Stressors and impacts

As Public Works Director of Nogales, Arizona, Alejandro Barcenas works to ensure a safe and secure water supply for the city’s 20,500 residents. His task isn’t easy: the city is located in an arid region just north of the United States–Mexico border, and its entire supply comes from groundwater.

Half of Nogales’ water comes from alluvial aquifers that are highly responsive to rainfall events. Though this convenient source of water recharges easily, it is also vulnerable to climate-related changes such as reduced precipitation and increased evaporation. The other half of the city’s groundwater comes from a lower-quality source—this water is more expensive to produce. To optimize the use of the two sources of groundwater into the future, Barcenas is contributing to the development of a modeling tool that simulates how the aquifers may change in response to climate.

Modeling groundwater processes

Based on surface hydrology, aquifer geology, and other conditions, hydrologists can develop useful mathematical models to represent surface and groundwater processes. By simulating the environment, precipitation, streamflow, infiltration, and extraction, these models can estimate the availability of water in aquifers over time. Enhancing these models by linking them to future precipitation scenarios can give water managers an opportunity to explore potential conditions, including the costs and benefits of various management strategies.

Developing a modeling tool

Along with other stakeholders, Barcenas provided input for the development of a modeling tool designed to answer aquifer management questions. The tool is made up of component models that link likely precipitation scenarios, through streamflow, to aquifer response. The sophisticated model simulates groundwater pumping and informs users how various strategies could affect the reliability of water supplies and the need for future storage capacity.

As a result of hydrologists, practitioners, and other stakeholders collaborating in the development of this tool, the model has the flexibility to enable users to explore a range of questions. For instance, in addition to his goal of providing water for the community, Barcenas is concerned with protecting riverside ecosystems as community assets. The model can help him explore how the needs of these ecosystems might be balanced with the city’s water needs.

Based on the success of early phases of their work, Barcenas will continue contributing to the effort to tailor the tool so it can meet the specific needs of managing Nogales’ water supply. As precipitation patterns change with changing climate, and as this type of modeling work progresses, communities that rely on climate-sensitive aquifers will be able to access models and use the results to fine-tune their water supply operations. Barcenas is convinced this approach will enhance the long-term sustainability of local groundwater resources and build climate resilience for Nogales.