This step looks into the future to identify changing (presumably increasing) water demand related to expanding customer needs – because of a growing residential population or because of expanding industrial and commercial demands, or both. During Planning Step 3, the future demands will be compared to the baseline conditions established in Planning Step 1 to identify gaps in future water supply needs and estimate costs of developing new water supplies, building infrastructure and operating and maintaining the future water supply system.
This guidance document recommends that planners prepare forecasts for five-year, ten-year, and twenty-year intervals. Additional time points can be included as well. The longer the planning horizon, the greater the uncertainty of the forecast. Forecasts should be revisited and updated on a regular basis.