Groundwater-supported evapotranspiration within glaciated watersheds under conditions of climate change

This paper analyzes the effects of geology and geomorphology on surface-water/-groundwater interactions, evapotranspiration, and recharge under conditions of long-term climatic change. Our analysis uses hydrologic data from the glaciated Crow Wing watershed in central Minnesota, USA, combined with a hydrologic model of transient coupled unsaturated/saturated flow (HYDRAT2D). Analysis of historical water-table (1970–1993) and lake-level (1924–2002) records indicates that larger amplitude and longer period fluctuations occur within the upland portions of watersheds due to the response of the aquifer system to relatively short-term climatic fluctuations. Under drought conditions, lake and water-table levels fell by as much as 2–4 m in the uplands but by 1 m in the lowlands. The same pattern can be seen on millennial time scales. Analysis of Holocene lake-core records indicates that Moody Lake, located near the outlet of the Crow Wing watershed, fell by as much as 4 m between about 4400 and 7000 yr BP. During the same time, water levels in Lake Mina, located near the upland watershed divide, fell by about 15 m. Reconstructed Holocene climate as represented by HYDRAT2D gives somewhat larger drops (6 and 24 m for Moody Lake and Lake Mina, respectively). The discrepancy is probably due to the effect of three-dimensional flow. A sensitivity analysis was also carried out to study how aquifer hydraulic conductivity and land-surface topography can influence water-table fluctuations, wetlands formation, and evapotranspiration. The models were run by recycling a wet year (1985, 87 cm annual precipitation) over a 10-year period followed by 20 years of drier and warmer climate (1976, 38 cm precipitation). Model results indicated that groundwater-supported evapotranspiration accounted for as much as 12% (10 cm) of evapotranspiration. The aquifers of highest hydraulic conductivity had the least amount of groundwater-supported evapotranspiration owing to a deep water table. Recharge was even more sensitive to aquifer hydraulic conductivity, especially in the lowland regions. These findings have important implications for paleoclimatic studies, because the hydrologic response of a surface-water body will vary across the watershed to a given climate signal.     

Effects of Spatiotemporal Constraints on Geostatistical Analysis of Groundwater Depth

Geostatistical evaluation of the groundwater depth (GWD) in California's South Coast hydrologic region, and its sensitivity to different spatiotemporal assumptions, is presented in this paper. We obtain a pseudo-stationary representation of the groundwater depth, using the publicly available, online database from the GAMA GeoTracker project, while tracking the associated uncertainty throughout the process. We create nine different sub-datasets, using different temporal constraints, such as seasonal partitioning and different long-term variability filtering criteria. The geostatistical analysis and comparison between the different maps highlight the trade-off between spatial and temporal accuracy. For example, when moving to stricter filtering criteria, despite removing a large number of sites from the interpolation, the root mean squared error (RMSE) calculated in the analysis either decreased or only slightly increased. This suggests that the long-term variability filter is a good representation of the GWD accuracy and that the cross-validation RMSE captures both the stability effect as well as spatial density of the measurement points. We further find that the point-specific standard error is strongly correlated with the associated GWD prediction and that the mean relative error is approximately 60% of the prediction. Hence, it is highly recommended to account for such error in a forward-engineering application, by introducing a GWD distribution rather than a single value into the analysis. Finally, we analyze seasonal fluctuations in the study region and find that they are on average 2.5 m with a standard deviation of 8 m.     

An Inexpensive, Multi-Use, Dedicated Pump for Ground Water Monitoring Wells

A simple, inexpensive sampling pump has lately come into use in ground water monitoring. The pump is referred to as an inertial pump; its only downhole components are a foot valve connected to a length of tubing or pipe. The operating principle of the pump is based on the inertia of a column of water within the riser tubing. Ground water is drawn through the foot valve and up the riser tubing by rapid up and down movements of the tubing. This pumping method is not new, but has only recently been applied to monitoring wells. Foot valves are available in a variety of materials and sizes and can be used in monitoring wells as small as 19mm (3/4 inch) I.D. Flexible polyethylene or Teflon® tubing, and in some cases stainless steel tubing or rigid PVC pipe, is used as the riser. The inertial pump satisfies most of the criteria normally cited for an "ideal" sampling device. The pump is easy to operate, reliable, durable, portable, and virtually maintenance-free. It can be operated manually from as deep as 40m or from as deep as 60m using a motor drive. The pump is inexpensive, and therefore suitable for use as a dedicated sampling pump. Recent tests have shown the pump to be suitable for sampling volatile organics. The inertial pump has a high flow capacity and performs well in silty/sandy environments, which makes it useful for developing and purging monitoring wells. It may also be used to perform field hydraulic conductivity tests.     

Identifying Potential Pollutant Point Sources in an Area of High Ground Water Consumption

The Commonwealth of Pennsylvania relies heavily upon its ground water resources for drinking water. The U.S. Environmental Protection Agency, Region III, is responsible for regulating the discharge of waste to the subsurface through injection wells within Pennsylvania. To facilitate identification of industrial facilities unregulated by EPA that may be contaminating ground water through industrial water and waste water discharge wells, a screening procedure was devised utilizing a Geographic Information System (GIS). This procedure involved cross-referencing locations of industrial sites to maps of municipal sewer systems. The effectiveness of this GIS screening procedure was investigated in seven counties in southeastern Pennsylvania. Facilities identified by the procedure were inspected for possible violations of Underground Injection Control (UIC) program regulations. As a result of these inspections, many facilities were found to be illegally discharging waste into ground water. In addition, other EPA program violations were identified. The project demonstrated that the GIS screening procedure can be an effective tool to locate sources of pollution of ground water.     

Using a Combination of Digital Aerial Photography and Satellite Remote Sensing to Assist Contemporary Restructuring in an Urban Area of South Africa

Abstract

The transition and restructuring process of urban South Africa are currently in the phase of identifying land development objectives. These objectives aim to integrate previously segregated areas through integrated development plans. This research aims firstly to identify and describe the historical development of the spatial form and structure of the secondary city and capital of the Northern Province, Pietersburg and its dispersed peripheral towns. Supervised classification of SPOT HRV multispectral imagery is used to support the theoretical explanation. Images from an airborne digital Kodak DCS 420 camera are used to provide training sites in the pre‐classification stages, and also provide field data to the process of post‐classification accuracy assessment. Secondly, SPOT HRV imagery is applied to identify the stark contrast in urban development between the city of Pietersburg and its surrounding former homeland towns. Both built and natural environmental aspects are investigated. In conclusion benefits and problems of assessing urban morphology and development in a developing country by means of a combination of satellite imagery and digital aerial photography are discussed.     

Integration of the scientific community as exemplified by the biotech sector: An analysis based on bibliometric indicators in the Danish–Swedish border region

This paper presents an account of the progress of the integration between the Danish and Swedish parts of the Öresund Region within the world of science, with emphasis on biotech. The paper is based on data from the database Science Citation Index Expanded. The amount of co-authorships produced by agents from each side of the region is analysed for a 12-year period (1994–2005) and used as an indicator to show how the integration is proceeding. Each of the co-authorships is examined to shed light on the nature of the interactions, thereby identifying the agents most involved in collaboration. Furthermore, the development in co-authorships within the region is compared to the development in co-authorships between the Öresund Region and four selected reference areas. Our findings indicate that there has been a substantial increase in both the number of co-authorships overall and within biotech solely. The rise in co-authorships between the two parts is proceeding at a faster pace than the rise in co-authorships between the Öresund Region and the reference areas. The overall results of this paper indicate a growing integration of the biotech sector in the Öresund Region.     

Refractory megacrysts and magnesium-rich melt inclusions within spinel in oceanic tholeiites: Indicators of magma mixing and parental magma composition

Refractory megacrysts of olivine, plagioclase, chromian diopside and Cr-Al spinel, which were not in equilibrium with the host oceanic tholeiite on eruption, are present in samples from several dredge sites and DSDP drill sites in the Atlantic and Pacific Oceans. They have multiple origins: (1) cognate or accidental mantle fragments; (2) relict fragments from fractional crystallization of parental liquids considerably more primitive than oceanic tholeiite; and most commonly (3) the fractional crystallization products of such liquids mixed with oceanic tholeiite magma. Melt inclusions in chrome-spinel phenocrysts provide evidence for this postulated Mg- and Ca-rich magma which has counterparts in the Scottish Tertiary Province and in west Greenland.     

Development of a thermal desorption method for the analysis of particle associated polycyclic aromatic hydrocarbons in ambient air

An investigation for the analysis of polycyclic aromatic hydrocarbons in airborne particulates using thermal desorption and gas chromatography-mass spectrometry is described. Samples are obtained from ambient air using fibreglass filters and the volatile material from the filter is thermally desorbed to gas chromatograph. A 30 meter capillary column is used to separate the hydrocarbons and eight polyaromatic hydrocarbons are used to test the method and recovery is >95%. The eight polycyclic aromatic hydrocarbons anthracene, phenanthrene, fluoranthrene, pyrene, benzo (a) anthracene, chrysene, benzo (a) pyrene and benzo (e) pyrene were the most abundant PAHs found in the samples of ambient air with current method at Uxbridge-London. Application of the measurement of polycyclic aromatic hydrocarbons in ambient air samples shows that the hydrocarbons trapped in the particle phase to a lesser degree at higher ambient temperature. In conclusion a method has been developed to transfer the PAHs in particle phase from a filter to GC-MS by thermal desorption. A standard mixture of PAHs, when absorbed onto the filter, did lead to strong analyte absorbent interactions by the high percent recovery of the sample.     

Alluvial, eolian and lacustrine sedimentology of a Paleoproterozoic half-graben, Baker Lake Basin, Nunavut, Canada

The northeast-trending Baker Lake sub-basin was a volcanically active, half-graben during deposition of ca. 1.85–1.76 Ga Baker Lake Group. Drainage was oriented along transverse and axial directions with flow to playa lake and deeper perennial lacustrine depocentres. Basin marginal, streamflow-dominated alluvial fans were concentrated along the southern margin, and provided sediment from Archean crystalline basement rocks. These fed transverse gravel- and sand-bed braided streams. Alluvial dynamics were characterized by channel aggradation and abandonment. Abandoned channel belts were sites of floodplain and eolian deposition. Basin axial braided streams fed northeast and southwest to a depocentre near Christopher Island, where eolian, playa and lacustrine environments were intimately linked. Felsic minette flows were initially erupted from localized centres; contemporaneous sedimentary deposits typically contain minor volcaniclastic components that increase in abundance basinward. Voluminous and widespread younger minette flows prograded outward from volcanic centres contributing significant additional basin-infill.