Samples from rain collectors were collected when enough daily precipitation accumulated in the collectors. Sampled precipitation events during the study period were in May, June, July, August, and September 2018. Physical properties of sampled water-temperature, pH, and specific conductance-were measured in the field. Water samples were analyzed for stable isotopes of oxygen and hydrogen and for chloride concentration. Recharge rates for aquifers supplying springs were determined using precipitation volume and chloride concentrations for a 12-day period before the sample-collection date. Multivariate statistical analysis methods used on water-chemistry data included principal component analysis, cluster analysis, and end-member mixing analysis. Water composition was used to determine the spring type and contributing aquifers for 11 springs in the North and South Units of Theodore Roosevelt National Park from analyses of water-chemistry data between May and September 2018. In the North Unit, Achenbach Spring was classified as a filtration spring with water from an unconfined part of the upper Fort Union aquifer and infiltration of precipitation. Hagen Spring, Mandal Spring, and Stevens Spring were classified as contact springs supplied by semiconfined parts of the upper Fort Union aquifer. Overlook Spring at one time may have been a natural spring or seep but now is a developed spring that behaves like a flowing artesian well completed in a confined part of the upper Fort Union aquifer. In the South Unit, six springs were classified into two spring types: filtration and contact springs. Boicourt Spring and Sheep Butte Spring were classified as filtration springs that have water supplied by unconfined parts of the upper Fort Union aquifer and infiltrated precipitation. Big Plateau Spring, Lone Tree Spring, Sheep Pasture Spring, and Southeast Corner Spring were classified as contact springs that receive waters from a semiconfined part of the upper Fort Union aquifer. from the ground and flows or forms pools (Bryan, 1919). Springs commonly form when the side of a hill, a valley bottom, or other excavations intersect flowing groundwater at or below the local water table (U.S. Geological Survey, 2019). Seeps are a type of spring in which the water flows from pores in the ground over considerable areas (Bryan, 1919). Seeps occur from a slow movement of water through Unconfined aquifer water table Unconfined aquifer water table Rotational slump or landslide Low permeability unit Low permeability unit EXPLANATION Spring Groundwater level Groundwater flow direction Filtration Confined aquifer hydraulic head Confined aquifer hydraulic head spring or seep Flowing artesian spring Upper contact spring Lower contact spring Figure 3. Types of springs in the study area.
In 2009 the United States completed an 80% reduction of its operationally deployed strategic nuclear weapons from Cold War highs. Since 1991, the United States also reduced its non-strategic nuclear weapons by over 90%. Additionally, the United States removed much of its nuclear arsenal from alert status and continues to drawdown its nuclear weapons stockpiles. However, nuclear weapons may still play an important role in deterring an adversary attack against the United States and in providing a nuclear umbrella to allies. In fact, an extended nuclear deterrent for protecting allies also may contribute significantly to nonproliferation effortsthe nuclear umbrella provides an assurance to allies so they do not perceive the need to develop nuclear weapons arsenals for themselves. This paper explores the impact of US nuclear weapons policy on the current and future effectiveness of extended nuclear deterrence for the Republic of Turkey. It concludes that the credibility of US extended nuclear deterrence for Turkey depends on many factors and not just the quality and quantity of the US nuclear arsenal.
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The City of Deadwood, South Dakota, has been working on a new archeological investigation in preparation for economic growth and expansion within the city limits, through the Deadwood Historic Preservation Office. During the excavation process, buried artifacts and historical features from the late 1800s have been uncovered. The stratigraphy of shallow unconsolidated deposits in the city of Deadwood, S. Dak., was surveyed on January 29, 2020, using real-time kinematic survey methods and described to identify variations in geologic material, thickness, and depth from the land surface in support of archeological studies by the city. The findings of the study will provide city managers and the public with reliable and impartial information for their use by advancing field or analytical methodology and understanding of hydrologic processes in the study area. The primary excavation site was surveyed, and stratigraphic units were delineated from changes in material properties or depositional environment. The primary excavation site consisted of nine stratigraphic units; however, some units were not consistent along the length of the excavation and pinched out along the cross section. Survey data points also were collected for artifacts and other sites of interest. The shallow surficial geology in the study area was affected by human construction, fires, and flooding.
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