Gl Introduction Gl Purpose and scope G2 Background G2 Description of study area G3 Plant communities G3 Study design G5 Methods G9 Evaluation of drawdown G10 Site K G10 Site D G12 Site H G12 Site B G12 Soil water responses G12 Site K G15 Site D GL7 Site H G19 Site B G20 Vegetation responses G20 Vegetative cover G20 Response to precipitation G21 Response to changes in depth to ground water G24 Xylem pressure potential G25 Seasonal variation G28 Variation in predawn xylem pressure potential with changes in soil water content G29 Variation between transects G30 Plant growth G32 Response to precipitation G32 Response to changes in depth to ground water G33 Phenological stages G34 Summary and conclusions G34 References cited G36 FRONTISPIECE Perspective and oblique view of Owens Valley, California, showing the dramatic change in topographic relief between the valley and surrounding mountains. FIGURES 1. Map showing location of study area and water-table drawdown sites G4 2. Photograph showing view looking southeast across southern Owens Valley G5 3. Photographs showing major plant communities in Owens Valley G6 4. Diagrams showing location of pump-equipped and monitoring wells for water-table drawdown sites G8 5. Photograph showing use of point-frame apparatus G9 6-18. Graphs showing: 6. Groundwater levels at water-table drawdown sites Gil 7. Idealized soil matric potential profile in soil with water-table depth of 3.5 meters near end of summer G13 Contents 8. Soil water content and soil matric potential in soil profile at transect Dl, October 1986 G15 9. Soil matric potential profiles at transects K1-K5 G16 10. Soil matric potential profiles at transects D1-D6 G18 11. Soil water content and soil matric potential at transect HI, March 1986 G19 12. Soil matric potential profiles at transect HI G20 13. Soil matric potential profiles at transect B1 G20 14. Combined measurements of cover repetition for all sites and species measured in September, 1983-86 G21 15. Normalized cover repetition for phreatophytic shrubs at each transect G22 16. Seasonal precipitation at Bishop and Independence during each growing season, 1982-86 G24 17. Cover repetition measured in September, 1984-86, for phreatophytic shrubs and grasses at sites H and B G26 18. Normalized cover repetition for individual species at site B measured in September 1985 and 1986 G30 19-22. Schematic plots showing: 19. Midday xylem pressure potential by month for Nevada saltbush, rabbitbrush, greasewood, sagebrush, and shadscale G41 20. Predawn xylem pressure potential by month for Nevada saltbush, rabbitbrush, greasewood, sagebrush, and shadscale G42 21. Midday xylem pressure potential at all vegetation transects G43 22. Predawn xylem pressure potential at all vegetation transects G46 23-28. Graphs showing: 23. Plant growth in relation to precipitation at sites K and D

Water-chemistry, biological, and habitat data were collected from 70 sites on Midwestern streams during August as part of an integrated, regional water-quality assessment by the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program. The study area includes the Corn Belt region of southern Minnesota, eastern Iowa, and west-central Illinois, one of the most intensive and productive agricultural regions of the world. The focus of the study was to evaluate the condition of woodedriparian zones and the influence of basin soildrainage characteristics on water quality and biological-community responses. This report includes a description of the study design and site-characterization process, sample-collection and processing methods, laboratory methods, quality-assurance procedures, and summaries of data on nutrients, herbicides and metabolites, stream productivity and respiration, biological communities, habitat conditions, and agriculturalchemical and land-use information.

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The objective of this study was to determine the incidence of Giardia lamblia acquisition in back-country travelers to a wilderness area, provide longitudinal follow-up on the incidence of symptomatic gastrointestinal illness and relate such information to concentrations of Giardia cysts in water samples from a high-use area. A prospective cohort non-interventional study of 41 healthy adult backcountry travelers from age 19 to 71 years in Desolation Wilderness, Lake Tahoe Basin was carried out. The incidence of Giardia cyst acquisition in backcountry travelers was only 5.7% (95% CI 0.17–20.2%). Mild, self-limiting gastrointestinal illness occurred in 16.7% of subjects (95% CI 4.9%–34.50%), none of whom demonstrated G. lamblia infection. Water sampling from three popular stream sites revealed cyst contamination to be generally at low levels with cyst concentrations in the single digit range for every 100 gallons filtered. G. lamblia contamination of water occurs, but at low levels. Acquisition of this parasite may be infrequent in backcountry recreationalists. Symptomatic gastrointestinal illness following wilderness travel can be due to other etiologies. Our findings may not be representative of all wilderness areas, but suggest that in the absence of documented G. lamblia infection, persons symptomatic following travel may suffer a self-limiting gastrointestinal illness. In such circumstances, empiric therapy for giardiasis is tempting but difficult to justify.