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USGS2014

California State Waters Map Series: Offshore of Coal Oil Point, California

In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath sonar data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow (to about 100 m) subsurface geology. The Offshore of Coal Oil Point map area lies within the central Santa Barbara Channel region of the Southern California Bight. This geologically complex region forms a major biogeographic transition zone, separating the cold-temperate Oregonian province north of Point Conception from the warm-temperate California province to the south. The map area is in the southern part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation—at least 90°—since the early Miocene has been proposed for the Western Transverse Ranges province, and geodetic studies indicate that the region is presently undergoing north-south shortening. Uplift rates (as much as 2.0 mm/yr) that are based on studies of onland marine terraces provide further evidence of significant shortening. The cities of Goleta and Isla Vista, the main population centers in the map area, are in the western part of a contiguous urban area that extends eastward through Santa Barbara to Carpinteria. This urban area is on the south flank of the east-west-trending Santa Ynez Mountains, on coalescing alluvial fans and uplifted marine terraces underlain by folded and faulted Miocene bedrock. In the map area, the relatively low-relief, elevated coastal bajada narrows from about 2.5 km wide in the east to less than 500 m wide in the west. Several beaches line the actively utilized coastal zone, including Isla Vista County Park beach, Coal Oil Point Reserve, and Goleta Beach County Park. The beaches are subject to erosion each winter during storm-wave attack, and then they undergo gradual recovery or accretion during the more gentle wave climate of the late spring, summer, and fall months. The Offshore of Coal Oil Point map area lies in the central part of the Santa Barbara littoral cell, which is characterized by littoral drift to the east-southeast. Longshore drift rates have been reported to range from about 160,000 to 800,000 tons/yr, averaging 400,000 tons/yr. Sediment supply to the western and central parts of the littoral cell, including the map area, is largely from relatively small transverse coastal watersheds. Within the map area, these coastal watersheds include (from east to west) Las Llagas Canyon, Gato Canyon, Las Varas Canyon, Dos Pueblos Canyon, Eagle Canyon, Tecolote Canyon, Winchester Canyon, Ellwood Canyon, Glen Annie Canyon, and San Jose Creek. The Santa Ynez and Santa Maria Rivers, the mouths of which are about 100 to 140 km northwest of the map area, are not significant sediment sources because Point Conception and Point Arguello provide obstacles to downcoast sediment transport and also because much of their sediment load is trapped in dams. The Ventura and Santa Clara Rivers, the mouths of which are about 45 to 55 km southeast of the map area, are much larger sediment sources. Still farther east, eastward-moving sediment in the littoral cell is trapped by Hueneme and Mugu Canyons and then transported to the deep-water Santa Monica Basin. The offshore part of the map area consists of a relatively flat and shallow continental shelf, which dips gently seaward (about 0.8° to 1.0°) so that water depths at the shelf break, roughly coincident with the California’s State Waters limit, are about 90 m. This part of the Santa Barbara Channel is relatively well protected from large Pacific swells from the north and northwest by Point Conception and from the south and southwest by offshore islands and banks. The shelf is underlain by variable amounts of upper Quaternary marine and fluvial sediments deposited as sea level fluctuated in the late Pleistocene. The large (130 km2) Goleta landslide complex lies along the shelf break in the southern part of the map area. This compound slump complex may have been initiated more than 200,000 years ago, but it also includes three recent failures that may have been generated between 8,000 to 10,000 years ago. A local, 5- to 10-m-high tsunami may have been generated from these failure events. The map area has had a long history of hydrocarbon development, which began in 1928 with discovery of the Ellwood oil field. Subsequent discoveries in the offshore include South Ellwood offshore oil field, Coal Oil Point oil field, and Naples oil and gas field. Development of South Ellwood offshore field began in 1966 from platform “Holly,” the last platform to be installed in California’s State Waters. The area also is known for “the world’s most spectacular marine hydrocarbon seeps,” and large tar seeps are exposed on beaches east of the mouth of Goleta Slough. Offshore seeps adjacent to South Ellwood oil field release about 40 tons per day of methane and about 19 tons per day of ethane, propane, butane, and higher hydrocarbons. Seafloor habitats in the broad Santa Barbara Channel region consist of significant amounts of soft sediment and isolated areas of rocky habitat that support kelp-forest communities nearshore and rocky-reef communities in deep water. The potential marine benthic habitat types mapped in the Offshore of Coal Oil Point map area are directly related to its Quaternary geologic history, geomorphology, and active sedimentary processes. These potential habitats, which lie primarily within the Shelf (continental shelf) but also partly within the Flank (basin flank or continental slope) megahabitats, range from soft, unconsolidated sediment to hard sedimentary bedrock. This heterogeneous seafloor provides promising habitat for rockfish, groundfish, crabs, shrimp, and other marine benthic organisms.

California↗

USGS1994

Nutrients, suspended sediment, and pesticides in waters of the Red River of the North Basin, Minnesota, North Dakota, and South Dakota, 1970-90

Available data on nutrients (phosphorus and nitrogen), suspended sediment, and pesticides in the Red River of the North Basin, a study unit under the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program, are reviewed. These data were collected by several agencies during 1970-90. Nutrient concentrations in surface water are higher downgradient from agricultural and urban areas than in other areas, but generally do not exceed U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Levels (MCLs). The 10 milligram per liter (mg/L) drinking water MCL for nitrate (as nitrogen) was rarely exceeded. Some of the largest nutrient inputs to the surface-water system appear to come from the Fargo-Moorhead area. The highest nitrogen concentrations usually were found in the Red River of the North. Nitrogen composition was mostly organic nitrogen with some nitrate. Ammonia nitrogen was negligible except during mid-winter, when concentrations could exceed 1.0 mg/L. Streams draining the corn-dominated cropland in the southern part of the basin had relatively high nitrogen concentrations compared to parts of the basin where small-grain crops, forests, and wetlands predominate. The Pembina River in the northern part of the basin had a large range in nitrogen concentrations that often exceeded those in the Red River of the North. The highest phosphorus concentrations generally were found in of the Red River of the North, although tributary streams occasionally had peak concentrations that exceeded those in the Red River of the North. Median nitrate concentrations in ground water were less than 1.0 mg/L as nitrogen in all counties in the basin except in Otter Tail and Decker Counties in Minnesota. Half of the wells in Otter Tail County had nitrate-nitrogen concentrations exceeding 2.8 mg/L. Shallow, surficial aquifers tended to have the highest nitrate concentrations. Median suspended-sediment concentrations were less than 100 mg/L except in the Red River of the North near the Canadian border at Emerson, Manitoba and the Pembina River. The Pembina River occasionally had high suspended sediment concentrations; about 10 percent of the samples exceeded 2,000 mg/L. For both surface and ground water, available pesticide data were limited in spatial and temporal coverage. The majority of pesticide analyses for the Red River of the North Basin show no concentrations above laboratory reporting limits. Reported concentrations usually were below USEPA MCLs. Only a few analyses of pesticides in ground water had concentrations above laboratory reporting limits. Wells that had reportable levels are mainly in the southern and southeastern part of the basin, where atrazine was the most commonly detected pesticide. A relatively large fraction of stream samples had detectable quantities of 2,4-D, a- and y-HCH, and atrazine. These samples covered time spans of as much as 15 years and were from sites downstream from large drainage basins; however, concentrations were well below US EPA MCLs. One county-level study showed higher 2,4-D concentrations at upstream sites than at the outlet from a small basin. This indicates that downstream sites may fail to show impaired water-quality and the fate of pesticides used in the basin. Following the 1972 ban on DDT, concentrations of DDT in fish samples from the Red River of the North quickly decreased. Fish concentrations of DDE and DDD decreased more slowly. Low levels of DDE and DDD were detected in fish 14 years after the DDT ban.

Minnesota, North Dakota, South Dakota↗

USGS2007

USGS Tampa Bay Pilot Study

Many of the nation's estuaries have been environmentally stressed since the turn of the 20th century and will continue to be impacted in the future. Tampa Bay, one the Gulf of Mexico's largest estuaries, exemplifies the threats that our estuaries face (EPA Report 2001, Tampa Bay Estuary Program-Comprehensive Conservation and Management Plan (TBEP-CCMP)). More than 2 million people live in the Tampa Bay watershed, and the population constitutes to grow. Demand for freshwater resources, conversion of undeveloped areas to resident and industrial uses, increases in storm-water runoff, and increased air pollution from urban and industrial sources are some of the known human activities that impact Tampa Bay. Beginning on 2001, additional anthropogenic modifications began in Tampa Bat including construction of an underwater gas pipeline and a desalinization plant, expansion of existing ports, and increased freshwater withdrawal from three major tributaries to the bay. In January of 2001, the Tampa Bay Estuary Program (TBEP) and its partners identifies a critical need for participation from the U.S. Geological Survey (USGS) in providing multidisciplinary expertise and a regional-scale, integrated science approach to address complex scientific research issue and critical scientific information gaps that are necessary for continued restoration and preservation of Tampa Bay. Tampa Bay stakeholders identified several critical science gaps for which USGS expertise was needed (Yates et al. 2001). These critical science gaps fall under four topical categories (or system components): 1) water and sediment quality, 2) hydrodynamics, 3) geology and geomorphology, and 4) ecosystem structure and function. Scientists and resource managers participating in Tampa Bay studies recognize that it is no longer sufficient to simply examine each of these estuarine system components individually, Rather, the interrelation among system components must be understood to develop conceptual and predictive modeling tools for effective ecosystem adaptive management. As a multidisciplinary organization, the USGS possesses the capability of developing and coordinating an integrated science strategy for estuarine research founded on partnerships and collaborative efforts, multidisciplinary teams of scientists, and integrated field work, data analysis and interpretation, and product development. The primary role of the USGS in Tamps Bay research was defined with our partners based upon this capability to address estuarine issues using an integrated science approach with a regional perspective and within a national context to complement the numerous ongoing scien efforts by state and local agencies that address local issues within Tamp Bay. Six primary components of the USGS Tamp Bay Study address critical gaps within each of the the four estuarine system components and focus on: 1.) Examining how natural and man-made physical changes affect ecosystem health through mapping and modeling. 2.) Identifying sources and quality of groundwater, surface water, and sediment, 3.) Identifying sources and quality of groundwater, surface water, and sediment, 4.) Assessing the natural and man-made changes affecting wetland health and restoration, 5.) Identifying and measuring the impact of urbanization on seafloor habitats, Providing a web-based digital information management system of information for scientists and the public, including a system that supports the work of those officials who must make decisions that affect the state of the bay. The Tampa Bay Study is in its sixth year and will continue through September 2007. This paper presents a non-inclusive summary of key findings associated with the six primary project components listed above. Component 4 (above) is described in detail in the following chapter 13. More information on the Tampa Bay Study is available from our on-line digital information system for the Tampa Bay Study at http://gulfsci.usgs.gov.

Florida↗

USGS2015

Framework for modeling urban restoration resilience time in the aftermath of an extreme event

The impacts of extreme events continue long after the emergency response has terminated. Effective reconstruction of supply-chain strategic infrastructure (SCSI) elements is essential for postevent recovery and the reconnectivity of a region with the outside. This study uses an interdisciplinary approach to develop a comprehensive framework to model resilience time. The framework is tested by comparing resilience time results for a simulated EF-5 tornado with ground truth data from the tornado that devastated Joplin, Missouri, on May 22, 2011. Data for the simulated tornado were derived for Overland Park, Johnson County, Kansas, in the greater Kansas City, Missouri, area. Given the simulated tornado, a combinatorial graph considering the damages in terms of interconnectivity between different SCSI elements is derived. Reconstruction in the aftermath of the simulated tornado is optimized using the proposed framework to promote a rapid recovery of the SCSI. This research shows promising results when compared with the independent quantifiable data obtained from Joplin, Missouri, returning a resilience time of 22 days compared with 25 days reported by city and state officials.

Kansas↗

USGS2003

Water-quality and algal conditions in the Clackamas River basin, Oregon, and their relations to land and water management

In 1998, the U.S. Geological Survey sampled the Clackamas River, its major tributaries, and reservoirs to characterize basic water quality (nutrients, dissolved oxygen, pH, temperature, and conductance), water quantity (water sources within the basin), and algal conditions (biomass and species composition). Sampling locations reflected the dominant land uses in the basin (forest management, agriculture, and urban development) as well as the influence of hydroelectric projects, to examine how these human influences might be affecting water quality and algal conditions. Nuisance algal growths, with accompanying negative effects on water quality, were observed at several locations in the basin during this study. Algal biomass in the lower Clackamas River reached a maximum of 300 mg/m2 chlorophyll a, producing nuisance algal conditions, including fouled stream channels and daily fluctuations in pH and dissolved oxygen concentrations to levels that did not meet water-quality standards. Algal biomass was highest at sites immediately downstream from the hydroelectric project's reservoirs and/or powerhouses. Nuisance algal conditions also were observed in some of the tributaries, including the North Fork of the Clackamas River, Clear Creek, Rock Creek, and Sieben Creek. High amounts of drifting algae increased turbidity levels in the Clackamas River during June, which coincided with a general increase in the concentration of disinfection by-products found in treated Clackamas River water used for drinking, presumably due to the greater amounts of organic matter in the river. The highest nutrient concentrations were found in the four lowermost tributaries (Deep, Richardson, Rock, and Sieben Creeks), where most of the agriculture and urban development is concentrated. Of these, the greatest load of nutrients came from Deep Creek, which had both high nutrient concentrations and relatively high streamflow. Streams draining forestland in the upper basin (upper Clackamas River and Oak Grove Fork) had the highest concentrations of phosphorus (and lowest concentrations of nitrogen), and streams draining forestland in the middle basin (Clear Creek, Eagle Creek, and the North Fork of the Clackamas River) had relatively high concentrations of nitrogen (and low concentrations of phosphorus). In contrast, relatively low concentrations of both nitrogen and phosphorus were found at the two reference streams, reflecting their pristine condition. Relatively high phosphorus levels in the upper basin are probably due to the erosion of naturally occurring phosphorus deposits in this area. Likely sources of nitrogen (mostly nitrate) in the forested watersheds include nitrogen-fixing plants, atmospheric deposition, timber harvesting, and applications of urea fertilizers.

Water-Resources Investigations Report↗

USGS2017

U.S. Geological Survey Karst Interest Group Proceedings, San Antonio, Texas, May 16–18, 2017

Introduction and Acknowledgments Karst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) and evaporites (gypsum, anhydrite, and halite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are varied and complex. These factors involve biological, chemical, and physical changes that when combined with the diverse climatic regimes in which karst development has taken place, result in the unique dual- or triple-porosity nature of karst aquifers. These complex hydrogeologic systems typically represent challenging and unique conditions to scientists attempting to study groundwater flow and contaminant transport in these terrains. The dissolution of carbonate rocks and the subsequent development of distinct and beautiful landscapes, caverns, and springs have resulted in the most exceptional karst areas being designated as national or state parks. Tens of thousands of similar areas in the United States have been developed into commercial caverns and known privately owned caves. Both public and private properties provide access for scientists to study the flow of groundwater in situ . Likewise, the range and complexity of landforms and groundwater flow systems associated with karst terrains are enormous, perhaps more than for any other aquifer type. Karst aquifers and landscapes that form in tropical areas, such as the cockpit karst along the north coast of Puerto Rico, differ greatly from karst landforms in more arid climates, such as the Edwards Plateau in west-central Texas or the Guadalupe Mountains near Carlsbad, New Mexico, where hypogenic processes have played a major role in speleogenesis. Many of these public and private lands also contain unique flora and fauna associated with these karst hydrogeologic systems. As a result, numerous federal, state, and local agencies have a strong interest in the study of karst terrains. Many of the major springs and aquifers in the United States have developed in carbonate rocks, such as the Floridan aquifer system in Florida and parts of Alabama, Georgia, and South Carolina; the Ozark Plateaus aquifer system in parts of Arkansas, Kansas, Missouri, and Oklahoma; and the Edwards-Trinity aquifer system in west-central Texas. These aquifers, and the springs that discharge from them, serve as major water-supply sources and form unique ecological habitats. Competition for the water resources of karst aquifers is common, and urban development and the lack of attenuation of contaminants in karst areas due to dissolution features that form direct pathways into karst aquifers can impact the ecosystem and water quality associated with these aquifers. The concept for developing a platform for interaction among scientists within the U.S. Geological Survey (USGS) working on karst-related studies evolved from the November 1999 National Groundwater Meeting of the USGS. As a result, the Karst Interest Group (KIG) was formed in 2000. The KIG is a loose-knit, grass-roots organization of USGS and non-USGS scientists and researchers devoted to fostering better communication among scientists working on, or interested in, karst science. The primary mission of the KIG is to encourage and support interdisciplinary collaboration and technology transfer among scientists working in karst areas. Additionally, the KIG encourages collaborative studies between the different mission areas of the USGS as well as with other federal and state agencies, and with researchers from academia and institutes. To accomplish its mission, the KIG has organized a series of workshops that have been held near nationally important karst areas. To date (2017) seven KIG workshops, including the workshop documented in this report, have been held. The workshops typically include oral and poster sessions on selected karst-related topics and research, as well as field trips to local karst areas. To increase non-USGS participation an effort was made for the workshops to be held at a university or institute beginning with the fourth workshop. Proceedings of the workshops are published by the USGS and are available online at the USGS publications warehouse https://pubs.er.usgs.gov/ by using the search term “karst interest group.” The first KIG workshop was held in St. Petersburg, Florida, in 2001, in the vicinity of the large springs and other karst features of the Floridan aquifer system. The second KIG workshop was held in 2002, in Shepherdstown, West Virginia, in proximity to the carbonate aquifers of the northern Shenandoah Valley, and highlighted an invited presentation on karst literature by the late Barry F. Beck of P.E. LaMoreaux and Associates. The third KIG workshop was held in 2005, in Rapid City, South Dakota, near evaporite karst features in limestones of the Madison Group in the Black Hills of South Dakota. The Rapid City KIG workshop included field trips to Wind Cave National Park and Jewel Cave National Monument, and featured a presentation by Thomas Casadevall, then USGS Central Region Director, on the status of Earth science at the USGS. The fourth KIG workshop in 2008 was hosted by the Hoffman Environmental Research Institute and Center for Cave and Karst Studies at Western Kentucky University in Bowling Green, Kentucky, near Mammoth Cave National Park and karst features of the Chester Upland and Pennyroyal Plateau. The workshop featured a late-night field trip into Mammoth Cave led by Rickard Toomey and Rick Olsen, National Park Service. The fifth KIG workshop in 2011 was a joint meeting of the USGS KIG and University of Arkansas HydroDays, hosted by the Department of Geosciences at the University of Arkansas in Fayetteville. The workshop featured an outstanding field trip to the unique karst terrain along the Buffalo National River in the southern Ozarks, and a keynote presentation on paleokarst in the United States was delivered by Art and Peggy Palmer. The sixth KIG workshop was hosted by the National Cave and Karst Research Institute (NCKRI) in 2014, in Carlsbad, New Mexico. George Veni, Director of the NCKRI, served as a co-chair of the workshop with Eve Kuniansky of the USGS. The workshop featured speaker Dr. Penelope Boston, Director of Cave and Karst Studies at New Mexico Tech, Socorro, and Academic Director at the NCKRI, who addressed the future of karst research. The field trip on evaporite karst of the lower Pecos Valley was led by Lewis Land (NCKRI karst hydrologist), and the field trip on the geology of Carlsbad Caverns National Park was led by George Veni. This current seventh KIG workshop is being held in San Antonio at the University of Texas at San Antonio (UTSA). This 2017 workshop is being hosted by the Department of Geological Sciences’ Student Geological Society (SGS), and student chapters of the American Association of Petroleum Geologists (AAPG) and Association of Engineering Geologists (AEG), with support by the UTSA Department of Geological Sciences and Center for Water Research. The UTSA student chapter presidents, Jose Silvestre (SGS), John Cooper (AAPG), and Tyler Mead (AEG) serve as co-chairs of the 2017 workshop with Eve Kuniansky of the USGS. The technical session committee is chaired by Eve Kuniansky, USGS, and includes Michael Bradley, Tom Byl, Rebecca Lambert, John Lane, and James Kaufmann, all USGS, and Patrick Tucci, retired USGS. The logistics committee includes Amy Clark, Yongli Gao, and Lance Lambert (Department Chair), UTSA Department of Geological Sciences; and Ryan Banta and Allan Clark, USGS, San Antonio, Texas. The field trip committee is chaired by Allan Clark and includes Amy Clark, Yongli Gao, and Keith Muehlestein, UTSA; Marcus Gary, Edwards Aquifer Authority and University of Texas at Austin; Ron Green, Southwest Research Institute; Geary Schindel, Edwards Aquifer Authority; and George Veni, NCKRI. Additionally, two organizations have assisted the UTSA student chapters in hosting the meeting by donating funds to the chapters: the Edwards Aquifer Authority, San Antonio, Texas, and the Barton Springs Edwards Aquifer Authority, Austin, Texas. Additionally, Yongli Gao, Center for Water Research and Department of Geological Sciences, UTSA, helped develop sessions on cave and karst research in China for this workshop. These proceedings could not have been accomplished without the assistance of Lawrence E. Spangler as co-editor who not only has subject matter expertise, but also serves as an editor with the USGS Science Publishing Network. We sincerely hope that this workshop continues to promote future collaboration among scientists of varied and diverse backgrounds, and improves our understanding of karst aquifer systems in the United States and its territories. The extended abstracts of USGS authors were peer reviewed and approved for publication by the USGS. Articles submitted by university researchers and other federal and state agencies did not go through the formal USGS peer review and approval process, and therefore may not adhere to USGS editorial standards or stratigraphic nomenclature. However, all articles had a minimum of two peer reviews and were edited for consistency of appearance in the proceedings. The use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The USGS Water Availability and Use Science Program funded the publication costs of the proceedings.

Scientific Investigations Report↗

USGS2013

Geographic setting influences Great Lakes beach microbiological water quality

Understanding of factors that influence Escherichia coli (EC) and enterococci (ENT) concentrations, pathogen occurrence, and microbial sources at Great Lakes beaches comes largely from individual beach studies. Using 12 representative beaches, we tested enrichment cultures from 273 beach water and 22 tributary samples for EC, ENT, and genes indicating the bacterial pathogens Shiga-toxin producing E. coli (STEC), Shigella spp., Salmonella spp, Campylobacter jejuni/coli, and methicillin-resistant Staphylococcus aureus, and 108–145 samples for Bacteroides human, ruminant, and gull source-marker genes. EC/ENT temporal patterns, general Bacteroides concentration, and pathogen types and occurrence were regionally consistent (up to 40 km), but beach catchment variables (drains/creeks, impervious surface, urban land cover) influenced exceedances of EC/ENT standards and detections of Salmonella and STEC. Pathogen detections were more numerous when the EC/ENT Beach Action Value (but not when the Geometric Mean and Statistical Threshold Value) was exceeded. EC, ENT, and pathogens were not necessarily influenced by the same variables. Multiple Bacteroides sources, varying by date, occurred at every beach. Study of multiple beaches in different geographic settings provided new insights on the contrasting influences of regional and local variables, and a broader-scale perspective, on significance of EC/ENT exceedances, bacterial sources, and pathogen occurrence.

Great Lakes↗

USGS2017

Persistence of historical population structure in an endangered species despite near-complete biome conversion in California's San Joaquin Desert

Genomic responses to habitat conversion can be rapid, providing wildlife managers with time-limited opportunities to enact recovery efforts that use population connectivity information that reflects predisturbance landscapes. Despite near-complete biome conversion, such opportunities may still exist for the endemic fauna and flora of California's San Joaquin Desert, but comprehensive genetic data sets are lacking for nearly all species in the region. To fill this knowledge gap, we studied the rangewide population structure of the endangered blunt-nosed leopard lizard Gambelia sila , a San Joaquin Desert endemic, using restriction site-associated DNA (RAD), microsatellite and mtDNA data to test whether admixture patterns and estimates of effective migration surfaces (EEMS) can identify land areas with high population connectivity prior to the conversion of native xeric habitats. Clustering and phylogenetic analyses indicate a recent shared history between numerous isolated populations and EEMS reveals latent signals of corridors and barriers to gene flow over areas now replaced by agriculture and urbanization. Conflicting histories between the mtDNA and nuclear genomes are consistent with hybridization with the sister species G. wislizenii , raising important questions about where legal protection should end at the southern range limit of G. sila . Comparative analysis of different data sets also adds to a growing list of advantages in using RAD loci for genetic studies of rare species. We demonstrate how the results of this work can serve as an evolutionary guidance tool for managing endemic, arid-adapted taxa in one of the world's most compromised landscapes.

California↗

USGS2007

Mangrove forest distributions and dynamics (1975–2005) of the tsunami-affected region of Asia

Aim We aimed to estimate the present extent of tsunami-affected mangrove forests and determine the rates and causes of deforestation from 1975 to 2005. Location Our study region covers the tsunami-affected coastal areas of Indonesia, Malaysia, Thailand, Burma (Myanmar), Bangladesh, India and Sri Lanka in Asia. Methods We interpreted time-series Landsat data using a hybrid supervised and unsupervised classification approach. Landsat data were geometrically corrected to an accuracy of plus-or-minus half a pixel, an accuracy necessary for change analysis. Each image was normalized for solar irradiance by converting digital number values to the top-of-the atmosphere reflectance. Ground truth data and existing maps and data bases were used to select training samples and also for iterative labelling. We used a post-classification change detection approach. Results were validated with the help of local experts and/or high-resolution commercial satellite data. Results The region lost 12% of its mangrove forests from 1975 to 2005, to a present extent of c . 1,670,000 ha. Rates and causes of deforestation varied both spatially and temporally. Annual deforestation was highest in Burma ( c . 1%) and lowest in Sri Lanka (0.1%). In contrast, mangrove forests in India and Bangladesh remained unchanged or gained a small percentage. Net deforestation peaked at 137,000 ha during 1990–2000, increasing from 97,000 ha during 1975–90, and declining to 14,000 ha during 2000–05. The major causes of deforestation were agricultural expansion (81%), aquaculture (12%) and urban development (2%). Main conclusions We assessed and monitored mangrove forests in the tsunami-affected region of Asia using the historical archive of Landsat data. We also measured the rates of change and determined possible causes. The results of our study can be used to better understand the role of mangrove forests in saving lives and property from natural disasters such as the Indian Ocean tsunami, and to identify possible areas for conservation, restoration and rehabilitation.

Journal of Biogeography↗

USGS2008

U.S. Geological Survey Karst Interest Group Proceedings, Bowling Green, Kentucky, May 27-29, 2008

*INTRODUCTION AND ACKNOWLEDGMENTS* Karst aquifer systems are present throughout parts of the United States and some of its territories. The complex depositional environments that form carbonate rocks combined with post-depositional tectonic events and the diverse climatic regimes under which these rocks were formed result in unique hydrologic systems. The dissolution of calcium carbonate and the subsequent development of distinct and beautiful landscapes, caverns, and springs have resulted in some karst areas of the United States being designated as national or state parks and commercial caverns. Karst aquifers and landscapes that form in tropical areas, such as the north coast of Puerto Rico, differ greatly from karst areas in more arid climates, such as central Texas or western South Dakota. Many of these public and private lands contain unique flora and fauna associated with the hydrologic systems in these karst areas. As a result, multiple Federal, State, and local agencies have an interest in the study of karst terrains. Carbonate sediments and rocks (limestone and dolomite) are composed of greater than 50 percent carbonate minerals and the predominant carbonate mineral is calcium carbonate or limestone (CaCO3). Unlike terrigenous clastic sedimentation, the depositional processes that produce carbonate rocks are complex, involving both biological and physical processes. These depositional processes impact greatly the development of permeability of the sediments. Carbonate minerals readily dissolve or precipitate depending on the chemistry of the water flowing through the rock, thus the study of both marine and meteoric diagenesis of carbonate sediments is multidisciplinary. Even with a better understanding of the depositional environment and subsequent diagenesis, the dual porosity nature of karst aquifers presents challenges to scientists attempting to study ground-water flow and contaminant transport. Many of the major springs and aquifers in the United States are developed in carbonate rocks and karst areas. These aquifers and the springs that discharge from them, serve as major water-supply sources and as unique biological habitats. Commonly, there is competition for the water resources of karst aquifers, and urban development in karst areas can impact the ecosystem and water quality of these aquifers. The concept for developing a Karst Interest Group evolved from the November 1999 National Ground-Water Meeting of the U.S. Geological Survey (USGS), Water Resources Division. As a result, the Karst Interest Group was formed in 2000. The Karst Interest Group is a loose-knit grass-roots organization of USGS employees devoted to fostering better communication among scientists working on, or interested in, karst hydrology studies. The mission of the Karst Interest Group is to encourage and support interdisciplinary collaboration and technology transfer among USGS scientists working in karst areas. Additionally, the Karst Interest Group encourages cooperative studies between the different disciplines of the USGS and other Department of Interior agencies and university researchers or research institutes. The first Karst Interest Group workshop was held in St. Petersburg, Florida, February 13-16, 2001, in the vicinity of karst features of the Floridan aquifer system. The proceedings of that first meeting, Water-Resources Investigations Report 01-4011 are available online at: http://water.usgs.gov/ogw/karst/ The second Karst Interest Group workshop was held August 20-22, 2002, in Shepherdstown, West Virginia, in close proximity to the carbonate aquifers of the northern Shenandoah Valley. The proceedings of the second workshop were published in Water-Resources Investigations Report 02-4174, which is available online at the previously mentioned website. The third workshop of the Karst Interest Group was held September, 12-15, 2005, in Rapid City, South Dakota, which is in close proximity to karst features

Scientific Investigations Report↗

USGS2004

Sources of phosphorus to the Carson River upstream from Lahontan Reservoir, Nevada and California, Water Years 2001-02

Discharge of treated municipal-sewage effluent to the Carson River in western Nevada and eastern California ceased by 1987 and resulted in a substantial decrease in phosphorus concentrations in the Carson River. Nonetheless, concentrations of total phosphorus and suspended sediment still commonly exceed beneficial-use criteria established for the Carson River by the Nevada Division of Environmental Protection. Potential sources of phosphorus in the study area include natural inputs from undisturbed soils, erosion of soils and streambanks, construction of low-head dams and their destruction during floods, manure production and grazing by cattle along streambanks, drainage from fields irrigated with streamwater and treated municipal-sewage effluent, ground-water seepage, and urban runoff including inputs from golf courses. In 2000, the U.S. Geological Survey (USGS), in cooperation with Carson Water Subconservancy District, began an investigation with the overall purpose of providing managers and regulators with information necessary to develop and implement total maximum daily loads for the Carson River. Two specific goals of the investigation were (1) to identify those reaches of the Carson River upstream from Lahontan Reservoir where the greatest increases in phosphorus and suspended-sediment concentrations and loading occur, and (2) to identify the most important sources of phosphorus within the reaches of the Carson River where the greatest increases in concentration and loading occur. Total-phosphorus concentrations in surface-water samples collected by USGS in the study area during water years 2001-02 ranged from <0.01 to 1.78 mg/L and dissolved-orthophosphate concentrations ranged from <0.01 to 1.81 mg/L as phosphorus. In streamflow entering Carson Valley from headwater areas in the East Fork Carson River, the majority of samples exceeding the total phosphorus water-quality standard of 0.1 mg/L occur during spring runoff (March, April, and May) when suspended-sediment concentrations are high. Downstream from Carson Valley, almost all samples exceed the water-quality standard, with the greatest concentrations observed during spring and summer months. Estimated annual total-phosphorus loads ranged from 1.33 tons at the West Fork Carson River at Woodfords to 43.41 tons at the Carson River near Carson City during water years 2001-02. Loads are greatest during spring runoff, followed by fall and winter, and least during the summer, which corresponds to the amount of streamflow in the Carson River. The estimated average annual phosphorus load entering Carson Valley was 21.9 tons; whereas, the estimated average annual phosphorus load leaving Carson Valley was 37.8 tons, for an annual gain in load across Carson Valley of 15.9 tons. Thus, about 58 percent of the total-phosphorus load leaving Carson Valley on an annual basis could be attributed to headwater reaches upstream from Carson Valley. During spring and summer (April 1-September 30) an average of 85 percent of the total-phosphorus load leaving Carson Valley could be attributed to headwater reaches. During fall and winter (October 1-March 31) only 17 percent of the phosphorus load leaving Carson Valley could be attributed to headwater reaches. The composition of the phosphorus changes during summer from particulate phosphorus entering Carson Valley to dissolved orthophosphate leaving Carson Valley. Particulate phosphorus entering Carson Valley could be settling out when water is applied to fields and be replaced by dissolved orthophosphate from other sources. Alternatively, the particulate phosphorus could be converted to dissolved orthophosphate as it travels across Carson Valley. Data collected during the study are not sufficient to distinguish between the two possibilities. Eagle Valley and Dayton-Churchill Valleys may act as sinks for phosphorus. On an annual basis, during water years 2001-02, about 90 percent of the phosphorus entering Eagle Valley left the

Scientific Investigations Report↗

USGS2005

Molecular assays for targeting human and bovine enteric viruses in coastal waters and their application for library-independent source tracking

Rapid population growth and urban development along waterways and coastal areas have led to decreasing water quality. To examine the effects of upstream anthropogenic activities on microbiological water quality, methods for source-specific testing are required. In this study, molecular assays targeting human enteroviruses (HEV), bovine enteroviruses (BEV), and human adenoviruses (HAdV) were developed and used to identify major sources of fecal contamination in the lower Altamaha River, Georgia. Two-liter grab samples were collected monthly from five tidally influenced stations between July and December 2002. Samples were analyzed by reverse transcription- and nested-PCR. PCR results were confirmed by dot blot hybridization. Eleven and 17 of the 30 surface water samples tested positive for HAdV and HEV, respectively. Two-thirds of the samples tested positive for either HEV or HAdV, and the viruses occurred simultaneously in 26% of samples. BEV were detected in 11 of 30 surface water samples. Binary logistic regression analysis showed that the presence of both human and bovine enteric viruses was not significantly related to either fecal coliform or total coliform levels. The presence of these viruses was directly related to dissolved oxygen and streamflow but inversely related to water temperature, rainfall in the 30 days preceding sampling, and chlorophyll-?? concentrations. The stringent host specificity of enteric viruses makes them good library-independent indicators for identification of water pollution sources. Viral pathogen detection by PCR is a highly sensitive and easy-to-use tool for rapid assessment of water quality and fecal contamination when public health risk characterization is not necessary. Copyright ?? 2005, American Society for Microbiology. All Rights Reserved.

Applied and Environmental Microbiology↗

USGS2009

Behavioral response of the coachwhip (Masticophis flagellum) to habitat fragment size and isolation in an urban landscape

Habitat fragmentation is a significant threat to biodiversity worldwide. Habitat loss and the isolation of habitat fragments disrupt biological communities, accelerate the extinction of populations, and often lead to the alteration of behavioral patterns typical of individuals in large, contiguous natural areas. We used radio-telemetry to study the space-use behavior of the Coachwhip, a larger-bodied, wide-ranging snake species threatened by habitat fragmentation, in fragmented and contiguous areas of coastal southern California. We tracked 24 individuals at three sites over two years. Movement patterns of Coachwhips changed in habitat fragments. As area available to the snakes was reduced, individuals faced increased crowding, had smaller home-range sizes, tolerated greater home-range overlap, and showed more concentrated movement activity and convoluted movement pathways. The behavioral response shown by Coachwhips suggests, on a regional level, area-effects alone cannot explain observed extinctions on habitat fragments but, instead, suggests changes in habitat configuration are more likely to explain the decline of this species. Ultimately, if “edge-exposure” is a common cause of decline, then isolated fragments, appropriately buffered to reduce emigration and edge effects, may support viable populations of fragmentation-sensitive species.

California↗

USGS1996

Occurrence and accumulation of pesticides and organic contaminants in river sediment, water and clam tissues from the San Joaquin River and tributaries, California

A study was conducted in 1992 to assess the effects of anthropogenic activities and land use on the water quality of the San Joaquin River and its major tributaries. This study focused on pesticides and organic contaminants, looking at distributions of contaminants in water, bed and suspended sediment, and the bivalve Corbicula fluminea. Results indicated that this river system is affected by agricultural practices and urban runoff. Sediments from Dry Creek contained elevated concentrations of polycyclic aromatic hydrocarbons (PAHs), possibly derived from urban runoff from the city of Modesto; suspended sediments contained elevated amounts of chlordane. Trace levels of triazine herbicides atrazine and simazine were present in water at most sites. Sediments, water, and bivalves from Orestimba Creek, a westside tributary draining agricultural areas, contained the greatest levels of DDT (1,1,1-trichloro-2-2-bis[p-chlorophenyl]ethane), and its degradates DDD (1,1-dichloro-2,2-bis[p-chlorophenyl]ethane), and DDE (1,1-dichloro-2,2- bis[p-chlorophenyl]ethylene). Sediment adsorption co efficients (K(oc)), and bioconcentration factors (BCF) in Corbicula of DDT, DDD, and DDE at Orestimba Creek were greater than predicted values. Streams of the western San Joaquin Valley can potentially transport significant amounts of chlorinated pesticides to the San Joaquin River, the delta, and San Francisco Bay. Organochlorine compounds accumulate in bivalves and sediment and may pose a problem to other biotic species in this watershed.

California↗

USGS1970

Water in urban planning, Salt Creek Basin, Illinois water management as related to alternative land-use practices

Water management can be an integral part of urban comprehensive planning in a large metropolitan area. Water both imposes constraints on land use and offers opportunities for coordinated land and water management. Salt Creek basin in Cook and Du Page Counties of the Chicago metropolitan area is typical of rapidly developing suburban areas and has been selected to illustrate some of these constraints and opportunities and to suggest the effects of alternative solutions. The present study concentrates on the related problems of ground-water recharge, water quality, management of flood plains, and flood-control measures. Salt Creek basin has a drainage area of 150 square miles. It is in flat to. gently rolling terrain, underlain by glacial drift as much as 200 feet thick which covers a dolomite aquifer. In 1964, the population of the basin was about 400,000, and 40 percent of the land was in urban development. The population is expected to number 550,000 to 650,000 by 1990, and most of the land will be taken by urban development. Salt Creek is a sluggish stream, typical of small drainage channels in the headwaters area of northeastern Illinois. Low flows of 15 to 25 cubic feet per second in the lower part of the basin consist largely of sewage effluent. Nearly all the public water supplies in the basin depend on ground water. Of the total pumpage of 27.5 million gallons per day, 17.5 million gallons per day is pumped from the deep (Cambrian-Ordovician) aquifers and 10 million gallons per day is pumped from the shallow (Silurian dolomite and glacial drift) aquifers. The potential yield of the shallow aquifers, particularly glacial drift in the northern part of the basin, far exceeds present use. The largest concentration of pumpage from the shallow ,aquifers is in the Hinsdale-La Grange area. Salt Creek serves as an important source of recharge to these supplies, particularly just east of Hinsdale. The entire reach of Salt Creek south and east of Elmhurst can be regarded as an area of potential recharge to the shallow aquifers. Preservation of the effectiveness of these potential recharge areas should be considered in land-use planning. Salt Creek is polluted in times of both low and high flow. Most communities in the basin in Du Page County discharge their treated sewage into the creek, whereas those in Cook County transfer their sewage to plants of the Metropolitan Sanitary District outside the basin. During periods of high runoff, combined storm runoff and overflow from sanitary sewers enter the creek. Such polluted water detracts from the stream's esthetic and recreational potential and poses a threat to ground-water supplies owing to induced recharge of polluted water to shallow aquifers. Alternative approaches .to the pollution problem include improvement of the degree of sewage treatment, detention and treatment of storm runoff, dilution of sewage through flow augmentation, or transfer of sewage from the basin to a central treatment plant. To result in an enhanced environment, the streambed would have to be cleansed of accumulated sludge deposits. The overbank flooding in Salt Creek basin every 2 to 3 years presents problems because of encroachments and developments on the flood plains. Flood plains in an urban area can be managed by identifying them, by recognizing that either their natural storage capacity or equivalent artificial capacity is needed to accommodate floods, and by planning land use accordingly. Examples of effective floodplain management include (1) preservation of greenbelts or regional parks along stream courses, (2) use of flood plains for recreation, parking lots. or other low-intensity uses, (3) use of flood-proofed commercial buildings, and (4) provision for compensatory storage to replace natural storage capacity. Results of poor flood-plain management include uncontrolled residential development and encroachment by fill into natural storage areas where no compensatory storage has been

Water Supply Paper↗

USGS2013

Real-time piscicide tracking using Rhodamine WT dye for support of application, transport, and deactivation strategies in riverine environments

Piscicide applications in riverine environments are complicated by the advection and dispersion of the piscicide by the flowing water. Proper deactivation of the fish toxin is required outside of the treatment reach to ensure that there is minimal collateral damage to fisheries downstream or in connecting and adjacent water bodies. In urban settings and highly managed waterways, further complications arise from the influence of industrial intakes and outfalls, stormwater outfalls, lock and dam operations, and general unsteady flow conditions. These complications affect the local hydrodynamics and ultimately the transport and fate of the piscicide. This report presents two techniques using Rhodamine WT dye for real-time tracking of a piscicide plume—or any passive contaminant—in rivers and waterways in natural and urban settings. Passive contaminants are those that are present in such low concentration that there is no effect (such as buoyancy) on the fluid dynamics of the receiving water body. These methods, when combined with data logging and archiving, allow for visualization and documentation of the application and deactivation process. Real-time tracking and documentation of rotenone applications in rivers and urban waterways was accomplished by encasing the rotenone plume in a plume of Rhodamine WT dye and using vessel-mounted submersible fluorometers together with acoustic Doppler current profilers (ADCP) and global positioning system (GPS) receivers to track the dye and map the water currents responsible for advection and dispersion. In this study, two methods were used to track rotenone plumes: (1) simultaneous injection of dye with rotenone and (2) delineation of the upstream and downstream boundaries of the treatment zone with dye. All data were logged and displayed on a shipboard laptop computer, so that survey personnel provided real-time feedback about the extent of the rotenone plume to rotenone application and deactivation personnel. Further, these strategies facilitate adjustment of rotenone application and deactivation strategies in real time if necessary based on the observed advection and dispersion of the rotenone plume. Two large-scale and complex applications of rotenone in the Chicago Area Waterway System (CAWS) in 2009 and 2010 to combat invasive Asian carp are documented in this report. The application in Chicago Sanitary and Ship Canal (CSSC) in December 2009 involved more than 1,800 gallons of rotenone injected at multiple stations through a 6.2-mile reach of the canal near Lockport, Illinois. The rotenone plume was encased in Rhodamine WT dye so that two survey boats provided real-time feedback to shore personnel regarding the plume extent as it advected downstream. Real-time tracking of the rotenone was essential in this large-scale application because of the multistage injection strategy and the numerous deactivation points required to minimize collateral damage to fisheries in surrounding and receiving water bodies. All timing of application and deactivation operations relied on dye tracking. A second application of rotenone in May 2010 to the Little Calumet River near O’Brien Lock and Dam (Illinois) provided another opportunity for dye-tracking support operations; however, application and deactivation strategies were designed considering zero-flow conditions within the reach of interest. Therefore, dye was injected at the upstream and downstream boundaries of the rotenone application reach and was used to track movement of water in and out of a treatment reach, allowing proper deactivation to occur and avoiding unnecessary damage to fisheries downstream. The data collected during the real-time tracking operations for both applications allowed full documentation of the rotenone treatment for archival purposes and provided information for future applications. The methods presented in this report for real-time tracking and documentation of piscicide applications in riverine environments worked exceptionally well and allowed the multiagency Asian Carp Rapid Response Workgroup to carry out large-scale rotenone applications in urban waterways in an environmentally responsible manner with minimal collateral damage to fisheries outside the treatment reach. Traveltime information extracted from the boat-mounted and fixed-position fluorometers agrees well with empirical predictions from a preliminary dye study (mock rotenone injection) on this system completed in November 2009 on the CSSC and with previously published methods for estimating traveltimes of the peak, leading edge, and trailing edge of the plume. Although the rotenone application strategy called for zero-flow conditions on the Little Calumet River in 2010, downstream advection of treated water did occur, and dye tracing combined with velocity mapping allowed this advection to be documented and exposed the unique hydrodynamics and mixing within this reach. The large volumes of data collected during the operations allow documentation and visualization of the rotenone applications, thus providing feedback to planners and archival of the treatments for future reference. The methods developed in this report are directly transferrable to piscicide applications in water bodies in other locations, including rivers, ponds, or lakes, and can be used for real-time tracking of any passive contaminant that may enter a water body.

Illinois↗

USGS2006

Concentrations, loads, and yields of particle-associated contaminants in urban creeks, Austin, Texas, 1999-2004

Concentrations, loads, and yields of particle-associated (hydrophobic) contaminants (PACs) in urban runoff in creeks in Austin, Texas, were characterized using an innovative approach: large-volume suspended-sediment sampling. This approach isolates suspended sediment from the water column in quantities sufficient for direct chemical analysis of PACs. During 1999-2004, samples were collected after selected rain events from each of five stream sites and Barton Springs for a study by the U.S. Geological Survey, in cooperation with the City of Austin. Sediment isolated from composited samples was analyzed for major elements, metals, organochlorine compounds, and polycyclic aromatic hydrocarbons (PAHs). In addition, at the Shoal Creek and Boggy Creek sites, individual samples for some events were analyzed to investigate within-event variation in sediment chemistry. Organochlorine compounds detected in suspended sediment included chlordane, dieldrin, DDD, DDE, DDT, and polychlorinated biphenyls (PCBs). Concentrations of PACs varied widely both within and between sites, with higher concentrations at the more urban sites and multiple nondetections at the least-urban sites. Within-site variation for metals and PAHs was smaller than between-site variation, and concentrations and yields of these and the organochlorine compounds correlated positively to the percentage of urban land use in the watershed. Loads of most PACs tested correlated significantly with suspended-sediment loads. Concentrations of most PACs correlated strongly with three measures of urban land use. Variation in suspended-sediment chemistry during runoff events was investigated at the Shoal and Boggy Creek sites. Five of the eight metals analyzed, dieldrin, chlordane, PCBs, and PAHs were detected at the highest concentrations in the first sample collected at the Shoal Creek site, a first-flush effect, but not at the Boggy Creek site. Temporal patterns in concentrations of DDT and its breakdown products varied from one event to the next. In spite of the first-flush effect in concentrations at the Shoal Creek site, most of the contaminant load was transported at peak discharge, when suspended-sediment concentration and load are maximum.

Scientific Investigations Report↗

USGS1996

Comparison of estimated and observed stormwater runoff for fifteen watersheds in west-central Florida, using five common design techniques

Hydrologists use several traditional techniques for estimating peak discharges and runoff volumes from ungaged watersheds. However, applying these techniques to watersheds in west-central Florida requires that empirical relationships be extrapolated beyond tested ranges. As a result there is some uncertainty as to their accuracy. Sixty-six storms in 15 west-central Florida watersheds were modeled using (1) the rational method, (2) the U.S. Geological Survey regional regression equations, (3) the Natural Resources Conservation Service (formerly the Soil Conservation Service) TR-20 model, (4) the Army Corps of Engineers HEC-1 model, and (5) the Environmental Protection Agency SWMM model. The watersheds ranged between fully developed urban and undeveloped natural watersheds. Peak discharges and runoff volumes were estimated using standard or recommended methods for determining input parameters. All model runs were uncalibrated and the selection of input parameters was not influenced by observed data. The rational method, only used to calculate peak discharges, overestimated 45 storms, underestimated 20 storms and estimated the same discharge for 1 storm. The mean estimation error for all storms indicates the method overestimates the peak discharges. Estimation errors were generally smaller in the urban watersheds and larger in the natural watersheds. The U.S. Geological Survey regression equations provide peak discharges for storms of specific recurrence intervals. Therefore, direct comparison with observed data was limited to sixteen observed storms that had precipitation equivalent to specific recurrence intervals. The mean estimation error for all storms indicates the method over estimates both peak discharges and runoff volumes. Estimation errors were smallest for the larger natural watersheds in Sarasota County, and largest for the small watersheds located in the eastern part of the study area. The Natural Resources Conservation Service TR-20 model, overestimated peak discharges for 45 storms and underestimated 21 storms, and overestimated runoff volumes for 44 storms and underestimated 22 storms. The mean estimation error for all storms modeled indicates that the model overestimates peak discharges and runoff volumes. The smaller estimation errors in both peak discharges and runoff volumes were for storms occurring in the urban watersheds, and the larger errors were for storms occurring in the natural watersheds. The HEC-1 model overestimated peak discharge rates for 55 storms and underestimated 11 storms. Runoff volumes were overestimated for 44 storms and underestimated for 22 storms using the Army Corps of Engineers HEC-1 model. The mean estimation error for all the storms modeled indicates that the model overestimates peak discharge rates and runoff volumes. Generally, the smaller estimation errors in peak discharges were for storms occurring in the urban watersheds, and the larger errors were for storms occurring in the natural watersheds. Estimation errors in runoff volumes; however, were smallest for the 3 natural watersheds located in the southernmost part of Sarasota County. The Environmental Protection Agency Storm Water Management model produced similar peak discharges and runoff volumes when using both the Green-Ampt and Horton infiltration methods. Estimated peak discharge and runoff volume data calculated with the Horton method was only slightly higher than those calculated with the Green-Ampt method. The mean estimation error for all the storms modeled indicates the model using the Green-Ampt infiltration method overestimates peak discharges and slightly underestimates runoff volumes. Using the Horton infiltration method, the model overestimates both peak discharges and runoff volumes. The smaller estimation errors in both peak discharges and runoff volumes were for storms occurring in the five natural watersheds in Sarasota County with the least amount of impervious cover and the lowest slopes. The largest errors were for storms occurring in the three small natural watersheds in the eastern part of the study area. The mean estimation errors for peak discharge ranged from an underestimation of 63 percent to an overestimation of 224 percent. For runoff volume, the mean estimation errors range from an underestimation of 63.3 percent to an overestimation of 267 percent.

Florida↗