Spring & Seep Geochemistry
Inyo/Los Angeles Cooperative Study

See Final Report Here

Cooperative Study Proposal

April 25, 2000

Project Title:
Shallow and Deep Groundwater Geochemistry and Source of Spring and Seep Water in the Owens Valley

Principal Investigators:
Aaron Steinwand and Randy Jackson, Inyo County Water Department
Saeed Jorat and Paula Hubbard, Los Angeles Department of Water and Power

Purpose

The purposes of this study are two-fold. First, basic water quality indices will be monitored quarterly for one year to develop a data base that could be used to assist restoration of spring waters required by the Green Book and Final Environmental Impact Report (FEIR) should any impacts occur. Secondly, the geochemical signatures of selected springs and seeps will be examined and compared to shallow and deep groundwater samples to identify the source of water. These results will be used to link spring and seep flows to particular aquifers. Understanding the linkage will improve groundwater models necessary to assess potential pumping effects.

Background

The Technical Group is required by the Inyo/LA Water Agreement and the FEIR to manage groundwater pumping from existing and new wells to Aavoid reductions in spring flows that would cause significant decreases or changes in spring associated vegetation.@ The Green Book (p.31) states that the Technical Group will identify and monitor areas of vegetation dependent upon springs and flowing wells. The FEIR (p.3-21) expands this monitoring commitment to seeps. The FEIR (p.3-21) also outlines management options to remedy potential impacts, AIf despite such management, significant decreases in spring flows occur that could cause significant decreases or changes in vegetation dependent upon such flows, management of groundwater pumping from wells affecting flow from the spring will be modified so that adequate spring flow resumes to supply the vegetation@. Recently, a program was instituted by LADWP to inventory springs and seeps in the valley (Ahlborn and Hill, 1998a&b; Ecosystem Sciences, 1998). That inventory identified many springs and prioritized them for monitoring. The monitoring program includes rudimentary sampling of water flow and water quality parameters, and some of that data may be acceptable to assist the effort proposed here. That inventory, however, is limited to a one-time sampling and contains no assessment of the hydrologic linkage of springs and seeps to their subsurface sources. Phreatophytic vegetation communities on the valley floor rely on periodic access to groundwater from the shallow aquifer for long-term survival. One option for pumping management to meet the water supply and vegetation protection goals of the Inyo/LA Water Agreement is to pump from wells sealed to the deep aquifer in preference to wells constructed in both the shallow and deep aquifers. Several tests have demonstrated that the timing and magnitude of drawdown in the shallow aquifer due to pumping from the deep aquifer is buffered by the less permeable confining layers separating them (Harrington, 1998; Jackson, 1997). While this strategy may reduce impacts to the shallow aquifer near pumping wells, it may transfer impacts to distant springs and seeps that rely on upward flow of water from the deep aquifer. The Inyo/LA Water Agreement relies on monitoring results to trigger management decisions, and the Green Book (p. 19) also states that mitigation is a secondary management tool if the attempt to avoid impacts is unsuccessful. The efficacy of the Green Book management techniques to detect and avoid potential impact to springs is questionable, and the management strategy should be revised to reflect the effects of sealed deep-aquifer pumping. Developing appropriate triggers for management of existing deep-aquifer pumping must include an assessment of the potential sensitivity of critical springs and seeps. The need for such an assessment is more urgent if pumping increasingly shifts to the deep aquifer as suggested in previous reports (Coufal et al., 1991; City of Los Angeles and Inyo County, 1987).

Geochemical characterization of spring and well water is a common technique applied to lend insight into the hydrogeology of springs and groundwater flow systems (Hem, 1985; Garrels and MacKenzie, 1967). In a classic study conducted by Garrels and MacKenzie (1967), spring water chemistry, source water chemistry (snow), and clay mineralogy in the Sierra Nevada of California were used successfully to reconstitute the weathering of the surrounding parent rocks. They demonstrated conclusively that hydrochemical analysis is a powerful tool to reconstruct likely flow paths, to determine sources of spring water, or to evaluate groundwater mixing in groundwater systems. The level of detail of that analysis is beyond the scope of this study, but several examples exist of studies conducted near the Owens Valley that relied on geochemistry to evaluate hydrology of closed basins. Hardie (1968) and Jones (1965) used geochemistry to evaluate the relationship of hydrology and controls on groundwater and soil salinity development in Saline and Deep Springs Valley, respectively. Similarly, Smith and Drever (1976) studied spring water chemistry at Teels Marsh, Nevada to assess processes affecting groundwater. Recently, Bredehoft and King (1999) and Farnham et al. (1999) used chemistry of springs in the Death Valley area to assess groundwater source and the possibility of impacts from construction of nuclear waste storage facilities at Yucca Mountain, Nevada. Studies similar in scope and objectives to this proposal have been conducted on Owens Lake to better understand the potential groundwater flow paths between sampling wells and sources of spring water (Font, 1995; Lopes, 1988). Additionally, in an ongoing Inyo/LADWP cooperative study, the source water for springs at Owens Lake was recently identified as an important unknown in the existing groundwater model. Because springs represent sensitive and valuable habitat, the consultants recommended the data gap must be addressed to accurately assess potential impacts of proposed pumping and before rational groundwater management plans could be developed (CDM, 1999).

Relying on geochemical analyses to investigate the hydrogeology of an area is less intrusive and usually less expensive than extensive drilling programs. Interpreting the geochemical data, however, is rarely straightforward, and such studies commonly rely on modeling of the solid and aqueous phase interactions, groundwater mixing, and evolution of groundwater geochemistry along likely flow paths (Back, 1966; Hardie and Eugster, 1970). For example, locally, Font (1995) relied heavily on geochemical models to investigate the complicated groundwater relationships on Owens Lake. Models have primarily been of two types; geochemical speciation and chemical mass balance to evaluate spatial and temporal changes along groundwater flowpaths (McCutcheon et al., 1992). Several models have been developed and are widely applied.

Tasks

1.     The first phase of this study will be to locate and evaluate existing water quality data collected by LADWP and other agencies for wells that may be located near springs and seeps of interest. If appropriate data exist, it could result in considerable cost savings for this study. The remainder of this proposal is written assuming no geochemical data appropriate to the objectives of this study are located.

2.     The list of springs and seeps developed by Ecosystem Sciences was consulted to identify appropriate areas to be sampled. Thirty-one springs were identified as potential candidates for sampling of routine water quality indicators (Table 1). For the spring source water determination, the list was narrowed down to valley floor springs and seeps likely to be affected if sealed deep aquifer pumping were increased. The short list of springsand locations of nearby deep and shallow monitoring wells is presented in Table 2 and on maps in Appendix A. Samples from two shallow and two deep wells for each spring were budgeted, but this may change after further investigation of the wells and sites. Eight adjacent mountain front springs on the east and west sides of the valley were selected to provide end members of groundwater chemistry for the flowpath analysis (Table 2). Flowpath analysis will assist groundwater modeling efforts to assess potential impacts to springs and seeps.

Sampling will be conducted quarterly for easily determined water quality parameters at the springs listed in Table 1 by a DWP hydrographer. The seasonal sampling is not expected to identify the source of spring waters, but the seasonal variability could provide insight regarding that question that would not be obtained with a single sampling date. Time series plots of the spring water data will be prepared. We understand that routine water quality measurements are being collected at selected springs as part of a microinvertebrate inventory conducted by Ecosystem Sciences (Don Sada, personal communication). As mentioned above, the first step of this study will identify all relevant data to avoid duplicating previous efforts. The proposed list of springs selected for regular sampling will undoubtably change after existing data are evaluated and the springs are visited in the field, but we do not expect the list to expand. It is, therefore, a liberal estimate of the number of field sites to be visited during this study.

3.     A one time sampling of a selected set of springs and nearby wells (Table 2) to measure a broader range of constituents will be performed to assess source waters. The chemical analyses are relatively expensive, and a one-time sampling is recommended here because it is likely that site to site variation in water chemistry will be greater than temporal variation. The need for additional sampling will be better assessed after evaluation of the initial sampling results. Some seeps have shallow groundwater but no obvious surface waters (Ecosystem Sciences, 1999). At these sites, tension lysimeters or passive groundwater collectors will be used to retrieve samples (Arndt and Richardson, 1993). Sample chemistry can be altered by degassing and contact with the atmosphere during collection. To minimize this source of error, selected analyses will be performed in the field for pH, electrical conductivity (EC), temperature, turbidity, and dissolved oxygen. Total alkalinity, bicarbonate, and carbonate concentrations will be determined within 24 hours of sample collection. Additionally, sample vials will be completely filled, and all samples will be kept cool during transport to the laboratory. Field sampling will be performed jointly by DWP and Inyo personnel. Analyses for the major aqueous species (Table 2) will be performed by the LADWP Water Quality Laboratory, or in the event that facility is unavailable, a commercial laboratory will be selected by Inyo and Los Angeles. Isotope chemistry will be performed by a commercial laboratory. Laboratory selection will be based on certification, methods employed, cost, and time to complete requested analyses.

Table 1: Springs and seeps to monitored quarterly. Spring/seep notation as given by Ecosystem Sciences (1999). Analyses will include pH, EC, temperature, dissolved Oxygen, and water flow.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2. Candidate springs and sampling strategy for groundwater source determination. Spring/seep notation as given by Ecosystem Sciences (1999).

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4.     Initial data analysis will include preparation of Stiff and Piper diagrams and ion ratios for visual inspection, screening, and sorting the geochemical data (Back, 1961; Freeze and Cherry, 1979). The computer software NETPATH and WATEQ4F (Ball and Nordstrum, 1991; Plummer, et al., 1994) or PHREEQ will be employed to assist identification of spring and seep source water. WATEQ4F is an equilibrium speciation model commonly applied to investigate the interactions among potential solid phases and aqueous species that may be controlling the geochemistry of multicomponent systems. As a quality control measure, the charge balance error calculated by the program will be used to assess the accuracy of the water analyses. NETPATH determines which mass balance reactions are feasible along a flowpath. Generally, the equation solved by NETPATH is:

Initial Waters + Reactant Phases = Final Water + Product Phases

This program will be used to evaluate the effects of evaporation, mineral precipitation and dissolution, and mixing with waters of different chemistry necessary to assess source of water at potentially affected springs. To perform the mass balance calculations, however, the program requires assumptions of the equilibrium solid phases present and constraints on chemical and isotopic species. Thus, it is advantageous to utilize this program in conjunction with an equilibrium model (WATEQ4F) to assist preparation of NETPATH models and interpretation of results. NETPATH contains a generalized version of WATEQ4F (WATEQFP), but we propose to use the parent program until differences in the results of the two models are evaluated. PHREEQ can perform similar modeling tasks as the combination of WATEQ4F and NETPATH, but it has the added capabiltiy to accomodate measurement error in the input data. Selection of the specific modeling software will be finalized after selection of the geochemical modeling consultant. Piper diagrams and calculated ion ratios will be examined qualitatively for groupings of data that have similar geochemical characteristics. The flow path relationships between groups, and the geochemical reactions required for one group to evolve to another will be evaluated by geochemical modeling.

5.     Ultimately, results from this study and a related study to determine confining layer properties could be used to improve the groundwater models to assist development of an acceptable strategy and monitoring program to manage deep aquifer pumping. Hence, eight springs located at the mountain fronts are included in the sampling list to allow a rudimentary flowpath analysis to be performed. If possible, results will be developed into GIS themes to facilitate analysis of the spatial and geochemical relationships between samples to infer groundwater flowpaths.

Product

At the conclusion of this cooperative study, a report will be prepared jointly by the two agencies or by the consultant under the direction from the principal investigators summarizing the data collected in each task, results of the modeling effort, and the findings of the study regarding the source of water in each spring.

Timeline

 

 

 

 

 

 

 

 

 

 

 

 

 

Summary of tasks

 

 

 

 

 

 

 

 

 

 

References

Ahlborn, Gary and Mark Hill. (draft dated 2-27-98). Lower Owens River Project, Technical Memorandum #12, Springs and seeps inventory and assessment, Task VII.C. Prepared for Los Angeles Department of Water and Power and Inyo County Water Department.

Ahlborn, Gary and Mark Hill. (draft dated 5-5-98). Lower Owens River Project, Supplement to Technical Memorandum #12: Protocol for spring and seep, Task VII.C. Prepared for Los Angeles Department of Water and Power and Inyo County Water Department.

Arndt, J.L. and J.L. Richardson. 1993. Temporal variations in the salinity of shallow groundwater from the periphery of some North Dakota wetlands. J. Hydrol. 141:75-105.

Back, W., 1961. Techniques for mapping of hydrochemical facies. Short papers, Geol. Surv. Res. D-380-D-382.

Back, W., 1966. Origin of hydrochemical facies of groundwater in the Atlantic coastal plain. USGS Prof. Pap. 498A.

Ball, J.W., and D.K. Nordstrom. 1991. Users manual for WATEQ4F, with revised thermodynamic data base and test cases for calculating major, trace and redox elements in natural waters. USGS Open File Report 91-183. 189pp.

Bredehoeft, J.D. and M.J. King. 1999. A geochemical evaluation of springs, Death Valley, California. Yucca Mountain Nuclear Waste Repository, 1998 Oversight Program Report (DRAFT) submitted to Inyo County, Feb. 1999.

Camp, Dresser, and McKee. 1999. Identification of data gaps, Owens Lake Evaluation. Client Review Draft Technical Memorandum. March 4, 1999.

City of Los Angeles and Inyo County. 1987. Feasibility of sealing the upper zones of existing production wells in the Owens Valley. Report to Inyo/Los Angeles Technical Group.

Coufal, E.L., W.R. Hutchinson, T.E. Griepentrog and R. Jackson. 1991. Deep test hole study: a report to the Inyo/LADWP Standing Committee from the Inyo/LADWP Technical Group. December, 1991.

Ecosystem Sciences (delivered 1-28-99). Lower Owens River Project, Springs and seeps inventory. Phase I. (raw data). Prepared for Los Angeles Department of Water and Power and Inyo County Water Department.

Font, K.R., 1995. Geochemical and isotopic evidence of hydrologic processes at Owens Lake, California. M.S. thesis. Univ. Nevada, Reno.

Farnham, I.M., K.H. Johannesson, A.K. Singh, K.J. Stetzenbach, and X. Zhou. 1999. Using multivariate statistical analysis of ground-water major cation and trace-element concentrations to evaluate ground-water flow in south-central Nevada. pp. 64-65. In J.L. Slate (ed.) Proc. Conf. on Status of Geol. Res. and Mapping in Death Valley National Park, Las Vegas, Nv. April 9-11, 1999. USGS Open-file Rep. 99-153.

Freeze, R.A, and J.A. Cherry. 1979. Groundwater. Prentice-Hall, Inc., Englewood Cliffs, New Jersey.

Garrels, R.M., and F.T. Mackenzie. 1967. Origin of the chemical compositions of some springs and lakes. pp. 222-242. In R.F. Gould (ed.) Equilibrium concepts in natural water systems. Adv. Chem. Serial 67. Amer. Chem. Soc.

Harrington, R.F., 1998. Internal Inyo County Water Department memorandum on continuation of the E/M 375 and E/M 382 operational testing. April 9, 1998.

Hardie, L.A., 1968. The origin of recent non-marine evaporite deposit of Saline Valley, Inyo Co., California. Geochim. et Cosmochim. Acta 32:1279-1301.

Hardie, L.A., and H.P. Eugster, 1970. The evolution of closed-basin brines. pp. 273-290, In

Min. Soc. Am. Spec. Pub. vol 3.

Hem, J.D., 1985. Study and interpretation of the chemical characteristics of natural water. 3rd ed. USGS Water-Supply Paper 2254, 263pp.

Jackson, R., 1997. Evaluation of the linkage of enhancement/mitigation wells 380 and 381 to the TS4 monitoring site. Memorandum Report to the Inyo/Los Angeles Technical Group.

Jones, B.F., 1965. The hydrology and mineralogy of Deep Springs Lake, Inyo County, California. USGS Prof. Paper 502-A. 53 pp.

Lopes, T.J. 1998. Hydrology and water budget of Owens Lake, California. Water Resources Center Publication 41107. Desert Research Institute, Reno.

McCutcheon, S.C., J.L. Martin, and T.O. Barnwell, Jr., 1992. Water quality. pp.11.1-11.73. In D.R. Maidment (ed.) Handbook of Hydrology. McGraw-Hill, New York, NY.

Plummer, L.N., E.C. Presetemon, and D.L. Parkhurst. 1994. An interactive code (NETPATH) for modeling NET geochemical reactions along a flow PATH--version 2.0. U.S.Geological Surv. Water Res. Invest. Rep. 94-4169, 130 pp.

Smith, C.L., and J.I. Drever. 1976. Controls on the chemistry of springs at Teels Marsh, Mineral County, Nevada. Geochim. et Cosmochim. Atca 40:1081-1093.

 
Appendix A

Maps of the springs/seeps selected for groundwater source determination and nearby shallow and deep monitoring well, flowing wells, and pumping wells.

(provided in earlier copies and additional copies available at the ICWD)

 

 Inyo/Los Angeles Cooperative Studies