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Tennessee Valley Authority Watershed Protection and Improvement
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This presentation details how TVA is providing adequate data for sound decision-making, identifying and build partnerships, partnering to prioritize watersheds and projects, and implementing projects to protect water quality and biodiversity.
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Cooperative
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Past SC Meetings and Materials
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July 13-15, 2015 Appalachian LCC Steering Committee Meeting
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Hydrologic Units within the Tennessee River Basin
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Unit name and total area (square miles) for 2, 4, 6, and 8 digit hydrologic units within the Tennessee River System.
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Reports & Documents
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A LIDAR‐DERIVED EVALUATION OF WATERSHED‐SCALE LARGE WOODY DEBRIS SOURCES AND RECRUITMENT MECHANISMS: COASTAL MAINE, USA
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In‐channel large woody debris (LWD) promotes quality aquatic habitat through sediment sorting, pool scouring and in‐stream nutrient retention and transport. LWD recruitment occurs by numerous ecological and geomorphic mechanisms including channel migration, mass wasting and natural tree fall, yet LWD sourcing on the watershed scale remains poorly constrained. We developed a rapid and spatially extensive method for using light detection and ranging data to do the following: (i) estimate tree height and recruitable tree abundance throughout a watershed; (ii) determine the likelihood for the stream to recruit channel‐spanning trees at reach scales and assess whether mass wasting or channel migration is a dominant recruitment mechanism; and (iii) understand the contemporary and future distribution of LWD at a watershed scale. We utilized this method on the 78‐km‐long Narraguagus River in coastal Maine and found that potential channel‐spanning LWD composes approximately 6% of the valley area over the course of the river and is concentrated in spatially discrete reaches along the stream, with 5 km of the river valley accounting for 50% of the total potential LWD found in the system. We also determined that 83% of all potential LWD is located on valley sides, as opposed to 17% on floodplain and terrace surfaces. Approximately 3% of channel‐spanning vegetation along the river is located within one channel width of the stream. By examining topographic and morphologic variables (valley width, channel sinuosity, valley‐ side slope) over the length of the stream, we evaluated the dominant recruitment processes along the river and often found a spatial disconnect between the location of potential channel‐spanning LWD and recruitment mechanisms, which likely explains the low levels of LWD currently found in the system. This rapid method for identification of LWD sources is extendable to other basins and may prove valuable in locating future restoration projects aimed at increasing habitat quality through wood additions.
key words: large woody debris; lidar; river restoration; habitat
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Resources
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Climate Science Documents
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Carbon sequestration in the U.S. forest sector from 1990 to 2010
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From 1990 through 2005, the forest sector (including forests and wood products) sequestered an average 162 Tg C year1 . In 2005, 49% of the total forest sector sequestration was in live and dead trees, 27% was
in wood products in landfills, with the remainder in down dead wood, wood products in use, and forest floor and soil. The pools with the largest carbon stocks were not the same as those with the largest sequestration rates, except for the tree pool. For example, landfilled wood products comprise only 3% of total stocks but account for 27% of carbon sequestration. Conversely, forest soils comprise 48% of total stocks but account for only 2% of carbon sequestration. For the tree pool, the spatial pattern of carbon stocks was dissimilar to that of carbon flux. On an area basis, tree carbon stocks were highest in the Pacific Northwest, while changes were generally greatest in the upper Midwest and the Northeast. Net carbon sequestration in the forest sector in 2005 offset 10% of U.S. CO2 emissions. In the near future, we project that U.S. forests will continue to sequester carbon at a rate similar to that in recent years. Based on a comparison of our estimates to a compilation of land-based estimates of non-forest carbon sinks from the literature, we estimate that the conterminous U.S. annually sequesters 149–330 Tg C year1. Forests, urban trees, and wood products are responsible for 65–91% of this sink.
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Resources
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Climate Science Documents
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Columbia Water Center White Paper America’s Water Risk: Water Stress and Climate Variability
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The emerging awareness of the dependence of business on water has resulted in increasing awareness of the concept of “Water Risk” and the diverse ways in which water can pose threats to businesses in certain regions and sectors. Businesses seek to secure sustainable income. To do so, they need to maintain a
competitive advantage and brand differentiation. They need secure and stable supply chains. Their exposure risks related to increasing scarcity of water can come in a variety of forms at various points in the supply chain. Given increasing water scarcity and the associated deterioration of the quantity and quality of water sources in many parts of the world, many “tools” have been developed to map water scarcity riskor water risk. Typically, these tools are based on estimates of the average water supply and demand in each unit of analysis.Often, they are associated with river basins, while business is associated with cities or counties. They provide a useful first look at the potential imbalance of supply and demand to businesses.
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Resources
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Climate Science Documents
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Aeolian process effects on vegetation communities in an arid grassland ecosystem
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Many arid grassland communities are changing from grass dominance to shrub
dominance, but the mechanisms involved in this conversion process are not completely
understood. Aeolian processes likely contribute to this conversion from
grassland to shrubland. The purpose of this research is to provide information
regarding how vegetation changes occur in an arid grassland as a result of aeolian
sediment transport. The experimental design included three treatment blocks, each
with a 25 × 50 m area where all grasses, semi-shrubs, and perennial forbs were
hand removed, a 25 × 50 m control area with no manipulation of vegetation cover,
and two 10 × 25 m plots immediately downwind of the grass-removal and control
areas in the prevailing wind direction, 19◦ north of east, for measuring vegetation
cover. Aeolian sediment flux, soil nutrients, and soil seed bank were monitored on
each treatment area and downwind plot. Grass and shrub cover were measured on
each grass-removal, control, and downwind plot along continuous line transects as
well as on 5 × 10 m subplots within each downwind area over four years following
grass removal. On grass-removal areas, sediment flux increased significantly, soil
nutrients and seed bank were depleted, and Prosopis glandulosa shrub cover increased
compared to controls. Additionally, differential changes for grass and shrub
cover were observed for plots downwind of vegetation-removal and control areas.
Grass cover on plots downwind of vegetation-removal areas decreased over time
(2004–2007) despite above average rainfall throughout the period of observation,
while grass cover increased downwind of control areas; P. glandulosa cover increased
on plots downwind of vegetation-removal areas, while decreasing on plots downwind
of control areas. The relationships between vegetation changes and aeolian
sediment flux were significant and were best described by a logarithmic function,
with decreases in grass cover and increases in shrub cover occurring with small
increases in aeolian sediment flux
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Resources
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Climate Science Documents
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Adaptation: Planning for Climate Change and Its Effects on Federal Lands
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National forest managers are charged with tackling the effects of climate change on the natural resources
under their care. The Forest Service National Roadmap for Responding to Climate Change and the Climate
Change Performance Scorecard require managers to make significant progress in addressing climate
change by 2015. To help land managers meet this challenge, Forest Service scientists conducted three case studies on national forests and adjacent national parks and documented a wide range of scientific issues and solutions. They summarized the scientific foundation for climate change adaptation and made the information accessible to land managers by creating a climate change adaptation guidebookand web portal. Case study teams discovered that collaboration among scientists and land managers is crucial to adaptation planning, as are management plans targeted to the particular ecosystem conditions and management priorities of each region. Many current management practices are consistent with climate change
adaptation goals. Because timely implementation is critical, strategies are in development at the national
level to speed the implementation of science-based climate change adaptation processes in national
forests throughout the country.
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Climate Science Documents
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Biotic Multipliers of Climate Change
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A focus on species interactions may improve predictions of the effects of climate change
on ecosystems.
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Resources
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Climate Science Documents
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Drought Sensitivity of the Amazon Rainforest
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Amazon forests are a key but poorly understood component of the global carbon cycle. If, as
anticipated, they dry this century, they might accelerate climate change through carbon losses and
changed surface energy balances. We used records from multiple long-term monitoring plots across
Amazonia to assess forest responses to the intense 2005 drought, a possible analog of future events.
Affected forest lost biomass, reversing a large long-term carbon sink, with the greatest impacts
observed where the dry season was unusually intense. Relative to pre-2005 conditions, forest subjected
to a 100-millimeter increase in water deficit lost 5.3 megagrams of aboveground biomass of carbon per
hectare. The drought had a total biomass carbon impact of 1.2 to 1.6 petagrams (1.2 × 1015 to
1.6 × 1015 grams). Amazon forests therefore appear vulnerable to increasing moisture stress, with the
potential for large carbon losses to exert feedback on climate change.
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Climate Science Documents
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Effects of Urbanization and Climate Change on Stream Health
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Estimation of stream health involves the analysis of changes in aquatic species, riparian vegetation, microinvertebrates, and channel degradation due to hydrologic changes occurring from anthropogenic activities. In this study, we quantified stream health changes arising from urbanization and climate change using a combination of the widely accepted Indicators of Hydrologic Alteration (IHA) and Dundee Hydrologic Regime Assessment Method (DHRAM) on a rapidly urbanized watershed in the Dallas-Fort Worth metropolitan area in Texas. Historical flow data were split into pre-alteration and post-alteration periods. The influence of climate change on stream health was analyzed by dividing the precipitation data into three groups of dry, average, and wet conditions based on recorded annual precipitation. Hydrologic indicators were evaluated for all three of the climate scenarios to estimate the stream health changes brought about by climate change. The effect of urbanization on stream health was analyzed for a specific subwatershed where urbanization occurred dramatically but no stream flow data were available using the widely used watershed-scale Soil and Water Assessment Tool (SWAT) model. The results of this study identify negative impacts to stream health with increasing urbanization and indicate that dry weather has more impact on stream health than wet weather. The IHA-DHRAM approach and SWAT model prove to be useful tools to estimate stream health at the watershed scale.
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Climate Science Documents
