Exploring the Possibilities At Prado Dam Greg Woodside, P.G., C.HG. Executive Director of Planning & Natural Resources December 5, 2017
The Orange County groundwater basin lies at the base of the Santa Ana River watershed
OCWD overlies the groundwater basin in the northern half of Orange County Basin provides 75% of water supply for 2.4 million people
The basin is comprised of three major aquifer systems that are hydraulically interconnected
Starting about 11 miles downstream, OCWD recharges Santa Ana River water captured at Prado Dam
The deep basins are able to recharge up to 100,000 acre-feet per year
Prior to the early 1990s, a large sand dike had to be constructed to divert water from the SAR
In 1992, the Imperial Rubber Dam was installed at a cost of $3M Increased capture of storm water paid for the cost of the dam and control structure in the first year of operation
The USACE constructed Prado Dam in 1941 for flood risk management and water conservation
Army Corps of Engineers & OCWD have longstanding Partnership in Prado Basin Ecosystem restoration Temporary stormwater capture in buffer pool (aka water conservation ) Stormwater capture does not affect flood risk management
Summary of Prado Water Conservation through Time Year 1969 revision to reservoir regulation schedule 1990 update to water control manual Flood Season 490 ft 494 ft Non-Flood Season 1993 MOA 494 ft 505 ft 2006 MOA 498 ft 505 ft
OCWD and the USACE cooperate to store and capture up to 20,000 af of storm water at a time The ACOE coordinates the release rate with OCWD to match the capacity of the recharge system.
1949 1953 1957 1961 1965 1969 1973 1977 1981 1985 1989 1993 1997 2001 2005 2009 2013 2017 Annual Recharge (afy) Investments in infrastructure and water conservation at Prado Dam have paid off 140,000 Surface Water Recharge 120,000 100,000 Storm Flow Recharge 80,000 60,000 40,000 20,000 0
Water Level Elevation (ft msl) Water Levels Behind Prado Dam 1996-2017 550 540 Spill Elevation 542 ft msl Storage (af) 174K 530 520 Spring Water Conservation Level 100K 510 500 490 20K 10K 2.5K 480 200 470 460 450 January-69 January-79 January-89 January-99 January-09
Monthly Rainfall (inches) An all-time record of 10.5 inches was recorded in Anaheim in December 2010 12 10 8 8 inches in 6 days Monthly Rainfall Historic Average Rainfall 6 4 2 0 JULY AUG SEPT OCT NOV DEC JAN FEB MAR APR MAY JUNE
False-Color Satellite Image of the Atmospheric River 18th December 2010
The shape of the watershed margins has a significant impact on AR s FMCW Radar NEXRAD Radar Forest Cannon and F. Martin Ralph, Scripps
Jul-10 Aug-10 Sep-10 Oct-10 Nov-10 Dec-10 Jan-11 Feb-11 Mar-11 Apr-11 May-11 Jun-11 Conservation Pool Storage (af) Over 130,000 acre-feet of water was released to the ocean due to December 2010 storm 100,000 90,000 80,000 70,000 60,000 50,000 40,000 30,000 20,000 Max. Conservation Pool Storage (af) 10,000 0 Month
Preliminary, Cannon, Ralph, Scripps. Atmospheric Rivers hit the Santa Ana River watershed in January and February 2017 L L 23-Jan 18-Feb Preliminary, Cannon, Ralph, Scripps.
Inches February 17-18, 2017 AR Storm 3.5 3.0 2.5 Precipitation (in) 2.0 1.5 1.0 0.5 0.0 1-Feb 6-Feb 11-Feb 16-Feb 21-Feb 26-Feb 900 af unused storage 8,000 506 7,000 502 Flow (cfs) 6,000 5,000 4,000 3,000 Inflow (cfs) Outflow (cfs) Water Surface Elevation 6,500 af of storage created 498 494 490 Water Surface Elevation (ft msl) 486 2,000 482 1,000 478 0 1-Feb 6-Feb 11-Feb 16-Feb 21-Feb 26-Feb 474
There is wide variability in the AR tracks affecting the Santa Ana River watershed Preliminary schematic of the low pressure centers and moisture transport during 107 extreme events that accounted for ~50% of 1981-2017 precipitation in the Santa Ana River Watershed. Preliminary, Cannon, Ralph, Scripps.
Forecast-Informed Reservoir Operations (FIRO) Using enhanced weather forecasting and runoff estimation tools to inform future reservoir operations Includes growing understanding of atmospheric river (AR) storms Pilot study underway for Lake Mendocino led by Dr. Martin Ralph/Scripps, Army Corps, and Sonoma County Water Agency OCWD initiating similar pilot study.
Improved forecasting will have multiple benefits Reservoir Operations Greater insight to future storms and stormwater inflow rates Water Supply Reduced losses to ocean Efficient use of water conservation pool Decreased need for imported water
Thank You! Photo courtesy of Chris Jones, USACE (1-17-2017)