Archive for the ‘Article Highlights’ Category

New England flood frequencies increasing

Monday, March 12th, 2012

April 2012 article (Early View): “Increased Frequency of Low-Magnitude Floods in New England,” by William H. Armstrong, Mathias J. Collins, and Noah P. Snyder.

Although catastrophic floods are usually responsible for channel avulsions, stream barrier breaches (e.g., dams), and transporting large bed-load particles, floods occurring every one or two years are more active agents in shaping the prevailing channel dimensions because of their frequency and ability to erode and transport bank and bed material. Frequent, low-magnitude floods are also important for riparian and aquatic habitat.

The authors selected gauges from the USGS Hydro-Climatic Data Network (HCDN), a compilation of river gauges that are minimally affected by human use and are the best available representation of natural streamflow throughout the U.S. They found widespread upward trends in peak over threshold per water year (POT/WY) – a direct measure of increasing flood frequency – on New England rivers. Twenty-two of 23 study gauges selected for climate sensitivity show increasing trends in POT/WY through the analysis of long-term records. They found evidence for a step increase in POT/WY around 1970 on more than half of the rivers, and seven rivers show evidence for a step increase in flood discharge, supporting recent studies noting change points in time series of various hydrologic variables around that time.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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Collaborative watershed management

Friday, March 9th, 2012

April 2012 article (Early View): “Stakeholder Analysis of a Collaborative Watershed Management Process: A Florida Case Study,” by Tatiana Borisova, Laila Racevskis, and Jennison Kipp.

[Straight from a good abstract.] This study focuses on a Florida watershed where development of a total maximum daily load (TMDL) and its implementation plan resulted in conflicts among stakeholders. The overall goal is to build a better understanding of stakeholder perceptions of water quality problems, water policy processes and decisions, and water management plan development in a region where these issues have become contentious. Findings are based on a stakeholder analysis using qualitative data collected through focus groups with agricultural producers, local governments, and environmental groups, and supplemented with additional qualitative data on the watershed management process. Stakeholder conflicts in this case study are associated with perceived flaws in the structural and procedural characteristics of the stakeholder involvement process: (1) suboptimal watershed stakeholder representation on the TMDL executive committee, (2) an inappropriate voting procedure for making TMDL decisions, (3) limitations in information sharing between regulatory agencies and watershed stakeholders, and (4) stakeholders’ doubts about whether tradeoffs associated with achieving the water quality targets were assessed adequately throughout the TMDL planning and implementation process. This study contributes to the literature on collaborative watershed management by analyzing stakeholder involvement given Florida’s unique institutional settings, where implementation of TMDL pollution abatement is mandatory.

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Composite efficiency indicators

Thursday, March 8th, 2012

April 2012 article (Early View): “Macro, Meso, and Micro-Efficiencies in Water Resources Management: A New Framework Using Water Balance,” by Naim Hale and Andrew A. Keller.

In this paper, performance composite indicators are developed in order to determine efficiency using water balance. Total flow used in this law of conservation of mass can be total inflow into a water resources system (WRS) or total consumption out of it. It is important to use both of these two types when conducting any systems analysis and design. But in order to expand the utility of the indicators so that decision makers can use them, this paper goes beyond the pure hydrology of a WRS and employs an important concept called “Usefulness Criterion,” which is incorporated into the water balance through a logical approach. In this process, two dimensions are identified: one deals with the quality and the other with the beneficial use of water. Both of these are determined through weights given by the manager based on physical characteristics of used and reused water, system quality, and management goals. Management goals are particularly relevant because, for example, a decision maker or a consultant should decide on the acceptable salt tolerance for an irrigation system design or acceptable pollution for the downstream ecosystem. In this regard it should be noted that societies and political processes are getting involved in making judgments concerning the use of water, that is, what constitutes a reasonable beneficial use, which then should be incorporated into the weights.

After these preliminary definitions, 3ME “ (Macro, Meso, and Micro-Efficiencies) result:?are described for a WRS based on two total flow types for water balance that incorporates different scales, flow paths, and Usefulness Criterion. MacroE links the system to the main water body of a river basin such as a river, while MicroE is of prime importance to the subsystems, such as an urban or agricultural area. The MesoE represents an analysis of the situations that are happening between MacroE and MicroE and the flows that occur between the two. Consequently, these three levels are of interest to different stakeholders within a river basin.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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Satellite precipitation adjustment

Tuesday, March 6th, 2012

April 2012 article (Early View): “Validation of Satellite Precipitation Adjustment Methodology From Seven Basins in the Continental United States,” by Kenneth J. Tobin and Marvin E. Bennett.

This article outlines a methodology that adjusts satellite products utilizing ground-based precipitation data. The approach is not a simple bias adjustment, but is a three-step process that transforms a satellite product based on a ground-based precipitation product (NEXRAD-derived Multisensor Precipitation Estimator [MPE] product or rain-gauge data). The developed methodology was successfully applied to seven moderate-to-large sized watersheds from continental United States and northern Mexico over a spectrum of climatic regimes ranging from dry to humid settings.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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Vanishing hemlock forests

Tuesday, March 6th, 2012

April 2012 article (Early View): “Effects of Eastern Hemlock Decline on Large Wood Loads in Streams of the Appalachian Mountains,” by Daniel M. Evans, C. Andrew Dolloff, W. Michael Aust, Amy M. Villamagna.

Large wood plot locations.

As a one of my favorite hiking trails winds through Upper Whiteoak Canyon in Shenandoah National Park, there’s a place called “Limberlost.” Over the years, I’ve seen this magical area change from a deep, dark, almost monoculture Eastern hemlock forest into a light place, filled with growing understory. The culprit is a hemlock woolly adelgid infestation. I knew this outbreak, occurring all over the Appalachian Mountains, had to effect streams. Here’s the answer.

The authors paired information on Eastern Hermlock decline with large wood (LW) measurements to examine the relationships between forest disturbance, basal area, and LW stream loads and to understand how this episodic disturbance affects stream ecosystems throughout the Appalachian Mountains. This study suggests that hemlock loss increase LW loads in streams in the short term, particularly in higher elevation, high-gradient streams. However, this initial pulse of LW may lead to decline of total LW in these high-gradient streams once the hemlock LW is flushed downstream or lost through fragmentation. This flush of new LW may flow downstream over time and add to LW loads in lower stream reaches. New stands of replacement trees will need time to develop after the hemlock are removed, before they contribute to production and recruitment of LW in streams.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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75 years of the U.S. flood control program

Friday, March 2nd, 2012

April 2012 article (Early View): “The U.S. Flood Control Program at 75: Environmental Issues,” by Peter E. Black.

Peter Black, a Past President of AWRA, is one of our organization’s treasures. Peter doesn’t have to read about historic water events, he was there! In this article, he examines the U.S. riverine Flood Control Program, starting by pointing out a notable misquote of Gilbert White. He shows how misconceptions and lack of understanding concerning fundamental ecology and hydrology of floodplains and watersheds have led to unwise or unintended consequences.

Including topics such as “How Realistic is Flood Control,” this summary makes for very interesting, sometimes opinionated reading. Black is senior enough to not hold back: “The time has come to recognize that there is pressing need to reconsider the value of ‘flood control’ as a misnomer, oxymoron, or fantasy: actually, all three.”

Only in JAWRA. Recommended reading.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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2007-9 Drought in Georgia

Thursday, March 1st, 2012

April 2012 article (Early View): “The 2007-2009 Drought in Athens, Georgia, United States: A Climatological Analysis and an Assessment of Future Water Availability,” by Pete Campana, John Knox, Andrew Grundstein, and John Dowd.

This case study reports how population increases, combined with a lack of water conservation, led to severe water shortages in the Athens, Georgia region during late 2007. Drought indices and precipitation records indicates that conditions were severe, but not worse than several other drought events. A drought of similar length would be expected to occur approximately every 25 years. Only after per capita usage decreased did water resources last despite continuing drought conditions through 2009.

In all likelihood, the future of water supplies will depend on mitigative and adaptive strategies implemented by the counties that rely on them. Mitigation strategies, such as the water restrictions put in place during 2007, have already proven to be successful at reducing withdrawal levels to a sustainable daily amount. The Athens area was able to avert a crisis partly by taking actions that were in advance of state restrictions on water use. However, Georgia HB 1281 (signed by Gov. Perdue in May 2008) now prevents local governments from getting “ahead of the curve” v. state-level water-use restrictions without application to and approval by the Director of the Georgia EPD on a case-by-case basis, demonstrating “good cause,” and following an EPD-approved process. This is a potentially disastrous top-down directive that reduces the responsiveness of society to drought.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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February 2012 cover photo

Wednesday, February 8th, 2012

Potomac River above Great Falls

Members, your February 2012 issue of JAWRA should be in your Official USPS mailboxes this week.

The February cover actually is more of a fall than winter scene. How appropriate for a “year without winter” in the Washington, D.C. area! It was taken early on a November morning, when the warm water of the river meeting the chilly air produced a fog. The location is on the Virginia side of the Potomac River, just upstream of Great Falls.

Instituted by former Editor Chris Lant, our cover photo has given JAWRA its distinctive look since 1997. We used stock photos until 2006, when we switched to member-contributed photos. You can see the past covers online. Instructions for contributing a photo also are on that page.

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GIS for variable source area

Tuesday, January 17th, 2012

February 2012 Article (Early View): “Incorporating Variable Source Area Hydrology into a Spatially Distributed Direct Runoff Model,” by Brian Buchanan, Zachary M. Easton, Rebecca Schneider, and M. Todd Walter.

Representative maps

This paper describes a geographic information system-based operational model that simulates the spatio-temporal dynamics of variable source area (VSA) runoff generation and distributed runoff-routing, including through complex artificial drainage networks. The model combines the Natural Resource Conservation Service’s Curve Number (CN) equation for estimating storm runoff with the topographic index concept for predicting the locations of VSA and a runoff-routing algorithm into a new spatially distributed direct hydrograph model.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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SWAT in Canada

Thursday, January 12th, 2012

February 2012 Article (Early View): “Modeling Climate Change Impacts on Hydrology and Nutrient Loading in the Upper Assiniboine Catchment,” Rajesh R. Shrestha, Yonas B. Dibike, and Terry D. Prowse.

Lake Winnipeg Watershed

The authors employed the SWAT model for future (2042-2062) periods with model forcings for future climates derived from three regional climate models and their ensemble means. The effects of future changes in climatic variables, especially precipitation and temperature, are clearly evident in the resulting snowmelt and runoff regimes. The future hydrologic scenarios consistently show earlier onsets of spring snowmelt and discharge peaks, and higher total runoff volumes. The simulated nutrient loads closely match the dynamics of the future runoff for both nitrogen and phosphorus, in terms of earlier timing of peak loads and higher total loads. However, nutrient concentrations could decrease due to the higher rate of runoff increase.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own.]

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