Hydrology of the Yucaipa Groundwater Subbasin: Characterization and Integrated Numerical Model, San Bernardino and Riverside Counties, California

Scientific Investigations Report 2021-5118
Prepared in cooperation with San Bernardino Valley Municipal Water District
Edited by: Geoffrey Cromwell and Ayman H. Alzraiee


Executive Summary

Water management in the Santa Ana River watershed in San Bernardino and Riverside Counties in southern California is a complex task with various water purveyors navigating geographic, geologic, hydrologic, and political challenges to provide a reliable water supply to stakeholders. As the population has increased throughout southern California, so has the demand for water. The Yucaipa groundwater subbasin (hereafter referred to as “Yucaipa subbasin”), one of nine groundwater subbasins in what the California Department of Water Resources (DWR) refers to as the Upper Santa Ana Valley groundwater basin (California Department of Water Resources, 2016; the DWR naming convention is used within this report), is no exception; steady population growth since the 1940s and changes in water use has forced local water purveyors to regularly adapt their water infrastructure to meet demand. Groundwater has historically been the dominant source of water in the Yucaipa subbasin although recently, imported water via the California State Water Project has augmented the total water supply. Despite the influx of imported water, overall demand for groundwater continues to rise, and there is concern by local water managers that groundwater levels may adversely impact water supply and (or) decline to a point where it will be uneconomical to produce water, severely limiting the ability of local agencies to meet water-supply demand.

To better understand the hydrogeology and water resources in the Yucaipa subbasin, the U.S. Geological Survey (USGS) and the San Bernardino Valley Municipal Water District initiated a cooperative study to understand the hydrogeologic system of the Yucaipa subbasin and in the encompassing Yucaipa Valley watershed (YVW). A three-dimensional hydrogeologic framework model was constructed to quantify the structure and extent of hydrogeologic units. Historical and present-day groundwater conditions were characterized to evaluate the groundwater-flow system. Lastly, the Yucaipa Integrated Hydrological Model (YIHM) was developed to simulate the integrated surface-water and groundwater systems, including natural and anthropogenic (that is, human influenced) recharge and discharge throughout the study area from 1947 to 2014.

The Yucaipa subbasin is an inland groundwater basin located about 12 miles (mi) southeast of the City of San Bernardino and about 75 mi east of Los Angeles, California. The subbasin encompasses about 39 square miles (mi2), including the City of Yucaipa. The geographic extent of the Yucaipa subbasin was established by the California Department of Water Resources, who defined the boundaries of the subbasin based on hydrogeologic transitions between crystalline rock and basin-fill sediments, active fault strands, surface-water drainage divides, and a portion of an adjudicated groundwater management boundary. Two groundwater subbasins of the Upper Santa Ana Valley groundwater basin are adjacent to the Yucaipa subbasin, the San Bernardino groundwater subbasin to the west and the San Timoteo groundwater subbasin to the south.

The Yucaipa subbasin is encompassed by the YVW, which is in turn comprised of three sub-watersheds that represent surface-water flow across and within the Yucaipa subbasin. Although the Yucaipa subbasin is the specific area of interest for this study, the entire YVW was considered for the purposes of characterizing the hydrogeology of the Yucaipa subbasin and for development of the YIHM.

The purposes of this report are to (1) describe the hydrologic and hydrogeologic settings of the Yucaipa subbasin and aquifer system, (2) describe the construction and calibration of the fully coupled groundwater and surface-water flow model for the Yucaipa subbasin and the encompassing YVW, referred to as the YIHM, and (3) present numerical results, including water budgets and hydraulic heads, and the effect of pumping and climate stresses (precipitation and temperature) on water-budget components.

Suggested Citation

Cromwell, G., and Alzraiee, A., eds., 2022, Hydrology of the Yucaipa groundwater subbasin: Characterization and integrated numerical model, San Bernardino and Riverside Counties, California: U.S. Geological Survey Scientific Investigations Report 2021–5118, 4 p., https://doi.org/10.3133/sir20215118.

ISSN: 2328-0328 (online)

Study Area

Table of Contents

  • Acknowledgments
  • Executive Summary
  • Chapter A: Hydrogeologic Characterization of the Yucaipa Groundwater Subbasin
    • Introduction  
    • Hydrogeology  
    • Water Budget  
    • Groundwater Levels, Flow, and Movement  
    • Hydrologic Flow Barriers  
    • Water Chemistry  
    • Summary  
    • References Cited  
    • Appendix A1. Tables
  • Chapter B: Yucaipa Valley Integrated Hydrological Model
    • Acknowledgments  
    • Introduction  
    • Model Discretization  
    • Initial Conditions  
    • Precipitation-Runoff Modeling System Model Description  
    • MODFLOW Model Description  
    • Integration of Precipitation-Runoff Modeling System and MODFLOW  
    • Integrated Model Calibration  
    • Calibration Results  
    • Simulated Hydrologic Budget  
    • Model Limitations  
    • Summary and Conclusions  
    • References Cited  
    • Appendix B1. Calibration Using Ensemble Smoother  
    • Appendix B2. Evaluation of Streamflow Data Quality and Calibration Goodness-of-Fit
Publication type Report
Publication Subtype USGS Numbered Series
Title Hydrology of the Yucaipa groundwater subbasin: Characterization and integrated numerical model, San Bernardino and Riverside Counties, California
Series title Scientific Investigations Report
Series number 2021-5118
DOI 10.3133/sir20215118
Year Published 2022
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) California Water Science Center
Description Executive Summary: vi, 4 p.; Chapter A: viii, 81 p.; Chapter B: xii, 76 p.; 2 Data Releases
Country United States
State California
County Riverside County, San Bernardino County
Online Only (Y/N) Y
Additional Online Files (Y/N) Y
Google Analytic Metrics Metrics page
Additional publication details