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USGS2023

Groundwater prospecting using a multi-technique framework in the lower Casas Grandes Basin, Chihuahua, México

Groundwater is a strategic resource for economic development, social justice, environmental sustainability, and water governance. The lower Casas Grandes River Basin, located in the state of Chihuahua, México, is in a semi-arid region with increasing groundwater demand and regional challenges such as drought and depletion of aquifers. Even though there is official information about the availability of groundwater, a comprehensive aquifer characterization requiring an interdisciplinary investigation using a diverse suite of tools and multiple data sources has yet to be carried out. This study presents a multi-technique framework to evaluate potential sites to drill for groundwater resources and reduce the risk of unsuccessful drilling. The main components of the methodology include wellhead leveling correction with a differential global positioning survey to define piezometric levels, principal component analysis using LANDSAT-8 images, application of geospatial tools, geophysics analysis using time domain electromagnetic surveys (TDES) and vertical electric soundings (VES), and structural geohydrology to define aquifer characteristics. The results showed that using the proposed framework steps improved the possibility of identifying subsurface layers with lower resistivity values that could be related to groundwater. Low resistivity values (35 Ohm-m) were found at depths from 50 to 85 m at sites where the regional static water level reached a depth of 245 m, indicating the potential location of a shallow groundwater resource at a site where the intersection of a fracture trace was identified. This procedure can be used in other regions in the world where limited information is available for groundwater exploration, thus reducing the risk of drilling dry wells in complex hydrogeological environments.

Lower Casas Grandes Basin, Chihuahua↗

USGS2022

Improved method for simulating groundwater inundation using the MODFLOW 6 Lake Transport Package

Groundwater inundation due to sea level rise can affect island and coastal freshwater resources by exposing water tables to direct, continuous evaporation. Numerical simulations of groundwater inundation effects on coastal and island aquifers have been limited by an inability to simulate solute transport and variable density flow between the aquifer and lakes formed by groundwater inundation. Consequently, we contributed to the development of a new tool, the Lake Transport Package, for MODFLOW 6 that can calculate solute concentrations within lakes and allows for variable density flow between lakes and aquifers. Here we use groundwater inundation as an example application to showcase the functionality of the Lake Transport Package and the advantages of using this tool over past methods of representing groundwater inundation. We developed hypothetical island simulations based on hydrogeological characteristics of the Bahamas. Multiple sea level rise and lake evaporation rates were simulated to evaluate the effects of groundwater inundation on freshwater lens size for different climates. The results demonstrate the ability of the Lake Transport Package to calculate the solute concentration of the lake for transient simulations, including hypersaline concentrations. Higher sea level rise and greater lake evaporation rates lead to a greater loss of the freshwater lens and higher lake salinity. The formation of a lake and corresponding expansion due to groundwater inundation increases the loss of freshwater by 6–36%, depending on the lake evaporation rate. These simulations validate the performance and demonstrate usefulness of the Lake Transport Package as a tool in representing groundwater inundation.

Groundwater↗