Friant Dam and Millerton Reservoir

Transcription

1 San Joaquin River Restoration Program Floodplain Management Association Presentation SJRRP Update Continued: Impacts from Subsidence April 18, Friant Dam and Millerton Reservoir Completed in 1942 Authorized for: Water Supply Flood Control 520,500 Acre-feet Storage Capacity 1.8 Million Acre-feet Average Inflow 1.4 Million Acre-feet Average Deliveries No Carryover Storage Controlled Releases: San Joaquin River (8,000 cubic feet per second (cfs)) Friant-Kern Canal (5,300 cfs) Madera Canal (1,250 cfs) 2 Subject to Revision; For Discussion Only 1

2 Water Service & Holding Contracts Friant Division of the CVP 29 long-term Friant Division water service contracts Class 1 Water 800,000 acre-feet Class 2 Water 1,400,000 acre-feet Holding Contracts San Joaquin River downstream of Friant 5 cfs required past diversions Last diverter is at Gravelly Ford 3 CVP Friant Division Subject to Revision; For Discussion Only 2

3 Study Area Newman 153 miles of the San Joaquin River Friant Dam to the Merced River Confluence Challenges: - Most sections of river dry for many years - Agricultural encroachment into the channel - Existing levee challenges Los Banos Firebaugh Fresno Restoration Area Subsidence In 2010 the FloodSafe Program identified anomalies in survey controls attributable to subsidence USBR established a control network in 2011 and monitored subsidence throughout 2012 Preliminary measurements show subsidence rates greater than 0.5 ft/year, with two centers Site-specific projects include design criteria to account for a 25-year project life 6 Subject to Revision; For Discussion Only 3

4 Historic Subsidence (pre-2000) Subsidence has been a known issue in the Central Valley since the early 1900 s. Until approximately 1980, limited technology existed that could accurately map subsidence. Original studies, including surveys and mapping efforts, were conducted by: United States Army Corps of Engineers (USACE) United States Bureau of Reclamation (USBR) California Department of Water Resources (DWR) United States Geological Survey (USGS) Other interested parties Landowners, water districts, contracted A&E firms, etc. 7 Approximate location of maximum subsidence in the United States identified by research efforts of Dr. Joseph F. Poland (pictured). Signs on pole show approximate elevation of land surface in 1925, 1955, and (28 feet in 50 years,.56 feet/year) The site is in the San Joaquin Valley southwest of Mendota, California. Subject to Revision; For Discussion Only 4

5 Study Area Newman Los Banos Firebaugh Fresno Historic Subsidence (pre-2000) Estimated subsidence rates ( ), USACE 10 Subject to Revision; For Discussion Only 5

6 Projected Subsidence Rates, USACE Map 11 Early SJRRP Studies ( ) After the creation of the SJRRP, a series of early level studies and surveys were conducted. These studies utilized the latest technologies, including LiDAR, GPS, and traditional surveying methods. Original studies, including surveys and mapping efforts, were conducted by: USACE USBR California Department of Water Resources (DWR) United States Geological Survey (USGS) Other interested parties Landowners, water districts, contracted A&E firms, etc. 12 Subject to Revision; For Discussion Only 6

7 Early SJRRP Studies ( ) USGS Interferogram Data ( ) 13 Early SJRRP Studies ( ) RBF subsidence survey ( ), with DWR 14 Subject to Revision; For Discussion Only 7

8 SJRRP Studies & Data Sets To gather more data on the subsidence area, the SJRRP office and implementing agencies conducted design-level surveys between 2010 and the present. These studies utilize LiDAR, InSAR/IfSAR, GPS, photogrammetry, and traditional surveying methods. Surveys & mapping efforts were/are being conducted by: USACE USBR California Department of Water Resources (DWR) United States Geological Survey (USGS) Other interested parties Landowners, water districts, contracted A&E firms, etc. 15 SJRRP Studies 16 Subject to Revision; For Discussion Only 8

9 SJRRP Studies Combined RBF & USBR survey (2010) 17 NGS survey (2011), by USBR SJRRP Studies 18 Subject to Revision; For Discussion Only 9

10 SJRRP Studies NGS Survey ( ), by USBR 19 SJRRP Reach Specific Maps To support specific design projects (Reach 2B, Sack Dam & Arroyo Canal Reach 3, and Reach 4B1) a reach-specific series of subsidence maps were created These maps focus on the individual reach will allow the Design Team to determine relatively accurate subsidence design rates 20 Subject to Revision; For Discussion Only 10

11 Study Area Newman Los Banos Firebaugh Fresno SJRRP Reach 2B Maps 22 Subject to Revision; For Discussion Only 11

12 SJRRP Reach 2B Maps 23 Study Area Newman Los Banos Firebaugh Fresno Subject to Revision; For Discussion Only 12

13 SJRRP Reach 3 Maps 25 SJRRP Reach 3 Maps 26 Subject to Revision; For Discussion Only 13

14 SJRRP Reach 3 Maps 27 Study Area Newman Los Banos Firebaugh Fresno Subject to Revision; For Discussion Only 14

15 SJRRP Reach 4B1 Maps 29 SJRRP Reach 4B1 Maps 30 Subject to Revision; For Discussion Only 15

16 Data Analysis Factors A number of factors affect the survey data and how that data may be analyzed and incorporated into the subsidence projections for the SJRRP. These factors include: Varying confidence intervals Varying accuracy levels Mixed technologies used to collect this data Developing and confirming accurate benchmarks used to georeference the collected data Coordinating different data collection periods and timeframes Referencing the current data back to historic or previously collected data sets for comparing and confirming observed/measured subsidence 31 Planned Future Data Collection Data collection is expected to continue, as needed to support SJRRP projects. Currently planned data collection includes: Bi-annual USBR survey of NGS stations and other select benchmarks CH2MHill project site surveys (Reach 3) Henry Miller Reclamation District surveying along Arroyo & TSR Canals Central CA Irrigation District surveying along Delta-Mendota, Helm, and Poso Canals USGS InSAR/IfSAR surveying when possible (SJR Region) NGS data collection when available (static GPS base station network) Other sources when available These and all other available sources will be incorporated into the project when possible to refine the accuracy of the subsidence maps. 32 Subject to Revision; For Discussion Only 16

17 Impacts of Subsidence The effects of subsidence on this project include: Sedimentation Concerns: Sediment scour and head-cutting in reaches upstream of the subsidence Sediment deposition in reaches downstream of the subsidence Habitat Concerns: Migration of habitat materials (sediments, vegetation, floating debris/large woody debris, etc.) Migrated material is not immediately available as new habitat, so in-river and bank-side habitat is temporarily unavailable Loss of habitat complexity (disconnected floodplains upstream and inundated floodplains downstream) Structural Concerns: Increased flow velocities due to vegetation/sediment erosion; local scour around structures (i.e. bridge piers, abutments, control gates, etc.) Loss of conveyance capacities due to deposition Potential increased water depth in and downstream of subsidence pool Longer or permanent periods of inundation for submerged structures (bridge bearing pads, gate seals, stoplog seals, etc.) 33 Impacts of Subsidence (cont d) Structural Concerns continued: New structures must be designed to include the anticipated subsidence height, causing the structure to be larger, and therefore, more expensive Increased Operation & Maintenance costs for structures due to size increase, higher water velocities, and potential inundation Structures must be designed to pass or withstand additional sediment loadings caused by subsidence and flow changes Structures must be designed to operate over a large range, due to the changing elevations caused by subsidence Existing structures and other infrastructure connected to the project may become deficient due to subsidence effects, resulting in additional costs to restore Biological Concerns: Potential for increased predation Variations in flows and velocities may inadvertently cause changes in the temperature and quality of the water for the project 34 Subject to Revision; For Discussion Only 17

18 Affects on other projects The SJRRP includes additional projects beyond the San Joaquin River. These include the Friant-Kern Canal (FKC) and Madera Canal (MC) Capacity Restoration Projects, as well as other Water Management Goal-related projects. The subsidence shown to affect the San Joaquin River also has an impact on these additional projects, which is briefly explained below: 35 Other projects: FKC & MC Friant-Kern Canal (FKC) Subsidence has caused dead pools These are subsided reaches of the canal that cannot be drained via gravity These reaches must be pumped to dewater the canal Additionally, these reaches affect the hydraulic properties of the canal, and its ability to convey water, as originally designed Due to the capacity restrictions caused by subsidence, some flows/flood flows that cannot be conveyed in the SJR system must be routed down the FKC Increases the flows in the FKC, which reduces freeboard typically available for storm run-off or other inflows Additional flows must be delivered into the canal network and routed through the Central Valley safely, even during flood events Madera Canal (MC) Due to the capacity restrictions caused by subsidence, some flows/flood flows that cannot be conveyed in the SJR system must be routed down the MC Increases the flows in the MC, which reduces freeboard typically available for storm run-off or other inflows Additional flows must be delivered into the canal network and routed through the Central Valley safely, even during flood events 36 Subject to Revision; For Discussion Only 18

19 Efforts to End or Reduce Subsidence The Exchange Contractors and local landowners are cooperating to create a Subsidence Project Plan. This plan: Reduce deep well pumping (below Corcoran clay Increase yield of the shallow zone (above Corcoran clay) Build conveyance infrastructure Take advantage of flood flows in the Eastside Bypass (every 3-4 years) Neighbors to purchase annual supplies of surface water to supplement the yield from shallow aquifer 37 The hatched areas represent locations identified in the Merced and Madera County Subsidence Study as areas apparently suitable for recharge Efforts to End or Reduce Subsidence 38 Subject to Revision; For Discussion Only 19

20 Efforts to End or Reduce Subsidence Funding for Madera Water Supply Enhancement Project (Madera Water Bank) Existing Cooperative Agreement between the United States and Madera Irrigation District allows for up to $22.5 M from the USBR. Exchange Contractors in discussions with USBR to allow modify the existing agreement $7 million needed for project to start operations Help in coordinating flood releases from Friant through flood channels with reduced capacity. 39 Efforts to End or Reduce Subsidence Western Madera County Subsidence Area Base-map with Recharge Ponds and Conveyance Facilities 40 Subject to Revision; For Discussion Only 20

21 Reference Documents Comprehensive Study Information Paper: Subsidence in the Central Valley, U.S. Army Corps of Engineers, December Ground Water in the Central Valley, California A Summary Report, USGS Professional Paper 1401-A, pp.44, Land Subsidence due to ground-water withdrawal in the Los Banos-Kettleman City area, California; Part 1, Changed in the hydrologic environment conducive to subsidence, USGS Survey Report P 0437-E, pp.71, Lower San Joaquin River Flood Control Project, Subsidence Investigation, California Dept. of Water Resources, Office Report Volume 11 of 11, Preliminary Investigation of Land Subsidence in the Sacramento Valley, California, USGS Survey Open-File Report, pp.32, Ground-water Flow in the Central Valley, California, USGS, Survey Open-File Report , pp.203, Subsidence Survey of the Outside Canal and Delta-Mendota Canal, Stoddard & Associates, July San Joaquin River Restoration Program Subsidence Design Memo, USBR Technical Service Center, Merced and Madera County Subsidence Study Presentation, San Joaquin River Exchange Contractors 41 Michael Mitchener, CFM, PMP SJRRP Deputy Program Manager mmitchener@usbr.gov Subject to Revision; For Discussion Only 21