Abstract. For estimating suspended sediment concentration (SSC) in rivers, turbidity is generally a much better predictor than water discharge. Although it is now possible to collect continuous turbidity data even at remote sites, sediment sampling and load estimation are still conventionally based on discharge. With frequent calibration the relation of turbidity to SSC could be used to estimate suspended loads more efficiently. In the proposed system a programmable data logger signals a pumping sampler to collect SSC specimens at specific turbidity thresholds. Sampling of dense field records of SSC and turbidity is simulated to investigate the feasibility and efficiency of turbidity-controlled sampling for estimating sediment loads during runoff events. Measurements of SSC and turbidity were collected at 10-min intervals from five storm events in a small mountainous watershed that exports predominantly fine sediment. In the simulations, samples containing a mean of 4 to 11 specimens, depending on storm magnitude, were selected from each storm's record, and event loads were estimated by predicting SSC from regressions on turbidity. Using simple linear regression, the five loads were estimated with root mean square errors between 1.9 and 7.7%, compared to errors of 8.8 to 23.2% for sediment rating curve estimates based on the same samples. An estimator for the variance of the load estimate is imprecise for small sample sizes and sensitive to violations in regression model assumptions. The sampling method has potential for estimating the load of any water quality constituent that has a better correlate, measurable in situ, than discharge.
Lisle, T. E., and J. Lewis. 1992. Effects of sediment transport on survival of salmonid embryos in a natural stream: a simulation approach. Can. J. Fish. Aquat. Sci. 49: 2337Sci. 49: -2344.A model is presented that simulates the effects of streamflow and sediment transport on survival of salmonid embryos incubating in spawning gravels in a natural channel. Components of the model include a 6-yr streamflow record, an empirical bed load-transport function, a relation between transport and infiltration of sandy bedload into a gravel bed, effects of fine-sediment infiltration on gravel properties, and functions relating embryo survival to gravel properties. High-flow events drive temporal variations in survival; cross-channel variations in bedload transport cause spatial variations. Expected survival, as a result, varies widely from year to year and between spawning runs in a single year. Alternative functions from previous research that relate survival to fine-sediment concentration in spawning gravel and to intergravel rates of flow yield categorically different results. The relative uncertainty of the components of this model indicates that the greatest research needs are to understand how sediment transport affects the intergravel environment and how these changes affect embryo development and survival.Nous présentons un modèle qui simule les effets de l´écoulement d'un cours d'eau et du transport des sédiments sur la survie des embryons de salmonidés en incubation clans des frayères de gravier dans un chenal naturel. Les composantes du modèle incluent un relevé du débit du cours d'eau pendant 6 ans, une fonction empirique de transport des sédiments de fond, une relation entre le transport et l´infiltration de la charge de fond sableuse dans une couche de gravier, les effets de l´infiltration de sédiments fins sur les propriétés du gravier et des functions mettant en relation la survie des embryons et les propriétés du gravier. Les épisodes de débit élevé entraînent des variations temporelles de la survie; les variations D'travers le chenal du transport des sédiments de fond causent des variations spatiales. Par conséquent, la survie prévue varie considérablement d'une année a l´autre et d'une montaison de fraye à l'autre au cours de la même année. D'autres fonctions établies lors d´études précédentes qui mettent en relation la survie et la concentration de sédiments fins clans le gravier de la frayère ou l´écoulement entre les graviers donnent des résultats totalement différents. L´incertitude relative des composantes de ce modèle indique clue le besoin le plus pressant sur le plan de la recherche est la compréhension de la manière dont le transport des sédiments influe sur l´environnement du gravier et des répercussions de ces changements sur le développement et la survie des embryons. Received January 2, 1992 Reçu le 2 janvier 1992 Accepted May 21, 1992Accepté le 21 mai 1992 (JB354) urvival of salmonid embryos to emergence from the streambed has been related to substrate and flow conditions in many experimen...
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