LIST
OF FIGURES
CHAPTER 1
Figure 1. Location of Clear Lake within Cerro Gordo and Hancock counties and the state of Iowa.
FIGURE 2. Location
of Clear Lake within Cerro Gordo and Hancock counties.
FIGURE 3. Map
of Clear Lake watershed representing prairie and forest derived soils.
FIGURE 4. Distribution of common soil series in the Clear Lake watershed.
FIGURE 5. Distribution
and percentage of soil hydrogroups in the Clear Lake watershed.
FIGURE 9. Willingness
to pay for Plan B, low improvement: visitors.
FIGURE 10. Willingness
to pay for Plan B, low improvement: local residents.
FIGURE 11. Willingness
to pay for Plan B, high improvement: visitors.
FIGURE 12. Number
of trips taken at varying quality levels.
FIGURE 2. Open
water sampling points in Clear Lake, Iowa.
FIGURE 3. Trends
in water temperature in Clear Lake, Iowa during 1998-2000.
FIGURE 4. Trends
in water clarity in Clear Lake, Iowa during 1998-2000.
FIGURE 5. Trends
in oxygen concentrations in Clear Lake, Iowa during 1998-2000.
FIGURE 6. Trends
in alkalinity concentrations in Clear Lake, Iowa during 1998-2000.
FIGURE 7. Trends
in pH of Clear Lake, Iowa during 1998-2000.
FIGURE 8. Trends
in total dissolved solids (TDS) in Clear Lake, Iowa during 1998-2000.
FIGURE 9. Trends
in silica in Clear Lake, Iowa during 1998-2000.
FIGURE 10. Trends
in whole-lake, volume weighted concentrations of silica in Clear Lake, Iowa
during 1998-2000.
FIGURE 11. Comparison of total suspended solids concentrations in Clear Lake with those found in the 2000 Iowa Lake Water Quality Survey (Downing & Ramstack 2001).
FIGURE 12. Trends
in total suspended solids (TSS) in Clear Lake, Iowa during 1998-2000.
FIGURE 13. Volume
weighted trends in suspended solids in Clear Lake, Iowa during 1998-2000.
FIGURE 14. Trends
in inorganic suspended solids (ISS) in Clear Lake, Iowa during 1998-2000.
FIGURE 15. Trends
in volatile suspended solids (VSS) in Clear Lake, Iowa during 1998-2000.
FIGURE 16. Comparison
of total phosphorus concentrations in Clear Lake with those found in the 2000
Iowa Lake Water Quality Survey (Downing & Ramstack 2001).
FIGURE 17. Comparison of total phosphorus and total nitrogen concentrations in Clear Lake with those found in the 1990 (Bachmann et al 1992) and 2000 Iowa Lake Water Quality Surveys (Downing & Ramstack 2001), as well as world lake data (Downing and McCauley 1993).
FIGURE 18. Trends
in total nitrogen in Clear Lake, Iowa during 1998-2000.
FIGURE 19. Trends
in nitrate in Clear Lake, Iowa during 1998-2000.
FIGURE 20. Trends
in ammonia nitrogen in Clear Lake, Iowa during 1998-2000.
FIGURE 21. Trends in volume weighted concentrations of various forms of nitrogen in Clear Lake, Iowa during 1998-2000.
FIGURE 22. Trends
in total phosphorus concentrations in Clear Lake, Iowa during 1998-2000.
FIGURE 23. Trend
in volume weighted concentrations of total phosphorus in Clear Lake, Iowa
during 1998-2000.
FIGURE 24. Trend in the volume weighted ratio of total nitrogen to total phosphorus concentration in Clear Lake, Iowa during 1998-2000.
FIGURE 25. Trends
in the volume weighted chlorophyll a concentrations in Clear Lake, Iowa during
1998-2000.
FIGURE 26. Trends
in percentage taxonomic composition of phytoplankton in Clear Lake, Iowa during
1998-2000 (by biomass).
FIGURE 27. Photograph
of Bacillariophycaea (Melosira sp.) from Clear Lake.
FIGURE 28. Photograph
of Bacillariophycaea (Asterionella sp.) from Clear Lake.
FIGURE 29. Photograph
of Cyanobacteria (Spirulina sp.) from Clear Lake.
FIGURE 30. Photograph
of Cyanobacteria (Oscillatoria sp.) from Clear Lake.
FIGURE 31. Photographs
of Cyanobacteria (Anabaena sp.) from Clear Lake.
FIGURE 32. World
trend in Cyanobacteria abundance as related to the total phosphorus
concentrations in lakes.
FIGURE 33. Secchi
disk measurements and macrophyte abundance in Clear Lake from 1896 to 2000.
FIGURE 34. Clear
Lake bathymetric map, 2000.
FIGURE 35. Clear
Lake bathymetric map, 1935.
FIGURE 36. Clear
Lake bathymetric map, original post-glaciation estimate.
FIGURE 37. Clear
Lake sediment deposition map, 1935-2000.
FIGURE 38. Clear
Lake sediment deposition map, original lake basin estimate-2000.
FIGURE 39. Little
Lake section of Clear Lake sediment deposition map, original lake basin
estimate-2000.
FIGURE 40. Changes
in ambient total phosphorus concentration in Clear Lake predicted from the
Canfield/Bachmann model for various levels of reduction in phosphorus input
from the watershed.
FIGURE 41. Changes
in ambient water clarity in Clear Lake predicted form the Canfield/Bachmann model
for various levels of reduction in phosphorus input from the watershed.
FIGURE 1. Color-coded
bacterial concentrations in storm drains around the City of Clear Lake.
FIGURE 2. Color-coded chemical
concentrations in storm drains around the City of Clear Lake.
FIGURE 3. Spatial patterns of bacterial concentrations in
Clear Lake, Iowa.
FIGURE 4. Spatial
patterns of fecal coliform concentrations in Clear Lake, Iowa across the open
water season of 1999.
FIGURE 5. Spatial
patterns of E. coli bacteria concentrations in Clear Lake, Iowa across
the open water season of 1999.
FIGURE 6. Spatial
patterns of fecal enterococcal bacteria concentrations in Clear Lake, Iowa
across the open water season of 1999.
FIGURE 7. Aggregate patterns of fecal coliforms across the season.
CHAPTER 7
FIGURE 1. Locations of the sonde (·), Clear Lake Municipal Water Treatment Facility (·), and 3700 points used for calculation of physical wave characteristics (·).
FIGURE 2. Turbidity (NTU) (·), chlorophyll a concentrations (mg·L-1) (·), and wind speed (m·s-1) (·) observed at Clear Lake between July 25, 2000 and October 19, 2000.
FIGURE 3. Peaks
and troughs in spectral trends in Turbidity
(NTU) (¾) and wind speed (m·s-1)
(¾), both averaged over one hour intervals, are similar, implying a role
of wind–induced turbulence in sediment resuspension at Clear Lake.
FIGURE 4. Wave
velocities (cm·s-1) at
the lake bottom during a 5m·s-1
wind event along the prevailing Northwest-Southeast (330°-170°) wind axis.
FIGURE 5. Wave
velocities (cm·s-1) at
the lake bottom during a 10m·s-1
wind event along the prevailing Northwest-Southeast (330°-170°) wind axis.
FIGURE 6. Wave
velocities (cm·s-1) at
the lake bottom during a 15m·s-1
wind event along the prevailing Northwest-Southeast (330°-170°) wind axis.
FIGURE 7. Wave
velocities (cm·s-1) at
the lake bottom during a 20m·s-1
wind event along the prevailing Northwest-Southeast (330°-170°) wind axis.
FIGURE 8. Wave
velocities (cm·s-1) at
the lake bottom during a 25m·s-1
wind event along the prevailing Northwest-Southeast (330°-170°) wind axis.
FIGURE 9. Wave
velocities (cm·s-1) at
the lake bottom during 10 m·s-1
and 15 m·s-1 wind
events along a North-South (0°-180°) wind axis.
FIGURE 10. Wave
velocities (cm·s-1) at
the lake bottom during 10 m·s-1
and 15 m·s-1 wind
events along an East-West (270°-90°) wind axis.
FIGURE 11. Wave
velocities (cm·s-1) at
the lake bottom during 10 m·s-1
and 15 m·s-1 wind
events along a Northeast-Southwest (225°-45°) wind axis.
FIGURE 12. Flux
of (a.) turbidity (NTU) (¾), (b.) ammonium (mg·L-1) (¾), and (c.) total phosphorus
(mg·L-1) (¾) during a significant wind
event (10m·s-1) (¾) on September 27,
2000.
FIGURE 14. Trends
in the mean number of boats passing the sonde per 10 minute interval (¾), turbidity (NTU) (¾), and wind speed (10m·s-1) (¾) between August 25, 2000
and September 3, 2000.
FIGURE 1. Private well log downloaded from the IGSB’s Virtual GEOSAM database.
FIGURE 2. Hydraulic heads in major aquifers in relation to Clear Lake stage.
FIGURE 3. Map of Clear Lake watershed showing location of seepage meter measurements in 1999 and 2000. North is to the top of the map. Sections are 1 mi (1.6 km) square.
FIGURE 4. Boxplots
showing seepage measurements at the 21 sites (see Figure 3).
FIGURE 5. Cross-sectional
diagram showing piezometers in a nested configuration.
FIGURE 6. Topographic map showing location of piezometer nests (blue dots) and boundaries of cross-sections (lines) for discharge calculations by Darcy’s Law.
FIGURE 7. Simulation
of groundwater flow in the vicinity of Clear Lake using the AE model
GFLOW2000.
FIGURE 8. Calibration
curve for the AE simulation shown in Figure 7.
FIGURE 9. Boxplots
showing Total P concentrations in groundwater.
FIGURE 10. Boxplots
showing concentrations of Total P at each piezometer. Differences in concentrations exist between piezometers.
FIGURE 11. Vertical
profile of Total P concentration in groundwater at all sites. Highest values occur at shallow depths, but
there is no consistent trend with depth.
FIGURE 12. Variation
of Soil P (Olsen method) with depth in core.
FIGURE 13. Total
N concentrations in groundwater.
FIGURE 14. SiO2
concentrations in groundwater.
FIGURE 15. SiO2
concentrations in groundwater among the piezometers.
FIGURE 16. Relationship
of Na and Cl concentrations (meq/L) in groundwater.
FIGURE 17. Profile
of 3H (TU) in groundwater in the piezometers.
CHAPTER
9
FIGURE 1. Map
of Clear Lake watershed showing land use and the location of Ventura Marsh and
the reference system (Little Lake).
FIGURE 2. Map of Ventura Marsh showing the water quality,
plankton, and benthic sampling sites
FIGURE 3. Inorganic suspended solids and Secchi disc
transparency for Ventura Marsh from April 14, 1999 to September 27, 2000.
FIGURE 4. The
relationship between total phosphorus and phytoplankton biomass was examined.
Figure 4A is of the turbid phase (4/12/99 –6/6/00) and Figure 4B is of the
clear water phase (6/7/00 – 9/27/00).
FIGURE 5. The
relationship between Inorganic suspended solids and Secchi disk transparency
was examined.
FIGURE 6. Phytoplankton
biomass and percent composition for Ventura Marsh from May 13, 1999 to
September 27, 2000.
FIGURE 7. Zooplankton
biomass and percent composition for Ventura Marsh from April 12, 1999 to
September 27, 2000.
FIGURE 8. Box-whisker
plot of cladoceran and copepod lengths during premanipulation (4/12/99 –
8/16/99), postmanipulation 1 (8/17/99 – 10/15/99), postmanipulation 2 (3/14/99
– 6/6/00), and postmanipulation 3 (6/7/00 – 9/27/00).
FIGURE 9. Grazing
rate and phytoplankton biomass for Ventura Marsh from May 13, 1999 to September
27, 2000.
FIGURE 10. Benthic
biomass and percent composition for Ventura Marsh from April 12, 1999 to
September 27, 2000.
FIGURE 11. Box-whisker
plot of chironomid and oligochaete lengths during premanipulation (4/12/99 –
8/16/99), postmanipulation 1 (8/17/99 – 10/15/99), postmanipulation 2 (3/14/99
– 6/6/00), and postmanipulation 3 (6/7/00 – 9/27/00).
FIGURE 1. Sampling
sites and sub-basins used for modeling purposes in the Clear Lake watershed.
FIGURE 2. Watershed
areas differentiated for nutrient flux calculations in the Clear Lake
watershed.
FIGURE 3. 1998-1999 Total Phosphorus load (kg).
FIGURE 4. 1999-2000
Total Phosphorus load (kg).
FIGURE 5. Average
Total Phosphorus load (kg).
FIGURE 6. Land
uses in the Clear Lake watershed.
FIGURE 7. Present conditions modeling results from AGNPS model for the Clear Lake watershed.
FIGURE 1. Soil
samples taken in Clear Lake watershed summer of 1999.
FIGURE 2. Cropping
and tillage systems in the Clear Lake watershed.
FIGURE 3. Soil
survey of the Clear Lake watershed.
FIGURE 4. Olsen-P
in sub-sections of the Clear Lake watershed.
FIGURE 5. Bray-1
P in sub-sections of the Clear Lake watershed.
FIGURE 6. Mehlich-3
P in sub-sections of the Clear Lake watershed.
FIGURE 7. Iron-oxide
strip P in sub-sections of the Clear Lake watershed.
FIGURE 8. Water
extractable P in sub-sections of the Clear Lake watershed.
FIGURE 9. Soil
pH in sub-sections of the Clear Lake watershed.
FIGURE 1. Present
conditions modeling results from AGNPS model for the Clear Lake watershed.
FIGURE 2. Top
1%, 5%, and 10% of phosphorus exporting cropland cells determined by AGNPS
model.
FIGURE 3. Proposed
wetland restoration and construction in the Clear Lake watershed.
FIGURE 4. Schematic
diagram of nutrient retention wetlands and their nutrient retention rates.
FIGURE 5. Aerial view of Ventura Marsh at the present
time, and a visual representation of it in the future.
FIGURE 7. Wind rose for Clear Lake.
FIGURE 8. Proposed
area of dredging and dredging depths in the Little Lake.
FIGURE 9. Containment
site for dredge spoil.
FIGURE 10. Bathymetric
map of the Clear Lake after dredging.
FIGURE 11. Post
restoration water quality monitoring sites.