Pecos River Basin Research Articles

Golden alga presence and abundance are inversely related to salinity in a high-salinity river ecosystem, Pecos River, USA

Prymnesium parvum (golden alga, GA) is a toxigenic harmful alga native to marine ecosystems that has also affected brackish inland waters. The first toxic bloom of GA in the western hemisphere occurred in the Pecos River, one of the saltiest rivers in North America. Environmental factors (water quality) associated with GA occurrence in this basin, however, have not been examined. Water quality and GA presence and abundance were determined at eight sites in the Pecos River basin with or without prior history of toxic blooms. Sampling was conducted monthly from January 2012 to July 2013. Specific conductance (salinity) varied spatiotemporally between 4408 and 73,786μS/cm. Results of graphical, principal component (PCA), and zero-inflated Poisson (ZIP) regression analyses indicated that the incidence and abundance of GA are reduced as salinity increases spatiotemporally. LOWESS regression and correlation analyses of archived data for specific conductance and GA abundance at one of the study sites retrospectively confirmed the negative association between these variables. Results of PCA also suggested that at <∼15,000μS/cm, GA was present at a relatively wide range of nutrient (nitrogen and phosphorus) concentrations whereas at higher salinity, GA was observed only at mid-to-high nutrient levels. Generally consistent with earlier studies, results of ZIP regression indicated that GA presence is positively associated with organic phosphorus and in samples where GA is present, GA abundance is positively associated with organic nitrogen and negatively associated with inorganic nitrogen. This is the first report of an inverse relation between salinity and GA presence and abundance in riverine waters and of interaction effects of salinity and nutrients in the field. These observations contribute to a more complete understanding of environmental conditions that influence GA distribution in inland waters.

Conservation Genetics of Cyprinid Fishes (Genus Dionda) in Southwestern North America. II. Expansion of the Known Range of the Manantial Roundnose Minnow, Dionda argentosa

Abstract Cyprinids belonging to the genus Dionda have a relatively broad distribution in southwestern North America. However, validity of populations in several of the nominal species has not been examined rigorously. During the course of a conservation-genetics study of Dionda in western Texas we determined that one population presumed to represent Dionda episcopa instead belongs to Dionda argentosa. This extends the native range of D. argentosa to include the lower Pecos River basin in addition to its currently recognized distribution in three tributaries of the Rio Grande. Conservation implications for both species are discussed.

Transfer of Cochliopa texana to Pyrgulopsis (Hydrobiidae) and description of a third congener from the lower Pecos River basin

The Phantom Cave snail (Cochliopa texana), a little-studied rissooidean gastropod that is locally endemic within the lower Pecos River basin (Texas) and currently a candidate for addition to the Federal list of threatened and endangered species, is redescribed and transferred to the hydrobiid genus Pyrgulopsis, based on shell and anatomical characters. Specimens from the type locality (Phantom Lake Spring) and San Solomon Spring are larger than those from East Sandia Spring and also differ somewhat in shell shape and shape of the central cusps of the lateral radular teeth. However genetic (mtCOI, NDI) variation within and among these geographically proximal (6– 13 km) populations was slight, providing no basis for the recognition of distinct conservation units of this imperiled species. We also describe Pyrgulopsis ignota n. sp., which was recently discovered in a different part of the lower Pecos River basin and initially confused with the Phantom Cave snail. These two species differ in shell shape, operculum morphology, and form and glandular ornament of the penis. They are also strongly differentiated genetically from each other and from (13) other regional congeners ( pairwise sequence divergence .6.3% for both genes). A Bayesian phylogenetic analysis of the COI and NDI dataset indicated that these two snails are not closely related and that P. ignota occupies a basal position relative to other regional congeners.

Turbidity as an Indicator of Water Quality in Diverse Watersheds of the Upper Pecos River Basin

Microbial concentrations, total suspended solids (TSS) and turbidity vary with stream hydrology and land use. Turbidity, TSS, and microbial concentrations, loads and yields from four watersheds were assessed: an unburned montane forest, a catastrophically burned montane forest, urban land use and rangeland prairie. Concentrations and loads for most water quality variables were greatest during storm events. Turbidity was an effective indicator of TSS, E. coli and Enterococci spp. The greatest threat to public health from microbial contamination occurs during storm runoff events. Efforts to manage surface runoff and erosion would likely improve water quality of the upper Pecos River basin in New Mexico, USA.

A multi-isotope (δD, δ18O, 87Sr/86Sr, and δ11B) approach for identifying saltwater intrusion and resolving groundwater evolution along the Western Caprock Escarpment of the Southern High Plains, New Mexico

Abstract Declining water levels in arid and semi-arid regions increase an aquifer’s vulnerability to natural and anthropogenic influences. A multi-isotope ( δ D, δ 18 O, 87 Sr/ 86 Sr, and δ 11 B) approach was used to resolve the geochemical evolution of groundwater in a declining aquifer in a semi-arid region of the southwestern USA as groundwater composition reacts to source-water mixing, cross-formational flow including saltwater intrusion, water–rock interaction, and likely agricultural recharge. Sub-aquifers or local flow systems are present in the Southern High Plains aquifer along the Western Caprock Escarpment in New Mexico, and the study site’s local flow system contains a Na–Cl, high dissolved-solids groundwater that flows from the escarpment until it mixes with a high quality regional aquifer or regional flow system. The local flow system contains water that is similar in composition to the underlying, upper Dockum Group aquifer. Saltwater found in the upper Dockum Group aquifer likely originates in the adjacent Pecos River Basin and crosses beneath or possibly through the hydrologic divide of the Western Caprock Escarpment. Strontium concentrations of 0.9–31 mg/L and a 87 Sr/ 86 Sr range of 0.70845–0.70906 were sufficient to estimate source-water fractions, mixing patterns, and contributions from chemical weathering through mass balance inverse calculations. Boron concentrations (59–1740 mg/L) and δ 11 B values (+6.0–+46.0‰) were used to confirm source-water mixing, further evaluate water–rock interaction, and examine the influence of possible agricultural recharge. Alteration of B concentrations and δ 11 B values in an area of likely agricultural recharge indicated the loss of B and decrease in δ 11 B values likely from plant uptake, adsorption, and weathering contributions in the soil/vadose zone prior to recharge. The effectiveness of 87 Sr/ 86 Sr and δ 11 B for resolving the geochemical influences in groundwater in the Southern High Plains along the Western Caprock Escarpment allowed for the reinterpretation of the isotopic composition of water that has been shown to be highly variable in the Southern High Plains. This study shows the utility of a multi-isotope approach for resolving the geochemical evolution of groundwater in an aquifer that has a complex relationship with underlying aquifers and the applicability of these isotopes as indicators of the alteration of source waters from natural or anthropogenic influences.

Genetic and community similarities are correlated in endemic‐rich springs of the northern Chihuahuan Desert

ABSTRACTAim Species diversity and genetic diversity within a taxon are intrinsic parts of global biodiversity. These two levels of biodiversity can show strong correlation due to a variety of reasons (i.e. parallel processes affecting both communities and populations, genotypes of a numerically or functionally dominant species affecting community composition, a species assemblage selecting for a particular genotype by affecting its selection regime). We examined correlations between species and genetic biodiversity in four isolated endemic‐rich spring systems in a hot desert and their potential link to environmental variables and physical isolation.Location Chihuahuan Desert spring systems in the Pecos River basin of New Mexico and Texas, USA.Methods We compared species richness of fish and benthic macroinvertebrate communities to within‐population allelic richness of amphipods (monophyletic Gammarus spp.) and Pecos gambusia (Gambusia nobilis) using Mantel tests. We also compared pairwise community similarities with pairwise genetic identities of populations among the same groups. We tested correlations among diversity, similarity and environmental variables after controlling for the effects of spatial distances using partial Mantel tests. We partitioned genetic and species diversity into three spatial scales (i.e. individual springs, individual spring systems, the entire region) using AMOVA and partition.Results We found strong correlations between invertebrate species richness and mosquitofish allelic richness. We found even stronger correlations of amphipod and gambusia genetic identities with fish and invertebrate community similarities; these were best explained by geographic distance rather than abiotic environmental factors. Most of the taxa and communities exhibited the largest proportion of diversity at the regional level.Main conclusions Our results suggest that drift and migration are the mechanisms that best explain our observations, and although α‐diversity among genes and species may not be strongly correlated, the pattern of species and allelic complementarity among these groups seems to be concordant at the regional level.

Genetic and morphologic variation of the Pecos assiminea, an endangered mollusk of the Rio Grande region, United States and Mexico (Caenogastropoda: Rissooidea: Assimineidae)

Assiminea pecos is an endangered species of amphibious gastropod that occupies four widely separated portions of the Rio Grande region in the southwestern United States (Pecos River basin) and northeastern Mexico (Cuatro Cienegas basin). Our statistical and discriminant function analyses of shell variation among the disjunct populations of this species indicate that Mexican specimens differ in their morphometry from those of the United States and can be diagnosed by several characters. We also analyzed variation in the mitochondrial genome by sequencing 658 bp of mitochondrial COI from populations of A. pecos, representatives of the other three North American species of Assiminea, and several outgroups. Our results indicated substantial divergence of the Mexican population of A. pecos, which was consistently depicted as a monophyletic unit nested within or sister to the shallowly structured group comprised of American members of this species. Consistent with our findings, we describe the Mexican population as a new species, which is provisionally placed in the large, worldwide genus Assiminea pending further study of the phylogentic relationships of the North American assimineids. Our molecular data suggest that the Rio Grande region assimineids, which are among the few inland members of the otherwise estuarine subfamily Assimineinae, diverged from coastal progenitors in the late Miocene, with subsequent Pleistocene vicariance of Mexican and American species perhaps associated with development of the modern, lower course of the Rio Grande.

Recent Variations in Temperature, Precipitation, and Streamflow in the Rio Grande and Pecos River Basins of New Mexico and Colorado

Trends in climatic and hydrologic data from the Rio Grande and Pecos River basin are analyzed over an approximately 40-year period (1960 to 2000). Mann-Whitney tests for changes between halves of the record and between more recent decades, and Mann-Kendall tests for trend over the 40 years of record, are applied to monthly averages from 35 temperature stations and 63 precipitation stations. Similarly, the 15 hydrometric stations meeting the criteria of the Hydro-Climatic Data Network are examined using Mann-Whitney and Mann-Kendall tests to 5-day averages of daily mean streamflow. To distinguish regions that exhibit similar patterns of climatic variation, temperature and precipitation results from the Mann-Kendall test are used as inputs to a cluster analysis. Climatic variations in the region are consistent neither through time nor across space. Some areas have demonstrated recent increases in temperature or precipitation while others have displayed decreases in these same elements. In addition, many areas reveal climatic shifts in specific periods of the year that are in marked contrast with the trends observed in other periods and other places. Hydrologic variations are also not spatially homogeneous, but generally indicate higher streamflow, earlier onset to freshet, and generally larger freshet volumes in more recent decades.

Measuring direct and indirect costs of land retirement in an irrigated river basin: A budgeting regional multiplier approach

This analysis addresses three important conceptual problems in the measurement of direct and indirect costs and benefits: (1) the distribution of impacts between a regional economy and the encompassing state economy; (2) the distinction between indirect impacts and indirect costs (IC), focusing on the dynamic time path unemployed resources follow to find alternative employment; and (3) the distinction among the affected firms' microeconomic categories of fixed and variable costs as they are used to compute regional direct and indirect costs. It uses empirical procedures that reconcile the usual measures of economic impact provided by input/output models with the estimates of economic costs and benefits required for analysis of welfare changes. The paper illustrates the relationships and magnitudes involved in the context of water policy issues facing the Pecos River Basin of New Mexico.

EFFICIENTLY MANAGING SPATIALLY COMPETING WATER USES: NEW EVIDENCE FROM A REGIONAL RECREATION DEMAND MODEL*

ABSTRACT In arid regions, managing water efficiently among competing demands depends critically on measuring comparable economic values of each end use. Unfortunately, it has been difficult to measure recreational values of water in the arid western U.S. These difficulties result from open spaces, few sites, and low incomes typical of the region. We examine whether water used for recreation can economically compete with agriculture. We accomplish this objective by extending the travel cost model to account for conditions unique to arid environments. We use demand systems theory to estimate a regional travel cost model which accounts for travel time, substitute sites, and discretionary travel cost. Findings from New Mexico's Pecos River Basin reveal recreational values of water which are 4040 percent higher than would result from conventional travel cost methodology. Measured recreation values of $130 per acre‐foot compare with equivalent values of water in irrigated agriculture of $25–$40 per acre‐foot.

Ground-water head distribution in the third dimension of the Pecos River basin, New Mexico

Ground-water head distribution in the third dimension of the Pecos River basin, New Mexico

Agricultural demand for water in the Pecos River Basin: An addendum

A study that deals with importing water to the Pecos River basin and using this water without artificial recharging (Gisser, 1970) is compared with another study that deals with the problem of recharging imported water into the aquifer (Gisser and Mercado, 1972). The sensitivity of the demand for water function to changes in salinity constraints is explored, and the possibility of reducing natural discharge of water by lowering the evaporation rate of salt cedars is investigated.

Linear Programing Models for Estimating the Agricultural Demand Function for Imported Water in the Pecos River Basin

This paper provides the results of applying parametric linear programing methods to estimate the agricultural demand function for imported water in the Pecos basin. A parametric linear programing model suitable for the Pecos basin is developed. Agricultural activities in which land is irrigated either by local or imported water and by either ditch or sprinkler irrigation are developed and adjusted for forecasted 1980 prices. These agricultural activities are used by the parametric linear programing model, and various agricultural demand functions are obtained for the Pecos basin. These functions show the expected quantities of imported irrigation water that would be demanded at different prices and under a variety of constraints.