Yucaipa Valley Hydrogeology

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

The Yucaipa area is about 12 mi southeast of the city of San Bernardino and about 75 mi east of the city of Los Angeles in the upper part of the Santa Ana River drainage basin. Since about 1970 and especially during the 1990's, the widespread urbanization of southern California has extended inland from the coast into the Yucaipa area. Undeveloped land, agricultural land, and sparsely populated residential land have been converted into housing tracts. The net effect of this change in land use has been an increase in the demand for water, especially potable water for domestic use. Because the local supply of both surface water and ground water is limited in this semiarid region, water purveyors need an accurate assessment of water resources.

As part of a comprehensive hydrologic investigation in the Yucaipa Basin, efforts are focused on continuing to track the movement of imported water released into the Wilson Creek spreading ponds. To do this, water-quality data were collected and analyzed from 13 wells to monitor the absence or presence of imported water. Depth-dependent water-quality sampling was collected to determine recharge in selected areas. Water-quality data were collected and analyzed from 8 wells in the Crafton and Western Heights subbasins to access background levels of several constituents potentially influenced by recharge of water in spreading ponds expected in the near future. 

USGS works together with several water agencies and general public in the Yucaipa area to develop hydrogeologic understanding and water management plans for groundwater in the area.  The USGS will be providing the necessary technical guidance and support for San Bernardino Valley Municipal Water District to ensure success of the management plans.

Monitoring and Data Collection

Tracking the signal of imported water through the subsurface will be used to determine the direction of groundwater flow from recharge processes. Water-level monitoring will be used to measure pressure response from the decline of recharge activities. Continued collection of field measurements provide independent estimates of the magnitude and/or location of groundwater recharge that can be compared with and used to constrain estimates from future hydrologic models. Surface resistivity and duration of flow data will be used to help identify areas where recharge from streamflow may be occurring.

The USGS continues to operate and maintain the gaging stations and water-quality monitors in the upper Santa Ana River Basin including precipitation stations. Continuous recording water-level monitors are maintained at eight multiple-depth cluster well sites located in the Bunker Hill Basin and four sites in the Yucaipa Valley. Each of the Yucaipa Valley sites consists of between four to five well casings, with monitoring accomplished by using pressure transducers and electronic data loggers. All sites are equipped to transmit data hourly to NWIS.

Chemical and isotopic analyses of groundwater samples obtained from the multiple-depth well sites are being used to identify baseline 'native' water-quality conditions. Hydrogeologic technical support will be provided as requested by SBVMWD.

Investigations in the Yucaipa Basin focus on tracking the movement of imported water released into the Wilson Creek spreading ponds.

Relevance and Benefits

This project focuses on several contemporary hydrologic issues and provides a number of important benefits to the public. For example, it will:

• Advance knowledge of the hydrologic system in the Yucaipa Valley area. Much of this knowledge will be gained from development and calibration of a linked surface-water and ground-water flow processes.
• Provide unbiased data and results that will be used by the more than 20 water agencies in the area so that they can better resolve their multiple and continuing water issues.
• Provide water-resources information that will improve operation of local artificial-recharge basins, ground-water extractions, and ground-water cleanup facilities.
• Contribute to national databases used to develop and assess global climatological models.

Integrated Hydrologic Model

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.

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