Turbine Discharges Research Articles

Downstream alterations on hydrodynamic fields by hydropower plant operations: implications for upstream fish migration

This study identifies hydrodynamic alterations in flow downstream of a dam that are related to hydropower plant (HPP) operation and that might attract Neotropical potamodromous fish to unsafe places in the tailrace during their reproductive migration. Our hypotheses are (1) the hydrodynamic flow in the tailrace presents conditions that are strong attractive for fish than those found in the downstream reach and (2) there are no velocity barriers preventing the upstream migrant from reaching the tailrace over a wide range of turbine discharge. Two calibrated numerical models were created for the Tres Marias HPP (Brazil), using different turbine discharges: (1) a three-dimensional (3D) model of flow in the tailrace and (2) a two-dimensional (2D) model for flow in the 3-km reach downstream of the dam. Resulting flow fields of the Tres Marias HPP tailrace have elevated hydraulic strain and velocity homogeneity by as compared to the flow field of the downstream reach. The tailrace velocities are slow for mature individuals of all study species, which may swim from downstream reach to unsafe areas in their sustainable and prolonged mode by available corridors for different turbined discharges.

It goes with the flow: Size mediated plankton attenuation through the Niagara River connecting channel

Abstract The Niagara River connecting channel provides a unique system in which to examine the impact of a rapid lentic-lotic-lentic transition on a freshwater ecosystem, particularly on plankton community composition. From June to October 2014, six monitoring sites (three in the upper river and three in the lower river) were sampled monthly for water chemistry, phytoplankton and/or zooplankton composition. Zooplankton biomass decreased exponentially with distance downstream, as expected within a high flow lotic environment. The rapid attenuation of zooplankton occurring within 10 km of the river mouth was likely due to predation by large populations of planktivorous fishes in the river. Densities of phytoplankton, rotifers and bacteria also declined but were less strongly impacted by the lentic-lotic transition. Plankton communities were dominated by species common to Lake Erie, the source waterbody, and also by taxa more resilient to the highly turbulent conditions of the river. These species included siliceous diatoms, filamentous algae, small zooplankters, dreissenid veligers and loricated rotifers. Furthermore, the seasonality of species composition in the Niagara River is the same as its source water body, suggesting no impact from the river on plankton succession. Niagara Falls and the two hydroelectric facilities were not found to be a significant cause of plankton mortality down river. There is some evidence however that entrainment time in the hydroelectric reservoirs may slightly enhance phytoplankton and zooplankton densities, thus contributing to plankton populations downstream of the turbine discharges.

STUDY ON RULE CURVE DEVELOPMENT FOR HYDRO ELECTRIC POWER (HEP) DAM OPERATION. CASE STUDY: MURUM HEP DAM

An operation rule curve of a dam provides specific on the target elevation of thereservoir. This can vary throughout the year. This is an indication to the reservoir operator ofactivities to conduct for various situations involving reservoir and the hydrologic conditions.This rule curve shall apply to Murum dam solely for power generation purpose. Thedecisions on when and how much to release will impact the ability to pass a flood as well ashydropower capacity. The main objective of this research is to select the most suitablemethod and to develop the operation rule curves for Murum dam primarily for hydropowergeneration. A trial-and-error method has been selected for this study. Reservoir operationmodeling and simulation have been commenced using historical rainfall data, after runoffwas generated by rainfall runoff modellings. Three (3) simulations are conducted fordeveloping the operation rule curves. They are rule curve according to Sarawak EnergyBerhad’s requirement, ideal rule curve and mean rule curve. All three sets of rule curves aresuccessfully developed using turbine discharges of the dam as the parameters and to achievethe target firm energy generation of 635MW.

A Study of the Location of the Entrance of a Fishway in a Regulated River with CFD and ADCP

Simulation-driven design with computational fluid dynamics has been used to evaluate the flow downstream of a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed, and the measurements were used to validate the simulations. The measurements indicate a more unstable flow than the simulations, and the tailrace jet from the turbines is stronger in the simulations. A fishway entrance was included in the simulations, and the subsequent attraction water was evaluated for two positions and two angles of the entrance at different turbine discharges. Results show that both positions are viable and that a position where the flow from the fishway does not have to compete with the flow from the power plant will generate superior attraction water. Simulations were also performed for further downstream where the flow from the turbines meets the old river bed which is the current fish passage for upstream migrating fish. A modification of the old river bed was made in the model as one scenario to generate better attraction water. This considerably increases the attraction water although it cannot compete with the flow from the tailrace tunnel.

Simulation of transient flow in pipeline systems due to load rejection and load acceptance by hydroelectric power plants

In this paper, the implicit method of characteristics (IMOC) is extended to simulate the transient flow caused by load variation of hydroelectric power plants. The IMOC was proposed recently by the authors to remove the limitations of the commonly used conventional method of characteristics (MOC) and subsequently used for the simulation of transient flow caused by valve closure and pump failure. In the IMOC, an element-wise definition is used for all devices that may be used in a pipeline system and the corresponding equations are then assembled to form a system of equations that is solved for the unknown nodal heads and flows at each time step. In this paper, the IMOC is extended for the simulation of transient flow in the pipeline system upstream of a hydroelectric power plant. For this, an element-wise definition of the hydroelectric power plants and simple surge tank is proposed and their governing equations are derived in a matrix form required by the IMOC. Then these equations are assembled along with those of other devices of the pipeline system to construct a system of equations that is solved for the unknown head and flow. To further improve the convergence characteristics of the method, an improved formulation of the turbine is also proposed. In the proposed formulation, one of the turbine characteristic parameters, namely turbine net head, is used in addition to turbine head and discharges, to formulate the behavior of the turbine element. The method is applied to a problem of transient flow caused by load rejection and acceptance and the results are presented and compared with those of the explicit MOC. The results show the ability of the proposed method to accurately predict the variations of head and flow in the cases considered. It is also shown that the improved formulation of the turbine is computationally more efficient than the original formulation while producing the same results.

Hindrances to upstream migration of atlantic salmon (Salmo salar) in a northern Swedish river caused by a hydroelectric power‐station

AbstractMany Baltic salmon rivers have lost their natural juvenile production due to human activities blocking or reducing access to their spawning grounds, e.g. damming, power generation, partial hinders, etc. One such hindrance is a hydroelectric complex located in the lower reaches of River Umeälven in northern Sweden. Water from the forbay created by the dam Norrfors is directed to the Stornorrfors power‐station. At times, 100% of the river water is directed to the power‐station. Water from the power‐station then flows via a tunnel and outlet channel to the river. From the point of the tunnel's discharge into the river, the old river bed acts as a bypass channel directing migrating adult fish to a fish ladder located at the base of the dam.In this study, the effect that an additional turbine, that was installed at the power‐station in 1986, had on fish passage run‐time was examined. Changes in run‐time were compared for two periods 1974–1985 and 1986–1995. In 1997, 55 wild and 25 hatchery salmon were captured in the Umeälven estuary, radio tagged with uniquely coded tags, and tracked upstream. Both manual and automatic loggers were used to locate fish daily. The main findings show that only 26% of the wild salmon and none of the hatchery salmon found the fish ladder. It is suggested that the salmon followed the main water discharge from the power‐station outlet and are thus directed away from the entrance to the bypass channel leading to the fish ladder. Salmon respond by moving upstream or downstream depending on the current flow regimes. The bypass channel consists of partial hinders that may explain why it takes on average 52 days for the salmon to migrate 32 km from the estuary to the fish ladder. Adding a fourth turbine at the power‐station did not appear to have changed the timing of the migration or the seasonal distribution of the migrating wild salmon through the fish ladder. There was no significant effect of the fourth turbine on the duration of the middle 50% of the run in any weight‐class for wild salmon. Daily turbine discharges or ambient water temperature and daily counts of wild salmon at the fish ladder were not related. Copyright © 2001 John Wiley & Sons, Ltd.

IT'S NOT EASY BEING GREEN: Environmental Technologies Enhance Conventional Hydropower's Role in Sustainable Development

▪ Abstract Conventional hydroelectric generation uses a renewable energy source and currently supplies ∼10% of the annual output of electricity in the United States and ∼20% of electricity generated worldwide. To provide a significant contribution to sustainable development, the hydropower industry must address a variety of environmental concerns, including water quality and fish passage issues. The paper discusses new technologies for turbine design and control systems to improve dissolved oxygen levels in turbine discharges and survival of fish during turbine passage. The paper describes development, testing, and test results for these technologies, with an emphasis on collaboration of stakeholders and balance between environmental stewardship and economical power production.

Water‐Quality Impact Assessment for Hydropower

A methodology to assess the impact of a hydropower facility on downstream water quality is described. Negative impacts can result from the substitution of discharges aerated over a spillway with minimally aerated turbine discharges that are often withdrawn from lower reservoir levels, where dissolved oxygen (DO) is typically low. Three case studies illustrate the proposed method and problems that can be encountered. Historic data are used to establish the probability of low‐dissolved‐oxygen occurrences. Synoptic surveys, combined with downstream monitoring, give an overall picture of the water‐quality dynamics in the river and the reservoir. Spillway aeration is determined through measurements and adjusted for temperature. Theoretical computations of selective withdrawal are sensitive to boundary conditions, such as the location of the outlet relative to the reservoir bottom, but withdrawal from the different layers is estimated from measured upstream and downstream temperatures and dissolved‐oxygen profi...

DO Model for Discharges from Deep Impoundments

A simple model is presented for the annual dissolved oxygen (DO) cycle of releases from the hypolimnion of deep impoundments. The model includes mathematical formulations and rate constants for the processes of BOD decay, atmospheric reaeration, and thermal stratification. It was used to characterize the DO cycle of releases from 17 Tennessee Valley Authority reservoirs, using three years of weekly DO and temperature data. Rate constants were estimated using the quasilinearizatin technique for estimating unknown parameters in a system of ordinary differential equations. The results indicate that the model can reasonably simulate annual DO variations of turbine discharges from hypolimnetic waters. Since the model is a simple formulation of complex reservoir processes, it is best suited for preliminary analyses.