The mining of oil sands in northern Alberta leaves behind large open pits, tailings, and overburden piles in which the surface and subsurface hydrology has been completely disrupted. Extensive reclamation work is required to reconstruct the entire landscape and reestablish the various elements of the hydrologic cycle. Syncrude Canada Ltd. has established a series of small instrumented watersheds in a reclaimed overburden pile at the Mildred Lake mine in northern Alberta, Canada, to test the sustainability of different reclamation strategies. The purpose of these field sites is to assess the performance of different reclamation strategies and track the evolution of the reclaimed landscape with time. The saline-sodic shale overburden has been covered with different (in type and depth) soil layers to provide sufficient moisture storage for vegetation while minimizing runoff and salt transport into the cover from the underlying overburden shale. In this paper, a system dynamics watershed model (SDWM) is developed to simulate one of the reconstructed watersheds and assess its ability to provide common watershed functions. The model is at an early stage, but preliminary results point to the potential of the system dynamics approach in simulating watersheds and testing different scenarios. The tested reclamation strategy seems to be satisfactory within a certain range of hydrologic conditions. Further validation of the SDWM is required, however, before relying on its results for decision support with regard to reclamation strategies.Résumé : L'exploitation des sables bitumineux au nord de l'Alberta laisse sur place de grandes fosses à ciel ouvert, des résidus et des piles de morts-terrains; l'hydrologie souterraine et de surface a été complètement perturbée. Un travail de remise en état complet est requis pour reconstruire le paysage en entier et rétablir les divers éléments du cycle hydrologique. Syncrude Canada Ltd. a établi une série de petits bassins hydrologiques instrumentés dans un amoncellement de morts-terrains remis en état à la mine Mildred Lake, au nord de l'Alberta, afin d'étudier la durabilité de diverses stratégies de remise en état. Le but de ces sites sur le terrain est d'évaluer le rendement de diverses stratégies de remise en état et de suivre l'évolution temporelle du paysage remis en état. Les morts-terrains de shales salins et sodiques ont été recouverts de différentes (type et profondeur) couches de sol afin de conserver assez d'humidité pour la végétation tout en minimisant l'écoulement et le transport de sels dans la couverture à partir du mort-terrain de shale sous-jacent. Cet article développe un modèle de la dynamique du système du bassin hydrologique afin de simuler l'un des bassins hydrologiques reconstruits et évaluer sa capacité à fournir les fonctions de base d'un bassin hydrologique. Le modèle en est cependant à ses premières étapes, toutefois les résultats préliminaires soulignent le potentiel de l'approche de dynamique de système pour simuler les bassins hydrologiques et vérifier dive...

Many in-stream structures result in obstruction to fish migrations, thus preventing access to spawning grounds and other habitat areas which provide life cycle requirements for reproduction, rearing and shelter. Frequently, fishways are constructed at the site of the obstruction to provide access to habitat for various species. Conventional approaches to fish passage generally consist of 'hard' structures (e.g., concrete) or physical transport systems. Through experience and research in the laboratory and the field, much has been learned about the design requirements of these fishways. Recent attention has shifted to the use of 'soft' materials (e.g., rock), to try lor a more ecologicalffriendly fish passage method. The associated structures are referred to as nature-like fishways since they attempt to mimick nature. Considerable research in nature-like fishways is needed to ensure their successful application and widespread adoption.In this paper we give an overview ofconventional and nature-like fish Passage technology for river water projects. Included in the paper are discussions on basic fish passage requirements, conventional fishways, nature-like fishways, and guidance in selecting a fishway type. Comments are also provided on the need for further research in volitional fish passage technology. RESUMEBeaucoup de structures incorpor6es ont comme cons6quence lbbstruction pour p6cher des transferts, de ce fait emp6chant I'accds i engendrer les raisons et d'autres zones d'habitat qui fournissent des conditions requises de cycle de vie pour la reproduction, 1'6levage et I'abri. Fr6quemment, des passages de poissons sont construits au site de l'obstruction pour permettre d'acc6der i I'habitat pour diff6rentes espdces. Les approches conventionnelles pour p€cher le passage se

Reconstruction of disturbed watersheds is a common practice by the oil sands industry in northern Alberta, Canada. The reconstruction and restoration of the watershed hydrology are required as part of the reclamation mandated by Alberta Environment for mine closure. Assessment of the hydrological performance of the reconstructed watersheds is essential to ensure a sustainable reclamation strategy. A conceptual lumped system dynamics watershed (SDW) model is developed and calibrated in this study. The model, built within an object-based simulation environment, is capable of simulating the various hydrological processes in the reconstructed watersheds with good accuracy. STELLA Software is used as an object-based simulation environment that allows visual computations. The SDW model developed combines both physically-based and empirical formulations to replicate the hydrological system mathematically. The system dynamics approach along with the visual simulation environment help in developing a simulation-for-learning model, not only simulation for prediction. The model is successfully calibrated and validated; the results show that the SDW model is capable of simulating the various hydrological processes (soil moisture, evapotranspiration and runoff) with good accuracy. The SDW model can help in the assessment of the short-and long-term performances of the reconstructed watersheds, thus providing a useful decision-aid tool for the mining industry.Key words watershed modelling; system dynamics; reconstructed watersheds Simulation des processus hydrologiques de bassins versants reconstruits à l'aide de la dynamique des systèmes Résumé Dans le Nord de l'Alberta au Canada, une des pratiques communes de l'industrie des sables bitumineux est de reconstruire les bassins versants perturbés. La régénération prescrite par Alberta Environment, lors de la fermeture des mines, exige une reconstruction ainsi qu'une remise en état complète de l'hydrologie des bassins versants. Il est essentiel d'évaluer la performance hydrologique des bassins versants reconstruits afin d'assurer la pérennité d'une stratégie de régénération. Dans cette étude, on développe et étalonne un modèle localisé et conceptuel de la dynamique du système du bassin versant (DSBV). Le modèle, construit au sein d'un environnement de simulation orienté objet, peut simuler avec une bonne précision les divers processus hydrologiques des bassins versants reconstruits. Le logiciel STELLA est utilisé comme environnement de simulation orienté objet qui permet des calculs visuels. Le modèle développé DSBV combine des formulations empiriques et à bases physiques afin de reproduire mathématiquement le système hydrologique. L'approche de la dynamique des systèmes associée à l'environnement de simulation visuelle aident au développement d'un modèle non seulement de simulation pour la prévision, mais aussi de simulation pour l'apprentissage. Le modèle DSBV est calé et validé avec succès; les résultats montrent qu'il est capable de simuler les différents processus h...

Spillways for medium and high head dams may be exposed to high velocity flows and the associated destructive phenomenon of cavitation. Cavitation may occur at rough spots in the surface of the chute or tunnel, at local discontinuities in the finished surface such as construction joints, and at locations along critical flow profiles having significant deviations from design specifications. This paper addresses, on the basis of a review of the literature, a method for preventing or reducing cavitation damage on spillways through the use of spillway aerators. While the ability of induced or forced aeration to reduce or eliminate cavitation has been known for many years, it is only in relatively recent times that the aeration mechanism has been used to this advantage on spillways subject to high velocity flow. The recent application of aerators to spillway design is related, in part, to the trend toward higher head dams and larger design unit discharge rates. Design considerations and criteria for spillway aerators are presented in the paper, and the use of physical hydraulic models to make determinations of aerator performance is discussed. The intent of the paper is to provide a document with sufficient detail and scope to be useful as a first resource for spillway design practitioners. Key words: aerator design, air entrainment, cavitation, design criteria, high dam, model – prototype comparison, physical hydraulic model, spillway, spillway aeration.

The two-dimensional local scour occurring downstream from a submerged sluice gate for various tailwater depths was studied using a video imaging technique and a laser-Doppler anemometer. The flow field was found to be dynamic (i.e., varied with time). Previously reported equilibrium scour profiles for similar test conditions were not attained even after 96 h of laboratory testing. The scaling laws suggested in the literature were found to be unsuitable. New scaling laws are presented for the condition when a stable equilibrium state has not yet been attained. Velocity profiles are presented at various stations during digging and refilling conditions. Key words: local scour, time scale, video imaging, scour profile, velocity profile, sluice gate, cohesionless material, tailwater effect.