Reviewer Affiliation Reference Comment Response A. McLean

Transcription

1 Reviewer Affiliation Reference Comment Response A. McLean A. McLean J. Redwine J. Redwine NPS The target for the PM was to... restore NSM v target envelopes throughout the GE, except in areas where deviations are environmentally beneficial. The report seems to take the 2.5' "high" as an absolute, when indeed the target was "not to exceed" in terms of # of events and PPOR. Note that I am not in any way advocating that 2.5' is valid as an extreme high event. NPS The report refers to the 2.5' high as being measured from slough bottom. As we both know, topo in the SFWMM is averaged over each 2x2 cell (4 sq mi) and so there is really no way to know, in this model and at this scale what is slough / ridge / or tree island. We understand that the performance measure for tree islands was not an absolute ban on water depths ever exceeding 2.5 ft. One of our main points is that 2.5 ft is an arbitrary threshold for tree islands and that periodically in the predrainage Everglades, tree islands experienced much higher water levels and survived them. In setting hydrologic targets (performance measures) for the Everglades, they should not be based on protecting one landscape feature or organism, but on the historic hydroperiods that occurred over wet-dry cycles. As noted below in our response to Donalson, our recommendations with regard to water depths is based on local ground elevations not the 2x2 cells used in the model. NPS Page 5/62, line4: should read:.sloughs and into ridges. Corrected unto replaced with onto NPS Page 38/62, line 8: should read..velocities need to be high enough at times during wet years.. Pages 22-25, 30, 34, 53 Clarification Requested Ponded/Compartmentalized v. Flowing System? (see detailed comments) Corrected Compartmentalization, partial drainage, and many other anthropogenic modifications to the Greater Everglades resulted in the reduction of the range of water-level fluctuations as well as an equally important change in mean water levels due to impounding water in the Water Conservation Areas. We believe that to restore the Everglades it will be essential to restore the predrainage hydroperiods, including predrainage mean water levels. If this is done, then the needed water velocities in ridge and slough areas should occur again as they did historically. Restoring flow velocities when predrainage mean annual water Page February 2012

2 Page 13,15 Pages Page 37 Clarification Requested - Is the Panel Recommending Even Further Damage to Existing Ridge-Slough-Tree Landscape? (see detailed comments) Expansion Requested - Low Water Events (see detailed comments) Expansion Requested - Plants & Animals (see detailed comments) Clarification/Expansion Requested One Hydrological Performance Measure (see detailed comments) levels over a wet-dry period are not restored will not reverse the changes that have occurred in the ridge and slough landscape and vice versa. We don t disagree that flow is important, but believe that restoring only flow per se is not enough. Obviously, we are interested in restoring the Everglades to predrainage conditions. We believe that this can only be done by restoring the predrainage hydroperiods found over wet-dry cycles. Current conditions of some landscape features and some plant and animal assemblages in the Everglades will change if this is done, but this will be balanced by improvements in conditions of other features and assemblages. The Everglades were never a static system, but a dynamic system in which all of its components were fluctuating in abundance over wet-dry cycles. Extreme droughts balance extreme high water events. Organisms and landscape features adversely affected by wet years have a chance to recover during droughts. The role of drought, other than increasing fire frequency, on plant and animal recruitment in the Everglades has not been well studied. It has, however, in many other wetlands around the world where droughts are often very important periods for recruitment of plants. The panel reviewed all the literature given to it by RECOVER. Our task was not to write a detailed literature review on plants and animals in the Everglades, but to extract from the available literature information about how water levels impact plant and animal assemblages. We do not believe that performance measures for individual landscape features or specific plant or animal assemblages make any sense. If Page February 2012

3 D. Donalson D. Donalson USACE Page 4 paragraph 2 Line 2 states: A hydroperiod is a description of water-levels at a given point over some period of time. USACE Page 37, Recommendations Within the Everglades community, hydroperiod is often defined as the number of days that water is above ground level, and does not include a water depth dimension. It would be useful for the panel to give a very clear definition of how they are using hydroperiod. In the same context, it would also be useful for the panel to define explicitly waterdepth. Are they talking about stage or depth above ground level? What would be the longest duration expected for a 5 ft. water depth in slough areas? T. Towles FWC Given the wealth of reference materials that were made available to the panel, we find the dedication of only two pages in the body of the paper and five pages in Appendix B to the effects of extreme high and extreme low water depths/durations on Everglades fauna (particularly imperiled species such as the snail kite, tricolored heron, and Cape Sable seaside sparrow) to be less than satisfactory. Could the panel please elaborate on the probable responses of the selected faunal species to the 3 hypothetical hydrological regimes? Also, could the predrainage hydroperiods, including flow, can be re-established, the resulting hydrological conditions will be suitable for the preservation/restoration of all the historic landscape features and plant and animal assemblages. Our definition of the term hydroperiod is given on p. 6 in the Scope of Work. Because our definition differs from the way that the term is used in much of the literature on the Everglades, it should also have been defined in the Executive Summary. It has been added to the Executive Summary. Because we are concerned with the impact of water depths on organisms, especially plant assemblages, water depth refers to depth above ground level at a given location. If the local ground-level elevation is known, then water depths can be easily converted to stage elevations. The maximum water depths expected during wet years (ca. 5 ft in sloughs) would have been relatively short-lived events lasting only a few months or less. These high water events would have resulted from flood pulses caused by major storms during wet years. If you eliminate the 7 pages of non-specific information (cover, index, executive summary, and scope of work) at the beginning of the report, the 14 pages of references, and the 2 pages of recommendations, you end-up with about 39 pages of factual text. Of those 39 pages, 7 pages (18 %) are devoted to plants and 7 pages (18%) to animals. Given that the panel had 4 areas to address, we believe that our coverage of the fauna was well balanced and reasonable. See also our response to Dr. Rice s fourth question. Page February 2012

4 panel better define the parameters of what would constitute a wet, normal, or dry year as presented in Table 4 and Figure 6 given the existing topography of the ridge and slough landscape? T. Towles FWC Given the smaller topographic differences between ridge, slough, wet prairie, and the various tree island communities today than presumably occurred historically (according to McVoy et al. 2011), could the panel elaborate on how the recommended 5-foot or greater slough depths and the accompanying durations would affect each of these existing vegetative communities and their respective faunal assemblages? T. Towles FWC Do the water level recommendations below stand alone or should they only be implemented as a group? In the current, compartmentalized system, for example, it seems that raising water to restore sloughs in drier sections of compartments could only be accomplished through keeping water extremely deep in the wetter sections. Would the reviewers recommend increasing slough water depths under the current, low (absent) flow system, or are these based on the assumption that flow Based on our review of the relevant literature, the panel summarized the expected impacts of high water events on ridge and slough topography (Table 2, Figure 8), major plant assemblages (Table 3), and animal assemblages (Table 4). Because there are no long term studies of the impacts of changes in hydroperiods over a wet-dry cycle for most plant and animal assemblages, we have pieced together their responses as best we can from the available literature. The recommended 5 ft. slough depth is based on historic topographic differences and because of subsidence (and accretion in some cases, i.e. WCA 3B), the absolute elevations over which water-level fluctuations occurred historically cannot be duplicated. Our view is that water velocities in the Everglades were primarily the result of water-level fluctuations (i.e., flood pulses). Flood pulses produced high water velocities locally as they passed through a section of the Everglades. The higher the flood pulse, the higher the resulting velocities. If the goal of CERP is to restore predrainage conditions to the Everglades, the panel believes that it is essential to restore the pulsed hydrology of the Everglades that occurred formerly over wet-dry Page February 2012

5 capacity is increased first? In other words, would the reviewers recommend this be accomplished through higher levees if necessary, rather than through increased flow? "Specifically, we recommend restoring interannual water level fluctuations of 5 ft in sloughs in ridge and slough landscapes." cycles. We believe that focusing on flow velocities per se is misplaced. Determining whether restoring the predrainage hydroperiods is feasible given the current levees was not one of the charges of the panel. "We recommend that water levels in sloughs never go below the peat surface." "We recommend that water flow velocities need to be high enough at times during wet years to entrain floc." T. Towles FWC Could the panel please expand on how prolonged flooding has led to the demise of tree islands in the Ridge-Slough-Tree Island Degradation section that begins on page 29? Furthermore, could the reviewers provide guidance on how to avoid such deleterious impacts while attempting to meet your recommendation to increase water depths up to 5 feet or more in contemporary ridge and slough landscapes? All our information on the number, kinds, and distribution of tree islands is relatively recent, i.e., since the 1940s. It is very likely that the number of tree islands today is higher overall than it was prior to drainage (with some obvious exceptions, such as WCA 2 and northern WCA 3A). Both prolonged dry periods and prolonged flooding can result in an increase in tree islands. The maximum depth of water during wet periods in sloughs (ca. 5ft) would only occur periodically (i.e., during wet years) for relatively short periods of time (a few months) over a wet-dry cycle (ca years). Larger and higher tree islands could easily survive periodic flooding for this length of time. Periodic flooding might reduce the abundance of some lower elevation, shrub dominated tree islands, but they would quickly reform during dry years. Page February 2012

6 T. Towles FWC On page 5 under the scope of work, there s a statement that refers to the Extreme High and Low Water Levels in Greater Everglades Wetlands Performance Measure as a performance measure (PM) to be used for evaluating hydrological impacts to tree islands. We did have a prior hydrological performance measure (with different criteria) that was designed to evaluate model output in regard to tree islands, but the current PM was designed to evaluate model output in terms of extreme hydrological events that were beyond those that would be expected to occur under natural system conditions, and would presumably apply to multiple habitats and their respective plant and animal communities. Could the panel please review the stated intent of this PM, and clarify the above statement as necessary? We agree completely with the Greater Everglades Performance Measure: Extreme High and Low Water Levels in Greater Everglades Wetlands: The ecological target is the recovery of the predrainage patterns of multiyear hydroperiods. What we have tried to do in our report is to present a framework for establishing what the multiyear predrainage hydrology of the Everglades was like. Our assessment is that extreme high and low water events should be based on mean water levels and ranges of water levels found historically during the wet and dry years of a wet-dry cycle (i.e., years). It is our understanding that the 2.5 ft and 1.0 ft thresholds used to examine the number of extreme high and low water events over the period of record was originally based on a PM developed for tree islands. The sentence in the Scope of Work section of the report (p. 5) has been changed to reflect that the 2007 Greater Everglades Performance Measure: Extreme High and Low Water Levels in Greater Everglades Wetlands covers all the major landscape of the Everglades (ridge and slough, sawgrass plains, and marl marsh). Page February 2012