wind and wave measurments in irrigation reservoirs

69th SWCS International Annual Conference, 27 - 30 July, 2014, Lombard, ILNational Center for ComputationalHydroscience and Engineering

The University ofMississippi

Wind and Wave Measurements in Irrigation Reservoirs

Yavuz OzerenNational Center for Computational Hydroscience and Engineering

The University of Mississippi, Oxford, MS

Daniel WrenUSDA‐ARS, National Sedimentation Laboratory, Oxford MS

Michele RebaUSDA‐ARS, Delta Water Management Research Unit, Jonesboro, AR



Introduction

• The earthen embankments of these reservoirs often experience significant erosion primarily due to wind‐generated waves; therefore, require annual repairs if they are not protected.

• The design of effective embankment protection requires knowledge of the wind‐generated wave characteristics and their relationship to embankment erosion.

• Irrigation reservoirs are commonly used for irrigation water storage in lower Mississippi river floodplain.

• A field measurement station was installed in an irrigation reservoir near Harrisburg, AR, to acquire synchronous measurements of wind and wave properties along with levee erosion data.



Field Site



Field Site

• Wave staffs• Wind gauge• Erosion pins• Ground‐based LIDAR



0

)( dffSfm ii

omo mH 004.4

Field Measurements

An example time series water surface displacement data (June, 2012, Jonesboro, AR). The vertical axis is vertical water surface displacement.

Five‐hour‐average energy spectrum of the measured waves in July 19, 2012

Wave period, wave height and wind speed histograms for the time period between June 2012 and October 2012.



Field Measurements

Wave characteristics R26(March 2005)

R26(June 2008)

R27(June 2012)

Wind speed, U10 (m/s) 14 (NE) 13 (SW) 9.5 (S)Fetch length 586 450 470Wave height, Hm0 (m) 0.25 0.23 0.14Peak period, Tp (s) 1.7 1.6 1.4Significant period, Ts (s) 1.7 1.6 1.2Mean period, Tm (s) 1.4 1.4 1.1Significant wave height, Hs (m) 0.23 0.20 0.13Maximum wave height, Hmax (m) 0.38 0.39 0.24RMS wave height, Hrms (m) 0.17 0.12 0.09

The ranges of measured wave parameters compared to field measurements in 2005, 2008 and 2012.



44.0

220 0025.0

AA

m

UgF

UgH

28.0

2415.00

AA

p

UgF

UgT

Wave Prediction

Method Hm0 (m) Tp (s) tmin(min)

JONSWAP 0.11 1.1 15.2

Wilson (1965) 0.17 1.3 12.5

SMB, Bretschneider (1970) 0.19 1.7 9.4

Krylow (1976) 0.21 1.6 ‐

Donelan (1980) 0.16 1.4 10.3

Ozeren and Wren (2010) 0.14 1.3 11.8

Comparison of empirical wind wave prediction methods

72.0

2min 087.42

AA UgF

Ugt



Erosion



Protection techniques



Floating Wave Barriers



Floating Wave Barriers

T = 0.6 s, H = 28 mm, h = 0.466m

2.00 2.24 2.48 2.72 2.96 3.20

x (m)

0.0

0.6

z (m)

t=24.399208 s

2.00 2.24 2.48 2.72 2.96 3.20

x (m)

t=24.598543 s

Laboratory and numerical experiments

Shafer lake (2005‐2009)



Shape and Orientation



Shape and Orientation

Internal Levees (U = 10 m/s) Floating wave barriers (U = 10 m/s, Breakwater size = 0.5 m)



LMRB



Irrigation reservoir

(R)

Area – A(m2)

Levee Length (m)

Max. Fetch – Fmax (m)

Max. fetch azimuth (deg.)

Shape factor

17 116,500 1,336 483 ‐35 1.0221 123,525 1,421 516 33 0.9514 125,753 1,404 500 ‐47 1.0120 126,755 1,377 510 49 1.0219 128,328 1,411 510 43 1.017 132,719 1,422 508 ‐49 1.043 138,417 1,585 636 22 0.7827 142,109 1,529 562 26 0.949 151,950 1,931 772 12 0.5811 163,354 1,927 796 72 0.64 164,865 1,626 605 ‐59 0.952 167,344 1,687 666 ‐37 0.848 180,782 1,842 715 22 0.7822 198,299 1,802 662 ‐31 0.9413 206,061 1,737 610 ‐51 1.123 209,621 2,150 660 ‐80 0.8410 234,147 1,871 677 ‐43 1.0518 251,165 2,199 866 19 0.7526 286,009 2,239 851 65 0.8512 300,383 2,244 836 ‐33 0.915 303,328 2,267 840 ‐31 0.915 341,414 2,368 865 ‐58 0.941 351,303 2,413 920 ‐30 0.96 462,435 2,742 1030 ‐44 0.9324 464,613 3,119 1119 19 0.7516 774,962 3,814 1472 47 0.7828 818,208 4,106 1311 ‐81 0.8625 1,264,481 4,561 1690 ‐24 0.93



• For a given wind speed, fetch length is the key parameter that controls the size of the waves generated in irrigation reservoirs.

• The orientation of the reservoir relative to the predominant wind direction has a strong influence on embankment erosion in irrigation reservoirs, such that, reducing the fetch length in the prevailing wind direction can significantly reduce embankment erosion.

• Ongoing experimental research and reservoir assessment field studies will provide better information about the relations between the wave size and the erosion retreat rate.

Conclusions



Acknowledgments Carlos AlonsoUSDA‐ARS National Sedimentation Lab. Oxford, MS (retired)

Denis CarmanWhite River Irrigation District, AR

Keith AdmireUSDA‐NRCS National Water Management Center Little Rock, AR

Mustafa AltinakarNCCHE, The University of Mississippi, Oxford, MS

Paul WorkUSGS, Sacramento, CA

Technical support:Glen GreyJacob FergusonAlan Barger

wind and wave measurments in irrigation reservoirs

Environment

ilnational center

computational hydroscience

university of mississippi

s fetchlength

u gf u gh

aa u gf u gt

tp s tmin

u10 ms