Background 

Chronic problems in its wastewater system, including sanitary sewer overflows resulting in untreated transboundary discharges to the U.S., prompted the City, in coordination with NADBank, the Mexican National Water Commission (CONAGUA) and the U.S. Environmental Protection Agency (EPA), to evaluate the underlying conditions causing the wastewater infrastructure issues. Among the suspected causes was significant inflow and infiltration of water into the sewer system due to leaks in the water distribution system.

A study conducted in 2022 confirmed that the volume of water extracted and distributed within the city was more than twice the national per capita average established by CONAGUA. The study concluded that most of this water is being lost in distribution, creating infiltration problems in the sewer system. Moreover, due to this high water consumption, the shared aquifer with Naco, Arizona, is also vulnerable to over pumping and an accelerated depletion rate.

One of the actions identified to remedy this situation is the implementation of a metering system so that the utility can obtain accurate data on actual water used by its customers, quantify water losses in the distribution system and eventually pinpoint their source. Armed with this knowledge, the utility will also be in a better position to take actions aimed at promoting water conservation among its users, as well as reduce its pumping requirements and the associated costs.

To offset the energy needed to operate the water pumping facilities and improve the sustainability of the utility, the State of Sonora committed to providing an alternative energy source generated by renewable energy. Although the solar panels and related components were installed in 2018, the system is not operational and requires additional investments to be connected to the grid. OOMAPAS also removed and stored some of the panels to protect them from vandalism or other threats. Therefore, OOMAPAS is also seeking support to complete the connection and start-up of the solar energy system.

Description

The Project consists of installing water meters and completing the connection and startup of the existing solar energy system for three water production wells. The main project components include:

• Purchase of up to 2,400 remote-read water meters and installation of 2,326 meters for existing water accounts;
• Installation of solar energy system, consisting of 1,451 photovoltaic modules with a nominal capacity of 250-255 watts mounted on fixed arrays, along with 16 inverters coupled to three transformers; and
• Purchase and installation of cables to connect the solar energy system to the power grid, reinstallation of panels removed and stored by OOMAPAS, and start-up and testing of the new energy source. Project implementation will include disconnecting each solar panel from its junction box and checking that the panel, relay switches, fuse connectors and cables are all in good working order.

The solar panels and related components were installed in 2018 with funding from the State of Sonora, the Municipality of Naco and OOMAPAS. CAP funding will be used to purchase and install the water meters and to complete the connection and start-up of the solar energy system.

Benefits

The project will improve the sustainability of the drinking water system and water resource management by metering actual water use, which will provide a reliable basis for billing and revenue generation, detecting water losses and applying water conservation strategies, including implementing a water conservation rate structure and an improved leak detection program.

The project will also offset 100% of the energy required to operate three production wells with a solar energy system that is expected to generate approximately 767.8 megawatt-hours of electricity during the first year of operation and thus help prevent the emission of an estimated 352.5 metric tons/year of carbon dioxide, 1.06 metric tons/year of nitrogen oxides and 2.79 metric tons/year of sulfur dioxide. 

Additionally, water metering and an alternative energy system are expected to reduce pumping requirements and operating costs, as well as improve the overall financial health and institutional capacity of the utility.