Guideline for Developing Drinking Water Capacity Analysis Report Using Time Series Linear Model to Predict Future Demand

A capacity analysis report (CAR) is an essential document that assists public water system owners in prioritizing water infrastructure and resources for future capital improvements. The United States Environmental Protection Agency states that public water systems should develop a CAR when average daily production approaches or exceeds a certain percentage of the system design capacity. Different states have different CAR requirements; this report is a guide for developing a CAR for drinking water facilities based on State of Florida requirements. This document will also demonstrate how to use a water demand time series predictive model to forecast future demand. An illustration of how to develop two models is provided. Both models use time as the predictor/independent variable and water demand/consumption as the dependent variable. The first model uses full data to determine the linear regression equation, while the second model uses partitioned data to develop the linear regression equation. The model with the lowest Mean Absolute Error (MAE) is selected for future demand predictions. City of Fort Myers Water Treatment Plant data was used to demonstrate how to develop a CAR and demand forecasting models.