Characterizing Heterogeneity in Infiltration Rates During Managed Aquifer Recharge

Infiltration rate is the key parameter that describes how water moves from the surface into a groundwater aquifer during managed aquifer recharge (MAR). Characterization of infiltration rate heterogeneity in space and time is valuable information for MAR system operation. In this study, we utilized fiber optic distributed temperature sensing (FO‐DTS) observations and the phase shift of the diurnal temperature signal between two vertically co‐located fiber optic cables to characterize infiltration rate spatially and temporally in a MAR basin. The FO‐DTS measurements revealed spatial heterogeneity of infiltration rate: approximately 78% of the recharge water infiltrated through 50% of the pond bottom on average. We also introduced a metric for quantifying how the infiltration rate in a recharge pond changes over time, which enables FO‐DTS to be used as a method for monitoring MAR and informing maintenance decisions. By monitoring this metric, we found high‐spatial variability in how rapidly infiltration rate changed during the test period. We attributed this variability to biological pore clogging and found a relationship between high initial infiltration rate and the most rapid pore clogging. We found a strong relationship (R² = 0.8) between observed maximum infiltration rates and electrical resistivity measurements from electrical resistivity tomography data taken in the same basin when dry. This result shows that the combined acquisition of DTS and ERT data can improve the design and operation of a MAR pond significantly by providing the critical information needed about spatial variability in parameters controlling infiltration rates.     

The formation of the Hubble sequence of disc galaxies: the effects of early viscous evolution

We investigate a model of disc galaxies whereby viscous evolution of the gaseous disc drives material inwards to form a protobulge. We start from the standard picture of disc formation through the settling of gas into a dark halo potential well, with the disc initially coming into centrifugal equilibrium with detailed conservation of angular momentum. We derive generic analytic solutions for the disc–halo system after adiabatic compression of the dark halo, with free choice of the input virialized dark halo density profile and of the specific angular momentum distribution. We derive limits on the final density profile of the halo in the central regions. Subsequent viscous evolution of the disc is modelled by a variation of the specific angular momentum distribution of the disc, providing analytic solutions to the final disc structure. The assumption that the viscous evolution time-scale and the star formation time-scale are similar leads to predictions of the properties of the stellar components. Focusing on small 'exponential' bulges, i.e., ones that may be formed through a disc instability, we investigate the relationship between the assumed initial conditions, such as halo 'formation', or assembly, redshift z _f, spin parameter λ , baryonic fraction F , and final disc properties such as global star formation time-scale, gas fraction, and bulge-to-disc ratio. We find that the present properties of discs, such as the scalelength, are compatible with a higher initial formation redshift if the redistribution by viscous evolution is included than if it is ignored. We also quantify the dependence of final disc properties on the ratio F λ , thus including the possibility that the baryonic fraction varies from galaxy to galaxy, as perhaps may be inferred from the observations.     

The Kasila Group,Sierra Leone,an interpretation of new data

Recent geological mapping and U/Pb age determinations show that the Kasila Group has many of the characteristics shown by the Limpopo Belt and other high-grade linear metamorphic belts. The Kasila Group appears to form the southwestern periphery of the dominantly low-grade West African Archaean Craton.     

Patterns of water, heat, and solute flux through streambeds around small dams

Hyporheic exchange, enhanced by complex stream channel morphology, can influence biogeochemical processing in the streambed. These processes chemically alter water passing temporarily through the streambed, which eventually returns to the stream channel and can potentially affect surface water quality. To assess the degree of biogeochemical cycling induced by complex streambed morphology, we instrumented two 20-m reaches of Red Canyon Creek, Wyoming, each containing a small log dam, with in-stream minipiezometers and temperature data loggers. We simultaneously observed pore water geochemistry and streambed temperature dynamics in several bedforms located upstream or downstream of the dams. We modeled seepage flux into the streambed using heat transport modeling.
Upstream of the dams, low-permeability sediments have settled out in low-velocity pools, and enhanced anaerobic biogeochemical cycling occurred in the streambed. Rapid flux into the streambed occurred in glides immediately above the dams, where streambed temperature dynamics and geochemistry were nearly identical to the stream. In riffle sequences downstream of the dams, the streambed was oxygen rich, showed evidence of nitrification, and temperature dynamics indicated high connectivity between the streambed and the stream. Further downstream, streambed pore water geochemistry indicated ground water discharge occurring at the pool-riffle transition. Assessing streambed biogeochemical cycling may be facilitated by coupling streambed temperature measurements with pore water geochemistry and can aid in understanding how hyporheic exchange contributes to overall stream biogeochemistry.     

Geochemistry of basalts from the Dumisseau Formation, southern Haiti: implications for the origin of the Caribbean Sea crust

Basalt and diabase from the Cretaceous Dumisseau Formation, southern Haiti have Mg-numbers of 43–63, TiO₂ contents of 1.6–3.9% and La abundances of 3.6–15.3 ppm.La/Ta ratios average 10, and indicate that the basalts are oceanic in character, distinct from the arc associations forming the northern part of Haiti. Oldest lavas have low TiO₂ (1.6%) and are LREE-depleted, similar to N-MORBs, whereas overlying lavas have higher TiO₂ (2–3.9%) and are LREE-enriched, similar to E-MORBs or hotspot basalts.⁸⁷Sr⁸⁶Sr ratios vary from 0.70280 to 0.70316,¹⁴³Nd¹⁴⁴Nd from 0.512929 to 0.513121, and²⁰⁶Pb²⁰⁴Pb from 19.00 to 19.27. LREE-depleted lavas have high¹⁴³Nd¹⁴⁴Nd (0.51309–0.51310) typical of MORBs, whereas¹⁴³Nd¹⁴⁴Nd in the LREE-enriched lavas varies widely (0.512929–0.513121).Chemical features of the Dumisseau basalts are equivalent to those of Caribbean seafloor basalts recovered on DSDP Leg 15, and support the contention that the Dumisseau is an uplifted section of Caribbean Sea crust. Oldest lavas are analogous to MORB-like basalts cored at Leg 15 Sites 146, 150, 152 and 153, and the overlying lavas are analogous to incompatible-element-enriched basalts cored at Site 151 on the Beata Ridge. Isotopic compositions of the Dumisseau basalts overlap with those of the eastern Pacific Galapagos and Easter Island hotspots. However, the presence of N-MORB basalts in the lower part of the Dumisseau and at the majority of Leg 15 Sites indicates that the anomalously thick Caribbean crust probably did not originate as a hotspot-related basaltic plateau, but may have been generated by on-ridge or near-ridge hotspot magmatism.     

Identifying children’s perspectives on anti-social behaviour: Variations by home area and the implications

The paper examines the views of children living in contrasting British suburbs: exploring their perceptions of the occurrence of anti-social behaviour (ASB), their anxieties about different types of incident, and their views on appropriate punishments. Based on interviews with over 260 children aged 11–16 years, and 44 adults with a professional involvement in ASB, the evidence shows that the influence of home area on children’s perspectives of ASB varies according to the type of ASB under consideration. For ‘interpersonal’ ASB, children appear especially sensitive in the poorer area, where this ASB is much more common. Theories of normalisation regarding interpersonal ASB are not supported, as children in the poorer area are sensitised to the problems, rather than hardened, arguing for an urgent policy response. Regarding environmental ASB and the role of home area, the findings are reversed, and theories of normalisation are supported. Children’s lesser concerns about environmental ASB in the poorer, most affected area, pose rather different challenges to policy-makers, arguing for the selection of effective reduction measures at a local level, designed to better reflect the differing views of children in different areas. Identifying children’s perspectives brings new understandings to the multiple geographies of ASB, highlighting the importance of distinguishing between different types of ASB and raising awareness of the ways in which children’s perspectives may be similar and different from adults’ views. Our findings argue strongly for the central role of area in theoretical and applied ASB research, and a continuing emphasis on ‘the local’.     

How does the ownership of land affect household livelihood pathways under conditions of deagrarianization? ‘Hanging in’, ‘stepping up’ and ‘stepping out’ in two north Indian villages

In rural parts of the global South, livelihoods are diversifying away from agriculture. Nevertheless, agriculture typically still remains the backbone of rural life and is usually considered the prime source of economic security, social prestige and self‐identity. The task of narrating these somewhat contradictory processes in a conceptually coherent fashion has proven a major challenge for research. This paper responds to this problem by deploying an adapted version of Andrew Dorward's schema of households ‘hanging in, stepping up or stepping out’ of their landed interests. Dorward's middle‐ground theory provides an appropriate analytical vehicle for capturing the vagaries and situated complexities of the land‐livelihoods nexus. However the theory fails to fully appreciate the extent to which household livelihood decision making rests on complex entanglements that leverage land‐based and nonfarm activities against one another. We demonstrate the critical importance of these processes through the results of in‐depth interviews with 32 households in two north Indian villages. These interviews lead us to propose that land factors in livelihood aspirations in three fundamental ways: an arena for interpenetrated agrarian and nonagrarian livelihood streams; a base for social reproduction; and a bulwark of food (and by extension, livelihood) security through own‐production capabilities.     

Assessing the Impact of Climate Change on Water Supply and Flood Hazard in Ireland Using Statistical Downscaling and Hydrological Modelling Techniques

Estimates are made of changes in effective runoff at a high spatial resolution for the island of Ireland under different climate change scenarios. The first part of the investigation examines changes in annual and seasonal effective runoff for the whole land area of Ireland. The rainfall-runoff model HYSIM is used to carry out the hydrological simulations. The output from the HadCM3 Global Climate Model (GCM) is downscaled using statistical techniques to provide precipitation and evaporation data at a 10 km × 10 km resolution; this data is then used to drive the HYSIM model. Simulations are carried out for each of the 825 10 km × 10 km grid cells covering Ireland for the baseline period (1961–1990) and two future scenarios; 2041–2070 and 2061–2090. Parameter values are derived for each square using data from the Soil Survey of Ireland and the CORINE land use database and validation is carried out for selected catchments. The results of these simulations indicate a decrease in annual runoff that is most marked in the east and southeast of the country, whereas an increase is likely for the extreme northwest. The reduction in effective runoff for the east of the country is particularly marked during the summer months. It is these areas that have highest population density and also where greatest population growth is likely to occur. During the winter months an increase in effective runoff is suggested for the western half of country which could have implications for flood frequency, as well as the extent and duration of winter flooding.     

Emplacement processes of proto-arc basalt in the Izu–Bonin–Mariana arc system

Ascertaining the emplacement mechanism of oceanic basaltic lavas is important in understanding how ocean floor topography is produced and oceanic plates evolve, particularly during the early stages of crustal development of a supra-subduction zone. A detailed study of the volcanic stratigraphy at International Ocean Discovery Program (IODP) Site U1438 in the Amami Sankaku Basin, west of the Kyushu–Palau Ridge, has revealed the development of lava accretion and ridge topography on the Philippine Sea plate at about 49 Ma. Igneous basement rocks penetrated at Site U1438 are the uppermost 150 m of ~6 km-thick oceanic crust, and comprise, in a downhole direction, sheet flows (12.6 m), lobate sheet flows (61.3 m), pillow lavas (50.7 m), and thin sheet flows (25.3 m). The lowermost sheet flows are intercalated with layers of limestone and epiclastic tuff. Lithofacies analysis reveals that the lowermost sheet flows, limestone, and tuff formed on an axial rise, the pillow lavas were emplaced on a ridge slope, and the lobate sheet flows formed off ridge on an abyssal plain. The lithofacies of the basement basalt corresponds to the upper portions of fast-spreading oceanic crust, suggesting that subduction initiation was associated with intermediate to fast rates of seafloor spreading. The surface sheet flows are olivine–clinopyroxene-phyric basalt and differ from the lower basalt flows that contain phenocrysts of olivine and plagioclase, with or without clinopyroxene. The depleted chrome-spinel composition and olivine–clinopyroxene phenocryst assemblage in the surface sheet flows suggests a slight contribution of water for magma generation not present for the lower basalt flows. Considering the lithological difference between the backarc and forearc oceanic crust in the Izu–Bonin–Mariana arc, with sheet flow dominant in the former, seafloor spreading occurred faster in the later stage of subduction initiation.