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Kim H. Haag

Publications and source records attributed to Kim H. Haag.

10 recordsLinked to original sources
USGS2012

Flooded area and plant zonation in isolated wetlands in well fields in the Northern Tampa Bay Region, Florida, following reductions in groundwater-withdrawal rates

The extent and duration of the flooded area were compared in two reference wetlands and nine wetlands in well fields in the northern Tampa Bay region, Florida, to determine whether reductions in well-field groundwater-withdrawal rates resulted in increases in wetland flooded area. Flooded area, expressed as a percentage of the total wetland area, was used to provide a quantitative and comparable line of evidence for describing the hydrologic conditions in isolated wetlands of different sizes and locations. Flooded-area frequencies were quantified for periods with different groundwater-withdrawal rates that bracket reductions in well-field groundwater withdrawals. Four-year pre-reduction and post-reduction periods were applied to wetlands in Cypress Creek and Cross Bar Ranch well fields, whereas 3-year periods were applied to wetlands in Starkey well field. The reduced groundwater-withdrawal rates in Cypress Creek and Cross Bar Ranch well fields were 30 and 24 percent less than their pre-reduction rates, respectively. The reduced groundwater-withdrawal rate in the Starkey well field was 64 percent less. Total rainfall amounts were similar (differed by 1 percent or less) in the respective pre- and post-reduction periods, which minimized the effect that rainfall variability had on the analysis. Flooded-area patterns at the reference wetlands, which were unaffected by groundwater withdrawals, were similar during pre- and post-reduction periods, indicating that short-term rainfall variability within those periods did not affect the longer-term patterns of flooded-area extent and duration. One well-field wetland (W-33) experienced an extent and duration of flooded area similar to that observed at the reference wetlands. About 61–100 percent of W-33 was flooded 41 percent of the time during the pre-reduction period and 45 percent of the time in the post-reduction period. The amount of time the wetland was dry decreased from 40 percent in the pre-reduction period to 26 percent in the post-reduction period. The median elevation of the potentiometric surface of the Upper Floridan aquifer increased beneath this wetland by about 4 feet after reductions in groundwater-withdrawal rates. Four well-field wetlands (W-17, W-56, Starkey N, and Starkey 108) had substantial increases in the extent and duration of the flooded area after reductions in groundwater-withdrawal rates. These four wetlands were dry for 25–45 percent less time during the post-reduction period, when the pre- and post-reduction periods were compared. Up to 20 percent of W-56 was flooded more than three times as long after reductions in groundwater-withdrawal rates. All parts of W-17 were flooded for as much as 10 percent of the time in the post-reduction period. Parts of Starkey N and Starkey 108 were flooded for more than twice as much time after reductions in groundwater-withdrawal rates. The median elevation of the potentiometric surface of the Upper Floridan aquifer was about 4–8 feet higher beneath W-17 and W-56 after reductions in groundwater-withdrawal rates, whereas the median elevation increased beneath Starkey N and Starkey 108 by about 4 feet after reductions in groundwater-withdrawal rates. Four other well-field wetlands (W-41, Q-1, Starkey D, and Starkey E) were mostly dry before reductions in groundwater-withdrawal rates and remained mostly dry after the reductions. W-41 was dry 23 percent less time in the post-reduction period, but most of the increase in flooded area was confined to less than 20 percent of the total wetland area. Q-1 was dry for only 12 percent less time in the post-reduction period. The median elevation of the potentiometric surface of the Upper Floridan aquifer increased beneath W-41 by about 5 feet and beneath Q-1 by about 2 feet after reductions in groundwater-withdrawal rates. The extent and duration of the flooded area was unchanged at Starkey D when the post-reduction period was compared to the pre-reduction period. At Starkey E the extent of the flooded area decreased slightly during the post-reduction period. Even though groundwater-withdrawal rates at Starkey well field decreased in the post-reduction period, the median elevation of the potentiometric surface of the Upper Floridan aquifer did not increase beneath Starkey D and Starkey E after reductions in groundwater-withdrawal rates from this well field. Factors such as the high permeability of sediments beneath the wetlands, subsidence, or sinkholes could contribute to continued downward leakage from these four wetlands and the lack of recovery of wetland water levels. Plant zonation in the two reference wetlands and the nine well-field wetlands was described using data collected by the Southwest Florida Water Management District and Tampa Bay Water, a regional utility, in their Wetland Assessment Procedure (WAP). A scoring system was used to describe the distribution of trees, woody shrubs, and groundcover in zones at three depths along a transect line through each wetland. The locations of the three zones were identified on contoured wetland bathymetry maps and were discussed in relation to areas of the wetland bottom that flooded for different periods of time during the study. Higher scores are characteristic of a greater extent and duration of wetland flooded area. WAP scores and weighted average scores for wetland vegetation were generally consistent with the results of the flooded area analysis. The WAP scores and weighted average scores were higher overall and did not decline with time at four wetlands in well fields (W-33, W-56, Starkey N, and Starkey 108) during the years following reductions in groundwater-withdrawal rates. These four wetlands also had increases in the extent and duration of the flooded area during the post-reduction period. Scores for trees were more consistent than scores for shrubs and groundcover. WAP scores remained relatively low or generally declined at five well-field wetlands (Q-1, W-17, W-41, Starkey D, and Starkey E) during the years following reductions in groundwater-withdrawal rates, and weighted average scores either declined over time or remained low. These five wetlands either did not have an increase in the extent and duration of the flooded area, or if there was an increase, it was small.

Florida↗
USGS2011

USGS research on Florida's isolated freshwater wetlands

The U.S. Geological Survey (USGS) has studied wetland hydrology and its effects on wetland health and ecology in Florida since the 1990s. USGS wetland studies in Florida and other parts of the Nation provide resource managers with tools to assess current conditions and regional trends in wetland resources. Wetland hydrologists in the USGS Florida Water Science Center (FLWSC) have completed a number of interdisciplinary studies assessing the hydrology, ecology, and water quality of wetlands. These studies have expanded the understanding of wetland hydrology, ecology, and related processes including: (1) the effects of cyclical changes in rainfall and the influence of evapotranspiration; (2) surface-water flow, infiltration, groundwater movement, and groundwater and surfacewater interactions; (3) the effects of water quality and soil type; (4) the unique biogeochemical components of wetlands required to maintain ecosystem functions; (5) the effects of land use and other human activities; (6) the influences of algae, plants, and invertebrates on environmental processes; and (7) the effects of seasonal variations in animal communities that inhabit or visit Florida wetlands and how wetland function responds to changes in the plant community.

Florida↗
USGS2010

Hydrology and Ecology of Freshwater Wetlands in Central Florida - A Primer

Freshwater wetlands are an integral part of central Florida, where thousands are distributed across the landscape. However, their relatively small size and vast numbers challenge efforts to characterize them collectively as a statewide water resource. Wetlands are a dominant landscape feature in Florida; in 1996, an estimated 11.4 million acres of wetlands occupied 29 percent of the area of the State. Wetlands represent a greater percentage of the land surface in Florida than in any other state in the conterminous United States. Statewide, 90 percent of the total wetland area is freshwater wetlands and 10 percent is coastal wetlands. About 55 percent of the freshwater wetlands in Florida are forested, 25 percent are marshes and emergent wetlands, 18 percent are scrub-shrub wetlands, and the remaining 2 percent are freshwater ponds. Freshwater wetlands are distributed differently in central Florida than in other parts of the State. In the panhandle and in northern Florida, there are fewer isolated wetlands than in the central and southern parts of the State, and few of those wetlands are affected by activities such as groundwater withdrawals. In southern Florida, the vast wetlands of the Everglades and the Big Cypress Swamp blanket the landscape and form contiguous shallow expanses of water, which often exhibit slow but continuous flow toward the southwestern coast. In contrast, the wetlands of central Florida are relatively small, numerous, mostly isolated, and widely distributed. In many places, wetlands are flanked by uplands, generating a mosaic of contrasting environments-unique wildlife habitat often adjacent to dense human development. As the population of central Florida increases, the number of residents living near wetlands also increases. Living in close proximity to wetlands provides many Floridians with an increased awareness of nature and an opportunity to examine the relationship between people and wetlands. Specifically, these residents can observe how wetlands are affected by human activities. Freshwater wetlands are unique and complex ecosystems defined by characteristic properties. Wetlands usually have standing water during at least part of the year, although water depths can vary from a few inches to as much as several feet from one wetland to another. The hydrologic behavior of wetlands is influenced by drainage basin characteristics, as well as by natural variations in climate. Wetlands in central Florida (especially forested wetlands) often have acidic waters that are darkly stained from organic substances released by decomposing leaves and other plant material. Wetlands are characterized by biogeochemical cycles in which vital elements such as carbon, nitrogen, phosphorus, and others are transformed as they move between wetland soils and sediments, the open water, and the atmosphere. Wetlands are populated with plants that can thrive under conditions of saturated soils and low dissolved-oxygen concentrations. The bottoms of many wetlands, especially marshes, are covered with decayed plant material that can accumulate over time to form brown peat or black muck soils. Wetlands are inhabited by animals that need standing water to complete some or all of their life cycles, and they also provide periodic food, water, and shelter for many other animals that spend most of their lives on dry land. The complex and interrelated components of wetlands directly affect one another and there are numerous feedback mechanisms.

Circular↗
USGS2006

Flooding Frequency Alters Vegetation in Isolated Wetlands

Many isolated wetlands in central Florida occur as small, shallow depressions scattered throughout the karst topography of the region. In these wetlands, the water table approaches land surface seasonally, and water levels and flooding frequency are largely determined by differences between precipitation and evapotranspiration. Because much of the region is flat with little topographic relief, small changes in wetland water levels can cause large changes in wetland surface area. Persistent changes in wetland flooding frequencies, as a result of changes in rainfall or human activity, can cause a substantial change in the vegetation of thousands of acres of land. Understanding the effect that flooding frequency has on wetland vegetation is important to assessing the overall ecological status of wetlands. Wetland bathymetric mapping, when combined with water-level data and vegetation assessments, can enable scientists to determine the frequency of flooding at different elevations in a wetland and describe the effects of flooding frequency on wetland vegetation at those elevations. Five cypress swamps and five marshes were studied by the U.S. Geological Survey (USGS) during 2000-2004, as part of an interdisciplinary study of isolated wetlands in central Florida (Haag and others, 2005). Partial results from two of these marshes are described in this report.

Fact Sheet↗
USGS2006

Strength in Numbers: Describing the Flooded Area of Isolated Wetlands

Thousands of isolated, freshwater wetlands are scattered across the karst1 landscape of central Florida. Most are small (less than 15 acres), shallow, marsh and cypress wetlands that flood and dry seasonally. Wetland health is threatened when wetland flooding patterns are altered either by human activities, such as land-use change and ground-water pumping, or by changes in climate. Yet the small sizes and vast numbers of isolated wetlands in Florida challenge our efforts to characterize them collectively as a statewide water resource. In the northern Tampa Bay area of west-central Florida alone, water levels are measured monthly in more than 400 wetlands by the Southwest Florida Water Management Distirct (SWFWMD). Many wetlands have over a decade of measurements. The usefulness of long-term monitoring of wetland water levels would greatly increase if it described not just the depth of water at a point in the wetland, but also the amount of the total wetland area that was flooded. Water levels can be used to estimate the flooded area of a wetland if the elevation contours of the wetland bottom are determined by bathymetric mapping. Despite the recognized importance of the flooded area to wetland vegetation, bathymetric maps are not available to describe the flooded areas of even a representative number of Florida's isolated wetlands. Information on the bathymetry of isolated wetlands is rare because it is labor intensive to collect the land-surface elevation data needed to create the maps. Five marshes and five cypress wetlands were studied by the U.S. Geological Survey (USGS) during 2000 to 2004 as part of a large interdisciplinary study of isolated wetlands in central Florida. The wetlands are located either in municipal well fields or on publicly owned lands (fig. 1). The 10 wetlands share similar geology and climate, but differ in their ground-water settings. All have historical water-level data and multiple vegetation surveys. A comprehensive report by Haag and others (2005) documents bathymetric mapping approaches, the frequency of flooding in different areas of the wetlands, and the relation between flooding and vegetation in these wetlands. This fact sheet describes bathymetric mapping approaches and partial results from two natural marshes (Hillsborough River State Park Marsh, and Green Swamp Marsh) and one impaired marsh (W-29 Marsh) that is located on a municipal well field and is affected by ground-water withdrawals. (fig. 1).

Fact Sheet↗
USGS2005

Bathymetry and vegetation in isolated marsh and cypress wetlands in the northern Tampa Bay Area, 2000-2004

Wetland bathymetry and vegetation mapping are two commonly used lines of evidence for assessing the hydrologic and ecologic status of expansive coastal and riverine wetlands. For small isolated freshwater wetlands, however, bathymetric data coupled with vegetation assessments are generally scarce, despite the prevalence of isolated wetlands in many regions of the United States and the recognized importance of topography as a control on inundation patterns and vegetation distribution. In the northern Tampa Bay area of west-central Florida, bathymetry was mapped and vegetation was assessed in five marsh and five cypress wetlands. These 10 isolated wetlands were grouped into three categories based on the effects of ground-water withdrawals from regional municipal well fields: natural (no effect), impaired (drier than natural), and augmented (wetlands with artificially augmented water levels). Delineation of the wetland perimeter was a critical component for estimating wetland-surface area and stored water volume. The wetland perimeter was delineated by the presence of Serenoa repens (the 'palmetto fringe') at 9 of the 10 sites. At the 10th site, where the palmetto fringe was absent, hydric-soils indicators were used to delineate the perimeter. Bathymetric data were collected using one or more techniques, depending on the physical characteristics of each wetland. Wetland stage was measured hourly using continuous stage recorders. Wetland vegetation was assessed semiannually for 2 1/2 years in fixed plots located at three distinct elevations. Vegetation assessments were used to determine the community composition and the relative abundance of obligate, facultative wet, and facultative species at each elevation. Bathymetry maps were generated, and stage-area and stage-volume relations were developed for all 10 wetlands. Bathymetric data sets containing a high density of data points collected at frequent and regular spatial intervals provided the most useful stage-area and stage-volume relations. Bathymetric maps of several wetlands also were generated using a low density of data points collected along transect lines or contour lines. In a comparative analysis of the three mapping approaches, stage-area and stage-volume relations based on transect data alone underestimated (by 50-100 percent over certain ranges of stage) the wetland area and volume compared to results using a high density of data points. Adding data points collected along one elevation contour below the wetland perimeter to the transect data set greatly improved the agreement of the resulting stage-area and stage-volume relations to the high-density mapping approach. Stage-area relations and routinely monitored stage data were used to compare and contrast the average flooded area in a natural marsh and an impaired marsh over a 2-year period. Vegetation assessments used together with flooded-area information provided the potential for extrapolating vegetation results from points or transects to wetlands as a whole. A comparison of the frequency of flooding of different areas of the wetland and the species composition in vegetation plots at different elevations indicated the dependence of vegetation on inundation frequency. Because of the broad tolerances of many wetlands plants to a range of inundation conditions, however, vegetation assessments alone provided less definitive evidence of the hydrologic differences between the two sites, and hydrologic changes occurring during the 2 years, than the flooded-area frequencies. Combining flooded-area frequencies with vegetation assessments could provide a more versatile and insightful approach for determining the ecological status of wetlands than using vegetation and stage data alone. Flooded-area frequencies may further provide a useful approach for assessing the ecological status of wetlands where historical vegetation surveys and stage data are lacking. Comparing the contemporary flooded-area frequencies a

Scientific Investigations Report↗
USGS2000

Water quality in southern Florida: Florida, 1996-98

Major influences and findings for water quality and biology in southern Florida, including the Everglades, are described and illustrated. Samples were collected to determine total phosphorus, dissolved organic carbon, pesticides, mercury, nitrate, volatile organic carbon compounds, and radon-222. Water-management, agricultural, and land-use practices are discussed. Sixty-three species of fish in 26 families were collected; 43 native species, 10 exotic or nonnative species, and 10 species of marine fish that periodically inhabit canals and rivers were identified.

Florida↗
USGS1999

Water quality in the southern Everglades and Big Cypress Swamp in the vicinity of the Tamiami Trail, 1996-97

The quality of water flowing southward in the Everglades and Big Cypress Swamp was characterized by three synoptic surveys along an 80-mile section of the Tamiami Trail and along a 24-mile transect down the Shark River Slough, by monthly sampling of a background reference site in the central Big Cypress Swamp, and by sampling of fish tissue for contaminants at several sites near the Trail. The quality of water along the Trail is spatially variable due to natural and human influences. Concentrations of dissolved solids and common ions such as chloride and sulfate were lowest in the central and eastern Big Cypress Swamp and were higher to the west due to the effects of seawater, especially during the dry season, and to the east due to canal drainage from the northern Everglades. Concentrations of total phosphorus tended to decrease from west to east along the 80-mile section of the Trail, and were usually about 0.01 milligram per liter or less in the Everglades. Short-term loads (based on average discharge for 4 days) of total phosphorus and total Kjeldahl nitrogen (ammonia plus organic nitrogen) across four gaged sections of the Tamiami Trail were highest in the Everglades near the S-12 structures primarily due to the relatively greater discharges in that section. Concentrations of dissolved solids and total phosphorus at the central Big Cypress Swamp site increased significantly during the dry season as waters ponded. Effects of nearby, upstream agricultural activities were evident at a site in the western Big Cypress Swamp where relatively high concentrations of total phosphorus, total mercury, and dissolved organic carbon and high periphyton biomass accumulation rates were measured and where several pesticides were detected. The most frequently detected pesticides along the Trail were atrazine (14 detections), tebuthiuron (11 detections), and metolachlor (5 detections), and most concentrations were less than 0.1 microgram per liter. DDT compounds were the only pesticides detected in fish from five sites. Total DDT ranged from 5 to 6 micrograms per kilogram in largemouth bass and from 11 to 17 micrograms per kilogram in Florida gar.

Florida↗