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At least 199 records · Page 11Linked to original sources
USGS2006

Factors Affecting Firm Yield and the Estimation of Firm Yield for Selected Streamflow-Dominated Drinking-Water-Supply Reservoirs in Massachusetts

Factors affecting reservoir firm yield, as determined by application of the Massachusetts Department of Environmental Protection's Firm Yield Estimator (FYE) model, were evaluated, modified, and tested on 46 streamflow-dominated reservoirs representing 15 Massachusetts drinking-water supplies. The model uses a mass-balance approach to determine the maximum average daily withdrawal rate that can be sustained during a period of record that includes the 1960s drought-of-record. The FYE methodology to estimate streamflow to the reservoir at an ungaged site was tested by simulating streamflow at two streamflow-gaging stations in Massachusetts and comparing the simulated streamflow to the observed streamflow. In general, the FYE-simulated flows agreed well with observed flows. There were substantial deviations from the measured values for extreme high and low flows. A sensitivity analysis determined that the model's streamflow estimates are most sensitive to input values for average annual precipitation, reservoir drainage area, and the soil-retention number-a term that describes the amount of precipitation retained by the soil in the basin. The FYE model currently provides the option of using a 1,000-year synthetic record constructed by randomly sampling 2-year blocks of concurrent streamflow and precipitation records 500 times; however, the synthetic record has the potential to generate records of precipitation and streamflow that do not reflect the worst historical drought in Massachusetts. For reservoirs that do not have periods of drawdown greater than 2 years, the bootstrap does not offer any additional information about the firm yield of a reservoir than the historical record does. For some reservoirs, the use of a synthetic record to determine firm yield resulted in as much as a 30-percent difference between firm-yield values from one simulation to the next. Furthermore, the assumption that the synthetic traces of streamflow are statistically equivalent to the historical record is not valid. For multiple-reservoir systems, the firm-yield estimate was dependent on the reservoir system's configuration. The firm yield of a system is sensitive to how the water is transferred from one reservoir to another, the capacity of the connection between the reservoirs, and how seasonal variations in demand are represented in the FYE model. Firm yields for 25 (14 single-reservoir systems and 11 multiple-reservoir systems) reservoir systems were determined by using the historical records of streamflow and precipitation. Current water-use data indicate that, on average, 20 of the 25 reservoir systems in the study were operating below their estimated firm yield; during months with peak demands, withdrawals exceeded the firm yield for 8 reservoir systems.

Scientific Investigations Report↗
USGS2023

Nitrogen isotopes indicate vehicle emissions and biomass burning dominate ambient ammonia across Colorado's Front Range urban corridor

Urban ammonia (NH 3 ) emissions contribute to poor local air quality and can be transported to rural landscapes, impacting sensitive ecosystems. The Colorado Front Range urban corridor encompasses the Denver Metropolitan Area, rural farmland/rangeland and montane forest between the city and the Rocky Mountains. Reactive nitrogen emissions from the corridor are partly responsible for increased N deposition to the wildland-urban interface (WUI) in this region. To determine the significance of individual NH 3 sources to WUI ecosystems, we measured the concentration and isotopic composition (δ 15 N–NH 3 ) of ambient NH 3(g) from April to October 2018 across a five-site urban to rural gradient in the corridor. The urban sites had higher NH 3 concentrations and δ 15 N–NH 3 values than the rural/suburban sites. Based on isotope mixing models, NH 3 emission source contributions for all sites were fertilizer (12 ± 5.7%), livestock waste (18 ± 12%), vehicles (37 ± 23%), and biomass burning (34 ± 20%). Vehicle contributions were consistent across all months with an average of 35% and summer months showed a peak in biomass burning contributions (40%). As wildfires are projected to increase due to climate change, we stress a need for constraints on the isotopic signature of NH 3 emitted from wildfires. Vehicle emissions contributed the greatest amount of NH 3 (40%) at the urban sites while rural/suburban sites had higher agricultural contributions (41%). Had 2018 not had an anomalously high wildfire season, 46% and 60% of the NH 3 would have been attributed to vehicle emissions at the WUI site and urban sites, respectively. NH 3 emissions have historically been ascribed to agricultural activities but these findings illustrate the universal significance of vehicle emissions and the potential for sustained wildfire activity to be a primary contributor to NH 3 . Air quality (e.g., particulate matter) and nitrogen deposition reduction plans may benefit by including management practices that address vehicle NH 3 emissions.

Colorado↗
USGS1992

Water resources and aquifer yields in the Charles River basin, Massachusetts

In 1984, about 66 Mgal/d (million gallons per day) of municipally supplied water was used by towns in the middle and upper Charles River basin and by the city of Cambridge in the lower basin. The Division of Water Resources of the Massachusetts Department of Environmental Management estimates that by the year 2020 an additional 11 Mgal/d of water will be needed to meet demands. The largest sources of un used water in the basin are 15 stratified-drift aquifers along the Charles River that are hydraulically con nected to the river and to its major tributaries. These aquifers, which consist mainly of medium to coarse sand and gravel, are generally unconfined, narrow, and discontinuous. They are as much as 100 feet thick, and transmissivity ranges from about 1,000 to 25,000 cubic feet per day per square foot times foot of aquifer thickness. The depth to the water table from the land surface generally is less than 15 feet and the water table fluctuates about 3 to 5 feet annually. Recharge to the aquifers is mostly derived from precipita tion, and the aquifers continuously discharge ground water to streams, ponds, lakes, and wetlands. Aquifer yields from the 15 aquifers under normal climatic conditions were related to the estimated duration of flow of the streams that drain the aquifers. Long-term (180 days or more) aquifer yields that are derived from interception of ground-water discharge range from less than 1 to more than 5 Mgal/d at the streamflow that is exceeded 95 percent of the time. However, because withdrawal may reduce streamflow in the Charles River to unacceptable levels, these yield estimates were adjusted to meet commonly cited minimum-streamflow criteria. For example, if minimum streamflows in the Charles River are maintained at no less than the annual 7-day, 10-year, mean low flow for 95 percent of the time, only three of the 15 aquifers could sustain yields of more than 1 Mgal/d from intercepted ground-water discharge. However, none of the aquifers could yield an appreciable amount of water from this source if streamflows are maintained at no less than this minimum for 99 percent of the time. Yields also are available to wells front water in duced by pumping to infiltrate through a streambed. Yields front induced infiltration from the Charles River were estimated for four aquifers and range from about 4 to 11 Mgal/d at the 95-percent flow duration. If minimum-streamflow criteria are to be maintained, these yield estimates would be substantially lower. A streamflow-accounting model was used to demonstrate the possible streamflow reductions that could result from further development of the water resources of the middle and upper Charles River basin. Results indicate that pumpage of an additional 11 Mgal/d could reduce flow in the river at Waltham by about 6 ft 3 /s (cubic feet per second) (4 Mgal/d) throughout the year--alt amount equal to about 24 percent of the flow that is exceeded 95 percent of the time. Also, model results indicate that increases in punzpage and the export of was-tewater from the basin of 23 Mgal/d would reduce streamflow at Waltham by about 14 ft 3 / s (9 Mgal/d) throughout the year.

Massachusetts↗
USGS2015

Water-level conditions in the confined aquifers of the New Jersey Coastal Plain, 2008

Groundwater-level altitudes in 10 confined aquifers of the New Jersey Coastal Plain were measured and evaluated to provide an overview of regional groundwater conditions during fall 2008. Water levels were measured in more than 900 wells in New Jersey, eastern Pennsylvania, and northern Delaware and potentiometric surface maps prepared for the confined Cohansey aquifer of Cape May County, the Rio Grande water-bearing zone, the Atlantic City 800-foot sand, the Piney Point, Vincentown, and the Wenonah-Mount Laurel aquifers, the Englishtown aquifer system, and the Upper, Middle, and Lower aquifers of the Potomac-Raritan-Magothy aquifer system. In 2008, the highest water-level altitudes were observed in the Vincentown aquifer (median, 78 ft) and the lowest in the Atlantic City 800-foot sand (median, -45 ft). Persistent, regionally extensive cones of depression were present within the potentiometric surfaces of the Englishtown aquifer system in east-central New Jersey, the Wenonah-Mount Laurel aquifer in east-central and southern New Jersey, the Upper, Middle, and Lower Potomac-Raritan-Magothy aquifers in southern New Jersey, and the Atlantic City 800-foot sand in the southeastern part of the State. Cones of depression in the potentiometric surfaces of the Upper Potomac-Raritan-Magothy and the Piney Point aquifers in east-central and southwestern New Jersey had broadened and deepened since 2003. Declining water levels in many of New Jersey’s confined Coastal Plain aquifers intensified during the late 1970s and early 1980s, prompting the designation of two water-supply Critical Areas by the New Jersey Department of Environmental Protection; Critical Areas 1 and 2 continued to be of concern. To address that concern, water-level changes were assessed in nearly 800 wells measured during the fall of 2003 and 2008, and potentiometric-surface difference maps for each aquifer were constructed and evaluated. In addition, water-level trends were calculated for 77 wells for the periods 2003–8 and 1998–2008 and for 73 wells for the period 1978–2008. From 2003 to 2008 small to moderate water-level changes were observed in many Coastal Plain aquifers in New Jersey, but in places, groundwater levels continued to decline substantially as a result of pumping. Groundwater levels in the Atlantic City 800-foot sand were lower in 2008 than in 2003; declines were greatest near pumping centers in eastern Atlantic County. Changes were less pronounced in Cape May County where water levels were, on average, 1 to 3 feet (ft) lower than those during the previous study (2003), except near Rio Grande where a localized cone of depression had formed as a result of increased withdrawals. Large and widespread declines occurred in the Piney Point aquifer in Cumberland County where water levels in and around the city of Bridgeton had fallen in excess of 100 ft since 2003, and by 30 ft to more than 60 ft in surrounding areas. Groundwater levels in the Wenonah-Mount Laurel aquifer and Englishtown aquifer system continued to recover in east-central New Jersey; however, groundwater levels in the Wenonah-Mount Laurel aquifer throughout the southern part of the State continued to decline. In the Upper Potomac-Raritan-Magothy aquifer, groundwater levels were substantially lower than in 2003 in parts of northern Ocean County but were stable in the area adjacent to Raritan Bay (Critical Area 1), and water levels continued to recover in southern New Jersey. In the Middle Potomac-Raritan-Magothy aquifer, water levels rose near Raritan Bay in Middlesex County; however, modest declines were recorded in interior areas of Monmouth and Ocean Counties. Groundwater levels in both the Middle and Lower Potomac-Raritan-Magothy aquifers were stable or rising within the regional cone of depression in Critical Area 2; beyond the critical area in southern New Jersey, however, water levels were slightly lower than in 2003. Analyses of long-term water-level changes indicate that from 1978 to 2008 downward trends occurred at 20 wells (27 percent), upward trends at 27 wells (37 percent), and trends at 26 wells (36 percent) were insubstantial. Sustained, long-term declines were observed most often at wells within the Atlantic City 800-foot sand and at wells in the Piney Point aquifer in southern New Jersey, in which rates of decline were as great as 1.4 feet/year. Upward water-level trends were observed frequently at wells screened in the Englishtown aquifer system and the Wenonah-Mount Laurel aquifer in Critical Area 1 in east-central New Jersey, and in the Potomac-Raritan-Magothy aquifer system in parts of Critical Area 1 and throughout most of Critical Area 2 in southern New Jersey. Annual rates of upward change were as great as 3.9 and 5.6 ft/yr in the Englishtown aquifer system and Wenonah-Mount Laurel aquifer, respectively. Among the units of the Potomac-Raritan-Magothy aquifer system, annual rates of recovery were greatest in the Lower aquifer. From 1998 to 2008, downward water-level trends were observed at 22 wells (29 percent), upward trends were observed at 21 wells (27 percent), and insubstantial trends at 34 wells (44 percent). Downward trends were detected most often at wells open to the Piney Point aquifer and the Atlantic City 800-foot sand. Upward water-level trends were most frequent in wells open to the Englishtown aquifer system in Critical Area 1 and in wells within the Potomac-Raritan-Magothy aquifer system in southern New Jersey.

New Jersey↗
USGS2003

Flooding Associated with Typhoon Chata'an, July 5, 2002, Guam

Introduction On July 5, 2002, starting at about 8 a.m., the southern half of the eye of Typhoon Chata'an passed directly over the northern part of the island of Guam. Data collected on Guam indicate that the typhoon had sustained winds of 85 to 90 miles per hour (mi/hr) with gusts of up to 115 mi/hr (Charles Guard, National Weather Service, written commun., 2003). Storm rainfall totals exceeded 21 inches (in.) over the mountainous areas in south-central Guam. During the peak of the storm, rain fell at rates of up to 6.48 inches per hour (in/hr). Because of the damage caused by Typhoon Chata'an, the President signed a major disaster declaration on July 6, 2002. Damages associated with Typhoon Chata'an, while considered moderate relative to other storms that have affected Guam, amounted to several tens of millions of dollars. In excess of 1,000 single-family and multi-family homes were either extensively damaged or destroyed. Electrical power was out for several days over most of the island and no potable water was available through public distribution systems (Federal Emergency Management Agency, 2002). The extreme rainfall led to flooding in southern Guam and caused numerous landslides and severe erosion along water courses. The most significant evidence of these effects could be found in the Fena Valley Reservoir, where elevated sediment concentrations made the water unsuitable for use as a domestic water supply for several days. During normal operation, Fena Valley Reservoir supplies most of the drinking water for the military and some of the general public in southern Guam. All of the stream-gaging stations operated by the U.S. Geological Survey (USGS) on Guam were damaged to some extent during the flood and three of the stations were totally destroyed. Peak flows in many rivers in southern Guam reached record levels during Typhoon Chata'an. New record peak stages and/or flows of record occurred at 14 of 15 sites where the USGS has collected data. In some areas, the magnitude of flood peaks exceeded previous records significantly. Peak flows had recurrence intervals of 80 years or more at 9 of the 13 sites where sufficient data were available to make the computations. Four of the 9 sites had recurrence intervals that were determined to be greater than 100 years. In this fact sheet, storm rainfall totals and maximum rainfall totals for durations of 1-, 3-, 6-, and 12-hours are summarized for 12 rain gages on Guam. Peak stages and/or flows were computed at 15 USGS streamflow-gaging stations and recurrence intervals for the peaks determined. Rainfall and streamflow-gaging stations operated by the USGS on Guam are supported by funding provided by numerous agencies including the U.S. Navy, the U.S. Army Corps of Engineers (USACE), and the University of Guam through the Water and Environmental Research Institute (WERI). The USGS Office of Surface Water, as part of a national program to document the effects of extreme floods in the United States, provided funding to support the preparation of this fact sheet.

Fact Sheet↗
USGS2021

Effectiveness of rapid 'ōhi'a death management strategies at a focal disease outbreak on Hawai'i Island

The ongoing spread of rapid ‘ōhi‘a death (ROD) in the Hawaiian Islands threatens the long-term sustainability of ‘ōhi‘a lehua (Metrosideros polymorpha) forests throughout the state. First identified in the Puna district of Hawai‘i Island in 2014, the disease caused by the novel fungi Ceratocystis lukuohia and Ceratocystis huliohia has now spread island-wide and was recently detected on Kaua‘i, O‘ahu, and Maui. The leading hypothesis for the spread of ROD is through airborne ambrosia beetle frass particles that contain viable Ceratocystis propagules, thus management efforts focus on containing this frass. At the time of this study (2017–2018), the Waipunalei site was the northernmost outbreak of ROD on Hawai‘i Island. The focal nature of the outbreak and accessibility of the location provided the opportunity to monitor the effectiveness of two types of proposed management methods to reduce the airborne spread of potentially infective ambrosia beetle frass: tree felling and insecticide treatments. We placed 23 passive environmental samplers (PES), which monitored for airborne frass and wood particles containing C. lukuohia and C. huliohia in a grid that spanned the outbreak area over 22 weeks. Cross-vane panel traps with 1:1 methanol:ethanol lures were attached to nine of the PES to document wood-boring ambrosia and cerambycid beetle populations during the latter three months of the study. Monitoring with PES began three weeks before management and continued for one month after the last infected trees were felled. Glass microscope slides from the 23 PES were examined for airborne ambrosia beetle frass and wood particles by microscopy. DNA was extracted from the slides and tested by qPCR (quantitative polymerase chain reaction) for C. lukuohia and C. huliohia. We also investigated the correlation of beetle gallery counts with tree height and tested the efficacy of Bifen I/T insecticide (active ingredient: bifenthrin 7.9%) for preventing beetle attacks on the cut surface of ‘ōhi‘a bolts (tree stem sections). Beetle trapping data revealed that the area supports a diverse community of wood-boring beetles, some of which likely attack ‘ōhi‘a and may facilitate the spread of ROD. The number of beetle galleries on felled ‘ōhi‘a trees decreased linearly as tree height increased. We also observed significantly fewer beetle attacks on Bifen I/T treated ‘ōhi‘a bolts than non-treated bolts, but gallery formation nearly ceased in both treated and control bolts by week three. Ceratocystis lukuohia DNA was detected twenty-six times and C. huliohia was detected five times in the PES throughout this study. DNA detections were correlated to frass and wood counts, and the number of felled trees were correlated to wood particle counts but not frass counts. Both the timing and distribution of detections across the sampling grid indicate that tree felling may have reduced airborne detections of Ceratocystis DNA soon after tree felling was completed. A subsequent increase in detections after tree felling ceased may indicate that incomplete removal of infected trees and the appearance of new infections in previously asymptomatic trees could have allowed airborne detections of potentially infectious fungal propagules to once again increase.

Hawaii↗
USGS2018

Respiratory hazard assessment of combined exposure to complete gasoline exhaust and respirable volcanic ash in a multicellular human lung model at the air-liquid interface

Communities resident in urban areas located near active volcanoes can experience volcanic ash exposures during, and following, an eruption, in addition to sustained exposures to high concentrations of anthropogenic air pollutants ( e.g., vehicle exhaust emissions). Inhalation of anthropogenic pollution is known to cause the onset of, or exacerbate, respiratory and cardiovascular diseases. It is further postulated similar exposure to volcanic ash can also affect such disease states. Understanding of the impact of combined exposure of volcanic ash and anthropogenic pollution to human health, however, remains limited. The aim of this study was to assess the biological impact of combined exposure to respirable volcanic ash (from Soufrière Hills volcano (SHV), Montserrat and Chaitén volcano (ChV), Chile; representing different magmatic compositions and eruption styles) and freshly-generated complete exhaust from a gasoline vehicle. A multicellular human lung model (an epithelial cell-layer composed of A549 alveolar type II-like cells complemented with human blood monocyte-derived macrophages and dendritic cells cultured at the air-liquid interface) was exposed to diluted exhaust (1:10) continuously for 6 h, followed by immediate exposure to the ash as a dry powder (0.54 ± 0.19 μg/cm 2 and 0.39 ± 0.09 μg/cm 2 for SHV and ChV ash, respectively). After an 18 h incubation, cells were exposed again for 6 h to diluted exhaust, and a final 18 h incubation (at 37 °C and 5% CO 2 ). Cell cultures were then assessed for cytotoxic, oxidative stress and (pro-)inflammatory responses. Results indicate that, at all tested (sub-lethal) concentrations, co-exposures with both ash samples induced no significant expression of genes associated with oxidative stress ( HMOX1, NQO1 ) or production of (pro-)inflammatory markers (IL-1β, IL-8, TNF-α) at the gene and protein levels. In summary, considering the employed experimental conditions, combined exposure of volcanic ash and gasoline vehicle exhaust has a limited short-term biological impact to an advanced lung cell in vitro model.

Environmental Pollution↗
USGS2017

Optimal hydrograph separation using a recursive digital filter constrained by chemical mass balance, with application to selected Chesapeake Bay watersheds

Quantitative estimates of base flow are necessary to address questions concerning the vulnerability and response of the Nation’s water supply to natural and human-induced change in environmental conditions. An objective of the U.S. Geological Survey National Water-Quality Assessment Project is to determine how hydrologic systems are affected by watershed characteristics, including land use, land cover, water use, climate, and natural characteristics (geology, soil type, and topography). An important component of any hydrologic system is base flow, generally described as the part of streamflow that is sustained between precipitation events, fed to stream channels by delayed (usually subsurface) pathways, and more specifically as the volumetric discharge of water, estimated at a measurement site or gage at the watershed scale, which represents groundwater that discharges directly or indirectly to stream reaches and is then routed to the measurement point. Hydrograph separation using a recursive digital filter was applied to 225 sites in the Chesapeake Bay watershed. The recursive digital filter was chosen for the following reasons: it is based in part on the assumption that groundwater acts as a linear reservoir, and so has a physical basis; it has only two adjustable parameters (alpha, obtained directly from recession analysis, and beta, the maximum value of the base-flow index that can be modeled by the filter), which can be determined objectively and with the same physical basis of groundwater reservoir linearity, or that can be optimized by applying a chemical-mass-balance constraint. Base-flow estimates from the recursive digital filter were compared with those from five other hydrograph-separation methods with respect to two metrics: the long-term average fraction of streamflow that is base flow, or base-flow index, and the fraction of days where streamflow is entirely base flow. There was generally good correlation between the methods, with some biased slightly high and some biased slightly low compared to the recursive digital filter. There were notable differences between the days at base flow estimated by the different methods, with the recursive digital filter having a smaller range of values. This was attributed to how the different methods determine cessation of quickflow (the part of streamflow which is not base flow). For 109 Chesapeake Bay watershed sites with available specific conductance data, the parameters of the filter were optimized using a chemical-mass-balance constraint and two different models for the time-dependence of base-flow specific conductance. Sixty-seven models were deemed acceptable and the results compared well with non-optimized results. There are a number of limitations to the optimal hydrograph-separation approach resulting from the assumptions implicit in the conceptual model, the mathematical model, and the approach taken to impose chemical mass balance (including tracer choice). These limitations may be evidenced by poor model results; conversely, poor model fit may provide an indication that two-component separation does not adequately describe the hydrologic system’s runoff response. The results of this study may be used to address a number of questions regarding the role of groundwater in understanding past changes in stream-water quality and forecasting possible future changes, such as the timing and magnitude of land-use and management practice effects on stream and groundwater quality. Ongoing and future modeling efforts may benefit from the estimates of base flow as calibration targets or as a means to filter chemical data to model base-flow loads and trends. Ultimately, base-flow estimation might provide the basis for future work aimed at improving the ability to quantify groundwater discharge, not only at the scale of a gaged watershed, but at the scale of individual reaches as well.

Scientific Investigations Report↗
USGS2022

A biological condition gradient for coral reefs in the US Caribbean Territories: Part I. Coral narrative rules

As coral reef condition and sustainability continue to decline worldwide, losses of critical habitat and their ecosystem services have generated an urgency to understand and communicate reef response to management actions, environmental contamination, and natural disasters. Increasingly, coral reef protection and restoration programs emphasize the need for robust assessment tools for protecting high-quality waters and establishing conservation goals. Of equal importance is the need to communicate assessment results to stakeholders, beneficiaries, and the public so that environmental consequences of decisions are understood. The Biological Condition (BCG) model provides a structure to evaluate the condition of a coral reef in increments of change along a gradient of human disturbance. Communication of incremental change, regardless of direction, is important for decision makers and the public to better understand what is gained or lost depending on what actions are taken. We developed a narrative (qualitative) Biological Condition Gradient (BCG) from the consensus of a diverse expert panel to provide a framework for coral reefs in US Caribbean Territories. The model uses narrative descriptions of biological attributes for benthic organisms to evaluate reefs relative to undisturbed or minimally disturbed conditions. Using expert elicitation, narrative decision rules were proposed and deliberated to discriminate among six levels of change along a gradient of increasing anthropogenic stress. Narrative rules for each of the BCG levels are presented to facilitate the evaluation of benthic communities in coral reefs and provide specific narrative features to detect changes in coral reef condition and biological integrity. The BCG model can be used in the absence of numeric, or quantitative metrics, to evaluate actions that may encroach on coral reef ecosystems, manage endangered species habitat, and develop and implement management plans for marine protected areas, watersheds, and coastal zones. The narrative BCG model is a defensible model and communication tool that translates scientific results so the nontechnical person can understand and support both regulatory and non-regulatory water quality and natural resource programs.

Puerto Rico, U.S. Virgin Islands↗
USGS2010

Quantity and sources of base flow in the San Pedro River near Tombstone, Arizona

Base flow in the upper San Pedro River at the gaging station (USGS station 09471550) near Tombstone, Arizona, is an important factor in the long-term sustainability of the river's riparian ecosystem. Most base flow occurs during the non-summer months (typically, from November to May), because evapotranspiration (ET) is greater than groundwater discharge to the riparian zone during the growing season and typically causes periods of zero flow in the spring and fall. Streamflow during the summer months occurs only as a result of rainfall and runoff. Using a hydrograph separation technique that partitions streamflow into stormflow and base flow, based on the change in runoff from the previous day, median base flow at the Tombstone gage from 1968 to 2009 (1987 to 1996 data absent) is 4,890 acre-ft/yr. Median base flow for the earlier period of record, 1968 to 1986, is 5,830 acre-ft/yr and for the later period, 1997 to 2009, is 2,880 acre-ft/yr. Base flow in the upper San Pedro River is derived from groundwater discharge to the river from the regional and alluvial aquifer. The regional aquifer is defined as having recharge zones away from the river, primarily at mountain fronts and along ephemeral channels. The alluvial aquifer is recharged mainly from stormflow. Based on environmental isotope data, the composition of base flow in the upper San Pedro River at the gaging station near Tombstone is 74 +/- 10 percent regional groundwater and 26 +/- 10 percent summer storm runoff stored as alluvial groundwater for the 2000 to 2009 period. The volume of base flow in a given year is well explained, using multiple regression, by mean daily flow during the previous October and by rainfall during the months of December and January (R2 = 0.9). This does not suggest that streamflow is composed only of these two sources; rather, these two sources control the degree of saturation of the near-stream alluvial aquifer and, therefore, the amount of winter base-flow infiltration that is possible upstream of the Tombstone gaging station. Because of losing conditions upstream of the Tombstone gage, there is no minimum amount of base flow that would be expected in any given year. The regression equation was used to adjust the measured base flow to account for year-to-year variation in precipitation. Adjusted base flows decreased, independent of climate, from the early period of record to the late period of record. In addition to total base flow, other metrics were considered, including the start and end dates of base flow, the number of days of base flow, the 25th percentile mean daily flow, and the number of days of zero flow. Each of these showed a decline in base flow between the early period of record and the late period. The available evidence to evaluate this decrease - hydraulic gradients in the alluvial and regional aquifers and a 10-yr record of streamflow environmental isotope samples - indicates that no reduction in groundwater discharge has occurred over this period of record. Continued regional groundwater pumping will, however, eventually lead to a decline in the contribution of regional groundwater to base flow.

Scientific Investigations Report↗
USGS2009

Estimated Loads of Suspended Sediment and Selected Trace Elements Transported through the Milltown Reservoir Project Area Before and After the Breaching of Milltown Dam in the Upper Clark Fork Basin, Montana, Water Year 2008

This report presents estimated daily and cumulative loads of suspended sediment and selected trace elements transported during water year 2008 at three streamflow-gaging stations that bracket the Milltown Reservoir project area in the upper Clark Fork basin of western Montana. Milltown Reservoir is a National Priorities List Superfund site where sediments enriched in trace elements from historical mining and ore processing have been deposited since the construction of Milltown Dam in 1907. Milltown Dam was breached on March 28, 2008, as part of Superfund remedial activities to remove the dam and contaminated sediment that had accumulated in Milltown Reservoir. The estimated loads transported through the project area during the periods before and after the breaching of Milltown Dam, and for the entire water year 2008, were used to quantify the net gain or loss (mass balance) of suspended sediment and trace elements within the project area during the transition from a reservoir environment to a free-flowing river. This study was done in cooperation with the U.S. Environmental Protection Agency. Streamflow during water year 2008 compared to long-term streamflow, as represented by the record for Clark Fork above Missoula (water years 1930-2008), generally was below normal (long-term median) from about October 2007 through April 2008. Sustained runoff started in mid-April, which increased flows to near normal by mid-May. After mid-May, flows sharply increased to above normal, reaching a maximum daily mean streamflow of 16,800 cubic feet per second (ft3/s) on May 21, which essentially equaled the long-term 10th-exceedance percentile for that date. Flows substantially above normal were sustained through June, then decreased through the summer and reached near-normal by August. Annual mean streamflow during water year 2008 (3,040 ft3/s) was 105 percent of the long-term mean annual streamflow (2,900 ft3/s). The annual peak flow (17,500 ft3/s) occurred on May 21 and was 112 percent of the long-term mean annual peak flow (15,600 ft3/s). About 81 percent of the annual flow volume was discharged during the post-breach period. Daily loads of suspended sediment were estimated directly by using high-frequency sampling of the daily sediment monitoring. Daily loads of unfiltered-recoverable arsenic, cadmium, copper, iron, lead, manganese, and zinc were estimated by using regression equations relating trace-element discharge to either streamflow or suspended-sediment discharge. Regression equations for estimating trace-element discharge in water year 2008 were developed from instantaneous streamflow and concentration data for periodic water-quality samples collected during all or part of water years 2004-08. The equations were applied to records of daily mean streamflow or daily suspended-sediment loads to produce estimated daily trace-element loads. Variations in daily suspended-sediment and trace-element loads generally coincided with variations in streamflow. Relatively small to moderately large daily net losses from the project area were common during the pre-breach period when low-flow conditions were prevalent. Outflow loads from the project area sharply increased immediately after the breaching of Milltown Dam and during the rising limb and peak flow of the annual hydrograph. Net losses of suspended sediment and trace elements from the project area decreased as streamflow decreased during the summer, eventually becoming small or reaching an approximate net balance between inflow and outflow. Estimated daily loads of suspended sediment and trace elements for all three stations were summed to determine cumulative inflow and outflow loads for the pre-breach and post-breach periods, as well as for the entire water year 2008. Overall, the mass balance between the combined inflow loads from two upstream source areas (upper Clark Fork and Blackfoot River basins) and the outflow loads at Clark Fork above Missoula indicates net losses

Scientific Investigations Report↗
USGS2025

Tapwater exposures, residential risk, and mitigation in a PFAS-impacted-groundwater community

Tapwater (TW) safety and sustainability are priorities in the United States. Per/polyfluoroalkyl substance(s) (PFAS) contamination is a growing public-health concern due to prolific use, widespread TW exposures, and mounting human-health concerns. Historically-rural, actively-urbanizing communities that rely on surficial-aquifer private wells incur elevated risks of unrecognized TW exposures, including PFAS, due to limited private-well monitoring and contaminant-source proliferation in urbanizing landscapes. Here, a broad-analytical-scope TW-assessment was conducted in a hydrologically-vulnerable, Mississippi River alluvial-island community, where PFAS contamination of the shallow-alluvial drinking-water aquifer has been documented, but more comprehensive contaminant characterization to inform decision-making is currently lacking. In 2021, we analyzed 510 organics, 34 inorganics, and 3 microbial groups in 11 residential and community locations to assess (1) TW risks beyond recognized PFAS issues, (2) day-to-day and year-to-year risk variability, and (3) suitability of the underlying sandstone aquifer as an alternative source to mitigate TW-PFAS exposures. Seventy-six organics and 25 inorganics were detected. Potential human-health risks of detected TW exposures were explored based on cumulative benchmark-based toxicity quotients ( ∑ TQ ). Elevated risks ( ∑ TQ ≥ 1) from organic and inorganic contaminants were observed in all alluvial-aquifer-sourced synoptic samples but not in sandstone-aquifer-sourced samples. Repeated sampling at 3 sites over 52–55 h indicated limited variability in risk over the short-term. Comparable PFAS-specific ∑ TQ for spatial-synoptic, short-term (3 days) temporal, and long-term (3 years quarterly) temporal samples indicated that synoptic results provided useful insight into the risks of TW-PFAS exposures at French Island over the long-term. No PFAS detections in sandstone-aquifer-sourced samples over a 3 year period indicated no PFAS-associated risk and supported the sandstone aquifer as an alternative drinking-water source to mitigate community TW-PFAS exposures. This study illustrated the importance of expanded contaminant monitoring of private-well TW, beyond known concerns (in this case, PFAS), to reduce the risks of a range of unrecognized contaminant exposures.

Wisconsin↗
USGS2000

Environmental Setting and Effects on Water Quality in the Great and Little Miami River Basins, Ohio and Indiana

The Great and Little Miami River Basins drain approximately 7,354 square miles in southwestern Ohio and southeastern Indiana and are included in the more than 50 major river basins and aquifer systems selected for water-quality assessment as part of the U.S. Geological Survey's National Water-Quality Assessment Program. Principal streams include the Great and Little Miami Rivers in Ohio and the Whitewater River in Indiana. The Great and Little Miami River Basins are almost entirely within the Till Plains section of the Central Lowland physiographic province and have a humid continental climate, characterized by well-defined summer and winter seasons. With the exception of a few areas near the Ohio River, Pleistocene glacial deposits, which are predominantly till, overlie lower Paleozoic limestone, dolomite, and shale bedrock. The principal aquifer is a complex buried-valley system of sand and gravel aquifers capable of supporting sustained well yields exceeding 1,000 gallons per minute. Designated by the U.S. Environmental Protection Agency as a sole-source aquifer, the Buried-Valley Aquifer System is the principal source of drinking water for 1.6 million people in the basins and is the dominant source of water for southwestern Ohio. Water use in the Great and Little Miami River Basins averaged 745 million gallons per day in 1995. Of this amount, 48 percent was supplied by surface water (including the Ohio River) and 52 percent was supplied by ground water. Land-use and waste-management practices influence the quality of water found in streams and aquifers in the Great and Little Miami River Basins. Land use is approximately 79 percent agriculture, 13 percent urban (residential, industrial, and commercial), and 7 percent forest. An estimated 2.8 million people live in the Great and Little Miami River Basins; major urban areas include Cincinnati and Dayton, Ohio. Fertilizers and pesticides associated with agricultural activity, discharges from municipal and industrial wastewater-treatment and thermoelectric plants, urban runoff, and disposal of solid and hazardous wastes contribute contaminants to surface water and ground water throughout the study area. Surface water and ground water in the Great and Little Miami River Basins are classified as very hard, calcium-magnesiumbicarbonate waters. The major-ion composition and hardness of surface water and ground water reflect extensive contact with the carbonate-rich soils, glacial sediments, and limestone or dolomite bedrock. Dieldrin, endrin, endosulfan II, and lindane are the most commonly reported organochlorine pesticides in streams draining the Great and Little Miami River Basins. Peak concentrations of the herbicides atrazine and metolachlor in streams commonly are associated with post-application runoff events. Nitrate concentrations in surface water average 3 to 4 mg/L (milligrams per liter) in the larger streams and also show strong seasonal variations related to application periods and runoff events. Ambient iron concentrations in ground water pumped from aquifers in the Great and Little Miami River Basins often exceed the U.S. Environmental Protection Agency Secondary Maximum Contaminant Level (300 micrograms per liter). Chloride concentrations are below aesthetic drinking-water guidelines (250 mg/L), except in ground water pumped from low-yielding Ordovician shale; chloride concentrations in sodium-chloriderich ground water pumped from the shale bedrock can exceed 1,000 mg/L. Some of the highest average nitrate concentrations in ground water in Ohio and Indiana are found in wells completed in the buried-valley aquifer; these concentrations typically are found in those parts of the sand and gravel aquifer that are not overlain by clay-rich till. Atrazine was the most commonly detected herbicide in private wells. Concentrations of volatile organic compounds in ground water generally were below Federal drinking-water standards, except near areas of known or suspected contamination. Evaluation of fish and macroinvertebrate community performance in streams and rivers draining the Great and Little Miami River Basins indicates that most streams meet basic aquatic-life-use criteria set by the Ohio Environmental Protection Agency for warmwater habitat. Stream reaches whose biological community performance meet aquatic-lifeuse criteria defined for exceptional warmwater habitat are found in Twin Creek, the Upper Great Miami River, the Little Miami River, and the Whitewater River Basins. Other streams have exhibited significant improvements in biological community performance (and water quality)'that are attributed primarily to reduced pollutant loadings from wastewater-treatment plants upgraded since 1972. Four hydrogeomorphic regions were delineated in the Great and Little Miami River Basins based on distinct and relatively homogeneous natural characteristics. Primary features used to delineate the hydrogeomorphic regions include bedrock geology, surficial geology, physiography, hydrology, soil types, and vegetation. These four regions Till Plains, Drift Plains/Unglaciated, Interlobate, and Fluvial are used in the Great and Little Miami River Basins study to assess the influence of natural features of the environmental setting on surface- and ground-water quality.

Indiana, Ohio↗
USGS2020

Water-quality trends for selected sites and constituents in the international Red River of the North Basin, Minnesota and North Dakota, United States, and Manitoba, Canada, 1970–2017

A comprehensive study to evaluate water-quality trends, while considering natural hydroclimatic variability, in the Red River of the North Basin and assess water-quality conditions for the Red River of the North crossing the international boundary near Emerson, Manitoba, Canada (the binational site), was completed by the U.S. Geological Survey in cooperation with the International Joint Commission, North Dakota Department of Environmental Quality, and Minnesota Pollution Control Agency and in collaboration with Manitoba Sustainable Development and Environment and Climate Change Canada. The international Red River of the North Basin encompasses 3 U.S. States (South Dakota, North Dakota, and Minnesota) and 1 Canadian Province (Manitoba). Water quality in the Red River of the North Basin is of concern for both Federal governments and State and Provincial governments. Water-quality objectives have been previously established for selected dissolved ions and recently (2019) proposed for selected nutrients for the binational site. In the current (2020) study, water-quality data from State, Provincial, and Federal agencies in the United States and Canada for sites in the Red River of the North Basin from 1970 to 2017 were compiled and used for trend analysis. Trend analysis using a water-quality dataset from multiple agencies that collect water-quality data for various objectives presented multiple challenges. The trend-analysis approach was able to accommodate differences in water-quality data caused by field-collection and laboratory-analytical method differences, disparities in sampling frequencies, and spatial and temporal gaps in data. Most of these challenges were overcome by the statistical tool, R–QWTREND, which identifies trends in concentration unrelated to variability in streamflow. The integrated basin approach used in the current study, combined with comparing current data trends with historical trends, provided valuable insights into understanding how water quality is changing spatially (34 sites analyzed for a recent period, 2000–15) and temporally (5 sites analyzed for a 45-year historical period, 1970–2015) within the Red River of the North Basin. One of the most consistent spatial and temporal changes observed in the current study was increasing concentrations of sulfate among tributary and main-stem sites since 2000. For some sites, increases were detected starting as early as 1985. Total dissolved solids and chloride concentrations had spatial and temporal patterns like sulfate. Although R–QWTREND removes the variability in constituent concentration caused by natural streamflow variability, all variability in sulfate caused by hydroclimatic variability may not be captured because of changes in hydrologic pathways and changes in the contributions of sulfate from various natural sources. Nutrient concentrations demonstrated less consistent spatial and temporal changes than sulfate, and changes in nutrient concentrations were assumed to be more closely tied to human-induced rather than natural changes. Nitrate-plus-nitrite concentrations were mostly increasing in the upper Red River of the North subbasin, and for nitrate plus nitrite and total nitrogen, the Sheyenne River subbasin had consistent decreasing concentrations. Since 2000, total phosphorus has decreased in the upper Red River of the North subbasin, but total phosphorus concentration has increased for sites in the lower Red River of the North subbasin, and for some main-stem sites, concentrations have been increasing since 1985. Unlike sulfate, the pattern in historical trends for total phosphorus for the main-stem sites differed from tributary sites, indicating that human-induced changes affected tributaries and main-stem sites differently. The more detailed evaluation of flow-averaged water-quality conditions for the binational site provided an understanding of how loads have changed over time and what proportion of the year and season concentrations are expected to exceed water-quality objectives. In a basin with highly variable streamflow like the Red River of the North, the trend in flow-averaged load (assuming streamflow conditions are the same year after year) provided a robust measure of change over time. Increasing concentrations of sulfate, chloride, total dissolved solids, and total phosphorus since 1985 for the binational site resulted in longer periods of exceedance of water-quality objectives per year occurring over time. For total nitrogen, decreasing concentrations resulted in shorter periods of exceedance per year during 1980 to 2015, but concentrations were still expected to exceed the water-quality objective about half the year. Periods of when exceedances were likely to occur during the year were affected by the source and transport mechanisms of the constituent. Trend results from this effort identified how water quality has changed across the basin, and further investigation would help to identify causes for the trends observed here. Information from the current study provides a basis for future trend attribution studies, evaluation of water-quality objectives, and development of comprehensive strategies for reducing nutrients to desired targets and establishes a baseline for tracking future progress in the Red River of the North Basin.

Minnesota, North Dakota, South Dakota, Manitoba↗
USGS2012

Lateral and vertical channel movement and potential for bed-material movement on the Madison River downstream from Earthquake Lake, Montana

The 1959 Hebgen Lake earthquake caused a massive landslide (Madison Slide) that dammed the Madison River and formed Earthquake Lake. The U.S. Army Corps of Engineers excavated a spillway through the Madison Slide to permit outflow from Earthquake Lake. In June 1970, high streamflows on the Madison River severely eroded the spillway channel and damaged the roadway embankment along U.S. Highway 287 downstream from the Madison Slide. Investigations undertaken following the 1970 flood events concluded that substantial erosion through and downstream from the spillway could be expected for streamflows greater than 3,500 cubic feet per second (ft 3 /s). Accordingly, the owners of Hebgen Dam, upstream from Earthquake Lake, have tried to manage releases from Hebgen Lake to prevent streamflows from exceeding 3,500 ft 3 /s measured at the U.S. Geological Survey (USGS) gaging station 0638800 Madison River at Kirby Ranch, near Cameron, Montana. Management of flow releases from Hebgen Lake to avoid exceeding the threshold streamflow at USGS gaging station 06038800 is difficult, and has been questioned for two reasons. First, no road damage was reported downstream from the Earthquake Lake outlet in 1993, 1996, and 1997 when streamflows exceeded the 3,500-ft 3 /s threshold. Second, the 3,500-ft 3 /s threshold generally precludes releases of higher flows that could be beneficial to the blue-ribbon trout fishery downstream in the Madison River. In response to concerns about minimizing streamflow downstream from Earthquake Lake and the possible armoring of the spillway, the USGS, in cooperation with the Madison River Fisheries Technical Advisory Committee (MADTAC; Bureau of Land Management; Montana Department of Environmental Quality; Montana Fish, Wildlife and Parks; PPL-Montana; U.S. Department of Agriculture Forest Service - Gallatin National Forest; and U.S. Fish and Wildlife Service), conducted a study to determine movement of the Madison River channel downstream from Earthquake Lake and to investigate the potential for bed material movement along the same reach. The purpose of this report is to present information about the lateral and vertical movement of the Madison River from 1970 to 2006 for a 1-mile reach downstream from Earthquake Lake and for Raynolds Pass Bridge, and to provide an analysis of the potential for bed-material movement so that MADTAC can evaluate the applicability of the previously determined threshold streamflow for initiation of damaging erosion. As part of this study channel cross sections originally surveyed by the USGS in 1971 were resurveyed in 2006. Incremental channel-movement distances were determined by comparing the stream centerlines from 14 aerial photographs taken between 1970 and 2006. Depths of channel incision and aggregation were determined by comparing the 2006 and 1971 cross-section and water-surface data. Particle sizes of bed and bank materials were measured in 2006 and 2008 using the pebble-count method and sieve analyses. A one-dimensional hydraulic-flow model (HEC-RAS) was used to calculate mean boundary-shear stresses for various streamflows; these calculated boundary-shear stresses were compared to calculated critical-shear stresses for the bed materials to determine the potential for bed-material movement. A comparison of lateral channel movement distances with annual peak streamflows shows that streamflows higher than the 3,500-ft 3 /s threshold were followed by lateral channel movement except from 1991 to 1992 and possibly from 1996 to 1997. However, it was not possible to discern whether the channel moved gradually or suddenly, or in response to one peak flow, to several peak flows, or to sustained flows. The channel moved between 2002 and 2005 even when streamflows were less than the threshold streamflow of 3,500 ft 3 /s. Comparisons of cross sections and aerial photographs show that the channel has moved laterally and incised and aggraded to varying degrees. The channel has developed meander bends and has incised as much as 5–12 feet (ft) through the upstream part of the Madison Slide (cross sections 1400–800). Near cross section 800, the stream has eroded into the steep right bank between the stream and the road where fill was mechanically placed after 1970. Channel movement also was noted downstream from the Madison Slide. Near Raynolds Pass Bridge, about 3 miles (mi) downstream from Earthquake Lake, elevations across the channel have changed by -1.4 ft to +1.9 ft, but these changes were local in nature and could represent a few rocks or depressions in the bed. Overall, it does not appear that the materials eroded from the Madison Slide are causing aggradation in the subreach near the Raynolds Pass Bridge. Comparisons of critical shear stresses to mean boundary-shear stresses indicate that the D50 particle sizes (median size) along the right side of the bed between cross sections 400 and 500 and along the right side of the bed between cross sections 1300 and 1400 could move at the threshold streamflow. In contrast, most of the D84 particle sizes at those two locations probably will not move at the threshold streamflow. This lack of movement for the larger particles at the threshold streamflow could lead to further armoring of the bed as the D50 and smaller-sized particles are removed from the bed and transported downstream. The Shields parameter values from 0.04 to 0.08 that were used to calculate critical shear stresses could be conservative for a high-gradient stream such as the Madison. A higher, less conservative, Shields parameter would result in higher critical shear stresses, meaning that higher streamflows would be required to move material than those reported herein. In addition, because materials in the channel thalweg are exposed to higher boundary-shear stresses than the materials along the sides of the channel, larger, more erosion-resistant materials likely exist in the deeper parts of the channel where high-flow depths and velocities prevented sediment sampling. Movement of these materials might require higher critical shear stresses than estimated in this report. Characterization of sediment sizes in the center of the stream and observation of bed-material movement for a range of streamflows could provide information to help refine the Shields parameter and critical-shear stress estimates for bed materials in the Madison River downstream from Earthquake Lake. Furthermore, resurveying cross sections and water-surface elevations more frequently (either annually or after high streamflows) could better define the relation between streamflow and lateral and vertical channel movement.

Montana↗
USGS2016

Hydropower assessment of Bolivia—A multisource satellite data and hydrologic modeling approach

This study produced a geospatial database for use in a decision support system by the Bolivian authorities to investigate further development and investment potentials in sustainable hydropower in Bolivia. The study assessed theoretical hydropower of all 1-kilometer (km) stream segments in the country using multisource satellite data and a hydrologic modeling approach. With the assessment covering the 2 million square kilometer (km 2 ) region influencing Bolivia’s drainage network, the potential hydropower figures are based on theoretical yield assuming that the systems generating the power are 100 percent efficient. There are several factors to consider when determining the real-world or technical power potential of a hydropower system, and these factors can vary depending on local conditions. Since this assessment covers a large area, it was necessary to reduce these variables to the two that can be modeled consistently throughout the region, streamflow or discharge, and elevation drop or head. First, the Shuttle Radar Topography Mission high-resolution 30-meter (m) digital elevation model was used to identify stream segments with greater than 10 km 2 of upstream drainage. We applied several preconditioning processes to the 30-m digital elevation model to reduce errors and improve the accuracy of stream delineation and head height estimation. A total of 316,500 1-km stream segments were identified and used in this study to assess the total theoretical hydropower potential of Bolivia. Precipitation observations from a total of 463 stations obtained from the Bolivian Servicio Nacional de Meteorología e Hidrología (Bolivian National Meteorology and Hydrology Service) and the Brazilian Agência Nacional de Águas (Brazilian National Water Agency) were used to validate six different gridded precipitation estimates for Bolivia obtained from various sources. Validation results indicated that gridded precipitation estimates from the Tropical Rainfall Measuring Mission (TRMM) reanalysis product (3B43) had the highest accuracies. The coarse-resolution (25-km) TRMM data were disaggregated to 5-km pixels using climatology information obtained from the Climate Hazards Group Infrared Precipitation with Stations dataset. About a 17-percent bias was observed in the disaggregated TRMM estimates, which was corrected using the station observations. The bias-corrected, disaggregated TRMM precipitation estimate was used to compute stream discharge using a regionalization approach. In regionalization approach, required homogeneous regions for Bolivia were derived from precipitation patterns and topographic characteristics using a k -means clustering approach. Using the discharge and head height estimates for each 1-km stream segment, we computed hydropower potential for 316,490 stream segments within Bolivia and that share borders with Bolivia. The total theoretical hydropower potential (TTHP) of these stream segments was found to be 212 gigawatts (GW). Out of this total, 77.4 GW was within protected areas where hydropower projects cannot be developed; hence, the remaining total theoretical hydropower in Bolivia (outside the protected areas) was estimated as 135 GW. Nearly 1,000 1-km stream segments, however, were within the boundaries of existing hydropower projects. The TTHP of these stream segments was nearly 1.4 GW, so the residual TTHP of the streams in Bolivia was estimated as 133 GW. Care should be exercised to understand and interpret the TTHP identified in this study because all the stream segments identified and assessed in this study cannot be harnessed to their full capacity; furthermore, factors such as required environmental flows, efficiency, economics, and feasibility need to be considered to better identify a more real-world hydropower potential. If environmental flow requirements of 20–40 percent are considered, the total theoretical power available reduces by 60–80 percent. In addition, a 0.72 efficiency factor further reduces the estimation by another 28 percent. This study provides the base theoretical hydropower potential for Bolivia, the next step is to identify optimal hydropower plant locations and factor in the principles to appraise a real-world power potential in Bolivia.

Open-File Report↗
USGS2004

Hydrologic, soil, and vegetation gradients in remnant and constructed riparian wetlands in west-central Missouri, 2001-04

A study was conducted by the U.S. Geological Survey in cooperation with the Missouri Department of Conservation at the Four Rivers Conservation Area (west-central Missouri), between January 2001 and March 2004, to examine the relations between environmental factors (hydrology, soils, elevation, and landform type) and the spatial distribution of vegetation in remnant and constructed riparian wetlands. Vegetation characterization included species composition of ground, understory, and overstory layers in selected landforms of a remnant bottomland hardwood ecosystem, monitoring survival and growth of reforestation plots in leveed and partially leveed constructed wetlands, and determining gradients in colonization of herbaceous vegetation in a constructed wetland. Similar environmental factors accounted for variation in the distribution of ground, understory, and overstory vegetation in the remnant bottomland forest plots. The primary measured determining factors in the distribution of vegetation in the ground layer were elevation, soil texture (clay and silt content), flooding inundation duration, and ponding duration, while the distribution of vegetation in the understory layer was described by elevation, soil texture (clay, silt, and sand content), total flooding and ponding inundation duration, and distance from the Marmaton or Little Osage River. The primary measured determining factors in the distribution of overstory vegetation in Unit 1 were elevation, soil texture (clay, silt, and sand content), total flooding and ponding inundation duration, ponding duration, and to some extent, flooding inundation duration. Overall, the composition and structure of the remnant bottomland forest is indicative of a healthy, relatively undisturbed flood plain forest. Dominant species have a distribution of individuals that shows regeneration of these species with significant recruitment in the smaller size classes. The bottomland forest is an area whose overall hydrology has not been significantly altered; however, portions of the area have suffered from hydrologic alteration by a drainage ditch that is resulting in the displacement of swamp and marsh species by colonizing shrub and tree species. This area likely will continue to develop into an immature flood plain forest under the current (2004) hydrologic regime. Reforestation plots in constructed wetlands consisted of sampling survival and growth of multiple tree species (Quercus palustris, pin oak; Carya illinoiensis, pecan) established under several production methods and planted at multiple elevations. Comparison of survival between tree species and production types showed no significant differences for all comparisons. Survival was high for both species and all production types, with the highest mortality seen in the mounded root production method (RPM®) Quercus palustris (pin oak, 6.9 percent), while direct seeded Quercus palustris at middle elevation and bare root Quercus palustris seedlings at the low elevation plots had 100 percent survival. Measures of growth (diameter and height) were assessed among species, production types, and elevation by analyzing relative growth. The greatest rate of tree diameter (72.3 percent) and height (65.3 percent) growth was observed for direct seeded Quercus palustris trees planted at a middle elevation site. Natural colonized vegetation data were collected at multiple elevations within an abandoned cropland area of a constructed wetland. The primary measured determining factors in the distribution of herbaceous vegetation in this area were elevation, ponding duration, and soil texture. Richness, evenness, and diversity were all significantly greater in the highest elevation plots as a result of more recent disturbance in this area. While flood frequency and duration define the delivery mechanism for inundation on the flood plain, it is the duration of ponding and amount of “topographic capture” of these floodwaters in fluvial landforms that largely determines the survivability and distribution of tree species in both remnant and constructed wetlands. Ponding, flooding, ground-water levels, and precipitation all accounted for saturated conditions in the upper soil profiles in the Four Rivers Conservation Area monitoring sites. Of these processes, ponding and flooding were the primary factors accounting for soil saturation conditions. The identification of landform features in undisturbed settings, therefore, can be an important aide in predicting the sustainable spatial distribution of various plant species in riparian revegetation projects.

Missouri↗
USGS2018

Groundwater contributions to excessive algal growth in the East Fork Carson River, Carson Valley, west-central Nevada, 2010 and 2012

Excessive algal growth and low dissolved oxygen concentrations were observed during low streamflow conditions during summer months along a 5,800-foot reach of the East Fork Carson River in Carson Valley, west-central Nevada. Algal growth from nutrient enrichment of a stream reduces aquatic diversity, threatens fish ecology and stream health, and can be a recreational nuisance. In response to concerns that groundwater discharging to the 5,800-foot reach of the East Fork Carson River may be a source of nutrients to the stream, the U.S. Geological Survey, in cooperation with the Carson Water Subconservancy District and the Nevada Division of Environmental Protection, conducted studies during the summers of 2010 and 2012 to gain an improved understanding of the contributions of nutrients to the stream from groundwater, characterize algal conditions and algal effects on water quality, assess potential sources of nitrate in groundwater discharging to the stream, and evaluate nitrate reduction in groundwater from denitrification. A reconnaissance study in the summer of 2010 along the 5,800-foot study reach located a subreach with clear evidence of nutrient-rich groundwater discharging to the stream. At the subreach, nitrate plus nitrite (referred to hereafter as nitrate) concentrations in groundwater discharging to the stream were high (average 2.75 milligrams per liter as nitrogen) along the right bank. The stream at this location had the highest stream nitrate concentrations (average 0.056 milligrams per liter as nitrogen) compared to other locations upstream and downstream of the subreach. As a result, the 2012 study focused on a 405-foot subreach of the East Fork Carson River centered where results from the 2010 study found the highest stream and groundwater concentrations of nitrate, as well as the greatest observed contributions of groundwater discharge to the stream. Groundwater nutrient concentrations were much higher than stream nutrient concentrations during the summer of 2012 during low streamflow conditions at the 405-foot subreach of the East Fork Carson River. Average groundwater nitrate and orthophosphate concentrations along the right bank of the 405‑foot subreach were 9 and 12 times higher, respectively, than in the stream at this subreach. Groundwater discharge rates to the study reach based on different methods varied from 0.09 to 1.2 cubic feet per second per mile. Estimated groundwater discharge rates to the right bank of the study subreach were used to calculate groundwater nutrient load estimates to the subreach right bank, which were found to be low when compared to stream nutrient loads. Elevated algal biomass levels above nuisance thresholds were observed during the summers of 2010 and 2012. The study reach was characterized as mesotrophic-eutrophic during the 2010 study and eutrophic during the 2012 study. The presence of algae caused daily dissolved oxygen and pH fluctuations in the stream, resulting in exceedances of the State of Nevada water-quality standards owing to low dissolved oxygen concentrations and high pH concentrations, although the standards might not have been applicable during 2012 because of extremely low streamflow. The addition of nutrients to the stream from the constant supply in groundwater discharge sustains the growth of algae during low streamflow conditions. In the summer when streamflow is low or very low, nutrient-rich groundwater discharge enters the stream through the sediment-water interface at the streambed. Because the attached algae is thick and stream velocity is low, the nutrient-rich water pools at the sediment-water interface. Higher nutrient concentrations at the streambed create a favorable microenvironment for algae attached to the substrate to consume available nutrients from the groundwater before the groundwater mixes with overlying stream water. The source of nitrate in groundwater in this subreach is anthropogenic because nitrate concentrations are greater than background groundwater nitrate concentrations in Douglas County, high groundwater nitrate concentrations are only found at the right bank of the stream near a housing development, and organic wastewater compounds indicative of human-derived sources were also detected in groundwater wells on the right bank of the stream. Nitrogen and oxygen isotope concentrations of nitrate in shallow groundwater were used to determine the specific source of the nitrate, but the isotopic values indicated denitrification was occurring. Further investigation is needed to determine the specific anthropogenic source of the nitrate in the groundwater because the denitrification present in all samples obscures the original source of nitrogen.

Nevada↗