Coastal Lowlands Regional Groundwater Availability Study

Science Center Objects

USGS is undertaking a 5-year study to assess groundwater availability for the aquifers proximal to the Gulf of Mexico from the Texas-Mexico border through the panhandle of Florida, known as the Coastal Lowlands Aquifer System (CLAS). This study is one of several within the Regional Groundwater Availability Studies of the USGS Water Availability and Use Science Program.

Groundwater from the CLAS is used mainly for municipal, agricultural, and industrial supply. The study will focus on quantifying the current status and long-term trends of groundwater availability within the CLAS.

 

Learn More at the CLAS Website

 

Conceptual model development

The team will develop an updated conceptual model of the CLAS, which will lead to initial estimates of major water-budget components such as recharge, surface-water/groundwater exchange, and coastal discharge. These datasets will be derived from a variety of sources, including remotely sensed datasets and outputs from other models. These independent estimates of important water budget components will not only provide important, early insights into the groundwater available within the CLAS, but will also be used in construction of the groundwater model datasets, conditioning of the model to historical data, and for quantifying the uncertainty of system properties and water-budget components.

Purpose-driven modeling

The modeling analysis will focus on estimating, in a stochastic sense, water-budget components and potential subsidence under different climate and water-use scenarios. First, a baseline, forecast simulation will be developed using long-term average climate conditions and water use. Then both long-term, low- intensity drought and short-term, high-intensity drought scenarios will be developed to quantify the response of the CLAS to different combinations of climate change and water usage.

Uncertainty analysis

In contrast to more traditional modeling, the CLAS model will be developed within an uncertainty quantification (UQ) framework using recently-developed USGS tools, PEST++ and pyEMU. Within this framework, we will formally and rigorously define the uncertainty in the model throughout the model development process. 

Land-surface subsidence

Land-surface subsidence is a major issue in the CLAS study area, most notably within the Houston-Galveston Texas region, as well as in Baton Rouge, Louisiana. In the Houston-Galveston region, water-level data from wells have been collected and analyzed annually to create water-level altitude and change maps since 1977. The simulation of subsidence will be implemented through the new subsidence package for MODFLOW6, which is being developed as a part of this study.