drought and flood conditions negatively impacted phytoplankton biomass potential. Prolonged drought periods were associated with reduced nutrient loads and phytoplankton inputs from the watershed and increased influence of water exchange with the Atlantic Ocean, all of which restrict biomass potential. Conversely, under flood conditions, nutrient loads were elevated, but high freshwater flushing rates in the estuary diminished water residence times and increase salinity variation, thereby restricting the buildup of phytoplankton biomass. An exception to the latter pattern was a large incursion of a cyanobacteria bloom from Lake Okeechobee via the St. Lucie Canal observed in the summer of 2005. From a spatial perspective, regional differences in water residence times, sources of watershed inputs, and the proximity to the Atlantic Ocean influenced the composition and biomass of the phytoplankton community. Long water residence times in the North Fork region of the St. Lucie Estuary provided an environment conducive to the development of blooms of autochthonous origin. Conversely, shorter residence times in the mid-estuary limit autochthonous increases in biomass, but allochthonous sources of biomass can result in bloom concentrations of phytoplankton.     

The Contribution of Benthic Nutrient Regeneration to Primary Production in a Shallow Eutrophic Estuary,Weeks Bay,Alabama

Benthic oxygen, dinitrogen, and nutrient fluxes (NH₄⁺, NO₃⁻, and PO₄³⁻) were measured monthly during a 1-year period at two locations in Weeks Bay, a shallow (1.4 m) and eutrophic estuary in Alabama. Gross primary productivity (GPP), ecosystem respiration (R), and net ecosystem metabolism were determined from high-frequency dissolved oxygen measurements. Peak water column NO₃⁻ (55 μM) and chlorophyll a (138 μg/l) concentrations were measured during spring and fall, respectively. Sediments were a net source of NH₄⁺ (102 μmol m⁻² h⁻¹) and PO₄³⁻ (0.9 μmol m⁻² h⁻¹) but a sink for NO₃⁻ (−30 μmol m⁻² h⁻¹). Benthic N₂ fluxes indicated net N fixation (12 μmol N m⁻² h⁻¹). Sediment oxygen demand (0.55 g O₂ m⁻² day⁻¹) accounted for <10% of R (7.3 g O₂ m⁻² day⁻¹). Despite high GPP rates (4.7 g O₂ m⁻² day⁻¹), the estuary was net heterotrophic. Benthic regeneration supplied, on average, 7.5% and 4% of primary productivity N and P demands, respectively. These results contrast with the conventional view that benthic regeneration accounts for a large fraction of phytoplankton nutrient demand in shallow estuaries.     

Crustal volatile release at Merapi volcano; the 2006 earthquake and eruption events

High‐temperature gas in volcanic island arcs is widely considered to originate predominantly from the mantle wedge and from subducted sediments of the down‐going slab. Over the decade (1994–2005) prior to the 2006 eruption of Merapi volcano, summit fumarole CO₂ gas δ¹³C ratios are relatively constant at ?4.1 ± 0.3‰. In contrast, CO₂ samples taken during the 2006 eruption and after the May 26th 2006 Yogyakarta earthquake (M6.4) show a dramatic increase in carbon isotope ratios to ?2.4 ± 0.2‰. Directly following the earthquake (hypocentre depth 10–15 km), a 3–5‐fold increase in eruptive intensity was observed. The elevated carbon isotope gas data and the mid‐crustal depth of the earthquake source are consistent with crustal volatile components having been added during the 2006 events, most probably by the thick local limestone basement beneath Merapi. This ‘extra’ crustal gas likely played an important role in modifying the 2006 eruptive behaviour at Merapi and it appears that crustal volatiles are able to intensify and maintain eruptions independently of traditional magmatic recharge and fractionation processes.     

Local physiographic controls on the responses of Arctic lakes to climate warming in Sirmilik National Park,Nunavut, Canada

Twenty high Arctic lakes and ponds were sampled for water chemistry and modern diatom assemblages in two distinct physiographic sectors of Sirmilik National Park, Nunavut, Canada. Sites on southwestern Bylot Island were warmer, more alkaline, less dilute, and had higher concentrations of nutrients, DOC and Chl-a (mesotrophic to oligo-mesotrophic), whereas sites on Qorbignaluk Headland on northern Baffin Island were deeper, very dilute, mostly oligotrophic and had lower pH. Diatom assemblages differed markedly between these two regions as a consequence of limnological differences between them. Paleolimnological records, spanning > 200 years and dated by ²¹⁰Pb activity, were produced from each region to compare biological responses to recent warming inferred from glaciological studies on Bylot Island and regional syntheses for the Arctic. Diatom assemblages began to change around AD 1900 at both sites. At Qorbignaluk Headland, marked shifts in diatom community composition occurred during the twentieth century, with large increases in the abundance of planktonic diatoms. At Bylot Island, diatom community changes began around the same time, and involved modest decreases in planktonic diatoms and increases in inferred specific conductance, likely because of a decrease in the areal extent of the small lake as a response to warming. The study confirms that responses of freshwater ecosystems to climate warming vary depending on local physiographic factors.     

Temporal englacial water content variability associated with a rapidly retreating glacier

This study uses a combination of evidence from ground penetrating radar, borehole, video, and wireless probe data to assess temporal changes in englacial water content associated with Briksdalsbreen, a rapidly retreating Norwegian glacier. Over a 13 day period in 2006, ice radar‐wave velocity varied between 0·135 m/ns (± 0·009) and 0·159 m/ns (± 0·003), and water content from 7·8% (+2·6, ?2·8) to 2·5% (+0·9, ?1·1) [derived from the Looyenga (Physica 31 (3): 401–406, 1965) formula]. It is suggested that during warm precipitation free days, void spaces within the glacier become filled with water, resulting in low radar‐wave velocity. This stored water then drained during cold, high precipitation days, allowing the radar‐wave velocity to rise. These changes in englacial storage were caused by the enhanced crevassing generated by the newly floating ice margin, and were associated with accelerated glacier retreat. Copyright © 2011 John Wiley & Sons, Ltd.