Geology topics

Research about Puerto Rico

Source-linked reports with geographic coverage including Puerto Rico.

At least 127 records · Page 7Linked to original sources

USGS2017

The effects of forest cover on base flow of streams in the mountainous interior of Puerto Rico, 2010

The U.S. Geological Survey, in cooperation with the Puerto Rico Department of Natural and Environmental Resources, completed a study to determine whether a relation exists between the extent of forest cover and the magnitude of base flow at two sets of paired drainage basins in the highlands of the municipalities of Adjuntas and Utuado within the mountainous interior of Puerto Rico. One set of paired basins includes the Río Guaónica and Río Tanamá, both tributaries of the Río Grande de Arecibo. The other set includes two smaller basins in the drainage basin of the Río Coabey, which is a tributary of the Río Tanamá. The paired basins in each set have similar rainfall patterns, geologic substrate, and aspect; the principal difference identified in the study is the extent of forest cover and related land uses such as the cultivation of shade and sun coffee. Data describing the hydrology, hydrogeology, and streamflow were used in the analysis. The principal objective of the study was to compare base flow per unit area among basins having different areal extents of forest cover and land uses such as shade coffee and sun coffee cultivation. Within the mountainous interior of Puerto Rico, a substantial amount of the annual rainfall (45 to 39 percent in the Rio Guaónica and Rio Tanamá, respectively) can migrate to the subsurface and later emerge as base flow in streams. The magnitude of base flow within the two sets of paired basins varies seasonally. Minimum base flows occur during the annual dry season (generally from January to March), and maximum base flows occur during the wet season (generally from August to October). During the dry season or periods of below-normal rainfall, base flow is either the primary or the sole component of streamflow. Daily mean base flow ranged from 3.2 to 20.5 cubic feet per second (ft3 /s) at the Rio Guaónica Basin, and from 4.2 to 23.0 ft3 /s at the Rio Tanamá Basin. The daily mean base flows during 2010 ranged from 0.28 to 0.98 ft3 /s at Tributary 1 and from 0.22 to 0.58 ft3 /s at Tributary 2 of the Rio Coabey. The normalized daily base flow at the Río Guaónica and Río Tanamá Basin during 2010 ranged from 1.3 to 8.1 cubic feet per second per square mile (ft3 /s)/mi2 and from 1.1 to 6.1 (ft3 /s)/mi2 , respectively. The normalized daily base flow for the basins of Tributary 1 and Tributary 2 of Río Coabey during 2010 ranged from 1.0 to 3.6 (ft3 /s)/mi2 and from 1.5 to 3.9 (ft3 /s)/mi2 , respectively. The normalized mean annual base flow is similar within the larger paired basins of Río Tanamá (2.74 [ft3 /s]/mi2 ) and Río Guaónica (3.15 [ft3 /s]/mi2 ). The mean annual base flow per unit area for both of these basins is about 79 percent of the mean annual streamflow. In the large paired basins, the proportion of Type I land use (forest patches, shade and mixed shade/sun coffee with associated cash crops) is substantially higher in Rio Guaónica Basin (81 percent) than in the Rio Tanamá Basin (59 percent), and the base flow per unit area is also higher. In the small paired basins of Rio Coabey, the proportion of Type I land use is much higher at Tributary 1 (52 percent) than at Tributary 2 (15 percent), but, in contrast to the large basins, the mean annual base flow per unit area is lower (2.22 and 2.62 [ft3 /s]/mi2 , respectively). There is no consistent relation between land use and normalized base flow between the two sets of paired basins in the study.

Scientific Investigations Report↗

USGS2017

Twentieth century warming of the tropical Atlantic captured by Sr-U paleothermometry

Coral skeletons are valuable archives of past ocean conditions. However, interpretation of coral paleotemperature records is confounded by uncertainties associated with single-element ratio thermometers, including Sr/Ca. A new approach, Sr-U, uses U/Ca to constrain the influence of Rayleigh fractionation on Sr/Ca. Here we build on the initial Pacific Porites Sr-U calibration to include multiple Atlantic and Pacific coral genera from multiple coral reef locations spanning a temperature range of 23.15–30.12°C. Accounting for the wintertime growth cessation of one Bermuda coral, we show that Sr-U is strongly correlated with the average water temperature at each location ( r 2 = 0.91, P < 0.001, n = 19). We applied the multispecies spatial calibration between Sr-U and temperature to reconstruct a 96 year long temperature record at Mona Island, Puerto Rico, using a coral not included in the calibration. Average Sr-U derived temperature for the period 1900–1996 is within 0.12°C of the average instrumental temperature at this site and captures the twentieth century warming trend of 0.06°C per decade. Sr-U also captures the timing of multiyear variability but with higher amplitude than implied by the instrumental data. Mean Sr-U temperatures and patterns of multiyear variability were replicated in a second coral in the same grid box. Conversely, Sr/Ca records from the same two corals were inconsistent with each other and failed to capture absolute sea temperatures, timing of multiyear variability, or the twentieth century warming trend. Our results suggest that coral Sr-U paleothermometry is a promising new tool for reconstruction of past ocean temperatures.

Puerto Rico↗

USGS2017

Lithological influences on contemporary and long-term regolith weathering at the Luquillo Critical Zone Observatory

Lithologic differences give rise to the differential weatherability of the Earth’s surface and globally variable silicate weathering fluxes, which provide an important negative feedback on climate over geologic timescales. To isolate the influence of lithology on weathering rates and mechanisms, we compare two nearby catchments in the Luquillo Critical Zone Observatory in Puerto Rico, which have similar climate history, relief and vegetation, but differ in bedrock lithology. Regolith and pore water samples with depth were collected from two ridgetops and at three sites along a slope transect in the volcaniclastic Bisley catchment and compared to existing data from the granitic Río Icacos catchment. The depth variations of solid-state and pore water chemistry and quantitative mineralogy were used to calculate mass transfer (tau) and weathering solute profiles, which in turn were used to determine weathering mechanisms and to estimate weathering rates. Regolith formed on both lithologies is highly leached of most labile elements, although Mg and K are less depleted in the granitic than in the volcaniclastic profiles, reflecting residual biotite in the granitic regolith not present in the volcaniclastics. Profiles of both lithologies that terminate at bedrock corestones are less weathered at depth, near the rock-regolith interfaces. Mg fluxes in the volcaniclastics derive primarily from dissolution of chlorite near the rock-regolith interface and from dissolution of illite and secondary phases in the upper regolith, whereas in the granitic profile, Mg and K fluxes derive from biotite dissolution. Long-term mineral dissolution rates and weathering fluxes were determined by integrating mass losses over the thickness of solid-state weathering fronts, and are therefore averages over the timescale of regolith development. Resulting long-term dissolution rates for minerals in the volcaniclastic regolith include chlorite: 8.9 × 10 −14 mol m −2 s −1 , illite: 2.1 × 10 −14 mol m −2 s −1 and kaolinite: 4.0 × 10 −14 mol m −2 s −1 . Long-term weathering fluxes are several orders of magnitude lower in the granitic regolith than in the volcaniclastic, despite higher abundances of several elements in the granitic regolith. Contemporary weathering fluxes were determined from net (rain-corrected) solute profiles and thus represent rates over the residence time of water in the regolith. Contemporary weathering fluxes within the granitic regolith are similar to the long-term fluxes. In contrast, the long-term fluxes are faster than the contemporary fluxes in the volcaniclastic regolith. Contemporary fluxes in the granitic regolith are generally also slightly faster than in the volcaniclastic. The differences in weathering fluxes over space and time between these two watersheds indicate significant lithologic control of chemical weathering mechanisms and rates.

Bisley watersheds↗

USGS2017

Projecting impacts of climate change on water availability using artificial neural network techniques

Lago Loíza reservoir in east-central Puerto Rico is one of the primary sources of public water supply for the San Juan metropolitan area. To evaluate and predict the Lago Loíza water budget, an artificial neural network (ANN) technique is trained to predict river inflows. A method is developed to combine ANN-predicted daily flows with ANN-predicted 30-day cumulative flows to improve flow estimates. The ANN application trains well for representing 2007–2012 and the drier 1994–1997 periods. Rainfall data downscaled from global circulation model (GCM) simulations are used to predict 2050–2055 conditions. Evapotranspiration is estimated with the Hargreaves equation using minimum and maximum air temperatures from the downscaled GCM data. These simulated 2050–2055 river flows are input to a water budget formulation for the Lago Loíza reservoir for comparison with 2007–2012. The ANN scenarios require far less computational effort than a numerical model application, yet produce results with sufficient accuracy to evaluate and compare hydrologic scenarios. This hydrologic tool will be useful for future evaluations of the Lago Loíza reservoir and water supply to the San Juan metropolitan area.

Puerto Rico↗

USGS2017

Recruitment phenology and pelagic larval duration in Caribbean amphidromous fishes

Amphidromous fishes are major components of oceanic tropical island stream ecosystems, such as those of the Caribbean island, Puerto Rico. Fishes with this life history face threats related to the requirement for connectivity between freshwater and marine environments during early life stages. Pelagic larval duration and recruitment phenology are 2 early life-history processes that are crucial for the biology, ecology, conservation, and management of amphidromous fishes. However, these processes are understudied in the Caribbean in general and have never been quantified in Puerto Rico. We quantified recruit abundance, recruitment phenology, and pelagic larval duration of several Caribbean amphidromous fish species in multiple rivers in Puerto Rico and explored the effects of environmental variables on recruit abundances. Two fish taxa—sirajo goby ( Sicydium spp.) and River Goby ( Awaous banana )—were exceptionally abundant as postlarvae and recruited to Caribbean rivers in pulsed migration episodes that were periodic at annual and lunar scales. Sirajo goby and River Goby recruit abundances varied among rivers, were greater at sunrise than at sunset, and were positively related to river discharge. The pelagic larval duration of 4 fish taxa ranged from a minimum of 28 d to a maximum of 103 d with means between 43 ± 7 d (SD) and 65 ± 11 d. We identified the last-quarter moon phase during the months of June through January as periods of maximum amphidromous fish recruitment to freshwater streams. The results and conclusions of our study can be applied to identify critical times to maintain river–ocean connectivity and stream flow for the benefit of the amphidromous fish population dynamics, stream ecology, and natural resources of the Caribbean.

Puerto Rico↗

USGS2017

White-cheeked Pintail duckling and brood survival across wetland types at Humacao Nature Reserve, Puerto Rico

Duckling survival is an important influence on recruitment in several North American Anas species. White-cheeked Pintail ( Anas bahamensis ) breeding in Puerto Rico encounter a variety of wetland types that may influence duckling survival. We monitored fates of 92 radio-tagged ducklings in 31 broods in 5 wetland habitat types at Humacao Nature Reserve in southeastern Puerto Rico from 2000 to 2002. Wetlands included 2 separate coastal lagoon complexes, mangrove forest, and managed and unmanaged wetland impoundments containing herbaceous vegetation. We used known-fate models to estimate daily and interval survival rates of ducklings and broods. We conducted conservative and liberal analyses of survival because of uncertain fates of 36 ducklings. In the conservative analysis, the most parsimonious model for duckling survival contained wetland type and a positive influence of daily precipitation. In the liberal analysis, duckling survival also varied among wetlands, was positively influenced by daily precipitation, but negatively influenced by hatch date. Brood survival was also positively influenced by precipitation and female body mass. Managed wetland impoundments and shallowly flooded lagoon habitats containing ferns, interspersed cattail ( Typha dominguensis ), and other herbaceous cover promoted up to 3 times higher survival of ducklings over the course of a 30-day duckling period than we found in mangroves, more deeply flooded lagoons with predominately restricted shoreline cover, or unmanaged impoundments overgrown with vegetation. Broad confidence intervals for survival estimates among wetlands preclude unequivocal interpretation, but our results suggest that White-cheeked Pintail ducklings survive poorly in mangroves but benefit from appropriate management.

Puerto Rico↗

USGS2017

Occupancy and abundance of Eleutherodactylus frogs in coffee plantations in Puerto Rico

Shaded coffee plantations are of conservation value for many taxa, particularly for resident avifauna in the face of extensive landscape changes. Yet, little is known about the value of coffee plantations for amphibians because there are scant demographic data to index their value among species with different habitat preferences. We estimated the probability of occupancy of three frog species: Eleutherodactylus wightmanae, a forest species; E. brittoni, a grassland species; and E. antillensis, an open habitat species. Occupancy was estimated in sun and shaded plantations, and in secondary forest, in the west-central mountains of Puerto Rico. We also estimated the probability that a survey station was occupied by no individuals, one, or >1 individual, as a proxy of abundance. The aforementioned parameters, and local colonization and extinction probability, were modeled as a function of weather conditions (temperature, humidity) and vegetation cover at the sampling station (5 m) and contextual (100 m) scales. Encounter histories were obtained with passive acoustic recorders between February and July in 2015. Consistent with known habitat preferences, the highest occupancies were associated with secondary forests for E. wightmanae and sun plantations for E. brittoni . Occupancy probability for E. antillensis was similar across habitat types, indicating no aversion to shaded–forested habitats. Shaded plantations harbored moderate levels of occupancy for all species, indicating their potential value for multispecies conservation. Local colonization rates increased with forest cover for E. wightmanae, and with open habitats for E. brittoni and E. antillensis . Open habitats harbored a higher abundance of E. brittoni and E antillensis, but lower values for E. wightmanae . Sun and shaded plantations could provide quality habitat for Eleutherodactylus spp. if managed for features that promote local colonization and abundance.

Puerto Rico↗

USGS2017

Developing multi-model ensemble projections of ecologically relevant climate variables for Puerto Rico and the US Caribbean

The global increases in surface air temperature are the most widespread and direct consequence of anthropogenic climate change. However, while 21st century temperatures are projected to increase in the Caribbean, the low variability and high average temperatures suggest that impacts on ecosystems and water resources are more likely through changes to the availability, timing, and pattern of moisture. The lack of local-scale climate model information that can resolve the complex topography and small scale climate features hinders the development of robust adaptation strategies. The goal of this project was to develop a suite of local-scale climate projections using dynamic downscaling to aid the development of adaptation strategies in Puerto Rico and the U.S. Virgin Islands (USVI). This project began by engaging the ecologists, hydrologists, and conservation biologists in the region to determine the most valuable types of information to aid research and decision making. The final product provides projections of future climate at a 2km horizontal resolution based on three global climate models and two regional climate models for a scenario with high greenhouse gas emissions. Results from the projections suggest that for Puerto Rico, annual temperature would increase between 1°C and 1.3°C by mid-century with larger temperature increases located in the interior portion of the island. Precipitation totals decrease for much of the island with island average decline between 12% and 19%, with some potentially large localized decreases exceeding 30%. The projected changes for the USVI are dominated by the surrounding ocean environment. The resulting projections will be provided to stakeholders in the region via the USGS and the CLCC.

Puerto Rico↗

USGS2017

Occupancy and abundance of Eleutherodactylus wightmanae and E. brittoni along elevational gradients in west-central Puerto Rico

Populations of Eleutherodactylus species in Puerto Rico have declined in recent decades due to habitat loss and long-term climatic changes. The conservation of these habitat specialists requires an understanding of factors influencing their abundance and distribution, which at present is scant. We estimated occupancy probability and the probability of encountering ≥2 individuals of E. wightmanae (Melodius Coqui or Wightman's Robber Frog) and E. brittoni (Grass Coqui), species with contrasting habitat affinities, using multi-season, multi-state occupancy models. These parameters also served as an index of abundance (non-presence, 1, and ≥2 individuals). We modeled parameters as a function of seasonal temperature and humidity, long-term average monthly precipitation, and habitat covariates measured at survey sites along 2 elevation gradients in the southern slopes of west-central Puerto Rico. We collected survey data using passive acoustic recorders during 3 seasonal periods between February and July 2015. Occupancy patterns of both species was unimodal, containing higher probabilities (e.g., ≥0.5) at elevations between 400 m and 700 m, where long-term monthly precipitation varied between 120 mm and 160 mm. Chances of encountering ≥2 individuals increased with ground cover for E. brittoni , and decreased with increasing canopy cover for E. wightmanae . Seasonal temperature and relative humidity did not influence occupancy or the probability of encountering ≥2 individuals, likely because covariates varied within known tolerance levels for Eleutherodactylus . Our findings help reduce local extinction probability through management of habitat conditions that increase the likelihood of encountering ≥2 individuals. We also detailed an analytical framework suitable to test hypotheses aimed at predicting potential impacts from land use and climatic changes, and species responses to conservation actions.

Puerto Rico↗

USGS2016

Sedimentation survey of Lago Caonillas, Utuado, Puerto Rico, September–November 2012

During September–November 2012, the U.S. Geological Survey, in cooperation with the Puerto Rico Aqueduct and Sewer Authority, conducted a sedimentation survey of Lago Caonillas to estimate current (2012) reservoir storage capacity and the recent (2000–2012) reservoir sedimentation rate by comparing the 2012 bathymetric survey data with the February 2000 data. The Lago Caonillas storage capacity, which was 42.27 million cubic meters in February 2000, decreased to 39.55 million cubic meters by September–November 2012. The intersurvey (2000–2012) storage capacity loss was about 6 percent, corresponding to a decrease of about 0.5 percent per year; this loss represents a reservoir sedimentation rate of about 226,670 cubic meters per year between 2000 and 2012. On a long-term basis, however, the sedimentation rate has remained nearly constant, decreasing from about 257,500 to 251,720 cubic meters per year during 1948–2000 and 1948–2012, respectively. Most of the sediment accumulation and associated storage capacity loss of Lago Caonillas has occurred within the eastern and Río Caonillas branches of the reservoir. In the vicinity of the Caonillas Dam, minor sediment deposition and scour have occurred. The Lago Caonillas drainage area sediment yield has decreased by about 2 percent since the previous survey, from 1,266 cubic meters per square kilometer per year in 2000 to 1,237 cubic meters per square kilometer per year in 2012. If the long-term sedimentation rate of 251,720 cubic meters per year remains constant, the useful life of Lago Caonillas may end in about 2169.

Puerto Rico↗

USGS2016

Sedimentation survey of Lago La Plata, Toa Alta, Puerto Rico, March–April 2015

Introduction Lago La Plata is operated by the Puerto Rico Aqueduct and Sewer Authority (PRASA) and is part of the San Juan Metropolitan Water District. The reservoir serves a population of about 425,000 people. During 2013 the reservoir provided 0.307 million cubic meters (Mm3 ) of water per day (about 81 million gallons per day), which is equivalent to 31 percent of the total water demand for the metropolitan area (Wanda L. Molina, U.S. Geological Survey, written commun., 2015). The dam was constructed in 1974 and is located about 5 kilometers (km) south of the town of Toa Alta and 5 km north of the town of Naranjito (fig. 1). The drainage area upstream from the Lago La Plata dam is about 469 square kilometers (km2 ). The storage capacity at construction in 1974 was 26.84 Mm3 with a spillway elevation of 47.12 meters (m) above mean sea level (msl). Storage capacity was increased to 40.21 Mm3 in 1989 after the installation of bascule gates to provide a normal dam pool elevation at 52 m above msl (Puerto Rico Electric and Power Authority, 1979). The maximum height of the dam is about 40 m above the river bottom near the dam, and the intake structure consists of six 1.82-m-diameter ports facing upstream, with 6-m vertical spacing that begins at an elevation of 19 m above msl. The U.S. Geological Survey (USGS), in cooperation with the PRASA, conducted a bathymetric survey of the Lago La Plata reservoir during March and April 2015. The hydrographic survey was designed to provide an update of the reservoir storage capacity and sedimentation rate. Areas with substantial sediment accumulation are also discussed in this report. The results of the survey were used to prepare a bathymetric map showing the reservoir bottom (fig. 2) referenced with respect to the spillway elevation. This report also includes a summary of a previous bathymetric survey conducted in 2006 (Soler-López, 2008).

Puerto Rico↗

USGS2016

Sedimentation survey of Lago Lucchetti, Yauco, Puerto Rico, September 2013–May 2014

The U.S. Geological Survey conducted a sedimentation survey of Lago Lucchetti, Yauco, Puerto Rico, in 2013–14 in cooperation with the Puerto Rico Aqueduct and Sewer Authority. The survey updated a previous survey, conducted in 2000, and provided accurate information regarding reservoir storage capacity and sedimentation rate using bathymetric techniques and a global positioning system coupled with a depth sounder device. The results of the 2013–14 survey indicated a total storage capacity for Lago Lucchetti of 10.21 million cubic meters and a long-term sedimentation rate loss of 0.16 million cubic meters per year based on the original capacity in 1952. Sediment accumulation was about 10.14 million cubic meters over the life of the reservoir, which represents a storage decrease of about 50 percent of the original capacity in 1952. On the basis of a comparison between the 2013–14 and 2000 surveys, the useful life for Lago Lucchetti is projected to end in 2076.

Yauco↗

USGS2016

Dam failure analysis for the Lago El Guineo Dam, Orocovis, Puerto Rico

The U.S. Geological Survey, in cooperation with the Puerto Rico Electric Power Authority, completed hydrologic and hydraulic analyses to assess the potential hazard to human life and property associated with the hypothetical failure of the Lago El Guineo Dam. The Lago El Guineo Dam is within the headwaters of the Río Grande de Manatí and impounds a drainage area of about 4.25 square kilometers. The hydrologic assessment was designed to determine the outflow hydrographs and peak discharges for Lago El Guineo and other subbasins in the Río Grande de Manatí hydrographic basin for three extreme rainfall events: (1) a 6-hour probable maximum precipitation event, (2) a 24-hour probable maximum precipitation event, and (3) a 24-hour, 100-year recurrence rainfall event. The hydraulic study simulated a dam failure of Lago El Guineo Dam using flood hydrographs generated from the hydrologic study. The simulated dam failure generated a hydrograph that was routed downstream from Lago El Guineo Dam through the lower reaches of the Río Toro Negro and the Río Grande de Manatí to determine water-surface profiles developed from the event-based hydrologic scenarios and “sunny day” conditions. The Hydrologic Engineering Center’s Hydrologic Modeling System (HEC–HMS) and Hydrologic Engineering Center’s River Analysis System (HEC–RAS) computer programs, developed by the U.S. Army Corps of Engineers, were used for the hydrologic and hydraulic modeling, respectively. The flow routing in the hydraulic analyses was completed using the unsteady flow module available in the HEC–RAS model. Above the Lago El Guineo Dam, the simulated inflow peak discharges from HEC–HMS resulted in about 550 and 414 cubic meters per second for the 6- and 24-hour probable maximum precipitation events, respectively. The 24-hour, 100-year recurrence storm simulation resulted in a peak discharge of about 216 cubic meters per second. For the hydrologic analysis, no dam failure conditions are considered within the model. The results of the hydrologic simulations indicated that for all hydrologic conditions scenarios, the Lago El Guineo Dam would not experience overtopping. For the dam breach hydraulic analysis, failure by piping was the selected hypothetical failure mode for the Lago El Guineo Dam. Results from the simulated dam failure of the Lago El Guineo Dam using the HEC–RAS model for the 6- and 24-hour probable maximum precipitation events indicated peak discharges below the dam of 1,342.43 and 1,434.69 cubic meters per second, respectively. Dam failure during the 24-hour, 100-year recurrence rainfall event resulted in a peak discharge directly downstream from Lago El Guineo Dam of 1,183.12 cubic meters per second. Dam failure during sunny-day conditions (no precipitation) produced a peak discharge at Lago El Guineo Dam of 1,015.31 cubic meters per second assuming the initial water-surface elevation was at the morning-glory spillway invert elevation. The results of the hydraulic analysis indicate that the flood would extend to many inhabited areas along the stream banks from the Lago El Guineo Dam to the mouth of the Río Grande as a result of the simulated failure of the Lago El Guineo Dam. Low-lying regions in the vicinity of Ciales, Manatí, and Barceloneta, Puerto Rico, are among the regions that would be most affected by failure of the Lago El Guineo Dam. Effects of the flood control (levee) structure constructed in 2000 to provide protection to the low-lying populated areas of Barceloneta, Puerto Rico, were considered in the hydraulic analysis of dam failure. The results indicate that overtopping can be expected in the aforementioned levee during 6- and 24-hour probable maximum precipitation events. The levee was not overtopped during dam failure scenarios under the 24-hour, 100-year recurrence rainfall event or sunny-day conditions.

Orocovis↗

USGS2016

The 3D Elevation Program: summary for Puerto Rico

Elevation data are essential to a broad range of applications, including forest resources management, wildlife and habitat management, scientific research, national security, recreation, and many others. For the Commonwealth of Puerto Rico, elevation data are critical for flood risk management, landslide mitigation, natural resources conservation, sea level rise and subsidence, coastal zone management, infrastructure and construction management, and other business uses. Today, high-density light detection and ranging (lidar) data are the primary sources for deriving elevation models and other datasets. Federal, State, Tribal, U.S. territorial, and local agencies work in partnership to (1) replace data that are older and of lower quality and (2) provide coverage where publicly accessible data do not exist. A joint goal of State and Federal partners is to acquire consistent, statewide coverage to support existing and emerging applications enabled by lidar data. The National Enhanced Elevation Assessment evaluated multiple elevation data acquisition options to determine the optimal data quality and data replacement cycle relative to cost to meet the identified requirements of the user community. The evaluation demonstrated that lidar acquisition at quality level 2 for the conterminous United States, Hawaii, and selected U.S. territories, and quality level 5 interferometric synthetic aperture radar (IfSAR) data for Alaska, all with a 6- to 10-year acquisition cycle, provided the highest benefit/cost ratios. The 3D Elevation Program (3DEP) initiative selected an 8-year acquisition cycle for the respective quality levels. 3DEP, managed by the U.S. Geological Survey (USGS), the Office of Management and Budget Circular A‒16 lead agency for terrestrial elevation data, responds to the growing need for high-quality topographic data and a wide range of other three-dimensional (3D) representations of the Nation’s natural and constructed features.

Puerto Rico↗

USGS2016

Hydrologic conditions in the South Coast aquifer, Puerto Rico, 2010–15

In 1958, the U.S. Geological Survey began documenting hydrologic conditions, including groundwater levels, groundwater withdrawals for agricultural irrigation and public water supply, and water quality, in the South Coast aquifer, Puerto Rico. This information has improved the understanding of the water resources of the region. The hydrologic data indicate that (1) groundwater levels declined as much as 40 feet in the Salinas area and 11 feet in the Guayama area during 2012–14; (2) groundwater withdrawals for agricultural irrigation increased from 6.0 to 10.5 million gallons per day, or 75 percent, from 2010 to 2012; and (3) total groundwater withdrawals decreased from 29.3 to 23.8 million gallons per day from 2010 to 2014. The quantity and quality of water in the aquifer is primarily affected by variations in aquifer recharge as a result of changing rainfall or modes of irrigation; however, the spatial patterns and magnitude of water withdrawals for all uses have a secondary impact on the quantity and quality of water in the aquifer. National Oceanic and Atmospheric Administration data from climatological stations indicate that the 30-year normal precipitation for the period 1991–2010 in the South Coastal and Southern Slopes climatological regions was about 37.74 and 61.61 inches, respectively; the 30-year moving average precipitation for the period 1985–2014 was 37.94 and 61.80 inches, respectively, for these regions. The mean annual precipitation during 2012–14 was 13 percent below the 30-year moving average for the South Coastal climatological region and 7.7 percent below for the Southern Slopes climatological region. When rainfall is below the 30-year moving average, recharge is diminished and groundwater levels decline. Annual precipitation in the South Coast aquifer, which includes a large part of the South Coastal and Southern Slopes climatological regions, was 39.42, 37.25, and 34.89 inches per year for 2012, 2013, and 2014, respectively. Water level declines reduce the thickness of freshwater in the unconfined parts of the South Coast aquifer. Additionally, the pumping-induced migration of poor-quality water from deep or seaward areas of the aquifer can contribute to reductions in the thickness of freshwater in the aquifer. The reduction in the freshwater saturated thickness of the aquifer in areas near Ponce, Juana Díaz, Salinas, and Guayama is of particular concern because the total saturated thickness of the aquifer is thinner in these areas. Total dissolved solids concentration in groundwater samples indicates a small positive trend in Ponce, Santa Isabel, Salinas, and Guayama. Diminished aquifer recharge during 2012 to 2015 and, to a lesser extent, increased groundwater withdrawals have resulted in a reduction in the freshwater saturated thickness of the aquifer. The reduction in freshwater saturated thickness of the aquifer may affect freshwater resources available for agriculture and public water supply. A prolonged time period with reduced aquifer recharge may have substantial implications for groundwater levels and fresh groundwater availability.

Puerto Rico↗

USGS2016

Occupancy dynamics in human-modified landscapes in a tropical island: implications for conservation design

Aim Avian communities in human-modified landscapes exhibit varying patterns of local colonization and extinction rates, determinants of species occurrence. Our objective was to model these processes to identify habitat features that might enable movements and account for occupancy patterns in habitat matrices between the Guanica and Susua forest reserves. This knowledge is central to conservation design, particularly in ever changing insular landscapes. Location South-western Puerto Rico. Methods We used a multiseason occupancy modelling approach to quantify seasonal estimates of occupancy, and colonization and extinction rates of seven resident avian species surveyed over five seasons from January 2010 to June 2011. We modelled parameters by matrix type, expressions of survey station isolation, quality, amount of forest cover and context (embedded in forest patch). Results Seasonal occupancy remained stable throughout the study for all species, consistent with seasonally constant colonization and extinction probabilities. Occupancy was mediated by matrix type, higher in reserves and forested matrix than in the urban and agricultural matrices. This pattern is in accord with the forest affinities of all but an open-habitat specialist. Puerto Rican Spindalis ( Spindalis portoricensis ) exhibited high occupancy in the urban matrix, highlighting the adaptability of some insular species to novel environments. Highest colonization rates occurred when perching structures were at ≤ 500 m. Survey stations with at least three fruiting tree species and 61% forest cover exhibited lowest seasonal extinction rates. Main conclusions Our work identified habitat features that influenced seasonal probabilities of colonization and extinction in a human-modified landscape. Conservation design decisions are better informed with increased knowledge about interpatch distances to improve matrix permeability, and habitat features that increase persistence or continued use of habitat stepping stones. A focus on dynamic processes is valuable because conservation actions directly influence colonization and extinction rates, and thus, a quantitative means to gauge their benefit.

Puerto Rico↗

USGS2016

Climate change implications for tropical islands: Interpolating and interpreting statistically downscaled GCM projections for management and planning

The potential ecological and economic effects of climate change for tropical islands were studied using output from 12 statistically downscaled general circulation models (GCMs) taking Puerto Rico as a test case. Two model selection/model averaging strategies were used: the average of all available GCMs and the average of the models that are able to reproduce the observed large-scale dynamics that control precipitation over the Caribbean. Five island-wide and multidecadal averages of daily precipitation and temperature were estimated by way of a climatology-informed interpolation of the site-specific downscaled climate model output. Annual cooling degree-days (CDD) were calculated as a proxy index for air-conditioning energy demand, and two measures of annual no-rainfall days were used as drought indices. Holdridge life zone classification was used to map the possible ecological effects of climate change. Precipitation is predicted to decline in both model ensembles, but the decrease was more severe in the “regionally consistent” models. The precipitation declines cause gradual and linear increases in drought intensity and extremes. The warming from the 1960–90 period to the 2071–99 period was 4.6°–9°C depending on the global emission scenarios and location. This warming may cause increases in CDD, and consequently increasing energy demands. Life zones may shift from wetter to drier zones with the possibility of losing most, if not all, of the subtropical rain forests and extinction risks to rain forest specialists or obligates.

Puerto Rico↗

USGS2016

The sensitivity of WRF downscaled precipitation in Puerto Rico to cumulus parameterization and interior grid nudging

The sensitivity of the Weather Research and Forecasting Model (WRF) simulated precipitation over Puerto Rico is evaluated using multiple combinations of cumulus parameterization (CP) schemes and interior grid nudging. NCEP-DOE AMIP-II reanalysis (R-2) is downscaled to 2- km horizontal grid spacing with both convective permitting simulations (CP active only in the 49 middle and outer domains) and CP schemes active in all domains. The results generally show lower simulated precipitation amounts compared to the observations, regardless of WRF configuration. However, activating the CP schemes in the inner domain improves the annual cycle, intensity, and placement of rainfall compared to the convective permitting simulations. Furthermore, the use of interior grid nudging techniques in the outer domains improves the placement and intensity of rainfall in the inner domain. Incorporating a CP scheme at convective permitting scales (< 4 km) and grid nudging at non-convective permitting scales (> 4 km) improves the island average correlation of precipitation by 0.05 to 0.2 and reduces the island average RMSE by up to 40 mm on average over relying on the explicit microphysics at convective permitting scales with grid nudging. Projected changes in summer precipitation between 2040-2042 and 1985-1987 using WRF to downscale CCSM4 ranges from a 2.6 mm average increase to 81.9 mm average decrease, depending on the choice of CP scheme. The differences are only associated with differences between WRF configurations, which indicates the importance of CP scheme for projected precipitation change as well as historical accuracy.

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