Richard G Niswonger (Former Employee)
Science and Products
Filter Total Items: 17
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MODFLOW-NWT, a Newton formulation for MODFLOW-2005 MODFLOW-NWT, a Newton formulation for MODFLOW-2005
This report documents a Newton formulation of MODFLOW-2005, called MODFLOW-NWT. MODFLOW-NWT is a standalone program that is intended for solving problems involving drying and rewetting nonlinearities of the unconfined groundwater-flow equation. MODFLOW-NWT must be used with the Upstream-Weighting (UPW) Package for calculating intercell conductances in a different manner than is done in...
Authors
Richard G. Niswonger, Sorab Panday, Motomu Ibaraki
Comment on "Evaluating interactions between groundwater and vadose zone using the HYDRUS-based flow package for MODFLOW" by Navin Kumar C. Twarakavi, Jirka Šimůnek and Sophia Seo Comment on "Evaluating interactions between groundwater and vadose zone using the HYDRUS-based flow package for MODFLOW" by Navin Kumar C. Twarakavi, Jirka Šimůnek and Sophia Seo
Twarakavi et al (2008) compared four packages that can be used to estimate recharge for regional-scale groundwater flow simulations using MODFLOW (Harbaugh, 2005). This comment is focused on the comparisons made between two of these packages, namely, UZF1 (Niswonger et al., 2006) and a derivative of HYDRUS referred to herein as HYDRUS (Seo et al., 2007). In their paper, Twarakavi et al....
Authors
R.G. Niswonger, David E. Prudic
GSFLOW - Coupled Ground-Water and Surface-Water Flow Model Based on the Integration of the Precipitation-Runoff Modeling System (PRMS) and the Modular Ground-Water Flow Model (MODFLOW-2005) GSFLOW - Coupled Ground-Water and Surface-Water Flow Model Based on the Integration of the Precipitation-Runoff Modeling System (PRMS) and the Modular Ground-Water Flow Model (MODFLOW-2005)
The need to assess the effects of variability in climate, biota, geology, and human activities on water availability and flow requires the development of models that couple two or more components of the hydrologic cycle. An integrated hydrologic model called GSFLOW (Ground-water and Surface-water FLOW) was developed to simulate coupled ground-water and surface-water resources. The new...
Authors
Steven L. Markstrom, Richard G. Niswonger, R. Steven Regan, David E. Prudic, Paul M. Barlow
Influence of perched groundwater on base flow Influence of perched groundwater on base flow
Analysis with a three‐dimensional variably saturated groundwater flow model provides a basic understanding of the interplay between streams and perched groundwater. A simplified, layered model of heterogeneity was used to explore these relationships. Base flow contribution from perched groundwater was evaluated with regard to varying hydrogeologic conditions, including the size and...
Authors
Richard G. Niswonger, Graham E. Fogg
Method for estimating spatially variable seepage loss and hydraulic conductivity in intermittent and ephemeral streams Method for estimating spatially variable seepage loss and hydraulic conductivity in intermittent and ephemeral streams
A method is presented for estimating seepage loss and streambed hydraulic conductivity along intermittent and ephemeral streams using streamflow front velocities in initially dry channels. The method uses the kinematic wave equation for routing streamflow in channels coupled to Philip's equation for infiltration. The coupled model considers variations in seepage loss both across and...
Authors
R.G. Niswonger, David E. Prudic, G.E. Fogg, David A. Stonestrom, E.M. Buckland
Streambed infiltration and ground-water flow from the Trout Creek drainage, an intermittent tributary to the Humboldt River, north-central Nevada Streambed infiltration and ground-water flow from the Trout Creek drainage, an intermittent tributary to the Humboldt River, north-central Nevada
Ground water is abundant in many alluvial basins of the Basin and Range Physiographic Province of the western United States. Water enters these basins by infiltration along intermittent and ephemeral channels, which originate in the mountainous regions before crossing alluvial fans and piedmont alluvial plains. Water also enters the basins as subsurface ground-water flow directly from...
Authors
David E. Prudic, Richard G. Niswonger, James R. Harrill, James L. Wood
Documentation of the Unsaturated-Zone Flow (UZF1) Package for modeling Unsaturated Flow Between the Land Surface and the Water Table with MODFLOW-2005 Documentation of the Unsaturated-Zone Flow (UZF1) Package for modeling Unsaturated Flow Between the Land Surface and the Water Table with MODFLOW-2005
Percolation of precipitation through unsaturated zones is important for recharge of ground water. Rain and snowmelt at land surface are partitioned into different pathways including runoff, infiltration, evapotranspiration, unsaturated-zone storage, and recharge. A new package for MODFLOW-2005 called the Unsaturated-Zone Flow (UZF1) Package was developed to simulate water flow and...
Authors
Richard G. Niswonger, David E. Prudic, R. Steven Regan
Trends in streamflow on the Humboldt River between Elko and Imlay, Nevada, 1950-99 Trends in streamflow on the Humboldt River between Elko and Imlay, Nevada, 1950-99
No abstract available.
Authors
David E. Prudic, Richard G. Niswonger, Russell W. Plume
River-aquifer interactions, geologic heterogeneity, and low-flow management River-aquifer interactions, geologic heterogeneity, and low-flow management
Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard materials beneath the river. Low flows are often important ecologically. Numerical simulations were used to assess how textural heterogeneity of an alluvial system influences river seepage and low flows. The Cosumnes River in...
Authors
J.H. Fleckenstein, R.G. Niswonger, G.E. Fogg
Incorporating seepage losses into the unsteady streamflow equations for simulating intermittent flow along mountain front streams Incorporating seepage losses into the unsteady streamflow equations for simulating intermittent flow along mountain front streams
Seepage losses along numerous mountain front streams that discharge intermittently onto alluvial fans and piedmont alluvial plains are an important source of groundwater in the Basin and Range Province of the Western United States. Determining the distribution of seepage loss along mountain front streams is important when assessing groundwater resources of the region. Seepage loss along...
Authors
R.G. Niswonger, David E. Prudic, G. Pohll, J. Constantz
Documentation of the Streamflow-Routing (SFR2) Package to Include Unsaturated Flow Beneath Streams - A Modification to SFR1 Documentation of the Streamflow-Routing (SFR2) Package to Include Unsaturated Flow Beneath Streams - A Modification to SFR1
Many streams in the United States, especially those in semiarid regions, have reaches that are hydraulically disconnected from underlying aquifers. Ground-water withdrawals have decreased water levels in valley aquifers beneath streams, increasing the occurrence of disconnected streams and aquifers. The U.S. Geological Survey modular ground-water model (MODFLOW-2000) can be used to model...
Authors
Richard G. Niswonger, David E. Prudic
Analysis of temperature profiles for investigating stream losses beneath ephemeral channels Analysis of temperature profiles for investigating stream losses beneath ephemeral channels
Continuous estimates of streamflow are challenging in ephemeral channels. The extremely transient nature of ephemeral streamflows results in shifting channel geometry and degradation in the calibration of streamflow stations. Earlier work suggests that analysis of streambed temperature profiles is a promising technique for estimating streamflow patterns in ephemeral channels. The present...
Authors
Jim Constantz, Amy E. Stewart, Richard G. Niswonger, Lisa Sarma
Science and Products
Filter Total Items: 17
No Result Found
Filter Total Items: 63
MODFLOW-NWT, a Newton formulation for MODFLOW-2005 MODFLOW-NWT, a Newton formulation for MODFLOW-2005
This report documents a Newton formulation of MODFLOW-2005, called MODFLOW-NWT. MODFLOW-NWT is a standalone program that is intended for solving problems involving drying and rewetting nonlinearities of the unconfined groundwater-flow equation. MODFLOW-NWT must be used with the Upstream-Weighting (UPW) Package for calculating intercell conductances in a different manner than is done in...
Authors
Richard G. Niswonger, Sorab Panday, Motomu Ibaraki
Comment on "Evaluating interactions between groundwater and vadose zone using the HYDRUS-based flow package for MODFLOW" by Navin Kumar C. Twarakavi, Jirka Šimůnek and Sophia Seo Comment on "Evaluating interactions between groundwater and vadose zone using the HYDRUS-based flow package for MODFLOW" by Navin Kumar C. Twarakavi, Jirka Šimůnek and Sophia Seo
Twarakavi et al (2008) compared four packages that can be used to estimate recharge for regional-scale groundwater flow simulations using MODFLOW (Harbaugh, 2005). This comment is focused on the comparisons made between two of these packages, namely, UZF1 (Niswonger et al., 2006) and a derivative of HYDRUS referred to herein as HYDRUS (Seo et al., 2007). In their paper, Twarakavi et al....
Authors
R.G. Niswonger, David E. Prudic
GSFLOW - Coupled Ground-Water and Surface-Water Flow Model Based on the Integration of the Precipitation-Runoff Modeling System (PRMS) and the Modular Ground-Water Flow Model (MODFLOW-2005) GSFLOW - Coupled Ground-Water and Surface-Water Flow Model Based on the Integration of the Precipitation-Runoff Modeling System (PRMS) and the Modular Ground-Water Flow Model (MODFLOW-2005)
The need to assess the effects of variability in climate, biota, geology, and human activities on water availability and flow requires the development of models that couple two or more components of the hydrologic cycle. An integrated hydrologic model called GSFLOW (Ground-water and Surface-water FLOW) was developed to simulate coupled ground-water and surface-water resources. The new...
Authors
Steven L. Markstrom, Richard G. Niswonger, R. Steven Regan, David E. Prudic, Paul M. Barlow
Influence of perched groundwater on base flow Influence of perched groundwater on base flow
Analysis with a three‐dimensional variably saturated groundwater flow model provides a basic understanding of the interplay between streams and perched groundwater. A simplified, layered model of heterogeneity was used to explore these relationships. Base flow contribution from perched groundwater was evaluated with regard to varying hydrogeologic conditions, including the size and...
Authors
Richard G. Niswonger, Graham E. Fogg
Method for estimating spatially variable seepage loss and hydraulic conductivity in intermittent and ephemeral streams Method for estimating spatially variable seepage loss and hydraulic conductivity in intermittent and ephemeral streams
A method is presented for estimating seepage loss and streambed hydraulic conductivity along intermittent and ephemeral streams using streamflow front velocities in initially dry channels. The method uses the kinematic wave equation for routing streamflow in channels coupled to Philip's equation for infiltration. The coupled model considers variations in seepage loss both across and...
Authors
R.G. Niswonger, David E. Prudic, G.E. Fogg, David A. Stonestrom, E.M. Buckland
Streambed infiltration and ground-water flow from the Trout Creek drainage, an intermittent tributary to the Humboldt River, north-central Nevada Streambed infiltration and ground-water flow from the Trout Creek drainage, an intermittent tributary to the Humboldt River, north-central Nevada
Ground water is abundant in many alluvial basins of the Basin and Range Physiographic Province of the western United States. Water enters these basins by infiltration along intermittent and ephemeral channels, which originate in the mountainous regions before crossing alluvial fans and piedmont alluvial plains. Water also enters the basins as subsurface ground-water flow directly from...
Authors
David E. Prudic, Richard G. Niswonger, James R. Harrill, James L. Wood
Documentation of the Unsaturated-Zone Flow (UZF1) Package for modeling Unsaturated Flow Between the Land Surface and the Water Table with MODFLOW-2005 Documentation of the Unsaturated-Zone Flow (UZF1) Package for modeling Unsaturated Flow Between the Land Surface and the Water Table with MODFLOW-2005
Percolation of precipitation through unsaturated zones is important for recharge of ground water. Rain and snowmelt at land surface are partitioned into different pathways including runoff, infiltration, evapotranspiration, unsaturated-zone storage, and recharge. A new package for MODFLOW-2005 called the Unsaturated-Zone Flow (UZF1) Package was developed to simulate water flow and...
Authors
Richard G. Niswonger, David E. Prudic, R. Steven Regan
Trends in streamflow on the Humboldt River between Elko and Imlay, Nevada, 1950-99 Trends in streamflow on the Humboldt River between Elko and Imlay, Nevada, 1950-99
No abstract available.
Authors
David E. Prudic, Richard G. Niswonger, Russell W. Plume
River-aquifer interactions, geologic heterogeneity, and low-flow management River-aquifer interactions, geologic heterogeneity, and low-flow management
Low river flows are commonly controlled by river-aquifer exchange, the magnitude of which is governed by hydraulic properties of both aquifer and aquitard materials beneath the river. Low flows are often important ecologically. Numerical simulations were used to assess how textural heterogeneity of an alluvial system influences river seepage and low flows. The Cosumnes River in...
Authors
J.H. Fleckenstein, R.G. Niswonger, G.E. Fogg
Incorporating seepage losses into the unsteady streamflow equations for simulating intermittent flow along mountain front streams Incorporating seepage losses into the unsteady streamflow equations for simulating intermittent flow along mountain front streams
Seepage losses along numerous mountain front streams that discharge intermittently onto alluvial fans and piedmont alluvial plains are an important source of groundwater in the Basin and Range Province of the Western United States. Determining the distribution of seepage loss along mountain front streams is important when assessing groundwater resources of the region. Seepage loss along...
Authors
R.G. Niswonger, David E. Prudic, G. Pohll, J. Constantz
Documentation of the Streamflow-Routing (SFR2) Package to Include Unsaturated Flow Beneath Streams - A Modification to SFR1 Documentation of the Streamflow-Routing (SFR2) Package to Include Unsaturated Flow Beneath Streams - A Modification to SFR1
Many streams in the United States, especially those in semiarid regions, have reaches that are hydraulically disconnected from underlying aquifers. Ground-water withdrawals have decreased water levels in valley aquifers beneath streams, increasing the occurrence of disconnected streams and aquifers. The U.S. Geological Survey modular ground-water model (MODFLOW-2000) can be used to model...
Authors
Richard G. Niswonger, David E. Prudic
Analysis of temperature profiles for investigating stream losses beneath ephemeral channels Analysis of temperature profiles for investigating stream losses beneath ephemeral channels
Continuous estimates of streamflow are challenging in ephemeral channels. The extremely transient nature of ephemeral streamflows results in shifting channel geometry and degradation in the calibration of streamflow stations. Earlier work suggests that analysis of streambed temperature profiles is a promising technique for estimating streamflow patterns in ephemeral channels. The present...
Authors
Jim Constantz, Amy E. Stewart, Richard G. Niswonger, Lisa Sarma