WATER-QUALITY ASSESSMENT OF THE OZARK
PLATEAUS STUDY UNIT, ARKANSAS, KANSAS,
MISSOURI, AND OKLAHOMAANALYSIS OF
INFORMATION ON NUTRIENTS, SUSPENDED
SEDIMENT, AND SUSPENDED SOLIDS, 1970-92
By Jerri V. Davis, James C. Petersen, James C. Adamski, and David A. Freiwald
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Abstract
Water-quality data collected during water
years 1970-90 (October 1 to September 30) for
83 surface-water sites and during 1970-92 for 395
ground-water sites in the 48,000 square mile
Ozark Plateaus study unit of the National Water-
Quality Assessment Program were analyzed using
selected descriptive and statistical methods. The
water-quality data include nutrient (nitrogen and
phosphorus), suspended-sediment, and suspended-
solids data; and ancillary information on
fertilizer use, animal waste, sewage-treatment
plants, and land use.
Statistically significant differences existed
in surface-water quality that can be attributed to
physiography, land use, and other effects. The
sites that were considered to be substantially
affected by sewage-treatment plants had the largest
concentrations of nutrients. Nutrient concentrations
generally were larger at sites associated
with agricultural basins than at sites associated
with forested basins.
Statistically significant differences existed
in the quality of ground water that can be attributed
to hydrogeologic and land-use effects. Nutrient
concentrations generally were largest where
the water source is indicated to be shallow in origin
and where parts of the hydrogeologic units are
in agricultural land-use areas.
Water quality has changed at several surface-
water sites since 1970. Nutrient concentrations
appear to have increased at some sites and
decreased at other sites. Causes of these apparent
trends are not known, but many of the sites with
apparent trends are in agricultural areas.
Surface-water loads of nutrients and suspended
sediment were affected by several factors
including streamflow, climate, drainage area, reservoir
operation, and inputs from point and nonpoint
sources. Annual loads were largest in large
basins, with large inputs of nutrients or sediment
during periods of high streamflows at locations
where reservoir operation effects are not substantial.
TABLE OF CONTENTS
- Abstract
- Introduction
- Description of the Ozark Plateaus study unit
- Geology and hydrology
- Climate, population, land use, and water use
- Nitrogen and phosphorus fertilizer use
- Animal and municipal sources of nutrients
- Assessment approach
- Selection of properties and constituents for analysis
- Evaluation of water-quality data
- Surface-water quality data
- Ground-water quality data
- Sources of available water-quality data
- Methods of data analysis
- Treatment of censored data
- Assessment of water-quality conditions
- Descriptive statistics
- Hypothesis tests
- Analysis of long-term trends
- Estimation of loads
- Characteristics of water-quality data
- Spatial and temporal distribution of surface-water quality data
- Spatial and temporal distribution of ground-water quality data
- Water-quality conditions
- Surface water
- Nutrients
- Nitrite plus nitrate
- Ammonia
- Total ammonia plus organic nitrogen
- Total nitrogen
- Total phosphorus
- Orthophosphate
- Suspended sediment and suspended solids
- Comparison of indicator and integrator sites
- Meramec River
- Osage River
- White River
- Relation of selected nutrient concentrations and discharge
- Nitrite plus nitrate
- Total phosphorus
- Ground water
- Nutrients
- Nitrite plus nitrate
- Ammonia
- Ammonia plus organic nitrogen
- Total nitrogen
- Total phosphorus
- Orthophosphate
- Long-term trends
- Surface water
- Nitrogen
- Phosphorus
- Suspended sediment and suspended solids
- Ground water
- Surface-water loads
- Summary
- Selected references
FIGURES
- Location of Ozark Plateaus study unit, major river basins, physiograhic areas, and hydrogeologic units
- Municipal sewage-treatment plant point-source discharges greater than 0.5 million gallons per day
- Location of selected surface-water sites with nutrient and suspended-sediment data
- Bar graphs showing monthly distribution of samples collected and analyzed for nitrite plus nitrate at selected surface-water sites for water years 1980-90
- Bar graphs showing number of samples for total phosphorus within deciles of daily mean discharge for water years 1980-90
- Map showing location of wells used in data analysis
- Map showing location of springs used in data analysis
- Bar graphs showing number of ground-water samples, by land use and site type, used in data analysis
- Bar graphs showing number of ground-water samples by confined and unconfined aquifers and temporal distribution
- Statistical distribution of well depth
- Statistical distribution of nitrite plus nitrate concentrations at surface-water sites for water years 1980-90
- Statistical distribution of ammonia concentrations at surface-water sites for water years 1980-90
- Statistical distribution of total ammonia plus organic nitrogen concentrations at surface-water sites for water years 1980-90
- Statistical distribution for total nitrogen concentrations at surface-water sites for water years 1980-90
- Statistical distribution for total phosphorus concentrations at surface-water sites for water years 1980-90
- Statistical distribution of orthophosphate concentrations at surface-water sites for water years 1980-90
- Statistical distribution of suspended-solids concentrations at surface-water sites for water years 1980-90
- Statistical distribution of nitrite plus nitrate concentrations at surface-water indicator and integrator sites in the Meramec, Osage, and White River Basins for water years 1980-90
- Statistical distribution of total phosphorus concentrations at surface-water indicator and integrator sites in the Meramec, Osage, and White River Basins for water years 1980-90
- Graphs showing relation of nitrite plus nitrate concentration to discharge at selected sites for water years 1980-90
- Graphs showing relation of total phosphorus concentration to discharge at select sites for water years 1980-90
- Statistical distribution of nitrite plus nitrate concentrations in ground water for water years 1970-92
- Statistical distribution of ammonia concentrations in ground water for water years 1970-92
- Statistical distribution of ammonia plus organic nitrogen concentrations in ground water for water years 1970-92
- Statistical distribution of total nitrogen concentrations in ground water for water years 1970-92
- Statistical distribution of total phosphorus concentrations in ground water for water years 1970-92
- Statistical distribution of orthophosphate concentrations in ground water for water years 1970-92
- Concentrations of nitrite plus nitrate for water years 1970-90 at selected surface-water sites
- Concentrations of ammonia for water years 1970-90 at selected surface-water sites
- Concentrations of total ammonia plus organic nitrogen for water years 1970-90 at selected surface-water sites
- Concentrations of total phosphorus for water years 1970-90 at selected surface-water sites
- Concentrations of orthophosphate for water years 1970-90 at selected surface-water sites
- Concentrations of suspended solids for water years 1970-90 at selected surface-water sites
TABLES
- Land-use percentage by physiographic area
- Annual nitrogen and phosphorus fertilizer use by major river basins, 1965 and 1985
- Animal waste nutrient contribution to the Ozark Plateaus study unit
- Major water-quality data sources available for the Ozark Plateaus study unit
- Summary by agency of the number of sites, collection methods, and frequency of water-quality samples used for analysis in this report
- Site and basin characteristics of surface-water sites in the Ozark Plateaus study unit
- Number of ground-water samples, by hydrogeologic unit, used in data analysis
- Statistical summary, by station, of discharge, nutrient, suspended-solids, and suspended-sediment data for surface water in the Ozark Plateaus study unit for water years 1980-90
- Statistical summary, by physiographic area and land use, of nutrient and suspended-solids data for surface water in the Ozark Plateaus study unit for water years 1980-90
- Statistical summary of nutrient data for ground water in the Ozark Plateaus study unit
- Ground-water samples with nitrate concentrations exceeding the maximum contaminant level
- Sites selected for examination of changes in water quality
- Ground-water sites with water-quality samples collected for more than 10 years
- Estimated annual inputs of nitrogen for selected basins
- Estimated annual inputs of phosphorus for selected basins
- Regression models used to estimate daily constituent loads at selected sites
- Estimated total nitrogen, total phosphorus, and suspended-sediment loads and yields at selected sites
- Annual mean streamflow for sites used for load estimation