HYDRODYNAMIC SIMULATIONS OF RESTORATION ALTERNATIVE 1 TENOROC FISH MANAGEMENT AREA Mark Schwartz, Les Bromwell, John Kiefer, Walt Reigner, Wink Winkler, and Brian Manley, BCI Engineers & Scientists, Inc., Lakeland Florida. Paper prepared for Stormwater Management Conference, Orlando, Florida, December 4-6, 2002. Abstract: A primary objective of the Upper Peace River restoration project is to create wetlands as compensation for wetlands impacted during construction of the Polk County Parkway (S.R. 570). The Tenoroc Fish Management Area (TFMA) will be the site of extensive wetland creation and enhancement, consisting of at least 85 acres of forested wetlands and 37 acres of herbaceous wetlands. An integral part of wetland creation and enhancement is to provide the hydrology necessary to maintain wetland health and propagation. Methods for providing sufficient or appropriate wetland hydrology include: improving water flow patterns and connections between wetlands, management of wetland surface water inflows and outflows, and adjusting topographic surface elevations, especially in relation to water table elevations and surface water basin configurations. Several alternatives for the location of created wetlands and modifications of interconnections between wetlands and lakes will be evaluated as part of the TFMA restoration project. This report describes the first of these alternatives and results of simulations to estimate off-site discharges, and water level fluctuations within wetlands and lakes. In general, the first alternative potentially increases runoff detention and diverts flows from the west to the east side of the project area.

ACKNOWLEGEMENTS

The authors would like to thank Matt Terella, and Vicki Bucy of BCI for preparation of the graphics used in this presentation.

INTRODUCTION

For many situations it is important to consider the interactions between surface water bodies (such as wetlands and lakes) and the underlying ground water system when trying to estimate potential impacts of development, and options for ecosystem protection or restoration. This is especially true in Florida where the water table is often within a few feet of land surface, affecting fluctuations in surface water bodies and their associated biological systems. Beginning in 1989, the Florida Institute of Phosphate Research (FIPR) sponsored the development of an integrated surface and ground water model for use in quantifying potential hydrologic impacts of phosphate mining in central Florida. The FIPR Hydrologic Model (FHM, Ref. 1), developed as part of this effort, has gone through many changes since the FIPR sponsored project ended in 1991, including the development of the Integrated Surface and Ground Water model (ISGW, Ref. 2). Previously developed models based on the original FIPR project used MODFLOW (Ref. 3) to represent the ground water system and HSPF (Ref. 4) to represent the surface water

system. FHM and ISGW overcome a major limitation of previous models such as SWMM (Ref. 5) and HPSF by representing the ground water system with more detail, including ground water flow into and out of surface water bodies (reaches).

BCIFLO96, makes a significant departure from the previously developed integrated

models. BCIFLO96 uses separate modules within MODFLOW to calculate surface water runoff, evapotranspiration (ET), and recharge to the saturated ground water system. That is, BCIFLO96 does not use HSPF, providing a more integrated representation of the surface and ground water systems than provided by either FHM or ISGW. In addition, BCIFLO96 includes hydraulic calculations based on the one-dimensional St. Venant’s equations that overcome potentially significant shortcomings of FHM and ISGW. These shortcomings include linear routing between water bodies within HSPF that may not account for downstream water levels, particularly as they change with upland hydrologic response resulting from design modifications.

Restoration alternatives are being evaluated for the TFMA to select the most appropriate

concept for restoration and mitigation planning. Evaluations are based on criteria established by a Selection Committee composed of representatives of the Florida Department of Environmental Protection (FDEP), Southwest Florida Water Management District (SWFWMD), and the US Army Corps of Engineers (USACOE). The FDEP is designated as the lead agency.

Among the evaluation criteria are the restoration of historic flows to Upper Saddle Creek,

the impacts of flow-through quantities on TFMA lakes, and the establishment of suitable wetland hydrology. In order to quantify the hydrologic impacts of various restoration alternatives, hydrologic simulations are being made to estimate:

• Water level fluctuations within enhanced and created wetlands, • Potential changes in hydrology of other wetlands within the project area, and • Potential changes in downstream discharges (flow and volume) in response to long-

term and extreme short duration rainfall events.

This report provides a description of these model simulations and their results for Alternative-1 (A-1). Each of the alternatives includes a description of created wetland locations, changes in surface water routing directions, and changes in topography. Changes associated with A-1 are summarized in this report and compared to conditions that existed in 1997. In general, A-1 is an alternative that potentially increases runoff detention and diverts flows from the west to the east side of the project area.

SITE DESCRIPTION Figure 1 shows the portion of the Upper Peace River basin included in the model representation and described in this report. Also shown in Figure 1 are the locations of nearby rain gages and pan evaporation instruments. The project area (i.e., Upper Saddle Creek Basin) represented in this numerical model investigation of surface and near surface hydrology is that part of the Upper Peace River Basin upstream of C.R. 546. This 24.4 square mile area includes the old mine lands of the Upper Saddle Creek Basin and more recent mined areas of Bridgewater and Williams. Discharge from

the Upper Saddle Creek Basin enters Saddle Creek and flows to Lake Hancock within the Upper Peace River Basin. Topographic surface elevations within the area range between 110 and 190 feet National Vertical Geodetic Datum (ft. NGVD). The phosphate ore (matrix) removed during mining is generally found at the top of the confining unit between the Surficial and Intermediate Aquifers. During mining, the surficial sands or overburden are removed and stacked in rows so that the phosphate ore can be accessed. This usually creates areas of long interconnected lakes. During beneficiation of the phosphate ore, the clays and sands (sand tailings) are separated from the phosphate particles. The clays are pumped back to impounded areas to settle out and consolidate. These clay settling areas (CSAs) have greater retention capacity and lower deep percolation rates than most natural systems. During mining within the Upper Saddle Creek Basin, these clays were generally deposited into previously mined areas, but in some cases impoundments were built around unmined areas. The sand tailings are generally a little coarser, and are more uniform in size, with higher permeability and infiltration rates than most natural soils. Figure 2 shows the location of the mined soils within the Upper Saddle Creek Basin.

The Upper Saddle Creek Basin is located within the Polk Uplands physiographic province between the Lakeland Ridge and the Winter Haven Ridge (Ref. 6). The topographic relief of the site is highly variable, ranging from relatively flat to gently undulating on some of the unmined areas, reclaimed mine sites and old clay settling areas (CSAs), to steeply sloping in areas of remnant overburden spoil piles and CSA embankments. The highest elevations (approximately 190 feet, referenced to the National Geodetic Vertical Datum [NGVD] of 1929) lie on some of the unmined areas in the extreme eastern portion of the site, and the lowest elevations (approximately 110 feet NGVD) are found in the south central portion of the property, near the headwaters of Upper Saddle Creek.

Peninsular Florida is underlain by a thick sequence of carbonate rocks capped by a thin

series of siliciclastic rocks that range from mid-Mesozoic to Recent in age (Ref. 7). The aquifer systems of Florida are found within the rocks deposited in the earliest Tertiary (55 million years ago) to Recent Ages (<100,000 years ago). In west-central Florida, the most prominent structural feature is the Ocala Platform. The Ocala Platform was a positive feature during the Miocene Age. The Ocala limestone comprises the youngest geologic unit present on the crest of the Ocala Platform (east of the project area), and is of Late Eocene Age. It is believed that Hawthorn Group sediments (of Miocene Age) have been removed from the crest of the platform through erosion. In west central Florida, rocks of Eocene Age generally dip to the south, away from the Ocala Platform. Miocene Age rocks follow this trend and thicken appreciably to the south, toward the Okeechobee basin. Rocks of the Late Eocene (40 million years old) to Recent Ages outcrop in Polk County. The significant stratigraphic and hydrogeologic units of west-central Florida are summarized in Table 1.

Table 1 Stratigraphic and Hydrogeologic Units

Underlying the Upper Saddle Creek Basin

Age Stratigraphic Nomenclature

Hydrogeologic Unit (Aquifer)

Approximate Thickness

(feet) Undifferentiated Recent to Pleistocene

Recent to Deposits and the upper portion Pleistocene of the Peace River Formation

(Bone Valley Member)

Surficial 60

Hawthorn Group (includes the Bone Valley Member

Miocene of the Peace River Formation, Intermediate 75 and the Arcadia Formation (including the Tampa Member)

Oligocene Suwannee Limestone 75 - 150 Eocene Ocala Limestone Floridan >200

A description of these units can be found in (Refs. 7, 8, 9, and 10).

Three principle hydrogeologic units are present in west-central Florida (Table 1): the Surficial Aquifer system; the Intermediate Aquifer System, and the Floridan aquifer system. The Surficial Aquifer is found primarily in permeable sand units of the undifferentiated surficial sediments, and in upper portions of the Peace River Formation (the Bone Valley Member). The Intermediate Aquifer System is present in the dolomite and limestone units of the lower portion of the Bone Valley Member and the Arcadia Formation. The Intermediate Aquifer System is equivalent to the secondary artesian aquifer of Stewart (Ref. 11). A lower clay-confining unit (the Tampa Member) occurs at the base of the Arcadia Formation. The Floridan Aquifer is encountered in the underlying Suwannee and Ocala Limestones.

PREVIOUS INVESTIGATIONS

The model representations of Upper Saddle Creek used in this investigation are in part based on model representations used in a previous investigation. A representation of the Upper Saddle Creek basin area using BCIFLO96 was previously calibrated to conditions of 1997 (Ref. 12) and provides model parameters used in the long-term simulations of this investigation. A SWMM representation of Saddle Creek Basin provided a description of the critical storm duration for defining the floodplain upstream of and including Lake Hancock (Ref. 13). An integrated surface and ground water model representation of Upper Saddle Creek basin previously used to estimate the large area water balance and general conditions of flow through the area (Ref. 14), provided some estimates of aquifer properties used in this model investigation.

BCIFLO96 DESCRIPTION

The model simulations were made using BCIFLO96. BCIFLO96 uses the one-

dimensional St. Venant's equations as represented in EXTRAN (Ref. 15) to simulate flow through water bodies and channels. This differs from the FIPR Hydrologic Model (FHM) of the Upper Saddle Creek (Ref. 14), which uses linear routing without backwater affects in simulating channel and water body flow. One of the primary reasons for selecting BCIFLO96 over FHM for use in this project is that the hydrodynamic flow calculations make it more useful for estimating changes in flows with changes in control structures and channel geometries.

BCIFLO96 divides a subbasin into model grid cells with rainfall, evapotranspiration,

infiltration, percolation, and ground water flow calculated for each cell. In addition, BCIFLO96 provides a detailed representation of the ground water system that is sometimes needed to better represent long-term simulations of a system.

Runoff is calculated in BCIFLO96 using the estimated depth of water above land surface

within each model cell. The rate of flow is calculated using a wide channel approximation of the Manning's Runoff Equation (Ref. 16). The flow rate is used to estimate the portion of the basin length that the runoff travels across in a time step. Since not all model cells may have a runoff depth greater than zero, the area of the basin used in the runoff calculations can be less than the total basin area. In BCIFLO96, basin numbers are identified for each model cell, resulting in a discrete approximation of the basin area for each model time step.

MODEL CONCEPTUALIZATION

Using BCIFLO96, the unsaturated zone below land surface and above the water table is

represented as a single homogeneous layer. The thickness of the unsaturated zone changes with water table elevation fluctuations. Water bodies such as lakes and wetlands are represented as storage junctions in the model. Water from storage junctions can flow into the unsaturated ground water system when the water table is below the bottom of the water body. When the water table is above the bottom of the water body, flow between the water body and the saturated ground water zone is calculated (i.e., ground water can flow to and from water bodies).

The EXTRAN module of BCIFLO96 allows easy representation of interconnected hydraulic features. Structures (e.g., culverts and weirs) are explicitly described in the input files of the EXTRAN module. Natural and man-made channels within the model area were represented as trapezoidal channels in this investigation. The lakes and water bodies across the project area were represented to calculate flow interactions between the water bodies and the ground water system.

The BCIFLO96 representation of the site was used to estimate changes in water level

fluctuations associated with proposed wetland creation and enhancements. For this analysis, a simplified representation of the underlying confined aquifer systems was used. The Upper Floridan Aquifer System (UFAS) was represented as a single constant head layer in the model. This will allow a comparison of flows and water level fluctuations simulated for various scenarios of proposed wetland creation and enhancement. Leakance to the UFAS is estimated to

be low, less than 2-inches/year (Ref. 12 and 14); which further allows some simplifications in the model representation to meet proposed model objectives.

MODEL SETUP

Basins were delineated based on topographic maps, water bodies and, hydrologic control

structures. Basins were also selected to better simulate the hydrology of created and enhanced wetlands and water bodies. Figure 3 shows the location of proposed areas for wetland creation and enhancement and 70 basins used to represent conditions of A-1. Figure 4 shows the divides for the 76 basins used to represent conditions of 1997. Also shown in Figures 3 and 4 are flow routing directions for the two scenarios.

Topographic elevations with a resolution of one-foot were obtained as part of the ongoing

restoration investigation. U.S. Geological Survey topographic data on 5-foot contours were used outside the Upper Saddle Creek Basin in setting up the model. The basin delineations and topographic data were used to estimate hydraulic lengths and slopes within the basin. The hydraulic length is the distance along a flow path from an upper-most upland point to a downstream point, generally at the outfall or water body within the basin boundaries. Hydraulic slopes were estimated along the path of a measured hydraulic length. BCIFLO96 requires estimates of the basin width in its calculations of runoff. The estimated basin width was calculated by dividing the area of the basin, excluding lakes, by the hydraulic length of the basin. Soils and landuse descriptions were used to define model parameters. The soils for 1997 conditions and A-1 are assumed to be the same (Figure 2). Figure 5 provides an illustration of landuse descriptions across the project area for 1997 conditions. Some modifications of landuse were made for conditions of A-1 reflecting development within the Bridgewater and Williams properties and changes related to created wetlands. The thickness of the surficial aquifer is calculated using elevations for the bottom of the surficial aquifer, which were taken from a previous model investigation (Ref. 14).

In general, each of the upland areas of a basin contributes runoff to a wetland or lake that discharges out of the basin through some form of control structure to a downstream channel and/or interconnected lake system. Wetlands and lakes are represented as junctions in EXTRAN. The stage area relationship for these water bodies was estimated from available topographic data.

Table 2 lists BCIFLO96 model parameters associated with soils. Table 3 lists

BCIFLO96 model parameters associated with landuse. These parameters are estimated for each model grid (Figure 6), weighted by the area of the soil or landuse polygon within the cell. Arcview, along with the Spatial Analyst Extension, was used to calculate model parameters weighted relative to the areas of like thematic character (i.e., zones of specific landuse, soils, etc.) within the model grid. Model parameters selected for representing uplands around lakes were calculated by removing the lake area from the area-weighted average computations.

The BCIFLO96 simulations used a one year period of rainfall and ET conditions observed in 1997 (Figure 7). This period of relatively high rainfall (i.e., 55.4 inches/year)

Table 2 BCILO96 Model Parameters Associated with Soils

Soil Description Hydraulic

Conductivity (ft/day)

Specific Yield1

Field

Capacity1

Porosity1

Infiltration Rate

(inches/hour)

Wilting Point1

Sand-A 10.0 0.10 0.33 0.43 10.0 0.03 Sand-B 2.9 0.10 0.30 0.40 8.0 0.03 Sand-C 2.9 0.10 0.30 0.40 6.0 0.03 Sand-D 1.0 0.10 0.30 0.40 5.0 0.03 Muck 0.1 0.20 0.30 0.40 0.1 0.26 Clay/Sand 2.0 0.10 0.45 0.55 10.0 0.15 Clay 0.1 0.10 0.45 0.55 10.0 0.15 Overburden 1.4 0.15 0.35 0.50 5.0 0.03 Tailings 29.0 0.10 0.26 0.36 20.0 0.03 Water 100.0 1.00 0.00 1.00 1.00 0.00

1A portion of the soil total bulk volume

Table 3 BCIFLO96 Model Parameters Associated with Land Use

DESCRIPTION LEVEL2 FLUCCS

Depression Storage (inches)

Manning's Roughness

RHIZOSPHERE DEPTH (feet)

ET COEFFICIENT

Residential Low Density 1100 0.30 0.13 2.0 0.90 Residential Medium 1200 0.20 0.11 2.0 0.90 Residential High 1300 0.10 0.05 2.0 0.90 Commercial & Services 1400 0.10 0.05 2.0 0.90 Industrial 1500 0.10 0.05 2.0 0.90 Extractive 1600 0.10 0.13 2.0 0.90 Institutional 1700 0.10 0.13 2.0 0.90 Recreation 1800 0.10 0.13 2.0 0.90 Open land 1900 0.10 0.13 2.0 0.90 Cropland & Pasture 2100 0.10 0.08 1.5 0.90 Tree Crops 2200 0.30 0.20 2.0 0.90 Feeding Operations 2300 0.30 0.01 1.5 0.90 Nurseries & Vineyards 2400 0.30 0.20 2.0 0.90 Specialty Farms 2500 0.30 0.01 1.5 0.09 Other Open Rural Land 2600 0.10 0.08 1.5 0.09 Herbaceous Range Land 3100 0.10 0.13 2.0 0.09 Shrub & Brushland 3200 0.10 0.13 2.0 0.90 Upland Conifer Forest 4100 0.35 0.45 6.0 0.90 Upland Hardwood Forest 4200 0.35 0.45 6.0 0.90 Upland Hardwood Forest 4300 0.30 0.45 6.0 0.90 Streams & Waterways 5100 6.00 0.00 0.0 1.00 Lakes 5200 6.00 0.00 0.0 1.00 Reservoirs 5300 6.00 0.00 0.0 1.00 Wetland Hardw. Forest 6100 6.00 0.45 2.0 0.90 Wetland Conif. Forest 6200 6.00 0.35 2.0 0.90 Wetland Forested Mix 6300 6.00 0.30 2.0 0.90 Veg. Non-forested Wetl. 6400 6.00 0.06 1.5 0.90 Non-Vegetated Wetland 6500 6.00 0.06 0.5 0.90 Disturbed lands 7400 0.10 0.13 2.0 0.90 Transportation 8100 0.40 0.01 0.0 0.90 Utilities 8300 0.40 0.01 0.0 0.90

started with drought conditions and ended with high rainfall near the end of the year. These starting conditions include ground water levels, downstream boundary conditions for overland flow, and water levels in junctions.

Juan Carriso of Keith & Schnars, Inc., working with Polk County to develop maintenance related needs along Saddle Creek, indicated that the critical storm event (i.e., the one that causes highest water levels and having a return period of 100 years) has a duration of 5-days (personal communication). The rainfall depth associated with this storm event is 16 inches.

Simulated discharge is sensitive to the starting water level and antecedent moisture conditions of the model. The starting water levels for the large-event simulations were obtained from the quasi-steady-state simulations of 1997 conditions using BCIFLO96. A quasi-steady-state simulation has little or no net change in storage, however it simulates water level flows and fluctuations driven by rainfall and pan evaporation data that were recorded for some period of time (a year in this case). The final quasi-steady-state simulations were obtained by restarting the annual simulations with water levels at the end of the previous annual simulation. This process was repeated until the net change in water storage was small (i.e., < 0.1 inches/year).

The total rainfall during 1997 is 55.4 inches with the quasi-steady-state simulation results

representing above average water levels within the water bodies of the model. Using a quasi-steady-state approach, the starting water levels and soil moisture conditions are not the same for 1997 conditions and A-1 conditions. Though the simulations use the same antecedent weather history of rainfall and pan evaporation, the systems represented in the two simulations do not arrive at the same ground water and water body states (i.e., antecedent moisture conditions).

MODEL LIMITATIONS

The unsaturated zone in BCIFLO96 is represented as one layer of variable thickness

between land surface and the water table. This representation does not simulate variations in saturation across the unsaturated zone. In addition, the model does not represent variations in root density with depth, and assumes that all water above the wilting point and within the rhizosphere is available for ET.

The model simulations made in this investigation are based on the best available data at

the time. However, the plans for development within the Williams property north of Tenoroc were not complete at the time of this report. Similarly, construction within the Bridgewater property northwest of Tenoroc had not been completed. In addition, the floodplain investigation of Upper Saddle Creek conducted by SWFWMD and Keith & Schnars Inc., (Ref. 13) has not been finalized. Changes in the findings from the floodplain study could affect the selection of a critical storm used in this investigation.

MODEL RESULTS

Figure 8 shows the simulated quasi-steady-state discharge from the Upper Saddle Creek

Basin for rainfall and ET conditions of 1997. Table 4 lists the water balance simulated for the quasi-steady-state simulations for A-1 and 1997 conditions. Under the conditions modeled, there

is no net change in water storage and all ground water baseflow and upland runoff will exit the project area (i.e., the volume of rainfall that falls on the project area equals the total volume of water leaving the project area during the period simulated). The model simulation indicates that there will be little or no change in the annual volume of flow from the Upper Saddle Creek Basin under A-1 conditions, compared to 1997 conditions. However, baseflow will increase by an amount similar to a reduction in overland flow. Under A-1 conditions there is a slight decrease in deep aquifer recharge caused by increased ET over areas of created wetlands, and decreased infiltration over areas of development (i.e., proposed development in Bridgewater and Williams).

Table 4

Simulated Water Budget for Weather Conditions of 1997

Component 1997 Conditions

(inches/year) Alternative-1 Conditions

(inches/year)

Rainfall

55.41

55.41 Evapotranspiration -33.28 -33.92 Overland Runoff -16.25 -14.53

Ground Water Baseflow -4.58 -5.86 Deep Aquifer Recharge -1.22 -1.10

Change in Storage -0.08 0.00 Sum 0.00 0.00

Remaining, Percent 0.00 0.00 Combined Runoff & Ground

Water Baseflow

-20.83

-20.39

Figures 9 provide a comparison of simulated water level fluctuations within Derby Lake. Under A-1 conditions, the simulated water levels of the large lakes in the southeast section of the Upper Saddle Creek Basin are higher than simulated water levels of these lakes under conditions of 1997. This is caused by routing a greater portion of flow into CSA-4W (i.e, model basin number 29), through an 18” CMP to Lake-10 (i.e., model junction number 73). Under 1997 conditions, a large portion of the total discharge from the Upper Saddle Creek Basin was routed over a weir northwest of (and bypassing) Lake-10. The net effect of these changes is to detain water for longer periods under A-1 conditions.

Figure 10 provides a comparison (i.e., 1997 conditions and A-1 conditions) of simulated discharges from the Upper Saddle Creek Basin for a 100-year/5-day storm event of 16.5 inches. The starting conditions for simulations of A-1 and 1997 conditions are not the same. However, they represent responses to the same antecedent conditions of rainfall and evapotranspiration. Examining Figure 8, it is apparent that the discharge at the end of quasi-steady-state conditions is greater for 1997 conditions than for A-1conditions. The decreased discharge for A-1 is not caused by lower water levels in lakes as illustrated in Figure 9. Rather, the decreased discharge is caused by relatively lower ground water moisture conditions at the start of the simulations for A-1 conditions as compared to the simulations of 1997 conditions. This is also apparent from

Table 5. For the simulation of 1997 conditions, the ground water system provides 3.64 inches of water that discharges from the site, while under A-1 conditions only 2.61 inches of the discharge are derived from ground water.

Table 5 Simulated Water Budget

for 100year/5-Day Event Storm

Component 1997 Conditions (inches/year)

Alternative-1 Conditions (inches/year)

Rainfall

16.11

16.11

Evapotranspiration -5.30 -5.32 Overland Runoff -12.47 -11.57

Ground Water Baseflow -1.76 -1.62 Deep Aquifer Recharge -0.22 -0.20

Change in Storage 3.64 2.61 Sum 0.00 0.01

Remaining, Percent 0.00 0.06 Combined Runoff & Ground

Water Baseflow

-14.23

-13.19

The peak discharge for the 100-year/5-day rainstorm simulated for A-1 conditions is within 0.7 percent of that simulated for 1997 conditions. Examination of Figure 6 indicates that there may be conditions for which the peak discharge for large rain events is lower for A-1 conditions than for 1997 conditions.

CONCLUSIONS

Water depths and water level fluctuations are important in determining the type and plant

species makeup of created and enhanced wetlands. Figures 11 and 12 provide an illustration of hydrologic zones and plant species composition for two types of wetlands: herbaceous and forested. Herbaceous wetland systems will generally have higher average water depths than forested wetland systems as proposed for this project. For both wetland types, there will probably be greater plant species diversity with annual water level fluctuations of 2 to 3 feet than for annual water level fluctuations of only 6 inches. This is in part due to greater overlap in the location of the plant zones described in Figures 11 and 12, for greater water level fluctuations.

The model simulation results provided in this report will be used in part to guide wetland

creation and enhancement. Figure 13 shows simulated water level fluctuations in the area of one of the created wetland areas, which is adjacent to Picnic Lake. Also shown on this figure are suggested wetland bottom elevations for the herbaceous and forested wetland types. In general, there are three options available for modifying water levels depths and water level fluctuations within created and enhanced wetlands:

• Selection of the wetland bottom elevation. • Modification of channels and structures controlling flow into the wetland, and • Modification of channels and structures controlling flow out of the wetland.

Other options include methods of reducing or increasing wetland bottom permeabilities, however this option is more difficult to control or predict. The model results will have some deviation from the real wetland systems and the ability to make hydrologic corrections by adjusting hydrologic control structures could be a very important component of successful wetland creation.

To some extent the objectives of this model investigation may be dependent on the annual weather conditions selected. Two questions were stated during initial reviews of this investigation:

1. Would an alternative set of wetland bottom elevations be selected if the simulations used rainfall and ET conditions of years other than 1997?

2. Are there reasonable starting conditions selected for the 5-day event storm that would result in higher peak discharges for A-1 conditions?

To address these questions, simulations of a 20-year (1976 through 1995) period were made. Figure 14 shows simulated water level fluctuations in the area of the same wetland as for Figure 13, (i.e., the wetland adjacent to Picnic Lake). Also shown on this figure are suggested wetland bottom elevations for the herbaceous and forested wetland types. Using results from simulations of a 20-year period, adjustments of 0.5 to 1.0 foot in the suggested wetland bottom elevations for created and enhanced wetlands were made. This suggests that the annual quasi-steady-state simulations may provide less successful predictions for estimating desirable wetland bottom elevations.

The maximum average daily discharges are generally lower under A-1 conditions than the 1997 conditions as shown in Figure 15. In addition, as for the 1997 quasi-steady-state simulations, there is an extended period of discharge after a rain event under A-1 conditions.

An additional set of simulations were made to estimate discharges for conditions similar to that of SCS curve number methods. The results from these simulations (Figure 16) indicate that peak discharges are lower for A-1 conditions when the simulations start with estimated antecedent moisture conditions II. There is greater detention during the rainfall event for A-1 conditions causing lower initial discharges during the rain event, but sustained discharges eventually exceed those simulated for 1997 conditions.

The simulations conducted as part of this investigation indicate that under A-1

conditions, water will be detained by the proposed rerouting and wetlands modifications with increase duration of flows after a rain event. In addition, the peak discharge rates will in general be lower for A-1 conditions. The simulations also provide some estimates of desired wetland bottom elevations useful in the wetland design.

REFERENCES

1. Florida Institute of Phosphate Research (1991), “Documentation of FIPR Hydrologic Model”. FIPR Project No. 88-03-085, Bartow, Florida.

2. Davis, P.R. (1988), “ISGW – the Integrated Surface Water and Groundwater Model

Coupling MODFLOW and HPSF”. Proceedings from MODFLOW 98, Vol. II. Golden, Colorado, October 4-8, 1998, pp. 715-722.

3. McDonald, M.G. and Harbaugh, A. W. (1984), “A Modular Three-Dimensional Finite-

Difference Ground-Water Flow Model”. U.S. Geological Survey. 4. Imhoff, J.C., Kittle, J.L., Jr., Donigian, A.S., Jr., (9184). Hydrologic Simulation Program

– FORTRAN (HSPF): Users Manual for Release 8.0. U.S. Environmental Protection Agency. EPA Document No. 600/3-84-066.

5. Huber, W., Dickinson, R.E., Cunningham, B.A., and Heaney, J.P. (1987), “Storm Water

Management Model User’s Manual, Version 4”. U.S. Environmental Protection Agency. 6. White, W. A. (1970), "The geomorphology of the Florida Peninsula". Florida Bureau of

Geology Bulletin no. 51, 164 p. 7. Scott, T.M. (1992), "A geological overview of Florida". Open File Report No. 50, Florida

Geological Survey, Tallahassee, Florida, 78p. 8. Campbell, K.M. (1986). “The industrial minerals of Florida”. Florida Geol. Surv. Inf.

Circ. 102. 9. Scott, Thomas M. and James Cathcart (1989), “Florida Phosphate Deposits – Field Trip

Guidebook T178, “American Geophysical Union, Washington, D.C., 52p. 10. Scott, T.M. (1988). “The Lithostratigraphy of the Hawthorn Group (Miocene) of

Florida”. Florida Geol. Surv. Bull. 59. 11. Stewart, H., Jr. (1966), "Ground Water Resources of Polk County". Florida Geological

Survey Report of Investigation, Number 44. 170 pp. 12. BCI Engineers & Scientists, Inc., March 2002. Upper Saddle Creek Hydrodynamic

Model, Calibration to Conditions of 1997. Florida Department of Environmental Protection, Tallahassee, FL.

13. Keith & Schnars, Inc. (In preparation). Saddle Creek Watershed Management Program.

Southwest Florida Water Management District. Brooksville, Florida. 14. Tara Patrick, Ken Trout, Jeffrey Vomacka, Mark Ross, and Mark Stewart (2000).

“Hydrologic Investigation of the Phosphate Mined Upper Saddle Creek Watershed,

Figure 7. Observed Rainfall and Pan Evaporation, 1997

0

0.5

1

1.5

2

2.5

3

0 50 100 150 200 250 300 350

Time, Days

Rai

nfal

l (in

ches

/hou

r)

0

0.05

0.1

0.15

0.2

0.25

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Month

Pan

Evap

orat

ion

(inch

es/d

ay)

Quasi-Steady-State 1997 Weather Conditions55.4 inches of Rainfall

0

50

100

150

200

250

0 60 120 180 240 300 360

Time, Days

Flow

, CFS

Alternative-1 Conditions

1997-Flow Conditions

Figure 8. Simulated Annual Discharge from the Tenoroc Basin

Derby Lake

123

125

127

129

131

133

0 90 180 270 360

Time, Days

Wat

er L

evel

, Ft N

GV

D

Alternative-11997-Conditions

Figure 9. Simulated Annual Water Levels at Derby Lake

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