Optimal sampling locations to reduce uncertainty in contamination extent in water distribution systems.

Drinking water utilities rely on samples collected from the distribution system to provide assurance of water quality. If a water contamination incident is suspected, samples can be used to determine the source and extent of contamination. By determining the extent of contamination, the percentage of the population exposed to contamination, or areas of the system unaffected can be identified. Using water distribution system models for this purpose poses a challenge because significant uncertainty exists in the contamination scenarios (e.g., injection location, amount, duration, customer demands, contaminant characteristics). This article outlines an optimization framework to identify strategic sampling locations in water distribution systems. The framework seeks to identify the best sampling locations to quickly determine the extent of the contamination while considering uncertainty with respect to the contamination scenarios. The optimization formulations presented here solve for multiple optimal sampling locations simultaneously and efficiently, even for large systems with a large uncertainty space. These features are demonstrated in two case studies.

Temperature-pressure scaling for air-fluidized grains near jamming.

We present experiments on a monolayer of air-fluidized beads in which a jamming transition is approached by increasing pressure, increasing packing fraction, and decreasing kinetic energy. This is accomplished, along with a noninvasive measurement of pressure, by tilting the system and examining behavior versus depth. We construct an equation of state and analyze relaxation time versus effective temperature. By making time and effective temperature dimensionless using factors of pressure, bead size, and bead mass, we obtain a good collapse of the data but to a functional form that differs from that of thermal hard-sphere systems. The relaxation time appears to diverge only as the effective temperature to pressure ratio goes to zero.

Variation in large-bodied fish-community structure and abundance in relation to water-management regime in a large regulated river.

Variation in life-history traits (growth, condition, mortality and recruitment) and relative abundance of 11 large-bodied fish species was investigated among three water-management regimes (unimpounded, run-of-the-river and winter reservoirs) in the large regulated Ottawa River, Canada. If waterpower management had an effect on fishes, then (1) would be expected community structuring among water-management regimes and (2) species with similar life-history traits should be affected in a similar manner. Large-bodied fish communities were assessed using two different standard index-netting techniques, one using trap nets and the other gillnets. Community structure could be discriminated based on species caught in nets using holographic neural networks (78.8% correct overall classification rate using trap nets and 76.0% using gillnets); therefore, water-management regimes affected community structure in the Ottawa River. Littoral zone benthivores were significantly lower in abundance (P < 0.001) or absent in winter reservoirs, whereas the abundance of planktivores or species that were planktivorous at young ages were significantly greater than in unimpounded river reaches. Growth, condition and mortality did not vary among reach types except smallmouth bass Micropterus dolomieu were in better condition in winter reservoirs than unimpounded reaches. Lake sturgeon Acipenser fulvescens recruitment was impaired in run-of-the-river reaches, whereas recruitment for other species that spawn in fast water was not affected.