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Wesley L. Bradford

Publications and source records attributed to Wesley L. Bradford.

6 recordsLinked to original sources
USGS1980

Distribution of nitrate in the unsaturated zone, Highland-East Highlands area, San Bernardino County, California

Nitrogen in the unsaturated soil zone in the Highland-East Highlands area of San Bernardino County, Calif., has been suspected as the source of nitrate in water from wells. Plans to recharge the local aquifers with imported surface water would raise the water table and intercept that nitrogen. This study was made to describe the distribution of inorganic nitrogen and other chemical constituents and nitrogen-using bacteria in the unsaturated zone, to relate nitrogen occurrences, in a general way, to present and historical land use, and to attempt to predict nitrogen concentrations in ground water after recharge. Some generalized correlations between nitrogen occurrence and land use were observed. In 11 of 13 test holes, the maximum nitrate-nitrogen (NO 3 - -N) concentrations occurred within 10 feet of the surface, suggesting that the major source of nitrogen is from the surface at these sites. Test holes were ranked according to maximum NO 3 - -N in the top 10 feet, total NO 3 - -N in the top 10 feet, and total NO 3 - -N in the top 40 feet. In all three rankings, the top seven test holes were the same--five in or near present or historical agricultural areas (primarily citrus groves), one in a feedlot, and one adjacent to an abandoned sewage-treatment plant. Two test holes in historically uninhabited areas ranked lowest. The control test hole in an uninhabited area ranked high in geometric mean of ammonium-nitrogen concentration (NH 4 + -N), suggesting that present in freshly weathered granite. The geometric means of NH 4 + -N concentrations in six of eight citrus-related test holes were significantly lower than in the control hole, suggesting that irrigation in citrus groves may have created conditions favoring nitrification of the primary NH 4 + -N. Rank correlation analyses between various measurements in test holes showed that high NO 3 - -N concentrations tend to occur with high specific conductance and chloride concentrations in soil extracts. If recharge is carried out as planned, assuming complete mixing of the recharge water and interstitial pore water in the top 20 feet of the saturated zone, NO 3 - -N concentrations in water at the top of the saturated zone may exceed 10 milligrams per liter in seven areas studied. Concentrations could reach as high as 66 milligrams per liter in the worst case projected. The highest concentrations may be found in three areas that are now, or were recently, citrus groves.

California↗
USGS1980

Dissolved-solids concentrations and loads in return flows to the Colorado River from agricultural land in southern California

The dissolved-solids concentration in Colorado River water increases from less than 50 mg/L (milligrams per liter) at the river's origin to about 700 mg/L at the California border and to about 900 mg/L at the United States-Mexico boundary. Much of the latter increase is due to depletion by agricultural use and irrigation return water with salts leached from soils under cultivation. Forty sites in three agricultural areas--Fort Mojave, Bard Valley, and Palo Verde Valley--were sampled to describe the dissolved-solids concentrations in return flows. Emphasis was on Palo Verde Valley. In the Fort Mojave area, the dissolved-solids concentration of Colorado River water was about 700 mg/L, while the concentration in water at the tile-drain convergence averaged about 2,500 mg/L. In the closed sump that presently receives all irrigation return, concentrations ranged from 812 to 1,760 mg/L. In Bard Valley, water diverted from the river had an annual mean dissolved-solids concentration of about 835 mg/L. During the study, concentrations in the two main drains carrying irrigation return water ranged from 953 to 1,290 mg/L. Selected drains in Palo Verde Valley were sampled several times to determine dissolved-solids loads from subareas within the valley. Loads determined in this study were compared with those of an earlier study. In agreement with the earlier study, loads were found to be largest from three subareas in the southern half of the valley and comparatively small from the four subareas in the northern half. Smaller loads were found in this study from all subareas, however. The differences are thought to be due to generally lower water discharge observed in drains during this study.

California↗
USGS1980

Quality of urban runoff, Tecolote Creek drainage area, San Diego County, California

The quality of storm runoff from a 9.2-square-mile urbanized watershed, Tecolote Creek, San Diego County, Calif., was studied during nine storms from September 1976 through May 1977. Specific conductance reached 2,100 micromhos and total residue concentrations reached 2,770 milligrams per liter. The chemical oxygen demand concentration in 95% of the samples exceeded 50 milligrams per liter, a concentration that may be sufficient to cause severe oxygen depletion in areas of the receiving water, Mission Bay. Lead concentrations in all samples exceeded concentrations thought to affect some aquatic organisms. Median total nitrogen and total orthophosphorus concentrations were far in excess of concentrations known to cause nuisance growth of algae in lakes. Fecal coliform bacteria concentrations greatly exceeded recommended levels for primary contact recreation water. Concentrations of pesticides--heptachlor, malathion, chlordane, DDT, diazinon, and dieldrin--frequently exceeded the recommended maximums for marine or freshwater aquatic systems. Total loads of selected constituents are calculated and may be used to estimate the impact of runoff on the receiving water. (USGS)

Water-Resources Investigations Report↗
USGS1979

Distribution of nitrate and related nitrogen species in the unsaturated zone, Redlands and vicinity, San Bernardino County, California

Nitrogen in the unsaturated soil zone in the vicinity of Redlands in San Bernardino County, Calif., has been suspected as the source of nitrate in water from wells. Plans have been made to recharge the aquifer with imported surface water. If this occurs, the rising water table will intercept soluble nitrate in the unsaturated zone. This study was made to quantify and delineate the distribution of the nitrate in the unsaturated zone. Thirteen test holes were drilled in areas of various land uses, and samples of the unsaturated-zone materials were obtained with depth. In 10 of the test holes, the maximum nitrate-nitrogen (N03--N) concentrations occurred within 10 feet of land surface suggesting N03--N sources at the surface. Ranking the test holes according to near-surface N03--N concentrations showed that, of the top six, only two are in irrigated citrus areas. One is in an abandoned feedlot. Of the lowest six, four are in irrigated citrus areas and one is in the Santa Ana River channel. The control test hole ranked fourth suggesting that relatively high N03--N concentrations can occur in near-surface soils even in the absence of human habitation. Analysis according to one conceptual model suggests that raising the water-table altitude by aquifer recharge will intercept N03--N now in the unsaturated zone causing increases in N03--N concentrations in water from wells of up to 48 milligrams per liter. The largest increases will occur in the vicinity of irrigated citrus areas. (Woodard-USGS).

Water-Resources Investigations Report↗
USGS1978

Water chemistry of the Redwood Creek and Mill Creek basins, Redwood National Park, Humboldt and Del Norte Counties, California

A 2-year study was made in the Redwood Creek and Mill Creek drainage basins of Redwood National Park to determine existing chemical water-quality conditions and to identify the effects of logging on water quality in the main stems and tributaries of the two basins. Overall, the chemical water quality of the main stems and the tributaries is excellent, suitable for most beneficial uses. Dissolved-solids concentrations range from 25 milligrams per liter in the Redwood Creek basin and 21 milligrams per liter in the Mill Creek basin during the rainy season to 139 and 49 during the dry season. Water shifts from a mixed calcium-sodium bicarbonate-chloride type toward a calcium bicarbonate type from the end of the wet season to the end of the dry season. It shifts back toward a mixed calcium-sodium bicarbonate-chloride type from the end of the dry season to the end of the wet season. The pH shifts with the water type from a median value of 6.80 in the rainy season to 7.37 in the dry season. Nitrogen and phosphorus concentrations are generally too low to support nuisance algae but are high enough, in some streams, to support modest populations, particularly in the main stem where light levels are high. Trace-metal concentrations are low, typical of clean streams. Evidence suggests that dissolved calcium and bicarbonate in stream water is produced by weathering of the Franciscan assemblage underlying the basins but that chlorides are transported inland from the ocean as dry fallout and spray and in rain. Exposure of the surface soils to the elements, either by logging or by natural causes such as sparse vegetation, seems to accelerate weathering, which leads to a calcium bicarbonate water type. Logging accelerates weathering most in the tributary watersheds with regoliths derived from sandstone and least in those with regoliths derived from schist; however, the data suggest that the rate of weathering in a schistose watershed can increase dramatically if soil disruption is extensive. Studies during storms indicated that specific conductance and alkalinity were two to three times as likely to decrease at the discharge peak in logged watersheds as in forested ones. This suggests that overland flow containing lower concentrations of soil-derived dissolved solids than flow from other sources is a larger component of peak flow in logged watersheds than in forested watersheds. Comparing a storm in November 1974 to one in February 1975, nitrate concentration increased significantly from November to February in a stream draining a logged watershed and decreased significantly in a stream draining a forested watershed. Then from the rainy season to the dry season, nitrate decreased in both logged and forested watersheds. This pattern suggests that soil nitrate produced by fixation and organic decomposition early in the rainy season tends to wash out of logged watersheds but be taken up in tree growth in forested watersheds. As the dry season progresses, base flow containing little nitrate enters the streams, causing a decrease in nitrate concentration. By contrast, the other plant nutrients--phosphorus, Kjeldahl nitrogen, ammonium, and dissolved organic carbon--all decreased in streams from the November 1974 storm to the February 1975 storm and changed little from the rainy season through the dry season. This pattern suggests that these materials tend to accumulate in the soil during the dry season and be washed out and diluted as the rainy season progresses. Very little reaches the water table due to soil absorption so that little appears in the base flow during the dry season.

California↗