Date of Award

Spring 5-8-2020

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Earth Sciences

Advisor

Andrew S. Reeve

Second Committee Member

Ryan P. Gordon

Third Committee Member

Gustavo A. Sarmiento Perez

Abstract

About 160,000 inhabitants live in the 1,600 square kilometers Carraipia River Basin located in northeastern Colombia and northwestern Venezuela. Historically, water has been supplied to the inhabitants in this arid coastal region by shallow dug wells. Water supplied by these wells is frequently of poor quality due to high concentrations of total dissolved solids (TDS). Recently, due to the increasing demand for water, numerous deep wells have been drilled in the region to supply water to rural and urban areas from deep aquifers. Colombian agencies seek more quantitative information on groundwater resources, driven by increasingly severe water shortages over the past decade that have adversely affected the quality of life for the people living in La Guajira state.

A groundwater flow computer model has been constructed to provide a tool for assisting with the management of groundwater resources in the Carraipia River Basin. This model is based on geologic maps, hydraulic test wells, geologic field data, and other sparse information to create a highly idealized model of the hydrostratigraphy of this basin. Before creating the three-dimensional groundwater model, stratigraphic columns and cross sections were prepared to guide conceptualization of the idealized groundwater flow model. Available data used to develop the conceptual hydrogeological model includes the following: precipitation data measured in the drainage basin (CORPOGUAJIRA et al., 2006), evapotranspiration data calculated from temperature measurements (CORPOGUAJIRA et al., 2006), hydraulic well tests (Colombian Geological Survey, personal communication), and hydraulic head data measured in shallow wells. The model includes interpreted and conceptualized aquifer parameters, such as hydraulic conductivity (K), and estimated current and future pumping rates. Finally, water table data scattered over the basin area are used to calibrate the model.

The regional groundwater system is represented mathematically, using the software ModelMuse and MODFLOW-2005 that discretizes the volume of the basin and the timing of the hydraulic stresses, and balances groundwater flow equations based on input files that define hydraulic stresses. The goal of this project is to use the current stipulated pumping regime in the Carraipia Basin to determine if this groundwater extraction is environmentally sustainable. A secondary goal is to assess how groundwater extraction and other hydraulic stresses impacts the extent of saltwater intrusion.

Currently, data are very sparse and topography is poorly constrained. The groundwater model is an idealized representation to establish a starting point for future refinement. In addition, improving the understanding of groundwater flow processes, this model:

  • Can be used to help estimate sustainable yields,
  • Can simulate the impact of different pumping scenarios,
  • Can help identify critical data needed to improve the hydrogeologic characterization of the Carraipia Basin.

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