Spring Snails Survival Threatened by SNWA Pipeline

Spring Snails Form Base of the Trophic Food Pyramid and Prevent Eutrophication in Spring Streams Threatened by the SNWA Pipeline




Contents

1) Abstract ---- pg. 1
2) Introduction ---- pg. 2
3) Spring Snail Physical Attributes ---- pg. 3
4) Spring Snail Diet and Habitat ---- pg. 4
5) Spring Snail Social Clusters and Lifestyle ---- pg. 4
6) Requirement for Listing Species as Endangered under ESA ---- pg. 5
7) Correlation between Excessive Aquifer Withdrawals and Spring Snail Population Decline ---- pg. 5
8) Carbonate Aquifer Decline Probable Given Interconnected Basin Hydraulics ---- pg. 6
9) Prior Examples of Species Extinction Following Excessive Aquifer Withdrawals ---- pg. 9
10) Reduced Spring Flow, Water Temperature and Chemistry Changes can Decrease Spring Snail Population ---- pg. 10
11) Water Permits Allocated Beyond Capacity of Yield Due to Development Pressures ---- pg. 10
12) Multifactorial Conditions Prevent Accurate Assessment of Long Term Damages and Effective Mitigation ---- pg. 11
13) Three Spring Snail Species at Risk of Extinction from SNWA Pipeline ---- pg. 12
14) Spring Snails Evolved to Overcome Ancient Climate Change, Yet Human Induced Spring Failure is Overwhelming ---- pg. 13
15) Spring Snails Form Base of Trophic Food Web Pyramid ---- pg. 13
16) Spring Snails Grazing on Periphyton and Algae Reduces Impacts of Overgrowth and Eutrophication ---- pg. 18
17) Aquifers and Spring Stream Function Best at Fullest Possible Level with Returns to Same Basin ---- pg. 28
18) Political and Financial Motivations for SNWA Pipeline Includes Development of Coyote Springs ---- pg. 43
19) A Tale of Two Texas Towns and Their Opposing Water Usage Choices ---- pg. 46
20) Long term Alternatives to SNWA Pipeline for Improving Las Vegas Water Emergency Storage Potentials ---- pg. 47
21) Conclusion ---- pg. 55
22) References ---- pg. 57


Abstract

The Southern Nevada Water Authority (SNWA) claims that they need to construct a 285 mile pipeline from Snake and Spring Valley to the Las Vegas region in order for their region to continue any future development. The proposed SNWA pipeline would most likely result in lowering groundwater tables throughout the Snake, Delmar, Cave and Spring Valley aquifer system and would dry up springs. The springs emerge at specific locations and elevations where there is an opening that connects to the aquifer complex below. At the groundwater level where water is able to reach the surface permanent springs emerge to form a diverse ecosystem that exists nowhere else throughout this desert region. At the base of the spring streams’ trophic food web pyramid are algae and periphyton that are consumed by spring snails that then provide regular food sources for many predatory species such as fish, eagles and even humans. An additional role played by spring snails is prevention of eutrophication by consumption of algae and periphyton. Eutrophication results from excess nutrients such as nitrogen entering groundwater and the watershed. Even with no extra nutrients the unchecked algae and periphyton growth would choke and suffocate small spring streams without the spring snail present. Slight reductions in spring and stream flow velocity could impact spring snail communities and allow overgrowth of algae colonies and periphyton, eventually depleting streams of oxygen and causing die off of fish and other top tier consumers and predators. The protection of spring snails under the ESA is critical to maintain a healthy spring stream ecosystem. This includes preventing excessive groundwater extractions by banning any out of basin water transfers as proposed by the SNWA pipeline.

Introduction

Spring snails have existed as an endemic species in the spring ecosystems of the Snake, Spring, Cave and Delmar Valley throughout the Great Basin region for thousands of years with little or no disturbances from humans, climate, predators or other natural factors. When ancient Lake Bonneville dried and shrank following prehistoric climate change the spring snails evolved over thousands of years to survive in the limited space and water conditions of the region’s remaining springs. The conditions spring snails evolved in occur in only their home spring, they are limited by requirements for specific temperatures, salinity, chemistry and other factors. This sensitivity to alterations in spring flow makes them especially vulnerable to extractions as a slight drop in groundwater levels can significantly reduce flow.

An entire ecosystem depends upon the spring snails and the algae and periphyton they feed upon. The spring fed ecosystems depend upon regular levels of groundwater as the aquifer is their only source of water. Rates of groundwater recharge need to replace the water lost to spring discharge each year, and this balance needs to continue for the springs to remain functional. The rate of recharge during the filling of this aquifer system was far greater during a wetter prehistoric climate than our currently dry desert conditions. Even local extractions need to be carefully monitored as they can also alter groundwater levels. If slight excesses from local extractions can drop groundwater levels, it follows that the proposal for regular large extractions by the SNWA would be expected to drop groundwater levels even more, resulting in reduced or eliminated spring flow. In order to protect spring snails from extinction due to loss of spring habitat from the SNWA pipeline they will need to be listed as endangered under the Endangered Species Act.

Protecting spring snails under the ESA requires understanding the source of the threat to their existence. Since they survived for thousands of years under relatively stable conditions the threat to their survival is not from any natural source. The primary threat to spring snails is a result of excessive groundwater extractions from local and external sources such as the proposed SNWA pipeline slowing down spring flows or drying them out. In this situation the human factor of developers and SNWA bureaucrats created a “perfect storm” of conditions that seriously threaten the existence of spring snails by lowering groundwater through excessive extractions.

Several developers including Mr. Harvey Whittemore and Mr. Albert Seeno have attempted to influence local politicians to support the Wingfield Company’s Coyote Springs housing development nearly 50 miles north of the Las Vegas urban core. In these satellite suburbs the property is inexpensive and developers can profit immensely from distant sites. However there is no water access for remote satellite developments and thus enter the need for the SNWA pipeline. Several other proponents of the SNWA pipeline are from other development corporations who are following the lead of Mr. Whittemore and Mr. Seeno by preparing for leapfrog development parallel to the pipeline route. The SNWA pipeline appears to directly correlate with the leapfrog development along the U.S. 93 highway corridor. This is also increasingly clear as other more reasonable options for water storage are ignored by water bureaucrats from the SNWA.

Spring Snail Physical Attributes

All spring snails are found in freshwater and have calcium carbonate shells to protect their soft invertebrate bodies. The patterned exterior of the shell is the periostracum and is made of organic matter. A shell’s completed circular turn is one whorl, and the last whorl is the spire. The first whorl, or protoconch, usually forms prior to hatching. The aperture is the shell’s opening, and some species have operculum coverings to seal the aperture (CBD, Petition pg. 16).

All 42 species of spring snail in the petition belongs to the family Hydrobiidae and 37 of these are members of the genus Pyrgulopsis. There are two anatomical regions in Hydrobiids; the head-foot region that consists of the snout, cephalic tentacles, eyes, neck and foot and the visceral coil region that is covered by the mantle. The genus Pyrgulopsis is identified by a thin and ovate-conic shell and a penis with few glands. The remaining five species on the list are members of the genus Tryonia that have elongate-conic shells. Spring snail species can be identified based upon differences in their shell and penis morphology. The male’s external penis is located behind the snout and has various lobes and glands attached, making observation of differences obvious (CBD, Petition pg. 16).

All members of family Hydrobiidae use gills to breathe and are “restricted to waters of unquestioned permanence and stability” needing springs with clean water and regular flow. All members of genus Pyrgulopsis and Tryonia are vulnerable to dehydration and any reduction in flow or alteration of the conditions of the spring could result in their demise. Hydrobiids can be found in any permanent type of spring fed ecosystem from small seeps to large gushing springs. The genus Pyrgulopsis often inhabits rheocrenes, the springs that flow out from below ground as streams and pour into a distinct channel, limnocrenes, the springs that form pools prior to entering the distinct channel and helocrenes, the springs that are shallow marshes with no open pools (CBD, Petition pg. 17).


Spring Snail Diet and Habitat

The plant communities that support spring snails with either shelter or food are water cress (Rorippa), bladderwort (Utricularia), spike rush (Eleocharis), and tule (Scirpus). Pyrgs prefer calcium carbonate rocks like travertine over soft sandy sediments while the genus Tyronia prefers both equally. Most spring snails prefer diatoms, bacteria, epiphytic algae and other aufwuchs species that attach to stones and larger plants while some include periphyton, detritus and other macrophytes in their diet (CBD, Petition pg. 19).

Hydrobiid population sizes are affected by factors are variable as water depth, stream shading, size of substrate material, water velocity at outflow, dissolved oxygen content, dissolved CO2 content, pH, salinity, water hardness, temperature, frequency of flooding and type of food. Pyrgs prefer spring temperatures between 10 to 40 degrees Celsius while Tyronia genus prefers thermal springs that are above 21 degrees, some within a narrow range. Conductivity levels for Pyrgs are between 70 – 37,000 umhos/cm. Other factors determining spring snail population size are spring brook wetted width and having armored and incised stream banks. Of the species studied so far, each one shows a strict preference to stream velocity, water temperatures and types of substrate material present in their habitat. As the spring snails have evolved with these specific conditions found in their preferred spring, these variables restrict them from other springs with different variables (CBD, Petition pg. 19).

The concentration of spring snails is greatest near the headwaters where conditions are most stable and decreases downstream as water temperature and chemistry is more variable. The need for stability in water conditions indicates that falling water levels would have drastic results for the populations of spring snails. According the USDI, any alterations in water flow, quality, temperature, clarity or mineral content can result in a direct loss of spring snails. Researchers Sada and Nachlinger concluded that spring snails need “high quality habitats with little disturbance” (CBD, Petition pg. 20).

Most spring snails are unable to relocate more than a few meters for each generation and are generally restricted to sections of their spring with conditions compatible with each species. Spring snails cannot cross dry or wet habitat that has inhospitable conditions for their species. Though some aquatic snails disperse with flood waters or hitchhiking on birds, these are mostly random mechanisms. Since spring snails have a narrow range of habitat conditions and cannot relocate, it follows that once a population has become extirpated from a spring their return is extremely improbable (CBD, Petition pg. 20).

Spring Snail Social Clusters and Lifestyle

Spring snails tend to cluster, with pyrg densities ranging from a few hundred to 10,000 per meter. Habitat sizes vary from smaller than one square meter to over 100 square meters in the larger springs. Those in warms springs reproduce continuously while cold spring residents only breed during warmer weather, both groups reproduce annually. Most pyrgs have a one year life span with many months required to attain breeding age, and then only mating once. Female pyrgs lay single egg capsules with single embryos on rock substrate that are often well secluded from predation. In just over a week the eggs hatch and babies around 0.3 mm long emerge ready to eat microscopic aquatic vegetation. As a result of low rates of reproduction combined with specific temperature and chemistry needs, the spring snails are vulnerable to extinction from variations in water levels (CBD, Petition pg. 20).

Requirement for Listing Species as Endangered under ESA

In order to protect spring snails under the Endangered Species Act (ESA) 16 U.S.C. 1533 the USFWS needs to list a species for protection if it is in danger of possible extinction in a significant section of its range. There are five factors used to determine this;

1) Present or future destruction, alteration or curtailment of habitat

2) Over harvesting for recreational, commercial, educational or scientific purposes

3) Disease or excessive predation

4) Already existing regulations ineffective

5) Other factors either human induced or natural that negatively influence their existence

If any one of the above listed factors results in a species becoming “in danger of extinction throughout all or a significant portion of its range” than the USFWS needs to classify it as endangered. If a species is “likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range” then it is classified as threatened. The abstract term “foreseeable future” should include the precautionary principle and also be based upon past patterns of extinctions elsewhere when a similar action was performed (CBD, Petition pg. 21).

Correlation between Excessive Aquifer Withdrawals and Spring Snail Population Decline

Credible threats to spring snail species survival exist whenever spring flows fluctuate and lower their output velocity and amounts as a result of excessive groundwater withdrawals. Any human activity that alters water discharge, velocity, depth, temperature, substrate quality, salinity and other factors places spring snail species at risk of extinction. The spring snails that reside in the smallest springs, some less than 1 cm deep and only 1 m wide are most at risk as their springs can be easily destroyed if groundwater levels fall (CBD, Petition pg. 22).
In 2002 a study of 135 aquatic endemic taxa of the Great Basin were reviewed and it was discovered that of these 68 (approx. 50%) had lost at least one of their populations over the last 140 years. They learned that 78 of these (approx. 58%) had decreased their distribution by over one half their initial population size and 15 of the total number studied became extinct. Three of the 15 extinct species were mollusks and 12 were fish. The causes of these extinctions were multifactorial; water diversions, groundwater extractions, introduction of non-native species and pollution. Of the 135 total taxa, 67% were harmed by water flow diversions, 58% by invasive species, 40% by grazing, 13% by groundwater pumping and 2% by recreation. Synergistic effects are multifactorial and account for 60% of the taxa affected. Several other studies such as a BLM plan for the Las Vegas district found 40% of spring areas they monitored were in poor condition and none were in excellent condition. Additional tests show degradation of many springs from a combination of human factors including groundwater withdrawal, water diversions or grazing and natural ones like drought (CBD, Petition pg. 23).

Several scientists have documented the correlation between groundwater withdrawal and adverse reactions of spring fed ecosystems to altered flow patterns. They explained that in most situations the human induced groundwater withdrawals removes more water than can be replenished and the level drops can reduce spring discharge or dry them out permanently (CBD, Petition pg. 24).

The carbonate rock substrate of eastern and southern Nevada forms two different types of aquifers; shallow basin-fill of unconsolidated saturated gravels and the deeper fractured carbonate sediment rocks of dolomite and limestone. Ground flow in the shallow basin-fill gravels responds to elevation while in the deep carbonate aquifers flow is determined by hydraulic gradients influenced by recharge and discharge locations. Carbonate aquifer systems allow for regional flows that move water between basins underneath mountains that usually divide watersheds on the surface (CBD, Petition pg. 24).

The carbonate aquifer water is released at spring sites when the water table meets an opening to allow the groundwater to escape and move into a stream channel or settle into a seep. The aquifer water is the main source of spring flow and thus removing groundwater by excessive pumping will result in level drop and then a decrease or entire loss of spring flow. The loss of springs can result in extinction for these four species of Pyrgs that are endemic to this region;

Longitudinal Gland Pyrg – (Pyrgulopsis anguina)

Bifid Duct Pyrg – (Pyrgulopsis peculiaris)

Sub-globose Snake Pyrg – (Pyrgulopsis saxatilis)

Spring Valley Bifid Duct Pyrg – (Pyrgulopsis peculiaris)

These four species of spring snail are all from springs found in the Snake and Spring Valley that are targeted by the SNWA pipeline (CBD Petition pg. 25).

Carbonate Aquifer Decline Probable Given Interconnected Basin Hydraulics

According to research from 2007 by Deacon et al, the interconnected aquifers will alter the hydrology of both basins if there is groundwater withdrawal, and the approval of the SNWA pipeline would lower groundwater, reduce and eliminate many regional springs, taking with them their dependent ecosystems and local endemic species found nowhere else on Earth (CBD Petition pg. 25).

The initial hydraulic head of the spring, elevation of spring opening and the distance of the pump’s location are all factors that influence groundwater levels. Groundwater flowing through a porous medium such as carbonate rocks is proportional to the hydraulic head differential or gradient, this relationship is known as Darcy’s Law. The hydraulic head differential at springs is lowered from a drawdown cone circling around the pump. Spring discharge can be reduced as the drawdown cone extends further from the pump and lowers the hydraulic head differential (CBD Petition pg. 25).

A slight lowering of the groundwater can alter spring discharge; small low elevation springs near pumping wells and also springs at higher elevation are more sensitive to water level drops. These seemingly insignificant changes in spring discharge can wreak havoc on the aquatic ecology. If only slight changes in water level can alter the ecosystem, any large scale groundwater extraction as proposed by the SNWA pipeline would cause an ecological catastrophe. According to Zektser et al; “Groundwater overdraft develops when long-term groundwater extraction exceeds aquifer recharge, producing declining trends in aquifer storage and hydraulic head. In conjunction with overdraft, declines in surface-water levels and stream flow, reduction or elimination of vegetation, land subsidence, and seawater intrusion are well documented in many aquifers of the southwestern United States” (CBD Petition, pg. 25).
Spring snails also perform a vital service to their spring community by feasting on periphyton and algae. Without constant grazing from spring snails, algae blooms and periphyton mats would take over the spring basin and create anoxic conditions of eutrophication in which very few other animals could survive. During the Early Cambrian time the transition from stromatolite and cyanobacterial mat monoculture to greater plant and animal diversity was helped by the “small shellies“, types of snails that were the ancestors of modern spring snails. The stromatolites and cyanobacterial mats of the Early Cambrian were not eaten by anything else prior to the appearance of the ancient small shelly snails (Prothero, pg. 193).

A report by Hershler and Sada explores the relationship between biogeography and snails in the Genus Pyrgulopsis, the aquatic spring snails. The spring snails are excellent indicators of prior interconnections between basins during the Cenozoic time. Their theory is that rather than a link between the Snake River Basin of Idaho and the western Lahontan Basin, there was instead continuous drainage integration across the northern boundary of the Great Basin. The spring snails have seven different regions of endemics, five of which (Death Valley system, Lahontan Basin, Bonneville Basin, Railroad Valley and White River Basin) relate to concentrations of other endemics and two (Dixie and Steptoe) with unique snail endemism. Within each of the three largest regions of endemism (Death Valley system, Lahontan Basin, Bonneville Basin) there are two or three subregions of spring snail edemism that is not paralleled by other aquatic species (Hershler, pg. 255).

The spring snails of Genus Pyrgulopsis are gastropods from the Family Hydrobiidae and were from the late Miocene where they formed tight linkages with their aquatic habitats. Spring snails are gill breathers that require permanent waters and are unable to leave their home spring habitat due to significant terrestrial barriers. The biodiversity of spring snails is a direct result of their endemism and independent evolution with many species that are locally endemic (Hershler, pg. 255).
Throughout North America there are 131 distinct species of Pyrgulopsis of which 61% reside in the Great Basin. The authors define the Great Basin as all regions with internal drainage between the Sierra Nevada and the Rocky Mountains including the Salton Trough and the human induced diversion on the Colorado River watershed (pg. 258). The Great Basin also contains the greatest diversity of spring snails with 80 recorded species, followed by the Colorado River watershed with 20 known species. The remainder are scattered throughout the western states and Mexico from the California coast east to the Rio Grande and from as far north as the Snake and Columbia Rivers south to Mexico’s Bolson de Mapimi in Chihuahua and Coahuila (Herschler, pg. 255).

Throughout their range spring snails are plentiful in aquatic benthic communities ranging in size from small seeps to large rheocrenes and limnocrenes. Their largest numbers are found closest to the source of the spring and decline downstream (Herschler. pg. 256).

Research of ancient spring snails reveals that they were restricted to littoral zones rich in oxygen or in nearby connected springs or wetlands and were not widely dispersed in paleolakes. Currently the distribution of spring snails throughout the Great Basin is widespread and many are endemic or restricted to a single spring, spring complex or drainage basin. Of the 80 species found in the Great Basin only 16 are found across major water divide drainages (Herschler, pg. 258-9).

The largest watershed drainage within the Great Basin is the Bonneville Basin subsection that includes Thousand Springs Basin, Snake and Hamlin Valleys and the Sevier River Basin, all of which contain endemic species of spring snails only found in their home springs. These three water basins also are the western, southern and eastern boundaries with the northern boundary entering southern Idaho. The Bonneville Basin has 17 species of spring snails, 14 of which are endemic. In addition to endemic spring snails are eight species of endemic fish. The spring snails of the Bonneville Basin all differ from the species found in the nearby Lahontan Basin with only a single crossover species. The greatest concentration of endemics is found in the three regions listed above (Herschler, pg. 267).

The Thousand Springs section contains three endemics; P. hovinghi, P. lentiglans and P. millenaria. Three locally endemic species reside in the Snake Valley section; P. hamlinensis, P. anguina and P. saxatilis. Each of these three has a close relative outside of their current range; P. hamlinensis with P. montana from the Meadow Valley Wash in the Colorado River drainage over the White Rock Mt. divide to the west, P. saxatilis with P. lata from the White River Valley to the west, and P. anguina with P. chamberlini from the Sevier River Basin to the east. The connection between these three sets of different relatives shows prehistoric stream capture likely occurred. In addition the distribution of P. peculiaris from the Spring Valley to the west through the Snake Valley and into the eastern Sevier River Basin shows prior drainage interconnections between these three watersheds. Other spring snails such as P. kolobensis are distributed across the Bonneville, Lahontan and Colorado River basins with noticeable differences in appearance (Herschler, pg. 268).

The Steptoe Basin includes the Antelope, Goshute, Spring and Steptoe Valleys with eight species of which six are endemics. The only spring snail found to range in both southern and northern parts of the Steptoe Basin is the far ranging P. kolobensis. Most all of the other endemics are concentrated in the northern and southern ends of the Steptoe Basin with five located in a large spring on the basin valley floor at the east side of the Egan Range north of the town of Ely. The five species of spring snails in this single location share several attributes and could be considered a species flock. Another species overlap is witnessed in the range of P. cruciglans from the northern Steptoe Basin and also in the western side of the Bonneville Basin. This interconnection is puzzling as the prehistoric shoreline of Lake Waring was not above the sill that divided the two sections during the Pleistocene. The only endemic fish of the Steptoe Basin, Relictis solitarius is not found across the divide in the Bonneville Basin (Herschler, pg. 269).

The biogeography of the spring snails in Genus Pyrgulopsis shows that the pluvial lake drainage both conforms to the status quo of drainage theories yet also considers more complicated patterns supported by evidence of overlapping ranges, species flocks and similarities between species. This report on spring snail biogeography also shows that the prehistoric Great Basin also had interchanges with other neighboring regions (Herschler, pg. 271).

The prehistoric fossil record of spring snails in the Great Basin confirms the claims made by the Center for Biological diversity that the Genus Pyrgulopsis deserves protection as they are confined to springs within their watershed. The type of above surface interconnection between springs and watersheds no longer occurs as it did during ancient times when lakeshores were higher and easily crossed by spring snails. This is evidenced by the similarities between species in neighboring watersheds that indicate evolutionary diversions over hundreds of thousands of years when the climate was wetter and lakeshores were closer together. As this wet climate ended long ago the current conditions of minimal precipitation do not allow members of Genus Pyrgulopsis any mobility outside of their home springs and therefore leaves them vulnerable to changes such as reduced spring water velocity from excessive extractions lowering groundwater levels. In prior cases of aquifer depletion from excessive extractions other endemic species of Pyrgulopsis such as the Spring Mountains spring snail have already experienced habitat losses and extirpation.

Prior Examples of Species Extinction Following Excessive Aquifer Withdrawals

The Nevada Wildlife Action Plan from 2006 shows that several large springs have either a reduced or zero flow following groundwater pumping with resulting declines in spring ecosystems. The Las Vegas dace (Rhinichthys deaconi), a spring dependent endemic, was designated extinct in 1957 when excessive groundwater extractions dried up their regional springs. As the same time the Las Vegas springs became dried out, the nearby Pahrump Valley’s Raycraft, Bennet’s and Mase springs also dried. Soon after this the Pahrump poolfish (Empetrichthys latos), an endemic of the Pahrump Valley became extinct. The following year scientists documented the extirpation of an entire population of the Spring Mountains spring snail (Pyrgulopsis deacon) (CBD Petition, pg. 26).

Groundwater pumping decreased surface flows in Owens Valley, Devil’s Hole and Ash Meadows in the 1960s. Though pumping at Ash Meadows was reduced in the early ‘80s, ongoing withdrawals continue to lower groundwater levels and discharge from springs. In the Moapa Valley groundwater extractions resulted in 13% of the studied endemic taxa having declined from lowered surface flows (CBD Petition, pg. 26).

Excess groundwater removal has resulted in losses of connectivity between groundwater and surface water habitats in Ash Meadows and Pahrump Valley. In a 2007 report by Deacon et al. results indicate that continued groundwater removal in southern Nevada could threaten 20 species federally listed as endangered along with 137 other endemic species that depend upon spring fed ecosystems. In their report they cite that the SNWA’s proposed groundwater withdrawals alone would threaten 41 species of spring snails throughout the 78 basin region (CBD Petition pg. 26).


Reduced Spring Flow, Water Temperature and Chemistry Changes can Decrease Spring Snail Population

In addition to spring failure, the 42 petitioned species of spring snails are also vulnerable to reduced flow and water quality changes such as temperature, clarity, dissolved oxygen, conductivity, sediment transport rates, mineral content and phytoplankton growth all resulting initially from groundwater extraction. Deacon explains that reduced spring flow can cause water to cool quicker, resulting in less area of habitat available for already limited endemic species that require specific water temperature ranges to survive. He states that these springs were relatively constant for thousands of years and each spring will have specific conditions in their substrate, velocity, depth and other characteristics for a short distance downstream. Both genus Pyrgulopsis and genus Tryonia are habitat specific and have poor dispersal ability, this trait makes them vulnerable to extinction if even a single spring becomes disrupted (CBD, Petition pg. 27).

Out of the total 42 petitioned spring snails, 14 are endemic to only one location, eleven from only two sites and three are found at over ten locations. The species found at multiple sites are also vulnerable to extirpation and will probably not be able to recolonize their former habitat once that happens (CBD Petition, pg. 28).

Other risks to spring snails from groundwater withdrawal include increased erosion, sedimentation, chemical spills and hydrostatic testing discharges. A study by ENSR for Clark, Lincoln and White Pine Counties in 2007 showed groundwater withdrawal would increase short term suspended sedimentation, decreased water quality from hydrostatic testing and dust control, and change the ecosystem’s food web enough to restructure the long term community and species composition (CBD Petition, pg. 28) .

Vegetation that depends upon spring water will become extirpated from these sites also, causing additional erosion, sedimentation, altered dissolved oxygen content and increased water temps from loss of shade. Invasive species can gain entry along pipeline construction roadways and also from altered spring flows (CBD Petition, pg. 28).

Water Permits Allocated Beyond Capacity of Yield Due to Development Pressures

Human population growth in the Las Vegas region is increasing rapidly and depends upon local carbonate aquifers in addition to the supply from Lake Mead and the Colorado River. The SNWA has applications for water rights of 200,000 acre feet per year (afy) and 330,000 afy total with surrounding regions applying for 870,487 afy. If all these applications were approved and that amount of water was actually removed, scientists predict groundwater levels dropping in all 78 basins over a 130,000 square km region. Studies have indicated that the carbonate rock aquifers and local springs are interconnected and are sensitive to changes in climate and groundwater levels already overdrawn. Deacon et al. discovered in 2007 that 35 basins within the Colorado River watershed have experienced aquifer level drops with existing water rights being 102% of yearly yield. In five out of eight flow systems water rights are greater than yearly yield, and also in 65 of the total 78 basins studied for potential adverse reactions to groundwater level drops (CBD Petition, pg. 28).


Since 2006 the total permits for withdrawal were up to 735,003 afy throughout the 78 basin region, with uneven rates from 0 to 1,660 % of yield estimates for each basin. Spring snails would be threatened with extinction even if groundwater withdrawals were limited to the estimated perennial yield. According to the Nevada Division of Water Resources perennial yield’s definition does not include for maintaining wetlands, stream flows, springs and their ecosystems, groundwater level and subsurface flow between basins. Perennial yield is determined by drying of springs, death of deep rooted phreatophyte plants, groundwater levels lowering, subsidence and reduced subsurface flow between basins. When water permits are issued that are 100 percent or more of perennial yield the expected outcomes are loss of springs and land subsidence (CBD Petition, pg. 29).

Multifactorial Conditions Prevent Accurate Assessment of Long Term Damages and Effective Mitigation

Uncertainty with precipitation recharge, evapotranspiration, time needed to return to equilibrium and subsurface flows combine to prevent obtaining a definite quantification of the damages and any reliable future outcome. It is without a doubt that the state’s current distribution of water permits fails to consider the ecological balance of aquifer dependent springs and seeps. This prevents the Nevada State Engineer from correctly assessing the needs of ecological stability and biodiversity when issuing water permits that only support greater suburban sprawl of the Las Vegas region (CBD Petition, pg. 29).
Since the Nevada Division of Water Resources definition of acceptable perennial yield does not prevent the drying out of springs, the spring snails listed in the petition could become extirpated from their home springs even when groundwater extractions are not above perennial yield. If the listed spring snails depend upon the state definition of perennial yield without receiving any protection from the Endangered Species Act, the resulting drying out of springs will most probably lead to their extirpation and eventually extinction. Several groundwater studies correlate with Schaefer and Harrill’s model of groundwater levels dropping from 0.3 to 488 meters across the 78 basin area from Sevier Lake in Utah to California’s Death Valley. This prediction indicates a future balance of groundwater level drops from 15 to 152 meters over a century or two. The first century would witness declines of spring flow declines by 2-14% with continuing declines until complete spring failure. These models all agree with one another with the exception of the SNWA model that predicts an above average rate of recharge from precipitation and discharge from evapotranspiration (CBD Petition, pg. 29).

The mitigation measures proposed by the SNWA are not going to be effective at saving spring snails as most of the basins where the petitioned species live already have water rights above yearly yield. Some sites have facilities to check for adverse effects of pumping, these will not be effective at protecting spring snails from extirpation or extinction. These monitoring sites will not show subtle changes in small springs or springs at unusually high or low elevations. The springs that correctly monitor discharge flow may not have mitigation test standards matching the actual physiological needs of the spring snail, resulting in a lack of support for the species prior to spring flow being at such low levels that would require protective involvement. It is unreasonable for the FWS to claim that their stipulated agreements are enough to protect spring snail habitat as spring snails are not included in their stipulated agreement. The FWS claims to monitor ecosystem health with no clear definition of the term as it relates to an induction level that would shut off pumping immediately when negative effects on the flora and fauna are observed. The specific needs spring snails have for microhabitat factors such as water temperature and chemistry result in them being harmed by reduction of spring flow that would occur prior to monitoring level triggers (CBD Petition, pg. 29).

Three Spring Snail Species at Risk of Extinction from SNWA Pipeline
Some species most at risk in the Snake and Spring Valleys include;
Pyrgulopsis anguina or the Longitudinal Gland Pyrg that inhabits small springs and shallow rheocrenes, some only 4 meters wide with a temperature range between 16-17 degrees Celsius and containing water dependent plants such as watercress (Rorippa nasturtium-aquaticum), Baltic Rush (Juncus balticus), and muskgrass (Chara vulgaris)
Pyrgulopsis peculiaris or the Bifid Duct Pyrg that inhabits small springs and shallow rheocrenes, some with temperatures ranging between 14-18 degrees Celsius, conductivity of 317-622 micromhos/cm and containing watercress (Nasturtium officinale, Rorippa nasturtium-aquaticum), Baltic Rush (Juncus balticus), and water parsnip (Berula bess).Pyrgulopsis saxatilis or the Sub-Globose Snake Pyrg, is found only in Millard County, Utah at a single spring complex including Warm Springs, Gandy Warm Springs, and Gandy Warm Creek. Their preferred habitat there is in large rocky rheocrenes with warm temps above 26.9 degrees Celsius. All three of the above species are threatened and in danger of extirpation from several of their home springs and could be faced with extinction (CBD Petition, pg. 102).

All three of the above mentioned spring snails are at risk of further population losses from excessive groundwater withdrawal. Since Pyrgulopsis anguina and P. saxatilis only inhabit the Snake Valley, and the yearly yield there is about 25,000 afy, yet with 65,949 afy of active records for that site and with SNWA applications for 50,679 afy in Snake Valley the total aquifer level drop could be from 0.3-30 meters and render both species extinct (CBD Petition, pg. 103).

Both Pyrgulopsis peculiaris and Pyrgulopsis anguina only inhabit Big Springs and two others close by, all located in a region vulnerable to groundwater level drops from excessive drawdowns. Spring flow reductions can also have adverse effects on their habitats, leading to species extirpation as in some cases such as Warm Spring on the Utah side of Snake Valley since it is the only remaining habitat for Pyrgulopsis saxatilis. The Lincoln County Land Act is an agreement between Utah and Nevada and applies to the water usage and distribution between the states from their shared Snake Valley basin. However, the most probable outcome of this agreement will be degradation of the spring snail habitat regardless of which state secures the most water rights.

In Spring Valley the SNWA claims water rights to extract 40,000 afy initially and up to 60,000 afy in ten years, resulting in a drawdown cone that would lower and eventually eliminate surface flows of springs that P. peculiaris depends upon. If the extractions proposed by the SNWA continue at this rate, the alluvial aquifer level could fall over 200 feet in only two centuries and also lower groundwater levels in the next door basin Snake Valley. Since the yearly yield of Spring Valley is near 80,000 afy, and 84,878 afy are claimed and 166,212 afy are total active claims the groundwater level drop is estimated from between 0.3 – 3.0 meters and up to 60 meters after 75 years of extractions by the SNWA (CBD Petition, pg. 104).

This severe decline in groundwater level and spring discharge can alter the vegetation from wetland species to desert species, resulting in the extirpation of the Bifid Duct Pyrg from Turnley Spring at Sacramento Pass over two decades. Currently no groundwater withdrawal agreement between Utah and Nevada provides protection to the spring snails. The vague definitions of “ecosystem health” with no indication as to when to cease extractions would fail to protect spring snails from the adverse effects of lowered spring flow (CBD Petition, pg. 105).

Spring Snails Evolved to Overcome Ancient Climate Change, Yet Human Induced Spring Failure is Overwhelming

The biodiversity of uniquely different spring snail species shows that their home springs were flowing regularly for thousands of years and more, enabling them to evolve in relative isolation to other species from nearby spring complexes. Of the 42 spring snail species petitioned for endangered status, 38 are critically imperiled, three are imperiled and one species may already be extinct. Since spring snail habitat is restricted to only permanent springs, the presence of a healthy population of spring snails indicate that their spring was flowing regularly since prehistoric times (CBD Petition, pg. 117).

If spring snails survived in these narrow niches for thousands of years without any problems, who are modern humans to decide that now their time is up because we need more golf courses? The loss of spring snails due to anthropocentric arrogance would be a tragedy with far reaching consequences, as the entire ecosystem of fish, amphibians, reptiles and mammals is based upon the populations of spring snails as the base level of the trophic food pyramid (CBD Petition, pg. 117).

Spring Snails Form Base of Trophic Food Pyramid

According to the Nevada Wildlife Action Plan; “In addition to springs’ critical role in the survival and conservation of endemic aquatic species, they also play a very important role for other wildlife species. Nevada, which has the lowest annual rainfall in the U.S., has limited surface water resources, particularly during drought. Springs provide a vital water source between infrequent surface waters, providing water availability and food resources for a wide range of Nevada’s wildlife, from bighorn sheep, elk, and deer; to birds and bats. The broad distribution of functional spring and spring outflow systems of all types across Nevada’s landscape is an important element in maintaining Nevada’s wildlife diversity” (CBD Petition, pg. 117).

There are very few other species that can reproduce and thrive on the algae and periphyton found in springs and seeps throughout the Great Basin besides the spring snail. The level of food needed to support this base of the food pyramid depends upon a regular water source coming up from the aquifer and out of the spring. Without this water exiting the ground there would be no vegetative growth in such quality and quantity as needed to support the spring snail population. The species of frogs, reptiles, fish, birds and mammals that depend upon spring snails as their nutritious food source cannot survive without them. Removal of this crucial food source resulting from dried out springs can result in massive famine for the predatory species that rely on spring snails for a regular food source.

The trophic food pyramid or web is built upon the base level of autotrophic biomass of vegetation called primary producers that derive energy from sunlight and use photosynthesis to store this energy that is eventually ingested by the next level of heterotrophic consumers. According to the energy flow paradigm the heterotrophic consumers only convert ten percent of the energy from autotrophs into formation of heterotrophic biomass. Secondary production is not just limited to measuring the energy flowing between trophic levels as it can also explain complex interactions in ecosystems such as stoichiometry. (UA, Benke).

Secondary production can help quantify the connections between many different links on a food web or trophic pyramid diagram by measuring energy flow for each species. The energy flow webs combine data on production and diet analysis for one species or taxa expressed in mass per square meter over a specific time frame (grams m2 y-1). The energy flow shows quantitative differences between ingestion flows and linkage strengths between the species and their food source measured in total amount of food ingested be each consumer (UA, Benke).

The ratio of ingestion flows to resource production can show strength of interactions or predation pressures. A strong top-town interaction is when a predator or heterotrophic consumer ingests a large portion of the primary producer or prey or autotroph’s biomass production without considering the absolute amount of the production. The trophic position is used to describe the ranking within a trophic hierarchy in more specific detail and is calculated from the combination of ingestion flows to any species located within a flow web. The trophic position of 3.2 is more specific than a standard trophic level of three reserved for all secondary consumers (UA, Benke).

Secondary production and trophic flow webs depend upon the ability of scientists to measure production in the field, and recent research has focused on freshwater and marine benthic invertebrates. Production of specific taxon has been determined for complete invertebrate assemblages in stream ecosystems by researchers collecting assemblage wide production estimates, gut analyses and food specific ecological efficiencies. Each species can have a flow web based upon the amount of food source needed to sustain their production (UA, Benke).

A connectivity web begins the basis for determining the presence or absence of food items through gut analysis. By quantifying the gut analysis from the connectivity web a diet proportion web can be formed, which can then become an assimilation web by including measurements of ecological efficiency. Finally the assimilation web can become a quantitative flow web by using secondary production data and finally an ingestion/production web can be created to determine the trophic position of each species in the flow web (UA, Benke).

The simplest connectivity web can be built using qualitative gut content data without considering the relative proportion in the gut. Though even the most detailed connectivity webs cannot determine the varied linkage strengths between the species, they can be used to measure the number of interactions per species and the maximum food chain length from the primary producer’s base of plant resources to the highest level consumer predator. The diet proportion web based upon quantitative gut data and the percentages of different food types found can be shown as a line with relative proportions of food type consumed shown as thickness of the line with a specified percentage proportion for each food type line that adds up to 1.00 as the total food consumed. The line thickness only shows diet preferences for each consumer, not the differences in absolute ingestion. Assimilation webs or assimilation/ingestion (A/I) efficiencies show the actual absorption of the percentage of the food items used for growth and metabolism. To determine the relative amount of each food type consumed the diet proportion of food type needs to be multiplied by the assimilation efficiency. The results shown in the assimilation web are noticeably different for animals with a varied diet that have consumed food types with different assimilation efficiencies and less apparent for animals that consume from the same food type. The completed assimilation web would be combined with data on secondary production to discover the trophic basis of the amount of secondary production for a single species of consumer that is designated to a single food type. In addition the total production of all species from a single food type can be established from the assimilation web (UA, Benke).

The completed flow webs include absolute ingestion flow from a specific food type to the consumer species, obtained by dividing the production of the food type by the gross production efficiency (GPE). The GPE is the product of the A/I times the production efficiency (production divided by assimilation or P/A), written as the following equation;

GPE = (A/I) x (P/A) = P/I

Since the GPE will be a number lower than one, the total consumed food types will be much higher number than the production resulting from the consumed food. When individual ingestion flows (gm-2y-1) are recorded for each interaction a quantitative flow web can be created for the entire assemblage and community.

The quantitative food web can show the trophic level of a consumer by following the longest feeding change and can show the trophic position (TP) by adding one to the sum of the trophic position of each food type (FTP) consumed times the percentage of energy each food type gave to the consumer’s production (PE%), written as the following equation;

TP = 1 + (FTPa x PE%) + (FTBb x PE%)

In order to discover the trophic position for all species, the trophic position of the species closest to the primary production base of the trophic food web needs to be determined first (UA, Benke).

An ingestion/production (I/P) web shows the effects of predation on animals or plants from a top down perspective, measured by the consumption of the predator divided by the production of a prey species (g m-2y-1). The resulting I/P ratio is expressed without any unit measures since both values use the same unit measures, effectively canceling them out. The total sum of all the percentages of ingested food types compared to predators shows the total production percentage from consumption and the entire impacts of all predation types on a specific species. If only one predator with a P/I ratio of 0.10 does not impact prey or producer species, adding 9 additional predator species with the same P/I value would be cumulative, resulting in P/I = 0.9, with the largest total impact being 1.00 as the greatest possible impacts (UA, Benke).

The drawing of the connectivity food webs are from top to bottom with respect to feeding directions. The thickness of the lines in diet proportion food webs show percentage of food types found in the gut and in assimilation food webs show the percentage of food consumed that is used for the production of energy in the consumer. The line thickness in flow webs show the absolute flow (g m-2y-1) of each food type from below being consumed by a species and in ingestion/production (I/P) food webs show the ratio (0 – 1.00) of consumption divided by the production of prey or plant resource (UA, Benke).

The authors of the report invented a hypothetical stream ecosystem to illustrate the uses of their enhanced trophic food web. The trophic web included two primary producers (algae and detritus), a primary consumer herbivorous insect chironomid (midge), an omnivorous insect trichopteran (caddisfly), and two predaceous carnivorous insects; plecopteran (stonefly) and megalopteran (hellgrammite). The connectivity web for the hypothetical stream ecosystem shows the standard relationships between producers and consumers; with chironomids (Ch) eating algae (Al) and detritus (De) trichopterans (Tr) eating (De) and (Ch), plecopterans (Pl) eating (Ch) and (Tr), and megalopterans eating (Tr), (Pl) and (Ch). The diet proportion web based on feeding percentages shows total sum (1.00) of food consumed; for (Ch) food (Al) is 0.50 and (De) is 0.50 and for (Tr) food (De) is 0.70 and (Ch) is 0.30. The assimilation web based on efficiency of absorption of feeding percentages also shows total sum of 1.00 of food consumed and used in growth or production on consumer. For (Tr) food intake of (Ch) is 0.30, yet the high assimilation efficiency (0.70) of (Ch) results in an assimilation value of 0.75 for (Ch). Another difference is the (Ch) food intake of (Al) is 0.50, and the assimilation value of (Al) as 0.80 due to the greater absorption and digestibility of (Al) over (De) with regards to (Ch) is the primary consumer (UA, Benke).
The flow web that shows the amount of total food consumed and ecological efficiencies can often have a wide range of line thickness with values between 29 to 40,000 mg m-2y-1, this extreme variation as a result of production variation amongst the species being studied, depends mostly upon the production value of each consumer. The ingestion flow is usually greatest for the species with the highest production; with (Ch) consuming 40,000 mg m-2y-1 equally for (Al) and (De) yet having a production value of 0.80 from (Al). This discrepancy between the equal consumption rates of vegetation and the 0.80 assimilation value shows the importance of considering the assimilation efficiency of the various food types throughout the ecosystem. Other differences between production and total consumption is found when comparing the consumption percentage of 0.70 for (De) as digested food in (Tr) to 0.50 in (Ch) despite the greater total amount of (De) consumed by (Ch) in the flow web. The flow web consumption of animal prey for omnivorous (Tr) is 4,286 mg m-2y-1 yet is only 286 mg m-2y-1 for (Pl) and 1,428 mg m-2y-1 for (Me), both of which are strict carnivores (UA, Benke).

The ingestion/production (I/P) web shows the production values of prey and producers, ingestion flow per consumer, individual flow I/P and the total I/P per food source. There are also wide ranges (0.01 – 0.80) of individual impacts of consumer carnivores on producers or other primary consumer herbivores though only a narrow range (0.37 – 0.80) of total consumer influences on producer or primary consumer species. The highest influences between species are from (Ch) on (Al) at 0.80 and on (De) at 0.50, then from (Tr) on (Ch) at 0.43, next from (Me) on (Tr) at 0.36 and finally from (Me) on (Pl) at 0.57. The trophic position is obtained from the flow web data and shows five trophic levels in ascending order from producer to consumer, with (Al) and (De) at (1), (Ch) at (2), (Tr) at (3), (Pl) at (4) and (Me) at (5). The trophic position shows variation between trophic levels to express the complexity of interactions between primary and secondary consumers. Some share the same positions and levels, such as (Al) and (De) since they are both on the base level as primary producers, (Ch) is also at (2) for both position and level. Differences appear in (Tr) on level (3) and position (2.8), in (Pl) at level (4) and position (3.1) and in (Me) at level (5) and position (3.4). These differences between trophic level and trophic position indicate the need to further examine ecosystems such as spring streams to determine the sensitivity of the endemics to human changes such as lowering of the water table and reduced spring flow from excessive extractions (UA, Benke).

The flow web is the most informative trophic web as it shows actual flows instead of only ratios and can quantify the strength of the links from a bottom to top outlook. For a top to bottom outlook using the I/P web is the best option. In the instance of (Tr) consumption of (Ch) at ingestion of 0.43 shows a strong connection, though two other consumers depend upon (Ch) raising their I/P to 0.52. Certain stream ecosystems in reality show total consumption at above 90% of producer production, showing strong top to bottom impacts with diffuse predation divided between several different species of consumers (UA, Benke).

The trophic position category introduces a staggered hierarchy within the trophic level system giving additional information based upon consumption preferences, such as (Me) at trophic level (5) consuming food types at trophic positions below (3), giving (Me) a trophic position of 3.4. The trophic position concept is similar to the stable isotope (SI) methodology where there is always fractionation between trophic levels. When used in combination the bottom to top links of food webs, top to bottom links of ingestion/production webs and trophic position assessments with ratios can help provide ecosystem researchers with an improved view of the complex interactions of stream and other ecosystems (UA, Benke).

The trophic food web pyramid in unique ecosystems like springs and seeps is a precariously balanced ecosystem supported by the base producer species such as algae or detritus (dead plants or animals) and primary consumer herbivore (snails, insects, other invertebrates) that can reproduce quickly enough to feed several species of secondary consumer omni-/carnivores without suffering any significant population losses themselves. The trophic food web pyramid is generally in the shape of a triangle containing ascending trophic levels with the primary producer vegetation at the base level, next level are primary consumer herbivores and then finally secondary consumer omni-/carnivores at the very top levels.

The upper levels (4-5) of the trophic pyramid for springs and seeps of the Great Basin would include secondary or tertiary consumers such as hawks, eagles, owls, snakes, large fish including Lahontan cutthroat trout and even human residents. Below them on levels (3-4) are primary or secondary consumers such as lizards, small insectivore birds like wrens, rodents, frogs and smaller fish. The lower and broader base levels (2-3) consists primary consumers such as spring snails, insects, turtles and microscopic organisms such as zooplankton. Finally the broadest land bottom base level (1) consists of primary producers such as algae, periphyton, vascular macrophyte plants, willow trees and other streamside species of vegetation that use photosynthesis to harness energy from the sun into biomass that supports all the consumer species above them.
The population numbers of the secondary and tertiary consumers in the upper trophic levels are small in number when compared to the primary consumers in the lower trophic levels. Though the eagle on level (5) will not consume the spring snails on level (2) directly in most cases, a frog from level (3) may eat 10-20 spring snails on a given day, only to be eaten along with 3-4 other small frogs by a large snake from level (4) until finally an eagle from level (5) swoops down to eat 1-2 large snakes. The reason for the tapering effect of populations and biomass in the ascending food pyramid is energy loss. The original production energy biomass coming from vegetation on base level (1) is lost at each ascending level of the trophic pyramid due to conversion of food items to carbohydrates and proteins and indigestibility of certain food parts such as seeds, husks, shells, skins, bones, etc... Supporting a healthy population of top level (5) tertiary consumers like eagles requires a stable base of level (1) primary producer vegetation like vascular plants, algae and periphyton to support level (2) primary consumers like spring snails.

The maintenance of the trophic food web’s pyramid base of vegetation requires a steady flow of spring water and stable groundwater levels. The ecosystem services provided by spring snails include feeding frogs, snakes fish and eagles among other consumers and the constant grazing of algae and periphyton. Excessive growth of certain species of algae and periphyton can clog and choke springs and their streams by depleting the water of oxygen and causing eutrophication. Thus the spring snails of the Great Basin springs, seeps and streams perform a service in both directions of the trophic food pyramid by regulating vegetation growth and providing enough food to collectively support an extensive food pyramid on their shelly backs. If the SNWA pipeline were to be constructed and their proposed amount of water were extracted, it is probable that the reduction of flow would reduce spring snail populations and result in excessive growth of algae and eventually eutrophication of the stream surrounding the spring.