A5064787822- Soil and Water Nutrient Dynamics
- Hydrology and Watershed Management Studies
- Water Quality and Resources Studies
- Water Quality and Pollution Assessment
- Fish Ecology and Management Studies
- Groundwater and Isotope Geochemistry
- Marine and coastal ecosystems
- Wastewater Treatment and Nitrogen Removal
- Soil erosion and sediment transport
- Water Quality Monitoring Technologies
- Atmospheric and Environmental Gas Dynamics
- Geochemistry and Geologic Mapping
- Hydrological Forecasting Using AI
- Soil Geostatistics and Mapping
- Geological Studies and Exploration
- Water resources management and optimization
- Water Quality Monitoring and Analysis
- Urban Stormwater Management Solutions
- Coastal wetland ecosystem dynamics
- Regional Economic and Spatial Analysis
- Aquatic Ecosystems and Phytoplankton Dynamics
- Hydrocarbon exploration and reservoir analysis
- Hydrology and Drought Analysis
- Environmental Science and Water Management
- Water Systems and Optimization
United States Geological Survey
2009-2022
Clark Art Institute
2020
Mindanao State University – Iligan Institute of Technology
2019
Herzliya Medical Center
1998
657 Oslo
1998
National Cancer Institute
1990-1994
Arizona Department of Health Services
1984
Illinois Environmental Protection Agency
1984
Indiana Department of Natural Resources
1984
Illinois Department of Transportation
1984
Seasonal hypoxia in the northern Gulf of Mexico has been linked to increased nitrogen fluxes from Mississippi and Atchafalaya River Basins, though recent evidence shows that phosphorus also influences productivity Gulf. We developed a spatially explicit structurally detailed SPARROW water-quality model reveals important differences sources transport processes control (N) (P) delivery Our simulations indicate agricultural watersheds contribute more than 70% delivered N P. However, corn...
We describe a method for using spatially referenced regressions of contaminant transport on watershed attributes (SPARROW) in regional water‐quality assessment. The is designed to reduce the problems data interpretation caused by sparse sampling, network bias, and basin heterogeneity. regression equation relates measured rates streams descriptors pollution sources land‐surface stream‐channel characteristics. Regression models total phosphorus (TP) nitrogen (TN) are constructed region defined...
Knowledge of headwater influences on the water-quality and flow conditions downstream waters is essential to water-resource management at all governmental levels; this includes recent court decisions jurisdiction Federal Clean Water Act (CWA) over upland areas that contribute larger water bodies. We review current watershed research use a model investigate receiving waters. Our evaluations demonstrate intrinsic connections headwaters landscape processes through their influence supply,...
One result of increased scientific and public interest in water quality over the past few decades has been gradual accumulation reliable long‐term data records an examining these for trends. This paper summarizes examines some major issues choices involved detecting estimating magnitude temporal trends measures stream quality. The first issue is type trend hypothesis to examine: step versus monotonic trend. second relates general category statistical methods employ: parametric nonparametric....
Water-quality records from two nationwide sampling networks now permit nationally consistent analysis of long-term water-quality trends at more than 300 locations on major U.S. rivers. Observed in 24 measures water quality for the period 1974 to 1981 provide new insight into changes stream that occurred during a time both terrestrial and atmospheric influences surface waters. Particularly noteworthy are widespread decreases fecal bacteria lead concentrations increases nitrate, chloride,...
Abstract Carbon cycling in the coastal zone affects global carbon budgets and is critical for understanding urgent issues of hypoxia, acidification, tidal wetland loss. However, there are no regional spanning three main ecosystems waters: wetlands, estuaries, shelf waters. Here we construct such a budget eastern North America using historical data, empirical models, remote sensing algorithms, process‐based models. Considering net fluxes total at domain boundaries, 59 ± 12% (± 2 standard...
Determining natural background concentrations of nutrients in watersheds the developed world has been hampered by a lack pristine sampling sites covering range climatic conditions and basin sizes. Using data from 63 minimally impacted U.S. Geological Survey reference basins, we empirical models yield total nitrogen (TN) phosphorus (TP) small as functions annual runoff, size, atmospheric deposition rate, region-specific factors. We applied previously estimated in-stream loss rates to yields...
The importance of lotic systems as sinks for nitrogen inputs is well recognized. A fraction in streamflow removed to the atmosphere via denitrification with remainder exported loads. At watershed scale, there a keen interest understanding factors that control fate throughout stream channel network, particular attention processes deliver large loads sensitive coastal ecosystems. We use dynamic transport model assess biogeochemical (nitrate loadings, concentration, temperature) and...
We calibrated SPARROW (Spatially Referenced Regression on Watershed Attributes) surface water‐quality models using measurements of total nitrogen and phosphorus from 37 sites in the 13,900‐km 2 Waikato River Basin, largest watershed North Island New Zealand. This first application outside United States included watersheds representative a wide range natural cultural conditions water‐resources data that were well suited for calibrating validating models. applied spatially distributed model to...
For additional information, contact: National Water-Quality Assessment ProgramU.S. Geological Survey413 Center12201 Sunrise Valley DriveReston, Virginia 20192https://water.usgs.gov/nawqa/ SPARROW (SPAtially Referenced Regressions On Watershed attributes) is a watershed modeling technique for relating water-quality measurements made at network of monitoring stations to attributes the watersheds containing stations. The core model consists nonlinear regression equation describing...
Abstract Net ecosystem production (NEP) and the overall organic carbon budget for estuaries along East Coast of United States are estimated. We focus on open estuarine waters, excluding fringing wetlands. developed empirical models relating NEP to loading ratios dissolved inorganic nitrogen total carbon, burial in sediment water residence time input across landward boundary. Output from a data‐constrained quality model was used estimate inputs boundary, including fluvial tidal‐wetland...
We compared the results of 12 recently calibrated regional SPARROW (SPAtially Referenced Regressions On Watershed attributes) models covering most continental United States to evaluate consistency and differences in factors affecting stream nutrient loads. The - 6 for total nitrogen phosphorus all provide similar levels prediction accuracy, but those major river basins eastern half country were somewhat more accurate. simulate long-term mean annual loads as a function wide range known...
Abstract Downstream flow in rivers is repeatedly delayed by hydrologic exchange with off‐channel storage zones where biogeochemical processing occurs. We present a dimensionless metric that quantifies river connectivity as the balance between downstream and of water bed, banks, floodplains. The degree directly influences quality — too little limits amount exchanged leads to biogeochemically inactive storage, while much contact time sediments for reactions proceed. Using reaction significance...
Lakes, reservoirs, and other ponded waters are ubiquitous features of the aquatic landscape, yet their cumulative role in nitrogen removal large river basins is often unclear. Here we use predictive modeling, together with comprehensive water quality, land use, hydrography datasets, to examine explain influences more than 18,000 on through networks Northeastern United States. Thresholds pond density where become important regional identified shown vary according a waters' relative size,...
A nationally consistent and well‐documented collection of water quality quantity data compiled during the past 30 years for streams rivers in United States is now available on CD‐ROM accessible over World Wide Web. The include measurements from two U.S. Geological Survey (USGS) national networks 122 physical, chemical, biological properties collected at 680 monitoring stations 1962 to 1995, assurance information that describes sample agencies, laboratories, analytical methods, estimates...
Estimates of nitrogen and phosphorus fertilizer use were made for counties in the United States period 1945 to 1985. County estimates obtained through disaggregation state-level proportion amount state fertilized acreage reported exist counties. Numerical values by county are not presented text this report because size data file, but available machine-readable form upon request. Graphical summaries national, state, briefly describe spatial temporal variability that data.
Despite progress in the implementation of conservation practices, related improvements water quality have been challenging to measure larger river systems. In this paper we quantify these downstream effects by applying empirical U.S. Geological Survey water-quality model SPARROW investigate whether spatial differences intensity were statistically correlated with variations nutrient loads. contrast other forms data analysis, application controls for confounding factors such as hydrologic...
Abstract Small ponds—farm ponds, detention or impoundments below 0.01 km 2 —serve important human needs throughout most large river basins. Yet the role of small ponds in regional nutrient and sediment budgets is essentially unknown, currently making it impossible to evaluate their management potential achieve water quality objectives. Here we used new hydrography data sets found that depending on spatial position within both local catchments larger network, can dominate retention nitrogen,...