Revising Reservoir Planning Based On Vulnerability To Sustained Drought In The Past And Future Charlie Ester, SRP Manager, Water Resource Operations October 2, 2013
Las Vegas SRP manages six reservoirs on the Salt (4) and Verde (2) rivers and one on East Clear Creek in Arizona, and operates approximately 260 groundwater wells, which provide a renewable water supply to the 250,000 acre service area. Mogollon Rim Salt River CAP
SRP Water Service Area 13,000 Sq. Mile Project Watershed Flagstaff Prescott Payson Phoenix River Salt River Peoria Glendale Tolleson Scottsdale Phoenix Mesa Avondale Tempe Gilbert Chandler Tucson
Salt River Project Historic Drought Periods (Average Runoff 1913 2010 = 1,172,215 AF) 100 90 % Average 80 70 60 50 40 Drought of Record 7 s 1898-1904 35% 7 s 1942-1948 62% 5 s 1953-1957 47% 4 s 1974-1977 52% 18 + s 1995 2013???% 30 20 10 0 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
Planning Assumptions Version 1.0 (1980s and 1990s) 950,000 AF -- full demand 325,000 AF -- maximum pumping Historical drought of record : 1898-1904 Use of allocation and pumping to manage for drought of record Demand mainly agricultural
SRP Storage, Pumping & Water Allotment Planning 2000 1800 Median Inflow Minimum Pumping 1600-75 Reservoir Storage (KAF) 1400 1200 1000 800 600 3.0 AF/AC 2.5 AF/AC Drought of Record - 125-200 - 250-325 Ground Water Production (KAF) 400 2.0 AF/AC 200 Maximum Pumping 0 1 2 3 4 5 6 7
Salt River Project Historic Drought Periods (Average Runoff 1913 2010 = 1,172,215 AF) 100 90 Longer Period Of Sustained Drought % Average 80 70 60 50 40 7 s 1898-1904 35% 7 s 1942-1948 62% 5 s 1953-1957 47% 4 s 1974-1977 52% 18 + s 1995 2013???% 30 20 10 0 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
The 11-year period was 1575-1585. 11- Drought With 70% Of Historical Gaged Median Inflow
Time To Rethink Old AssumpGons
2002 and 1996: long-term extreme lows 350 Reconstructed annual flows, SVT 300 2002 baseline Flow (pct of normal) 250 200 150 100 50 1400 1500 1600 1700 1800 1900 2000 Reconstructed flow was 21% of normal* in 2002, 22% of normal in 1996 No other reconstructed flow from 1330 to 2005 was lower than 25% of normal. Tree growth recovered with wetter conditions in 2005 *normal is 1914-2007 mean, water year, Salt+Verde+Tonto Flow (pct of normal) 250 200 150 100 50 0 1950 1960 1970 1980 1990 2000
How Vulnerable Are We? Historical Record Tree Ring Record Climate Change Scenarios Key Question: What is minimum flow that allows SRP to maintain carryover storage in perpetuity?
SRP Storage, Pumping & Water Allotment Planning 2000 1800 1600 Median Inflow - 75 Reservoir Storage (KAF) 1400 1200 1000 800 600-125 - 200-250 - 325 400 200 0 2002 2001 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 40% 45% 50% 55% 60% 63% 64% Median Simulated Reservoir Storage for a Range of Perpetually Reduced Inflows (as a percent of historical median)
How Vulnerable Are We? PERCENT OF MEDIAN INFLOW YEARS TO RESERVOIR DRYUP 64 INDEFINITE 63 50+ 60 19.5 55 9.3 50 7.3 48 6.4 45 5.4 40 4.4
Climate Change Roosevelt Lake and Dam, AZ The Story in the Southwest Climate Model Results
42-Model Run Average and 10% and 90% Range of Individual Simulations From Martin Hoerling, NOAA, and Jon Eischeid, U of CO, Past Peak Water in the Southwest, Southwest Hydrology, Jan/Feb 2007. Results of Intergovernmental Panel on Climate Change Fourth Assessment Report, 2007.
Projections of Future Changes in Climate Precipitation increases very likely in high latitudes Decreases likely in most subtropical land regions
What We Do Know: Climate Change? Bottom Line for The Southwest Continued warming could result in: Twenty (20) to fifty (50) percent decrease in runoff over the next several decades Which would require: Search for additional water supplies for same level of service; and, Some idea of the how much time we have to plan for those resources to be available (lead time)
In a climate changing world the question becomes: How much worse (drying) before previous droughts become a problem? Severe Droughts Capable of Depleting Surface Water Supply With The Noted Reduction In Flow Period Source Duration (yrs) Flow Reduction Average Annual % of Median 1214-1217 Tree-ring 4 20% 40% 1579-1585 Tree-ring 7 15% 50% 1666-1670 Tree-ring 5 20% 45% 1817-1823 Tree-ring 6 20% 48% 1898-1904 Historical 7 20% 48% 1999-2002 Historical 4 20% 40%
SRP Storage, Pumping & Water Allotment Planning 2000.0 1800.0 1600.0 Median Inflow Groundwater Pumping (KAF) - 75 Reservoir Storage (KAF) 1400.0 1200.0 1000.0 800.0 600.0-125 - 175-250 - 325 2.0 AF/AC 400.0 63% Median 200.0 0.0 1 2 3 4 5 6 7 8 9 10
SRP Storage, Pumping & Water Allotment Planning 2000.0 1800.0 1600.0 Median Inflow Groundwater Pumping (KAF) - 75 Reservoir Storage (KAF) 1400.0 1200.0 1000.0 800.0 600.0-125 - 175-250 - 325 2.0 AF/AC 400.0 63% Median 200.0 0.0 1 2 3 4 5 6 7 8 9 10
SRP Storage, Pumping & Water Allotment Planning 2000.0 1800.0 1600.0 Median Inflow Groundwater Pumping (KAF) - 75 Reservoir Storage (KAF) 1400.0 1200.0 1000.0 800.0 600.0-125 - 175-250 - 325 2.0 AF/AC 400.0 63% Median 200.0 0.0 1 2 3 4 5 6 7 8 9 10
SRP Storage, Pumping & Water Allotment Planning 2000.0 1800.0 1600.0 Median Inflow Groundwate Pumping (KAF) - 75 Reservoir Storage (KAF) 1400.0 1200.0 1000.0 800.0 600.0-125 - 175-250 - 325 2.0 AF/AC 400.0 63% Median 200.0 0.0 1 2 3 4 5 6 7 8 9 10
SRP Storage, Pumping & Water Allotment Planning 2000.0 1800.0 1600.0 Median Inflow Groundwate Pumping (KAF) - 75 Reservoir Storage (KAF) 1400.0 1200.0 1000.0 800.0 600.0-125 - 175-250 - 325 2.0 AF/AC 400.0 63% Median 200.0 0.0 1 2 3 4 5 6 7 8 9 10
SRP Storage, Pumping & Water Allotment Planning 2000.0 1800.0 1600.0 Median Inflow Groundwate Pumping (KAF) - 75 Reservoir Storage (KAF) 1400.0 1200.0 1000.0 800.0 600.0-125 - 175-250 - 325 2.0 AF/AC 400.0 63% Median 200.0 0.0 1 2 3 4 5 6 7 8 9 10
When Storage Drops Below The Target 63% Line: Activate Augmentation Efforts to Raise Storage Back to the 63% Line Menu Of Options: Increase Groundwater Pumping (Restoration Program) Reduce Allocation Of Water Purchase Central Arizona Project Water Exercise Lease Options Indian And Non-Indian Agriculture Recover Long Term Underground Storage Credits Conservation Efforts Watershed Management/Weather Modification Activities
Water Necessary to Recover to the Target 63% Line Historical Drought Recovery Water (KAF) Reduction 1 2 3 4 5 6 7 8 9 10 11 Total 1212-1218 20% 132 114 298 544 1576-1586 15% 169 143 285 316 913 1665-1671 20% 29 190 40 256 515 1817-1824 20% 337 140 261 19 112 869 1895-2005 20% 298 180 38 516 1998-2004 20% 19 242 283 544
Water Resources Planning Will Change
Proposed Methodology: Process To Determine Timing and Volume of Additional Supplies No, ConGnue Current OperaGng Plan IdenGfy Sustainable Storage Target, Demand, and Total Reservoir Storage Is Risk of GeVng Below Sustainable Storage 1% or Greater? Yes, Determine Volume and Source of Supplemental Supply Needed to Achieve Desired Reliability
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