Effects of Mean Flow and Temperature on Acoustic Liner Performance in Dual Stream Flow Ducts

Recently, increasing concern in Africa has been registered on the potential impacts on base flow and stream flow due to the implementation of watershed management interventions. This research incorporates spatially monthly geographical hydrological data sets into a developed spreadsheet water balance model to estimate the changes in surface runoff, base flow and stream flow as a result of implementing watershed management interventions in the Abbay River Basin during the period (2010-2018). The model was implemented at sub-catchment level. Considering Year 2005 as a datum for watershed management intervention, results of the modeling and spatial analysis indicated that watershed management interventions relatively reduced surface runoff, increased deep infiltration to groundwater and accordingly increased base flow to the stream. Among the key results in the Abbay Basin that change from Year 2010 to Year 2018 was reduction of surface runoff from the Abbay Basin in the amount of 1,753 million m3/yr. As a result, an increase in annual base flow in the amount of 23 million m3/yr was estimated, leaving a reduction in annual mean flow of the Abbay River in the amount of 1,731 million m3/yr of the Abbay River at El-Diem site. It is expected that the flow of the Abbay River will continue to decrease due to the continuous implementation of the watershed management interventions and agriculture expansion in the Abbay Basin.

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Stream Flow Generation for Simulating Yearly Bed Change at an Ungauged Stream in Monsoon Region

Water ◽

10.3390/w13040554 ◽

2021 ◽

Vol 13 (4) ◽

pp. 554

Author(s):

Woong Hee Lee ◽

Heung Sik Choi ◽

Dongwoo Lee ◽

Byungwoong Choi

Keyword(s):

Stream Flow ◽

Mean Bias Error ◽

Percentage Error ◽

Bias Error ◽

Monsoon Region ◽

Mean Flow ◽

Bankfull Discharge ◽

River Bed ◽

Flow Generation ◽

Annual Discharge

The stream flow generation method is necessary for predicting yearly bed change at an ungauged stream in Monsoon region where there is no hydrologic and hydraulic information. This study developed the stream flow generation method of daily mean flow for each month over a year for bed change simulation at an ungauged stream. The hydraulic geometries of cross-sections and the corresponding bankfull indicators of the Byeongseong river of 4 km reach were analyzed to estimate the bankfull discharge. The estimated bankfull discharge of the target reach was 77.50 m3/s, and the total annual discharge estimated 3720 m3/s through the correlation equation with the bankfull discharge. The measured total annual discharge of the Byeongseong river was 3887.30 m3/s, which is greater by 167.30 m3/s of 4.3% relative error. The volume and bed changes over a year by the Center for Computational Hydroscience and Engineering Two-Dimension (CCHE2D) model simulated using the measured discharge during 2013 and 2014 coincided with the surveyed in the same period. Estimated total annual discharge was used for the scenarios of stream flow generation. The generated stream flow using the flow apportioned to each month on the basis of the flow percentage in an adjacent stream simulated the river bed most appropriately. The generated stream flow using the flow based on the monthly rainfall percentage of the rainfall station in the target stream basin also simulated river bed well, which is confirmed as an alternative. Quantitatively, the root mean square error (RMSE), mean bias error (MBE), and mean absolute percentage error (MAPE) in-depth change of thalweg between the measured and the simulated were found to be 0.25 m, 0.04 m, and 0.44%, respectively. The result of the simulated cross-sectional river bed change for target reach coincided well with the surveyed. The proposed method is highly applicable to generate the stream flow for analyzing the yearly bed change at an ungauged stream in Monsoon region.

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Tidal bending of ice shelves as a mechanism for large-scale temporal variations in ice flow

The Cryosphere ◽

10.5194/tc-12-1699-2018 ◽

2018 ◽

Vol 12 (5) ◽

pp. 1699-1713 ◽

Cited By ~ 9

Author(s):

Sebastian H. R. Rosier ◽

G. Hilmar Gudmundsson

Keyword(s):

Stream Flow ◽

Large Scale ◽

Temporal Variations ◽

Mean Flow ◽

Ice Shelf ◽

Ice Flow ◽

Ice Shelves ◽

The Mean ◽

Viscoelastic Modelling ◽

Shelf Flow

Abstract. GPS measurements reveal strong modulation of horizontal ice shelf and ice stream flow at a variety of tidal frequencies, most notably a fortnightly (Msf) frequency not present in the vertical tides themselves. Current theories largely fail to explain the strength and prevalence of this signal over floating ice shelves. We show how well-known non-linear aspects of ice rheology can give rise to widespread, long-periodic tidal modulation in ice shelf flow, generated within ice shelves themselves through tidal flexure acting at diurnal and semidiurnal frequencies. Using full-Stokes viscoelastic modelling, we show that inclusion of tidal bending within the model accounts for much of the observed tidal modulation of ice shelf flow. Furthermore, our model shows that, in the absence of vertical tidal forcing, the mean flow of the ice shelf is reduced by almost 30 % for the geometry that we consider.

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