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At least 235 records · Page 13Linked to original sources
USGS2012

The interactive effects of excess reactive nitrogen and climate change on aquatic ecosystems and water resources of the United States

Nearly all freshwaters and coastal zones of the US are degraded from inputs of excess reactive nitrogen (Nr), sources of which are runoff, atmospheric N deposition, and imported food and feed. Some major adverse effects include harmful algal blooms, hypoxia of fresh and coastal waters, ocean acidification, long-term harm to human health, and increased emissions of greenhouse gases. Nitrogen fluxes to coastal areas and emissions of nitrous oxide from waters have increased in response to N inputs. Denitrification and sedimentation of organic N to sediments are important processes that divert N from downstream transport. Aquatic ecosystems are particularly important denitrification hotspots. Carbon storage in sediments is enhanced by Nr, but whether carbon is permanently buried is unknown. The effect of climate change on N transport and processing in fresh and coastal waters will be felt most strongly through changes to the hydrologic cycle, whereas N loading is mostly climate-independent. Alterations in precipitation amount and dynamics will alter runoff, thereby influencing both rates of Nr inputs to aquatic ecosystems and groundwater and the water residence times that affect Nr removal within aquatic systems. Both infrastructure and climate change alter the landscape connectivity and hydrologic residence time that are essential to denitrification. While Nr inputs to and removal rates from aquatic systems are influenced by climate and management, reduction of N inputs from their source will be the most effective means to prevent or to minimize environmental and economic impacts of excess Nr to the nation’s water resources.

Biogeochemistry↗
USGS1978

Coastal mapping handbook

Passage of the Coastal Zone Management Act of 1972 focused attention on the Nation's coastal land and water areas. As plans for more effective management of the coastal zone evolved, it soon became apparent that improved maps and charts of these areas were needed. This handbook was prepared with the requirements of the entire coastal community in mind, giving greatest attention to the needs of coastal zone managers and planners at the State and local levels. Its principal objective is to provide general information and guidance; it is neither a textbook nor a technical manual, but rather a primer on coastal mapping. This handbook should help planners and managers of coastal programs to determine their mapping requirements, select the best maps and charts for their particular needs, and to deal effectively with personnel who gather data and prepare maps. The sections on "Sources of Assistance and Advice" and "Product and Data Sources" should be especially useful to all involved in mapping the coastal zone. Brief summaries of the mapping efforts of several State coastal zone management programs are included. "Future outlook" discusses anticipated progress and changes in mapping procedures and techniques. Illustrations are inserted, where appropriate, to illustrate the products and equipment discussed. Because of printing restrictions, the colors in map illustrations may vary from those in the original publication. The appendixes include substantial material which also should be of interest. In addition a glossary and an index are included to provide easy and quick access to the terms and concepts used in the text. For those interested in more technical detail than is provided in this handbook, the "Selected references" will be useful. Also, the publications of the professional societies listed in appendix 4 will provide technical information in detail.

Report↗
USGS2018

The North American carbon budget: Past, present, and future

This chapter nicely summarizes and synthesizes the latest scientific information on the North American carbon budget by incorporating terrestrial, anthropogenic, aquatic, and coastal margin CO 2 and CH 4 dynamics. Starting with a historical context, the chapter summarizes current understanding of the magnitudes and trends of carbon stocks and fluxes at the continental scale. It also provides a regional context by stratifying the continent to countries and climate assessment regions and discusses the societal drivers, impacts, and carbon management decisions. Knowledge gaps and research needs are also identified. This chapter is well-written and clearly organized, and provides a broad context beyond individual chapters. Some of the main ways the chapter can be improved include the following: some work is needed on the Key Findings (discussed below); the goals and objectives should be explicitly described; critical content areas missing from the chapter are interannual variability of carbon fluxes and impacts of severe and extended droughts; indicators and feedbacks are missing from Section 2.4; consistent use of units is recommended; numbers with 3-4 significant digits over-state the confidence the reader should have, and all numbers should include uncertainties. And one broader concern to note: This chapter follows the global overview in Chapter 1, where “sinks” are sinks in the cycle perturbed by anthropogenic CO 2 and CH 4 , and the assumption is that globally, the net unperturbed background sinks are zero summed across all reservoirs. Yet in this chapter, “sinks” are net fluxes out of the atmosphere, background + perturbation. For the coastal ocean, inland waters, etc.—where lateral transport is significant—these sources and sinks include background/pre-industrial fluxes that are balanced by fluxes elsewhere. These distinctions must be made clear so that the reader is not given an impression of a greater or lesser sink for anthropogenic CO 2 than is there (e.g., P74, lines 4-6).

Book chapter↗
USGS2018

Efficacy of otoliths and first dorsal spines for preliminary age and growth determination in Atlantic Tripletails

The Atlantic Tripletail Lobotes surinamensis is a popular sport fish for which age and growth data are scarce in general and nonexistent for Georgia (GA), USA, waters. These data are necessary to ensure that management regulations are adequate to protect this species, especially given its popularity as a sport fish. We evaluated whether otoliths and spines were suitable for determining the estimated age (hereafter, “age”) and growth rates of Atlantic Tripletails, and we ascertained whether one method was more accurate than the other. Atlantic Tripletails were sampled by angling and trawling during March 30–August 10, 2009, and March 14–August 6, 2010, in nearshore GA waters of the Atlantic Ocean. During the study, 243 Atlantic Tripletails were captured and sampled for aging structures. Sagittal otoliths and the first dorsal spine were removed from each fish and used to estimate the age and growth rate. Mean differences in TL at age for spine and otolith data were evaluated with ANOVA. Estimated ages for males and females ranged from 1 to 5 years based on otoliths and spines. Both otolith and spine mean TLs at ages 1 and 2 were significantly different from each other as well as all other age‐classes, whereas mean TLs for ages 3–5 were not significantly different. Differences in Atlantic Tripletail TL among the otolith‐ and spine‐derived age‐classes were not significant. Each method used to age Atlantic Tripletails had advantages and disadvantages. Otoliths had higher initial reader agreement than spines, although agreement between the structures was 84.1%. However, otoliths require sacrifice of the fish, whereas a spine can be taken without sacrificing the fish. The lack of concrete life history data and population estimates suggests that when feasible, nonlethal aging methods would be preferred over lethal methods to ensure the survival of Atlantic Tripletail populations.

Georgia↗
USGS2013

Statewide summary for Florida

Throughout the past century, emergent wetlands have been declining across the Gulf of Mexico. Emergent wetland ecosystems provide a multitude of resources, including plant and wildlife habitat, commercial and recreational economic activity, and natural barriers against storms. As emergent wetland losses increase, so does the need for information on the causes and effects of this loss; emergent wetland mapping, monitoring, and restoration efforts; and education. This report provides scientists, managers, and citizens with valuable baseline information on the status and trends of emergent wetlands along the coast of the Gulf of Mexico. The Statewide Summary for Florida provides status and trends information for Florida using what data is available during the 1950-2010 time period. The State of Florida (Figure 1) is approximately 151,670 km2 (58,560 mi2 ) large with an average elevation of 30.5 m (100 ft) (Dahl, 2005). The Florida gulf coast stretches approximately 1,000 km (621 miles) from the Alabama State line to the Dry Tortugas in the Florida Keys (Handley et al., 2007). The climate varies along the coast, ranging from temperate continental in the panhandle to oceanic subtropical in the Keys. Due to this climatic gradient, the Gulf coast of Florida is divisible into two ecoregions, the Louisianian in the north along the panhandle, and the West Indian in the south along the length of the peninsula (Bailey 1978). The Lousianian ecoregion extends from Cedar Key north and west along the panhandle to the Alabama state line. It is characterized by extensive emergent coastal wetlands, temperate fauna, small tidal ranges (

Florida↗
USGS2016

Estuary-ocean connectivity: Fast physics, slow biology

Estuaries are connected to both land and ocean so their physical, chemical, and biological dynamics are influenced by climate patterns over watersheds and ocean basins. We explored climate-driven oceanic variability as a source of estuarine variability by comparing monthly time series of temperature and chlorophyll- a inside San Francisco Bay with those in adjacent shelf waters of the California Current System (CCS) that are strongly responsive to wind-driven upwelling. Monthly temperature fluctuations inside and outside the Bay were synchronous, but their correlations weakened with distance from the ocean. These results illustrate how variability of coastal water temperature (and associated properties such as nitrate and oxygen) propagates into estuaries through fast water exchanges that dissipate along the estuary. Unexpectedly, there was no correlation between monthly chlorophyll- a variability inside and outside the Bay. However, at the annual scale Bay chlorophyll- a was significantly correlated with the Spring Transition Index (STI) that sets biological production supporting fish recruitment in the CCS. Wind forcing of the CCS shifted in the late 1990s when the STI advanced 40 days. This shift was followed, with lags of 1–3 years, by 3- to 19-fold increased abundances of five ocean-produced demersal fish and crustaceans and 2.5-fold increase of summer chlorophyll- a in the Bay. These changes reflect a slow biological process of estuary–ocean connectivity operating through the immigration of fish and crustaceans that prey on bivalves, reduce their grazing pressure, and allow phytoplankton biomass to build. We identified clear signals of climate-mediated oceanic variability in this estuary and discovered that the response patterns vary with the process of connectivity and the timescale of ocean variability. This result has important implications for managing nutrient inputs to estuaries connected to upwelling systems, and for assessing their responses to changing patterns of upwelling timing and intensity as the planet continues to warm.

California↗
USGS2014

Organization of marine phenology data in support of planning and conservation in ocean and coastal ecosystems

Among the many effects of climate change is its influence on the phenology of biota. In marine and coastal ecosystems, phenological shifts have been documented for multiple life forms; however, biological data related to marine species' phenology remain difficult to access and is under-used. We conducted an assessment of potential sources of biological data for marine species and their availability for use in phenological analyses and assessments. Our evaluations showed that data potentially related to understanding marine species' phenology are available through online resources of governmental, academic, and non-governmental organizations, but appropriate datasets are often difficult to discover and access, presenting opportunities for scientific infrastructure improvement. The developing Federal Marine Data Architecture when fully implemented will improve data flow and standardization for marine data within major federal repositories and provide an archival repository for collaborating academic and public data contributors. Another opportunity, largely untapped, is the engagement of citizen scientists in standardized collection of marine phenology data and contribution of these data to established data flows. Use of metadata with marine phenology related keywords could improve discovery and access to appropriate datasets. When data originators choose to self-publish, publication of research datasets with a digital object identifier, linked to metadata, will also improve subsequent discovery and access. Phenological changes in the marine environment will affect human economics, food systems, and recreation. No one source of data will be sufficient to understand these changes. The collective attention of marine data collectors is needed—whether with an agency, an educational institution, or a citizen scientist group—toward adopting the data management processes and standards needed to ensure availability of sufficient and useable marine data to understand marine phenology.

Ecological Informatics↗
USGS2023

Volcanic aquifers of Hawaiʻi—Contributions to assessing groundwater availability on Kauaʻi, Oʻahu, and Maui

The volcanic aquifers of the Hawaiian Islands supply water to 1.46 million residents, diverse industries, and a large component of the U.S. military in the Pacific. Groundwater also supplies fresh water that supports ecosystems in streams and near the coast. Hawaii’s aquifers are remarkably productive given their small size, but the capacity of the islands to store fresh groundwater is limited because each island is surrounded by seawater, and salt water underlies much of the fresh groundwater. The amount of fresh groundwater available for human use from Hawai‘i’s volcanic aquifers is constrained by the consequences of groundwater withdrawal. Restrictions placed on these consequences can translate to limitations on groundwater availability. Changes in recharge resulting from changes in land cover or climate can alter the effect of withdrawals. This study uses numerical models of the volcanic aquifers of the islands of Kaua‘i, O‘ahu, and Maui to quantify the consequences of historical and plausible future withdrawals and changes in recharge. The study compares the results of model simulations of multiple scenarios of historical and projected future withdrawal and recharge. Results of the simulations using the groundwater models of the islands of Kaua‘i, O‘ahu, and Maui have implications for other islands in Hawai‘i. Since the first modern water well was drilled in Hawai‘i in 1879, total groundwater withdrawals on Kaua‘i, O‘ahu, and Maui have risen to nearly 400 million gallons per day. Model simulations indicate that these withdrawals have caused reductions in groundwater discharge to streams and springs, reductions in groundwater discharge to the ocean, changes in subsurface flow between sectors within an island, lowering of groundwater levels, and rise of the interface between fresh water and salt water in the aquifers. Future increases in withdrawals will increase the severity of the consequences. Changes in recharge can alter the effect of withdrawals—increases in recharge can offset the consequences of withdrawals, whereas decreases in recharge can exacerbate the effects of withdrawals. This study quantifies the consequences of withdrawals for past and plausible future circumstances. The models can be used to test other circumstances. Limits placed on the consequences of withdrawals—such as restrictions to protect stream or coastal ecosystems that rely on groundwater discharge and limitations on water-level decline and rise of the freshwater-saltwater interface to protect the productivity of existing wells—can translate to limits on groundwater availability from Hawai‘i’s volcanic aquifers. Setting acceptable limits to the consequences of groundwater withdrawal is also a critical part of assessing groundwater availability. Once these limits are set, numerical models can be used to quantify the amount of water that can be withdrawn within those limits and thereby inform management decisions that seek to balance the need to limit the consequences of groundwater withdrawals with the need to develop water for human use.

Hawaii↗
USGS2014

Sea-floor morphology and sedimentary environments of western Block Island Sound, northeast of Gardiners Island, New York

Multibeam-echosounder data, collected during survey H12299 by the National Oceanic and Atmospheric Administration in a 162-square-kilometer area of Block Island Sound, northeast of Gardiners Island, New York, are used along with sediment samples and bottom photography, collected at 37 stations in this area by the U.S. Geological Survey during cruise 2013-005-FA, to interpret sea-floor features and sedimentary environments. These data and interpretations provide important base maps for future studies of the sea floor, focused, for example, on benthic ecology and resource management. The features and sedimentary environments on the sea floor are products of the glacial history and modern tidal regime. Features include bedforms such as sand waves and megaripples, boulders, a large current-scoured depression, exposed glaciolacustrine sediments, and areas of modern marine sediment. Sand covers much of the study area and is often in the form of sand waves and megaripples, which indicate environments characterized by coarse-grained bedload transport. Boulders and gravelly lag deposits, which indicate environments of erosion or nondeposition, are found off the coast of Gardiners Island and on bathymetric highs, probably marking areas where deposits associated with recessional ice-front positions, the northern flank of the terminal moraine, or coastal-plain sediments covered with basal till are exposed. Bottom photographs and video of boulders show that they are commonly covered with sessile fauna. Strong tidal currents have produced the deep scour depression along the northwestern edge of the study area. The eastern side of this depression is armored with a gravel lag. Sea-floor areas characterized by modern marine sediments appear featureless at the 2-meter resolution of the bathymetry and flat to current rippled in the photography. These modern environments are indicative of sediment sorting and reworking.

New York↗
USGS2008

Hydrogeology of the Islamic Republic of Mauritania

Hydrogeologic maps were constructed for the Islamic Republic of Mauritania. The ground-water flow system in the country can best be described as two interconnected regional systems: the porous Continental Terminal coastal system and the interior, fractured sedimentary Taoudeni Basin system. In these systems, ground-water flow occurs in fill deposits and carbonate, clastic, metasedimentary, and metavolcanic rocks. Based on an evaluation of the potentiometric surface, there are three areas of ground-water recharge in the Taoudeni Basin system. One region occurs in the northwest at the edge of the Shield, one occurs to the south overlying the Tillites, and one is centered at the city of Tidjikdja. In contrast to the flow system in the Taoudeni Basin, the potentiometric surfaces reveal two areas of discharge in the Continental Terminal system but no localized recharge areas; the recharge is more likely to be areal. In addition to these recharge and discharge areas, ground water flows across the country's borders. Specifically, ground water from the Atlantic Ocean flows into Mauritania, transporting dissolved sodium from the west as a salt water intrusion, whereas fresh ground water discharges from the east into Mali. To the north, there is a relatively low gradient with inflow of fresh water to Mauritania, whereas ground-water flow discharges to the Senegal River to the south. A geographical information system (GIS) was used to digitize, manage, store, and analyze geologic data used to develop the hydrogeologic map. The data acquired for map development included existing digital GIS files, published maps, tabulated data in reports and public-access files, and the SIPPE2 Access database. Once in digital formats, regional geologic and hydrologic features were converted to a common coordinate system and combined into one map. The 42 regional geologic map units were then reclassified into 13 hydrogeologic units, each having considerable lateral extent and distinct hydrologic properties. Because the hydrologic properties of these units are also influenced by depth and degree of fracturing, the hydraulic conductivity values of these hydrogeologic units can range over many orders of magnitude.

Open-File Report↗
USGS2015

Linking behavior, physiology, and survival of Atlantic Salmon smolts during estuary migration

Decreased marine survival is identified as a component driver of continued declines of Atlantic Salmon Salmo salar . However, estimates of marine mortality often incorporate loss incurred during estuary migration that may be mechanistically distinct from factors affecting marine mortality. We examined movements and survival of 941 smolts (141 wild and 800 hatchery-reared fish) released in freshwater during passage through the Penobscot River estuary, Maine, from 2005 to 2013. We related trends in estuary arrival date, movement rate, and survival to fish characteristics, migratory history, and environmental conditions in the estuary. Fish that experienced the warmest thermal history arrived in the estuary 8 d earlier than those experiencing the coolest thermal history during development. Estuary arrival date was 10 d later for fish experiencing high flow than for fish experiencing low flow. Fish released furthest upstream arrived in the estuary 3 d later than those stocked further downstream but moved 0.5 km/h faster through the estuary. Temporally, movement rate and survival in the estuary both peaked in mid-May. Spatially, movement rate and survival both decreased from freshwater to the ocean. Wild smolts arrived in the estuary later than hatchery fish, but we observed no change in movement rate or survival attributable to rearing history. Fish with the highest gill Na + , K + -ATPase activity incurred 25% lower mortality through the estuary than fish with the lowest gill Na + , K + -ATPase activity. Smolt survival decreased (by up to 40%) with the increasing number of dams passed (ranging from two to nine) during freshwater migration. These results underscore the importance of physiological preparedness on performance and the delayed, indirect effects of dams on survival of Atlantic Salmon smolts during estuary migration, ultimately affecting marine survival estimates.

Marine and Coastal Fisheries: Dynamics, Management↗
USGS2009

The performance of nearshore dredge disposal at Ocean Beach, San Francisco, California, 2005-2007

Ocean Beach, California, contains an erosion hot spot in the shadow of the San Francisco ebb tidal delta that threatens valuable public infrastructure as well as the safe recreational use of the beach. In an effort to reduce the erosion at this location a new plan for the management of sediment dredged annually from the main shipping channel at the mouth of San Francisco Bay was implemented in May 2005 by the United States Army Corps of Engineers, San Francisco District (USACE). The USACE designated a temporary nearshore dredge disposal site for the annual disposal of about 230,000 m3 (300,000 yd3) of sand about 750 m offshore and slightly south of the erosion hot spot, in depths between approximately 9 and 14 m. The site has now been used three times for a total sediment disposal of about 690,000 m3 (about 900,000 yds3). The disposal site was chosen because it is in a location where strong tidal currents and open-ocean waves can potentially feed sediment toward the littoral zone in the reach of the beach that is experiencing critical erosion, as well as prevent further scour on an exposed outfall pipe. The onshore migration of sediment from the target disposal location might feed the primary longshore bar or the nearshore zone, and provide a buffer to erosion that peaks during winter months when large waves impact the region. The United States Geological Survey (USGS) has been monitoring and modeling the bathymetric evolution of the test dredge disposal site and the adjacent coastal region since inception in May 2005. This paper reports on the first 2.5 years of this monitoring program effort (May 2005 to December 2007) and assesses the short-term coastal response. Here are the key findings of this report: *Approximately half of the sediment that has been placed in the nearshore dredge-disposal site during the 2.5 years of this study remains within the dredge focus area. *In the winter of 2006-7, large waves transported the dredge-mound material onshore. *High rates of seasonal cross-shore sediment transport mask any potential profile change in the Coastal Profiling System data due to dredge placement. *Pockets of accretion have been recorded by topographic surveying adjacent to the dredge site, but it is unclear if the accretion is linked to the nourishment. *Cross-shore profile modeling suggests that dredge material must be placed in water depths no greater than 5 m to drive a positive shoreline response. *Area modeling demonstrates that the new dredge site increases wave dissipation and modifies local sediment-transport patterns, although the effect on the nearshore morphology is largely negligible. *Any increase in beach width or wave energy-dissipation related to the nourishment is likely to be realized only in the vicinity directly onshore of the nourishment site, which is several hundred meters south of the area of critical erosion. *Larger waves from the northwest and smaller waves from the west or southwest contribute most to the sediment transport from the dredge mound onshore.

California↗
USGS1984

Ground-water monitoring at Santa Barbara, California: Phase 2 — Effects of pumping on water levels and on water quality in the Santa Barbara ground-water basin

From July 1978 to January 1980, water levels in the southern part of the Santa Barbara ground-water basin declined more than 100 feet. These water-level declines resulted from increases in municipal pumping since July 1978. The increase in municipal pumping was part of a basin-testing program designed to determine the usable quantity of ground water in storage. The pumping, centered in the city less than 1 mile from the coast, has caused water-level declines to altitudes below sea level in the main water-bearing zones. As a result, the ground-water basin would be subject to saltwater intrusion if the study-period pumpage were maintained or increased. Data indicate that saltwater intrusion has degraded the quality of the water yielded from six coastal wells. During the study period, the six coastal wells all yielded water with chloride concentrations in excess of 250 milligrams per liter, and four of the wells yielded water with chloride concentrations in excess of 1,000 milligrams per liter. Previous investigators believed that saltwater intrusion was limited to the shallow part of the aquifer, directly adjacent to the coast. The possibility of saltwater intrusion into the deeper water-bearing deposits in the aquifer was thought to be remote because an offshore fault truncates these deeper deposits so that they lie against consolidated rocks on the seaward side of the fault. Results of this study indicate, however, that ocean water has intruded the deeper water-bearing deposits, and to a much greater extent than in the shallow part of the aquifer. Apparently the offshore fault is not an effective barrier to saltwater intrusion. No physical barriers are known to exist between the coast and the municipal well field. Therefore, if the pumping rate maintained during the basin-testing program were continued, the degraded water along the coast could move inland and contaminate the municipal supply wells. The time required for the degraded water to move from the coast to the nearest supply well is estimated, using Darcy's equation, to be about 20 years. Management alternatives for controlling saltwater intrusion in the Santa Barbara area include (1) decreasing municipal pumping, (2) increasing the quantity of water available for recharge by releasing surplus water from surface reservoirs to Mission Creek, (3) artificially recharging the basin using injection wells, and (4) locating municipal supply wells farther from the coast and spacing them farther apart in order to minimize drawdown. Continued monitoring of water levels and water quality would enable assessment of the effectiveness of the control measures employed.

California↗
USGS2025

Post-wildfire sediment fluxes and turbidity plumes in a coastal-draining watershed

Coastal watersheds impacted by wildfires experience higher erosion resulting in increased sediment delivery to the ocean that alters limiting factors (i.e., light) for marine organisms. With increasing wildfire magnitude and severity, it is critical to explore changes in riverine discharges to the ocean to assess cascading hazards associated with wildfires. In situ data, remotely sensed turbidity data, and hydrological model (Soil and Water Assessment Tool “SWAT”) simulations have been adapted to capture and investigate fire-related land use change impacts on Malibu Creek, California, USA. Modifying SWAT land cover inputs using burn severity data had minimal impact on simulations, requiring additional parameterization for acceptable model performance. Remotely sensed turbidity, in situ discharge, rating curve sediment loads, and SWAT simulated discharge and sediment loads increased following the Woolsey Fire. When compared to in situ and rating curve data in similar non-fire water years, the 2019 Woolsey Fire water year in situ discharge was 1.8 times higher, SWAT simulated discharges were 1.4–1.7 times higher, and rating curve sediment load was 1.3 times higher. However, the SWAT simulated sediment loads were slightly lower (0.8–0.9 times) than rating curve sediment loads in similar non-fire water years. Mean coastal turbidity increased to 18.2 Formazin Nephelometric Unit (FNU) during the first storm post-fire (mean background value of 4.3 FNU). Synergies between methods demonstrated rapid coastal sediment exports (remote sensing) and ongoing erosion post-fire (SWAT). These data are essential to understanding fire-related marine ecological changes and implementing effective management and conservation initiatives.

California↗
USGS1998

A simulation-optimization model for water-resources management, Santa Barbara, California

In times of drought, the local water supplies of the city of Santa Barbara, California, are insufficient to satisfy water demand. In response, the city has built a seawater desalination plant and gained access to imported water in 1997. Of primary concern to the city is delivering water from the various sources at a minimum cost while satisfying water demand and controlling seawater intrusion that might result from the overpumping of ground water. A simulation-optimization model has been developed for the optimal management of Santa Barbara?s water resources. The objective is to minimize the cost of water supply while satisfying various physical and institutional constraints such as meeting water demand, maintaining minimum hydraulic heads at selected sites, and not exceeding water-delivery or pumping capacities. The model is formulated as a linear programming problem with monthly management periods and a total planning horizon of 5 years. The decision variables are water deliveries from surface water (Gibraltar Reservoir, Cachuma Reservoir, Cachuma Reservoir cumulative annual carryover, Mission Tunnel, State Water Project, and desalinated seawater) and ground water (13 production wells). The state variables are hydraulic heads. Basic assumptions for all simulations are that (1) the cost of water varies with source but is fixed over time, and (2) only existing or planned city wells are considered; that is, the construction of new wells is not allowed. The drought of 1947?51 is Santa Barbara?s worst drought on record, and simulated surface-water supplies for this period were used as a basis for testing optimal management of current water resources under drought conditions. Assumptions that were made for this base case include a head constraint equal to sea level at the coastal nodes; Cachuma Reservoir carryover of 3,000 acre-feet per year, with a maximum carryover of 8,277 acre-feet; a maximum annual demand of 15,000 acre-feet; and average monthly capacities for the Cachuma and the Gibraltar Reservoirs. The base-case results indicate that water demands can be met, with little water required from the most expensive water source (desalinated seawater), at a total cost of $5.56 million over the 5-year planning horizon. The simulation model has drains, which operate as nonlinear functions of heads and could affect the model solutions. However, numerical tests show that the drains have little effect on the optimal solution. Sensitivity analyses on the base case yield the following results: If allowable Cachuma Reservoir carryover is decreased by about 50 percent, then costs increase by about 14 percent; if the peak demand is decreased by 7 percent, then costs will decrease by about 14 percent; if the head constraints are loosened to -30 feet, then the costs decrease by about 18 percent; if the heads are constrained such that a zero hydraulic gradient condition occurs at the ocean boundary, then the optimization problem does not have a solution; if the capacity of the desalination plant is constrained to zero acre-feet, then the cost increases by about 2 percent; and if the carryover of State Water Project water is implemented, then the cost decreases by about 0.5 percent. Four additional monthly diversion distribution scenarios for the reservoirs were tested: average monthly Cachuma Reservoir deliveries with the actual (scenario 1) and proposed (scenario 2) monthly distributions of Gibraltar Reservoir water, and variable monthly Cachuma Reservoir deliveries with the actual (scenario 3) and proposed (scenario 4) monthly distributions of Gibraltar Reservoir water. Scenario 1 resulted in a total cost of about $7.55 million, scenario 2 resulted in a total cost of about $5.07 million, and scenarios 3 and 4 resulted in a total cost of about $4.53 million. Sensitivities of the scenarios 1 and 2 to desalination-plant capacity and State Water Project water carryover were tested. The scenario 1 sensitivity analysis indicated that incorpo

Water-Resources Investigations Report↗
USGS2001

Analytical versus numerical estimates of water-level declines caused by pumping, and a case study of the Iao Aquifer, Maui, Hawaii

Comparisons were made between model-calculated water levels from a one-dimensional analytical model referred to as RAM (Robust Analytical Model) and those from numerical ground-water flow models using a sharp-interface model code. RAM incorporates the horizontal-flow assumption and the Ghyben-Herzberg relation to represent flow in a one-dimensional unconfined aquifer that contains a body of freshwater floating on denser saltwater. RAM does not account for the presence of a low-permeability coastal confining unit (caprock), which impedes the discharge of fresh ground water from the aquifer to the ocean, nor for the spatial distribution of ground-water withdrawals from wells, which is significant because water-level declines are greatest in the vicinity of withdrawal wells. Numerical ground-water flow models can readily account for discharge through a coastal confining unit and for the spatial distribution of ground-water withdrawals from wells. For a given aquifer hydraulic-conductivity value, recharge rate, and withdrawal rate, model-calculated steady-state water-level declines from RAM can be significantly less than those from numerical ground-water flow models. The differences between model-calculated water-level declines from RAM and those from numerical models are partly dependent on the hydraulic properties of the aquifer system and the spatial distribution of ground-water withdrawals from wells. RAM invariably predicts the greatest water-level declines at the inland extent of the aquifer where the freshwater body is thickest and the potential for saltwater intrusion is lowest. For cases in which a low-permeability confining unit overlies the aquifer near the coast, however, water-level declines calculated from numerical models may exceed those from RAM even at the inland extent of the aquifer. Since 1990, RAM has been used by the State of Hawaii Commission on Water Resource Management for establishing sustainable-yield values for the State?s aquifers. Data from the Iao aquifer, which lies on the northeastern flank of the West Maui Volcano and which is confined near the coast by caprock, are now available to evaluate the predictive capability of RAM for this system. In 1995 and 1996, withdrawal from the Iao aquifer reached the 20 million gallon per day sustainable-yield value derived using RAM. However, even before 1996, water levels in the aquifer had declined significantly below those predicted by RAM, and continued to decline in 1997. To halt the decline of water levels and to preclude the intrusion of salt-water into the four major well fields in the aquifer, it was necessary to reduce withdrawal from the aquifer system below the sustainable-yield value derived using RAM. In the Iao aquifer, the decline of measured water levels below those predicted by RAM is consistent with the results of the numerical model analysis. Relative to model-calculated water-level declines from numerical ground-water flow models, (1) RAM underestimates water-level declines in areas where a low-permeability confining unit exists, and (2) RAM underestimates water-level declines in the vicinity of withdrawal wells.

Hawaii↗
USGS2013

Integrated carbon budget models for the Everglades terrestrial-coastal-oceanic gradient: Current status and needs for inter-site comparisons

Recent studies suggest that coastal ecosystems can bury significantly more C than tropical forests, indicating that continued coastal development and exposure to sea level rise and storms will have global biogeochemical consequences. The Florida Coastal Everglades Long Term Ecological Research (FCE LTER) site provides an excellent subtropical system for examining carbon (C) balance because of its exposure to historical changes in freshwater distribution and sea level rise and its history of significant long-term carbon-cycling studies. FCE LTER scientists used net ecosystem C balance and net ecosystem exchange data to estimate C budgets for riverine mangrove, freshwater marsh, and seagrass meadows, providing insights into the magnitude of C accumulation and lateral aquatic C transport. Rates of net C production in the riverine mangrove forest exceeded those reported for many tropical systems, including terrestrial forests, but there are considerable uncertainties around those estimates due to the high potential for gain and loss of C through aquatic fluxes. C production was approximately balanced between gain and loss in Everglades marshes; however, the contribution of periphyton increases uncertainty in these estimates. Moreover, while the approaches used for these initial estimates were informative, a resolved approach for addressing areas of uncertainty is critically needed for coastal wetland ecosystems. Once resolved, these C balance estimates, in conjunction with an understanding of drivers and key ecosystem feedbacks, can inform cross-system studies of ecosystem response to long-term changes in climate, hydrologic management, and other land use along coastlines

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USGS2015

The surface elevation table and marker horizon technique: A protocol for monitoring wetland elevation dynamics

The National Park Service, in response to the growing evidence and awareness of the effects of climate change on federal lands, determined that monitoring wetland elevation change is a top priority in North Atlantic Coastal parks (Stevens et al, 2010). As a result, the NPS Northeast Coastal and Barrier Network (NCBN) in collaboration with colleagues from the U.S. Geological Survey (USGS) and The National Oceanic and Atmospheric Administration (NOAA) have developed a protocol for monitoring wetland elevation change and other processes important for determining the viability of wetland communities. Although focused on North Atlantic Coastal parks, this document is applicable to all coastal and inland wetland regions. Wetlands exist within a narrow range of elevation which is influenced by local hydrologic conditions. For coastal wetlands in particular, local hydrologic conditions may be changing as sea levels continue to rise. As sea level rises, coastal wetland systems may respond by building elevation to maintain favorable hydrologic conditions for their survival. This protocol provides the reader with instructions and guidelines on designing a monitoring plan or study to: A) Quantify elevation change in wetlands with the Surface Elevation Table (SET). B) Understand the processes that influence elevation change, including vertical accretion (SET and Marker Horizon methods). C) Survey the wetland surface and SET mark to a common reference datum to allow for comparing sample stations to each other and to local tidal datums. D) Survey the SET mark to monitor its relative stability. This document is divided into two parts; the main body that presents an overview of all aspects of monitoring wetland elevation dynamics, and a collection of Standard Operating Procedures (SOP) that describes in detail how to perform or execute each step of the methodology. Detailed instruction on the installation, data collection, data management and analysis are provided in this report and associated SOP’s. A better understanding of these processes will help to determine the present and future viability of coastal wetlands managed by NPS and can help address measures that will ensure these communities exist into the future.

Natural Resource Report↗