Climatic Variability and Water Supply Planning in Tampa Bay
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Tampa Bay Water is a drinking water utility servicing over two million residents in Hillsborough County, Pasco County, Pinellas County, New Port Richey, St. Petersburg, and Tampa. The utility is working to assess how climate change will affect local hydrology and water supply, provide forecasting tools to inform decision making, and diversify water supply sources in the region.
Tampa Bay Water is one of the eleven members of the Water Utility Climate Alliance, a collaborative focused on advancing climate resilience in water utilities throughout the United States. The utility has been working to assess how climate variability will affect local water supply, especially with respect to seasonal forecasting and periodic droughts. Historically, the region relied exclusively on groundwater pumping for its supply; however, saltwater intrusion and overpumping in the 1980s triggered a shift to 60% surface water supply from local rivers and the bay itself. However, the 1999-2001 drought required the utility to again pump groundwater to match consumer demand; the extent of this extraction had major impacts on the surrounding natural environment. The region is experiencing increasingly higher seasonal climatic variability, which may drive even more frequent droughts; at the same time, water demand will increase as the regional population grows. Tampa Bay Water believes its system is robust for another 15-20 years, but knows it needs to start planning for future demands. For example, the utility currently supplies approximately 240 million gallons per day (mgd) on average to over 2.4 million residents; projections indicate that with an increasing population, demand will increase to 275 mgd by 2035.
Tampa Bay Water is engaged in a number of efforts to provide resilient drinking water supplies, primarily (1) using forecasting tools to inform decision making, (2) conducting an assessment of the effects of climatic variability local hydrology, and (3) diversifying water supply sources in the region.
1. Forecasting Using the Climate Outlooks
from NOAA’s Climate Prediction Center, the utility tracked patterns in the El Niño Southern Oscillation (ENSO) to forecast wet and dry conditions in the region. These outlooks are useful to local water managers to identify near, short-term changes in surface water availability, and make strategic decisions on groundwater withdrawals to meet immediate consumer demands.
2. Climatic variability and water supply
Recognizing the need to forecast water supplies more reliably and over a longer timeframe, Tampa Bay Water partnered on a project to assess climate impacts on the area’s water supply and the utility’s ability to meet an anticipated increase in demand. The objectives are to evaluate the ability of dynamical and statistical downscaled Global Climate Models (GCM) to reproduce observed regional temperature and rainfall patterns; reproduce historic hydrologic behavior; evaluate projected changes in hydrology associated with future projections of temperature and rainfall; and assess the effects of climate projections on future water supply availability in the region. Initial results demonstrate high variability in projected precipitation patterns, which indicates a need for more refined regional and local hydrologic-climate models.
3. Diversified water supply sources
The utility constructed a $158-million desalination plant to protect groundwater sources from saltwater intrusion, as well as a $140-million, 15-billion-gallon reservoir that stores water from the Alafia River, Hillsborough River, and Tampa Bypass Canal.
These measures provide back up water supply during periods of drought, including during the recent April 2017 drought.
Outcomes and Conclusions
Tampa Bay Water is also collaborating with the Florida Water and Climate Alliance on projects to evaluate the effects of sea level rise on groundwater well and surface water quality, and the impacts of temperature changes on potable water delivery and operation and maintenance of water resources infrastructure.
Gregg, R.M., & Score, A. (2017). Climatic Variability and Water Supply Planning in Tampa Bay [Case study on a project of Tampa Bay Water]. Product of EcoAdapt's State of Adaptation Program. Retrieved from CAKE: http://www.cakex.org/case-studies/climatic-variability-and-water-supply-... (Last updated December 2017)
Chief Technical Officer (former)