http://hdl.handle.net/123456789/11 2026-08-03T16:27:20Z 2026-08-03T16:27:20Z http://hdl.handle.net/123456789/3195176 2020-11-05T12:53:27Z

Hydrogeology of Ash Flow Tuff: A Preliminary Statement Ash flow tuffs, silicic pyroclastic rocks commonly mapped as silicic lava flows (rhyolite, dacite, or quartz latite) on many pre‐1960 geologic maps, cover tens of thousands of square miles in the southwestern states and aggregate between 35,000 and 60,000 mi³ in the Great basin alone. In contrast to silicic lava flows but similar to basalts, ash flow tuffs are sheetlike bodies; individual flows have been traced for as much as 100 miles. Welding, the cohesion of molten glassy shards and pumice fragments during emplacement of these rocks, results in significant vertical variations in physical properties within individual flows. Interstitial porosity and permeability vary from 70% and 2 gpd/ft² (gallons per day per square foot), respectively, in nonwelded portions or zones of ash flows to less than 5% porosity and virtually zero permeability in densely welded zones. Primary and secondary joints spaced several feet apart in nonwelded zones are as close as a fraction of an inch in densely welded zones. Fracture transmissibility of welded zones within ash flow tuffs varies from 100–100,000 gpd/ft. The nonwelded zones are aquitards. Spring groups with discharges ranging from 20–200 cfs (cubic feet per second) emerge from welded tuff in eastern Idaho and Sumatra, Indonesia. The magnitude of the spring discharge attests to the regional hydraulic continuity of these strata. Development of groundwater from welded tuff in the Southwest appears several decades away because of depth of burial, large variations in yield, and locally poor water quality. Nevertheless, further study of these rocks is warranted to test the assumption common to many water budget studies that interbasin movement through and ‘mountain front recharge’ from silicic volcanic rocks are negligible.

http://hdl.handle.net/123456789/3195177 2020-11-05T12:53:27Z

Contribution of Atmospheric Chloride in Water from Selected Coastal Streams of Central California Chemical quality and discharge data were collected and analyzed from five streams draining watersheds between Half Moon Bay and Santa Cruz, California, to determine the contribution of atmospheric chloride to these coastal basins. Fifty‐nine percent of the total chloride leaving the basins underlain by Tertiary sedimentary rocks per year is atmospheric in origin. Nineteen percent of this atmospheric chloride contribution is introduced dissolved in rainwater, whereas the remaining 40% is brought into the basins as fine particulate dust, in ‘fog drip,’ or as an aerosol.

http://hdl.handle.net/123456789/3195178 2020-11-05T12:53:27Z

Hydrologic Response of a Young Pine Plantation to Weed Removal In May 1969 the weed vegetation on one plot in a 7‐year‐old red pine (Pinus resinosa, Ait.) plantation was killed by using herbicides. The site was a glacial outwash plain in Adams County, Wisconsin. Of the 27 cm of precipitation that occurred in June, July, and August of that year, evapotranspiration accounted for 16 cm on a plot with weeds and only 9 cm on the plot without weeds. But nearly all of this excess was lost from the root zone by a 61% increase in drainage associated with weed removal, so the increase of water available to plants was not great. The increase was most obvious in the surface layer beneath the trees where it amounted to 28%. In the openings between trees, the surface layer was actually drier owing to greater surface heating caused by removal of weeds. Important factors that amplified the effects of treatment were the erratic precipitation regime and the sandy texture of the soil.

http://hdl.handle.net/123456789/3195179 2020-11-05T12:53:27Z

Use of Fluorescein To Measure the Composition of Waterdrop Splash Fluorescein, a fluorescent compound, was used as a tracer to measure the amount of waterdrop water in splash after impact of the waterdrop in various depths of water. The addition to water of up to 50 ppm of fluorescein caused negligible changes in liquid density, surface tension, and viscosity. The tracer technique was successfully used to show the proportions of waterdrop water in splash from varying depths of target water.