Measured river leakages using conventional streamflow techniques: the case of Souhegan River, New Hampshire, USA

Multiple streamflow measurements were made at coupled discharge measurement stations to quantify rates of aquifer recharge and discharge on two reaches of the Souhegan River, New Hampshire, USA, flowing within a glacial-drift river-valley aquifer. The reaches included a predominantly losing (aquifer recharge) reach and a variable (aquifer recharge and discharge) reach located downstream of the former reach. River leakage, the differential between coupled upstream and downstream streamflow measurements along a reach, varied by almost 30 cubic feet per second (ft³/s) (0.85 m³/s) along the two reaches. The upper reach averaged 3.94 ft³/s (0.11 m³/s) loss whereas the lower reach averaged 4.85 ft³/s (0.14 m³/s) gain. At the upper reach, 13 losses were measured out of 19 coupled measurements. At the lower reach, ten out of 13 coupled measurements indicated gains in flow and suggest that this reach is primarily a gaining river reach. An important factor in river leakage appears to be antecedent trends in river stage. At the upper reach, gains were measured only during periods of declining river stage. Conversely, at the lower reach, streamflow loss was measured primarily during periods of rising river stage. Although some tendencies exist, several factors complicate the analysis of river leakage, most notably the inaccuracies in computed stream discharge.     

Measuring proton energies and fluxes using EIT (SOHO) CCD areas outside the solar disk images

An indirect proton flux measuring tool based on discrimination of the energy deposited by protons in 128 × 128 pixel EIT CCD areas outside the solar disk images is presented. Single pixel intensity events are converted into proton incident energy flux using modeled energy deposition curves for angles of incidence ±60° in four EIT spatial areas with different proton stopping power. The extracted proton flux is corrected for both the loss of one‐pixel events in the range of angles of incidence as well as for the contribution to the single pixel events resulting from scattered middle‐energy protons (low‐energy or high‐energy particles are stopped by the EIT components or pass through them, accordingly). A simple geometrical approach was found and applied to correct for a non‐unique relation between the proton‐associated CCD output signal and the incident proton energy. With this geometrical approximation four unique proton incident energy ranges were determined as 45–49, 145–154, 297–335, and 390–440 MeV. The indirect proton flux measuring tool has been tested by comparing Solar Energetic Particles (SEP) flux temporal profiles extracted from the EIT CCD frames and downloaded from the GOES database for the Bastille Day (BD) of 2000 July 14 and the more recent 2005 January 20 events. The SEP flux temporal profiles and proton spectra extracted from the EIT in the relatively narrow energy ranges between 45 and 440 MeV reported here are consistent with the related GOES profiles. The four additional EIT extracted ranges provide higher energy resolution of the SEP data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Ce/Nd isotope study of crustal contamination processes affecting Palaeocene magmas in Skye,Northwest Scotland

Twelve¹³⁸Ce/¹³⁶Ce isotope determinations, 31 Nd isotope analyses, and 31 REE profiles are presented for Tertiary basic to intermediate igneous rocks from the Isle of Skye, NW Scotland. The aim of this work is to precisely identify the contamination mechanisms of basic magmas emplaced through old crust, and to test the effectiveness of Ce isotope analysis as a petrogenetic tool.Combined Ce/Nd isotope analysis enables the modelling of the light REE profiles of the mantle-derived precursors to contaminated lavas, using different crustal end-members, in order to compare these with the magmatic lineage of uncontaminated Skye lavas. The geochemical data support a contamination mechanism involving a granitic melt, produced either by large degree melting of Scourian granulitefacies acid sheets, or (possibly) by melting of intermediate gneiss out of isotopic equilibrium.Basaltic lavas showing strong isotopic contamination effects yield calculated degrees of crustal contamination by large degree granitic melts of ca. 8 or 9% based on Ce and Nd isotopic data respectively. However, for lavas with liquidus temperatures of over 1250° C, the temperature dependence of the degree of contamination is weak.The combination of this evidence with new and published Pb isotope data suggests that the bulk of crustal contamination of the Skye lavas occurred in sill complexes at distinct levels in the crust, rather than during the actual ascent of magma through the crust in dykes. It is suggested on the basis of published fluid dynamic and field evidence that the assimilation of large degree melts of acid gneiss by turbulently flowing magma is more likely than assimilation of small degree disequilibrium melts from more refractory intermediate gneisses.It is concluded that Ce isotope analysis is a viable and useful adjunct to Nd isotope data in petrogenetic studies of continental igneous rocks emplaced through old basement.     

Use of GIS in Optimizing Timber Thinning Strategies in the Eastern Sierra Nevada*

This paper demonstrates the use of a Geographic Information System (GIS) to develop timber thinning strategies on the Kyburz Planning Area of the Tahoe National Forest in northeastern California. The primary criteria used in an assessment of selective thinning potential were forest health and fire hazard ratings. By eliminating environmentally sensitive, economically unfeasible, or low fire hazard areas from consideration, the use of GIS reduced the area that was considered appropriate for thinning by approximately 58%. GIS offers considerable potential for improving resource management strategies.     

The scaling of flow in vegetative structures

Sensible heat flux data obtained from the U.S. Environmental Protection Agency's Regional Air Pollution Study in St. Louis, Missouri are presented and discussed. Large spatial variations exist in heat flux on both a land-use scale and the urban scale. Arguments based upon empirical data and sampling theory show that estimates of heat flux representative of an upwind fetch l _x require a minimum observation height proportional to z ^3/4. The influence of advection on the magnitude of the heat flux is also explored for both the urban and sub-urban or land-use scales. The data clearly indicate that advection can strongly modulate and even dominate the vertical heat flux above surfaces in areas which maintain large horizontal temperature gradients. The advection contribution is positive for cold air advection and negative for warm air advection, and may result from either the urban heat island or land-use mesoscale features. The depth of advective influence is directly proportional to the horizontal scale of the phenomenon and inversely proportional to horizontal temperature gradient.     

Shaking and splashing—A case study of far-field effects of the Mjølnir asteroid impact on depositional environments in the Barents Sea

The Mjølnir impact crater in the Norwegian Barents Sea features among the 20 largest impact craters listed in the Earth Impact Database. The impact is dated to 142 ± 2.6 Ma, corresponding closely to the Jurassic/Cretaceous boundary in the Boreal stratigraphy. Multidisciplinary studies carried out over the last three decades have suggested that the up to 40 km wide crater was created by a 1–3 km diameter impactor colliding with a shallow epicontinental sea, causing regional havoc and a regional ecological crisis that followed in its wake. Only minor evidence for the consequences of the impact for the surrounding depositional basins has been documented so far. This study describes a large submarine slump penetrated by hydrocarbon exploration well 7121/9-1, located in the southern Hammerfest Basin and approximately 350 km away from the impact site. The slump is dated by a black shale drape, which contains characteristic impact-related biotic assemblages and potential ejecta material. This precise dating enables us to associate the slump with large-scale fault movements and footwall collapse along the basin-bounding Troms-Finnmark Fault Complex, which we conclude were caused by shock waves from the Mjølnir impact and the passage of associated tsunami trains. The draping black shale is interpreted to represent significant reworking of material from the contemporary seabed by tsunamis and currents set up by the impact.     

Nondestructive determination of the physical properties of Antarctic meteorites: Importance for the meteorite—parent body connection

Photogrammetry is a low-cost, nondestructive approach for producing 3-D models of meteorites for the purpose of determining sample bulk density. Coupled with the use of a nondestructive magnetic susceptibility/electrical conductivity field probe, we present measurements for the interrogation of several physical properties, on a set of Antarctic meteorites. Photogrammetry is an effective technique over a range of sample sizes, with meteorite bulk density results that are closely comparable with literature values, determined using Archimedean glass bead or laser scanning techniques. The technique is completely noncontaminating and suitable for the analysis of rare or fragile samples, although there are limitations for analyzing reflective samples. It is also flexible, and, with variations in equipment setup, may be appropriate for samples of a wide range of sizes. X-ray computed tomography analyses of the same meteorite samples yielded slightly different bulk density results, predominantly for samples below 10 g, although the reason for this is unclear. Such analyses are expensive and potentially damaging to certain features of the sample (e.g., organic compounds), but may be useful in expanding the measurements to accommodate an understanding of internal voids within the sample, lending itself to measurement of grain density. Measurements of bulk density are valuable for comparisons with estimates of the bulk densities of asteroids that are suggested as meteorite parent bodies.     

Monitoring active volcanoes and mitigating volcanic hazards: the case for including simple approaches

Simple approaches to problems brought about eruptions and their ensuing hazardous effects should be advocated and used by volcanologists while awaiting more sophisticated remedies. The expedients we advocate have all or many of the following attributes: only locally available materials are required; no extensive training of operators or installation is necessary; they are affordable and do not require foreign aid or exports; they are often labor intensive and are sustainable without outside assistance. Where appropriate, the involvement of local residents is advocated. Examples of simple expedients which can be used in forecasting or mitigating the effects of crises emphasize the relative ease and the less elaborate requirements with which simple approaches can be activated. Emphasis is on visual observations often by untrained observers, simple meteorogical measurements, observations of water level in lakes, temperature and chemistry of springs and fumaroles, new springs and collapse areas and observations of volcanic plumes. Simple methods are suggested which can be applied to mitigating damage from mudflows, nuées ardentes, tephra falls and gas discharge. A review in hindsight at Ruiz includes the use of both chemical indicators and simple mudflow alarms. Simple expedients are sufficiently effective that any expert volcanologist called to aid in a crisis must include them in the package of advice offered. Simple approaches are a critical and logical complement to highly technical solutions to hazardous situations.     

Glacial Lake Outburst Floods in the Nepal Himalaya: A Manageable Hazard?

Within the past fifteen years, glacial lake outburst floods have become an activetopic of discussion within the development community focused on Nepal. Suchfloods endanger thousands of people, hundreds of villages, and basic infrastructuresuch as trails and bridges. The flood risk is also a major impediment to hydroelectricdevelopment in several river basins. Unlike most other mountain hazards in Nepal,reducing the possibility of outburst floods is technically feasible. The first attemptwithin Nepal to reduce the hazard of one lake by artificially lowering its water levelwas partially completed in June 2000. Completing this task and beginning work onother hazardous lakes will require difficult decisions about risk by downstream residentsand substantial investment from the international aid community.