Publications—Scientific Investigation Report

Analysis of Ambient Conditions and Simulation of Hydrodynamics and Water-Quality Characteristics in Beaver Lake, Arkansas, 2001 through 2003

By Joel M. Galloway and W. Reed Green

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Abstract

Beaver Lake is a large, deep-storage reservoir located in the upper White River Basin in northwestern Arkansas. The purpose of this report is to describe the ambient hydrologic and water-quality conditions in Beaver Lake and its inflows and describe a two-dimensional model developed to simulate the hydrodynamics and water quality of Beaver Lake from 2001 through 2003.

Water-quality samples were collected at the three main inflows to Beaver Lake; the White River near Fayetteville, Richland Creek at Goshen, and War Eagle Creek near Hindsville. Nutrient concentrations varied among the tributaries because of land use and contributions of nutrients from point sources. The median concentrations of total ammonia plus organic nitrogen were greater for the White River than Richland and War Eagle Creeks. The greatest concentrations of nitrite plus nitrate and total nitrogen, however, were observed at War Eagle Creek. Phosphorus concentrations were relatively low, with orthophosphorus and dissolved phosphorus concentrations mostly below the laboratory reporting limit at the three sites. War Eagle Creek had significantly greater median orthophosphorus and total phosphorus concentrations than the White River and Richland Creek. Dissolved organic-carbon concentrations were significantly greater at the White River than at War Eagle and Richland Creeks. The White River also had significantly greater turbidity than War Eagle Creek and Richland Creek.

The temperature distribution in Beaver Lake exhibits the typical seasonal cycle of lakes and reservoirs located within similar latitudes. Beaver Lake is a monomictic system, in which thermal stratification occurs annually during the summer and fall and complete mixing occurs in the winter. Isothermal conditions exist throughout the winter and early spring.

Nitrogen concentrations varied temporally, longitudinally, and vertically in Beaver Lake for 2001 through 2003. Nitrite plus nitrate concentrations generally decreased from the upstream portion of Beaver Lake to the downstream portion and generally were greater in the hypolimnion. Total ammonia plus organic nitrogen concentrations also decreased from the upstream end of Beaver Lake to the downstream end and were substantially greater in the hypolimnion of Beaver Lake. Phosphorus concentrations mostly were near or below laboratory detection limits in the epilimnion and metalimnion in Beaver Lake and were substantially greater in the hypolimnion in the upstream and middle parts of the reservoir. Measured total and dissolved organic carbon in Beaver Lake was relatively uniform spatially, longitudinally, and vertically in the reservoir from January 2001 through December 2003. Chlorophyll a concentrations measured at sites in the upstream portion of the lake were significantly greater than at the other sites in the downstream portion of Beaver Lake.

During the study period, water clarity in Beaver Lake was significantly greater at the downstream end of the reservoir than at the upstream end. The greatest Secchi depths at the downstream end of the reservoir generally were observed in 2001 compared to 2002 and 2003, but did not have a seasonal pattern as observed at sites in the middle and upstream portion of the reservoir. Similar to Secchi depth results, turbidity results indicated greater water clarity in the downstream portion of Beaver Lake compared to the upstream portion. Turbidity also was greater in the hypolimnion than in the epilimnion in the reservoir during the stratification season.

A two-dimensional, laterally averaged, hydrodynamic, and water-quality model using CE-QUAL-W2 Version 3.1 was developed for Beaver Lake and calibrated based on vertical profiles of temperature and dissolved oxygen, and water-quality constituent concentrations collected at various depths at four sites in the reservoir from April 2001 to April 2003. Simulated temperatures and dissolved-oxygen concentrations compared reasonably well with measured temperatures and dissolved-oxygen concentrations and differences varied spatially in Beaver Lake for April 2001 to April 2003. The greatest differences between measured and simulated temperature data occurred in the upstream portion of the reservoir, which is the most dynamic part of the reservoir. In general, the differences between measured and simulated temperature were the least in 2001 at the two upstream sites and in 2002 at the two downstream sites, and greatest in 2003 for all four sites. Similar to temperature, differences between simulated and measured values of dissolved-oxygen concentrations were greater in the upstream portion of the reservoir compared to differences in the downstream portion. At the upstream portion of the reservoir, the greatest differences between simulated and measured dissolved oxygen generally occurred in 2002 and the least differences occurred in 2003. Simulated ammonia and total nitrogen concentrations in Beaver Lake compared relatively well with the measured concentrations and simulated nitrite plus nitrate concentrations generally were less then the measured concentrations. Simulated values for orthophosphorus were comparable to measured concentrations and simulated total phosphorus concentrations generally were greater than the measured concentrations in Beaver Lake. Simulated chlorophyll a values were comparable to measured chlorophyll a values both spatially and temporally in Beaver Lake.


TABLE OF CONTENTS

Figures
  1. Map showing Beaver Lake study area, Arkansas, with locations of data-collection sites
  2. Graphs showing daily inflow and hourly outflow for Beaver Lake, Arkansas, January 2001 through December 2003
  3. Graph showing daily reservoir water-surface elevation near Beaver Lake dam, January 2001 through December 200
  4. Boxplots showing distribution of nutrients, dissolved organic-carbon, and suspended-sediment concentrations for the White River near Fayetteville, Richland Creek at Goshen, and War Eagle Creek near Hindsville, 2001-2003
  5. Graphs showing time series of nutrients, dissolved organic-carbon, and suspended-sediment concentrations for the White River near Fayetteville, Richland Creek at Goshen, and War Eagle Creek near Hindsville, 2001-2003
  6. Graphs showing annual nutrient and organic-carbon loads computed for the White River near Fayetteville, Richland Creek at Goshen, and War Eagle Creek near Hindsville, 2001-2003
  7. Boxplot and graph showing distribution and time series of turbidity for the White River near Fayetteville, Richland Creek at Goshen, and War Eagle Creek near Hindsville, 2001-2003
  8. Graphs showing distribution of temperature and dissolved-oxygen concentration at sites L2 and L5 in Beaver Lake, 2001-2002
  9. Graphs showing distribution of temperature and dissolved-oxygen concentration in Beaver Lake on February 6, 2002 and August 22, 2002
  10. Boxplots showing distribution of nitrogen concentrations for five sites in Beaver Lake, 2001-2003
  11. Graphs showing time series of nitrogen concentrations for five sites in Beaver Lake, 2001-2003
  12. Boxplots showing distribution of phosphorus concentrations for five sites in Beaver Lake, 2001-2003
  13. Graphs showing time series of phosphorus concentrations for five sites in Beaver Lake, 2001-2003
  14. Boxplots showing distribution of organic-carbon concentrations for five sites in Beaver Lake, 2001-2003
  15. Graphs showing time series of organic-carbon concentrations for five sites in Beaver Lake, 2001-2003
  16. Boxplot showing distribution of chlorophyll a concentrations for five sites in Beaver Lake, 2001-2003
  17. Graph showing time series of chlorophyll a concentrations for five sites in Beaver Lake, 2001-2003
  18. Graph showing distribution of phytoplankton and time series of chlorophyll a concentrations for five sites in Beaver Lake, 2001-2002
  19. Boxplot showing distribution of Secchi depth for five sites in Beaver Lake, 2001-2003
  20. Graph showing time series of Secchi depth for five sites in Beaver Lake, 2001-2003
  21. Boxplot showing distribution of turbidity for five sites in Beaver Lake, 2001-2003
  22. Graph showing time series of turbidity for five sites in Beaver Lake, 2001-2003
  23. Plot showing side view, top view, and face view from the dam of the computational grid of Beaver Lake used in the CE-QUAL-W2 model
  24. Simulated and measured water-surface elevations near Beaver Lake dam, April 2001 to April 2003
  25. Selected simulated and measured water-temperature profiles for Beaver Lake at Highway 412 bridge near Sonora, Arkansas, April 2001 to April 2003
  26. Selected simulated and measured water-temperature profiles for Beaver Lake near Lowell, Arkansas, April 2001 to April 2003
  27. Selected simulated and measured water-temperature profiles for Beaver Lake at Highway 12 bridge near Rogers, Arkansas, April 2001 to April 2003
  28. Selected simulated and measured water-temperature profiles for Beaver Lake near Eureka Springs, Arkansas, April 2001 to April 2003
  29. Selected simulated and measured dissolved-oxygen concentration profiles for Beaver Lake at Highway 412 bridge near Sonora, Arkansas, April 2001 to April 2003
  30. Selected simulated and measured dissolved-oxygen concentration profiles for Beaver Lake near Lowell, Arkansas, April 2001 to April 2003
  31. Selected simulated and measured dissolved-oxygen concentration profiles for Beaver Lake at Highway 12 bridge near Rogers, Arkansas, April 2001 to April 2003
  32. Selected simulated and measured dissolved-oxygen concentration profiles for Beaver Lake near Eureka Springs, Arkansas, April 2001 to April 2003
  33. Simulated and measured ammonia concentrations for Beaver Lake, Arkansas, April 2001 to April 2003
  34. Simulated and measured nitrite plus nitrate concentrations for Beaver Lake, Arkansas, April 2001 to April 2003
  35. Simulated and measured total nitrogen concentrations for Beaver Lake, Arkansas, April 2001 to April 2003
  36. Simulated and measured orthophosphorus concentrations for Beaver Lake, Arkansas, April 2001 to April 2003
  37. Simulated and measured total phosphorus concentrations for Beaver Lake, Arkansas, April 2001 to April 2003
  38. Simulated and measured chlorophyll a concentrations for Beaver Lake, Arkansas, April 2001 to April 2003
  39. Simulated phytoplankton distribution for Beaver Lake, Arkansas, April 2001 to April 2003
Tables
  1. Water-quality and streamflow sites for Beaver Lake, Arkansas
  2. Parameters and values used for the Beaver Lake model, April 2001 to April 2003
  3. Comparative statistics of simulated and measured temperature and dissolved-oxygen concentration for Beaver Lake, April 2001 to April 2003
  4. Comparative statistics of simulated and measured nutrient concentrations for Beaver Lake, April 2001 to April 2003
  5. Comparative statistics of simulated and measured chlorophyll a concentrations for Beaver Lake, April 2001 to April 2003
  6. Results of sensitivity analysis for the Beaver Lake model, April 2001 to April 2003, showing the mean difference of all computed values at five sites in Beaver Lake compared to calibrated values


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