Semiarid Southwestern United States Research Articles

A Modified Rational Method Approach for Calculating First Flush Design Flow Rates to Mitigate Nonpoint Source Pollution from Stormwater Runoff

Mitigating nonpoint source pollution from stormwater runoff demands effective strategies for treating the first flush depth. Whether through off-stream storage or pass-through treatment devices, designing diversion structures and filtering materials is critical. This study proposes a streamlined procedure for determining first flush design flow rates, employing the modified rational method and rainfall intensity–duration equations applicable to any U.S. location. The dimensionless solution, which is presented as an equation requiring an iterative calculation for the desired flow rates, is complemented by precision graphs. Examples from the semi-arid Southwestern United States illustrate the methodology’s utility.

Seasonal Storm Characteristics Govern Urban Flash Floods: Insights from the Arid Las Vegas Wash Watershed

Abstract In the arid and semiarid southwestern United States, both cool- and warm-season storms result in flash flooding, although the former storms have been much less studied. Here, we investigate a catalog of 52 flash-flood-producing storms over the 1996–2021 period for the arid Las Vegas Wash watershed using rain gauge observations, reanalysis fields, radar reflectivities, cloud-to-ground lightning flashes, and streamflow records. Our analyses focus on the hydroclimatology, convective intensity, and evolution of these storms. At the synoptic scale, cool-season storms are associated with open wave and cutoff low weather patterns, whereas warm-season storms are linked to classic and troughing North American monsoon (NAM) patterns. At the storm scale, cool-season events are southwesterly and southeasterly under open wave and cutoff low conditions, respectively, with long duration and low to moderate rainfall intensity. Warm-season storms, however, are characterized by short-duration, high-intensity rainfall, with either no apparent direction or southwesterly under classic and troughing NAM patterns, respectively. Atmospheric rivers and deep convection are the principal agents for the extreme rainfall and upper-tail flash floods in cool and warm seasons, respectively. Additionally, intense rainfall over the developed low valley is imperative for urban flash flooding. The evolution properties of seasonal storms and the resulting streamflows show that peak flows of comparable magnitude are “intensity driven” in the warm season but “volume driven” in the cool season. Furthermore, the distinctive impacts of complex terrain and climate change on rainfall properties are discussed with respect to storm seasonality.

Impact of urbanization and stormwater infrastructure on ephemeral channel transmission loss in a semiarid watershed

Study regionMontoyas watershed in central New Mexico, a rapidly urbanizing basin characteristic for the semiarid Southwestern United States. The 142 km2 watershed drains to the Rio Grande. Study focusThis study evaluated the impacts of urbanization and stormwater infrastructure on ephemeral channel transmission loss (TL), an important source of groundwater recharge in dryland basins. A hydrologic model (HEC-HMS) was built for the watershed and calibrated based on seven years of precipitation and discharge data. The model was then used to simulate the individual and combined impacts of land use change (urbanization) and stormwater infrastructure (ponds, channel lining) on runoff and transmission losses over a ten-year period based on observed storm events. New hydrological insights for the regionResults show high inter-annual runoff variability with the two wettest years contributing 44–59% of the 10-year total, and dry years resulting in nearly no flow. Both runoff and TL increased with urbanization. Assuming natural ephemeral channels, TL comprised 64–81% of runoff reaching the basin outlet and 7–10% of domestic water use in the basin, depending on urbanization scenario. Stormwater detention ponds had minimal impact on TL; however, lining the lower 5, 10 and 15 km of ephemeral streams reduced TL by 31%, 55% and 73% over the ten-year study period. Results indicate that preservation of ephemeral channels, in particular permeable channel beds, should be considered a viable strategy for managed aquifer recharge in urbanizing areas.

Yield Potential and Water Use Efficiency of Alternate Rotation Crops in the Semiarid Environment of Southwestern United States

Highlights Water use efficiency and yield potential of 10 rotation crops were tested under dryland and fully irrigated conditions. Pearl millet in grasses, cowpea and sesbania in legumes had great potential as rotation crops with greater yields and WUEs. Irrigation improved water use efficiency of crops compared to dryland conditions. Abstract. Unpredictability in weather patterns prompted a need for testing diverse crops with broad range adaptability to introduce into the existing cropping systems or to innovate alternate cropping systems in the southwestern United States. Such crops suitable for system integration should preferably be dual-purpose and resource-use efficient. Keeping this in view, a two-year study was conducted at NMSU Rex E. Kirksey Agricultural Science Center, Tucumcari, New Mexico, comprised of 10 annual crop species including grasses, legumes, and oilseed crops. The study aimed at researching yield potential and water use efficiency of the selected crops under dryland and limited irrigated conditions in the semiarid, subtropical environment. Results suggest that both crop species and water regime (irrigated vs. dryland) had significant effects on seed and biomass yield and water use efficiencies (WUE) (P<0.05). Seed and biomass production under dryland conditions were significantly influenced each year by amount of precipitation received. Pearl millet [Pennisetum glaucum (L.) R. Br.] had consistently greater seed and biomass yields and WUEs than the other crops. Cowpea (Vigna unguiculata) and sesbania (Sesbania sesban) proved to be viable legumes with the advantage of greater biomass yields and water-use efficiency (WUEs) compared to other the legumes tested (P<0.05). For a balanced livestock diet, pearl millet+cowpea intercrop combination is a good option with greater yields and WUEs. Integrating these rotation crops into the traditional winter wheat cropping systems or alternate cropping systems may provide a significant benefit to producers in the semiarid southwestern United States. Keywords: Alternate crops, Summer rotation, Water-use efficiency, Yield potential.

Exploring conceptual models of infiltration and groundwater recharge on an intermittent river: The role of geologic controls

Study regionThis study is along an intermittent reach of the Alamosa River in the San Luis Valley of south-central Colorado, a river that is typical of the semi-arid southwestern United States with respect to climate, land use, and the impacts of upstream dam regulation. Study focusWe use conceptual steady-state models to identify geologic factors that may control water loss through infiltration. These conceptual models are parameterized according to a range of conditions observed from stream discharge, topographic data, geologic data, and drone magnetometer data. New hydrological insightsThe introduction of a fault, variation in the alluvial aquifer hydraulic conductivity, and presence or absence of a confining unit in the numerical models were the primary geologic controls that affected infiltration across the study reach. Conversely, variation in the thickness of the streambed had little impact. This information may help determine future data collection within this and similar semi-arid regions where rivers are controlled by a combination of surface water availability (e.g. through dam regulation) and complex subsurface geology, which are often not well constrained.

Rainwater as a renewable resource to achieve net zero urban water in water stressed cities

Globally, cities are facing increased water stress with an imbalance between available water resources and projected urban water demands. Water experts have pointed to rainwater harvesting (RWH) as one answer; however, the capacity of such a solution to address deficits on an urban scale is largely untested. This study proposes a model to evaluate the necessary network of RWH systems to achieve net zero urban water, meaning a sustainable local supply capable of meeting long-term demand. This approach was applied to a water stressed city, Tucson, Arizona, in the semi-arid Southwestern United States. A daily water balance model optimized for the smallest required storage volumes to reach net zero urban water at a resolution of ten years of consecutive daily rainfall. The potential passive and active RWH network was modelled under four investment scenarios using remote sensing, localized daily rainfall, and municipal water meter data. In the most financially and physically plausible scenario, rainwater replaced imported water and a 30% demand conservation was assumed. The median required storage was 28.2 cubic-meters per 100 square-meters of roof area, or an estimated $10,000 investment. Comparatively, the median RWH household storage installation in Tucson is 5.3 cubic-meters (1395 gallons). In addition to widespread investment in large household storage, this result would require paradigm shifts across built, economic, and social systems to fully integrate the decentralized network across the urban fabric. This study shows that net zero urban water can be achieved with RWH under multiyear drought conditions with large storage volumes.

Municipal Water Consumption and Urban Economic Growth in El Paso

This study investigates the nexus between municipal water consumption and economic growth for El Paso, TX, USA. Located in the semi-arid southwestern United States, El Paso water consumption has been the subject of prior economic studies. However, the relationship between water consumption and economic growth has not been previously analyzed for El Paso or any other metropolitan economies in the region. Empirical results indicate that municipal water usage and real personal income are integrated of order one, but are not co-integrated. Given that, a vector autoregression model is estimated and a Granger causality test is performed. Estimation results show unidirectional causation from real income growth to water consumption, indicating that water conservation policies will not inhibit economic growth in this urban economy.

Property, Unbundled Water Entitlements, and Anticommons Tragedies: A Cautionary Tale From Australia

As water becomes an increasingly scarce resource, a lack of clarity in relation to its use can produce both conflict among and inefficient use by users. In order to encourage markets in water and to ensure the viability and functionality of those markets, governments in many jurisdictions have moved away from commons property as a means of water allocation, and towards systems of private property in water. In doing so, one policy and legal option is “unbundling”, which seeks carefully to define both the entitlement to water and its separation into constituent parts. Advocates claim that unbundling makes water rights easier to value, monitor, and trade. But is unbundling the most efficient means of allocating water use rights? Or might such fragmentation produce what has come to be called an “anticommons tragedy”? To answer these questions, this article contains four parts. The Introduction provides the legal background to the modern means of allocating the use of water amongst competing, or rivalrous, users. Part I considers the theoretical nature of property, and the way in which such theory might be extended to water allocation through unbundling. Part II presents unbundling as it has been implemented in the Australian state of South Australia. This allows us to assess the extent to which the stated policy rationale for unbundling—certainty and transferability of entitlements—has been achieved and the extent to which this is a desirable outcome. Our analysis can be applied to any jurisdiction, most notably the arid and semi-arid southwestern United States, considering unbundling as a legal and policy option for the allocation of water use. The Conclusion reflects upon the potential for unbundling water entitlements in arid or semi-arid environments. The South Australian experience reveals a reluctance to embrace unbundling, both on the part of the state in terms of implementing, and on the part of market actors holding existing proprietary interests in water. This reluctance ought to be viewed by other jurisdictions as a warning about the effectiveness and efficiency of unbundling. We show that unbundling efforts may not only fail to provide efficiency gains, but also, and much more worryingly, may in fact drive anticommons tragedies that entirely inhibit any beneficial use. We propose that our anecdotal and theoretical analysis of South Australia requires empirical research both in Australia and in other jurisdictions climatologically, hydrologically, and in underlying legal framework, similar to Australia. Such empirical research will test our conclusions in relation to South Australia, both in respect to the operation of the water market and as to the behavior of market actors.

Crop Vulnerability to Weather and Climate Risk: Analysis of Interacting Systems and Adaptation Efficacy for Sustainable Crop Production

Climate change is increasing mean and extreme temperatures in the Southwestern United States, leading to a suite of changes affecting agricultural production. These include changes in water, soils, pathogens, weeds, and pests comprising the production environment. The aim of this synthesis is to describe the anticipated leading agricultural pressures and adaptive responses, many of which are near-term actions with longer-term consequences. In the semiarid Southwestern United States, climate change is expected to increase water scarcity. Surface water shortage is the leading reason for recent diminished crop yields in the Southwest. Drought and lack of water represent the leading regional weather-related cause of crop loss from 1989 to 2017. Thus, water scarcity has been and will continue to be a critical factor leading to regional crop vulnerability. Soils, pathogens, weeds, and insects are components of the agricultural production environment and are directly influenced by near-term weather and long-term climate conditions. Field crops, vegetable crops, and perennial crops have unique production requirements and diverse management options, many already used in farm management, to cope with production environment changes to build climate resilience. Farmers and ranchers continuously respond to changing conditions on a near-term basis. Long-term planning and novel adaptation measures implemented may now build nimble and responsive systems and communities able to cope with future conditions. While decision-support tools and resources are providing increasingly sophisticated approaches to cope with production in the 21st century, we strive to keep pace with the cascading barrage of inter-connected agricultural challenges.

Tree Irrigation Requirements in the Semiarid Southwestern United States

Several large cities in the southwestern United States have set a target to increase their tree canopy cover up to 25%, which often requires more than doubling the current canopy cover. A major goal is to alleviate high temperatures and support public health in addition to gaining all the other benefits conferred by urban forests. Rising temperatures, the arid climate, continued drought, increasing population numbers, and the growing urban forest in the southwestern United States fuel the demand for more water. Using water wisely to garner the benefits of trees requires the application of sufficient irrigation based on the water needs of different species. Current irrigation recommendations for trees are often based on expert consensus. Research-based results of tree irrigation studies from the southwestern United States are presented to give specific examples of how trees respond when they are exposed to different irrigation regimes.

Sodium Chloride Effects on Seed Germination, Growth, and Water Use of Lepidium alyssoides, L. draba, and L. latifolium: Traits of Resistance and Implications for Invasiveness on Saline Soils

In the semiarid southwestern United States, long-term drought, soil salinity, and land-use intensification have increased the risk of invasive plants that threatens landscape biodiversity. Soil-related factors that regulate plant invasions are not adequately known. We evaluated the salinity responses of three invasive plant species during a 3-mo plant growth period in a greenhouse and during a 2–wk seed germination study in the laboratory. The species included the indigenous Lepidium alyssoides A. Gray var. alyssoides (mesa pepperwort) and the exotic, invasive L. draba L. (whitetop) and L. latifolium L. (perennial pepperweed). A NaCl solution at –0.2 MPa reduced germination of L. alyssoides by ≈20% and had no effect on germination of L. draba and L. latifolium, merely delaying their mean germination time by a day or less. Reductions in seedling dry matter production and evapotranspiration (ET) were observed following irrigation with NaCl solutions at –0.1 MPa and –0.2 MPa. However, on the basis of ET and total plant dry matter production under common experimental conditions, the salt resistance of these species greatly exceeded that of salt sensitive bean (Phaseolus vulgaris L.) and equaled or exceeded that of salt-resistant cotton (Gossypium hirsutum L.). Below-ground propagating structures giving rise to clonal shoots were observed for all Lepidium spp., consistent with other reports. The results indicate that vegetative propagule pressure and relatively high resistance to salinity at germination and seedling growth stages could contribute to the invasiveness of these species under saline conditions. A broader impact of the findings is in their application to the larger diversity of invasive species to aid in the understanding of soil salinity and how it may govern plant invasions. This dataset could improve risk assessment measures to favor biodiversity in rangelands and natural ecosystems of semiarid regions.

Irrigation with brackish water changes evapotranspiration, growth and ion uptake of halophytes

Water shortage due to low precipitation, less river flows and high evaporation, and salinity stress related to use of brackish groundwater for irrigation are prevalent in the arid and semi-arid southwestern United States. The brackish groundwater desalinated using a reverse osmosis (RO) system produces a highly concentrate waste and creates a disposal problem. The objectives of this greenhouse study in pots were to assess irrigation water salinity induced changes to the evapotranspiration (ET), volumetric leaching fractions (LF), soil salinity, and dry biomass yields of two halophyte species (Hordeum vulgare, and xTriticosecale). Plants were arranged in a completely randomized design and four irrigation treatments (EC=0.8, 5, 8 and 10dS/m) were applied for 90days during the two seasons. No significant differences were observed in the saturated hydraulic conductivity and soil water retention of sandy loam soil irrigated with different brackish waters. Total ET obtained from water balance was higher for plants irrigated with control than brackish waters only in season one. An increase in irrigation water salinity increased soil salinity and mean leaching fraction (LF) while mean ET decreased. There were no differences in dry biomass yield for both species in season 1, and very small differences in season 2. The sodium uptake primarily from irrigation water confirmed that both species were halophyte, can be grown with RO concentrate, and used as a salt substitute in animal fodder. However, in order to prevent soil salinization, RO irrigation should be done intermittently or until vegetation establishment in nonagricultural areas.

Salinity an Environmental “Filter” Selecting for Plant Invasiveness? Evidence from Indigenous Lepidium alyssoides on Chihuahuan Desert Shrublands

A better understanding of site-specific factors such as soil salinity that regulate plant invasions is needed. We conducted a 3-mo greenhouse study to evaluate the salinity responses of three local maternal sources of Lepidium alyssoides, which is an indigenous species shown to aggressively colonize disturbed shrubland sites in the southwestern United States, including those affected by high salinity and sodicity. Results indicated that there were little or no population effects on plant evapotranspiration (ET), growth, and tissue Na and Cl concentrations. Significant reductions in seedling growth and ET were largely independent of various isosmotic saline irrigation solutions that included NaCl, Na2SO4, and CaCl2, each at −0.1 MPa and −0.2 MPa, suggesting that ET and growth were controlled by solution osmotic potential. The combined Na and Cl concentrations in leaves were 9–10% of dry weight with no visible sign of injury. However, increasing leaf mortality and abscission as a proportion of total leaf production was observed in the high-salt treatments (−0.2 MPa), with a combined Na and Cl concentration reaching 16% with high NaCl. Under saline conditions, considerable foliage salt loads of this species could deposit high-salt litter to potentially alter a landscape to its own favor and to the detriment of other salt-sensitive species. Results of this study add to a limited quantitative database on site-specific salinity factors governing plant invasions by showing the potential for these populations to behave invasively under saline conditions and, thus, potential for soil salinity assessment to predict incipient populations. However, due to its halophytic traits and indigenous status, L. alyssoides may alternatively provide ecosystem services to salinized shrublands of the arid and semiarid southwestern United States.

EFFECT OF PROTEIN ADDITION ON PROPERTIES OF GUAYULE NATURAL RUBBER

ABSTRACTParthenium argentatum, commonly known as guayule, is a desert shrub cultivated as a domestic source of natural rubber in the semi-arid southwestern United States. Guayule natural rubber (GR) may be used to replace petroleum-based rubber or in place of Hevea natural rubber (NR), but substitution must take into consideration differences in physical and chemical properties. Currently, Hevea NR is required in tire applications, especially aircraft and truck tires, because of its high oxidative resistance, rapid cure rate, and exceptional stress–strain response. These outstanding features are attributed to the presence of nonrubber constituents, mainly proteins and lipids, which cause the rubber to gel, and they contribute to strain-induced crystallization. In contrast, GR is low in proteins and is thus deprived of some attributes of Hevea. Addition of amino acids and proteins to guayule could potentially improve performance and thereby widen the range of applications for use. In a previous study, amino acids blended with GR latex improved thermo-oxidative stability, served as plasticizers and cure accelerators, and enhanced green strength slightly, but tensile strength was not improved. Here, a series of bio-based commercial proteins (gelatin, soy, albumin, casein, zein, gliadin, and gluten) were added to GR as a latex blend. In general, protein addition reduced bulk viscosity and improved thermo-oxidative stability. The gel content and green strength of the polymer–protein blends were increased, with the exception of gliadin, but not to levels observed for Hevea. Effects on vulcanization and mechanical properties in compounds were surprisingly influenced by the choice of antioxidants used. Our results demonstrate the potential of proteins as bio-based rubber compounding additives.

Physiologic response of six plant species grown in two contrasting soils and irrigated with brackish groundwater and RO concentrate

ABSTRACTWith declining availability of fresh surface water, brackish groundwater is increasingly used for irrigation in the arid and semi-arid southwestern United States. Brackish water can be desalinated by reverse osmosis (RO) but RO results in a highly saline concentrate. Disposal of concentrate is a major problem hindering augmentation of inland desalination in arid areas. The objective of this study was to determine the effect of texture and saline water irrigation on the physiology of six species (Atriplex canescens (Pursh) Nutt., Hordeum vulgare L., Lepidium alyssoides A. Gray, Distichlis stricta (L.) Greene, Panicum virgatum L., and ×Triticosecale Wittm. ex A. Camus [Secale × Triticum]). All species were grown in two contrasting soils and irrigated with the same volume of control water (EC 0.9 dS/m), brackish groundwater (4.1 dS/m), RO concentrate (EC 8.0 dS/m). Several plant physiological measurements were made during the growing season including height, number of stem nodes, average internodal length, number of leaves, leaf length, photosynthetic rates, stomatal conductance rates, transpiration rates, leaf temperatures, stem water potential, and osmotic potential. P. virgatum was the only species that showed significant decrease in plant height and growth with texture and irrigation water salinity. Except for A. canescens and L. alyssoides, number and length of leaves decreased with increasing salinity for all species. No significant differences were observed for photosynthetic, stomatal conductance, and transpiration rates by soil texture or irrigation water salinity. Stem water potential and osmotic potential did show some significant influence by soil texture and irrigation water salinity. Based on the results, RO concentrate can be reused to grow all six species in sand; however, growth of all species showed some limitations in clay. Local reuse of RO concentrate along desert margins with regular soil and environmental quality monitoring can accelerate implementation of inland desalination for sustaining food security.

Divergent responses of vegetation cover in Southwestern US ecosystems to dry and wet years at different elevations

In the semiarid Southwestern United States, prolonged drought conditions since the early 2000s have resulted in widespread declines of the vegetation productivity in this water-constrained ecosystem, as revealed by analyses of the Normalized Difference Vegetation Index (NDVI). However, the spatial pattern of the NDVI response to dry years is not uniform: a divergent response of NDVI to precipitation is observed between the low-lying desert and the high montane forests at elevations above 2,500 meter. We analyzed relationships between 15 years of Moderate Resolution Imaging Spectroradiometer (MODIS) NDVI and gridded climate data (PRISM) along elevation gradients at scales from regional to local. Our elevation-explicit analysis captures the transition from water-limited to temperature-limited ecosystems, with a sign-reversal in the correlation coefficient between precipitation and NDVI observed at about 2,500-3,000m altitude. We suggest warmer temperatures and less snow cover associated with drier years as explanations for high elevation gains in vegetation productivity during dry years.

The Impact of Climate Change on Agriculture in the Southwestern United States: The Ricardian Approach Revisited

This paper estimates a Ricardian model of farmland value across the counties of the semiarid Southwestern United States. Compared to previous contributions, we focus on one climate zone and include the presence of extreme weather events and of farm subsidies in our analysis. We also control for heterogeneity and for various types of spillover effects. Once calibrated, the model is used to project changes due to future climate conditions. We find that the probability of a decrease is great in highland counties while an increase or decrease is equally probable in lowland counties where climate impacts farmland value less.

Soil Solarization in High Tunnels in the Semiarid Southwestern United States

High tunnels are unheated structures covered with polyethylene (PE) glazing to protect high-value crops from adverse weather. The objective of this study was to raise soil temperatures to determine the efficacy of soil solarization using clear mulch on the soil surface and glazing or no glazing on a high tunnel during the hottest months of the year in the semiarid southwestern United States. Solarization trials were conducted in May and June 2013 in two high tunnels in southern Arizona. Highest soil temperatures were reached with the combination of a high tunnel covered with glazing and the soil covered with PE mulch. Average daily soil temperatures were 48 and 47 °C and average degree hours (DH) per day (base temperature 45 °C) were over 14 at soil depths of 5 and 15 cm. The average daily maximum soil temperature at 5- and 15-cm depth was 63.4 and 52 °C, respectively. The second highest soil temperatures were reached when the soil was covered with PE mulch without high tunnel glazing, which resulted per day in 5.2 DH above 45 °C at 5 cm and less than one DH at 15-cm depth. Glazing on the high tunnel without covering the soil surface raised soil temperatures only at the 5-cm depth above 45 °C, but not further down. High tunnel producers in the low desert areas in the southwestern United States can complete solarization in less than 1 week, depending on the organism to be controlled, when the soil is fallow during the summer months with glazing on the high tunnel and on the soil surface.

The effect of modeled recharge distribution on simulated groundwater availability and capture.

Simulating groundwater flow in basin-fill aquifers of the semiarid southwestern United States commonly requires decisions about how to distribute aquifer recharge. Precipitation can recharge basin-fill aquifers by direct infiltration and transport through faults and fractures in the high-elevation areas, by flowing overland through high-elevation areas to infiltrate at basin-fill margins along mountain fronts, by flowing overland to infiltrate along ephemeral channels that often traverse basins in the area, or by some combination of these processes. The importance of accurately simulating recharge distributions is a current topic of discussion among hydrologists and water managers in the region, but no comparative study has been performed to analyze the effects of different recharge distributions on groundwater simulations. This study investigates the importance of the distribution of aquifer recharge in simulating regional groundwater flow in basin-fill aquifers by calibrating a groundwater-flow model to four different recharge distributions, all with the same total amount of recharge. Similarities are seen in results from steady-state models for optimized hydraulic conductivity values, fit of simulated to observed hydraulic heads, and composite scaled sensitivities of conductivity parameter zones. Transient simulations with hypothetical storage properties and pumping rates produce similar capture rates and storage change results, but differences are noted in the rate of drawdown at some well locations owing to the differences in optimized hydraulic conductivity. Depending on whether the purpose of the groundwater model is to simulate changes in groundwater levels or changes in storage and capture, the distribution of aquifer recharge may or may not be of primary importance.

Estimating survival rates of quagga mussel (Dreissena rostriformis bugensis) veliger larvae under summer and autumn temperature regimes in residual water of trailered watercraft at Lake Mead, USA

On 6 January 2007, invasive quagga mussels (Dreissena rostriformis bugensis (Andrusov, 1897)) were discovered in the Boulder Basin of Lake Mead, Nevada, a popular site for recreational boating in the southwestern United States. Recreational watercraft are considered a primary vector for overland dispersal of quagga mussel veliger larvae between water bodies. Thus, effective decontamination of veligers in residual water carried by trailered recreation boats is critical to controlling this species' spread. The survival rate of quagga mussel veligers was measured during exposure to environmental temperature conditions mimicking those experienced in the residual water of trailered vessels during warm summer and cooler autumn months in the semi-arid southwestern United States. Under warm summer conditions, quagga mussel veligers survived approximately five days while under cooler autumn conditions they survived 27 days. When tested under autumn temperature conditions veliger survival times increased with increased level of larval development. The results suggested a greater likelihood of veliger transport in the residual water of trailered watercraft during autumn months. The results indicated that presently recommended vessel quarantine times to kill all externally attached juvenile and adult dreissenid mussels prior to launching in an uninfested water body should be increased to generate 100% veliger mortality in residual water unable to be fully drained from the internal areas of watercraft.