National Academies Press: OpenBook
« Previous: 3 Ecological Modeling
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

4

Monitoring

The Habitat Conservation Plan (HCP) requires the development and implementation of a monitoring plan throughout the 15-year term of the Incidental Take Permit to “…provide information for the U.S. Fish and Wildlife Service (FWS) and the Applicants to: (1) evaluate compliance with the HCP; (2) determine if progress is being made toward meeting the long-term biological goals and objectives; and (3) provide scientific data and feedback information for the Adaptive Management Process” (EARIP, 2012, page 6-2). To meet these goals, the monitoring plan must provide comprehensive information about key aspects of the hydrology and ecology of the aquifer and spring systems including groundwater flow and quality, surface water flow and quality, and selected biological habitats, populations, and communities. It must provide data that can be used to detect changes in spring flow and how the ecological system of springs and rivers responds to changes in flow. It must also allow detection of how the ecological system responds to other forcings such as incremental climate change, land-use and land-cover changes in the watersheds of the springs, mitigation and minimization efforts, and introductions or elimination of non-native species. Finally, the monitoring plan needs to provide basic information to support the development and evaluation of hydrologic and ecological models designed to understand and forecast spring flow and target species responses to changes in spring flow.

In this first report the Committee focuses on the biomonitoring and water quality monitoring programs. Collectively, these two somewhat independent programs are intended to provide the observational data needed to assess whether the HCP is meeting its goals of protecting the target species

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

as well as collecting the ancillary biological community and water quality data required to identify plausible mechanisms for observed changes in the target species abundance or distribution. In this chapter we describe these two monitoring programs, critically evaluate whether the programs are likely to achieve these goals, and offer a series of recommendations to improve monitoring as the program proceeds. Performance monitoring of ongoing or proposed mitigation and minimization measures is beyond the scope of this initial report.

BIOMONITORING PROGRAM

The Edwards Aquifer Authority (EAA) has developed a complex biomonitoring plan that covers many physical, chemical, and biological aspects of the San Marcos and Comal spring and river systems. While the program is focused on the abundance and spatial distribution of the target species (fountain darter, Texas wild rice, Comal Springs riffle beetle), it also samples the biological communities in which these species are embedded and some aspects of the physical and chemical environment such as water temperature, flow, and basic water quality variables. The biomonitoring program builds on past observations and uses a complicated combination of whole system mapping, index stations, and a series of longitudinal sampling stations depending on the particular parameter being measured.

Biological studies have been conducted in the Comal and San Marcos Springs areas by various individuals, agencies, and universities since the late 1800s when the fountain darter was first collected in the San Marcos and Comal Rivers (Schenck and Whiteside, 1976). In 2000, monitoring in these spring systems was organized under the Edwards Aquifer Authority Variable Flow Study. This study ended with the formal adoption in 2013 of the HCP, under which biological monitoring continues. Under the HCP comprehensive biological monitoring occurs two to four times per year at selected locations. In addition, high- or low-flow conditions can trigger additional sampling episodes.

Details of the biomonitoring program are provided in Tables 4-1 and 4-2 (for 2013) and Figures 4-1 through 4-5. To summarize briefly, water temperature is measured continuously at various locations in the spring and river systems. Other basic water quality variables (such as pH, dissolved oxygen, conductivity, and water depth) are measured twice a year at locations where fish sampling occurs. In addition, when triggered by low-flow thresholds, samples for nutrient analyses are taken from multiple locations along both river reaches. Aquatic vegetation is mapped throughout the entire river systems every five years, though in the San Marcos River Texas wild rice is mapped annually. Vegetation in the so-called “representative reaches” is mapped twice per year and when triggered by low-flow conditions. Foun-

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

TABLE 4-1 Components and Sampling Dates of the 2013 Biomonitoring Events in the Comal System

What When Where* Method Recurrence
Water quality Continuous for temperature Locations not disclosed Thermistors Every 10 minutes
Aug. 12 for many parameters 12 sites (Fig. 4-1) Grab samples During critical low flows
Every Friday for pH and CO2 5 sites (Fig. 4-2) Texas Naturalists Weekly
Vegetation mapping Jan-Feb Everywhere Kayak and GPS Every five years
April, Sep., Oct. 4 index reaches (Fig. 4-2) Kayak and GPS Twice a year and during critical low flows
Fountain darter sampling April, July, Aug., Oct. 4 index reaches (Fig. 4-2) Drop Net Twice a year and during critical low flows
7 locations (Fig. 4-1) Timed Dip Net Twice a year, but will discontinue if presence/ absence continues
4 index reaches (Fig. 4-2) Presence/absence Dip Nets Twice a year, but will discontinue if timed dip nets continue
Landa Lake SCUBA Not clear
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Fish community sampling April, Aug., Oct.r Certain river sections (Fig. 4-1) Seines and underwater surveys Twice a year and during critical low flows (new in 2013)
Comal salamander observations April, Aug., Sept., Oct. 4 spring locations (Fig. 4-2) SCUBA/snorkel Twice a year and during critical low flows
Comal invertebrates May-June, Nov. 3 spring locations (Fig. 4-2) Drift net Twice a year
  May-June, Sep., Oct., Nov. 10 springs at each of 3 locations: Spring Run 3, along the western shoreline of Landa Lake, and near Spring Island Cotton lures Twice a year and during critical low flows
Macroinvertebrate community sampling April, Oct. 4 index reaches (Fig. 4-2) Triple H sample Twice a year (new in 2013)

*Index reaches are called “representative reaches” in BIO-WEST (2014a).

SOURCE: BIO-WEST (2014a).

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

TABLE 4-2 Components and Sampling Dates of the 2013 Biomonitoring Events in the San Marcos System

What When Where* Method Recurring?
Water quality Continuous for temperature Not done in 2013 Locations not disclosed 18 sites (Fig. 4-3) Thermistors Grab samples Every 10 minutes During critical low flows
Vegetation mapping April-May Everywhere GPS Every 5 years
Oct. 3 index reaches (Fig. 4-3) GPS Twice a year and during critical low flows
Fountain darter sampling May, July (dip net only), Oct. 3 index reaches (Fig. 4-4) Drop Net Twice a year and during critical low flows
4 locations (Fig. 4-4, 4-5) Timed Dip Net Twice a year (3rd sampling event not explained)
15-20 sites in 3 index reaches (Fig. 4-4) Presence/absence Dip Nets Twice a year (3rd sampling event not explained)
Fish community sampling May, Oct. 4 segments (Fig. 4-4, 4-5) Seines and visual underwater surveys Twice a year (new in 2013)
San Marcos salamander May, Oct. 3 locations (Fig. 4-3) Snorkel/SCUBA Twice a year
Texas wild rice Aug-Sept. Everywhere Full system mapping via GPS Annually
Feb., Apr., May, Oct., Nov. 2 reaches Physical observations, lots of measurements Twice a year, and during critical low flows in vulnerable areas
Macroinvertebrate community sampling May, Oct. 3 index reaches (Fig. 4-3) Triple H sample Twice a year (new in 2013)

*Index reaches are called “representative reaches” in BIO-WEST (2014b).

SOURCE: BIO-WEST (2014b).

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

images

FIGURE 4-1 Fish community, water quality, and fountain darter timed dip net surveys within the Comal River study area.
SOURCE: BIO-WEST (2014a).

tain darter abundance and distribution are measured twice annually in the “representative reaches” and at additional sites. Fish community sampling is done in selected reaches (not the “representative reaches”) twice per year and when triggered by low-flow conditions. San Marcos salamander and Comal Springs salamander monitoring is done at three and four locations, respectively, twice per year. Macroinvertebrate community sampling in the “representative reaches” occurs twice per year.

Multiple components of both spring systems are monitored using five locational strategies (Box 4-1). System-wide sampling includes the entire Comal and San Marcos Rivers from the springs to the confluence with the Guadalupe and Blanco Rivers, respectively. Within these rivers, discrete points are sampled continuously for water temperature and occasionally for other water quality parameters during low-flow-triggered sampling events. “Representative reaches” are short segments of the rivers that are used as index stations and, similarly, “representative springs” are index

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

images

FIGURE 4-2 Invertebrate, salamander, Texas Master Naturalist, and representative sample reaches (includes aquatic vegetation mapping, drop-net sampling, presence/absence dip net sampling, macroinvertebrate community) surveys within the Comal River study area.
SOURCE: BIO-WEST (2014a).

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

images

FIGURE 4-3 Upper San Marcos River representative sample reaches, salamander count sites, water quality sampling and fixed station photography sites.
SOURCE: BIO-WEST (2014b).

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

images

FIGURE 4-4 Fish community sampling segments, and dip net timed survey sections (blue) for the Upper San Marcos River.
SOURCE: BIO-WEST (2014b).

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

images

FIGURE 4-5 Fish community sampling segments, and dip net timed survey sections (blue) for the Lower San Marcos River.
SOURCE: BIO-WEST (2014b).

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

Box 4-1
Spatial Sampling Strategies Used For Biomonitoring Program

  1. System-wide sampling for macrophytes
  2. Select longitudinal locations for water temperature, water quality, and fixed photography
  3. “Representative reach” sampling for macrophytes (SAV) and fountain darter netting
  4. Representative springs sampling for salamander and invertebrate sampling
  5. River section/segment sampling for fountain darter and community sampling for fish and macroinvertebrates.

sites at selected springs. Finally, additional sampling is also conducted at non-index reach sites.

It is important to note than none of the sampling locations was selected using randomization procedures. Therefore, it is inappropriate to use observations derived from the sampling locations to make inferences concerning the entire river or spring systems (with the exception of whole system mapping of vegetation). Nevertheless, the “representative reach” locations were selected purposely to cover the full range of environmental conditions and habitats exhibited throughout the entire river, and comprehensive sampling in these reaches can discern relationships among the physical and chemical environment and various biological populations and communities. Thus, these reaches can be useful as index sites to monitor long-term change, and the Committee recommends that sampling in these sites continues. But because the label “representative reach” can falsely imply that the sites can be used to scale to the entire river systems, the Committee suggests that the term “index or indicator site” or even “long-term index or indicator site” be used to more accurately describe these locations. Care should be taken to clarify that data from these index sites are not necessarily scalable to the entire river system. For the remainder of this report, the term “representative reach” is replaced with “index site” or “index reach.”

It is possible that the EAA will determine that from time to time it is important to be able to scale inferences on population density of fountain darters or other target species to the entire spring and reach system. For example, to be in compliance with the Incidental Take Permit, the EAA may decide it needs to estimate incidental take from the entire system, not just that in the study reaches. In that case, one way to make inferences on the

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

entire reach would be to do a special study to test how representative the index reaches are of the entire system, similar to what is being done now with mixed results for the submerged aquatic vegetation. An alternative approach would be to invoke some sort of randomization into the sampling protocols. One possibility would be to use the whole system aquatic plant mapping that is done every 5 years to stratify all the reaches by vegetation type and randomly sample within these strata for biological population and community variables. If aquatic plants are major drivers of fish and macroinvertebrate population and community distribution and abundance, then the relationships derived between abundance and plant community type could be used to scale up to the entire river system. Potential sampling of fountain darter in a manner that would be scalable to the entire system is discussed further in the section on biomonitoring of fountain darter.

Biomonitoring Methods

Texas Wild Rice and Submersed Aquatic Vegetation

San Marcos. Sampling of submersed aquatic vegetation (SAV) in the San Marcos system began in 2000 with two index reaches; a third reach, Spring Lake, was added soon after. The full-system aquatic vegetation mapping was added to periodically assess how representative the sample reaches are and to characterize the native and nonnative species distribution throughout the entire river. The current sampling design for Texas wild rice and SAV are (1) full-system mapping of Texas wild rice annually, (2) full-system mapping of SAV once every 5 years, and (3) sampling of SAV and Texas wild rice in three index reaches twice a year.

In terms of methods, the SAV mapping was conducted using a global positioning system (GPS) with real-time differential correction capable of sub-meter accuracy. The aquatic vegetation was identified and mapped by gathering coordinates (creating polygons) while maneuvering around the perimeter of each vegetation type at the water’s surface in a kayak. In 2013 a new protocol assessing all aquatic vegetation species was introduced; instead of mapping dominant vegetation only (as in previous years), all vegetation species in mixed stands are assigned a percent cover. This percent is multiplied by the total area of the stand to get an accurate surface area of that particular species.

The biomonitoring program also includes physical observations of Texas wild rice. When sampling began in 2000, Texas wild rice stands throughout the San Marcos River were assessed and documented as being in “vulnerable” areas if they possessed one or more of the following characteristics:

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
  1. occurred in shallow water (<0.5 feet),
  2. revealed extreme root exposure because of substrate scouring, or
  3. generally appeared to be in poor condition.

The areal coverage of Texas wild rice stands in vulnerable locations were determined in 2013 by GPS mapping (described above) in most instances, with some smaller stands measured using maximum length and maximum width. The length measurement was taken at the water surface parallel to streamflow and included the distance between the bases of the roots to the tip of the longest leaf. The width was measured at the widest point perpendicular to the stream current (this usually did not include roots). The length and width measurements were used to calculate the area of each stand according to a method used by the Texas Parks and Wildlife Department.

Comal River. The same sampling technique described above for the San Marcos River was employed to map the SAV in the Comal River system. In 2013, a comprehensive river system sampling study was conducted in January-February, as well as the annual spring-fall sampling in the sample reaches. A third sampling effort was conducted during the critical low-flow period in August.

Overall the sampling technique for gathering the percent cover of SAV in the two spring systems is adequate. A study to determine the representativeness of the current reach sampling was not uniformly successful, in that some index reaches mimicked the total river section while others did not (BIO-WEST, 2014a). For example, in the Upper Spring Run, reach coverage in 2013 was comparable to that of the total run, but the average reach coverage over the 2001–2013 time period was not. In the Old Channel and New Channel reaches, data from the index reaches measured either in 2013 or over the 2001–2013 time period did not follow the actual SAV species coverage in the entire section measured in 2013; however, in Landa Lake the data matched for both time periods. Because of the apparent sensitivity and variable response of SAV to flow conditions, particularly in the Comal River, it would be best to either sample the total river more frequently than every 5 years or increase and/or randomize the sampling locations if a more accurate representation of SAV throughout the river is desired.

The above sampling methods do not include data needed for the SAV modeling efforts, i.e., plant biomass. For dominant species and species specifically used in the modeling process, biomass data should be collected annually (and may need to be collected multiple times during the growing season to estimate specific growth rates) to validate the percent cover data and to provide accurate data for the SAV model.

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

Fountain Darter

The fountain darter sampling uses an ad-hoc design whose gear, frequency, and locations are tailored to the index reaches where responses are expected and coordinated with locations used for other aspects of the biomonitoring. Such a design is valid and likely appropriate for this type of small system and when designed by investigators who know the system, which is the case here. The key to a valid ad-hoc design is that the collected data on fountain darter are appropriately interpreted. It is possible that the EAA or others may want to use data on fountain darter densities in the index reaches to make statements about the total abundance of fountain darters in the Comal and San Marcos systems. Because the index reaches are not representative (see previous discussion), careful consideration should be given to how trends in darter density and local (reach-specific) abundance based on the index reaches will be interpreted, what constitutes a significant drop or increase (magnitude and duration), and whether and how to scale up to determine the status of the total population.

The biomonitoring for darter has, and should continue to be, modified over time in order to adopt new sampling methods and adapt to changing conditions. The key to effective modifications, such as changing sampling locations, gear, or frequency, is to ensure a sufficiently long enough period during which the old and new methods co-occur. Ensuring adequate overlap in time of the old and new sampling methods, and even maintenance of low-density sampling locations or old methods, is needed to ensure easy bridging between data based on the new and old methods and thus maintain the integrity of the accumulated time series. The need for overlapping sampling has been recognized (e.g., presence/absence with random versus fixed stations, BIO-WEST, 2014b, p. 15); however, data analyses and more rigorous evaluation need to be performed to support the extent to which the overlap is needed. Interpreting the data (from either index sites or system-wide) requires a very clean time series that is not interrupted or confounded with changes in the sampling.

It would also be timely to consider special studies related to the use of index sites to indicate fountain darter trends. These special studies could be performed for a limited time to confirm or even improve the interpretation of the standard year-to-year monitoring. One set of studies could be designed to address the representativeness of the index reaches, and to benchmark the degree of uncertainty when index information is extrapolated to the regional or system level. The study would likely use a stratified random design (to avoid too much sampling in very low density locations), and last for several years. Analyses to assess the representativeness of the index reach sampling after each year of data collection would provide valuable information on the sampling needed to fully assess the uncertainty in scaling

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

over a range of environmental conditions. Another study could confirm the present thinking that underlies the sampling locations about where darters are located and absent, and thus where sampling is not needed. Information that darters are, indeed, not found or only found in very low densities in certain habitats or locations during specific seasons would increase the confidence in the sampling results. Third, a common issue with most fish sampling is how gear selectivity and avoidance behavior, both of which can vary with conditions and habitat, affect the collected data and extrapolation of the data to broader scales (sample site to river reaches to the whole system). In this system a variety of gear is used to sample fountain darter. Some additional information on gear selectivity would be helpful for data interpretation and extrapolation and to ensure that issues about gear efficiency are not confounding results. The results of the special studies discussed above may not lead to major changes to the monitoring, but such special studies are reassuring and often yield supporting information that gets called upon as others examine, interpret, and possibly challenge the monitoring data.

Comal Springs Riffle Beetle

As part of the HCP, invertebrates in the Comal system, including the Comal Springs riffle beetle (CSRB), Peck’s Cave amphipod, and Comal Springs dryopid beetle, are sampled using two methods. First, drift nets are used at three spring locations twice a year to measure accumulated organisms (see yellow squares in Figure 4-2), with the listed species being returned to their spring of origin after enumeration. Second, cotton lures are used to attract CSRB twice a year and during critical low flows (including the drought conditions of 2013). These lures are placed at ten springs in each of three locations: Spring Run 3, along the western shoreline of Landa Lake, and near Spring Island (see Figure 4-2 in EARIP, 2012). These sampling efforts are an increase over what occurred during the EAA Variable Flow Study (BIO-WEST, 2007), in which populations of the CSRB were monitored at three spring upwelling regions of Landa Lake over six years. Taken together there are about 10 years of CSRB data from the Comal system, including during drought conditions.

The data presented in the HCP show that the populations of the CSRB were stable from 2004 to 2010 (EARIP, 2012, Table 4-8). However, in 2013 severe drought conditions substantially affected the Comal Spring system including the threatened invertebrate and salamander populations. During that drought, several of the springs that serve as habitat for the CSRB completely dried up for variable amounts of time. The populations of CSRB as measured with cotton lures were reported to be below their historical averages, which was attributed to the prolonged drought and

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

reductions in spring seep flows that either affected the populations directly or altered sedimentation rates in a way that reduced CSRB counts (BIO-WEST, 2014a). However, a long-term trend analysis from the BIO-WEST report could find no statistical relationship between total system discharge or individual spring discharge and the average number of beetles collected per lure. There could be many reasons for this, including limitations with the cotton lure method for evaluating CSRB populations, the possibility that populations are not responding to flow at those scales of measurement, or potential lag times where the populations may be responding to previous flow conditions and not the conditions noted on the day of sampling. It also calls into question the representativeness of the sampling and highlights the lack of life history information on this species, which makes it even more difficult to understand the meaning of changes in CSRB lure counts.

Interestingly, the biomonitoring conducted during 2013 found that the Texas wild rice and fountain darter populations were unaffected by the drought conditions, while the CSRB, Comal Springs salamander, and Peck’s Cave amphipod all were negatively affected. These short-term responses to drought level flows suggest that the CSRB may be the most sensitive of the listed species, warranting more thorough investigations to better understand the distribution and life history of this species and the other listed invertebrates within the Comal and San Marcos systems. A study to better understand the flow tolerances of the CSRB is part of the 2014 Applied Research Program (see Chapter 5), but as discussed below, this only scratches the surface of information needs for this species.

The main knowledge gap for CSRB is the lack of life history information, including the true densities of immature (larval), pupal, and adult life stages throughout the year; growth rates of the life stages; how many generations occur each year; how fast the life cycle proceeds; the synchrony or asynchrony of cohorts; or how the life cycle and other life history attributes like fecundity might be affected by changing flow or sediment conditions. It is possible that existing, historical data could be analyzed in a way to make life history inferences important for understanding population responses to environmental change. For instance, in the overall trend analyses of the 2013 biomonitoring report (BIO-WEST, 2014a), only adult beetles were considered; if there were similar data on larvae or pupae, some inferential life history information could be derived. Monthly quantitative sampling (surveys or some form of areal counts for density estimates) would also provide this information, as suggested by Bowles et al. (2003).

Measuring CSRB distribution should be a high priority, using a randomized or stratified randomized approach throughout Lake Landa, Spring Island, and other areas of potential habitat. One Applied Research project proposed to do something similar to this (in addition to refining CSRB collecting methods), titled Study to Establish Comal Springs Riffle Beetle

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

Baseline Population Distribution and Refine Riffle Beetle Collection Methods: Proposal No. 125-13-HCP. The study began in 2014 and should yield promising information important to understanding the broader ecological distribution of this beetle.

A major issue is the difficulty in quantifying the habitat of the CSRB and the other threatened invertebrates and salamanders, in terms of determining its areal coverage. The known primary habitats of these species are spring outflow seeps and subterranean corridors. A map of the current and potential habitat of these species is currently unavailable, but would be important for including the CSRB in future modeling efforts and identifying changes in habitat quality in response to such stressors as low flow and siltation. Furthermore, it is difficult to conduct quantitative sampling of organism density in spring outflow seeps and subterranean corridors, as described in BIO-WEST (2002), which is why the cotton lure method has been used and why the HCP goals for CSRB include maintaining silt-free spring rock and pebble substrates rather than more quantitative measures.

New methods for quantifying CSRB should be considered. For instance, much like the quantitative methods employed in the monitoring of the fountain darter and salamander populations using standardized visual surveys, the CSRB populations could be evaluated in a similar way using SCUBA or snorkel and additional hand-held magnifying tools while carefully and deliberately turning over rocks and removing and assessing vegetation for specimens in a defined area. Additionally, hyporheic pumping, freeze-coring or the use of colonization pots/baskets approaches could be modified from known methods (e.g., Scarsbrook and Halliday, 2002) to provide more quantitative CSRB counts on a monthly basis for the Comal system. If new quantitative sampling methods for the CSRB could be developed, then comparative studies could be conducted to determine how well the cotton lure approach represents densities. This information would be valuable for retrospective evaluations of the CSRB over the last 10 years when the cotton lure method was used to monitor population changes. New techniques for sampling CSRB may be difficult to undertake and may require additional funding, but are nonetheless important considerations if this listed species turns out to be one of the more sensitive species in these systems. All of this is dependent on permit take limits that should be considered with all future research on this and the other listed species.

As part of the Applied Research Program, the HCP has proposed future laboratory experiments, using Microcylloepus pusillus (Elmidae) as a surrogate species, to better understand how physical and chemical changes that may occur with lower spring velocities will impact CSRB survival. These studies could be reasonable to better describe the tolerances of CSRB and mechanisms for its survival under low flows, but only if life history information on CSRB confirms that M. pusillus is an effective surrogate (i.e.,

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

they should have similar life cycles, abiotic tolerances, habitat and food requirements, predators, diseases).

Finally, while one of the major objectives of the HCP is to limit sedimentation effects on CSRB and other species habitat through riparian restoration efforts, there seems to be no documentation on how these efforts will be measured for effectiveness and sustainability.

Even less is understood about other threatened invertebrates such as the subterranean Comal Spring dryopid beetle and Peck’s cave amphipod, and there have been fewer monitoring efforts. Additional life history and distribution studies are needed for these rare species as well, and a new approach to identifying and quantifying common habitat of these invertebrates warrants additional consideration, investigation, and resource investment.

As part of the Applied Research Program, a focused project on testing how well the CSRB acts as an indicator of the other threatened organisms is critical to a more comprehensive plan that conserves and protects all listed species in these aquifer-driven systems. Since the CSRB is thought to be restricted to springs and seeps throughout the Comal River system, a first step in testing CSRB as a multi-species indicator would be to quantify changes in the CSRB populations with matched population assessments of the other species in or near the springs and seeps. This will not be an easy task, and it will require considerable planning and the creative development of non-destructive approaches for sampling springs, adjacent habitat, and the hyporheos. However, visual survey approaches like those already being employed for the fountain darter and spring salamanders show promise for this kind of research. Additionally, recent research activity related to eDNA may offer a way to assess these more cryptic, difficult-to-sample, and rare species (Jerde et al., 2011; Thomsen et al., 2012). An eDNA approach could be evaluated for both the CSRB populations and the other listed animals and could serve as a high priority Applied Research project.

Benthic Macroinvertebrate Communities

Compared to other sampling programs, macroinvertebrate sampling has a much shorter history. Macroinvertebrate community sampling commenced in 2013 in the index reaches of both the Comal and San Marcos systems as a way to assess fountain darter food sources. It is scheduled to occur twice a year and rely on the Triple H sampling method (BIO-WEST, 2014a). The Committee recommends that the macroinvertebrate surveys be expanded to habitats that are not currently being evaluated to provide information on the overall health of the aquatic ecosystem, similar to what is done for surface waters throughout the United States as part of national bioassessment programs (Rosenberg and Resh, 1993; Barbour et al., 1999). Standard bioassessment approaches for flowing water habitats

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

are particularly useful in situations where there is a lack of information on the dominant factors affecting individual species or on how multiple species are connected, much like the Comal and San Marcos River systems. To carry this out, a stratified randomized approach using the existing vegetation mapping could be used to identify the top three or four predominant habitat types; then for each habitat, quarterly or biannual sampling could commence to determine the health of the overall macroinvertebrate community using standard EPA biomonitoring protocols. Standard macroinvertebrate biomonitoring programs are common throughout the United States and could easily be accomplished by the current expertise of the contractors of the EAA.

WATER QUALITY MONITORING PROGRAM

Water quality monitoring has occurred at various locations in the Comal and San Marcos springs and river systems for more than 10 years. The water quality monitoring program consists of five distinct parts: groundwater, surface water, stormwater, sediments, and continuous measurement (see Tables 4-3 and 4-4 for details). Groundwater is sampled at selected spring sites four times per year and more frequently under low-flow conditions. Surface water and stormwater are each sampled twice per year, with stormwater samples timed to coincide with major rain events. Sediment samples are taken once per year from the same locations as surface water samples. Continuous measurements of water temperature, dissolved oxygen, pH, turbidity, and specific conductance are made at 15-minute intervals using a multiparameter sonde. With a few minor exceptions, samples from groundwater, surface water, stormwater, and sediments are analyzed for the same comprehensive set of inorganic and organic constituents, including major anions and cations, nutrients, alkalinity, organic carbon, volatile and semivolatile organic compounds (VOCs, SVOCs), pesticides and herbicides, metals, and bacteria (see Appendices A and B in EAA, 2013).

Sample locations differ depending on the type of sampling, and while there is location overlap among sampling type, no single location is the site for surface water, stormwater, sediment, and continuous measurement (Tables 4-3 and 4-4). Similar to the biomonitoring program, sampling locations were not selected randomly and should be considered index sites that are not necessarily representative of the entire river system. In situations where it is desirable to extrapolate to the entire system to characterize a particular parameter, it is important to evaluate the degree to which the current monitoring locations are representative or to develop a randomized sampling design that can be used to provide representative samples.

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

Contaminant Sampling

A long list of organic and inorganic contaminants—from pesticides to metals—is being sampled to assess the current degree of contaminant load (see Appendices A and B of EAA, 2013 for the parameters and sampling protocols). The parameters that have been selected represent a broad set of contaminants and are generally appropriate to define baseline conditions and to identify potential impairments of the springs and river systems. However, the parameters are focused on industrial and commercial contaminants (e.g., VOCs, SVOCs, PCBs) that may not represent the most substantial risks for the springs. The potential for other contaminants, particularly those associated with urbanization and residential use, should be evaluated and incorporated into the sampling program. In particular, household chemicals, personal care products, and residential herbicides should be evaluated for their potential to be introduced into the springs and river systems.

The sampling is widely dispersed; taking the regular surface water sampling and the augmented stormwater sampling into account, contaminants are measured in unfiltered samples from 13 and 11 locations in the San Marcos and Comal Springs and river systems, respectively. Baseline sampling for the current list of constituents is appropriate, but if no significant concentrations are observed, further sampling for these parameters should be eliminated or conducted at reduced frequency and/or at fewer locations in each spring and river system, as planned (personal communication, Ed Oborny, BIO-WEST, 2014). In particular, the number of contaminant sampling locations should be reduced and effort reallocated to sampling additional storm events, should they occur. Because stream flow during storm events is likely to be high, fewer sites somewhat downstream could be monitored to get an integrated measurement. If contaminants show up in high concentration at that site, then further sampling at additional locations for that contaminant could be done in follow-up studies to pinpoint potential sources.

Methods for stormwater event sampling require further analysis and may need to include additional parameters for appropriate characterization. In particular, it may be appropriate to employ size-segregated stormwater analyses, recognizing that the fate and transport of any stormwater contaminant are closely related to particle size. Coarse particles tend to settle rapidly and will lead to near-source impacts while fine particles may be rapidly transported out of the spring-fed rivers. Conversely, fine particle-associated contaminants may exhibit greater bioavailability leading to exposure and risks of the target species. If loading from stormwater is found to be of potential concern, studies addressing the availability and fate of contaminants as a function of particle size will need to be addressed.

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

TABLE 4-3 Comal Springs Water Quality Monitoring Plan for 2014

Location Groundwater Surface Water Stormwater Sediment Sonde
Spring 1 4×/year* for complete set^
Spring 3 4×/year* for complete set^ 15 minute intervals for temperature, DO, pH, turbidity, Sp. Cond.
Spring 7 4×/year* for complete set^ 15 minute intervals for temperature, DO, pH, turbidity, Sp. Cond.
Upper Springs (near Bleiders Creek) 2×/year for constituents listed in Appendix A 2 storms/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
Upper Landa Lake (near Spring Island) 2×/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
Lower Landa Lake (above outfalls) 2×/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Upper Old Channel (Elizabeth Street) 2×/year for constituents listed in Appendix A 2 storms/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
USGS Gauge (above San Antonio Street Bridge 2×/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
New Channel (below confluence with Dry Comal Creek) 2 storms/year for constituents listed in Appendix A 15 minute intervals for temperature, DO, pH, turbidity, Sp. Cond.
Lower Old Channel (above Hinman Island) 2 storms/year for constituents listed in Appendix A
Comal River (above confluence with Guadalupe River) 2 storms/year for constituents listed in Appendix A

*Monthly sampling if San Antonio Pool critical period triggers have been reached.

^Complete set: DO, pH, conductivity, temperature, alkalinity, cations, anions, nutrients, metals, VOCs, SVOCs, herbicides, pesticides, bacteria, TOC, PCBs, and phosphorous.

Appendix A and B refer to EAA, 2013

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

TABLE 4-4 San Marcos Springs Water Quality Monitoring Plan for 2014

Location Groundwater Surface Water Stormwater Sediment Sonde
Deep Spring 4×/year* for complete set^
Hotel Spring 4×/year* for complete set^
Sink Creek 2×/year for constituents listed in Appendix A 2 storms/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
Spring Lake 2×/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
Sessoms Creek 2×/year for constituents listed in Appendix A 2 storms/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
City Park 2×/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
Rio Vista Dam 2×/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B 15 min. for temp, DO, pH, turbidity, Sp. Cond.
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Dog Beach Outflow 2 storms/year for constituents listed in Appendix A
Hopkins Street Outflow 2 storms/year for constituents listed in Appendix A
Purgatory Creek 2 storms/year for constituents listed in Appendix A
I-35 reach 2×/year for constituents listed in Appendix A 2 storms/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
Capes Dam 2×/year for constituents listed in Appendix A 1×/year for constituents listed in Appendix B
USGS Gauging Station 15 min. for temp, DO, pH, turbidity, Sp. Cond.
Willow Creek 2 storms/year for constituents listed in Appendix A

*Weekly sampling if San Marcos Springs <50 cfs; additional parameters weekly if <30 cfs.

^Complete set: DO, pH, conductivity, temperature, alkalinity, cations, anions, nutrients, metals, VOCs, SVOCs, herbicides, pesticides, bacteria, TOC, PCBs, and phosphorous.

Appendix A and B refer to EAA, 2013

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

Currently, the stormwater sampling is done manually, but two alternative sampling methods for contaminants are being considered—Gore passive samplers and automated sampling using ISCO samplers. An initial review suggests that both methods may be appropriate if the baseline sampling identifies potential concerns. Neither approach seems to be consistent with the preliminary nature of the problem identification phase that currently defines the water quality sampling program, but one or both would be needed to quantify contaminants introduced by stormwater events.

Nutrient Monitoring

Although the list of water quality parameters monitored is generally appropriate, the Committee has concerns about the monitoring of nutrients, especially phosphorus. Nutrient loading is typically an important driver of biological processes in aquatic ecosystems, especially in agricultural and urban watersheds. In many cases, the type, abundance, and distribution of algae and aquatic macrophytes is directly influenced by the nutrient regime of the water body. Because nutrient loading is typically influenced by weather, land use, land cover, and stream canopy cover, it can and does change over time in many systems. In many freshwater systems phosphorus is a limiting nutrient (Schindler, 1977 Elser et al., 2007), and because nitrogen is generally abundant in the San Marcos and Comal systems, it is likely (but apparently still not known with certainty) that phosphorus is limiting in these systems.

The reported detection limits for soluble reactive and total phosphorus measurements are 50 and 20 micrograms per liter, respectively, while the detection limits for nitrogen species are 50 micrograms per liter for NO3/ NO2 and 500 micrograms per liter for total nitrogen (Table 1 in BIO-WEST, 2014a and b). These values are above the level at which significant impairment of water quality can occur. Therefore, important changes or trends in nutrient loading to the spring and river systems could be occurring without detection. The Committee recommends that the method for phosphorus measurement be changed such that the detection limit is 2 micrograms per liter. This level of detection is standard in most non-wastewater monitoring of phosphorus, it is reasonable, and it would be helpful in detecting whether P concentrations are changing over time in a way that is meaningful to the ecology of the springs and rivers. The detection limits for NO3/NO2 and total nitrogen should be reduced to 10 and 50 micrograms/liter, respectively.

If total phosphorus concentrations above a few micrograms per liter are indeed present in the spring and river systems, the EAA should consider initiating a research project to understand the relationship between nutrient concentrations and the abundance of algae and macrophytes. Such a study

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

should consider all possible sources of water column nutrients including both the sediments as well as direct runoff from the watershed.

CONCLUSIONS AND RECOMMENDATIONS

The extensive monitoring of physical, chemical, and biological characteristics of the Comal and San Marcos spring and river systems under the Edwards Aquifer Authority Variable Flow Study from 2000-2012 and since 2013 under the HCP has provided a wealth of information upon which to base a long-term monitoring program. Choices of variables to measure and the sampling methods, locations, and frequencies were based largely on previous experience and knowledge. While in general the Committee found the monitoring programs to be strong, it also identified areas for improvement. The strengths and weaknesses are highlighted below.

The biomonitoring and water quality monitoring programs are generally well designed, comprehensive, and likely to be effective in providing information to meet the objectives of the HCP. The design and implementation of the monitoring programs was developed using expert knowledge and experience gained over more than a decade of intensive sampling and study. This prior knowledge has proved invaluable in developing the current sampling design. Monitoring of index reaches needs to continue in order to assess trends and build on existing databases.

The sampling programs do not provide a clear mechanism to scale results to the entire spring and reach system. If the EAA finds it is necessary to provide system-wide estimates of population densities of target species rather than relying on trends and index stations, it will need to invoke special studies or conduct sampling using randomization techniques. For example, a special study to determine the representativeness of the fountain darter trends estimated in index reaches would sample for darters very broadly and then examine the uncertainty associated with using the index information to infer densities and abundances at broader scales (groups of reaches and system-wide).

The biomonitoring and water quality monitoring programs are only loosely integrated. Both programs measure water temperature, dissolved oxygen, and nutrients. Both programs use multiparameter sondes for continuous measurements, but at different frequencies and perhaps with different calibration protocols. Surface water and sediment sampling locations are co-located, but there appears to be no single location that is sampled for surface water, stormwater, sediment, and continuous measurement by sonde. Water quality monitoring occurs at some, but not all, of the biomon-

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

itoring sampling locations (except for the limited water quality monitoring that is done as part of the biomonitoring program). Furthermore, annual reports for the two monitoring programs are produced independently. It is unclear whether there is a process for integrating information across the two monitoring programs in order to provide a full assessment of biological and environmental conditions. For example, it was confusing that data for phosphorus was found in the biomonitoring report, but not the water quality monitoring report.

Increased coordination and integration of the biomonitoring and water quality monitoring activities is needed. For example, whenever possible sampling sites for water quality and biomonitoring should be co-located to allow better integration and synthetic analyses.

Enhanced sampling for nutrients is recommended. The presence of annual algal blooms and the importance of aquatic macrophytes in structuring fish and macroinvertebrate communities suggest that nutrient loading plays an important role in the spring and river systems. As described in the chapter, the detection levels of 50 micrograms/liter for soluble reactive phosphorus, 50 micrograms/liter for NO3/NO2, and 500 micrograms/liter for total nitrogen are so high that significant changes in nutrient concentrations could go undetected. If the detection limits for phosphorus species, NO3/NO2, and total nitrogen were reduced to 2, 10, and 50 micrograms/liter, respectively, by changing analytical methods, this would enable identification of nutrient concerns in both spring systems.

It is expected that nutrients and other urban background contaminants may be more important than many of the specific toxins that are currently included in the sampling program. The planned elimination of many of these parameters after one or two initial rounds of sampling if significant detections are not observed is supported by the Committee. As with phosphorous, it is important that the methods used allow reliable detection of any constituent at potential levels of concern before any decision is made to eliminate that parameter.

New quantitative sampling methods are needed for the CSRB to complement and improve upon the cotton lure approach. At the same time, a large-scale stratified random survey of the potential habitat available in both systems would provide more robust data on how flow variation and sedimentation affect the habitat and thus population numbers of CSRB. The comprehensive survey of CSRB distribution proposed as part of the Applied Research Program should be given high priority.

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×

REFERENCES

Barbour, M. T., J. Gerritsen, B. D. Snyder and J. B. Stribling. 1999. Rapid bioassessment protocols for use in streams and wadeable rivers: periphyton, benthic macroinvertebrates and fish, Second Edition. U.S. Environmental Protection Agency, Office of Water: Washington, D.C.

BIO-WEST. 2002. Comal Springs Riffle Beetle Habitat and Population Evaluation. Final Report. Variable Flow Study. Edwards Aquifer Authority. 11 pp.

BIO-WEST. 2007. Variable Flow Study: seven years of monitoring and applied research: Prepared for Edwards Aquifer Authority, August. 70 pp.

BIO-WEST. 2014a. Annual report for the Habitat Conservation Plan Biological Monitoring Program Comal Springs/River Aquatic Ecosystem, March.

BIO-WEST. 2014b. Annual report for the Habitat Conservation Plan Biological Monitoring Program San Marcos Springs/River Aquatic Ecosystem, March.

Bowles, D. E., C. B. Barr, and R. Stanford. 2003. Habitat and phenology of the endangered riffle beetle Heterelmis comalensis and a coexisting species, Microcylloepus pusillus, (Coleoptera: Elmidae) at Comal Springs, Texas, USA. Archiv für Hydrobiologie 156:361-383.

EAA. 2013. 2014 Water Quality Monitoring Program Strategy for Comal Springs and San Marcos Springs in Support of the Edwards Aquifer Habitat Conservation Plan. June 11..

EARIP. 2012. Habitat Conservation Plan. Edwards Aquifer Recovery Implementation Program.

Elser, J. J., M. E. S. Bracken, E. E. Cleland, D. S. Gruner, W. S. Harpole, H. Hillebrand, J. T. Ngai, E. W. Seabloom, J. B. Shurin, and J. E. Smith. 2007. Global analysis of nitrogen and phosphorus limitation of primary producers in freshwater, marine and terrestrial ecosystems. Ecology Letters 10:1135–1142.

Jerde, C. L., A. R. Mahon, W. L. Chadderton, and D. M. Lodge. 2011. “Sight-unseen” detection of rare aquatic species using environmental DNA. Conservation Letters 4:150-157.

Rosenberg, D. M., and V. H. Resh. 1993. Freshwater biomonitoring and benthic macroinvertebrates. New York: Chapman and Hall.

Scarsbrook, M., and J. Halliday. 2002. Detecting patterns in hyporheic community structure: does sampling method alter the story? New Zealand Journal of Marine and Freshwater Research 36(2):443-453.

Schenck, J. R., and B. G. Whiteside. 1976. Distribution, habitat preference, and population size estimate of Etheostoma fonticola. Copeia 76(4):697-703.

Schindler, D. W. 1977. Evolution of phosphorus limitation in lakes. Science 195:260–262.

Thomsen, P. F., J. O. S. Kielgast, L. L. Iversen, C. Wiuf, M. Rasmussen, M. T. P. Gilbert, L. Orlando, and E. Willerslev. 2012. Monitoring endangered freshwater biodiversity using environmental DNA. Molecular Ecology 21:2565-2573.

Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 114
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 115
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 116
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 117
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 118
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 119
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 120
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 121
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 122
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 123
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 124
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 125
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 126
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 127
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 128
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 129
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 130
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 131
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 132
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 133
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 134
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 135
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 136
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 137
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 138
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 139
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 140
Suggested Citation:"4 Monitoring." National Research Council. 2015. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1. Washington, DC: The National Academies Press. doi: 10.17226/21699.
×
Page 141
Next: 5 Applied Research Program »
Review of the Edwards Aquifer Habitat Conservation Plan: Report 1 Get This Book
×
Buy Paperback | $55.00 Buy Ebook | $44.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

The Edwards Aquifer in south-central Texas is the primary source of water for one of the fastest growing cities in the United States, San Antonio, and it also supplies irrigation water to thousands of farmers and livestock operators. It is also is the source water for several springs and rivers, including the two largest freshwater springs in Texas that form the San Marcos and Comal Rivers. The unique habitat afforded by these spring-fed rivers has led to the development of species that are found in no other locations on Earth. Due to the potential for variations in spring flow caused by both human and natural causes, these species are continuously at risk and have been recognized as endangered under the federal Endangered Species Act (ESA).

In an effort to manage the river systems and the aquifer that controls them, the Edwards Aquifer Authority and stakeholders have developed a Habitat Conservation Plan (HCP). The HCP seeks to effectively manage the river-aquifer system to ensure the viability of the ESA-listed species in the face of drought, population growth, and other threats to the aquifer. The National Research Council was asked to assist in this process by reviewing the activities around implementing the HCP. Review of the Edwards Aquifer Habitat Conservation Plan: Report 1 is the first stage of a three-stage study. This report reviews the scientific efforts that are being conducted to help build a better understanding of the river-aquifer system and its relationship to the ESA-listed species. These efforts, which include monitoring and modeling as well as research on key uncertainties in the system, are designed to build a better understanding of how best to manage and protect the system and the endangered species. Thus, the current report is focused specifically on a review of the hydrologic modeling, the ecological modeling, the water quality and biological monitoring, and the Applied Research Program. The fundamental question that Review of the Edwards Aquifer Habitat Conservation Plan: Report 1 addresses is whether the scientific initiatives appropriately address uncertainties and fill knowledge gaps in the river-aquifer system and the species of concern. It is hoped that the successful completion of these scientific initiatives will ultimately lead the Edwards Aquifer Authority to an improved understanding of how to manage the system and protect these species.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!