Proposed Standard for Automatic Calculation of Rainfall Erosivity

Proposed Standard for Automatic Calculation of Rainfall

Erosivity

Manuel Reyes, Hiroshi Suda, Mark Brooks, and Ryan Boyles

21st Century Watershed Technology: Improving Water Quality and the Environment

EARTH University, Costa Rica February 21-24, 2010

Hiroshi SudaNorth Carolina Agricultural and Technical State University

Mark BrooksState Climate Office of North Carolina

Ryan BoylesState Climate Office of North Carolina

Proposed Standard for Automatic Calculation of Rainfall Erosivity

• Accepted for publication in the

Applied Engineering in Agriculture journal of the American Society of Agricultural and Biological

Engineers May and June 2010 issue (tentative)

Outline• Objectives• What is rainfall intensity percentage (RIP)?

• What is automatic calculation of rainfall erosivity (ACRE)?

• Methodology for web access

• Recommendation

• Discussion

Objective

• To describe how daily erosivity values are automatically calculated from the State

Climate Office of North Carolina climate stations

• To propose that this methodology be adopted as a standard method of calculating daily

rainfall erosivity



• Methodology for Website access

• Recommendation

• Discussion

Rainfall Intensity Percentage RIP

– Idea came from the thesis of Dr. Norman Hudson (read his thesis in Silsoe)

–Developed by Reyes (1989) as Master of Philosophy thesis in Silsoe

College,

Cranfield

University, United Kingdom

–Applied to Baton Rouge, Louisiana rainfall as a special topics problem in a

meteorology class at Louisiana State University in 1990

Published in TRANSACTIONS of the ASAE 1993

Rainfall Intensity Percentage RIP

– A measure of the intensity distribution of daily rainfall

– Quantifies the distribution of daily rainfall amount by class

RIP

• Calculated using:

where

RIPk

= rainfall intensity percentage in rainfall intensity class k

(By

)k

= rainfall amount of event y in rainfall intensity class k

P = total daily rainfall

zk

= daily number of events in class k. An event is defined as

a rainfall depth accumulated in a fixed‐time‐base interval,

and is extracted from autographic rainfall records

Example RIP CalculationSummation of 1 minute rainfall amounts into 5

minute intervals (June 3, 2009 rainfall, NCA&T weather station)

Time Rainfall Amount (mm) 5 Minute Rainfall Amount17:26 4.06417:27 2.03217:28 1.77817:29 3.55617:30 2.032 13.46217:31 1.2717:32 0.76217:33 1.2717:34 2.79417:35 2.54 8.636

Example RIP Calculation

Time5 minute

rainfall (mm)

Duration

(min)

intensity

(mm/h)

Time

(cont.)

5 minute

rainfall

(mm)

Duration

(min)

intensity

(mm/h)

16:55 ‐ ‐ ‐ 18:10 2.79 5 33.5317:00 0.51 5 6.10 18:15 0.25 5 3.0517:20 0.00 20 0.00 18:20 0.76 5 9.1417:25 2.54 5 30.48 18:25 0.76 5 9.1417:30 13.46 5 161.54 18:30 0.25 5 3.0517:35 8.64 5 103.63 18:35 4.57 5 54.8617:40 10.16 5 121.92 18:40 2.03 5 24.3817:45 8.89 5 106.68 18:45 0.25 5 3.0517:50 4.83 5 57.91 20:15 0.00 90 0.0017:55 4.57 5 54.86 20:20 0.25 5 3.0518:00 3.30 5 39.62 20:45 0.00 25 0.0018:05 4.32 5 51.82 20:50 0.25 5 3.05

Total Rain (mm)73.41

Intensity class = 0 – 20 mm/h

Time5 minute

rainfall (mm)

Duration

(min)

intensity

(mm/h)

Time

(cont.)

5 minute

rainfall

(mm)

Duration

(min)

intensity

(mm/h)

16:55 ‐ ‐ ‐ 18:10 2.79 5 33.5317:00 0.51 5 6.10 18:15 0.25 5 3.0517:20 0.00 20 0.00 18:20 0.76 5 9.1417:25 2.54 5 30.48 18:25 0.76 5 9.1417:30 13.46 5 161.54 18:30 0.25 5 3.0517:35 8.64 5 103.63 18:35 4.57 5 54.8617:40 10.16 5 121.92 18:40 2.03 5 24.3817:45 8.89 5 106.68 18:45 0.25 5 3.0517:50 4.83 5 57.91 20:15 0.00 90 0.0017:55 4.57 5 54.86 20:20 0.25 5 3.0518:00 3.30 5 39.62 20:45 0.00 25 0.0018:05 4.32 5 51.82 20:50 0.25 5 3.05



Using

RIP0‐20

= * 100

RIP0‐20

= 4%

.51 + .25 + .76 + .76 + .25 + .25 + .25 + .25

73.41

Intensity class = 20 – 40 mm/h

Time5 minute

rainfall (mm)

Duration

(min)

intensity

(mm/h)

Time

(cont.)

5 minute

rainfall

(mm)

Duration

(min)

intensity

(mm/h)

16:55 ‐ ‐ ‐ 18:10 2.79 5 33.5317:00 0.51 5 6.10 18:15 0.25 5 3.0517:20 0.00 20 0.00 18:20 0.76 5 9.1417:25 2.54 5 30.48 18:25 0.76 5 9.1417:30 13.46 5 161.54 18:30 0.25 5 3.0517:35 8.64 5 103.63 18:35 4.57 5 54.8617:40 10.16 5 121.92 18:40 2.03 5 24.3817:45 8.89 5 106.68 18:45 0.25 5 3.0517:50 4.83 5 57.91 20:15 0.00 90 0.0017:55 4.57 5 54.86 20:20 0.25 5 3.0518:00 3.30 5 39.62 20:45 0.00 25 0.0018:05 4.32 5 51.82 20:50 0.25 5 3.05



Using

RIP20‐40

= * 100

RIP20‐40

= 15%

2.54 + 3.30 + 2.79 + 2.03

73.41


By repeating this calculation we get the following table:

RIP RIP RIP RIP RIP RIP(0 ‐

20 mm/h) (20‐40 mm/h) (40 ‐60 mm/h) (60 ‐80 mm/h) (80 ‐100 mm/h) (>100 mm/h)

4% 15% 25% 0% 0% 56%



• Methodology for website access

• Recommendation

• Discussion

Automatic Calculation of Rainfall Erosivity

ACRE• A method of automatically calculating

erosivity using rainfall events measured by dataloggers

ACRE paper published in TRANSACTIONS of

the ASAE 1995

ACRE Erosivity Index

• The Daily Erosivity Index (DEI30

) is calculated using the

equation:

where

DEI30

= the daily erosivity index

Ed

= estimated daily rainfall kinetic energy

(I30

)d

= maximum daily 30‐minute intensity

Daily Rainfall Kinetic Energy

• The estimated daily rainfall kinetic energy is calculated using

the equation (Reyes 1989):

where

Ed


P = total rainfall amount

UKEk

= unit kinetic energy using the mean of the RIP kth

intensity class

interval as I

RIPk

= rainfall intensity percentage in a rainfall intensity class k

Unit Kinetic Energy• Unit kinetic energy is calculated using the

equation:;

if k ≥

76 mm/h, UKEk

= 28.3 J / m2

mm

where

UKEk

= metric form of unit kinetic energy from Wischmeier

and Smith’s (1978) equation in J m‐2

mm‐1

I = rainfall intensity (mm/h)

ACRE Erosivity Index

• The Daily Erosivity Index (DEI30

) is calculated using the

equation:

where

DEI30

= the daily erosivity index

Ed


(I30

)d

= maximum daily 30‐minute intensity

Calculating (I30

)dTime

5 Minute Rainfall

Amount (mm)

30 Minute Rainfall

Amount

30 Minute Rainfall

Intensity

16:55 0 0 017:00 0.51 0.51 1.017:05 0 0.51 1.017:10 0 0.51 1.017:15 0 0.51 1.017:20 0 0.51 1.017:25 2.5 3.0 6.117:30 13.5 16.0 32.017:35 8.6 24.6 49.317:40 10.2 34. 8 69.617:45 8.9 43.7 87.417:50 4.8 48.5 97.117:55 4.6 50.5 101.118:00 3.3 40.4 80.818:05 4.3 36.1 72.118:10 2.8 28.7 57.418:15 0.25 20.1 40.1

Example Erosivity Calculation

From the example above:

Where (I30

)d

= 101.1 mm/h and

Given P=total rainfall = 73.41mm

Example Erosivity Calculation

UKE10

= 11.9+8.7 log10

(10) = 20.6 J/ m2

mm

UKE30

= 11.9+8.7 log10

(30) = 24.8 J/ m2

mm

UKE50

= 11.9+8.7 log10

(50) = 26.7 J/ m2

mm

UKE70

= 11.9+8.7 log10

(70) = 28.0 J/ m2

mm

UKE90

= 28.3 J / m2

mm (since K ≥

76 mm/h)

UKE100

= 28.3 J / m2

mm (since K ≥

76 mm/h)

Example ACRE Erosivity Calculation

Therefore

Ed

= 73.41

= 1987 J / m2

And

DEI30

= Ed

(I30

)d

= 1987 J / m2

(101.1 mm / h)

DEI30

= 200886 J mm m‐2h‐1

20.6 J/ m2

mm(4%) + 24.8 J/ m2

mm(15%) + 26.7 J/ m2

mm(25%) + 28.3 J / m2

mm(56%)

100



• Methodology for Website access

• Recommendation

• Discussion

Proposed ACRE Web Accessible Method to be published in TRANSACTIONS of ASABE

Weather Stations• There are currently 14 weather stations with

daily erosivity available online (the only weather stations applying ACRE method in the world)

• Horticultural Crops Research Station (CAST)• Horticultural Crops Research Station (CLIN)• Upper Mountain Research Station (LAUR)• Lake Wheeler Rd Field Lab (LAKE)• Central Crops Research Station (CLAY)• NC A&T SU Research Farm (NCAT)• Buckland Elementary (BUCK)• NC Electric Cooperative Anson Peaking Plant (LILE)• Hamlet Tower (HAML)• Mount Mitchell State Park (MITC)• Williamsdale

Field Lab (WILD)• Taylorsville Tower (TAYL)• North Durham Water Reclamation Facility (DURH)• Burnsville Tower (BURN)

Weather station on a mountain in North Carolina

The automatic calculation of rainfall erosivity available from the State Climate Office of North Caroline is the only system of its kind on the world.

Weather Stations• There are currently 14 weather stations with

daily erosivity available online (the only weather stations applying ACRE method in the world)

• Horticultural Crops Research Station (CAST)• Horticultural Crops Research Station (CLIN)• Upper Mountain Research Station (LAUR)• Lake Wheeler Rd Field Lab (LAKE)• Central Crops Research Station (CLAY)

• NC A&T SU Research Farm (NCAT)• Buckland Elementary (BUCK)• NC Electric Cooperative Anson Peaking Plant (LILE)• Hamlet Tower (HAML)• Mount Mitchell State Park (MITC)• Williamsdale

Field Lab (WILD)• Taylorsville Tower (TAYL)• North Durham Water Reclamation Facility (DURH)• Burnsville Tower (BURN)

NC A&T Weather Station

Retrieving Data

• To retrieve the erosivity data, first go to the NC Climate Office CRONOS website

(http://www.nc‐climate.ncsu.edu/cronos)

• From here, type the name of the station you wish to view the data for, or use the four

letter code given on the previous slide

http://www.nc-climate.ncsu.edu/cronos

Retrieving Data

Type station name

or 4 letter code

here

Retrieving Data

• If a list of stations appears, click on the name of the desired station to navigate to its data

retrieval page

• From the data retrieval page, click on the “daily”

tab

Click here

Retrieving Data

• Immediately below the Daily tab you may select the number of days you

wish to retrieve data for.

• Scroll down to “Daily Moisture Parameters”

and click the checkbox for

daily erosivity. You may also select any other desired parameters.

Check this box

Retrieving Data

• Scroll down to the bottom of the page and click the “RETRIEVE DATA”

button

Click here to

retrieve data

Use this to change the

output format (Web

page, Excel spreadsheet,

or text file)

Retrieving Data

• If you select webpage format, the data will be given as shown below.

RIP RIP RIP RIP RIP RIP(0 ‐

20 mm/h) (20‐40 mm/h) (40 ‐60 mm/h) (60 ‐80 mm/h) (80 ‐100 mm/h) (>100 mm/h)

4% 15% 25% 0% 0% 56%

DEI30 = 200886 J mm m-2h-1(I30)d = 101.1 mm/h




• Recommendation

• Discussion

Recommendation

The ACRE method of: (1) summarizing short duration rainfall intensities and (2) calculating

of daily rainfall erosivity be adopted as a standard method.




• Recommendation

• Discussion and Questions

Discussion and questions

I will take notes:

Proposed Standard for Automatic Calculation of Rainfall Erosivity

Documents

Transcript of Proposed Standard for Automatic Calculation of Rainfall Erosivity