The Owens Valley Monitor 2002-2003

Research Aims to Improve Management

Since 2000, Inyo County Water Department (ICWD) and LADWP have been investigating ways to improve the way LADWP manages water resources in the Owens Valley. Following are status reports on the studies being conducted by ICWD and LADWP. Copies of the study proposals and reports are available at ICWD and on the ICWD website at www.inyowater.org.

Development of Hydrological Modeling Tools
Robert Harrington, ICWD; Saeed Jorat, LADWP
Funded by LADWP and the California Department of Water Resources

This study is aimed at developing tools to evaluate the impact of groundwater pumping, climatic variations, surface water management, and other hydrologic changes on groundwater levels. The study addresses both statistical and numerical modeling tools. The statistical models have been updated, the error analysis and driving variables refined (Harrington, 2001), and the models have been extended to provide predictions at monitoring sites (Steinwand and Harrington, 2003a). These advances have enabled ICWD technical staff to evaluate "what-if" scenarios, such as how much water table recovery would have occurred without the groundwater pumping restrictions of the Drought Recovery Policy (Steinwand and Harrington, 2003b). The numerical modeling part of this study aims at developing the USGS groundwater model for the Owens Valley into a tool for use by ICWD and LADWP staff. Inyo County has hired Wes Danskin, the developer of the USGS model (Danskin, 1998), to conduct a post-audit of the model, where the model's predictions for 1989 through 2002 are compared to what actually occurred. The model has been installed on ICWD and LADWP computer systems, data for the post-audit have been assembled, and the consultant is currently putting the data into the model. Additionally, data from the ET study (see below) have been used to develop refined coverages of ET for input into the numerical model. Estimated completion: March 2004.

Development of a Model for Predicting Phreatophyte Water Use and Soil Water Replenishment
Aaron Steinwand, Robert Harrington, ICWD
Funded by the Department of Water Resources

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 to evaluate the environmental effects of proposed pumping scenarios and to provide reliable forecasts of expected pumping yields. The study is underway.

Evapotranspiration from Groundwater-Dependent Plant Communities: Comparison of Micrometeorological and Vegetation-Based Measurements
Robert Harrington, Aaron Steinwand, ICWD;
Paula Hubbard, David Martin, LADWP
Funded by LADWP and Department of Water Resources

Evapotranspiration (ET), the conversion of liquid water to vapor, plays a key role in both the management mechanisms implemented in the Inyo/Los Angeles Water Agreement and in the Owens Valley water budget. The purpose of this study is to measure ET using specialized weather stations and compare these measurements to the Water Agreement’s methods and the Kc method (Steinwand et al., 2001) of calculating plant-water requirements. Three years of ET, soil water, and plant cover measurements have been collected in various Owens Valley plant communities.       At sites where vegetation is connected to the water table, measured ET agreed with Kc estimates. Multiple measurements of vegetation cover may be necessary to insure that the annual maximum plant cover is well-characterized (Steinwand et al., 2002). Results collected so far have been coupled with vegetation cover estimates derived from satellite imagery (Elmore et al., 2000) to generate improved coverages of ET for the regional groundwater model (Harrington and Steinwand, 2002). Estimated completion: April 2004.

Characterization of Confining Layer Hydrologic Conductivity and Storage Properties in the Owens Valley
Randy Jackson, ICWD; Saeed Jorat, LADWP
Funded by LADWP

The purpose of this study is to determine confining layer hydrologic properties to assist groundwater modeling efforts and to improve the management of wells sealed to the deep aquifer. Pumping from deep aquifers potentially could be managed differently than the Water Agreement methods. Without the information to be developed by this study, however, it is difficult to predict the magnitude and timing of water table drawdown from pumping deep aquifers. This complicates assessment of the effects of different pumping scenarios. The first phase of this study has been completed, including a sensitivity analysis and an analysis of available aquifer test data. In the future, ICWD and LADWP will improve the GIS maps developed under the first phase of the study, improve the characterization of the confining layer, perform deep-well operational tests, and improve procedures to manage groundwater pumping from the deep aquifer.

Shallow and Deep Groundwater Geochemistry and the Source of Spring and Seep Water in the Owens Valley
Aaron Steinwand, Randy Jackson, ICWD;
Saeed Jorat, LADWP
Funded by LADWP

One purpose of this study is to conduct an intensive sampling campaign at selected springs, monitoring wells, surface water, and pumping wells to determine the geochemical characteristics of the groundwater. The primary goal of the study is to better understand the source of groundwater emanating from the springs. Typically, deeper groundwater differs chemically from shallower groundwater. The linkage of spring water to either a shallow or deep source or some combination affects the potential for pumping to impact these areas. The study is being conducted by LADWP, ICWD, Montgomery Watson Harza (MWH), and Dr. Randy Bassett of Geochemical Technologies Corporation. The field sampling was conducted in March and April 2002, and samples were sent to MWH and University of Arizona laboratories for analysis. Most lab work was completed quickly, but some analyses required a few months to complete. Based on the preliminary results, the group decided to collect additional samples from a small number of wells in April 2003. Two of the wells were newly installed near one spring area in 2003. Completion of the final report is tentatively set for fall 2003.

Application of Canonical Community Ordination (CANOCO) to Assess Vegetation Change
Sally Manning, ICWD; David Martin, LADWP

This study will apply statistical techniques to an extensive dataset of vegetation measurements collected by ICWD vegetation staff to quantify the importance of several environmental factors, such as water table fluctuations, influencing vegetation changes observed in the last decade.
     Since 2000, the principal investigators have worked independently, studying factors influencing vegetation change. Dr. Manning has since determined that it may be reasonable to use multiple linear regression as the analytical method. Results of preliminary evaluations have been produced for internal review and were presented by Dr. Manning at the 2002 meeting of the Ecological Society of America.

Inventory and Classification of Riparian Vegetation in the Owens Valley for Use in Future Monitoring
Sally Manning, ICWD; David Martin, LADWP
Funded by LADWP

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 (the technical appendix to the Water Agreement) 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 the contract will be managed by LADWP. Work was to begin in March 2001. Currently, LADWP is reviewing a draft request for proposals and outlines of areas to be inventoried.

Development of a Demographic Model for Nevada saltbush (Atriplex torreyi)
Sally Manning, ICWD; David Martin, LADWP

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 species. 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. It is unclear whether, once begun, saltbush invasion can be halted and whether existing saltbush-dominated communities are sustainable.
     Since 2000, the principal investigators have worked independently on this study. Dr. Manning continues to collect field data, and a preliminary report was recently completed.

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