Using 3D Printing to Create a Robust and Compact Peristaltic Field Pump: An Update to the Montana Drill Pump

The collection of water samples from springs, streams, and wells is a critical component of field hydrogeological studies. Fieldwork, especially in mountainous terrain, often involves hiking to remote springs and streams. It is logistically and physically difficult to carry bulky, heavy sampling equipment such as large peristaltic pumps with built‐in batteries in these areas. To address this problem, researchers at the University of Montana designed the Montana Drill Pump (MDP) roughly 30 years ago to provide a compact, low‐cost and portable option for sampling with a peristaltic pump in the backcountry (Woessner 2007 ). Although the MDP is popular, with the advent of 3D printing techniques, a more robust and precise fitting pump design can be inexpensively created that can be quickly assembled in the lab or field. This new pump design was tested on multiple backpacking sampling campaigns in the Panamint Mountains of southern California, Mount Hood in Oregon, and Glacier National Park in northern Montana during the summer of 2017. The design was proven to be easy to use and durable in the field and offers a rugged, updated, more precisely fitting option to the MDP.     

Hydrocarbon‐Rich Groundwater above Shale‐Gas Formations: A Karoo Basin Case Study

Horizontal drilling and hydraulic fracturing have enhanced unconventional hydrocarbon recovery but raised environmental concerns related to water quality. Because most basins targeted for shale‐gas development in the USA have histories of both active and legacy petroleum extraction, confusion about the hydrogeological context of naturally occurring methane in shallow aquifers overlying shales remains. The Karoo Basin, located in South Africa, provides a near‐pristine setting to evaluate these processes, without a history of conventional or unconventional energy extraction. We conducted a comprehensive pre‐industrial evaluation of water quality and gas geochemistry in 22 groundwater samples across the Karoo Basin, including dissolved ions, water isotopes, hydrocarbon molecular and isotopic composition, and noble gases. Methane‐rich samples were associated with high‐salinity, NaCl‐type groundwater and elevated levels of ethane, ⁴He, and other noble gases produced by radioactive decay. This endmember displayed less negative δ¹³C‐CH₄ and evidence of mixing between thermogenic natural gases and hydrogenotrophic methane. Atmospheric noble gases in the methane‐rich samples record a history of fractionation during gas‐phase migration from source rocks to shallow aquifers. Conversely, methane‐poor samples have a paucity of ethane and ⁴He, near saturation levels of atmospheric noble gases, and more negative δ¹³C‐CH₄; methane in these samples is biogenic and produced by a mixture of hydrogenotrophic and acetoclastic sources. These geochemical observations are consistent with other basins targeted for unconventional energy extraction in the USA and contribute to a growing data base of naturally occurring methane in shallow aquifers globally, which provide a framework for evaluating environmental concerns related to unconventional energy development (e.g., stray gas).     

The Effect of Undetected Barriers on Groundwater Drawdown and Recovery

In large-scale pumping projects, such as mine dewatering, predictions are often made about the rate of groundwater level recovery after pumping has ceased. However, these predictions may be impacted by geological uncertainty—including the presence of undetected impermeable barriers. During pumping, an impermeable barrier may be undetected if it is located beyond the maximum extent of the cone of depression; yet it may still control drawdown during the recovery phase. This has implications for regional-scale modeling and monitoring of groundwater level recovery. In this article, non-dimensional solutions are developed to show the conditions under which a barrier may be undetected during pumping but still significantly impact groundwater level recovery. The magnitude of the impact from an undetected barrier will increase as the ratio of pumping rate to aquifer transmissivity increases. The results are exemplified for a hypothetical aquifer with an unknown barrier 3 km from a pumping well. The difference in drawdown between a model with and without a barrier may be <1 m in the 10 years while pumping is occurring, but up to 50 m after pumping has ceased.     

A 6000 year water level history of Europe Lake, Wisconsin, USA

Europe Lake occupies a small, closed, basin that would have been an embayment in Lake Michigan during the high water level events in the larger lake. Cores recovered from the lake reveal late Holocene water level fluctuations in the basin that are inferred from changes in taxa and abundance of molluscs, ostracodes, magnetic susceptibility, organic carbon, and oxygen isotopes.Non-glacial, Holocene lacustrine/paludal sedimentation in this portion of the Europe Lake basin started after 6600 RCYBP and was probably initiated by a rise in the water table of the deep bedrock aquifer, during the Nipissing transgression in Lake Michigan. Isotopically light ground water from this source was probably a major contributor during this phase to the negative ¹⁸O spikes in Valvata tricarinata and Amnicola limosa.The start of stable lacustrine conditions is marked by maximum diversity of ostracode and mollusc taxa and a shift toward much more positive ¹⁸O values. The Europe Lake basin at this time became an embayment of Lake Michigan. This event was probably coeval with the peak of the Nipissing transgression, when the water plane reached an altitude of about 183 m.The isolation of Europe Lake from Lake Michigan started at about 2390 RCYBP and is probably due to a drop in water level in Lake Michigan and/or to isostatic uplift of the Door Peninsula. Since isolation from Lake Michigan, water levels in Europe lake have been controlled primarily by fluctuations in local precipitation, evaporation and ground water discharge.     

Coastal phytoplankton blooms in the Southern California Bight

Surface chlorophyll (CHL) measured at the Scripps Pier in the Southern California Bight (SCB) for 18 years (1983–2000) reveals that the spring bloom occurs with irregular timing and intensity each year, unlike sea-surface temperature (SST), which is dominated by a regular seasonal cycle. In the 1990s, the spring bloom occurred earlier in the year and with larger amplitudes compared to those of the 1980s. Seasonal anomalies of the Pier CHL have no significant correlation with local winds, local SST, or upwelling index, which implies that classical coastal upwelling is not directly responsible for driving chlorophyll variations in nearshore SCB.The annual mean Pier CHL exhibits an increasing trend, whereas the Pier SST has no evident concomitant trend during the CHL observation period. The interannual variation of the Pier CHL is not correlated with tropical El Niño or La Niña conditions over the entire observing period. However, the Pier CHL was significantly influenced by El Nino/Southern Oscillation during the 1997/1998 El Niño and 1998/1999 La Niña transition period. The Pier CHL is highly coherent at long periods (3–7 years) with nearby offshore in situ surface CHL at the CalCOFI (California Cooperative Fisheries Investigations) station 93.27.     

Using large‐scale climatic patterns for improving long lead time streamflow forecasts for Gunnison and San Juan River Basins

In a water‐stressed region, such as the western United States, it is essential to have long lead times for streamflow forecasts used in reservoir operations and water resources management. Current water supply forecasts provide a 3‐month to 6‐month lead time, depending on the time of year. However, there is a growing demand from stakeholders to have forecasts that run lead times of 1 year or more. In this study, a data‐driven model, the support vector machine (SVM) based on the statistical learning theory, was used to predict annual streamflow volume with a 1‐year lead time. Annual average oceanic–atmospheric indices consisting of the Pacific decadal oscillation, North Atlantic oscillation (NAO), Atlantic multidecadal oscillation, El Niño southern oscillation (ENSO), and a new sea surface temperature (SST) data set for the ‘Hondo’ region for the period of 1906–2006 were used to generate annual streamflow volumes for multiple sites in the Gunnison River Basin and San Juan River Basin, both located in the Upper Colorado River Basin. Based on the performance measures, the model showed very good forecasts, and the forecasts were in good agreement with measured streamflow volumes. Inclusion of SST information from the Hondo region improved the model's forecasting ability; in addition, the combination of NAO and Hondo region SST data resulted in the best streamflow forecasts for a 1‐year lead time. The results of the SVM model were found to be better than the feed‐forward, back propagation artificial neural network and multiple linear regression. The results from this study have the potential of providing useful information for the planning and management of water resources within these basins. Copyright © 2012 John Wiley & Sons, Ltd.     

Voronoi Meshing to Accurately Capture Geological Structure in Subsurface Simulations

Mathematical Geosciences - Mesh generation lies at the interface of geological modeling and reservoir simulation. Highly skewed or very small grid cells may be necessary to accurately capture the...     

Physical-Ecological Response of the California Current System to ENSO events in ROMS-NEMURO

Ocean Dynamics - We analyze the bottom-up El Niño/Southern Oscillation (ENSO) driven physical-biological response of the California Current System (CCS) in a high-resolution,...