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It has been a decade
since the techniques for groundwater and vegetation management were developed and
incorporated into the Inyo/Los Angeles Water Agreement and its technical appendix, the
Green Book. At the time these techniques were adopted, it was recognized that there would
be a need for continuing research and cooperative studies to achieve the goals of the
Water Agreement. Consequently, the Water Agreement was designed to be flexible to allow
adoption of improved techniques to ensure the environmental protection and water supply
goals are met.
 Left:Meterological instruments used to measure
evapotranspiration from an akali meadow.
Photo by Bob Harrington, ICWD.
(Click on photo to enlarge).At its June 1998 meeting, the
Inyo/Los Angeles Standing Committee directed the Inyo/Los Angeles Technical Group to
prepare cooperative study proposals for consideration. Eight draft proposals were prepared
by ICWD scientists and forwarded to LADWP in June 1999. The proposed studies were directed
specifically at improving the scientific models used to predict the effect of pumping on
the water table and soil water and at quantifying how Owens Valley plant communities
respond when several environmental factors change simultaneously (including water level
fluctuations caused by pumping).
Discussions between LADWP and Inyo County continued throughout 1999 to work through
questions raised by LADWP regarding the purposes and eventual use of results from the
proposed studies. Eventually, the scope of work, staffing, time lines, and budgets for the
study proposals were agreed upon and five were approved by the Standing Committee. Three
more proposals are in the final stages of preparation.
The following is the list of cooperative studies, including the principal
investigators, the study objectives, and an update on the status of each study. Copies of
the proposals are available at ICWD and can also be found on the ICWD website at:
www.inyowater.org.
Development of Hydrological Modeling Tools
Robert Harrington, ICWD; Saeed Jorat, LADWP. Approved by the Standing
Committee, May 11, 2000.
The purpose of this study is to improve hydrological models developed by previous
cooperative studies to evaluate the impact of groundwater pumping, weather variations,
surface water management, and other hydrologic changes on groundwater levels. Because
groundwater modeling is the only method for consistent interpretation of groundwater data
and evaluation of management options, this task is a prerequisite to fulfill the
monitoring and technical goals of the Water Agreement. Inyo County and LADWP want to
jointly develop a common set of modeling tools so that methods and analyses are understood
and accessible to each agency.
Development of a Model for Predicting Phreatophyte Water Use and Soil Water
Replenishment
Aaron Steinwand, Robert Harrington, ICWD; Saeed Jorat, Paula Hubbard, LADWP
Proposal is in final stages of preparation.
The purpose of this study is to combine information from vegetation, groundwater,
precipitation, and soil water monitoring into a model to predict depletion and
replenishment of stored soil water above a fluctuating water table. This capability will
help protect Owens Valley vegetation by predicting how long soil water will support the
vegetation after pumping commences. If soil water information will continue to be used to
trigger pumping decisions, this type of model is needed by the Technical Group to evaluate
the environmental effects of proposed pumping scenarios and to provide reliable forecasts
of expected pumping yields. An expert on soil water modeling will be selected to assist
the principal investigators with this study.
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Evapotranspiration from
Groundwater-Dependent Plant Communities: Comparison of Micrometeorological Measurements
and Vegetation-based Measurements
Robert Harrington, Aaron Steinwand, ICWD; Paula Hubbard, David Martin, LADWP
Approved by Standing Committee, March 23, 2000.
The objective of this study is to provide direct measurements of evapotranspiration (ET),
the combination of evaporation from the ground surface and plant water use, using
micrometeorological methods to corroborate current estimates of vegetation transpiration.
If the method is accurate, estimating ET from simple vegetation measurements offers
important advantages for groundwater management. ET estimates are essential to the Green
Book methods for managing pumping and may remain an important component of groundwater
management strategies in the future. Results from this study will be applied to improve
the ET component of numerical groundwater models (study #1) and soil water models (study
#2). Characterization of Confining Layer Hydrologic Conductivity and Storage
Properties in the Owens Valley
Randy Jackson, ICWD; Saeed Jorat, LADWP
Approved by Standing Committee March 23, 2000.
The purpose of this study is to determine confining layer hydrologic properties to assist
groundwater modeling efforts (study #1) and to improve the management of wells sealed to
the deep aquifer. Pumping from deep aquifers potentially could be managed differently than
the Green Book methods. Without information to be developed by this study, however, the
magnitude and timing of the water table drawdown from pumping deep aquifers are difficult
to predict, complicating any assessment of the effects of different pumping scenarios. A
stepwise approach is proposed, starting with analysis of existing data and progressing to
low and high intensity field projects, if necessary.
Shallow and Deep Groundwater Geochemistry and the Source of Spring and Seep Water in
the Owens Valley
Aaron Steinwand, Randy Jackson, ICWD; Saeed Jorat, Paula Hubbard, LADWP
Approved by the Standing Committee June 16, 2000.
Springs and seeps are valuable and sensitive habitats in the Owens Valley. This study has
two objectives. First, basic water quality indices will be monitored seasonally for one
year to develop a database to be used to assist restoration of spring waters should any
impacts occur. Secondly, the geochemical signatures of water from selected springs and
seeps will be examined and compared to shallow and deep groundwater samples to identify
the source of the water. These results will be used to link spring and seep flows to
particular aquifers to improve groundwater models (study #1) used to assess potential
effects of pumping on these areas. An expert in geochemical modeling will be selected by
the fall of 2000 to assist the principal investigators with this study.
Application of Canonical Community Ordination (CANOCO) to Assess Owens Valley
Vegetation Change
Sally Manning, ICWD; David Martin, LADWP
Approved by Standing Committee March 23, 2000.
To manage groundwater pumping to avoid adverse changes in vegetation, it is imperative to
quantify the extent that water table fluctuations and other environmental factors affect
vegetation over the long term. This study will apply complex statistical techniques to an
extensive dataset of vegetation measurements collected by ICWD vegetation staff to
quantify the importance of several environmental factors influencing vegetation changes
observed in the last decade.
Inventory and Classification of Riparian Vegetation in the Owens Valley for Use in
Future Monitoring
To understand and measure the effects of groundwater pumping and surface water flows on
vegetation requires quantitative data on what vegetation is present and appropriate
techniques to monitor it. The objective of this study is to inventory, map, and classify
riparian (Type D) vegetation on Los Angeles-owned land in the Owens Valley to improve
monitoring and management of these areas. This study was suggested in the Green Book but
has not been completed. The Standing Committee agreed at its March 23, 2000, meeting that
this work will be conducted by a consultant selected jointly by ICWD and LADWP, and that
the contract will be managed by LADWP. The consultant will be selected this year to allow
fieldwork to begin by March 2001.
Development of a Demographic Model for Nevada saltbush (Atriplex torreyi)
Sally Manning, ICWD; David Martin, LADWP
Approved by Standing Committee March 23, 2000.
The purpose of this study is to use existing data for Nevada saltbush collected by ICWD
vegetation staff to develop a model that could allow researchers and managers to make
predictions about future population trends of this plant species, based on present
conditions. Nevada saltbush is a native shrub that commonly invades meadows subjected to
pumping. It has the potential to out-compete grass species and change the character of the
plant community in a way not allowed under the Water Agreement. In some areas, this
conversion may have already occurred before the baseline vegetation inventory of
1984-1987. It is unclear whether, once begun, saltbush invasion can be halted and whether
existing saltbush-dominated communities are sustainable.
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