Yucaipa Subbasin Integrated Hydrologic Model

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The USGS is developing a hydrologic model of the Yucaipa Subbasin to aid in evaluating and managing the groundwater resources in the area. The study results will provide a greater understanding of the geohydrology of the subbasin, and aid in the development of a groundwater-monitoring plan, as well as in the evaluation of potential hydrologic effects of future groundwater development and management actions on different parts of the subbasin.

location map of the Yucaipa area in Southern California.  Faults in the area are also displayed.

Location of the Yucaipa area, San Bernardino and Riverside Counties, California. (Public domain.)

A numerical flow model is needed as a tool that integrates all hydrologic data and understanding developed from previous and ongoing work in the basin. Development of a flow model in the Yucaipa Subbasin follows a similar approach used in the Bunker Hill and Rialto-Colton basins in which a model developed by USGS evolved into a tool used for active hydrologic management. The Yucaipa Subbasin contains complex hydrogeologic features that make it vital to incorporate detailed understanding of the geologic and hydrologic system into the numerical flow model, so that the model can ultimately be used as a groundwater management tool in the basin. Development of the model will occur over a period of four years. In addition, a preliminary recharge/runoff model for the contributing watershed will be developed. Several different techniques will be compared and evaluated to determine the method most suitable to quantify the amount of recharge and runoff from the upstream contributing watersheds. This model forms the basis for the input natural input components to the groundwater basin. Compiled data to calibrate and/or construct the integrated hydrologic model will include streamflow, precipitation, temperature, evapotranspiration, land use, groundwater levels, aquifer properties, groundwater pumping, and groundwater quality. The data will be organized in preparation for modeling and to allow easy updating with new data. These data and analyses will support next steps in the modeling process, including as development of a runoff/recharge model for the basin and upstream drainage area. The hydrogeologic model (including geologic, structural, and lithologic details) developed from the drillers’ logs database, geophysical surveys, and previous studies will be vetted and finalized. This analysis will be done in coordination and collaboration with USGS Research Geologists who have mapped the basin. These data and analyses will provide a foundation for numerical flow model. The groundwater flow model portion of the integrated hydrologic model will be constructed based on the data sets, hydrogeologic framework model, and recharge/runoff model. In future years, the integrated model will be calibrated and availability analyses and scenarios will be constructed and run. These will be used to analyze various water availability options. The integrated hydrologic model and analyses/scenario runs will be documented in a report.