Why a new groundwater model? Developing a new model for sacramento valley Annual DWR Geology & Groundwater Meeting December 3, 2014 Linda D. Bond, P.G. Integrated Regional Water Management Regional Planning Branch

Source:USGS IT IS IMPOSSIBLE TO USE A NATURAL RESOURCE WITHOUT IMPACTING IT Resources are finite Regional, long-term impacts of pumping often take decades to be detected Management will come early by choice or later out of necessity The best we can do is – understand the impacts – minimize the impacts we can – manage the impacts we can’t minimize 12/4/2014 Geology Matters2

OUTLINE  OVERVIEW OF GROUNDWATER-SURFACE WATER INTERACTIONS  WHY A NEW MODEL?  KEY FEATURES OF THE NEW MODEL 312/4/2014 Geology Matters

FACTORS CONTROLLING STREAM DEPLETION CAUSED BY GROUNDWATER PUMPING  Hydraulic Connectivity  Well Location  Aquifer Parameters: Transmissivity and Storativity  Streambed Conditions 2014 RPB Understanding GW SW Connection 4

HYDRAULIC CONNECTIVITY BETWEEN GROUNDWATER SYSTEM AND STREAMS AQUIFER AND STREAM DISCONNECTED AQUIFER AND STREAM CONNECTED SACRAMENTO VALLEY RPB Understanding GW SW Connection SAN JOAQUIN VALLEY

WHY DOES GROUNDWATER PUMPING IMPACT STREAMFLOW? Barlow and Leake 2012 Circular RPB Understanding GW SW Connection

HYDRODYNAMICS OF GW-SW SYSTEMS Storage Depletion To Streamflow Depletion Barlow and Leake 2012 Circular RPB Understanding GW SW Connection

DELAYED IMPACT – SEASONAL PUMPING 12/4/2014 Geology Matters8 Time Delay To Full Capture of Streamflow Extends Over Decades Bredehoeft and Kendy 2008

DELAYED IMPACT – SINGLE EVENT RPB Understanding GW SW Connection <- instantaneous <- cumulative Pumping Today Causes Stream Depletion That Extends Over Decades

GEOLOGY MATTERS AQUIFER PARAMETERS (Diffusivity = Transmissivity/Storativity) AND LOCATION OF CLAYS AND SANDS AFFECT RATE OF IMPACT Common Misconception – Deep Wells Don’t Impact Streams 10

WHY A NEW MODEL?  Numerous existing models of Sacramento Valley  All are “well calibrated” HOWEVER  Each represents the groundwater basin differently  Conceptual Model - Aquifer Parameters  Layers and Grid (model discretization)  All produce different stream depletion results 12/4/2014 Geology Matters11

EXISTING MODELS 12/4/2014 Geology Matters12 Notes: Approximate Values Model A – Uniform values from water table to base of groundwater system; no vertical variability

DO THESE DIFFERENCES MATTER? 12/4/2014 Geology Matters13

TESTING SHOWS STORATIVITY MATTERS 12/4/2014 Geology Matters14 Reeves 2008 STRMDEPL08 - Glover Solution 1954

TESTING SHOWS HYDRAULIC CONDUCTIVITY MATTERS 12/4/2014 Geology Matters15 Reeves 2008 STRMDEPL08 - Glover Solution 1954

TESTING SHOWS - MODEL ELEMENT SIZE MATTERS 12/4/2014 Geology Matters16 HYDROGRAPHS OF STREAMFLOW DEPLETION GRID SIZE 1000 ft X 700 ftGRID SIZE 500 ft X 80 ft GRID SIZE 12.5 ft X 25 ft GRID SIZE 250 ft X 25 ft

KEY FEATURES OF NEW MODEL  First Step: Sound Conceptual Model  Identify Distinct Hydrogeologic Structure and Units  Previous Studies (Geology of Northern Sacramento Valley – NRO DWR)  Mapping of Near-Surface Units (Helley and Harwood 1985 )  5000 Well Logs (DWR IRWM and Flood Division + USGS logs for Texture Analysis)  Second Step: Conduct Tests to Determine Model Grid Sizing That Can Produce Stable Stream Depletion Results 12/4/2014 Geology Matters17

12/4/2014 Geology Matters18

GEOLOGIC MAP SACRAMENTO VALLEY GROUNDWATER BASIN Key Interface Between Groundwater and Surface Water Systems 12/4/2014 Geology Matters19

REGIONAL AQUIFER SYSTEMS CREATE AN ILLUSION OF LIMITLESS SUPPLY PUMPING IMPACTS CAN TAKE DECADES TO BE DETECTED GROUNDWATER AND SURFACE WATER ARE REGULATED SEPARATELY BASINS ARE GOVERNED LOCALLY TO MANAGE WATER SUSTAINABLELY WILL REQUIRE CHANGE IN WHAT WE UNDERSTAND ABOUT GROUNDWATER AND HOW WE DEAL WITH THOSE FACTS 12/4/2014 Geology Matters20

Useful References  Barlow and Leake, 2012, Streamflow Depletion by Wells—Understanding and Managing the Effects of Groundwater Pumping on Streamflow, USGS, Circular 1376  Bredehoeft, J.D., and Kendy, Eloise, 2008, Strategies for offsetting seasonal impacts of pumping on a nearby stream: Ground Water, v. 46, no. 1, p  Bredehoeft, J., and Durbin, T., 2009, Ground water development—The time to full capture problem: Ground Water, v. 47, no. 4, p. 506–514.  Glover, R.E., and Balmer, G.G., 1954, River depletion resulting from pumping a well near a river: Transactions of the American Geophysical Union, v. 35, no. 3, p. 468– 470.  Leake, S.E., 2011, Capture—Rates and Directions of Groundwater Flow Don't Matter! Ground Water Volume 49, Issue 4, pages 456–458, July/August 2011  Theis, C.V., 1940, The Source of Water Derived from Wells Essential Factors Controlling the Response of an Aquifer to Development: Civil Engineering, v. 10, no. 5, p. 277–280.  Theis, C.V., 1941, The effect of a well on the flow of a nearby stream: Transactions of the American Geophysical Union, v. 22, no. 3, p. 734– /4/2014 Geology Matters

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Regional Aquifer Systems Create the Illusion of Limitless Supply Pumping Impacts Can Take Decades To Be Detected Stream Flow Depletion: Sacramento Valley Subsidence: San Joaquin Valley Salt Water Intrusion: Coastal Aquifers Challenge - Buy Now, Pay Later: Economies based on today’s groundwater use that result in future impacts are difficult to change 12/4/2014 Geology Matters23

CHALLENGE  GROUNDWATER AND SURFACE WATER ARE ONE INSEPERABLE, BASINWIDE- INTERCONNECTED RESOURCE  GROUNDWATER AND SURFACE WATER ARE REGULATED SEPARATELY  BASINS ARE GOVERNED LOCALLY  TO MANAGE WATER SUSTAINABLELY WILL REQUIRE A CHANGE IN WHAT WE UNDERSTAND ABOUT WATER AND HOW WE WORK TOGETHER 12/4/2014 Geology Matters24

12/4/2014 Geology Matters25

GROUNDWATER AND SURFACE WATER FUNCTION PHYSICALLY AS ONE BASINWIDE- INTERCONNECTED RESOURCE WATER RESOURCES CAN’T BE UNDERSTOOD WITH A PIECEMEAL “LOCAL WATER BUDGET” APPROACH Theis RPB Understanding GW SW Connection EACH PART AFFECTS THE WHOLE

12/1/201512/4/2014 Geology Matters

WHAT DOES STREAM DEPLETION LOOK LIKE? WHEN DOES IT MATTER? 2812/4/2014 Geology Matters

PREVIOUS WORK “All water discharged by wells is balanced by a loss of water somewhere.”  Theis, 1940  Glover and Balmer, 1954  Bredehoeft, Leake, and others – 1980’S to present  Barlow and Leake, 2012 Theis 2912/4/2014 Geology Matters

SACRAMENTO VALLEY - HISTORICAL SIMULATION AGRICULTURAL AND URBAN PUMPING (MAF/YR) C2VSIM Draft Report Nov /4/2014 Geology Matters

SACRAMENTO VALLEY - HISTORICAL SIMULATION NET GROUNDWATER DISCHARGE TO RIVERS (MAF/YR) C2VSIM Final Report June /4/2014 Geology Matters

AQUIFER PARAMETERS Source: July 2012 Draft Conaway Ranch-Environmental Assessment, Appendix C, Figure 7.  Parameter values in models represent “net” aquifer conditions  Team: Are parameter values reasonable representation of regional conditions?  Team: Can we generate figures showing distribution of aquifer parameters for each layer of model 3212/4/2014 Geology Matters

WELL LOCATION 3312/4/2014 Geology Matters

AQUIFER PARAMETERS: T(K*b)/S Rate of Impact for Confined Wells > Unconfined wells Because T(K*b)/S >> T(K*b)/Sy STREAM AND AQUIFER CONNECTED 3412/4/2014 Geology Matters

EXISTING MODELS 12/4/2014 Geology Matters35 Notes: Approximate Values Model A – Uniform values from water table to base of groundwater system; no vertical variability