The Middle Trinity Groundwater Conservation District (MTGCD) has announced the launch of a new online Rainwater Harvesting Calculator, designed to help Central Texas residents better understand the potential of collecting and storing rainwater for household use.
The calculator, available at https://mtgcd.lre-up.com/ and also through middletrinitygcd.org under the Education tab, gives residents a practical way to explore rainwater harvesting as a supplement to traditional water supplies. Users can enter an address or select a property on an interactive map to see how much rainfall might be captured from their roof. By factoring in roof size, roof type, and capture efficiency, the tool estimates the volume of water that could be collected in a typical year.
The Rainwater Harvesting Calculator draws on over 40 years of data from the PRISM Climate Database, developed at Oregon State University. PRISM blends weather station data with local geography to create accurate, location-specific rainfall maps widely used by the U.S. Department of Agriculture (USDA), National Oceanic and Atmospheric Administration (NOAA), and Environmental Protection Agency (EPA). Using this trusted source, the calculator provides more precise estimates than broad regional averages.
In addition to collection potential, the tool simulates water use and storage over time. It models indoor demand year-round and outdoor demand during warmer months, then shows how a cistern would fill and empty. This helps residents see how different tank sizes might perform under their specific conditions. The calculator also offers a timeseries analysis, illustrating how a system would have fared during past drought years. By exploring these scenarios, residents gain a clearer picture of how resilient a rainwater system might be during extended dry periods.
MTGCD emphasizes that the Rainwater Harvesting Calculator is intended as a planning and educational resource, not a substitute for detailed design. While the tool provides valuable insight, residents should consult professionals for sitespecific systems that meet building codes and include treatment, overflow, and other technical considerations.
This initiative underscores MTGCD’s mission to protect groundwater resources while supporting the needs of a growing population. By making rainwater harvesting more approachable and highlighting its role in drought resilience, the District hopes to inspire residents across Central Texas to participate in conservation efforts—one roof at a time.
—submitted