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K.J. Hitt

Publications and source records attributed to K.J. Hitt.

7 recordsLinked to original sources
USGS2007

Factors influencing ground-water recharge in the eastern United States

Ground-water recharge estimates for selected locations in the eastern half of the United States were obtained by Darcian and chloride-tracer methods and compared using statistical analyses. Recharge estimates derived from unsaturated-zone (RUZC) and saturated-zone (RSZC) chloride mass balance methods are less variable (interquartile ranges or IQRs are 9.5 and 16.1 cm/yr, respectively) and more strongly correlated with climatic, hydrologic, land use, and sediment variables than Darcian estimates (IQR = 22.8 cm/yr). The unit-gradient Darcian estimates are a nonlinear function of moisture content and also reflect the uncertainty of pedotransfer functions used to estimate hydraulic parameters. Significance level is <0.001 for nearly all explanatory variables having correlations with RUZC of <-0.3 or >0.3. Estimates of RSZC were evaluated using analysis of variance, multiple comparison tests, and an exploratory nonlinear regression (NLR) model. Recharge generally is greater in coastal plain surficial aquifers, fractured crystalline rocks, and carbonate rocks, or in areas with high sand content. Westernmost portions of the study area have low recharge, receive somewhat less precipitation, and contain fine-grained sediment. The NLR model simulates water input to the land surface followed by transport to ground water, depending on factors that either promote or inhibit water infiltration. The model explains a moderate amount of variation in the data set (coefficient of determination = 0.61). Model sensitivity analysis indicates that mean annual runoff, air temperature, and precipitation, and an index of ground-water exfiltration potential most influence estimates of recharge at sampled sites in the region. Soil characteristics and land use have less influence on the recharge estimates, but nonetheless are significant in the NLR model. ?? 2006 Elsevier B.V. All rights reserved.

Journal of Hydrology↗
USGS2006

Generalized boundaries of the National Water-Quality Assessment (NAWQA) Study-Unit Investigations in the conterminous United States 1991-2001

This is a GENERALIZED version of the boundaries and codes used for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program Study-Unit investigations in the conterminous United States, excluding the High Plains Regional Ground-Water Study. The data set represents the areas studied during the first decade of the NAWQA Program, from 1991-2001 ("cycle 1"). The coverage is intended only for drawing ILLUSTRATIONS, NOT for spatial analysis. The sources of this coverage were the full resolution NAWQA study unit coverage, which is available at http://water.usgs.gov/lookup/getspatial?nawqacyc1 and the coastline from a 1:2 million county coverage generalized for display at the scale of 1:34 million.

Report↗
USGS2006

Generalized boundaries of the National Water-Quality Assessment (NAWQA) Study-Unit Investigations in the conterminous United States 2001-2012

This is a GENERALIZED version of the boundaries and codes used for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) Program Study-Unit investigations in the conterminous United States, excluding the High Plains Regional Ground-Water Study. The data set represents the areas to be studied during the second decade of the NAWQA Program, from 2001-2012 ("cycle 2"). The coverage is intended only for drawing ILLUSTRATIONS, NOT for spatial analysis.

Report↗
USGS1997

Risk of nitrate in groundwaters of the United States - A national perspective

Nitrate contamination of groundwater occurs in predictable patterns, based on findings of the U.S. Geological Survey's (USGS) National Water Quality Assessment (NAWQA) Program. The NAWQA Program was begun in 1991 to describe the quality of the Nation's water resources, using nationally consistent methods. Variables affecting nitrate concentration in groundwater were grouped as 'input' factors (population density end the amount of nitrogen contributed by fertilizer, manure, and atmospheric sources) and 'aquifer vulnerability' factors (soil drainage characteristic and the ratio of woodland acres to cropland acres in agricultural areas) and compiled in a national map that shows patterns of risk for nitrate contamination of groundwater. Areas with high nitrogen input, well-drained soils, and low woodland to cropland ratio have the highest potential for contamination of shallow groundwater by nitrate. Groundwater nitrate data collected through 1992 from wells less than 100 ft deep generally verified the risk patterns shown on the national map. Median nitrate concentration was 0.2 mg/L in wells representing the low-risk group, and the maximum contaminant level (MCL) was exceeded in 3% of the wells. In contrast, median nitrate concentration was 4.8 mg/L in wells representing the high-risk group, and the MCL was exceeded in 25% of the wells.Nitrate contamination of groundwater occurs in predictable patterns, based on findings of the U.S. Geological Survey's (USGS) National Water Quality Assessment (NAWQA) Program. The NAWQA Program was begun in 1991 to describe the quality of the Nation's water resources, using nationally consistent methods. Variables affecting nitrate concentration in groundwater were grouped as `input' factors (population density and the amount of nitrogen contributed by fertilizer, manure, and atmospheric sources) and `aquifer vulnerability' factors (soil drainage characteristic and the ratio of woodland acres to cropland acres in agricultural areas) and compiled in a national map that shows patterns of risk for nitrate contamination of groundwater. Areas with high nitrogen input, well-drained soils, and low woodland to cropland ratio have the highest potential for contamination of shallow groundwater by nitrate. Groundwater nitrate data collected through 1992 from wells less than 100 ft deep generally verified the risk patterns shown on the national map. Median nitrate concentration was 0.2 mg/L in wells representing the low-risk group, and the maximum contaminant level (MCL) was exceeded in 3% of the wells. In contrast, median nitrate concentration was 4.8 mg/L in wells representing the high-risk group, and the MCL was exceeded in 25% of the wells.

Environmental Science & Technology↗
USGS1990

Summary of selected characteristics of large reservoirs in the United States and Puerto Rico, 1988

This report presents selected characteristics of 2,728 reservoirs and controlled natural lakes located within the 50 States of the United States and the Commonwealth of Puerto Rico. Data are presented for reservoirs that have normal capacities of at least 5,000 acre-ft or maximum capacities of at least 25,000 acre-ft and that were completed as of January 1, 1988. Reservoir data include: location, maximum capacity, normal capacity, surface area, drainage area, year completed, and use. The normal capacities of the 2,728 reservoirs and controlled natural lakes total more than 467 million acre-ft, and the combined surface areas for 2,362 of those reservoirs total almost 16 million acres. More than 9% (259) of the reservoirs are located in California. The total normal capacity of reservoirs in California is more than 40 million acre-ft (about 8.6% of the total normal capacity for the United States and Puerto Rico), and the total surface area is almost 700,000 acres (about 4.4% of the listed total surface area for the United States and Puerto Rico). (USGS)

Open-File Report↗