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Research about New Hampshire

Source-linked reports with geographic coverage including New Hampshire.

At least 73 records · Page 4Linked to original sources
USGS2011

Geophysical and flow-weighted natural-contaminant characterization of three water-supply wells in New Hampshire

Three bedrock water-supply systems in New Hampshire were studied, using borehole geophysics and flow-weighted sampling techniques, to determine the sources and distribution of natural contaminants in water entering the boreholes and to assess whether borehole modifications might be used to reduce contaminant levels. Well water in more than 100 community water-supply systems in New Hampshire have natural contaminants, such as arsenic and uranium, above the U.S. Environmental Protection Agency maximum contaminant levels of 10 and 30 micrograms per liter, respectively. The water-system wells were studied to identify fractional contributions of natural contaminants from specific fracture zones. The yields and flow-weighted contaminant levels of such fracture zones were assessed to determine if a modification of the borehole might lead to a reduction in the system’s contaminant levels. The water-supply systems investigated were typical of small community water systems in New Hampshire where a water system may serve 100 connections or less. Each water system consisted of two wells, approximately 300 to 400 feet deep, in generally low-yielding (about 10 gallons per minute or less) crystalline bedrock. The wells were typically operated a few hours per day to fill a storage tank and had tens of feet of drawdown caused by the low well yields. The systems selected had contaminant concentrations slightly above MCL, or a low-level contamination. One of the water systems investigated had low-level (10 to 24 micrograms per liter) arsenic contamination, and two of the water systems had low-level uranium (30 to 40 micrograms per liter) contamination. The contaminant values were blended-water concentrations from the two wells in a system. Each water system had differences in contaminant concentrations between the two wells. In each case, the well with the greater concentration of the two was selected for investigation. In two of the three systems investigated, there was either not enough variation in the borehole contaminant concentration or not enough water-yielding fractures for borehole modifications to be a viable potential remedy to elevated contamination. However, borehole and contaminant conditions in one of the bedrock supply-well systems may be favorable to potential improvement of supplied water by borehole modification where selected fracture zones are sealed off from supplying water to the well.

New Hampshire↗
USGS2011

Analysis of the transport of sediment by the Suncook River in Epsom, Pembroke, and Allenstown, New Hampshire, after the May 2006 flood

During May 13-16, 2006, rainfall in excess of 8.8 inches flooded central and southern New Hampshire. On May 15, 2006, a breach in a bank of the Suncook River in Epsom, New Hampshire, caused the river to follow a new path. In order to assess and predict the effect of the sediment in, and the subsequent flooding on, the river and flood plain, a study by the U.S. Geological Survey (USGS) characterizing sediment transport in the Suncook River was undertaken in cooperation with the Federal Emergency Management Agency (FEMA) and the New Hampshire Department of Environmental Services (NHDES). The U.S. Army Corps of Engineers (USACE) Hydrologic Engineering Center-River Analysis System (HEC-RAS) model was used to simulate flow and the transport of noncohesive sediments in the Suncook River from the upstream corporate limit of Epsom to the river's confluence with the Merrimack River in the Village of Suncook (Allenstown and Pembroke, N.H.), a distance of approximately 16 miles. In addition to determining total sediment loads, analyses in this study reflect flooding potentials for selected recurrence intervals that are based on the Suncook River streamgage flow data (streamgage 01089500) and on streambed elevations predicted by HEC-RAS for the end of water year 2010 (September 30, 2010) in the communities of Epsom, Pembroke, and Allenstown. This report presents changes in streambed and water-surface elevations predicted by the HEC-RAS model using data through the end of water year 2010 for the 50-, 10-, 2-, 1-, 0.2-percent annual exceedence probabilities (2-, 10-, 50-, 100-, and 500-year recurrence-interval floods, respectively), calculated daily and annual total sediment loads, and a determination of aggrading and degrading stream reaches. The model was calibrated and evaluated for a 400-day span from May 8, 2008 through June 11, 2009; these two dates coincided with field collection of stream cross-sectional elevation data. Seven sediment-transport functions were evaluated in the model with the Laursen (Copeland) sediment-transport function best describing the sediment load, transport behavior, and changes in streambed elevation for the specified spatial and temporal conditions of the 400-day calibration period. Simulation results from the model and field-collected sediment data indicate that, downstream of the avulsion channel, for the average daily mean flow during the study period, approximately 100 to 400 tons per day of sediment (varying with daily mean flow) was moving past the Short Falls Road Bridge over the Suncook River in Epsom, while approximately 0.05 to 0.5 tons per day of sediment was moving past the Route 28 bridge in Pembroke and Allenstown, and approximately 1 to 10 tons per day was moving past the Route 3 bridge in Pembroke and Allenstown. Changes in water-surface elevation that the model predicted for the end of water year 2010 to be a result of changes in streambed elevation ranged from a mean increase of 0.20 feet (ft) for the 50-percent annual exceedence-probability flood (2-year recurrence-interval flood) due to an average thalweg increase of 0.88 ft between the Short Falls Road Bridge and the Buck Street Dams in Pembroke and Allenstown to a mean decrease of 0.41 ft for the 50-percent annual exceedence-probability flood due to an average thalweg decrease of 0.49 ft above the avulsion in Epsom. An analysis of shear stress (force created by a fluid acting on sediment particles) was undertaken to determine potential areas of erosion and deposition. Based on the median grain size (d50) and shear stress analysis, the study found that in general, for floods greater than the 50-percent annual exceedence probability flood, the shear stress in the streambed is greater than the critical shear stress in much of the river study reach. The result is an expectation of streambed-sediment movement and erosion even at high exceedence-probability events, pending although the stream ultimately attains equilibrium through stream-stabilization measures or the adjustment of the river over time. The potential for aggradation in the Suncook River is greatest in the reach downstream of the avulsion. Specifically, these reaches are (1) downstream of the former sand pit from adjacent to Round Pond to downstream of the flood chute at the large meander bends, and (2) downstream of the Short Falls Road Bridge to approximately 3,800 ft upstream of the Route 28 bridge. The potential for degradation-net lowering of the streambed-is greatest for the reach upstream of the avulsion to the Route 4 bridge.

New Hampshire↗
USGS2011

Geophysical bed sediment characterization of the Androscoggin River from the former Chlor-Alkali Facility Superfund Site, Berlin, New Hampshire, to the state border with Maine, August 2009

The former Chlor-Alkali Facility in Berlin, New Hampshire, was listed on the U.S. Environmental Protection Agency National Priorities List in 2005 as a Superfund site. The Chlor-Alkali Facility lies on the east bank of the Androscoggin River. Elemental mercury currently discharges from that bank into the Androscoggin River. The nature, extent, and the speciation of mercury and the production of methyl mercury contamination in the adjacent Androscoggin River is the subject of continuing investigations. The U.S. Geological Survey, in cooperation with Region I of the U.S. Environmental Protection Agency, used geophysical methods to determine the distribution, thickness, and physical properties of sediments in the Androscoggin River channel at a small area of an upstream reference reach and downstream from the site to the New Hampshire–Maine State border. Separate reaches of the Androscoggin River in the study area were surveyed with surface geophysical methods including ground-penetrating radar and step-frequency electromagnetics. Results were processed to assess sediment characteristics including grain size, electrical conductivity, and pore-water specific conductance. Specific conductance measured during surface- and pore-water sampling was used to help interpret the results of the geophysical surveys. The electrical resistivity of sediment samples was measured in the laboratory with intact pore water for comparison with survey results. In some instances, anthropogenic features and land uses, such as roads and power lines affected the detection of riverbed properties using geophysical methods; when this occurred, the data were removed. Through combining results, detailed riverbed sediment characterizations were made. Results from ground-penetrating radar surveys were used to image and measure the depth to the riverbed, depth to buried riverbeds, riverbed thickness and to interpret material-type variations in terms of relative grain size. Fifty two percent of the riverbed in the study area was covered with gravel and finer sediments. The electrically resistive river water and sediment in this study area were conducive to the penetration of the ground-penetrating radar and step-frequency electromagnetic signals and allowed for effective sediment characterization by geophysical methods. The reach between the former Chlor-Alkali Facility and the Riverside Dam, had small areas of fine sediment (estimated 11 percent of riverbed area), found on the upstream left bank and the downstream right bank, with an electromagnetic conductivity (31.4 millisiemens per meter (mS/m) maximum) that was higher than the upstream reference reach. The greatest electromagnetic conductivity (195 mS/m), pore-water specific conductance (324 mS/m) and lab measured sediment conductivity of (76.8 mS/m, measured with a direct-current resistivity test box) in the study were measured approximately 1 mile (mi) downstream of the site from a sandbar on the left bank. Reaches adjacent to and within 2 mi downstream from the site had elevated electromagnetic conductivity despite having lower estimated percentages of riverbed area covered in sediment (11, 25, and 61 percent, respectively) than the reference reach (97). Typically finer grained sediment with similar mineralogy will be more conductive. The Shelburne Reservoir is approximately 8 mi downstream from the site had the second greatest pore-water specific conductance measured, 45.8 mS/m. Many of the locations with the largest step-frequency electromagnetic values have not been sampled for pore water and sediment.

New Hampshire↗
USGS2011

Changes in monoterpene mixing ratios during summer storms in rural New Hampshire (USA)

Monoterpenes are an important class of biogenic hydrocarbons that influence ambient air quality and are a principle source of secondary organic aerosol (SOA). Emitted from vegetation, monoterpenes are a product of photosynthesis and act as a response to a variety of environmental factors. Most parameterizations of monoterpene emissions are based on clear weather models that do not take into account episodic conditions that can drastically change production and release rates into the atmosphere. Here, the monoterpene dataset from the rural Thompson Farm measurement site in Durham, New Hampshire is examined in the context of a set of known severe storm events. While some storm systems had a negligible influence on ambient monoterpene mixing ratios, the average storm event increased mixing ratios by 0.59 ± 0.21 ppbv, a factor of 93 % above pre-storm levels. In some events, mixing ratios reached the 10’s of ppbv range and persisted overnight. These mixing ratios correspond to increases in the monoterpene emission rate, ranging from 120 to 1240 g km−2 h −1 compared to an estimated clear weather rate of 116 to 193 g km−2 h −1 . Considering the regularity of storm events over most forested areas, this could be an important factor to consider when modeling global monoterpene emissions and their resulting influence on the formation of organic aerosols.

New Hampshire↗
USGS2011

Demonstration/validation of the Snap sampler passive groundwater sampling device

Laboratory studies and a field demonstration were conducted to determine the ability of the Snap Sampler to recover representative concentrations of several types of inorganic analytes from ground water. Analytes included non-metals, transition metals, alkaline earth metals, alkali metals, and a metalloid. In the laboratory studies, concentrations of analytes in Snap Sampler samples were com-parable with concentrations of the analytes in samples collected from a standpipe (i.e., control samples). For the field demonstration, there were sampling events at the former Pease Air Force Base. Samples taken using a Snap Sampler were compared with samples collected using conventional low-flow purging and sampling and a regenerated cellulose passive diffusion sampler. Based upon statistical analyses, analyte concentrations were found to be equivalent to those in the low-flow samples with one exception – unfiltered iron, where concentrations were significantly higher in the Snap Sampler samples. Differences were most pronounced in samples collected from the two stainless steel wells and from wells with higher turbidity levels. Elevated turbidities may have resulted from installing additional sampling equipment (including the baffle, pump, samplers, and bottom weight) in the well before sampling. We will examine this issue further at our next test site.

New Hampshire↗
USGS2010

Earthquake refraction profiles of the root of the Sierra Nevada

We examine the seismic structure of the Sierra Nevada using records of nine earthquakes and one explosion in and near the Sierra, recorded on stations in the Sierra. We first interpret travel times from these paths, which are confined to a single tectonic block, in terms of one‐dimensional structures. The most nearly reversed pair of earthquakes, the 1966 Truckee and 1983 Durrwood Meadows earthquakes, share refracted ( P n ) arrival times (corrected to surface focus) along a line t =8.75±0.25+Δ/8.0, suggesting that a nearly flat layer of 8.0 km/s mantle material lies at depths of 46–48 km. First arrivals from these events do not constrain velocities from ≈30 to 45 km depth. Secondary arrivals and some first arrivals from other earthquakes suggest that velocities in part of this region range between 6.9 and 7.8 km/s. The presence of this “7.x‐km/s” layer can help to explain previous contradictory observations. The 7.x‐km/s layer could be interpreted as either the mafic bottom of a silicic, Mesozoic magmatic arc or as accreted mafic underplating or rejuvenated mantle related to Cenozoic arc volcanism or Basin and Range spreading. Arrivals at stations in the foothills and the crest of the Sierra cannot be fit with a single longitudinal structure, indicating a lateral variation of velocity structure. These variations support previously inferred variations of lithospheric structure, with higher‐velocity, thinner crust to the west beneath the Sierran foothills and slower‐velocity crust (or possibly upper mantle) beneath the high mountains in the eastern Sierra. Rapid changes in arrival times between stations separated by short distances in the eastern Sierra suggest that a sharp boundary exists between the Sierra and the Basin and Range at Moho depths. We also present fresh evidence of the asymmetry of the root of the Sierra, wherein arrivals from earthquakes on the west of the Sierra are delayed within the Sierra and return to original values in the Basin and Range, while arrivals from earthquakes and explosions from the Sierra into the Great Valley. We suggest that if the 7.x‐km/s material occurs in a wedge above the Moho, then the asymmetry can be explained by arrivals from the west being delayed by the dipping 8.0‐km/s Moho, while those from the east may be entering the root along a 7.x‐km/s layer that is near the depth of the Basin and Range Moho.

New Hampshire↗
USGS2010

Delineating a road-salt plume in lakebed sediments using electrical resistivity, piezometers, and seepage meters at Mirror Lake, New Hampshire, U.S.A

Electrical-resistivity surveys, seepage meter measurements, and drive-point piezometers have been used to characterize chloride-enriched groundwater in lakebed sediments of Mirror Lake, New Hampshire, U.S.A. A combination of bottom-cable and floating-cable electrical-resistivity surveys identified a conductive zone ( &lt; 100 ohm- m ) "> ( < 100 ohm- m ) (<100ohm-m) overlying resistive bedrock ( &lt; 1000 ohm- m ) "> ( < 1000 ohm- m ) (<1000ohm-m) beneath the lake. Shallow pore-water samples from piezometers in lakebed sediments have chloride concentrations of 200 &#x2013; 1800 &#x3BC; eq / liter "> 200 – 1800 μ eq / liter 200–1800μeq/liter , and lake water has a chloride concentration of 104 &#x3BC; eq / liter "> 104 μ eq / liter 104μeq/liter . The extent of the plume was estimated and mapped using resistivity and water-sample data. The plume ( 20 &#xD7; 35 m "> 20 × 35 m 20×35m wide and at least 3 m "> 3 m 3m thick) extends nearly the full length and width of a small inlet, overlying the top of a basin formed by the bedrock. It would not have been possible to mapthe plume's shape without the resistivity surveys because wells provided only limited coverage. Seepage meters were installed approximately 40 m "> 40 m 40m from the mouth of a small stream discharging at the head of the inlet in an area where the resistivity data indicated lake sediments are thin. These meters recorded in-seepage of chloride-enriched groundwater at rates similar to those observed closer to shore, which was unexpected because seepage usually declines away from shore. Although the concentration of road salt in the northeast inlet stream is declining, the plume map and seepage data indicate the groundwater contribution of road salt to the lake is not declining. The findings demonstrate the benefit of combining geophysical and hydrologic data to characterize discharge of a plume beneath Mirror Lake. The extent of the plume in groundwater beneath the lake and stream indicate there will likely be a long-term source of chloride to the lake from groundwater.

New Hampshire↗
USGS2010

Hydrostratigraphic mapping of the Milford-Souhegan glacial drift aquifer, and effects of hydrostratigraphy on transport of PCE, Operable Unit 1, Savage Superfund Site, Milford, New Hampshire

The Savage Municipal Well Superfund site in the Town of Milford, New Hampshire, was underlain by a 0.5-square mile plume (as mapped in 1994) of volatile organic compounds (VOCs), most of which consisted of tetrachloroethylene (PCE). The plume occurs mostly within highly transmissive stratified-drift deposits but also extends into underlying till and bedrock. The plume has been divided into two areas called Operable Unit 1 (OU1), which contains the primary source area, and Operable Unit 2 (OU2), which is defined as the extended plume area outside of OU1. The OU1 remedial system includes a low-permeability barrier wall that encircles the highest detected concentrations of PCE and a series of injection and extraction wells to contain and remove contaminants. The barrier wall likely penetrates the full thickness of the sand and gravel; in many places, it also penetrates the full thickness of the underlying basal till and sits atop bedrock. From 1998 to 2004, PCE concentrations decreased by an average of 80 percent at most wells outside the barrier wall. However, inside the barrier, PCE concentrations greater than 10,000 micrograms per liter (μg/L) still exist (2008). The remediation of these areas of recalcitrant PCE presents challenges to successful remediation. The U.S. Geological Survey (USGS), in cooperation with the New Hampshire Department of Environmental Services (NHDES) and the U.S. Environmental Protection Agency (USEPA), Region 1, is studying the solute transport of VOCs (primarily PCE) in contaminated groundwater in the unconsolidated sediments (overburden) of the Savage site and specifically assisting in the evaluation of the effectiveness of remedial operations in the OU1 area. As part of this effort, the USGS analyzed the subsurface stratigraphy to help understand hydrostratigraphic controls on remediation. A combination of lithologic, borehole natural gamma-ray and electromagnetic (EM) induction logging, and test drilling has identified 11 primary hydrostratigraphic units in OU1. These 11 units consist of several well-sorted sandy layers with some gravel that are separated by poorly sorted cobble layers with a fine-grained matrix. Collectively these units represent glacial sediments deposited by localized ice-margin fluctuations. For the most part, the units are semi-planar, particularly the cobble units, and truncated by an undulating bedrock surface. The lowermost unit is a basal till that ranges in thickness from zero to greater than 10 feet and mantles the bedrock surface. The 11 units have different lithologic and hydraulic characteristics. The hydraulic conductivity of the well-sorted sand and gravel units is typically greater than the conductivity of the poorly sorted cobble units and the basal till. The hydraulic conductivity ranges from 5 to greater than 500 feet per day. Lateral and vertical variation in lithology and hydraulic conductivity are inferred by variations in borehole natural gamma-ray counts and estimates of hydraulic conductivity. The comparison of hydrostratigraphic units with the spatial distribution of PCE concentrations suggests that solute transport away from source areas is primarily lateral within the permeable sandy units in the middle to lower parts of the aquifer. Along the centerline of the interior barrier area, highest PCE concentrations are in the sandy units to the east of suspected source areas.

New Hampshire↗
USGS2010

Preliminary assessment of trends in static water levels in bedrock wells in New Hampshire, 1984 to 2007

Analysis of nearly 60,000 reported values of static water level (SWL, as depth below land surface) in bedrock wells in New Hampshire, aggregated on a yearly basis, showed an apparent deepening of SWL of about 13 ft (4 m) over the period 1984&ndash;2007. Water-level data were one-time measurements at each well and were analyzed, in part, to determine if they were suitable for analysis of trends in groundwater levels across the state. Other well characteristics, however, also have been changing over time, such as total well depth, casing length, the length of casing in bedrock, and to some extent, well yield. Analyses indicated that many of the well construction variables are significantly correlated; the apparent declines in water levels may have been caused by some of these factors. Information on changes in water use for the period was not available, although water use may be an important factor affecting water levels. Multiple regression models were used to determine the simultaneous effects of important variables on SWLs statewide. Models also were generated for each county, and the model-calculated results for counties were generally similar to the results for the state wide models. The most significant predictors of mean SWL (aggregated by year and quarter) were total depth, the third quarter of the year (July&ndash;September), elevation, and height of well above minimum elevation within a 1,640-foot (500-meter) radius (hillslope factor). Casing length was a significant predictor of SWL for igneous-rock models and curvature of the land surface for metamorphic-rock models. Local geologic as well as landscape features appear to provide further explanation of SWL variation. For example, SWLs in wells completed in specific granites appear to be deeper than in other granites; this relation was also observed for different groups of metamorphic rocks. A more detailed examination of data from six towns that report frequent complaints about low water supply from bedrock aquifer wells showed that hillslope position may play a role in the availability of water in wells. SWLs were commonly deeper (greater depth to water) for wells with more than 100 ft (30 m) of relief between the well and the lowest land-surface elevation within 1,640 ft (500 m) of the well. For these high-relief wells, the depth to SWL was commonly greater for those that were on generally south-facing slopes, compared to wells on north-facing slopes. Concerns about wells with very little water-producing capacity in localized areas of some towns may be better understood by considering some of the relations identified in this study. For example, the data show that the position of a well on a hillslope affects the SWL depth in that well; however, the data also indicate that the average yield of the well is lower for hillslope wells than for wells in lower relief areas. This relation indicates that as the hillslope factor increases (and SWLs become deeper), the amount of available water in the wells decreases. Knowledge of this relation indicates that deeper wells may be needed in areas of higher relief. In areas with less extreme relief, the overall depths of wells have increased substantially more than the depths to the SWL. This indicates that the amount of water stored in wells (wellbore storage) has increased, and thus more water is available for use in the average well. As a result, more water may be used because it is available, possibly adding to the problem of local well interference or exacerbating drought-related well problems. These data provided an opportunity to examine groundwater-level conditions across the state; however, the bedrock wells used in this study would not be suitable for rigorous evaluation of trends in SWL across the state because the locations and characteristics of the wells vary with time. Further, these wells cannot substitute for a carefully designed network of wells selected for the sole purpose of monitoring trends in water levels over time. The SWL data may be useful in the design of a monitoring network, and continued collection of water-level data from the bedrock wells could be used to augment data from monitoring wells.

New Hampshire↗
USGS2009

Hydrologic processes and the water budget: Chapter 2

This chapter focuses on the hydrological setting of Mirror Lake and its water budget. It first describes the glacial deposits and bedrock topography in the Mirror Lake area. It then provides an overview of the hydrologic processes associated with Mirror Lake and examines the field and analytical methods used to determine its water budget. It presents results from the hydrologic studies, which are based on monthly and annual water budgets for the calendar years 1981 through 2000.

New Hampshire↗
USGS2009

Evaluation of methods and uncertainties in the water budget

Water budget studies of Mirror Lake aim to measure hydrologic components interacting with the lake as accurately as possible. However, measurements of water budget components are subject to some degree of uncertainty. This chapter describes the methods used to quantify water budget components of Mirror Lake in detail. It examines uncertainties in precipitation values, monthly evaporation, water flows, and exchange with groundwater. It shows how those values were derived, including the assumptions that went into the calculations and the uncertainties inherent in the values.

New Hampshire↗
USGS2009

Evaluation of methods and uncertainties in the chemical budgets

This chapter examines the uncertainties inherent in the water and chemical budgets of the lake in relation to the differences between chemical mass change in storage and to the balance between solute inputs and solute outputs associated with water fluxes. It begins by discussing uncertainty in the water budgets used to determine chemical budgets. It then examines uncertainties in chemical analyses of precipitation samples, surface water samples, and groundwater samples. It also discusses alternative approaches to determining chemical budgets. It describes the methods used to calculate chemical mass input from the tributaries, chemical mass loss by surface outflow, chemical mass input from groundwater, and chemical mass loss by flow through groundwater.

New Hampshire↗
USGS2009

Mirror Lake: Past, present and future

This chapter discusses the hydrological and biogeochemical characteristics of Mirror Lake and the changes that resulted from air-land-water interactions and human activities. Since the formation of Mirror Lake, both the watershed and the lake have undergone many changes, such as vegetation development and basin filling. These changes are ongoing, and Mirror Lake is continuing along an aging pathway and ultimately, it will fill with sediment and no longer be a lake. The chapter also identifies major factors that affected the hydrology and biogeochemistry of Mirror Lake: acid rain, atmospheric deposition of lead and other heavy metals, increased human settlement around the lake, the construction of an interstate highway through the watershed of the Northeast Tributary, the construction of an access road through the West and Northeast watersheds to the lake, and climate change. The chapter also offers future recommendations for management and protection of Mirror Lake.

New Hampshire↗
USGS2007

Evaluation of inflow to Mirror Lake, New Hampshire

Measured stream discharge plus calculated ground water discharge (total measured runoff) were compared with runoff calculated by the unit-runoff method for the two largest watersheds of Mirror Lake for 1981–1983. Runoff calculated by the unit-runoff method, using Hubbard Brook watershed 3 as the index watershed, was greater than the total measured runoff into Mirror Lake during periods of high flow and slightly less than the total measured runoff into Mirror Lake during periods of low flow. Annual calculated unit runoff was 17 to 37 percent greater than total measured runoff. Differences in monthly runoff are far greater, ranging from 0 to greater than 100 percent. For high flows the calculated unit runoff is about 2 times greater than total measured runoff. For low flows the northwest basin of Mirror Lake has the greatest ground water contribution compared to the other two basins. In contrast, Hubbard Brook watershed 3 has the least ground water contribution.

New Hampshire↗
USGS2007

The Piermont allochthon revisited and redefined at its type locality: Discussion

Timms (2004) has presented a very restricted interpretation of an important structural feature in the New England Appalachians that I originally termed the Piermont allochthon and interpreted as a far-traveled Acadian thrust sheet (Moench et al., 1987; Moench, 1990). As described herein, subsequent mapping has led me to a very different conclusion that, whether right or wrong, is crucial to understand because it bears directly on how we interpret northern Appalachian tectonics for Late Ordovician to Early Devonian time (see also Billings [1992] and Moench [1992]). Figures 1 and 2 of this paper and 2 and 3 of Timms (2004), at the same scale, are vastly different depictions of stratigraphy and structure at the very southern tip of the Piermont “allochthon” (quotes mine), which I now term the Piermont-Frontenac parautochthon. Timms appears to have been unaware of my concurrent work in the area and the evolution of my understanding of the Piermont-Frontenac parautochthon since the 1990s, which is discussed below.

New Hampshire↗
USGS2007

Comparison of 15 evaporation methods applied to a small mountain lake in the northeastern USA

Few detailed evaporation studies exist for small lakes or reservoirs in mountainous settings. A detailed evaporation study was conducted at Mirror Lake, a 0.15 km2 lake in New Hampshire, northeastern USA, as part of a long-term investigation of lake hydrology. Evaporation was determined using 14 alternate evaporation methods during six open-water seasons and compared with values from the Bowen-ratio energy-budget (BREB) method, considered the standard. Values from the Priestley-Taylor, deBruin-Keijman, and Penman methods compared most favorably with BREB-determined values. Differences from BREB values averaged 0.19, 0.27, and 0.20 mm d-1, respectively, and results were within 20% of BREB values during more than 90% of the 37 monthly comparison periods. All three methods require measurement of net radiation, air temperature, change in heat stored in the lake, and vapor pressure, making them relatively data intensive. Several of the methods had substantial bias when compared with BREB values and were subsequently modified to eliminate bias. Methods that rely only on measurement of air temperature, or air temperature and solar radiation, were relatively cost-effective options for measuring evaporation at this small New England lake, outperforming some methods that require measurement of a greater number of variables. It is likely that the atmosphere above Mirror Lake was affected by occasional formation of separation eddies on the lee side of nearby high terrain, although those influences do not appear to be significant to measured evaporation from the lake when averaged over monthly periods.

New Hampshire↗
USGS2007

Geological assessment of cores from the Great Bay National Wildlife Refuge, New Hampshire

Geological sources of metals (especially arsenic and zinc) in aquifer bedrock were evaluated for their potential to contribute elevated values of metals to ground and surface waters in and around Rockingham County, New Hampshire. Ayotte and others (1999, 2003) had proposed that arsenic concentrations in ground water flowing through bedrock aquifers in eastern New England were elevated as a result of interaction with rocks. Specifically in southeastern New Hampshire, Montgomery and others (2003) established that nearly one-fifth of private bedrock wells had arsenic concentrations that exceed the U.S. Environmental Protection Agency (EPA) maximum contamination level for public water supplies. Two wells drilled in coastal New Hampshire were sited to intersect metasedimentary and metavolcanic rocks in the Great Bay National Wildlife Refuge. Bulk chemistry, mineralogy, and mineral chemistry data were obtained on representative samples of cores extracted from the two boreholes in the Kittery and Eliot Formations. The results of this study have established that the primary geologic source of arsenic in ground waters sampled from the two well sites was iron-sulfide minerals, predominantly arsenic-bearing pyrite and lesser amounts of base-metal-sulfide and sulfosalt minerals that contain appreciable arsenic, including arsenopyrite, tetrahedrite, and cobaltite. Secondary minerals containing arsenic are apparently limited to iron-oxyhydroxide minerals. The geologic source of zinc was sphalerite, typically cadmium-bearing, which occurs with pyrite in core samples. Zinc also occurred as a secondary mineral in carbonate form. Oxidation of sulfides leading to the liberation of acid, iron, arsenic, zinc, and other metals was most prevalent in open fractures and vuggy zones in core intervals containing zones of high transmissivity in the two units. The presence of significant calcite and lesser amounts of other acid-neutralizing carbonate and silicate minerals, acting as a natural buffer to reduce acidity, forced precipitation of iron-oxyhydroxide minerals and the removal of trace elements, including arsenic and lead, from ground waters in the refuge. Zinc may have remained in solution to a greater extent because of complexing with carbonate and its solubility in near-neutral ground and surface waters. The regional link between anomalously high arsenic contents in ground water and a bedrock source as established by Ayotte and others (1999, 2003) and Montgomery and others (2003) was confirmed by the presence of some arsenic-bearing minerals in rocks of the Kittery and Eliot Formations. The relatively low amounts of arsenic and metals in wells in the Great Bay National Wildlife Refuge as reported by Ayotte and others (U.S. Geological Survey Water Resources Data, 2005) were likely controlled by local geochemical environments in partially filled fractures, fissures, and permeable zones within the bedrock formations. Carbonate and silicate gangue minerals that line fractures, fissures, and permeable zones likely limited the movement of arsenic from bedrock to ground water. Sources other than the two geologic formations might have been required to account for anomalously high arsenic contents measured in private bedrock aquifer wells of Rockingham County.

New Hampshire↗