Pajaro Valley Hydrologic Model Base-Case Scenario

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1 Pajaro Valley Hydrologic Model Base-Case Scenario Board of Directors Meeting March 23, 2011 Presented by: Brian Lockwood, P.G., Hydrologist

2 Acknowledgements, Base-Case The concept for the Base-Case scenario was developed by: Mary Bannister, P.G., C.Eg., General Manager, PVWMA Brian Lockwood, P.G.,Staff Hydrologist, PVWMA Lidia Gutierrez, Gutierrez Consultants Martin Feeney, P.G., C. Hg., Consulting Hydrogeologist Randy Hanson, Research Hydrologist, USGS The Base-Case scenario was built and modeled by: Randy Hanson Brian Lockwood

3 Acknowledgements, PVHM Development of the model was a complex process. The following people were instrumental in the development of the PVHM: Randall T. Hanson, Research Hydrologist, Principal Scientist U.S. Geological Survey, San Diego, CA Claudia Faunt, Ph.D., P.E., Hydrologist U.S. Geological Survey, San Diego, CA Wolfgang Schmid, Ph.D., Research Hydrologist, University of Arizona, Tucson, AZ Model Technical Advisory Committee (TAC) Andy Fisher, Ph. D., UCSC Derrik Williams, P.G., C.Hg., SqCWD Howard Franklin, P.G., MCWRA John Eiskamp, Ph. D., PVWMA Mike Cloud, P.G., (County of SC) Warren Koenig, Ch. E. Martin Feeney, P.G., C. Hg. TAC Moderator Consulting Hydrogeologist Jonathan Lear, P.G., C. Hg., Senior Hydrogeologist Monterey Peninsula Water Management District Brian Lockwood, P.G., Staff Hydrologist

4 Presentation Overview Why a new model? Model Concepts A Brief Review Base-Case Scenario Objective Assumptions Results Implications Future Work Hanson et al. (in prep.)

5 The Need for a New Model The IGSM proprietary model code has been subject of some criticism from modeling community PVMWA contracted with the U.S. Geological Survey to develop a robust, defensible model utilizing public domain code (MODLOW 2005) Incorporate new data (pumpage, land use, precipitation, etc.) now available as a result of Agency's monitoring programs Develop tool to evaluate and compare various water management scenarios to balance basin

6 Improvement Over Previous Models Internally-calculated agricultural pumpage and recharge Metered municipal pumpage Improved conceptualization of hydrostratigraphy More robust surface and groundwater linkage Open, peer-reviewed development

7 What is a Groundwater Model?

9 Basin Geology: Map View Four geologic units exposed at the surface: Alluvium Upper Aromas Purisima Basement Units are heterogeneous (vary spatially) Hanson et al. (in prep.)

10 Basin Geology: Profile View 6 Model Layers: Alluvium Alluvial Confining Unit Upper Aromas Aromas Confining Unit Lower Aromas Purisima Hanson et al. (in prep.)

11 Determine the basin s water budget (shortfall) following a simulation into the future, given the Agency s existing projects. Base-Case Scenario: Objective Hanson et al. (in prep.)

12 Base-Case Scenario: Assumptions Coastal Distribution System deliveries of up to 7,150 acre-feet (AF) per year. Land Use held constant (to 2009) Municipal & Rural Residential pumpage held constant The variations in local weather conditions of the next thirty years will be similar to the last thirty years.

13 Base-Case Scenario: Preliminary Results The existing projects cause a reduction in sea water intrusion, but not a cessation. Wet years result in some recharge (2,500 AF). Dry years result in overdraft (-22,500 AF). Average shortfall is 12,000 acre-feet per year for the Base-Case simulation period.

14 Historical and Simulated Coastal Flows

15 What the Shortfall Represents The volume of additional water supplies necessary to balance the water budget. Average shortfall of 12,000 acre-feet Project delivery of 7,150 acre-feet Shortfall plus Delivered Water is comparable to supplies needed as stated by the 2002 BMP 18,500 acre-feet of total additional supply.

16 Future Work Development of water management scenarios to simulate in order to support the Basin Management Plan update process. Pajaro River at Murphy s Crossing, 3/21/2011 Photo by Casey Meusel

17 Additional Information Hydrologic Model of the Pajaro Valley, Santa Cruz and Monterey Counties, California Hanson et al., in review Simulation and Analysis of Conjunctive Use with MODFLOW s Farm Process Hanson et al., 2010, in Ground Water Simulation of an Aquifer-Storage-and- Recovery (ASR) System for Agricultural Water Supply using the Farm Process in MODFLOW for the Pajaro Valley, Monterey Bay, California Hanson et al., 2008 Simulation and Analysis of Conjunctive Use with MODFLOW s Farm Process Hanson et al., 2008

18 Additional Information, cont. MODFLOW-2005, The US- Geological Survey Modular Ground-Water Model The Groundwater Flow Process Harbaugh, A. W The Farm Process, Version 2 Schmid, Wolfgang, and Hanson, R.T., 2009 Links to references may be found on the Agency s website: references.shtml

19 Thank You.. -- Questions?

Hydrogeologic Conceptual Models for Regional Flow Systems

Hydrogeologic Conceptual Models for Regional Flow Systems R.T. Hanson, U.S. Geological Survey One Water Hydrologic Flow Model USGS MODFLOW-OWHM Session 4 Groundwater Subbasin Baseline Historic and Current