Characteristics of fluvial sediment in Ohio streams and estimates of sediment yield are reported. Results are based on data from several daily record stations and 5 years of intermittent record from a 38-station network. Most of the sediment transported by Ohio streams is in suspension. Mean annual bedload discharge, in percentage of mean annual suspended-sediment discharge, is estimated to be less than 10 percent at all but one of the sediment stations analyzed. Duration analysis shows that about 90 percent of the suspended sediment is discharged during 10 percent of the time. Concentration of suspended sediment averages less than 100 milligrams per liter 75 percent of the time and less than 50 milligrams per liter 50 percent of the time. Suspended sediment in Ohio streams is composed mostly of silt and clay. Sand particle content ranges from 1 to 2 percent in northwestern Ohio to 15 percent in the east and southeast. Sediment yields range from less than 100 tons per square mile per year (35 tonnes per square kilometer per year) in the northwest corner of Ohio to over 500 tons per square mile per year (175 tonnes per square kilometer per year) in the southern part, in Todd Fork basin, lower Paint Creek basin, and the Kentucky Bluegrass area. Yield from about 63 percent of Ohio's land area ranges from 100 to 200 tons per square mile per year (35 to 70 tonnes per square kilometer per year).

Ground-water conditions were studied in a 148-square-raile area in southwestern Nevada County, California, which lies in the foothills of the Sierra Nevada.There, the area is underlain chiefly by hard and dense metavolcanic and plutonic rocks of pre-Tertiary age.Nevada County is experiencing a rapid growth in population, and ground water is being used to supply most of the new developments. Water systems in much of the area, however, are having difficulty in meeting the increased demand for water.Ground water in this part of the county occurs chiefly in fractures in the hard rocks and moves through a zone that, in general, lies above a depth of about 215 feet and that is less than 200-feet thick.Favorable sites for wells are those where saturated fractures occur in the hard rocks. These fractures probably trend northwestward or southwestward, and most probably occur above a depth of about 215 feet. Consequently, the deeper that wells have to be drilled to find water, the more likely that their yields will be small.Most wells in the study area average about 180 feet in depth and yield less than 18 gallons per minute.

After almost a century of activity and publication of approximately 2,100 water-resources related reports for the State of California, one needs to ask: Have we as an agency improved the level of understanding of the hydrologic environment in the State? Have we provided sufficient data and interpretive products that are necessary for sound decisionmaking to the water-management community? A century of existence certainly demonstrates an historical role for the U.S. Geological Survey in the hydrologic community. The resulting 2,100 reports continue to serve as the foundation of hydrologic knowledge for the State of California. Additionally, hydrologic historians will note: (1) The evolution and sophistication of the investigative and interpretive tools used to collect and transfer hydrologic data and knowledge to the water user community, and (2) a strong and steadfast adherence to the essence of science and the maintenance of our unbiased and nonregulatory stance in the midst of highly controversial and political issues. The justification for this stance is simple the need has existed and will continue to exist for an unbiased entity such as the U.S. Geological Survey to produce scientific, credible information. The major national water issues for the Water Resources Division in 1988 correspond well to water issues in the State of California. These issues are (1) Water availability and competition for this water; (2) quality of water; and (3) management of water and land resources. Studies being conducted by the U.S. Geological Survey and described in this publication are, for the most part, in support of providing data and interpretation to address these issues. As an agency, we are aware of and dedicated to the premise that credible data are obtained only when subjected to consistent, discipline related, quality-assurance programs. Throughout the Water Resources Division, continuous quality-assurance programs are conducted of all the activities that influence and ensure the quality of our products and services. These documented and proven quality-assurance programs provide to the hydrologic community necessary confidence that our products and services will meet the most stringent criteria. Several of the most relevant and visible studies being conducted by the California District deal with selenium toxicity in the western San Joaquin Valley; groundwater export from the Owens Valley, coupled with vegetation survivability studies; hydrodynamics variability in San Francisco Bay; reclaimed water use; seawater intrusion in the Santa Barbara area; and involvement in the water-quality standard/water-rights hearing for the San Francisco Bay/Delta. These studies and the others described herein are providing valuable data and methods development that continue to contribute significantly to the science of hydrology and the water-management community within the State.

GROUNDWATER ISSUES Ground water is an abundant and important natural resource in California. An average of 16.6 million acre-feet of fresh ground water (20 percent of the total withdrawn in the United States) is withdrawn annually to supply 39 percent of the freshwater used in the State. Of the total fresh ground water withdrawn, 70 percent is used for irrigation, 25 percent for public supply, 2 percent for industrial self-supplies, 1 percent for domestic supplies, 1 percent for mining, and 1 percent for livestock, thermoelectric power, and commercial self-supplies. Groundwater sources supply more than 18 million people (69 percent of the population). The major issues related to ground water in California are: Effects of agricultural practices on water quality, Saltwater intrusion in central and south coastal aquifers, and Conjunctive use of surface and ground water in southern California.

Selenium toxicity in the western San Joaquin Valley, groundwater export from the Owens Valley coupled with vegetation survivability studies, and the pending water-quality standards/water-rights hearing for the San Francisco Bay/Delta are just a few of the controversial and important efforts with which we are involved. All these studies are providing valuable data and methods development that contribute significantly to the science of hydrology.