Land–Ocean–Atmosphere Influences on Groundwater Variability in the South Atlantic–Gulf Region

Climate association between Groundwater Storage (GWS) and sea level changes have been missing from the Intergovernmental Panel on Climate Change, demanding a requisite study of their linkage and responses. Variability in the Hydrologic Unit Code—03 region, i.e., one of the major U.S. watersheds in the southeast caused by Sea Surface Temperature (SST) variability in the Pacific and Atlantic Ocean, was identified. Furthermore, the SST regions were identified to assess its relationship with GWS, sea level, precipitation, and terrestrial water storage. Temporal and spatial variability were obtained utilizing the singular value decomposition statistical method. A gridded GWS anomaly from the Gravity Recovery and Climate Experiment (GRACE) was used to understand the relationship with sea level and SST. The negative pockets of SST were negatively linked with GWS. The identification of teleconnections with groundwater may substantiate temporal patterns of groundwater variability. The results confirmed that the SST regions exhibited El Niño Southern Oscillation patterns, resulting in GWS changes. Moreover, a positive correlation between GWS and sea level was observed on the east coast in contrast to the southwestern United States. The findings highlight the importance of climate-driven changes in groundwater attributing changes in sea level. Therefore, SST could be a good predictor, possibly utilized for prior assessment of variabilities plus groundwater forecasting.

Distribution, Period of Gravidity, and Host Identification for the Narrow Pigtoe Mussel

The narrow pigtoe Fusconaia escambia is a freshwater mussel found only in the Escambia and Yellow river basins in northwest Florida and southern Alabama. It is listed as threatened under the U.S. Endangered Species Act. Like other freshwater mussels (Unionidae), its life cycle involves a larval stage (i.e., glochidial) in which most species are obligate parasites on the gills or fins of fishes. Knowledge of life history, population demographics, population genetics, and threats for the narrow pigtoe is lacking throughout its range, which impedes conservation of this species. Therefore, our objectives were to 1) compare historical and current distribution data using a conservation status assessment map, 2) determine period of gravidity, and 3) identify fish hosts. We used a conservation status assessment map to examine spatial and temporal changes in narrow pigtoe distribution and the possibility that the species has been extirpated from a subbasin (i.e., Hydrologic Unit Code level 10 watershed boundary; U.S. Geological Survey National Hydrography Dataset). Period of gravidity for the narrow pigtoe was determined by examining the gills of mussels in the field, and peak gravidity was considered to be the month in which the greatest number of gravid females was encountered. Fish hosts were determined by infecting individuals of 18 fish species with glochidia in a laboratory setting. Overall, the narrow pigtoe appears to be maintaining stable populations in Florida, but too few surveys have been conducted in Alabama subbasins for us to fully assess its status throughout its range. Peak months of gravidity were May-July, with the greatest percent of gravid females observed in May, although they were observed as early as 9 March and as late as 25 October. Nine fish species from five genera were identified as hosts for narrow pigtoe, with Blacktail Shiner Cyprinella venusta and Weed Shiner Notropis texanus consistently producing the greatest number of viable juvenile mussels. Host and gravidity findings from this study will be useful if propagation efforts become necessary for conservation of the narrow pigtoe.

Multispecies and Watershed Approaches to Freshwater Fish Conservation

<em>Abstract</em>.—Native fish conservation areas (NFCAs) are watersheds where management emphasizes proactive conservation and restoration for long-term persistence of native fish assemblages while allowing for compatible uses. Native fish conservation areas are intended to complement traditional fisheries management approaches that are often reactive to population stressors and focused on single-species conservation efforts rather than complete assemblages. We identified potential NFCAs in the upper Snake River basin above Hells Canyon Dam using a process that ranked all subwatersheds (Hydrologic Unit Code 12) and used empirical data on distribution, abundance, and genetics for three native trout species (Bull Trout <em>Salvelinus confluentus</em>, Columbia River Redband Trout <em>Oncorhynchus mykiss gairdneri</em>, and Yellowstone Cutthroat Trout <em>O. clarkii bouvieri</em>, including the fine-spotted form) and both known occurrences and modeled potential distributions of native nongame fishes. Rankings also incorporated drainage network connectivity and land-protection status (e.g., national park, wilderness). Clusters of high-ranking subwatersheds were identified as potential NFCAs that were then classified according to the presence of nongame fishes identified as species of greatest conservation need in state wildlife action plans. The Pacific Creek and Goose Creek watersheds ranked high in the upper basin (above Shoshone Falls), and Little Jacks Creek and Squaw Creek ranked high in the lower basin. We then contrasted characteristics of a select few potential NFCAs, discuss the practical implementation and benefits of NFCAs for both fishes and other aquatic species in the upper Snake River basin, examined how the NFCA approach could enhance existing conservation partnerships, and discuss how designating select watersheds as NFCAs can create higher public awareness of the value of native fishes and other aquatic species and their habitats.

Advances in Understanding Landscape Influences on Freshwater Habitats and Biological Assemblages

<i>Abstract.</i>—Fluvial threat assessments characterize the potential for fluvial habitat conditions to be degraded by differing types and intensities of anthropogenic activities occurring on the landscape, ultimately affecting stream biota. We present a threat assessment for fluvial habitats in Alaska based on six anthropogenic disturbance indices representing urbanization, agriculture/timber harvest, stream fragmentation, point-source pollution, infrastructure, and mines. These indices were combined to develop an overall index of contemporary threat of habitat alteration throughout Alaska using the 12-digit U.S. Geological Survey hydrologic unit code (HUC-12) framework (<i>n </i>= 13,997) and at a finer spatial resolution using local and network catchments for individual stream reaches within Southeast Alaska (<i>n </i>= 207,092). Overall, contemporary threat of habitat alteration indices showed that ~96% of fluvial habitats both statewide and for Southeast Alaska were at low or very low levels; however, anadromous fish habitats were under greater human pressure with nearly double the amount of moderately to severely disturbed habitats when compared to all fluvial habitats. We further evaluated potential future threats to fluvial habitats from mineral mining activities and climate change. More than 86% of existing mine claims statewide and 99% of claims in Southeast Alaska occur in areas of low and very low contemporary threat to fluvial habitats for anadromous fishes. Under climate change, July air temperatures are projected to increase ~1.9°C, on average, by mid-century within HUC-12s containing anadromous fish streams, indicating immense potential to warm streams with anadromous fishes within the state. This fluvial threat assessment demonstrates that overall threats from contemporary anthropogenic disturbance factors are generally low with localized areas of high intensity. However, future threats from mining and climate change have considerable potential to alter fluvial habitats for anadromous fishes in Alaska, particularly those currently unaltered by anthropogenic disturbances.

Past, current, and projected landscape configurational effects on streamflow within the Rocky River HUC-8 watershed of the Charlotte metropolitan region

This study examined past, current, and projected landscape configuration (LC) impacts on streamflow within a 3,553 square kilometer (km2) Hydrologic Unit Code (HUC)-8 Rocky River (RR) watershed of the Charlotte, North Carolina metropolitan region (CMR). Utilizing a monthly model, Thornthwaite Water Balance (TWB) simulations incorporating LC (blended contagion (CON)-adjusted curve numbers (CNs)) derived from two previous (2001, 2006) and one current (2011) US scale land cover/land use (LC/LU) time snapshots outperformed a blended original (ORG) CN watershed model during the 15-year (180-month) period from January 1999 to December 2013. Findings were confirmed using evaluations from several statistically based, hydrologic model performance predictors. Five-year comparisons of the 2001 time snapshot with the 2006 time snapshot and 2011 time snapshot indicated the least underestimation/overestimation of measured streamflow occurred during the 2001 time snapshot. This period had the highest measured runoff and points towards LC influences on streamflow simulation being potentially more quantifiable during periods of greater watershed precipitation. Watershed LC/LU and climatic data were also projected to the 2030 time snapshot under five different scenarios. Streamflow was projected to be about 2.6% higher in volume than what was estimated for the current (2011) time snapshot using a blended CON-adjusted TWB model.

A calibration-free, robust estimation of monthly land surface evapotranspiration rates for continental-scale hydrology

Continuous simulation of monthly evapotranspiration rates for 1979–2015 was performed by the latest, calibration-free version of the complementary relationship of evaporation over the conterminous United States. The results were compared to similar estimates of the WREVAP program and the North American Regional Reanalysis (NARR) project. Validation of the three methods was performed by the Parameter-Elevation Regressions on Independent Slopes Model precipitation and Hydrologic Unit Code level-6 runoff data. The present method outperforms the WREVAP and NARR estimates with a root-mean-square error (RMSE) of 89 mm yr−1, an R2 value of 0.87, an absolute bias (σ) of −5 mm yr−1, and slope (m) and intercept (c) values of 0.97 and 22 mm yr−1, respectively, for the best-fit line, in comparison to similar values (RMSE = 161 mm yr−1, R2 = 0.8, σ = 124 yr–1 mm yr−1, m = 0.88, c = 191 mm yr−1; and RMSE = 195 mm yr−1, R2 = 0.81, σ = 146 mm yr−1, m = 1.05, c = 120 mm yr−1) of the latter two methods. The value of the Priestley–Taylor (PT) coefficient was determined by inversion of the PT-equation via a model-independent identification of wet cells and their estimated surface temperatures.