ENVIRONMENTAL FORENSICS, 2018 VOL. 19, NO. 2, 99–111 https://doi.org/10.1080/15275922.2018.1448909 Understanding the source of water for selected springs within Mojave Trails National Monument, California Andy Zdon, PG, CHg, CEGa, M. Lee Davisson, PGb and Adam H. Love, Ph.D.c aTechnical Director – Water Resources, PARTNER ENGINEERING AND SCIENCE, INC., Santa Ana, CA, Sacramento, CA; bML Davisson & Associates, Inc., Livermore, CA; cVice President/Principal Scientist, Roux Associates, Inc., Oakland, CA ABSTRACT KEYWORDS While water sources that sustain many of the springs in the Mojave Desert have been poorly Water resources; clipper understood, the desert ecosystem can be highly dependent on such resources. This evaluation mountains; bonanza spring; updates the water resource forensics of Bonanza Spring, the largest spring in the southeastern groundwater; forensics; Mojave Desert. The source of spring flow at Bonanza Spring was evaluated through an integration isotopes of published geologic maps, measured groundwater levels, water quality chemistry, and isotope data compiled from both published sources and new samples collected for water chemistry and isotopic composition. The results indicate that Bonanza Spring has a regional water source, in hydraulic communication with basin fill aquifer systems. Neighboring Lower Bonanza Spring appears to primarily be a downstream manifestation of surfacing water originally discharged from the Bonanza Spring source. Whereas other springs in the area, Hummingbird, Chuckwalla, and Teresa Springs, each appear to be locally sourced as “perched” springs. These conclusions have important implications for managing activities that have the potential to impact the desert ecosystem. Introduction above Bonanza Spring. Identification of future impacts General information and data regarding springs in the from water resource utilization becomes problematic if Mojave Desert are sparse, and many of these springs are initial baseline conditions are unknown or poorly under- not well understood. Bonanza Spring rises in the Clipper stood. This analysis was performed with the intent to Mountains within the newly established Mojave Trails better understand the water source that sustains Bonanza National Monument, San Bernardino County, California Spring, neighboring Lower Bonanza Spring, and the des- (Figure 1). Bonanza Spring is within the southeastern ert ecosystem that is dependent on those resources. Mojave Desert, a sparsely populated area, and has gener- Bonanza Spring is the largest spring in the southeastern ally been assumed to be a perched spring disconnected Mojave Desert. Despite its large size relative to other from the basin-fill aquifer system. Rapid growth and springs, Bonanza Spring is a fifth–sixth magnitude spring competition for water resources in the Mojave Desert is (Kresic, 2010), with its surface flow, not inclusive of an ongoing issue and results in the need for a balancing evapotranspiration, varying around 10 gallons per min- of competing uses and priorities. These include provid- ute. Small springs such as those identified in this investi- ing water to an expanding population, preserving water- gation, frequently get overlooked in hydrologic dependent ecological resources, and expanding needs of investigations since their discharges are commonly water for commercial development including alternative inconsequential to the overall water budget of the area energy generation facilities. being studied. Such oversight is problematic when evalu- In the case of Bonanza Spring, substantial groundwa- ating the sensitivity of critically important resources for ter development is proposed for export out of the region. vegetation and wildlife, both resident and migratory. Proposed groundwater development in this area is antici- Bonanza spring supports a substantial riparian area that pated to be in excess of the groundwater recharge to the belies its relatively small surface expression of water flow basin, resulting in basin aquifer drawdown from pump- (Figure 2). That the spring is perennial is indicated by ing with upgradient impacts to groundwater elevations the presence of freshwater snails (Physidae sp.) that are CONTACT Andy Zdon, PG, CHg, CEG [email protected] Technical Director – Water Resources, PARTNER ENGINEERING AND SCIENCE, INC., 1761 E. Garry Avenue, Santa Ana, CA 92705, 135 L Street, Sacramento, CA 95814, D: 916-237-0252. Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/uenf. © 2018 Informa UK Limited, trading as Taylor & Francis Group 100 A. ZDON ET AL. Figure 1. Location of Bonanza Spring within Mojave Trails National Monument (adapted from Wilderness Society, 2017). reliant on fresh water to survive. These invertebrates are area of the Mojave has received attention because of the currently being identified to species level (Parker, 2017, proposed Cadiz groundwater storage and recovery proj- pers. comm.) as many of these invertebrates can be ect (e.g., Metropolitan Water District of Southern endemic to the springs they live in. California, 2001; Davisson, 2000; Davisson and Rose, While detailed regional hydrogeologic investigations 2000; CH2M Hill, 2011; and Geoscience Support Serv- in the Mojave region are typically sparse, the exception ices, 2011). More recently, a Mojave Desert-wide spring to this is in the area southwest of Bonanza Spring. This survey (Andy Zdon & Associates, 2016) was completed on lands managed by the U.S. Bureau of Land Manage- ment (BLM) that included springs in the Clipper Moun- tains (Bonanza Spring, Lower Bonanza Spring, Hummingbird Spring, Lost Dutch Oven Spring, Falls Spring, Burnt Spring, and Chuckwalla Spring). Other springs of interest in the area include Vernandyles and Theresa Springs in the Marble Mountains, and the numerous springs in the Old Woman Mountains. These springs have been assumed in the past to be local springs – perched springs that rise as a result of surfacing of water that is recharged within its local watershed and not in communication with aquifers of more regional extent. The areas of the local watersheds for each of the Figure 2. Photograph of Bonanza Spring. key springs evaluated for this investigation are ENVIRONMENTAL FORENSICS 101 approximately 50 acres for Bonanza Spring (and Lower reports and documents. These investigations have Bonanza Spring), 147 acres for Hummingbird Spring, 25 occurred over several decades and the project-specific lit- acres for Teresa Spring, and 20 acres for Chuckwalla erature is substantial. Of principal note related to the Spring. current project are geochemical and recharge-estimation Due to the striking differences in physical character investigations by Lawrence Livermore Laboratory between Bonanza Spring and other springs in the Clipper (Davisson and Rose, 2000), a limited field spring survey Mountains, this study sought a greater understanding of conducted in the Marble Mountains to support the draft Bonanza Spring and the causes for its physical differences. environmental impact report (Kenney Geoscience, 2011) and an assessment associated with potential project- related impacts to springs (CH2M Hill, 2011). The field Previous studies activities associated with these groundwater development Hydrologic investigations in the California desert have related investigations were on a reconnaissance level and generally been focused on answering inquiries regarding few springs in the Clipper Mountains, and neither of a specific need. In the Bonanza Spring area (southeastern the springs in the Marble Mountains (Theresa and Mojave Desert), there have been three phases of investi- Vernandyles), were identified. gation, as follows: 1) an early reconnaissance phase dur- During 2015 and 2016, a spring survey was conducted ing the early decades of the 20th century, conducted to (Andy Zdon & Associates, 2016) for U.S. BLM lands in identify presence or absence of available water at springs their Needles, Barstow, and Ridgecrest Districts and other desert waterholes to facilitate safe travel, and (Bonanza Spring is within their Needles District). Infor- to identify potential bases of operation for more detailed mation regarding the location and physical characteris- scientific investigations in the region (Zdon, 2013); 2) tics of the springs in this study was found in the files of investigations related to development of a water resource the Needles District of the BLM (U.S. Bureau of Land available for export (what is today known as the Cadiz Management [BLM], 2015). For the purposes of that Project). Investigations related to the Cadiz project have investigation, 436 springs were identified of which 312 focused on the wellfield production and potential were inspected during the period from September 2015 impacts to the alluvial aquifer in the Fenner Valley through February 2016. Of that number, two springs Groundwater Basin and surrounding hydrologically- were identified in the Marble Mountains (one spring, linked groundwater basins; and 3) a recent effort to com- Theresa Spring has had surface flow on two visits with prehensively document and understand individual substantial signs of Desert Bighorn Sheep activity and springs on public lands throughout the region. wildlife-watering infrastructure present) and seven The early reconnaissance phase investigations in this springs were identified in the Clipper Mountains (includ- area were conducted by Mendenhall (1909) and ing Bonanza Spring and Lower Bonanza Spring), shown Thompson (1921, 1929). Mendenhall described