SUTRA model used to evaluate long-term groundwater availability in the Waihee, Iao, and Waikapu aquifer systems, Maui, Hawaii

Groundwater levels have declined since the 1940s in the Wailuku area of central Maui, Hawaii,
on the eastern flank of West Maui volcano, mainly in response to increased groundwater
withdrawals. Available data since the 1980s also indicate a thinning of the freshwater lens and an
increase in chloride concentrations of pumped water from production wells. These trends,
combined with projected increases in demand for groundwater in central Maui, have led to
concerns over groundwater availability and have highlighted a need to improve understanding of
the hydrologic effects of proposed groundwater withdrawals in the Waihee, Iao, and Waikapu
areas of central Maui. A three-dimensional, variable-density solute-transport model (SUTRA) was
developed to evaluate the effects of seven selected withdrawal/recharge scenarios on water
levels and salinity of groundwater in central Maui, Hawaii. The model was constructed using
water-level and salinity data available for the period from 1926 to 2012. Groundwater recharge for
the model was estimated using a daily water budget for the period of interest. Inflow of
groundwater at the model boundaries was estimated from an existing island-wide numerical
groundwater-flow model (Izuka and others, 2021, available at https://doi.org/10.3133/sir20205126).
The data release also includes the SUTRA source code and executable file used to run the
simulations. The SUTRA code was modified to include a simplified representation of water-table
storage (Gingerich, 2008, available at https://pubs.usgs.gov/sir/2008/5236/; Gingerich and Engott,
2012, available at https://pubs.usgs.gov/sir/2012/5010/). This USGS data release contains all of
the input and output files for the simulations described in the associated model documentation
report (https://doi.org/10.3133/sir20215113).