Environmental Restoration and Protection Areas

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-listedgiven 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 partnershipsfor 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 fromLanda 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 iswell established that fountain darters prefer cover in the form of vegetation and favor native vegetation, so it is possible thatestablishing 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 yearand the water enters the spring-fed pool before draining into the Old Channel (personal communication, Nathan Pence (City of New Braunfels). If the projectis 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 5.2addresses protection in the form of native aquatic vegetation maintenance and flow-split 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 thatthe 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 thatresults 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 ERPAsand 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 thanthree 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 Fand 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 neededto 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 recommendsan entrance velocity less than 0.5 fps be used in initial plans. A lower intake velocitywould 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 pumpscould 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 proximityof 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 mayultimately result in large unintendedchangesto the Old Channel that may ultimately impact the “high quality” habitatof 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 springsandhasnever 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 immediatearea. 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 thantheupwelling 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 likelydrifted 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 NFHTChas 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 spring-fed 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.