MODFLOW 6 and MODPATH 7 Models for Simulating Groundwater Flow and Nitrogen Transport in the Long Island, New York Aquifer System (ver. 2.0, January 2026)

This groundwater model application data release documents transient and steady-state regional and inset numerical models of the Long Island aquifer system that simulate groundwater flow and nitrogen transport for the period 1900-2019 using the US Geological Survey groundwater modeling software MODFLOW 6 (Langvin and others, 2017 and 2022). The development and calibration of the regional groundwater flow model is documented in Walter and others (2024). The development of the regional groundwater nitrogen transport model and inset groundwater flow and nitrogen transport models are documented in Jahn and Walter (2025). The particle-tracking algorithm MODPATH 7 (Pollock, 2016) was used to simulate advective transport in the aquifer, to delineate the areas at the water table that contribute recharge to coastal water bodies, and to estimate total travel times of water from the water table to discharge locations. Model input and output files included in this data release are documented in the readme.txt.

First posted August 2025, ver 1.0

Revised January 2026, ver 2.0

Version 1.0: In this version of the dataset, models MF7, MF8, and MF9 had 250x250-foot inset model arrays (such as recharge, nitrogen inputs, initial conditions) that were shifted north by 1 regional model rows (equivalent to 500 feet) and west by 1 regional model column (equivalent to 500 feet) due to a geospatial processing error. This resulted in the incorrect placement of those arrays relative to the inset coastlines. Additionally, the MF7 recharge input file (inset_historic_lgr/child-flow.rcha) points to a single average 2010-2019 recharge array for each of the 10 stress periods rather than the 10 unique arrays representing annual average recharge rates for each year from 2010-2019.

Version 2.0: This version of the dataset has been updated with correctly aligned inset model arrays for MF7, MF8, and MF9. The MF7 recharge input file has been updated to correctly point to the 10 annual average recharge arrays. Corresponding model output files have been updated.
References
Langevin, C.D., Hughes, J.D., Banta, E.R., Niswonger, R.G., Panday, Sorab, and Provost, A.M., 2017, Documentation for the MODFLOW 6 Groundwater Flow Model: U.S. Geological Survey Techniques and Methods, book 6, chap. A55, 197 p.

Langevin, C.D., Provost, A.M., Panday, Sorab, and Hughes, J.D., 2022, Documentation for the MODFLOW 6 Groundwater Transport Model: U.S. Geological Survey Techniques and Methods, book 6, chap. A61, 56 p.

Walter, D.A., Jahn, K.L., Masterson, J.P., Dressler, S.E., Finkelstein, J.S., and Monti, J., Jr., 2024, Simulation of Groundwater Flow in the Long Island, New York Regional Aquifer System for Pumping and Recharge Conditions From 1900 To 2019: U.S. Geological Survey Scientific Investigations Report 2024-5044, 114 p.

Jahn, K.L. and Walter, D.A, 2025, Assessing Legacy Nitrogen in Groundwater using Numerical Models of the Long Island, New York Aquifer System, Preprint on EarthArXiv

Pollock, D.W., 2016, User guide for MODPATH version 7—a particle-tracking model for MODFLOW: US Geological Survey Open-File Report 2016–1086.