Archive for the ‘Article Highlights’ Category

Estrogen transport from poultry litter

Wednesday, May 16th, 2012

June 2012 article (Early View): “Dissolved Organic Carbon and Estrogen Transport in Surface Runoff From Agricultural Land Receiving Poultry Litter,” by Sudarshan Dutta, Shreeram Inamdar, Jerry Tso, Diana S. Aga, and J. Tom Sims.

Poultry litter from concentrated bird-raising operations has become a major issue. This article adds some critical experimental data to the discussion, looking at estrogens and dissolved organic carbon (DOC).

The authors investigated exports of DOC in surface runoff from agricultural fields receiving various treatments of poultry litter (raw vs. pelletized). In addition, they also investigated how estrogens in runoff were associated with DOC. Different forms of estrogens studied were: estrone, 17?-estradiol, estriol, and their conjugates. Experimental agricultural plots were 12 m × 5 m long and had reduced tillage and no-till management practices. The aromatic content of DOC was characterized using specific ultraviolet absorbance (SUVA). Flow-weighted concentrations of DOC and SUVA in surface runoff from plots with poultry litter were significantly (p ? 0.10) greater than the control (no litter) plots. Compared to pelletized poultry litter, reduced-tillage plots with raw litter yielded higher DOC concentrations and SUVA values. No significant differences (p ? 0.10) in DOC and SUVA were observed between litter treatments for plots with no-till. Total estrogen concentrations (including all forms) were positively and significantly (p ? 0.10) correlated with DOC.

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

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Stream restoration mitigation

Tuesday, May 15th, 2012

June 2012 article (Early View): “Compensatory Mitigation for Streams Under the Clean Water Act: Reassessing Science and Redirecting Policy,” by Martin W. Doyle and F. Douglas Shields.

This article throws down a major challenge for stream restoration programs, basically saying the scale of restoration often is too small. I will let the abstract below speak for itself.

Current stream restoration science is not adequate to assume high rates of success in recovering ecosystem functional integrity. The physical scale of most stream restoration projects is insufficient because watershed land use controls ambient water quality and hydrology, and land use surrounding many restoration projects at the time of their construction, or in the future, do not provide sufficient conditions for functional integrity recovery. Reach scale channel restoration or modification has limited benefits within the broader landscape context. Physical habitat variables are often the basis for indicating success, but are now increasingly seen as poor surrogates for actual biological function; the assumption “if you build it they will come” lacks support of empirical studies. If stream restoration is to play a continued role in compensatory mitigation under the United States Clean Water Act, then significant policy changes are needed to adapt to the limitations of restoration science and the social environment under which most projects are constructed. When used for compensatory mitigation, stream restoration should be held to effectiveness standards for actual and measurable physical, chemical, or biological functional improvement. To achieve improved mitigation results, greater flexibility may be required for the location and funding of restoration projects, the size of projects, and the restoration process itself.

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

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Climatic data input for SWAT

Tuesday, May 15th, 2012

June 2012 article (Early View): “Improved SWAT Model Performance With Time-Dynamic Voronoi Tessellation of Climatic Input Data in Southern Africa,” by Jafet C.M. Andersson, Alexander J.B. Zehnder, Bernhard Wehrli, and Hong Yang.

Most of our common hydrologic models were developed in regions relatively rich in data. Applying them to regions with more problematic data is a major challenge. Here’s an interesting study working in Southern Africa.

This study compared two approaches to obtain climatic time series for the Soil and Water Assessment Tool (SWAT), namely the conventional centroid method and time-dynamic Voronoi tessellation, and assessed the performance of SWAT in simulating discharge and smallholder maize yields in Southern Africa. Climatic time series were estimated with each method. The Voronoi method utilized all available precipitation and temperature data, but the centroid method used only 14.5 and 82.5%, respectively.

After centroid processing, sub-basin time series were on average 42 and 63% incomplete, respectively. After Voronoi processing, all time series were complete. SWAT was fed with each climate dataset. Each model setup was independently calibrated and validated against discharge and maize yield. Similar model performance was obtained with both methods for yield. The root mean squared error during calibration was 0.26 and 0.27 t ha?1 for the centroid and Voronoi methods, respectively (p-value: 0.80). However, daily discharge simulations improved significantly with the Voronoi method. The coefficient of determination increased from 0.24 to 0.39 in the calibration period (p-value: 9.6 × 10?13) and from 0.41 to 0.48 in the validation period (p-value: 3.1 × 10?3). The Voronoi method improved the simulation of the river flow regime. The largest improvements were obtained in data scarce situations, at high spatial and temporal resolution, and where the centroid method performed the worst.

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

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Hydraulic geometry relations

Thursday, May 10th, 2012

June 2012 article (Early View): “Optimizing Bankfull Discharge and Hydraulic Geometry Relations for Streams in New York State,” by Christiane I. Mulvihill, and Barry P. Baldigo.

Regional hydraulic geometry (HG) curves are regression equations that estimate bankfull discharge, width, depth, and cross-sectional area as a function of drainage area. Bankfull discharge in alluvial streams with well-developed floodplains is the stage or flow at which a stream just overtops its banks, or the point of incipient flooding

This study analyzes how various data stratification schemes can be used to optimize the accuracy and utility of regional HG models of bankfull discharge, width, depth, and cross-sectional area for streams in New York. Topographic surveys and discharge records from 281 cross sections at 82 gaging stations with drainage areas of 0.52-396 square miles were used to create log-log regressions of region-based relations between bankfull HG metrics and drainage area. The success with which regional models (see the article for the regions) distinguished unique bankfull discharge and HG patterns was assessed by comparing each regional model to those for all other regions and a pooled statewide model. Gages were also stratified (grouped) by mean annual runoff (MAR), Rosgen stream type, and water-surface slope to test if these models were better predictors of HG to drainage area relations.

This study found that statewide relations between drainage area and HG were strongest when data were stratified by hydrologic region, but that co-variable models could yield more accurate HG estimates in some local regional curve applications.

NOTE: New York recently made regional curves more accessible by adding them to StreamStats (http://water.usgs.gov/osw/streamstats/new_york.html) application, the subject of many talks at the recent AWRA GIS Specialty Conference.

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

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Estimating with sparse data

Wednesday, May 9th, 2012

June 2012 article (Early View): “A Design Peak Flow Estimation Method for Medium-Large and Data-Scarce Watersheds With Frontal Rainfall,” by Enrique Muñoz, José Luis Arumí, and José Vargas

It’s always nice to have a lot of long-term data. But, what do you do when the data are sparse? Here’s a nice solution applied to Chile.

The authors developed a reliable peak flow estimation method for the design of hydraulic structures. The method is valid in medium-large watersheds (100-5,000 km2) located in Chile between 32°45? and 43°50?S, with scarcity of hydro-meteorological information, and where frontal rainfall prevails. The proposed method requires only rainfall data and geomorphologic descriptors as inputs, and relates the instant peak flow with the time of concentration rainfall flux (the contributing watershed area multiplied by the rainfall). The parameters of the model were defined with peak flows obtained from statistical analyses of historical fluviometric records from 25 watersheds. The quality of the proposed method is evaluated by applying it to three external watersheds different from those used to define model parameters, and comparing it with three other indirect methods and with peak flows obtained from statistical analyses, which were also used as the benchmark. The proposed method estimates peak flows with mean differences of less than 10%, which is two times less than other similar indirect methodologies, making it a recommendable option for estimating design peak flows.

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

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Nitrate concentrations in springs

Tuesday, May 8th, 2012

June 2012 article (Early View): “Nitrate Concentrations in Springs Flowing into the Lower Flint River Basin, Georgia U.S.A.,” by Stephanie E. Allums, Stephen P. Opsahl, Stephen W. Golladay, David W. Hicks, and L. Mike Conner.

Analysis of long-term data from (2001-2009) in four springs that discharge from the Upper Floridan aquifer into the Flint River (southwestern Georgia, United States) indicate aquifer and surface-water susceptibility to nutrient loading. These analyses indicate a direct relation between nitrate-N loading since the 1940s and intensification of agricultural and urban land use. This study demonstrates the importance of evaluating long-term impacts of land use on water quality in groundwater springs and in determining how rapidly these changes occur.

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

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Sampling variability

Friday, May 4th, 2012

June 2012 article (Early View): “Spatial Variability of Pool-Tail Fines in Mountain Gravel-Bed Stream Affects Grid-Count Results,” by Kristin Bunte, John P. Potyondy, Kurt W. Swingle, and Steven R. Abt.

The study demonstrated how bankward fining and longitudinal differences of pool-tail fines can affect amounts, variability, and accuracy of grid-count results obtained by different sampling schemes.

Fine sediment (<2 and <6 mm) particles underlying a 49-intersection grid placed on a streambed at 25, 50, and 75% of the wetted pool-tail width are commonly counted to assess the status and trend of aquatic ecosystems or to monitor changes in the supply of fines in mountain gravel-bed streams. However, results vary even when crews perform nearly identical procedures. This study hypothesized that spatial variability of pool-tail fines affects grid-count results and that a sampling scheme can be optimized for precision and accuracy. Grid counts taken at seven evenly spaced locations across the wetted width of 10 pool tails in a pool-riffle study stream indicated a bankward fining trend with secondary peaks of fines within the stream center. Sampling locations close to the waterlines harbored more than twice as many fines as central locations. Most of the five grid-count schemes derived from the seven sampled locations produced significantly different results. Compared with sampling at all seven locations, schemes that focus near waterlines overpredicted fines, while those that focus on the center underpredicted them. Variability of fines among pool tails was the highest within a broad band along the waterlines; hence, focusing sampling there yielded the most variable results. The scheme sampling at 25, 50, and 75% of the wetted width had the lowest precision and moderate accuracy. Accuracy and precision of grid-count results can be greatly improved by sampling at seven even-spaced locations across the pool tail.

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

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Urban stream restoration valuation

Wednesday, May 2nd, 2012

June 2012 article (Early View): “Is Urban Stream Restoration Worth It?,” by Melissa A. Kenney, Peter R. Wilcock, Benjamin F. Hobbs, Nicholas E. Flores, and Daniela C. Martínez.

Public investment in urban stream restoration is growing, yet little has been done to quantify whether its benefits outweigh its cost. The most common drivers of urban stream projects are water quality improvement and infrastructure protection, although recreational and aesthetic benefits are often important community goals. The authors use standard economic methods to show that these contributions of restoration can be quantified and compared to costs. The approach is demonstrated with a case study in Baltimore, Maryland, a city with a legal mandate to reduce its pollutant load. Typical urban stream restoration costs of US$500-1,200 per foot are larger than the cost of the least expensive alternatives for management of nitrogen loads from stormwater (here, detention ponds, equivalent to $30-120 per foot of restored stream) and for protecting infrastructure (rip-rap armoring of streambanks, at $0-120 per foot).

The key appears to be, the higher costs of stream restoration can in some cases be justified by its aesthetic and recreational benefits. Anecdotal evidence suggests that aesthetic and recreation enhancements such as instream riffles and falls, walking paths, stream access, debris removal, signage, and desirable streamside vegetation may have public appeal. These are valued using a contingent valuation survey at $560-1,100 per foot. The article does not intend to provide a definitive answer regarding the worth of stream restoration, but demonstrates that questions of worth can be asked and answered. Broader application of economic analysis would provide a defensible basis for understanding restoration benefits and for making restoration decisions.

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

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Optimizing hydropower

Tuesday, May 1st, 2012

June 2012 article (Early View): “Short-Term Hydroscheduling with Discrepant Objectives Using Multi-Step Progressive Optimality Algorithm,” by Chuntian Cheng, Jianjian Shen, Xinyu Wu, and Kwok-wing Chau.

Short-term hydroscheduling (STHS) has received more attention in China with the rapid expansion of hydropower systems. This article presents a novel strategy for STHS with discrepant objectives in which all hydropower plants are classified into several types. The classification depends on the location and special operating characteristics of hydroplants, inflow, installed capacity, load demands, and other factors. In this way, the same type of plants take advantage of the same optimization objective for optimizing their generation scheduling, and the objectives used for different types are different. Each type of hydropower plant is expected to play its best role using the objective function chosen.

In this article, the authors present a multi-step progressive optimality algorithm (MSPOA) for the short-term hydroscheduling (STHS) problem to improve the quality of optimal solutions and enhance the convergence speed of progressive optimality algorithm (POA). In MSPOA, the original problem is first decomposed into a sequence of problems with the longer time steps. Next, the problem with the longest time step is solved, and the optimal solution is used as the initial solution for the problem with the second longest time step. This process proceeds until the original problem with the shortest time step is solved. The proposed discrepant-objective method and solution technique are tested for two types of hydroelectric systems. The results show that MSPOA can give better solutions and cost less time than POA due to enlarging feasible range of decision variables and reducing the number of computational stages. Discrepant objectives among hydropower plants can express the operation characteristics of complex hydropower systems more accurately than unique objective or multiple objectives.

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

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ET corrections

Tuesday, March 13th, 2012

April 2012 article (Early View): “Error Autocorrelation and Linear Regression for Temperature-Based Evapotranspiration Estimates Improvement,” by Patrick Valverde Medeiros, Francisco Fernando Noronha Marcuzzo, Cristián Youlton, and Edson Wendland.

This work describes two correction procedures for potential evapotranspiration estimates by temperature, making the results more reliable. Initially, the standard FAO-Penman-Monteith method was evaluated with a complete climatologic data set for the period between 2002 and 2006. Then temperature-based estimates by Camargo and Jensen-Haise methods have been adjusted by error autocorrelation evaluated in biweekly and monthly periods. In a second adjustment, simple linear regression was applied. The adjusted equations have been validated with climatic data available for the Year 2001. Both proposed methodologies showed good agreement with the standard method indicating that the methodology can be used for local potential evapotranspiration estimates.

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

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