Representing Groundwater Management in California’s Central Valley: CALVIN and C2VSIM By PRUDENTIA GUGULETHU ZIKALALA B.E. (City University of New York-City College) 2006 THESIS Submitted in partial satisfaction of the requirements for the degree of MASTER OF SCIENCE in Civil Engineering in the OFFICE OF GRADUATE STUDIES of the UNIVERSITY OF CALIFORNIA DAVIS Approved: ______________________________________________________ Jay Lund ______________________________________________________ Timothy Ginn _______________________________________________________ Graham Fogg _______________________________________________________ Charles Brush Committee in Charge 2013 i Abstract Updates were made to CALVIN, a hydro-economic optimization model of California’s intertied water delivery system, to improve groundwater representation in the Central Valley. Revisions are based on the Department of Water Resources C2VSIM numerical groundwater model. Additionally, updates are made on the constraints of Delta Exports from major pumping plants as well as constraints on the required Delta Outflows based on current CALSIM II model. The updated CALVIN model is used to examine economical pumping and surface water deliveries with two overdraft management scenarios for 2050 projected land use. Finally a C2VSIM simulation with optimized CALVIN water allocations – surface diversions and pumping – is used to study the Central Valley aquifer responses with these management cases as well as the role of pumping and artificial recharge in the conjunctive use of water for reliable supplies. Although improvements in CALVIN and Central Valley groundwater modeling are considerable, in some regions CALVIN, C2VSIM and CVHM differ substantially. ii Dedication For Dr. Megan Wiley-Rivera, who introduced me to science research and whose generosity and love of teaching I should like to replicate. iii Acknowledgements The completion of this thesis as well as the knowledge I have gained in this process would not be possible without Heidi Chou, Josué Medellín-Azuara, Christina Buck and Kent Ke. They were present to meet, to skype to get clarifications on things and pushed to make sure all work necessary to set up model was done and made their time available to edit most of this work. Thanks also to Michelle Lent who was recruited into this effort much later but worked with incredible efficiency and positivity and helped us get things done. I would like to thank Prof. Jay Lund for his guidance, encouragement, enthusiasm and suggestions through the project that helped us get unstuck without whom this thesis would not have been completed, as well as his editorial assistance in preparing this document. Thanks to Charles Brush for his assistance with running the C2VSIM model, providing information and assistance with understanding the model. I will like to thank Prof. Tim Ginn and Prof. Graham Fogg for their ideas and comments while serving on my committee. iv Contents Abstract ......................................................................................................................................................... ii Dedication .................................................................................................................................................... iii Acknowledgements ...................................................................................................................................... iv Figures ........................................................................................................................................................ viii Tables ............................................................................................................................................................ x Chapter One: Introduction ........................................................................................................................... 1 Chapter Two: C2VSIM and Central Valley Groundwater ............................................................................. 6 2.1 Description of C2VSIM .................................................................................................................. 7 2.2 Geology of the Central Valley Geology and Flow Parameters in C2VSIM .................................. 13 2.2.1 Hydrogeologic Layers ................................................................................................................. 15 2.2.2 Rootzone Characterisation......................................................................................................... 19 2.2.3 Unsaturated Zone Characterisation ........................................................................................... 20 2.3 Water Budgets ............................................................................................................................ 21 2.3.1 Water Use (Surface Water & Groundwater for Agriculture and Urban Demands) ................... 22 2.3.2 Evapotranspiration ..................................................................................................................... 23 2.3.3 Deep Percolation of Precipitation and Irrigation Return Flows ................................................ 26 2.3.4 Reuse of Irrigation Water ........................................................................................................... 26 2.3.5 Stream flow and Stream-Aquifer Interaction ............................................................................ 26 2.3.6 Lake-Aquifer Interaction ............................................................................................................ 29 2.3.7 Diversion Losses ......................................................................................................................... 30 2.3.8 Tile Drain Outlows ...................................................................................................................... 30 2.3.9 Artificial Recharge ...................................................................................................................... 31 2.3.10 Boundary Inflow ....................................................................................................................... 31 2.3.11 Interbasin Inflow ...................................................................................................................... 32 2.3.12 Subsidence ............................................................................................................................... 33 2.3.13 Pumping ................................................................................................................................... 35 Chapter Three: Updating CALVIN based on C2VSIM .................................................................................. 39 3.1 Groundwater Conceptualization and goals of CALVIN ............................................................... 39 3.2 Location of Groundwater Reservoirs .......................................................................................... 42 v 3.3 Groundwater Conceptualization and Interaction with Other Elements in CALVIN .................... 45 3.4 Update of Groundwater Representation in CALVIN ................................................................... 47 3.4.1 Split Agricultural Return Flows to Surface Water and Ground Water (Terms 1a and 1b) ......... 48 3.4.2 Amplitude for Internal Reuse (Term 2) ...................................................................................... 51 3.4.3 Amplitude for Agricultural Return Flow of total applied water (<1) – Agricultural Areas (Term 3) ......................................................................................................................................................... 53 3.4.4 Net External Inflows to Groundwater (Term 4) ........................................................................ 55 3.4.5 Groundwater Basin Storage Capacity (Term 5) ......................................................................... 61 3.4.6 Minimum & Maximum Pumping Constraints (Term 6 & 7) ....................................................... 63 3.4.7 Representative Depth to Groundwater and Pumping Cost - Extracted from DWR Well Monitoring Data for year 2000 (Term 8) (by Christina Buck) ............................................................. 64 3.4.8 Surface Water Losses including Evaporation & Diversion losses to GW (Term 9) .................... 69 3.4.9 Artificial Recharge Operation Costs (Term 10) and Infiltration Fraction of Artificial Recharge (Term 11) ............................................................................................................................................. 69 3.4.10 Urban Return Flow to groundwater (Term 12) ........................................................................ 72 3.5 Calibration Process for Updated Base Case CALVIN ................................................................... 73 3.5.1 Description of the network representation of California’s intertied water system .................. 76 3.5.2 Base Case Calibration ................................................................................................................. 80 3.5.3 Calibrated Base Case CALVIN with new CALSIM II Delta Outflow Requirements and Constraints to Delta Exports .................................................................................................................................. 87 3.6 Limitations and Concluding Remarks 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