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USGS1979

Monthly and annual water budgets of Lake Wingra, Madison, Wisconsin, 1972-77

This report presents estimated annual and monthly water budgets for Lake Wingra and the adjacent wetland area for January 1972 through September 1972. Annually, inputs from precipitation, surface runoff, and groundwater inflow are approximately equal (31, 34, and 35 percent, respectively). Outputs include outflow from the lake into Murphy Creek (70 percent), evapotranspiration from the lake and wetland (26 percent), and ground-water outflow (4 percent). The inputs and outputs vary seasonally. In months when snowmelt occurs, surface runoff is a major input (56 percent in March; 46 percent in April). In fall and winter ground-water inflow is a major input (57 percent in November). Precipitation comprises 41 percent of the input in August but only 18 percent in January. Lake outflow is the major output except from July through September. Combined evaporation and evapotranspiration is a major output in summer (45 to 58 percent) but minor in winter (less than 13 percent). Ground-water outflow is a small part of the budget each month, ranging from 2 percent in March and April to a maximum of 7 percent in September. The water budget is based on field data collected from January 1972 through June 1973, and on fragmentary data and estimates for July 1973 through September 1977. The budget terms differ from those published by Oakes, Hendrickson, and Zuehls (1975, table 10) because springflow has been included in total ground-water inflow and estimated on a monthly basis in this report. Previously only annual estimates were provided.

Wisconsin↗

USGS1980

Data-base system for northern Midwest regional aquifer-system analysis

The U.S. Geological Survey is conducting a study of the Cambrian and Ordovician aquifer system of the northern Midwest as part of a national series of Regional Aquifer-Systems Analysis (RASA). An integral part of this study will be a simulation of the ground-water flow regime using the Geological Survey's three-dimensional finite-difference model. The first step in the modeling effort is the design and development of a systematic set of processes to facilitate the collection, evaluation, manipulation, and use of large quantities of information. A computerized data-base system to accomplish these goals has been completed for the northern Midwest RASA. The input to the data-base system consists of either point values or contour maps of the hydrogeologic data required by the model. Digital samples of contoured surfaces are obtained by machine digitization. Uniformly spaced model-node values are then computed from the discrete data by two-dimensional interpolation. The interpolator uses the regional (long wavelength) characteristics of the data to compute a surface with minimum total curvature. Local (short wavelength) data are merged with the regional surface to produce the model-node values at the desired spacing. Nonuniformly spaced nodal values may be obtained by fitting two-dimensional polynomials (bicubic splines) to surfaces formed by uniformly spaced points and solving for the surface values at the node locations. The uniformly or nonuniformly spaced node values constitute the output of the data-base system and in turn are the input arrays of data values for the ground-water flow model. Management of the data base is facilitated by forming a data file for each model input parameter and for other hydrogeologic data used in the study. The data files are subdivided into elements consisting of individual model-layer arrays. In this form the data base can be readily accessed and edited. In addition to the interpolation programs, software components of the system include programs: (1) to transform geographic coordinates on a Lambert conformal conic projection to cartesian coordinates and vice versa, (2) to machine contour gridded data, (3) to expedite manipulation and editing of data, and (4) to perform various interarray computations. The data-base system has the following attributes: (1) manual handling of data is minimized and machine handling of data is maximized, (2) given unequally spaced point data over the extent of a study area, model input arrays for any reasonable uniform node spacing can be rapidly computed, (3) accuracy of computed node values are generally compatible with accuracy and spatial distribution of point data, (4) a relatively large class of nonuniformly spaced node configurations can be computed, (5) data within data-base files can be easily accessed and readily edited, and (6) the occurrence of data processing errors at various stages of data-base generation is monitored by machine contouring the computed grids. Functioning of the data-base system is illustrated by the sequence of steps required to produce a model-input array of transmissivity, given raw geologic and hydraulic conductivity data.

Water-Resources Investigations Report↗

USGS1996

Hydrology and water quality of Lauderdale Lakes, Walworth County, Wisconsin, 1993-94

Water and phosphorus budgets were determined for the Lauderdale Lakes (the interconnected Green, Middle, and Mill Lakes) in Walworth County, southeastern Wisconsin to provide background information for a wastewater management plan to limit the input of phosphorus to the lakes. The most significant components of the water and phosphorus budgets were determined independently by intensive data collection from November 1993 through October 1994. In addition to development of the water and phosphorus budgets, in-lake water quality, and trophic state of the lakes were evaluated. The lakes (treated as one lake with three basins) have a total surface area of 807 acres. The lakes have a surface-water outlet, but have no major surface inlets. Lake level is controlled by a dam and weir at the outlet. Maximum depths of Green, Middle, and Mill Lakes are about 60, 50, and 50 feet, respectively. The total drainage area of the lakes measured from the outlet is 16.1 square miles; only about 2.5 square miles, however, contribute surface runoff directly to the lake. About 70 percent of the 14.7-mile shoreline length is developed. Shoreline development includes 1,010 houses, of which about 30 percent are used year-round. Ground water and precipitation are the primary water-budget inflow components, and during the study period represented 72 and 24 percent of the total annual inflow, respectively. Surface-water inflow from the small nearshore contributing drainage area accounted for only 4 percent of the inflow budget. Total annual phosphorus input to the lakes was 846 pounds. Although surface water accounted for only 4 percent of the water budget, it represented 51 percent of the total annual phosphorus input. Phosphorus input from septic systems was the second largest source, with a probable annual input of 210 pounds, accounting for 25 percent of the total. Positive ground-water gradients to the lake and phosphorus concentrations in ground water were verified by data from nearshore observation wells. Phosphorus concentrations in ground water exceeded background concentrations of 0.008 milligrams per liter in three out of six observation wells in the inflow area of the lakes. Overall, the phosphorus loading to the lakes is small and lake-water quality is good. The trophic state indices calculated for the lakes ranged from oligotrophic to mesotrophic but were in the mesotrophic class for most of the year. An equation to predict phosphorus concentration at spring turnover from loading estimates was fairly accurate in predicting the measured phosphorus concentration for Lauderdale Lakes.

Wisconsin↗

USGS1999

Sources and chronology of nitrate contamination in spring waters, Suwannee River basin, Florida

A multi-tracer approach, which consisted of analyzing water samples for n aturally occurring chemical and isotopic indicators, was used to better understand sources and chronology of nitrate contamination in spring wate rs discharging to the Suwannee and Santa Fe Rivers in northern Florida. Dur ing 1997 and 1998, as part of a cooperative study between the Suwannee River Water Management District and the U.S. Geological Survey, water samples were collected and analyzed from 24 springs and two wells for major ions, nutrients, dissolved organic carbon, and selected environmental isotopes [18O/16O, D/H, 13C/12C, 15N/14N]. To better understand when nitrate entered the ground-water system, water samples were analyzed for chlorofluorocarbons (CFCs; CCl3F, CCl2F2, and C2Cl3F3) and tritium (3H); in this way, the apparent ages and residence times of spring waters and water from shallow zones in the Upper Floridan aquifer were determined. In addition to information obtained from the use of isotopic and other chemical tracers, information on changes in land-use activities in the basin during 1954-97 were used to estimate nitrogen inputs from nonpoint sources for five counties in the basin. Changes in nitrate concentrations in spring waters with time were compared with estimated nitrogen inputs for Lafayette and Suwannee Counties. Agricultural activities [cropland farming, animal farming operations (beef and dairy cows, poultry, and swine)] along with atmospheric deposition have contributed large quantities of nitrogen to ground water in the Suwannee River Basin in northern Florida. Changes in agricultural land use during the past 40 years in Alachua, Columbia, Gilchrist, Lafayette, and Suwannee Counties have contributed variable amounts of nitrogen to the ground-water system. During 1955-97, total estimated nitrogen from all nonpoint sources (fertilizers, animal wastes, atmospheric deposition, and septic tanks) increased continuously in Gilchrist and Lafayette Counties. In Suwannee, Alachua, and Columbia Counties, estimated nitrogen inputs from all nonpoint sources peaked in the late 1970's corresponding to the peak use in fertilizer during this time. Fertilizer use in Columbia, Gilchrist, Lafayette, and Suwannee Counties increased substantially during 1993-97. The heavy use of fertilizers in the basin is corroborated by nitrogen isotope data. Values of d15N of nitrate (d15N-NO3) in spring waters range from 2.7 per mil (SUW718971) to 10.6 per mil (Poe Spring) with a median of 5.4 per mil. The range of values indicates that nitrate in the sampled spring waters most likely originates from a mixture of inorganic (fertilizers) and organic (animal wastes) sources; however, higher d15N values for Poe and Lafayette Blue Springs indicate that an organic source of nitrogen probably is contributing nitrate to these spring waters. Water samples from two wells sampled in Lafayette County have high d15N-NO3 values of 11.0 and 12.1 per mil, indicating the predominance of an organic source of nitrate. These two wells are located near dairy and poultry farms, where leachate from animal wastes may contribute nitrate to ground water. Dissolved-gas data (nitrogen, argon, and oxygen) indicate that denitrification has not removed large amounts of nitrate from the ground-water system. Thus, variations in d15N-NO3 values of spring waters can be attributed to variations in d15N-NO3 values of ground-water recharge, and can be used to obtain information about source(s) of nitrate. Extending the use of age-dating techniques (CFCs and 3H) to spring waters in complex karst systems required the use of several different approaches for estimating age and residence time of ground water discharging to springs. These approaches included the use of a simple reservoir model, a piston-flow model, an exponential model, and a binary-mixing model. When age data (CFC-11, CFC-113, and 3H) are combined for all springs, models that incorporate exponential mixtures seem to provide reliable estimates of average residence times of ground water discharging to springs. Whereas, data for some individual springs fit a binary-mixing model with more than 50 percent young water (recharged within the past 5 years), data from other individual springs fit a piston-flow model with a water age of about 25 years. The young ages of several spring waters (such as SUW718971, SUW725971, and Ginnie Spring) indicate the high vulnerability of the springs to contamination. For most springs, CFCs suggest that a large fraction of the water is more than 20 years old. Springs with lower flows tend to have young ages (shallow ground-water flow systems), whereas springs with higher flows tend to have older ages (deep ground-water flow systems). The chemical composition of spring waters can be used as a qualitative indicator of age and ground-water residence time. Nitrate-nitrogen concentrations and dissolved oxygen in spring waters are inversely related to the apparent ages of spring waters and ground-water residence time in the basin. Silica concentrations increase as the age of spring waters increase. Long-term trends in nitrate concentrations in selected spring waters were compared with estimated inputs of nitrogen from various sources in Suwannee and Lafayette Counties. In both counties, trends in nitrate concentrations in spring waters closely followed the estimated contribution of nitrogen from fertilizers. Decreasing nitrate concentrations in spring waters from Suwannee County followed the decrease in estimated fertilizer use from the mid-1970's to the early 1990's. Increasing nitrate concentrations in sprin g waters from Lafayette County followed the steady increase in fertilizer use from the early 1960's to the mid-1990's The relation between the concentration of nitrate in ground water and the amount of nitrogen that is added to a ground-water contributing area for a spring is controlled by complex interactions among hydrogeologic, land-use, and climatic factors, as well as several other land-management factors. Spring waters represent mixtures of converging flow paths that contain ground water with a range of ages. Even if nitrogen inputs were reduced substantially, it may take decades for nitrate concentrations in the ground-water system to return to near background levels.

Florida↗

USGS2013

Influence of multi-source and multi-temporal remotely sensed and ancillary data on the accuracy of random forest classification of wetlands in northern Minnesota

Wetland mapping at the landscape scale using remotely sensed data requires both affordable data and an efficient accurate classification method. Random forest classification offers several advantages over traditional land cover classification techniques, including a bootstrapping technique to generate robust estimations of outliers in the training data, as well as the capability of measuring classification confidence. Though the random forest classifier can generate complex decision trees with a multitude of input data and still not run a high risk of over fitting, there is a great need to reduce computational and operational costs by including only key input data sets without sacrificing a significant level of accuracy. Our main questions for this study site in Northern Minnesota were: (1) how does classification accuracy and confidence of mapping wetlands compare using different remote sensing platforms and sets of input data; (2) what are the key input variables for accurate differentiation of upland, water, and wetlands, including wetland type; and (3) which datasets and seasonal imagery yield the best accuracy for wetland classification. Our results show the key input variables include terrain (elevation and curvature) and soils descriptors (hydric), along with an assortment of remotely sensed data collected in the spring (satellite visible, near infrared, and thermal bands; satellite normalized vegetation index and Tasseled Cap greenness and wetness; and horizontal-horizontal (HH) and horizontal-vertical (HV) polarization using L-band satellite radar). We undertook this exploratory analysis to inform decisions by natural resource managers charged with monitoring wetland ecosystems and to aid in designing a system for consistent operational mapping of wetlands across landscapes similar to those found in Northern Minnesota.

Minnesota↗

USGS2009

Benthic biogeochemical cycling, nutrient stoichiometry, and carbon and nitrogen mass balances in a eutrophic freshwater bay

Green Bay, while representing only ~7% of the surface area and ~1.4% of the volume of Lake Michigan, contains one‐third of the watershed of the lake, and receives approximately one‐third of the total nutrient loading to the Lake Michigan basin, largely from the Fox River at the southern end of the bay. With a history of eutrophic conditions dating back nearly a century, the southern portion of the bay behaves as an efficient nutrient and sediment trap, sequestering much of the annual carbon and nitrogen input within sediments accumulating at up to 1 cm per year. Depositional fluxes of organic matter varied from ~0.1 mol C m22 yr21 to >10 mol C m −2 yr −1 and were both fairly uniform in stoichiometric composition and relatively labile. Estimates of benthic recycling derived from pore‐water concentration gradients, whole‐sediment incubation experiments, and deposition‐burial models of early diagenesis yielded an estimated 40% of the carbon and 50% of the nitrogen recycled back into the overlying water. Remineralization was relatively rapid with ~50% of the carbon remineralized within ~15 yr of deposition, and a mean residence time for metabolizable carbon and nitrogen in the sediments of 20 yr. On average, organic carbon regeneration occurred as 75% CO 2 , 15% CH 4 , and 10% dissolved organic carbon (DOC). Carbon and nitrogen budgets for the southern bay were based upon direct measurements of inputs and burial and upon estimates of export and production derived stoichiometrically from a coupled phosphorus budget. Loadings of organic carbon from rivers were ~3.7 mol m −2 yr −1 , 80% in the form of DOC and 20% as particulate organic carbon. These inputs were lost through export to northern Green Bay and Lake Michigan (39%), through sediment burial (26%), and net CO 2 release to the atmosphere (35%). Total carbon input, including new production, was 4.54 mol m −2 yr −1 , equivalent to ~10% of the gross annual primary production. Nitrogen budget terms were less well quantified, with nitrogen export ~54% of total inputs and burial ~24%, leaving an unquantified residual loss term in the nitrogen budget of ~22%.

Green Bay↗

USGS1998

Oxygen and hydrogen isotope systematics of Lake Baikal, Siberia: Implications for paleoclimate studies

We interpret oxygen and hydrogen isotope data for water samples from Lake Baikal, Siberia, its tributaries and other local rivers, and local precipitation in terms of the known water budget for the modem lake in order to gain insight into past limnological and climatic processes that influenced the lake. Lake Baikal is remarkably uniform in its isotopic composition (??18O = -15.8 ?? 0.2???; ??D = -123 ?? 2???) and lies slightly to the right of the global meteoric water line, which suggests significant evaporation. Water is supplied to the lake by over 300 rivers and streams. The oxygen isotope values (??18O) of the rivers in the Baikal catchment range from -13.4 to -21.2???. The hydrogen isotope values (??D) for the same area range from -103 to -156???. Both these ranges generally conform to the global meteoric water line. The weighted average isotopic composition of input to the lake (rivers plus precipitation) is -15.2??? for ??18O and -116??? for ??D, values higher than those of the modem lake. Therefore, the isotopic composition of the modem lake cannot be related to the modem input through simple evaporation. Instead, modeling of the isotopic mass balance of the lake suggests that inputs (precipitation and influx from rivers) and outputs (evaporation and outflow) are not at a steady-state equilibrium under current climate conditions. We found previous input to the lake had lower ??18O and ??D values than modem input, which reflects cooler climates in the past compared with modern conditions. Under constant climate conditions, steady-state conditions are not expected to be reached by the lake for at least 700 yr because of its large size and the long residence time of water in the lake.

Limnology and Oceanography↗

USGS2021

Appendix E. Water quality and hydrology of Green Lake, Wisconsin, and the response in its near-surface water-quality and metalimnetic dissolved oxygen minima to changes in phosphorus loading

Green Lake is the deepest natural inland lake in Wisconsin, USA, with a maximum depth of about 72 meters (m). In the early 1900’s, the lake was believed to have very good water quality (low nutrient concentrations and good water clarity), with low dissolved oxygen (DO) concentrations only in the deepest part of the lake. Because of increased phosphorus (P) inputs from anthropogenic activities in its watershed, total phosphorus (TP) concentrations in the lake increased, which led to increased algal production and low DO concentrations not only occurring in its deepest areas but also in the middle of the water column (metalimnion). Routine monitoring of the lake and its tributaries has been conducted by the U.S. Geological Survey since 2004 and 1988, respectively. Results from this monitoring led to the Wisconsin Department of Natural Resources (WDNR) listing the lake as impaired because of low DO concentrations in the metalimnion, with elevated TP concentrations identified as the cause of impairment. As part of this study, comprehensive sampling of the lake and its tributaries was conducted in 2017–2018 to augment ongoing monitoring and further describe the low DO concentrations in the lake (especially in the metalimnion). Empirical and process-driven water quality models were then used to determine the causes of the low DO concentrations and the magnitude of P load reductions needed to improve the water quality of the lake to meet multiple water-quality goals, including the WDNR criteria for TP and DO. Data from previous studies showed that DO concentrations in the metalimnion decreased slightly as summer progressed in the early 1900’s, but since the late 1970s have typically dropped below 5 milligrams per liter (mg/L), which is the WDNR criterion for impairment. During 2014–2018 (baseline period for this study), the near-surface geometric-mean TP concentration during June–September in the east side of the lake was 0.020 mg/L and in the west side was 0.016 mg/L (both were below the 0.015 mg/L WDNR criterion for the lake), and the minimum metalimnetic DO concentrations measured in August ranged from 1.0 to 4.7 mg/L. It was believed that the degradation in water quality was caused by excessive P inputs to the lake; therefore, the total P inputs to the lake were estimated. The mean annual external P load during 2014–2018 was estimated to be 8,980 kilograms per year (kg/yr), of which monitored and unmonitored tributary inputs contributed 84 percent, atmospheric inputs contributed 8 percent, waterfowl contributed 7 percent, and septic systems contributed 1 percent. At fall turnover, internal sediment recycling contributed an additional 7,040 kg that increased TP concentrations in shallow areas of the lake by about 0.020 mg/L. The elevated TP concentrations then persisted until the following spring. On an annual basis, however, there is a net deposition of P to the bottom sediments. Empirical models were used to describe how the near-surface water quality of Green Lake would be expected to respond to changes in external P loading. Predictions from the models showed a relatively linear response between P loading and TP and chlorophyll-a (Chl-a) concentrations in the lake, with the changes in TP and Chl-a concentrations being less on a percentage basis (50–60 percent for TP and 30–70 percent for Chl-a) than the changes in P loading. Mean summer water clarity, indicated by Secchi disk depths, had a larger response to decreases in P loading than to increases in loading. Based on these relations, external P loading to the lake would need to be decreased from 8,980 kg/yr to about 5,460 kg/yr for the geometric mean June–September TP concentration on the east side of the lake, with higher TP concentrations than the west side, to reach the WDNR criterion of 0.015 mg/L. This reduction of 3,520 kg/yr equates to a 46-percent reduction in the potentially controllable external P sources (all external sources except precipitation, atmospheric deposition, and waterfowl) from that measured during water years (WYs) 2014–2018. The total external P loading would need to be decreased to 7,680 kg/yr (17-percent reduction in potentially controllable external P sources) for near-surface June–September TP concentrations in the west side of the lake to reach 0.015 mg/L. Total external P loading would need to be decreased to 3,870–5,320 kg/yr for the lake to be classified as oligotrophic, with a near-surface June-September TP concentration of 0.012 mg/L. Results from the hydrodynamic water-quality model GLM-AED (General Lake Model coupled to the Aquatic Ecodynamics modeling library) indicated that metalimnetic DO minima are driven by external P loading and internal sediment recycling that lead to high TP concentrations during spring and early summer, which in turn lead to high phytoplankton production, high metabolism and respiration, and ultimately DO consumption in the upper, warmer areas of the metalimnion. GLM-AED results indicated that settling of organic material during summer may be slowed by the colder, denser, and more viscous water in the metalimnion and increase DO consumption. Based on empirical evidence comparing minimum metalimnetic DO concentrations with various meteorological, hydrologic, water quality, and in-lake physical factors, lower metalimnetic DO concentrations occurred when there was warmer metalimnetic water temperatures, higher near-surface Chl-a and TP concentrations, and lower Secchi depths during summer. GLM-AED results indicated that the external P load would need to be reduced to about 4,010 kg/yr, a 57-percent reduction from that measured in 2014–2018, to eliminate the occurrence of metalimnetic DO minima of less than 5 mg/L in over 75 percent of the years (the target provided by the WDNR). Large reductions in external P loading are expected to have an immediate effect on the near-surface TP concentrations and metalimnetic DO concentrations in Green Lake. However, it may take several years for the full effects of the external load reduction to be observed because internal sediment recycling is an important source of P for the following spring.

Wisconsin↗

USGS2015

Net ecosystem production and organic carbon balance of U.S. East Coast estuaries: A synthesis approach

Net ecosystem production (NEP) and the overall organic carbon budget for the estuaries along the East Coast of the United States are estimated. We focus on the open estuarine waters, excluding the fringing wetlands. We developed empirical models relating NEP to loading ratios of dissolved inorganic nitrogen to total organic carbon, and carbon burial in the sediment to estuarine water residence time and total nitrogen input across the landward boundary. Output from a data-constrained water quality model was used to estimate inputs of total nitrogen and organic carbon to the estuaries across the landward boundary, including fluvial and tidal-wetland sources. Organic carbon export from the estuaries to the continental shelf was computed by difference, assuming steady state. Uncertainties in the budget were estimated by allowing uncertainties in the supporting model relations. Collectively, U.S. East Coast estuaries are net heterotrophic, with the area-integrated NEP of −1.5 (−2.8, −1.0) Tg C yr −1 (best estimate and 95% confidence interval) and area-normalized NEP of −3.2 (−6.1, −2.3) mol C m −2 yr −1 . East Coast estuaries serve as a source of organic carbon to the shelf, exporting 3.4 (2.0, 4.3) Tg C yr −1 or 7.6 (4.4, 9.5) mol C m −2 yr −1 . Organic carbon inputs from fluvial and tidal-wetland sources for the region are estimated at 5.4 (4.6, 6.5) Tg C yr −1 or 12 (10, 14) mol C m −2 yr −1 and carbon burial in the open estuarine waters at 0.50 (0.33, 0.78) Tg C yr −1 or 1.1 (0.73, 1.7) mol C m −2 yr −1 . Our results highlight the importance of estuarine systems in the overall coastal budget of organic carbon, suggesting that in the aggregate, U.S. East Coast estuaries assimilate (via respiration and burial) ~40% of organic carbon inputs from fluvial and tidal-wetland sources and allow ~60% to be exported to the shelf.

Global Biogeochemical Cycles↗

USGS2003

Determination of antibiotic residues in manure, soil, and surface waters

In the last years more and more often detections of antimicrobially active compounds (“antibiotics”) in surface waters have been reported. As a possible input pathway in most cases municipal sewage has been discussed. But as an input from the realm of agriculture is conceivable as well, in this study it should be investigated if an input can occur via the pathway application of liquid manure on fields with the subsequent mechanisms surface run‐off/interflow, leaching, and drift. For this purpose a series of surface waters, soils, and liquid manures from North Rhine‐Westphalia (Northwestern Germany) were sampled and analyzed for up to 29 compounds by HPLC‐MS/MS. In each of the surface waters antibiotics could be detected. The highest concentrations were found in samples from spring (300 ng/L of erythromycin). Some of the substances detected (e.g., tylosin), as well as characteristics in the landscape suggest an input from agriculture in some particular cases. In the investigation of different liquid manure samples by a fast immunoassay method sulfadimidine could be detected in the range of 1…2 mg/kg. Soil that had been fertilized with this liquid manure showed a content of sulfadimidine extractable by accelerated solvent extraction (ASE) of 15 μg/kg dry weight even 7 months after the application. This indicates the high stability of some antibiotics in manure and soil.

Acta Hydrochimica et Hydrobiologica↗

USGS2015

Evaluation of habitat suitability index models by global sensitivity and uncertainty analyses: a case study for submerged aquatic vegetation

Habitat suitability index (HSI) models are commonly used to predict habitat quality and species distributions and are used to develop biological surveys, assess reserve and management priorities, and anticipate possible change under different management or climate change scenarios. Important management decisions may be based on model results, often without a clear understanding of the level of uncertainty associated with model outputs. We present an integrated methodology to assess the propagation of uncertainty from both inputs and structure of the HSI models on model outputs (uncertainty analysis: UA) and relative importance of uncertain model inputs and their interactions on the model output uncertainty (global sensitivity analysis: GSA). We illustrate the GSA/UA framework using simulated hydrology input data from a hydrodynamic model representing sea level changes and HSI models for two species of submerged aquatic vegetation (SAV) in southwest Everglades National Park: Vallisneria americana (tape grass) and Halodule wrightii (shoal grass). We found considerable spatial variation in uncertainty for both species, but distributions of HSI scores still allowed discrimination of sites with good versus poor conditions. Ranking of input parameter sensitivities also varied spatially for both species, with high habitat quality sites showing higher sensitivity to different parameters than low-quality sites. HSI models may be especially useful when species distribution data are unavailable, providing means of exploiting widely available environmental datasets to model past, current, and future habitat conditions. The GSA/UA approach provides a general method for better understanding HSI model dynamics, the spatial and temporal variation in uncertainties, and the parameters that contribute most to model uncertainty. Including an uncertainty and sensitivity analysis in modeling efforts as part of the decision-making framework will result in better-informed, more robust decisions.

Florida↗

USGS2022

Increased mercury and reduced insect diversity in linked stream-riparian food webs downstream of a historical mercury mine

Historical mining left a legacy of abandoned mines and waste rock in remote headwaters of major river systems in the western United States. Understanding the influence of these legacy mines on culturally and ecological important downstream ecosystems is not always straight-forward because of elevated natural levels of mineralization in mining-impacted watersheds. To test the ecological effects of historic mining in the headwaters of the upper Salmon River watershed (USA), we measured multiple community and chemical endpoints in downstream linked aquatic-terrestrial food webs. Mining inputs impacted downstream food webs through increased mercury accumulation and decreased insect biodiversity. Total mercury (THg) in seston, aquatic insect larvae, adult aquatic insects, riparian spiders, and fish at sites up to 7.6 km downstream of mining was in much higher concentrations (1.3 to 11.3-fold) and isotopically distinct compared with sites immediately upstream of mining inputs. Methylmercury (MeHg) concentrations in bull trout and riparian spiders were sufficiently high (732 – 918 and 347 – 1,140 ng MeHg g -1 dw) to affect humans, birds, and piscivorous fish. Furthermore, the alpha-diversity of benthic insects was locally depressed by 12-20% within 4.3 to 5.7 km downstream of from the mine. However, because total insect biomass was not affected by mine inputs, the mass of mercury in benthic insects at a site (i.e., ng Hg m -2 ) was extremely elevated downstream (10 – 1,778-fold) compared with directly upstream of mining inputs. Downstream adult aquatic insect-mediated fluxes of total mercury were also high (~16 ng THg m -2 d -1 ). Abandoned mines can have ecologically important effects on downstream communities, including reduced biodiversity and increased mercury flux to higher order consumers, including fish, birds, and humans.

Idaho↗

USGS2003

Characterization of lake water and ground water movement in the littoral zone of Williams Lake, a closed-basin lake in North central Minnesota

Williams Lake, Minnesota is a closed‐basin lake that is a flow‐through system with respect to ground water. Ground‐water input represents half of the annual water input and most of the chemical input to the lake. Chemical budgets indicate that the lake is a sink for calcium, yet surficial sediments contain little calcium carbonate. Sediment pore‐water samplers (peepers) were used to characterize solute fluxes at the lake‐water–ground‐water interface in the littoral zone and resolve the apparent disparity between the chemical budget and sediment data. Pore‐water depth profiles of the stable isotopes δ 18 O and δ 2 H were non‐linear where ground water seeped into the lake, with a sharp transition from lake‐water values to ground‐water values in the top 10 cm of sediment. These data indicate that advective inflow to the lake is the primary mechanism for solute flux from ground water. Linear interstitial velocities determined from δ 2 H profiles (316 to 528 cm/yr) were consistent with velocities determined independently from water budget data and sediment porosity (366 cm/yr). Stable isotope profiles were generally linear where water flowed out of the lake into ground water. However, calcium profiles were not linear in the same area and varied in response to input of calcium carbonate from the littoral zone and subsequent dissolution. The comparison of pore‐water calcium profiles to pore‐water stable isotope profiles indicate calcium is not conservative. Based on the previous understanding that 40–50 % of the calcium in Williams Lake is retained, the pore‐water profiles indicate aquatic plants in the littoral zone are recycling the retained portion of calcium. The difference between the pore‐water depth profiles of calcium and δ 18 O and δ 2 H demonstrate the importance of using stable isotopes to evaluate flow direction and source through the lake‐water–ground‐water interface and evaluate mechanisms controlling the chemical balance of lakes.

Minnesota↗

USGS2004

Tritium hydrology of the Mississippi River basin

In the early 1960s, the US Geological Survey began routinely analysing river water samples for tritium concentrations at locations within the Mississippi River basin. The sites included the main stem of the Mississippi River (at Luling Ferry, Louisiana), and three of its major tributaries, the Ohio River (at Markland Dam, Kentucky), the upper Missouri River (at Nebraska City, Nebraska) and the Arkansas River (near Van Buren, Arkansas). The measurements cover the period during the peak of the bomb-produced tritium transient when tritium concentrations in precipitation rose above natural levels by two to three orders of magnitude. Using measurements of tritium concentrations in precipitation, a tritium input function was established for the river basins above the Ohio River, Missouri River and Arkansas River sampling locations. Owing to the extent of the basin above the Luling Ferry site, no input function was developed for that location. The input functions for the Ohio and Missouri Rivers were then used in a two-component mixing model to estimate residence times of water within these two basins. (The Arkansas River was not modelled because of extremely large yearly variations in flow during the peak of the tritium transient.) The two components used were: (i) recent precipitation (prompt outflow) and (ii) waters derived from the long-term groundwater reservoir of the basin. The tritium concentration of the second component is a function of the atmospheric input and the residence times of the groundwaters within the basin. Using yearly time periods, the parameters of the model were varied until a best fit was obtained between modelled and measured tritium data. The results from the model indicate that about 40% of the flow in the Ohio River was from prompt outflow, as compared with 10% for the Missouri River. Mean residence times of 10 years were calculated for the groundwater component of the Ohio River versus 4 years for the Missouri River. The mass flux of tritium through the Mississippi Basin and its tributaries was calculated during the years that tritium measurements were made. The cumulative fluxes, calculated in grams of 3II were: (i) 160 g for the Ohio (1961-1986), (ii) 98 g for the upper Missouri (1963-1997), (iii) 30 g for the Arkansas (1961-1997) and (iv) 780 g for the Mississippi (1961-1997). Published in 2004 by John Wiley and Sons, Ltd.

Mississippi River basin↗

USGS2026

Effect of land-use change and climate on coral calcification and geochemistry: A 253-year time series from west Maui

Land-use change and climate variability both regulate land-based inputs of sediment and nutrient delivery to coral reefs, yet few records in Hawaii can identify when these land-based inputs began or how they have evolved through time. We present a 253-year (1760–2013) coral core record from Olowalu reef, Maui, spanning pre-colonial settlement through the rise and decline of sugarcane agriculture, water diversion, and modern coastal development. Trace element ratios (e.g., Ba/Ca, Y/Ca, P/Ca, Fe/Ca, Sr/Ca) and coral growth parameters document how watershed disturbance and climate variability have influenced reef conditions. Coral trace element records exhibit coherent variability at annual to decadal timescales consistent with El Niño–Southern Oscillation and Pacific Decadal Oscillation frequencies, suggesting climatic control on runoff and groundwater delivery. Superimposed on this natural variability, Ba/Ca, P/Ca, and Fe/Ca increased by 17–55% from the eighteenth century to the late twentieth century, with the largest increase occurring during the mid-1900s and coinciding with the maximum extent of Maui sugarcane plantations. These shifts indicate prolonged increases in sediment and nutrient inputs to the reef. Coral calcification increased by ~30% prior to ~1970 but declined thereafter, coincident with the peak sugarcane production. The negative correlation between coral calcification rate and terrigenous proxies (e.g., Ba/Ca, Y/Ca, P/Ca, and Fe/Ca) suggests that episodic terrestrial inputs from sugarcane plantations depressed coral calcification. This record provides the first pre-colonial to modern baseline for ridge-to-reef connectivity in Maui and demonstrates that historical land-use change has left a persistent geochemical imprint on the downstream reef ecosystem.

Hawaii↗

USGS2009

A carbon, nitrogen, and sulfur elemental and isotopic study in dated sediment cores from the Louisiana Shelf

Three sediment cores were collected off the Mississippi River delta on the Louisiana Shelf at sites that are variably influenced by recurring, summer-time water-column hypoxia and fluvial loadings. The cores, with established chronology, were analyzed for their respective carbon, nitrogen, and sulfur elemental and isotopic composition to examine variable organic matter inputs, and to assess the sediment record for possible evidence of hypoxic events. Sediment from site MRJ03-3, which is located close to the Mississippi Canyon and generally not influenced by summer-time hypoxia, is typical of marine sediment in that it contains mostly marine algae and fine-grained material from the erosion of terrestrial C4 plants. Sediment from site MRJ03-2, located closer to the mouth of the Mississippi River and at the periphery of the hypoxic zone (annual recurrence of summer-time hypoxia >50%), is similar in composition to core MRJ03-3, but exhibits more isotopic and elemental variability down-core, suggesting that this site is more directly influenced by river discharge. Site MRJ03-5 is located in an area of recurring hypoxia (annual recurrence >75%), and is isotopically and elementally distinct from the other two cores. The carbon and nitrogen isotopic composition of this core prior to 1960 is similar to average particulate organic matter from the lower Mississippi River, and approaches the composition of C3 plants. This site likely receives a greater input of local terrestrial organic matter to the sediment. After 1960 and to the present, a gradual shift to higher values of δ 13 C and δ 15 N and lower C:N ratios suggests that algal input to these shelf sediments increased as a result of increased productivity and hypoxia. The values of C:S and δ 34 S reflect site-specific processes that may be influenced by the higher likelihood of recurring seasonal hypoxia. In particular, the temporal variations in the C:S and δ 34 S down-core are likely caused by changes in the rate of sulfate reduction, and hence the degree of hypoxia in the overlying water column. Based principally on the down-core C:N and C:S ratios and δ 13 C and δ 34 S profiles, sites MRJ03-3 and MRJ03-2 generally reflect more marine organic matter inputs, while site MRJ03-5 appears to be more influenced by terrestrial deposition.

Geo-Marine Letters↗

USGS2005

Microbial responses and nitrous oxide emissions during wetting and drying of organically and conventionally managed soil under tomatoes

The types and amounts of carbon (C) and nitrogen (N) inputs, as well as irrigation management are likely to influence gaseous emissions and microbial ecology of agricultural soil. Carbon dioxide (CO2) and nitrous oxide (N2O) efflux, with and without acetylene inhibition, inorganic N, and microbial biomass C were measured after irrigation or simulated rainfall in two agricultural fields under tomatoes (Lycopersicon esculentum). The two fields, located in the California Central Valley, had either a history of high organic matter (OM) inputs ("organic" management) or one of low OM and inorganic fertilizer inputs ("conventional" management). In microcosms, where short-term microbial responses to wetting and drying were studied, the highest CO2 efflux took place at about 60% water-filled pore space (WFPS). At this moisture level, phospholipid fatty acids (PLFA) indicative of microbial nutrient availability were elevated and a PLFA stress indicator was depressed, suggesting peak microbial activity. The highest N 2O efflux in the organically managed soil (0.94 mg N2O-N m-2 h-1) occurred after manure and legume cover crop incorporation, and in the conventionally managed soil (2.12 mg N2O-N m-2 h-1) after inorganic N fertilizer inputs. Elevated N2O emissions occurred at a WFPS >60% and lasted <2 days after wetting, probably because the top layer (0-150 mm) of this silt loam soil dried quickly. Therefore, in these cropping systems, irrigation management might control the duration of elevated N2O efflux, even when C and inorganic N availability are high, whereas inorganic N concentrations should be kept low during times when soil moisture cannot be controlled.

Biology and Fertility of Soils↗

USGS2000

Coastal erosion vs riverline sediment discharge in the Arctic shelfx seas

This article presents a comparison of sediment input by rivers and by coastal erosion into both the Laptev Sea and the Canadian Beaufort Sea (CBS). New data on coastal erosion in the Laptev Sea, which are based on field measurements and remote sensing information and existing data on coastal erosion in the CBS as well as riverine sediment discharge into both the Laptev Sea and the CBS are included. Strong regional differences in the percentages of coastal ero- sion and riverine sediment supply are observed. The CBS is dominated by the riverine sediment discharge (64.45x106 t a-1) mainly of the Mackenzie River. which is the largest single source of sediments in the Arctic. Riverine sediment discharge into the Laptev Sea amounts to 24.10x106 t a-1, more than 70% of which are related to the Lena River. In comparison with the CBS. the Laptev Sea coast on average delivers approximately twice as much sediment mass per kilometer, a result of higher erosion rates due to higher cliffs and seasonal ice melting. In the Laptev Sea sediment input by coastal erosion (58.4x106 t a-1) is therefore more important than in the CBS and the ratio between riverine and coastal sediment input amounts to 0.4. Coastal erosion supplying 5.6x106 t a-1 is less significant for the sediment budget of the CBS where riverine sediment discharge exceeds coastal sediment input by a factor of ca. 10.

International Journal of Earth Sciences↗