Recharge Estimation for Transient Ground Water Modeling

Abstract

Reliable ground water models require both an accurate physical representation of the system and appropriate boundary conditions. While physical attributes are generally considered static, boundary conditions, such as ground water recharge rates, can be highly variable in both space and time. A practical methodology incorporating the hydrologic model HELP3 in conjunction with a geographic information system was developed to generate a physically based and highly detailed recharge boundary condition for ground water modeling. The approach uses daily precipitation and temperature records in addition to land use/land cover and soils data. The importance of the method in transient ground water modeling is demonstrated by applying it to a MODFLOW modeling study in New Jersey. In addition to improved model calibration, the results from the study clearly indicate the importance of using a physically based and highly detailed recharge boundary condition in ground water quality modeling, where the detailed knowledge of the evolution of the ground water flowpaths is imperative. The simulated water table is within 0.5 m of the observed values using the method, while the water levels can differ by as much as 2 m using uniform recharge conditions. The results also show that the combination of temperature and precipitation plays an important role in the amount and timing of recharge in cooler climates. A sensitivity analysis further reveals that increasing the leaf area index, the evaporative zone depth, or the curve number in the model will result in decreased recharge rates over time, with the curve number having the greatest impact.

Groundwater Recharge Assessment in the Chateauguay River Watershed

“…The other assessment methods were mainly used to validate recharge results obtained from the HELP model (details are provided in Croteau, 2006). HELP has also been applied for groundwater recharge assessment in numerous hydrogeological studies ( Jyrkama et al, 2002;Gogolev, 2002;Scibek and Allen, 2006a;2006b). But given the comprehensive set of modelled hydrologic processes, for given climate conditions, considerable over-or under-estimation of the water balance parameters were occasionally obtained.…”

Application of the Versatile Soil Moisture Budget Model to Estimate Evaporation from Prairie Grassland

“…Compared to precipitation, which is measurable at least on a point scale, evaporation estimates have a large degree of uncertainty. The accuracy of model-simulated groundwater recharge has been tested by the comparison of simulated groundwater level to observation data ( Jyrkama et al, 2002) or the comparison of land-surface model outputs to those of more sophisticated unsaturated flow models (Loukili et al, 2008). However, simulated evaporation in these models has rarely been compared against measured evaporation in the field.…”

“…Numerical groundwater flow models coupled with hydrological land-surface models have been recognized as an effective tool for the sustainable development and management of groundwater resources in many parts of the world (Sophocleous and Perkins, 2000;Lubczynski and Gurwin, 2005, and references therein). Among the recent progresses in Canada is the coupling of a three-dimensional groundwater flow model MODFLOW (McDonald and Harbaugh, 1996) with a land-surface model called Hydrologic Evaluation of Landfill Performance (HELP) by Jyrkama et al (2002) and Scibek and Allen (2006). In these coupled models, the primary function of the land-surface model is to provide spatially distributed, transient groundwater recharge flux.…”

An Integrated Field Assessment of Groundwater Recharge

“…Nevertheless, groundwater modelers, planners, and policy makers frequently use a single recharge value for an entire watershed calculated as an assumed fraction of the annual average precipitation or as determined by model calibration. Use of a single annual value may be inappropriate, depending on the application, and, consequently, may invalidate model results and predictions, particularly where small scale or detailed flow path delineation is required over time [8,17].…”

“…There has been extensive research on recharge estimation at a variety of scales [2][3][4], including studies that assess spatial and temporal recharge variability [5][6][7][8][9][10][11][12][13][14][15][16]. Nevertheless, groundwater modelers, planners, and policy makers frequently use a single recharge value for an entire watershed calculated as an assumed fraction of the annual average precipitation or as determined by model calibration.…”