Advective transport observations with MODPATH-OBS--documentation of the MODPATH observation process

Abstract

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.Suggested citation: Hanson, R.T., Kauffman, L.K., Hill, M.C., Dickinson, J.E., and Mehl, S.W., 2013, Advective transport observations with MODPATH-OBS-Documentation of the MODPATH observation process: U.S. Geological Survey Techniques and Methods book 6-chap. A42, 96 p., http: pubs.usgs.gov/tm/06/a42. iii PrefaceThe MODPATH-OBS computer program described in this report is designed to calculate simulated equivalents for observations (or predictions) related to groundwater transport that can be represented in a meaningful way using particle tracking. Generally this means that the observations relate to the movement of the center of a discrete plume, movement of position along a plume front selected to correct for the effects of dispersion and reactions not simulated by particle tracking, geochemical data that identify likely recharge areas, and other hydrologic features.MODPATH-OBS uses the particle tracking capabilities of MODPATH by acting as a postprocessor. MODPATH is a postprocessor for MODFLOW, so that the sequence of model runs generally required is MODFLOW, MODPATH, and MODPATH-OBS.The versions of MODFLOW and MODPATH that support MODPATH-OBS as documented in this report are MODFLOW-2000/2005 and MODFLOW-LGR (Mehl and Hill, 2005 and MODPATH (Pollock, 1994(Pollock, , 2012 or MODPATH-LGR (Dickinson and others, 2011). MODFLOW-LGR is derived from MODFLOW-2005(Harbaugh, 2005 and supports local grid refinement. MODFLOW-LGR simulations may include local grid refinement or may use a single grid. When a single grid is used, MODFLOW-LGR performs identically to the version of MODFLOW-2005 cited on the MODFLOW-LGR web page. MODPATH-LGR and MODPATH-OBS can use nearly all of the capabilities of MODFLOW-LGR. For example, simulations can be steady-state, transient, or a combination; model layers may be confined or convertible from confined to unconfined; all of the head-dependent boundary packages are supported and features simulated using the Streamflow-Routing (SFR) Package can be routed across grid boundaries. Limitations are discussed in this report. (Pollock, 1989(Pollock, , 1994(Pollock, , 2012 and supports the tracking of particles through locally refined grids. For a single grid and no observations, MODPATH-LGR performs similarly to the version of MODPATH cited on the MO...

Optimizing Recharge Area Delineation for Small- to Medium-Sized Groundwater Systems through Coupling Methods and Numerical Modeling: A Case Study of Linfen City, China

“…Additional methods employing travel time include uniform flow equations [17], time of travel equations [18], and HYBRID methods [19]. Some advanced approaches such as MODPATH-OBS incorporate decay processes into particle tracking [20], while others consider convection, dispersion, adsorption, and first-order decay through the backward-in-time solution of the convection-dispersion equation [21][22][23][24]. Numerous studies underscore the substantial impacts of factors like transient flow, generalized source-sink terms, anisotropy, and horizontal-vertical conductivity on the protection zone size and shape [25][26][27].…”

Capture zone delineation methodology based on the maximum concentration: Preventative groundwater well protection areas for heat exchange fluid mixtures

“…Capture zone delineation is often done using approaches based on the advective travel time, such as a particle tracking method (e.g., MODPATH) [ Pollock , ], uniform flow field equations or calculated fixed radius [ U.S. EPA , ], or the HYBRID method [ Paradis and Martel , ]. Recently, zero‐order and first‐order decay have also been introduced in particle tracking methods, e.g., MODPATH‐OBS [ Hanson et al ., ]. Other methods have been developed to account for both advection and dispersion in the delineation of capture zones, by applying the backward‐in‐time solution of the advection‐dispersion equation [ Uffink , ; Chin and Chittaluru , ; Neupauer and Wilson , ; Tosco and Sethi , ].…”