SANTA ANA RIVER WASTE LOAD ALLOCATION MODEL UPDATE SUMMARY REPORT Part 1 of 3: Text PREPARED FOR: Santa Ana Watershed Project Authority June 19, 2020 GEOSCIENCE Support Services, Inc. Ground Water Resources Development P.O. Box 220, Claremont, CA 91711 | P: 909.451.6650 | F: 909.451.6638 | www.gssiwater.com Santa Ana River Waste Load Allocation Model Update - Summary Report 19-Jun-20 THIS REPORT IS RENDERED TO THE SANTA ANA WATERSHED PROJECT AUTHORITY AND BASIN MONITORING PROGRAM TASK FORCE AS OF THE DATE HEREOF, SOLELY FOR THEIR BENEFIT IN CONNECTION WITH ITS STATED PURPOSE AND MAY NOT BE RELIED ON BY ANY OTHER PERSON OR ENTITY OR BY THEM IN ANY OTHER CONTEXT. AS DATA IS UPDATED FROM TIME TO TIME, ANY RELIANCE ON THIS REPORT AT A FUTURE DATE SHOULD TAKE INTO ACCOUNT UPDATED DATA. THIS DOCUMENT HAS BEEN CHECKED FOR COMPLETENESS, ACCURACY, AND CONSISTENCY BY THE FOLLOWING PROFESSIONALS: ___________________________________ Lauren Wicks, PG Project Geohydrologist PG No. 9531 ___________________________________ Johnson Yeh, Ph.D., PG, CHG Principal CHG No. 422 ___________________________________ Dennis E. Williams, Ph.D., PG, CHG President CHG No. 139 Copyright © 2020 GEOSCIENCE Support Services, Inc. GEOSCIENCE retains its copyrights, and the client for which this document was produced may not use such products of consulting services for purposes unrelated to the subject matter of this project. No portion of this report may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, mechanical, electronic, photocopying, recording or otherwise EXCEPT for purposes of the project for which this document was produced. i Santa Ana River Waste Load Allocation Model Update - Summary Report 19-Jun-20 SANTA ANA RIVER WASTE LOAD ALLOCATION MODEL UPDATE SUMMARY REPORT CONTENTS 1.0 INTRODUCTION ......................................................................................................................... 1 1.1 Purpose and Scope ..................................................................................................................... 1 1.2 Project Location ......................................................................................................................... 2 1.3 Model Background ..................................................................................................................... 2 2.0 DATA COLLECTION ..................................................................................................................... 5 2.1 Land Use ..................................................................................................................................... 5 2.2 Soil Types .................................................................................................................................... 6 2.3 Precipitation Data ...................................................................................................................... 6 2.4 Evaporation Data ........................................................................................................................ 8 2.5 Streamflow Data ........................................................................................................................ 8 2.5.1 Discharges ................................................................................................................. 10 2.5.2 Seven Oaks Dam Outflow ......................................................................................... 13 2.5.3 Stormwater Management Facilities and Channel Type ............................................ 13 2.6 TDS and TIN Data ..................................................................................................................... 14 2.7 Quality Assurance / Quality Control ......................................................................................... 19 3.0 WASTE LOAD ALLOCATION MODEL UPDATE ............................................................................ 20 3.1 2017 WLAM HSPF Development .............................................................................................. 20 3.1.1 Model Code ............................................................................................................... 20 3.1.1.1 HSPF Modules................................................................................................ 21 3.2 Data Needs for the 2017 WLAM HSPF ..................................................................................... 22 3.2.1 Land Surface Elevations ............................................................................................ 22 3.2.2 Soil Types .................................................................................................................. 23 3.2.3 Land Use .................................................................................................................... 24 ii Santa Ana River Waste Load Allocation Model Update - Summary Report 19-Jun-20 3.2.4 Precipitation .............................................................................................................. 25 3.2.5 Evapotranspiration .................................................................................................... 26 3.2.6 Streamflow ................................................................................................................ 27 3.2.6.1 External Inflow .............................................................................................. 27 3.2.6.2 Discharges ..................................................................................................... 27 3.2.6.3 Surface Water Diversions for Off-Channel Recharge .................................... 28 3.2.6.4 Prado Wetlands ............................................................................................. 29 3.2.6.5 OCWD Operations at and below Prado Dam ................................................ 30 3.2.7 Stream Channel Characteristics ................................................................................ 30 3.2.8 Rising Water .............................................................................................................. 31 3.2.9 TDS and TIN ............................................................................................................... 32 3.2.9.1 TDS and TIN in Runoff and Percolation from Precipitation ........................... 33 3.2.9.2 TDS and TIN in Discharges ............................................................................. 33 3.2.9.3 TDS and TIN in Rising Groundwater .............................................................. 33 3.2.9.4 TDS and TIN in Prado Wetlands Outflow ...................................................... 34 3.2.9.5 Nitrogen Reaction Rate Coefficients ............................................................. 34 3.3 WLAM Differences ................................................................................................................... 35 3.3.1 Initial Comparison of 2008 WLAM and HSPF ............................................................ 40 4.0 2017 WLAM HSPF CALIBRATION .............................................................................................. 44 4.1 Calibration Process ................................................................................................................... 44 4.2 Calibration Criteria ................................................................................................................... 45 4.3 Streamflow Calibration Results ................................................................................................ 47 4.3.1 Streamflow Outlier Analysis ...................................................................................... 55 4.4 TDS and TIN Calibration ........................................................................................................... 57 4.4.1 Water Budgets and Mass Balance ............................................................................ 60 4.5 Rising Water Sensitivity Analysis .............................................................................................. 64 4.5.1 Rising Water Calibration Approaches ....................................................................... 64 4.5.2 Rising Water Sensitivity Analysis ............................................................................... 68 4.6 Precipitation Sensitivity Analysis .............................................................................................. 72 iii Santa Ana River Waste Load Allocation Model Update - Summary Report 19-Jun-20 5.0 PREDICTIVE SCENARIO ASSUMPTIONS ..................................................................................... 74 5.1 Hydrologic Period ..................................................................................................................... 74 5.2 Land Use ................................................................................................................................... 75 5.3 Streamflow ............................................................................................................................... 75 5.3.1 Discharges to Surface Water ..................................................................................... 75 5.3.1.1 De Minimis Discharge .................................................................................... 75 5.3.1.2 Recycled Water Discharge ............................................................................. 75 5.3.1.2.1 Riverside RWQCP ...................................................................................