Water demand planning and climate change HOW ARE CHANGES IN CUSTOMER WATER DEMANDS AND CLIMATE IMPACTING HOW WE THINK ABOUT FUTURE WATER SUPPLY? Peter Mayer, P.E. Principal Climate Change • • • • • Drought Water shortages Super storms Floods New water supply = time + $$$ Drought @2050 vs. Notorious Recent Historical Droughts PDSI = Palmer Drought Severity Index PDSI was developed by Wayne Palmer in the 1960s and uses temperature and rainfall information in a formula to determine dryness. 2040-2060 Source: Dr. Martin Hoerling, NOAA Earth System Research Laboratory US Drought Monitor Risks of Climate Change for Water Providers Decreased water supply Reduced snowpack Earlier runoff Increased water demand Hotter and drier Higher evapotranspiration rates Increased outdoor demand for irrigation Increased indoor demand for cooling Intense and more frequent drought Variability and uncertainty Potential Water Provider Responses to Climate Change Increase water supply, treatment capacity, and storage Manage Both Nothing water demand Greeley Colorado 100 Years of Water Use City of Greeley Water Production (MGD) 12,000.000 10,000.000 8,000.000 6,000.000 4,000.000 2,000.000 2013 2008 2003 1998 1993 1988 1983 1978 1973 1968 1963 1958 1953 1948 1943 1938 1933 1928 1923 1918 1913 1908 0.000 Climate Conundrum: Uncertainty Risks of developing new supply, capacity, and storage Demand doesn’t materialize Infrastructure over-built Public pays for water and infrastructure that wasn’t needed Risks of managing water demand It doesn’t work and demand increases. It works and revenue declines Water Demand Forecasting Takes on New Importance Understanding likely future demand trends is essential to preparing effectively for climate change. A brief history of demand forecasting in Seattle, WA Per Capita Demand and Drought 180 160 140 Gallons per capita per day 1992 - 2002 avg = 149.9 gpcd 120 2003 - 2014 avg = 131.0 gpcd 100 80 Drought 2002-2004 13% reduction in average system gpcd from 1992 - 2014. 60 40 20 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 12,000 3.50 10,000 3.00 8,000 2.50 6,000 2.00 4,000 1.50 Drought 2002-2004 2,000 1.00 - 0.50 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Net ET (ft) Seasonal Demand (AF) Net ET (ft) Seasonal Demand (AF) Seasonal Demand and Net ET Net ET vs. Seasonal Demand 12,000 Seasonal Impact Seasonal Demand (AF) 10,000 8,000 6,000 y = 294.54x - 341.63 R² = 0.5154 4,000 2,000 15.0 20.0 25.0 30.0 Net ET - Inches 35.0 40.0 Demand Forecasts that Incorporate Climate Change Impacts Example: In Colorado Front Range climatologists predict 4 - 7˚ F average temperature increase, but uncertain changes in precipitation Temperature increase used in ET models for predict future landscape water requirements Demand forecasts that include an explicit outdoor irrigation component incorporate these potential increases Scenario planning for multiple futures (from Colorado’s Water Plan Draft 2014) Multiple Future Demand Scenarios Three population scenarios – low, medium and high growth Two conservation scenarios – passive and active Two climate scenarios – today’s climate and warmer climate 12 demand forecasts Variability of demand must also be incorporated Demand Forecasts Incorporating Climate Change 35,000 30,000 Annual Demand (AF) 25,000 20,000 15,000 Lower limit of forecast water demand variability. 10,000 5,000 - Supply and Demand Modeling Potential impacts of future drought on water supplies Potential impacts of future climate change on water supplies Integration of supply and demand scenarios 12 demand scenarios 2 future drought scenarios 24 combined supply and demand scenarios Demand Forecast Under Climate Change The Path Forward Monitor water supply and demand rigorously If new supply projects are likely, move forward on planning and permitting Identify “sign posts” of additional supply and/or demand management Implement a “No Regrets” Strategy Reduce water demand of existing customers Reduce system water loss Ensure new customers join the system at high efficiency level Anticipate demand reductions Set rates to recover costs even if demand goes down Thank You! Peter Mayer, P.E. Principal peter.mayer@waterdm.com 720-318-4232 www.waterdm.com