Richard Webb (Former Employee)
Science and Products
Filter Total Items: 37
Potential effects of runoff, fluvial sediment, and nutrient discharges on the coral reefs of Puerto Rico Potential effects of runoff, fluvial sediment, and nutrient discharges on the coral reefs of Puerto Rico
Coral reefs, the foundation and primary structure of many highly productive and diverse tropical marine ecosystems, have been degraded by human activity in much of the earth's tropical oceans. To contribute to improved understanding of this problem, the potential relation between river sediment and nutrient discharges and degradation of coral reefs surrounding Puerto Rico was studied...
Authors
M. C. Larsen, R.M.T. Webb
Using a coupled groundwater/surface-water model to predict climate-change impacts to lakes in the Trout Lake Watershed, northern Wisconsin Using a coupled groundwater/surface-water model to predict climate-change impacts to lakes in the Trout Lake Watershed, northern Wisconsin
A major focus of the U.S. Geological Survey’s Trout Lake Water, Energy, and Biogeochemical Budgets (WEBB) project is the development of a watershed model to allow predictions of hydrologic response to future conditions including land-use and climate change. The coupled groundwater/surface-water model GSFLOW was chosen for this purpose because it could easily incorporate an existing...
Authors
Randall J. Hunt, John F. Walker, Steven L. Markstrom, Lauren E. Hay, John Doherty
Pesticide fate and transport throughout unsaturated zones in five agricultural settings, USA Pesticide fate and transport throughout unsaturated zones in five agricultural settings, USA
Pesticide transport through the unsaturated zone is a function of chemical and soil characteristics, application, and water recharge rate. The fate and transport of 82 pesticides and degradates were investigated at five different agricultural sites. Atrazine and metolachlor, as well as several of the degradates of atrazine, metolachlor, acetochlor, and alachlor, were frequently detected...
Authors
T.C. Hancock, Mark W. Sandstrom, J. R. Vogel, R.M.T. Webb, E.R. Bayless, J.E. Barbash
Simulated fate and transport of metolachlor in the unsaturated zone, Maryland, USA Simulated fate and transport of metolachlor in the unsaturated zone, Maryland, USA
An unsaturated-zone transport model was used to examine the transport and fate of metolachlor applied to an agricultural site in Maryland, USA. The study site was instrumented to collect data on soil-water content, soil-water potential, ground water levels, major ions, pesticides, and nutrients from the unsaturated zone during 2002-2004. The data set was enhanced with site-specific...
Authors
E.R. Bayless, P. D. Capel, J.E. Barbash, R.M.T. Webb, T.L.C. Hancock, D.C. Lampe
Variations in pesticide leaching related to land use, pesticide properties, and unsaturated zone thickness Variations in pesticide leaching related to land use, pesticide properties, and unsaturated zone thickness
Pesticide leaching through variably thick soils beneath agricultural fields in Morgan Creek, Maryland was simulated for water years 1995 to 2004 using LEACHM (Leaching Estimation and Chemistry Model). Fifteen individual models were constructed to simulate five depths and three crop rotations with associated pesticide applications. Unsaturated zone thickness averaged 4.7 m but reached a...
Authors
R.M.T. Webb, M.E. Wieczorek, B. T. Nolan, T.C. Hancock, Mark W. Sandstrom, J.E. Barbash, E.R. Bayless, R. W. Healy, J. Linard
Land-use effects on erosion, sediment yields, and reservoir sedimentation: A case study in the Lago Loiza Basin, Puerto Rico Land-use effects on erosion, sediment yields, and reservoir sedimentation: A case study in the Lago Loiza Basin, Puerto Rico
Lago Loíza impounded in 1953 to supply San Juan, Puerto Rico, with drinking water; by 1994, it had lost 47% of its capacity. To characterize sedimentation in Lago Loíza, a study combining land-use history, hillslope erosion rates, and subbasin sediment yields was conducted. Sedimentation rates during the early part of the reservoir’s operation (1953– 1963) were slightly higher than the...
Authors
Allen C. Gellis, Richard M. T. Webb, S. C. McIntyre, William J. Wolfe
Science and Products
Filter Total Items: 37
Potential effects of runoff, fluvial sediment, and nutrient discharges on the coral reefs of Puerto Rico Potential effects of runoff, fluvial sediment, and nutrient discharges on the coral reefs of Puerto Rico
Coral reefs, the foundation and primary structure of many highly productive and diverse tropical marine ecosystems, have been degraded by human activity in much of the earth's tropical oceans. To contribute to improved understanding of this problem, the potential relation between river sediment and nutrient discharges and degradation of coral reefs surrounding Puerto Rico was studied...
Authors
M. C. Larsen, R.M.T. Webb
Using a coupled groundwater/surface-water model to predict climate-change impacts to lakes in the Trout Lake Watershed, northern Wisconsin Using a coupled groundwater/surface-water model to predict climate-change impacts to lakes in the Trout Lake Watershed, northern Wisconsin
A major focus of the U.S. Geological Survey’s Trout Lake Water, Energy, and Biogeochemical Budgets (WEBB) project is the development of a watershed model to allow predictions of hydrologic response to future conditions including land-use and climate change. The coupled groundwater/surface-water model GSFLOW was chosen for this purpose because it could easily incorporate an existing...
Authors
Randall J. Hunt, John F. Walker, Steven L. Markstrom, Lauren E. Hay, John Doherty
Pesticide fate and transport throughout unsaturated zones in five agricultural settings, USA Pesticide fate and transport throughout unsaturated zones in five agricultural settings, USA
Pesticide transport through the unsaturated zone is a function of chemical and soil characteristics, application, and water recharge rate. The fate and transport of 82 pesticides and degradates were investigated at five different agricultural sites. Atrazine and metolachlor, as well as several of the degradates of atrazine, metolachlor, acetochlor, and alachlor, were frequently detected...
Authors
T.C. Hancock, Mark W. Sandstrom, J. R. Vogel, R.M.T. Webb, E.R. Bayless, J.E. Barbash
Simulated fate and transport of metolachlor in the unsaturated zone, Maryland, USA Simulated fate and transport of metolachlor in the unsaturated zone, Maryland, USA
An unsaturated-zone transport model was used to examine the transport and fate of metolachlor applied to an agricultural site in Maryland, USA. The study site was instrumented to collect data on soil-water content, soil-water potential, ground water levels, major ions, pesticides, and nutrients from the unsaturated zone during 2002-2004. The data set was enhanced with site-specific...
Authors
E.R. Bayless, P. D. Capel, J.E. Barbash, R.M.T. Webb, T.L.C. Hancock, D.C. Lampe
Variations in pesticide leaching related to land use, pesticide properties, and unsaturated zone thickness Variations in pesticide leaching related to land use, pesticide properties, and unsaturated zone thickness
Pesticide leaching through variably thick soils beneath agricultural fields in Morgan Creek, Maryland was simulated for water years 1995 to 2004 using LEACHM (Leaching Estimation and Chemistry Model). Fifteen individual models were constructed to simulate five depths and three crop rotations with associated pesticide applications. Unsaturated zone thickness averaged 4.7 m but reached a...
Authors
R.M.T. Webb, M.E. Wieczorek, B. T. Nolan, T.C. Hancock, Mark W. Sandstrom, J.E. Barbash, E.R. Bayless, R. W. Healy, J. Linard
Land-use effects on erosion, sediment yields, and reservoir sedimentation: A case study in the Lago Loiza Basin, Puerto Rico Land-use effects on erosion, sediment yields, and reservoir sedimentation: A case study in the Lago Loiza Basin, Puerto Rico
Lago Loíza impounded in 1953 to supply San Juan, Puerto Rico, with drinking water; by 1994, it had lost 47% of its capacity. To characterize sedimentation in Lago Loíza, a study combining land-use history, hillslope erosion rates, and subbasin sediment yields was conducted. Sedimentation rates during the early part of the reservoir’s operation (1953– 1963) were slightly higher than the...
Authors
Allen C. Gellis, Richard M. T. Webb, S. C. McIntyre, William J. Wolfe