Environmental Restoration and Protection Areas
Feasibility Study: Comal Springs
TPWD Comments March 23, 2011
TPWD staff has had the opportunity to review the Environmental Restoration and Protection
Areas Feasibility Study: Comal Springs report, which was prepared by Bio-West, Inc. for the
Edwards Aquifer Recovery and Implementation Program.
Section 2.0 describes the Environmental Background of Comal Springs, including a summary for
each species. TPWD supports the inclusion of the Comal Springs salamander even though it is
not Federally-listed given this species occupies habitats in close association with the Comal
Springs riffle beetle.
Section 3.0 addresses Stakeholder Interaction and identifies specific concerns raised by
stakeholders. TPWD supports the formation of a review team or future subcommittee to oversee
ERPA activities, recommend possible alternatives, and assist in study design, data collection, and
data analysis. The review team or subcommittee should be composed of experts from multiple
disciplines with an emphasis on those familiar with the listed species, such as an invertebrate
biologist, fish biologist, hydrogeologist, geomorphologist, and others. Such a team will provide
broad perspectives in developing ERPA activities, may help reduce costs through collaborative
efforts and applied research activities, and will help ensure acceptance by all involved in the
EARIP process. It would also be good to identify partnerships for implementation of the ERPAs
to share in the cost and work duties given the limited funding and broad scope of questions that
remain unanswered regarding the needs of the listed species.
Section 5.0 outlines the ERPA component description and conceptual design. Each component
of the proposed ERPA’s is addressed below.
Section 5.1 addresses restoration. The primary restoration activity proposed is the establishment
of native vegetation and removal of non-native vegetation in key, sustainable areas such as the
Old Channel and Landa Lake. TPWD staff agrees that removing non-native vegetation and
establishing native vegetation is important, but questions the long-term sustainability of
maintaining native vegetation in the Old Channel given the abundance of non-natives currently
present upstream in Landa Lake. While the removal of non-native vegetation from Landa Lake
would represent a monumental task, it is a worthwhile effort. Failure to remove the source area
of non-native vegetation places the proposed Old Channel ERPA reach in perpetual jeopardy of
revegetation of non-native species. While a flow bypass is proposed to protect the upper portion
of the Old Channel, unless properly sized, the capacity of such a bypass will not protect against
large floods, scouring, and the immigration of non-native vegetation.
An additional benefit to removing non-native vegetation from Landa Lake, assuming native
vegetation is established in its place, is the potential bolstering of fountain darter populations. It
is well established that fountain darters prefer cover in the form of vegetation and favor native
vegetation, so it is possible that establishing native vegetation in the lake will result in an
increase in darter numbers. Efforts to remove non-native vegetation could begin systematically at
the headwater confluence with Blieders Creek and work downstream. Removal of non-native
vegetation will need to be on-going and require short and long-term monitoring to be successful.
Trained volunteers and University students might be available as free or inexpensive labor for
large-scale removal.
It should also be noted that the City of New Braunfels has filed with USFWS and USACE for a
permit to address sedimentation issues with the spillway that empties into the head of the Old
Channel and erosion issues with the dam at the head of the spring-fed swimming pool.
Sedimentation at the spillway and erosion at the dam, over the last decade or more, has resulted
in the spillway lying at a higher elevation than the dam, which is currently only an inch or two
above normal pool level (personal communication, Nathan Pence, City of New Braunfels). The
City’s project proposes to raise the dam elevation and lower the spillway so that they function as
originally designed. Currently, the dam is overtopped several times a year and the water enters
the spring-fed pool before draining into the Old Channel (personal communication, Nathan
Pence (City of New Braunfels). If the project is completed, the spillway, which is located at the
head of the Old Channel, would periodically introduce higher flows to the Old Channel and
compromise the ability to manage flows and protect habitat in the Old Channel as proposed.
Section 5.2 addresses protection in the form of native aquatic vegetation maintenance and flowsplit management. TPWD staff agrees that active monitoring and maintenance will be required
to protect native vegetation establishment efforts in the Old Channel. TPWD staff supports
focusing initial efforts on the Old Channel, but views this as an area to be protected through
maintenance as well as a pilot study to inform broader efforts. Section 5.2.2 addresses flow-split
management in the Old and New Channels. The purpose of flow split management is to use
culverts at the head of the Old Channel as a tool to protect native vegetation establishment efforts
in the Old Channel and to maximize the quality of habitat in the Old Channel. Under the
proposed flow-split, the Old Channel would receive 20 cfs when the total springflow is 30 cfs.
The desired goal is to maintain 40-80 cfs of flow at all times. Hardy (2011) indicates that 20 cfs
in the Old Channel will provide approximately 75% of the maximum available fountain darter
habitat from a physical habitat perspective and that 3 of the 4 identified thermal thresholds are
not exceeded.
Section 5.2.4 addresses the proposed spring run connectivity ERPA. Hardy (2011) is quoted as
stating that “we believe the empirical data on riffle beetles demonstrates their persistence within
spring runs and Landa Lake over the past two decades strongly supports that they should be
adequately protected over the proposed flow regime.” While Comal Springs riffle beetles have
persisted in these habitats, the impact of the drought of record on the population is unclear as no
data was gathered prior. Past occupation and persistence does not ensure continued presence
during a repeat of drought of record conditions or worse.
TPWD staff is skeptical that the water quality of Landa Lake will be adequate to support
populations of riffle beetles under the proposed flow regime. Water quality at the mouth of
spring run 3 declines during low flow conditions as the western springs are reduced until the lake
springs are the sole component of flow (page B-22 of Guyton 2004). In spite of remaining
concerns regarding the placement of the proposed diffuser pipes, the possible impingement and
entrainment of organisms in the pump system, and the possible degradation of the remaining
habitat in spring run 3 as a result of pumping Landa Lake water into the habitat; TPWD staff
does not oppose this proposed project.
Section 5.2.5 outlines the Old Channel ERPA. The last paragraph on page 40 states three main
concerns noted in Hardy (2011) regarding this flow regime: 1) the potential for aquatic
vegetation die-off and subsequent dissolved oxygen (DO) problems in Landa Lake, 2) the
increase in larval mortality of fountain darters that would likely be experienced, and 3) the
potential for cool water inflows from springs along the margin of Landa Lake to flow down the
New Channel instead of entering the Old Channel. The Old Channel ERPA and protection area
is proposed, in part, to provide a safeguard in the event of a vegetation die off that results in low
dissolved oxygen levels in Landa Lake. The third major concern raised by Hardy (2011) in
regards to the short-circuiting of cool water inflows down the New Channel as opposed to the
Old Channel could have a significant impact on the success of the Old Channel ERPA and the
ability to maintain high quality habitat in the Old Channel. Before significant time and money is
invested in the Old Channel ERPA, as a whole, it seems prudent to further investigate thermal
dynamics within the water column, especially as it relates to lenses of cooler water, the Old
Channel culverts, and their relation to varying flows. This is important because the temperature
of water entering the Old Channel during low flows is a major factor in assessing the feasibility
of the proposed ERPAs and Hardy (2011) only reports average water column temperatures.
Section 5.2.5 (pg 46) describes the proposed means of recirculating water to sustain high quality
habitat within the Old Channel. Page 46 states that the “EARIP described flow regime proposes
flows to go as low as 20 cfs within the Old Channel, which strays from a high quality habitat
condition” and that “in order to increase flows back to more optimal conditions within the Old
Channel ERPA, some sort of recirculation scheme would need to be implemented.” TPWD staff
concerns with recirculation include the actual benefits derived from recirculation (cost/benefit),
the potential for increased water temperatures associated with recirculation, the means to divert
and pump more than 50% of the flow in the channel into a pipe under low flow conditions, and
the impingement and entrainment of fountain darters, among others.
Hardy (2011) estimated that a flow of 20 cfs in the Old Channel will provide approximately 75%
of the maximum available habitat for fountain darters from a physical habitat perspective. Under
extreme ambient temperature conditions, the Old Channel ERPA area is projected to maintain
water temperatures less than three of the four temperature thresholds at all times. Analysis of
Table 4 (pg 26), which presents the fountain darter weighted useable area (WUA) in the Old
Channel in relation to flow, shows there is only an 8% increase in WUA between 20 cfs and 40
cfs. This indicates that there is very little physical habitat benefit derived from increasing flows
from 20 cfs to 40 cfs. It appears as though the only benefit derived from recirculation is an 8%
increase in WUA for fountain darters. This small increase in fountain darter WUA may not
warrant such efforts and may have negative habitat impacts including increased water
temperatures, disturbance of the streambed and banks, and the impingement and entrainment of
fountain darters and other species.
A major concern for TPWD staff is the potential for the proposed recirculation project to
increase water temperatures to a point that larval mortality of fountain darters will significantly
increase. Section 5.2.5.1 addresses concerns with water temperature modeling. Modeling results
for worst-case ambient air temperature (July 2009) and maximum Landa Lake input
temperatures (80.6º F) are presented and indicate recirculation does not measurably increase
water temperatures in the Old Channel ERPA reach. However, it is not clear how “maximum
Landa Lake input temperatures (80.6º F)” were derived or used in the model. TPWD staff
assumes that it represents the maximum modeled temperature of Landa Lake water before it
enters the Old Channel. However, a review of Hardy (2011) shows temperatures in mid-Landa
Lake (upstream of Old Channel culverts) and lower Landa Lake (section that contains Old
Channel culverts) at 30 cfs total discharge range from about 77º to 85º F and about 79º to 88º F,
respectively. Thus, it appears as though “maximum Landa Lake input temperatures” were not
derived from Hardy (2011) and the modeled scenario does not represent “worst case.”
Clarification is needed regarding maximum Landa Lake input temperatures used in the model.
Also of concern is the infrastructure needed to divert and pump more than 50% of the flow in the
channel into a pipe under low flow conditions as proposed. Details of the proposal describe the
use of three, 12-inch screened pipes and a pump system that would create an entrance velocity at
the well screen of 1.5 feet per second (fps). TPWD staff is concerned about the potential for
impingement and/or entrainment of fountain darters (adult, juvenile, larval stage, and possibly
eggs), as well as other aquatic organisms, on the well screen. A typical recommendation for
entrance velocities made by resource agencies (TPWD, TCEQ, etc.) to avoid the entrainment and
impingement of organisms is 0.5 fps. Due to the size and endangered status of the fountain
darter, TPWD staff recommends an entrance velocity less than 0.5 fps be used in initial plans. A
lower intake velocity would greatly affect the configuration and number of diversion intakes that
would be required at the proposed diversion rate and suggests that at least nine intakes (as
described) would be needed. An increase in the number of diversion structures required would
have a more significant impact on the bed and banks of the Old Channel.
Additional concerns with recirculation include the potential fouling of the pumps and/or well
screens by snails, aquatic vegetation, and debris and the ramping up time needed to reach 20 cfs
of recirculation. Fouling of the well screens or pumps could cause pulsing or fluctuations in
flow and ultimately result in complete failure of the pumps due to clogging. Pump redundancy
and daily maintenance would be required to minimize fouling impacts. The report suggests water
would start to be withdrawn at smaller quantities when total discharge in the New Channel is 50
to 60 cfs and slowly be ramped up to reach the desired 20 cfs rate. This could result in
significant time when pumps are in operation and may also result in times when the pumps are
turned on and the full amount is not needed (e.g. total discharge reaches 45 cfs and then drought
ends).
Section 5.2.5.2 describes the Old Channel experimental channel. Several aspects of the
experimental channels are of concern including additional alterations to an already highly
modified system, the proximity of the channels to habitat that has been deemed Critical Habitat
and a priority for protection due to its potential for “high quality,” and the design of the proposed
channels. The plans call for the construction of two channels between the spring-fed swimming
pool and the Old Channel. As described the channels are estimated to be 15-20 feet wide, which
results in an overall width of at least 30 feet. A 30-40 foot wide channel would seemingly only
leave a sliver of land between the experimental channels and the Old Channel. Large flood
events could potentially alter the size and configuration of the experimental channels and erode
the land separating the Old Channel and the experimental channels. In addition, lesser flow
events (i.e. bankfull discharge) are also of concern due to their erosional capabilities. TPWD
staff is concerned that the experimental channels may ultimately result in large unintended
changes to the Old Channel that may ultimately impact the “high quality” habitat of the Old
Channel.
Also of concern is the proposal to construct Comal Springs riffle beetle habitat by burying a pipe
beneath substrate to provide upwelling. The Comal Springs riffle beetle is known to inhabit
springs and the area immediately surrounding springs and has never been found far from spring
orifices. The species of riffle beetle currently found in the Old Channel belongs to another genus
known to have a broad distribution in spring fed creeks and rivers. Like other spring endemics,
the Comal Springs riffle beetle is adapted to and restricted by the unique conditions found in
spring orifices and the immediate area. There is little evidence that indicates the Comal Springs
riffle beetle can survive in habitats outside of its natural range such as in the experimental
channels or the Old Channel.
Survival of the Comal Springs riffle beetle depends on more than the upwelling of water.
Research performed by BIO-WEST in coordination with the San Marcos National Fish Hatchery
and Technology Center (NFHTC) on habitat use of the Comal Springs riffle beetle found the
beetles displayed tendencies for movement downward and toward current, but supported no
statistically significant conclusions. The affinity for aquatic organisms to orient facing into
oncoming current is known as positive rheotaxis and is known to be a trait of riffle beetles as
well as many other aquatic organisms that occupy habitats with swift current. If Comal Springs
riffle beetles could survive in downstream habitats, they would have likely drifted into and
colonized these habitats at some point since construction of the Old Channel. Spring-dwelling
organisms, especially those that also utilize hypogean (subterranean) habitats, are adapted and
restricted to such habitats. The exact factors that restrict them to these habitats are not known,
but may include an affinity or need for the supersaturation of certain dissolved gases (CO2 or O2)
or food items that are only found in these habitats. USFWS staff at the San Marcos NFHTC has
experience working with riffle beetles and could likely conduct research into habitat preferences
and utilization of the Comal Springs riffle beetle that would provide insight into the factors that
limit their distribution.
Table 13 asserts that the Old Channel ERPA is not located in a highly erodible or flood prone
area and states that only the June 2010 flood caused major damage. According to City of New
Braunfels staff, the Old Channel receives excess water several times a year through the springfed swimming pool due to the previously mentioned erosion of the dam. Overbank, bankfull,
and high flow pulse flows are energetic events that can cause severe erosion in unstable systems.
A flow of 80 cfs as occurred in 2010 is known to cause extensive scouring in the Old Channel.
Flows of this magnitude or greater could have significant impacts on the experimental channel
and the Old Channel. Additional engineering and hydrology studies are needed to determine the
effective discharge of the Old Channel and the experimental channels and the capacity of the
channels for passing 10, 20, 50, and 100 year flood events. Without proper planning and design,
all ERPA efforts in the Old Channel could be compromised by high flow events.
Section 5.2.6 addresses temporary flow screens in Landa Lake. The purpose of temporary
baffles or screens in Landa Lake is to direct flow to deeper areas to reduce lake retention time
and keep lake temperatures low. The report concludes that flow screens or baffles are unfeasible
because there were no benefits extended downstream to the Old Channel and because
partitioning reportedly created areas with limited circulation and increased temperatures. TPWD
staff agrees that flow screens are unfeasible and is also concerned about potential impacts flow
screens would indirectly have on gill parasite densities. The reported limited circulation and
increased temperatures in Landa Lake created by the flow screens are the kind of conditions
likely suitable to allow the gill parasite to reach high densities, which could have negative
impacts on fountain darter populations.
Section 5.3 addresses applied research. As mentioned previously in these comments, TPWD has
serious reservations about the utility, feasibility, and stability of the proposed Old Channel
ERPAs and the experimental channels. These concerns override the potential benefits that might
be gained from directed research and studies using the channels. TPWD recommends that a
combination of laboratory and field studies continue to be employed to address the habitat, flow,
and life history needs of the species of concern in the Comal spring system as outlined in Table
14. If the deficiencies of the ERPAs as proposed can be satisfactorily addressed and mitigated,
then controlled studies using the experimental channels might be an option to compliment other
research activities.
In the interim, TPWD recommends further investigation into the potential for using properly
designed laboratory studies and sites in San Marcos to investigate the questions broached in
Table 14. While laboratory studies and research utilizing conditions representative of the San
Marcos system cannot fully replicate conditions in the Comal, they can serve as a safer
alternative and help provide needed information on the needs of the species related to stream
flow, water chemistry, and life history.
As indicated in Table 14, laboratory studies are not suitable for addressing all of the issues
related to Landa Lake inflow. While it may be difficult to simulate low flows of 10-20 cfs in the
laboratory, primary variables of interest related to different low flow volumes such as water
temperature and streamflow velocity can be controlled in a lab setting. In addition, there is a
wealth of information and data already available based on laboratory and raceway studies on
several of the species of concern. Alternatives to the experimental channels for researching low
flow effects on vegetation decay and physicochemical parameters also exist, such as utilizing
ponds at the Texas State University campus to create a microcosm of Landa Lake (personal
communication, Dr. Timothy Bonner, Texas State University Aquatic Station Director) or
utilizing ponds at the San Marcos NFHTC. Similarly, low flow effects on fountain darters and
gill parasites can be addressed through a combination of field studies and laboratory
experiments, providing both statistically significant data and a portrait of actual ecosystem
responses. For instance, the low flow effects on fountain darters could be assessed by both welldesigned experimental studies that further refine the habitat requirements of fountain darters and
monitoring their response to low flows in the field. Conditions in the upper portion of Landa
Lake at and near confluence with Blieders Creek deteriorate under low flows. The area could be
used to re-establish native vegetation and a population of darters during higher flows that could
be monitored (perhaps including mark-recapture) as flows decrease.
Another option for investigating low flow effects on the fountain darter population is a proposed
fish pass for the Slough Arm of the San Marcos River. The Slough Arm is an old channel of the
San Marcos River that was abandoned decades ago following construction of a dam and a
subsequent large flood that altered the route of the river. Water can be diverted to the Slough
Arm through an old mill race that has its head adjacent to the San Marcos River Pub. A fish pass
has been proposed to allow fish movement around the Rio Vista Dam. It is possible that a
project could be designed to investigate low flow effects on fountain darters and/or Texas wildrice, a species that cannot be researched at Comal Springs. While the flood and security
concerns with this location are similar, if not greater, than those with the Old Channel, the cost
would likely be less, the overall project would restore rather than alter natural habitat, and Texas
wild-rice could be included in future research.
The effects of low flows on gill parasites could be studied through a combination of field studies
and laboratory experiments. Ongoing studies of gill parasite densities in the water column in
relation to snail removal and the degree of infection of fountain darters should be continued.
Information from these field studies can be bolstered by laboratory experiments that provide
statistically significant information on the effects of gill parasites on fountain darters under
varying water quality conditions.
Page 85 identifies intangibles that may impede the ability to move forward with a given
alternative and cites reluctance of TPWD staff to support using the proposed experimental
channels for conducting research. Another intangible cited is the opposition of TPWD to using
the Old Channel for endangered species habitat. TPWD is indeed reluctant to support the
experimental channels as well as many aspects of the proposed Old Channel ERPA as currently
proposed, for reasons outlined in these comments.
TPWD agrees with the recommendation in the report that an EARIP ERPA subcommittee or
some form of third-party independent review team be assembled to oversee the ERPA
implementation and studies conducted during the adaptive management phase of the HCP. Given
the current lack of knowledge regarding many of the listed species and the uncertainties of biotic
community response to future low flow events, it seems as though a series of experiments and
studies formulated by an ERPA workgroup would be more beneficial and possibly more cost
effective than research using the proposed experimental channels immediately adjacent to the
Old Channel as currently designed. Implementation of any of the ERPA components will require
extensive permitting and funding. It is likely that if any of the ERPA components are
implemented, they will be in a modified form following interdisciplinary studies related to
habitat, hydrology, the species of concern, and ERPA design and operation. Creation of the
recommended subcommittee should occur as soon as practical.
Environmental Restoration and Protection Areas
Feasibility Study: San Marcos Springs
Several terms need to be quantified and/or defined. Flows variously described as “low”, “high”,
“average”, “extreme”, etc. need to have numbers or ranges of numbers if at all possible. The
draft HCP has defined the period of the drought of record and the frequency of such an event
fairly well. It should be made clear that these droughts are natural climatic events, not human induced events.
The proposed ERPA in the eastern spillway below Spring Lake is somewhat problematic for
Texas wild-rice. Not only is uncontrolled recreation a current problem, but the stands in this
location were either seeded or planted. Thus, genetic diversity within this area is probably
limited and this area would not be the best choice for a Texas wild-rice ERPA.
There are quite a few assumptions regarding the ability of Texas wild-rice to be restored and reestablished. Most are based on the increase in coverage from 1989 to present. While Texas wildrice has dramatically increased in coverage in the uppermost segments of the river (above Rio
Vista Dam), it has dramatically decreased in coverage below Rio Vista Dam. Because the
reasons for both the increase and decrease are unknown, it seems premature to assume that Texas
wild-rice can easily recover. Also, flows from 1989 to present have rarely been below 80 cfs and
have mostly been above 100 cfs or even 140 cfs. Thus, to compare the 20 year increase in cover
during a period of average and above average flows to a period when flows would be at
historical lows for months with brief pulses that would only approach the occasional low flows
does not seem analogous.
There are no documented studies of successful (i.e., increasing in coverage and sexually
reproducing) long-term Texas wild-rice reintroductions. Several small stands planted by Paula
Power in the 1990s are still extant but have not increased in coverage and do not sexually
reproduce. Again it seems early to assume that it will be easy to increase the coverage of Texas
wild-rice through removal of non-natives and replacement with Texas wild-rice. A new
reintroduction study has been initiated by Mara Alexander (USFWS-San Marcos) and Baylor
University that will hopefully provide more and better data.
It is interesting that based on the locations of Texas wild-rice in 2009, 1500 m2 would be in areas
identified as optimal habitat at a modeled flow of 45 cfs. Although it is the best estimate
available as to which stands might be viable during a drought of record, there are many other
variables that could affect the locations of stands. Even though stands do exist in suboptimal
areas, it is not possible with the data supplied to determine which of the suboptimal stands might
be lost. However, a quick check of the depth would reveal which stands would be in water too
shallow (less than 6 inches) for Texas wild-rice to persist. As no plan for recreational control has
been developed or approved, it is difficult to assess whether suboptimal or even optimal stands of
Texas wild-rice will be protected during a drought of record. Thus, it is entirely speculative and
unsubstantiated to state that over 2000 m2 would survive a drought of record.
Although the San Marcos ERPA is only minimally developed, there is such a strong case made
in the report for Texas wild-rice being able to withstand a drought of record that costs, both
monetary and political, of restoring Texas wild-rice and controlling recreation should be
provided.
TPWD staff do not agree that Texas wild-rice would be at moderate risk from the EARIP
proposed flow regime but rather that the risk would be high or severe according to the stated
definitions Anything lower than the proposed flow regime (i.e., 30 cfs) would be detrimental.
Literature Cited
Hardy, T.B. DRAFT 2011. Evaluation of the Proposed Edwards Aquifer Recovery
Implementation Program Drought of Record Minimum Flow Regimes in the
Comal and San Marcos River Systems. River Systems Institute, Texas State
University. 80 pp + electronic appendices.
LBG-Guyton Associates. 2004. Evaluation of augmentation methodologies in support of in-situ
refugia at Comal and San Marcos Springs, Texas. Prepared for the Edwards Aquifer Authority,
San Antonio, Texas.