PROGRAM GOALS. ⢠To Replace water-thirsty turf with trees and shrubs. ⢠To save time by .... CEA-Hort (Barbara Storz). â City of College Station personnel.
Predicting Water Use in Urban Residential Landscapes R. D. Havlak, R. H. White, D. R. Chalmers, W. A. Mackay, J. C. Thomas
During the summer, it is estimated that 25 to 60 % of the water used by residential customers is applied to the landscape.
Texas Single Family Home Lawns Maintenance Practices Aeration 4 6
Soil testing Disease Control
Activity
19 29 34
Dethatching Clippings removal
50 62
Weed Control
78 94
Insect Control Fertilizer
0 10 20 30 40 50 60 70 80 90 100
Irrigation
Percentage Source: The Economic Impact of the Texas Turfgrass Industry
Take a Look at the “Whole Landscape” ü In urban landscapes, irrigation requirements have been determined for turfgrasses but not for most landscape species. (Costello et al, 2000) ü Evidence that homeowner irrigation practices did not change substantially with changes in landscape design. (Peterson et al, 1999)
WaterWise Landscape Rebate Program
PROGRAM GOALS • • • •
To Replace water-thirsty turf with trees and shrubs To save time by installing low maintenance shrubs and mulch To choose the right plant for the right place To reduce future demand on the water utility and create beautiful, drought tolerant landscapes. Austin, Texas
Do Trees and Shrubs Influence Water Use? ü In typical clay-loam soils, most tree roots are usually located less than 8 to 12 inches below the surface and grow outward far beyond the branch tips of the tree. (Perry, 1982) ü Does actual landscape water use change substantially when trees and shrubs are added? Does actual homeowner water use change?
300 250
Mesquite Oak Willow
200 150 100
Devitt et al. 1995 J. of Turfgrass Management 1:47-62
MONTH
Dec
Oct
Aug
Jun
Apr
Feb
Dec
Oct
Aug
Jun
0
Apr
50
Feb
EVAPOTRANSPIRATION
Bermuda/Ryegrass
Research Objectives 1. Determine if correlations exist for water use between 6 landscape species 2. Identify water use patterns for a landscape and its plant components 3. Compare daily water use versus potential evapotranspiration for a multiple plant species landscape
Research Objectives (cont.) 4. Establish seasonal water use coefficients for a landscape and its plant components 5. Evaluate actual water use between xeric and mesic landscapes, trained and untrained homeowners, and 2 – 5, 8 – 12, and 20+ year old landscapes
Research Locations
Brazos County
Hidalgo County
Research Materials and Methods 1. Texas ELITE Program ”Efficient Landscape Irrigation Through Education” •
Collaborative effort with Hidalgo Co. CEAHort and Master Gardener volunteers
•
Evaluating actual water use by trained vs. untrained homeowners with xeric and mesic landscape types
Research Materials and Methods 1. Texas ELITE Program (cont.) ”Efficient Landscape Irrigation Through Education” Twelve (12) Landscapes 6 xeric landscapes and 6 mesic landscapes 3 response unit sites (trained) 3 standard practice sites (untrained)
Research Materials and Methods 2. Effects of Landscape Maturity on Homeowner Water Use • •
Collaborative effort with City of College Station - Water Conservation personnel Evaluate 1997 - 2002 water use data ü 2 – 5 year old landscapes ü 8 – 12 year old landscapes ü 20+ year old landscapes
40
40
35
35
30
30
25
25
20
20
15
15
10
10
5
5
0
0 1
2
3
4
5
6
7
MONTH
8
PET (1000 gallons)
WATER USE (1000 gallons)
Water Use Data Comparisons for 2-5, 8-12, and 20+ Year Old Landscapes (2000)
2-5 8 - 12 20+ PET
9 10 11 12 (Based on a 7000 sq. ft. landscape and a 0.6 landscape coefficient)
Research Materials and Methods 3. Rainfall Interception by Tree Canopies •
3 Post Oak and 3 Live Oak trees ü 6 rainfall gauges randomly placed beneath canopy ü Data collected and gauges randomly rearranged after each rainfall event ü 3 rainfall gauges in non-canopy areas
Research Materials and Methods 4. Soil Water Dynamics in a Landscape With Multiple Vegetation Types • • •
Location: Weslaco Ext. & Res. Center Soil type: Willacy fine sandy loam Nov. 2002: Installed 192 ECHO volumetric soil moisture sensors Ø 64 sensor locations—3 sensors/location ü 0” – 8” depth (A) ü 8” – 16” depth (B) ü 16” – 24” depth (C)
Landscape Vegetation Types Evaluated ü Mature Walnut Tree/St. Augustinegrass – Measurements from 10’, 20’, and 30’ from the base of the tree
ü ü ü ü ü
Crepe Myrtles/St. Augustinegrass St. Augustinegrass Rose Bushes Ficus Hedge Dwarf Yaupon Hedge
Research Materials and Methods Data Collection and Analysis • •
Daily soil water content (inches) Daily soil water loss (inches) -Soil depths = A, B, C, A+B, B+C, Total -Lc values = actual ET/potential ET
•
Daily PET and rainfall data collected from nearby weather station
Volumetric Water Content (%)
Sensor Response to a 1.0" Rainfall Event 35 Sensor #40 Measurements
30 25 20 15 0
800
1600
Time (Hours)
2400
Volumetric Water Content (%)
Sensor Response to Soil Moisture Fluctuations 26 25.8 25.6 25.4 25.2 25 24.8 24.6 24.4 24.2 24
Sensor #30 Measurements
0
8 16 24 32 40 48 Time (Hours)
Soil Water Loss/Gain (Inches)
Total Increase in Soil Moisture vs. Daily Rainfall 1.5 1 0.5 0 -0.5 -1 -1.5
Landscape Rainfall
35
45
55
65
Time (Days)
75
Soil Water Loss (Inches)
Total Soil Water Loss vs. Potential Evapotranspiration (PET) 0.2 TR-10 TR-20
0.15
TR-30 0.1
SA Landscape
0.05
PET
0 89 90 91 92 93 94 95 96 97 Time (Days)
Total Daily Water Loss Compared to PET (Between Rainfall Events) May 2 - May 14
Soil Water Loss (Inches)
0.30 0.25 TR-10
0.20
TR-20 TR-30
0.15
SA PET
0.10 0.05 0.00 122
124
126
128
130
Time (Days)
132
134
Total Daily Water Loss Compared to PET (Between Rainfall Events) June 8 - June 13
Soil Water Loss (Inches)
0.30 0.25
TR-10
0.20
TR-20 TR-30
0.15
SA PET
0.10 0.05 0.00 159
160
161
162
163
Time (Days)
164
165
Soil Water Loss by Depth for St. Augustinegrass (June 8-13)
Soil Water Loss (Inches)
0.3 0.25 0"-8"
0.2
8"-16" 16"-24"
0.15
Total 0.1
PET
0.05 0 159
160
161
162 Time (Days)
163
164
165
Soil Water Loss by Depth for Tree-30 (June 8-13)
Soil Water Loss (Inches)
0.3 0.25 0"-8"
0.2
8"-16" 0.15
16"-24" Total
0.1
PET
0.05 0 159
160
161
162
Time (Days)
163
164
165
Total Daily Water Loss Compared to PET (Between Rainfall Events) June 8 - June 13
Soil Water Loss (Inches)
0.3 0.25
FI DY
0.2
RB
0.15
CM
0.1
PET
0.05 0 159
160
161
162 Time (Days)
163
164
165
PET (Inches)
Lc (Percent)
Landscape Coefficient Compared to PET (May 31 - June 13) 1 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0
Lc PET
1
3
5
7 Time (Days)
9
11
13
Weekly Summation of Soil Water Loss 1.80
Soil Water Loss (Inches)
1.60 1.40 1.20 1.00
Landscape
0.80
PET
0.60 0.40 0.20 0.00 0.00
5.00
10.00
15.00
Time (Weeks)
20.00
25.00
Soil Water Loss (Inches)
Monthly Summation of Soil Water Loss (February and March) TR-10 TR-20 3.5 TR-30 3 SA 2.5 FI 2
DY RB CM
1.5 1 0.5
Landscape PET
0 February Time (Months)
March
Soil Water Loss (Inches)
Monthly Summation of Soil Water Loss (April and May) 5.5 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0
TR-10 TR-20 TR-30 SA FI DY RB CM Landscape PET April
May
Time (Months)
April 12, 2003 Total Actual ET
April 12, 2003 Actual ET 4-6 pm
June 8, 2003 Total ET
June 9, 2003 Total ET
June 10, 2003 Total ET
June 11, 2003 Total ET
June 12, 2003 Total ET
June 13, 2003 Total ET
Acknowledgements Funding: ü USDA-Cooperative State Research, Education, and Extension Service -Rio Grande Basin Initiative ü Texas Water Resource Institute ü Texas Turfgrass Association
Acknowledgements Collaborations: ü ü ü ü ü
Weslaco Ext. and Res. Center personnel Hidalgo Co. Master Gardener volunteers Hidalgo Co. CEA-Hort (Barbara Storz) City of College Station personnel Turfgrass Staff – Texas A&M University
