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[1] Despite the growing interest in hyporheic exchange and the associated stream ecosystem processes, few studies consider restoration of hyporheic exchange as a design goal. Here we study the design of three types of subsurface structures for hyporheic restoration after conceptual designs published over 40 years ago. Vaux's designs involve modifying the subsurface with low or high hydraulic conductivity material placed at the streambed or adjacent to a confining layer below the stream. In this preliminary analysis of subsurface structure design we use two-dimensional groundwater flow modeling of structures to simulate structure performance in plane bed streams for ranges of structure geometric design and hydraulic conductivities. Structure performance is evaluated on the basis of total streambed flux, physical extent of hyporheic flow paths created, and residence time distributions along flow paths modified by the structures. High hydraulic conductivity structures bend flow paths toward and through the structures themselves; performance is controlled by the structure hydraulic conductivity. Results show low hydraulic conductivity structure performance is insensitive to the structure material; hyporheic exchange is created by deflecting flow paths away from the structure itself. Time scales of simulated exchange are great enough to promote nitrification, denitrification, respiration, and thermal buffering in the subsurface, though these processes will also be controlled by site-specific chemical and biological factors. General design recommendations for specific restoration objectives are presented. Results of this study can be extrapolated to further understand the interaction of natural subsurface heterogeneities (e.g., clay and gravel deposits and bedrock knickpoints) and flow fields in creating hyporheic flow paths.Citation: Ward, A. S., M. N. Gooseff, and P. A. Johnson (2011), How can subsurface modifications to hydraulic conductivity be designed as stream restoration structures? Analysis of Vaux's conceptual models to enhance hyporheic exchange, Water Resour. Res., 47, W08512,

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An artificial neural network (ANN) was used to evaluate the hydrological responses of two streams in the northeastern U.S. having different hydroclimatologies (rainfall and snow+rain) to hypothetical changes in precipitation and thermal regimes associated with climate change. For each stream, historic precipitation and temperature data were used as input to an ANN, which generated a synthetic daily hydrograph with high goodness-of-fit (r2 > 0.80). Four scenarios of climate change were used to evaluate stream responses to climate change: + 25% precipitation, -25% precipitation, 2 x the coefficient of variation in precipitation regime, and +3"C average temperature. Responses were expressed in hydrological terms of ecological relevance, including flow variability, baseflow conditions, and frequency and predictability of floods. Increased average precipitation induced elevated runoff and more frequent high flow events, while decreased precipitation had the opposite effect. Elevated temperature reduced average runoff. Doubled precipitation variability had a large effect on many variables, including average runoff, variability of flow, flooding frequency, and baseflow stability. In general, the rainfall-dominated stream exhibited greater relative response to climate change scenarios than did the snowmelt stream.Stream ecosystems are at risk for changes due to climate change because ecological processes are strongly influenced by seasonal patterns of precipitation, runoff, and temperature (Carpenter et al. 1992;Allan 1995). If historical hydrological and thermal regimes in streams are modified by anthropogenically altered climate change, then ecosystem alteration is to be expected. Hydrological modifications may result either from changes in average conditions or from changes in the distribution and timing of extreme events such as floods and droughts. Evaluating the extent to which stream hydrographs are modified by scenarios of climate change can provide important information on the relative sensitivity of stream ecosystems to potential climate change.Modeling stream hydrological response to climate variation can be performed with a variety of techniques. If detailed watershed and climate data are available for parameterization, one can use mass balance models, such as hydrological budget models (e.g. Gleick 1987). However, for many stream systems, detailed watershed data are lacking, making the mechanistic modeling of hydrological response to climate difficult, Further, traditional empirical models (e.g. regression models) may not per- AcknowledgmentsWe thank P. Mulholland and C. P. Hawkins for constructive reviews of an earlier version of this paper.

The Walkerton (Ontario, Canada) outbreak of waterborne Escherichia coli O157:H7 and Campylobacter jejuni was quite limited in both space and time, making it a good model for exploring the utility of different typing and subtyping methods for the characterization of relationships among isolates of these organisms. We have extended previous work with these organisms through analysis by the Oxford multilocus sequence typing (MLST) and the flagellin short variable region (fla-SVR) sequencing methods. Additional isolates not epidemiologically related to the Walkerton outbreak have also been included. Both sequencing methods identified and differentiated between Walkerton outbreak strains 1 and 2. When these strains were compared with isolates that were not part of the outbreak, the information produced by the fla-SVR method more often correlated with epidemiological findings than that produced by MLST, though both methods were required for optimal discrimination. The MLST data were more relevant in terms of the overall population structure of the organisms. Both mutation and recombination appeared to be responsible for generating diversity among the isolates tested.

Bankfull depth and discharge are basic input parameters to stream planform, stream restoration, and highway crossing designs, as well as to the development of hydraulic geometry relationships and the classification of streams. Unfortunately, there are a wide variety of definitions for bankfull that provide a range of values, and the actual selection of bankfull is subjective. In this paper, the relative uncertainty in determining the bankfull depth and discharge is quantified, first by examining the variability in the estimates of bankfull and second by using fuzzy numbers to describe bankfull depth. Fuzzy numbers are used to incorporate uncertainty due to vagueness in the definition of bankfull and subjectivity in the selection of bankfull. Examples are provided that demonstrate the use of a fuzzy bankfull depth in sediment trans. port and in stream classification. Using fuzzy numbers to describe bankfull depth rather than a deterministic value allows the engineer to base designs and decisions on a range of possible values and associated degrees of belief that the bankfull depths take on each value in that range.

This work investigated effects of carrying 0, 1, or 2 copies of the A allele resulting from the g+6723G-A transition in growth differentiation factor gene (GDF8) in New Zealand Texel-cross sheep at different lamb ages and carcass weights. Two Texel-cross sires carrying 1 copy of the A allele were mated to approximately 200 ewes carrying 0, 1, or 2 copies of the A allele. A total of 187 progeny were generated and genotyped to determine whether they were carrying 0, 1, or 2 copies of the A allele. The progeny were assigned to 1 of 4 slaughter groups balanced for the 3 genotypes, sex, and sire. The 4 groups were slaughtered commercially when their average BW (across all progeny in the slaughter group) reached 33, 40, 43, and 48 kg, respectively. Measurements of BW, and carcass dimensions and yield were made on all animals using Viascan (a commercial 2-dimensional imaging system that estimates lean content of the carcass as a percentage of total carcass weight). Additional measurements were made on the fourth slaughter group, which was computed tomography scanned at each slaughter time point to obtain 4 serial measures of lean and fat as estimated from the computed tomography images. The A allele did not have an effect on any BW traits. The A allele was associated with increased muscle and decreased fat across the variety of measures of muscling and fat, explaining between 0.2 and 1.1 of a residual SD unit. Estimates for an additive effect were significant and were positive for muscle and negative for fat traits. No dominance effect estimates (positive or negative) were significant. There was no significant interaction between A allele number and carcass weight or slaughter group for any trait. This is the first systematic study of the effect of the A allele copy number over a range of carcass weights (13 to 20 kg) and ages and results suggest the size of the effect across these endpoints is proportionately the same. Testing for the A allele therefore offers breeders the potential to improve rates of genetic gain for lean-meat yield across most production systems.