Forecasting the Long Term Demand of Water
Future Water, | | Return

Supply and demand. It’s a basic economic principle that determines the price of a good or service. For Tampa Bay Water, that service is the delivery of wholesale drinking water to its member governments. The amount (supply) of that water depends on how much water (demand) each of these member governments needs.

The relationship between demand and supply underlies the forces behind the allocation of resources. In Tampa Bay Water’s case, we must know what the demand for water will be in the future so that we can ensure the supply will be there to meet that demand.

At a recent Tampa Bay Water Board meeting, staff gave a report that forecasted the long-term demand of its six member governments. This forecast model is evaluated and verified each year based on updated socio-economic projections.

The total regional demand projected for Water Year 2015 is 232.5 mgd (millions of gallon per day.) This is about 1.7 mgd lower than last year’s 2015 demand projection. The regional demand prediction for Water Year 2014 of 227.2 mgd is consistent and nearly identical to the Water Year 2014 actual demand of 226.8 mgd. The slightly lower demand forecast for Water Year 2015 is a result of less growth in single-family demand than was predicted.

Other factors that affected the long-term forecast included:

  • Increases in multi-family housing units and employment outweighing the effects of slow income growth and increasing water pricing. This results in long-term growth in regional water demands.
  • Model results for Hillsborough County and City of Tampa water demand planning areas show increases in projected water demands for the 2020 to 2035 time horizon.
  • Both Pinellas and St. Petersburg demands decline. Declines in Pinellas County water demands are primarily due to a loss of wholesale water customers.
  • The highest growth rates are projected to occur in the City of Tampa and Hillsborough County water service areas.
  • Housing unit growth rates for Pinellas County and the City of St. Petersburg are projected to remain flat.
  • Water use in the single-family sector has dropped from 229 gallons per account per day in 2007 to 189 gallons per account per day in 2013. This is an indication that water use efficiency is increasing.

Tampa Bay Water uses the results of these long-term forecast models for two primary purposes:

  • Annual budgeting and source allocation — near-term projections up to five years.
  • Long-range water supply planning — forecasting demands for at least a 10 to 20-year time horizon.