University of Hawaii at Manoa

University of

Hawaii at Manoa

Water

Sustainability

Studies

Technical

Memorandum #1 -

UH Manoa Campus

Water Use Study

2011

1

Water Sustainability Studies

UH Manoa Campus Water Use Study

Principal Investigator: Roger Babcock, Jr.

Students: Jayson Tasaka, Krishna Lamichhane, Yanling Li, Kristen Au

Civil & Environmental Engineering Dept. and Water Resources Research Center

Table of Contents 1. Introduction .............................................................................................................................................. 2

2. Water Usage on Campus .......................................................................................................................... 2

3. Methodologies .......................................................................................................................................... 4

3.1. Building water use ............................................................................................................................. 4

3.2. Chiller water use ................................................................................................................................ 6

3.3. Irrigation water use ........................................................................................................................... 8

2

1. Introduction The University of Hawaii Manoa (UHM) campus is a large facility located on 320 acres, containing almost 150

buildings, including classrooms, libraries, laboratories, dormitories, and various other support facilities. The area

also contains many roads, parking lots, and lots of beautiful green space. Potable water is used for in-building

uses such as drinking, washing, toilets, showers, and laboratory work. Potable water is also used for air

conditioning/chillers and landscape irrigation. From the various uses, wastewater is created and disposed into

the City collection system. On any given day, the number of people on campus may include 26-28,000 people.

Therefore, the UHM consumes a large quantity of water (about 1 MGD) and produces lots of wastewater. The

potable water is purchased from the Honolulu Board of Water Supply (BWS). Wastewater charges are also based

on potable water use. The purpose of this report is to evaluate the water use at UH Manoa by type/category of

use in order to facilitate conservation efforts, and to provide an evaluation of alternative potential non-potable

supplies to meet non-potable demands. The three major categories are In-Building (potable), Landscape

Irrigation (non-potable), and AC/Chillers (non-potable). These values are not readily available from UH Manoa

or the BWS, so a study with calculations was required.

2. Water Usage on Campus The best estimate of the breakdown of water use by category is shown in Figure 1, which indicates 45% In-

Building use, 33% Irrigation use, and 22% AC/Chiller use. Generally, UH Manoa campus consumes 1.08 million

gallons of potable water each day and discharges large quantities of wastewater. The combined costs for water

and wastewater are approximately $13K per day, or $5M per year. The number of total students in 2010 was

20,337. Therefore, the average cost per student is

approximately 64₵ per day, or $245 per year.

Monthly categorized water use and cost are tabulated in

Table 1 and also plotted in Figure 2. The building water use

was calculated from population attendance data and

estimated water usage per headcount. Chiller water use was

calculated from chiller capacity and building area. Irrigation

water use was calculated by the difference. The costs were

obtained from the UHM campus water bills. From Table 1,

the average annual cost of potable water was $1.2M and

sewage was $3.4M over the 2008-2010 years.

Figure TM1- 1: UH Manoa Campus Water Use Overview

Building, 483,000

gpd, 45%

AC/Chiller 243,000

gpd, 22%

Irrigation, 358,000

gpd, 33%

3

Table TM1- 1: UH Manoa Campus Water Usage Summary

FY Month Campus Population Building Chiller Irrigation Total Monthly Cost

Men Women Total gpd gpd gpd gpd Water Sewage Total

2008

Jul-08 10,441 7,853 18,294 354840 275003 314047 28710 $51,371.12 $ 141,246.97 $192,618.09

Aug-08 15,556 13,311 28,867 564774 277631 154713 30329 $87,192.01 $ 220,920.61 $308,112.62

Sep-08 16,139 14,004 30,143 590291 269807 128505 30070 $95,228.28 $ 220,691.33 $315,919.61

Oct-08 12,711 14,004 26,715 531569 229468 448563 36792 $105,598.73 $ 268,079.36 $373,678.09

Nov-08 13,070 14,502 27,572 548879 223430 78804 25888 $74,262.78 $ 188,804.80 $263,067.58

Dec-08 10,257 11,057 21,314 423490 203149 358644 29969 $86,003.21 $ 211,452.96 $297,456.17

Jan-09 11,193 12,166 23,359 464376 203672 192927 26188 $75,190.67 $ 190,824.66 $266,015.33

Feb-09 13,070 14,502 27,572 548879 213759 114874 26691 $76,638.69 $ 194,350.58 $270,989.27

Mar-09 12,091 13,280 25,371 504724 227927 123327 26036 $74,793.47 $ 189,482.21 $264,275.68

Apr-09 12,711 14,004 26,715 531569 250746 185641 29442 $84,588.74 $ 214,107.03 $298,695.77

May-09 11,355 12,425 23,780 472955 262011 320705 32110 $92,211.28 $ 233,938.42 $326,149.70

Jun-09 8,395 8,986 17,381 345183 274825 378359 30367 $89,625.86 $ 237,367.44 $326,993.30

TOTAL ANNUAL COST $992,704.84 $2,511,266.37 $3,503,971.21

2009

Jul-09 7,386 8,058 15,444 307102 275003 399331 29852 $91,230.85 $ 256,175.28 $347,406.13

Aug-09 12,103 13,524 25,627 510397 277631 222964 30751 $94,006.32 $ 263,812.17 $357,818.49

Sep-09 12,695 14,222 26,917 536180 269807 238901 31782 $97,125.01 $ 272,816.94 $369,941.95

Oct-09 12,695 14,222 26,917 536180 229468 452368 37048 $113,160.43 $ 318,083.80 $431,244.23

Nov-09 13,051 14,728 27,779 553618 223430 603610 41995 $128,185.55 $ 361,140.86 $489,326.41

Dec-09 10,270 11,279 21,549 428687 203149 369556 30459 $93,023.38 $ 262,174.06 $355,197.44

Jan-10 11,160 12,357 23,517 468091 203672 213114 26915 $111,159.57 $ 313,916.89 $425,076.46

Feb-10 13,051 14,728 27,779 553618 213759 544338 39898 $121,607.95 $ 343,718.40 $465,326.35

Mar-10 12,068 13,491 25,559 509058 227927 318226 32096 $98,476.50 $ 275,522.15 $373,998.65

Apr-10 12,695 14,222 26,917 536180 250746 404789 36248 $110,522.11 $ 312,411.18 $422,933.29

May-10 11,316 12,604 23,920 476299 262011 488386 37312 $115,786.04 $ 326,359.18 $442,145.22

Jun-10 8,400 9,189 17,589 349817 274825 1022908 50113 $154,965.27 $ 455,221.12 $618,497.64

TOTAL ANNUAL COST $1,329,248.98 $3,761,352.03 $5,098,912.26

2010

Jul-10 7,355 8,009 15,364 305473 275003 603809 36022 $114,319.95 $ 356,784.40 $471,104.35

Aug-10 12,075 13,462 25,537 508528 277631 556033 40825 $129,600.63 $ 404,388.62 $533,989.25

Sep-10 12,668 14,158 26,826 534284 269807 530836 40604 $128,800.86 $ 402,515.37 $531,316.23

Oct-10 12,668 14,158 26,826 534284 229468 491382 38177 $121,046.83 $ 378,850.25 $499,897.08

Nov-10 13,009 14,660 27,669 551375 223430 158532 28389 $89,986.63 $ 282,032.45 $372,019.08

Dec-10 10,275 11,219 21,494 427429 203149 372721 30517 $96,723.40 $ 303,225.12 $399,948.52

Jan-11 11,138 12,297 23,435 466370 203672 400029 32548 $103,212.40 $ 323,102.04 $426,314.44

Feb-11 13,009 14,660 27,669 551375 213759 449792 36954 $116,951.71 $ 367,710.48 $484,662.19

Mar-11 12,038 13,428 25,466 507132 227927 520732 38197 $120,999.82 $ 371,581.84 $492,581.66

Apr-11 12,668 14,158 26,826 534284 250746 134006 27954 $87,428.62 $ 278,208.63 $365,637.25

May-11 11,278 12,529 23,807 473967 262011 224909 29227 $92,723.97 $ 281,090.40 $373,814.37

Jun-11 8,380 9,132 17,512 348198 274825 359202 29876 $94,785.16 $ 302,458.82 $397,243.98

TOTAL ANNUAL COST $1,296,579.98 $4,051,948.42 $5,348,528.40

AVERAGE ANNUAL COST $1,206,177.93 $3,441,522.27 $4,650,470.62

4

Figure TM1- 2: UH Manoa Campus Water Usage Breakdown

3. Methodologies

3.1. Building water use

The calculation of building water use was estimated from two major facts: population on campus and water

usage per person per day. Population data were obtained from the UH Office of the Vice Chancellor for

Academic Affairs, Manoa Institutional Research. The major population groups are summarized in Table 2-1 and

2-2. The water usage per person is estimated by generally observed behaviors and is listed in Table 3. The total

water usage is then calculated as total attendance multiplied by water usage per person. Table 4 is estimated

campus attendance of different population groups based on class schedules.

Table TM1- 2: Campus Population of Students

Fiscal Year

Undergraduate Graduate Unclassified

Men Women Men Women Men Women

2008 6198 7240 2389 3151 428 763

2009 6275 7308 2413 3313 411 715

2010 6303 7296 2363 3363 351 661

5

Table TM1- 3: Campus Population of Faculties (M for Men, W for Women)

Executive Admin Faculty Lecturers

Grad Assistants Admin/Tech Staff Others

M W M W M W M W M W M W M W

60 32 1408 1076 145 183 682 605 595 733 410 556 1083 608

57 35 1358 1053 85 102 645 647 568 725 382 506 1187 760

56 34 1278 1014 103 116 683 662 548 719 365 471 1267 730

Table TM1- 4: Water Daily Usage Estimate/Headcount

Type Usage per Day Fixture

flow rate

Unit Men Women

Toilet 0.2 4 1.6 gpf

Urinal 3 0 1.6 gpf

Faucet 3 4 4 gpm

Showerhead 0.01 0.01 1 gpm

Others - - - -

Total water 17.13 22.41 gpd

Total water 0.521038 0.68 1000 gal/mo

Table TM1- 5: Monthly Attendances in Percentage

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Undergraduate 80 100 90 100 80 50 30 90 100 100 100 80

Graduate 80 100 90 90 80 70 80 90 90 90 100 60

Unclassified 20 50 30 30 50 0 0 30 30 30 50 0

Executive Admin 95 90 90 90 95 85 85 95 90 90 90 90

Faculty 100 100 100 100 100 80 80 100 100 100 100 80

Lecturers 100 100 100 100 100 40 40 100 100 100 100 40

Grad Assistants 95 100 95 95 100 60 60 100 95 95 100 95

Admin/Tech 100 100 100 100 100 100 100 100 100 100 100 100

Staff 100 100 100 100 100 100 100 100 100 100 100 100

Others 90 90 90 90 90 90 90 90 90 90 90 90

6

3.2. Chiller water use

When reversed calculated by the manufacture data of cooling tower models, average water consumption used

by all campus chillers is around 192,025 gpd. See Table 5. But when combining cooling area of the buildings and

cooling tower model data, the total use of chiller water is 242,619 gallons per day. The large number is selected

since in reality most manufacturers’ data are generally considered conservative.

Table TM1- 6: Chiller water usage calculation by cooling tower model

Quantity Building Type Model Number Tons GPD Tons/GPD

2 Agricultural Science BAC Cooling Tower VT1-N209-OMLX 418

2 Architecture School BAC Cooling Tower VTL-126-MCW 252

1 Art BAC Cooling Tower T1662NMCL 662

1 Bilger Addition BAC Cooling Tower 3643-2CL 1238

2 Biomedical Science Counterflow Ceramic

Cooling Tower N/A N/A

1 Business

Administration BAC Cooling Tower VT1-375-PCL 375

1 Gilmore Hall BAC Cooling Tower VT1-N255-PMCL 255

1 Hamilton Library BAC Cooling Tower 3665-2C 1284

3 Hamilton Library

Addition Evapco Cooling Towers LSTA8P-243 1758

2 Hawaii Hall Marley Quadraflow

Cooling Towers 23224-LS 1096

1 Hawaii Institute for

Geophysics BAC Cooling Tower T-1462-PMCWR 800

4 Holmes Hall Evapco Cooling Towers LSWA 87 C 5380 25500 0.211

1 Institute for Astronomy BAC Cooling Tower F1443 PLT 443

1 Hawaiian Studies BAC Cooling Tower VFL-722-MLX 722

1 Kuykendall Hall BAC Cooling Tower VXT-105 LT 105 800 0.225

1 Kuykendall Hall BAC Cooling Tower VXT-75 LT 75

2 Marine Sciences BAC Cooling Tower VT0-154-NCL 308 5100 0.060

1 Moore Hall BAC Cooling Tower 3341 LS 341

1 Music Complex BAC Cooling Tower VT0-78 KMCLX 78

3 POST BAC Cooling Tower VT1-921-OMCWS 2763 22400 0.123

2 QLC BAC Cooling Tower VTL-209-OCL 418

2 Saunders Hall BAC Cooling Tower VXT-N215-CWR 430 4900 0.088

2 Stan Sheriff Center Evapco Cooling Towers AT 24818 B 962

1 St. John Plant Evapco Cooling Towers AT8 125 2000

1 Watanabe Hall BAC Cooling Tower 3455A-MM 455

1 Webster Hall BAC Cooling Tower VC1-307 MMO 307

2 Wist Hall BAC Cooling Tower VTL-059 H 118

Total Load 23043 tons

Average tons/gpd factor 0.141

Total Water Use 192025 gpd

7

Table TM1- 7: Chiller water usage calculation by cooling tower model and building areas

Building Area Floors Total Area

(sqft) Tons

Load Factor

Evap Water (gpm)

Evap Water (gpd)

Cycles Makeup

Water (gpd)

Holmes Hall 7614596 4 207916.56 693 0.7 14.55 20958 3 10,479

Sakamaki Hall 2641120 4 73364.444 245 0.6 4.40 6339 2.5 4,226

Watanabe 1860703 4 51686.194 172 0.6 3.10 4466 2.5 2,977

Art 8352569 2 116007.9 387 0.6 6.96 10023 2.5 6,682

Kuykendall 1454232 4 40395.333 135 0.6 2.42 3490 2.5 2,327

MSB 1633328 7.5 85069.167 284 0.6 5.10 7350 2.5 4,900

POST 4096200 9 256012.5 853 0.8 20.48 29493 2.5 19,662

Saunders 3061775 5.5 103192.8 344 0.6 6.19 8916 2.5 5,944

East West Center 5063311 4 140647.53 469 0.6 8.44 12152 2.5 8,101

Campus Center 2984560 3 62178.333 207 0.6 3.73 5372 2.5 3,581

Kennedy Theater 3105300 2 43129.167 144 0.5 2.16 3105 2.5 2,070

Jefferson Hall 3684691 2 51176.264 171 0.6 3.07 4422 2.5 2,948

Physical Science 1901776 3 39620.333 132 0.6 2.38 3423 2.5 2,282

Bilger Addition 1679108 5 58302.361 194 0.8 4.66 6716 2.5 4,478

Bilger Hall 1675261 3 34901.271 116 0.6 2.09 3015 2.5 2,010

Architecture 4351320 2 55435 185 0.6 3.33 4790 2.5 3,193

George Hall 2548708 3 53098.083 177 0.6 3.19 4588 2.5 3,058

Crawford Hall 1103422 3 22987.958 77 0.6 1.38 1986 2.5 1,324

Hawaii Hall 1679958 3 34999.125 117 0.6 2.10 3024 2.5 2,016

QLC 3932889 3 69935.188 233 0.6 4.20 6042 2.5 4,028

Bus Ad 8185851 3 170538.56 568 0.6 10.23 14735 2.5 9,823

Webster 1860589 4 51683.028 172 0.6 3.10 4465 2.5 2,977

Spalding 810237 4 22506.583 75 0.6 1.35 1945 2.5 1,296

Hamilton Annex 3117724 5 108254.31 361 0.7 7.58 10912 2.5 7,275

Hamilton 5517872 4 153274.22 511 0.7 10.73 15450 2.5 10,300

Paradise Palms 1599718 1 11109.153 37 0.6 0.67 960 2.5 640

Moore Hall 27413299 5 951850.66 3173 0.6 57.11 82240 2.5 54,827

St. John 1917401 6 79891.708 266 0.6 4.79 6903 2.5 4,602

Gilmore Hall 1499622 7 72898.292 243 0.6 4.37 6298 2.5 4,199

Agricultural Engineering

1867785 1 12970.729 43 0.6 0.78 1121 2.5 747

Sherman Laboratory 3222822 2 44761.417 149 0.6 2.69 3867 2.5 2,578

Pope Lab 1451321 2 20157.236 67 0.6 1.21 1742 2.5 1,161

C-More Hall 2 30000 100 0.6 1.80 2592 2.5 1,728

Biomed 6456556 2 89674.389 299 0.6 5.38 7748 2.5 5,165

Biomed Middle 984417 8 54689.833 182 0.6 3.28 4725 2.5 3,150

Auxillary Services 2630313 1 18266.063 61 0.6 1.10 1578 2.5 1,052

Agricultural Science 3299731 4 91659.194 306 0.6 5.50 7919 2.5 5,280

Law 3577121 2 49682.236 166 0.6 2.98 4293 2.5 2,862

Law Library 4518921 1 31381.396 105 0.6 1.88 2711 2.5 1,808

Stan Sherrif 10655482 5 369982.01 1233 0.7 25.90 37294 2.5 24,863

Total (gpd) 242,619

8

In the final calculation, monthly usage is also factored with the temperature and precipitation effects by

assuming less water lost in the evaporation during low temperature and high humidity conditions and vice versa.

The annual climate data and calculation factors are listed in Table 7. Both temperature and rain factors are

weighted against the average; overall factor is the average of the two.

Table TM1- 8: Climate Factors for Chiller Evaporation

Temp (F) Rain Temp

Factor Rain

Factor Overall Factor

Month Low High Average Inches % % %

Jan 65.7 80.4 73.05 2.73 94.30 73.60 83.95

Feb 65.4 80.7 73.05 2.35 94.30 81.91 88.10

Mar 66.9 81.7 74.3 1.89 95.91 91.98 93.94

Apr 68.2 83.1 75.65 1.11 97.65 109.04 103.35

May 69.6 84.9 77.25 0.78 99.72 116.27 107.99

Jun 72.1 86.9 79.5 0.43 102.62 123.92 113.27

Jul 73.8 87.8 80.8 0.5 104.30 122.39 113.35

Aug 74.7 88.9 81.8 0.46 105.59 123.27 114.43

Sept 74.2 88.9 81.55 0.74 105.27 117.14 111.21

Oct 73.2 87.2 80.2 2.18 103.53 85.63 94.58

Nov 71.1 84.3 77.7 2.26 100.30 83.88 92.09

Dec 67.8 81.7 74.75 2.85 96.49 70.97 83.73

3.3. Irrigation water use Irrigation water (358,000 gpd) is calculated as the total minus building and chiller usage, since there is no other

major water usage. Given the total vegetation coved area of UH (approximated from GIS map) is around 98.69

acres, 358,000 gpd is equivalent to around 0.13 inches per day of irrigation. This is a reasonable estimation since

most lawn management guide specifies an amount of 0.1 inches daily. The spike in June of 2010 shown is Figure

2 is caused by an alleged water leak. A brief irrigation demand curve is plotted in Figure 3, which can be used as

design criteria for non-potable irrigation system. The percentage means to what extent the system is able to

meet the water demand with a given capacity. For example, a 500,000 gallon storage tank is able to meet 83

percent of the irrigation demand during the period of 2008 to 2010.

9

Figure TM1- 3: Irrigation Water Demand on UH Manoa Campus