UK Centre for Water Efficient Technologies

(“WET” Centre)

WET Centre

WET Centre, 24 July 2018

WET Centre

Rain Water Harvesting (RWH)

www.newleafirrigation.co.uk

WET Centre

Overview

Installation of a RWH system in the WET Centre required

ground, structural, hydraulic and electrical works

The cost of the materials and installation was £12,621 (not

including gutters)

In situ monitoring of rainfall events

Electronic recording of rain volume harvested

Objectives

To determine optimum system design

To identify opportunities for improvements

To provide a case study for the industry

To develop a credible cost/benefit analysis

To gather robust data on water savings

To understand the limitations of RWH

Construction

WET Centre

WET Centre RWH system

Environmental Agency, 2009.

Rainwater Harvesting: an on-farm guide p18. Principles of an indirect system

Storage

tank

Sump

tank

Rain water

harvesting

area

(1,720 m2)

North

150 m3

10 m3

Sump tank

Storage tank

WET Centre

Design variables

For an “average” climatic year

150 m3 capacity tank

Collecting rain water from 1,720 m2

Average water use per hectare for a strawberry

crop of 2,495 m3 (WATERR project)

Will RWH provide sufficient water for the WET

Centre production area (0.34 ha)?

Limitations

Design compromises made to meet available budget

Storage capacity (150 m3) may not be enough in wet years, during winter months, in

exceptional rainfall events or during droughts

No filters installed in the input line

No removal of biological contaminants

Storage tank

Rainfall at EM, 30-year average, 1981 - 2010

WET Centre

2017

RWH in a “typical” year – towards self sufficiency?

How much of the 648 mm of rainfall can be collected and used for irrigation?

Does sufficient rainfall occur at the right time of year for strawberry production?

During intense rainfall events, how much water is lost (e.g. surplus water siphoned from

underground sump and runs to waste)?

How much rain water is “lost” in a typical year? (~155 mm, Jan - Mar)

Does the collected rain water need to be treated to remove biological contaminants?

357 mm rainfall at EM Apr - Oct

Polytunnel roof area ~ 1,720 m2

Run-off co-efficient = 0.85

357 x 1,720 x 0.85 = = 522 m3

150 m3 stored over Nov – March

Total volume collected = 672 m3

Equivalent to 3,907 m3 / ha

Crop Water applied

m3 / hectare

Average Range

Raspberry

Substrate 1,509 650 - 2,600

Strawberry

Substrate 2,495 1,275 - 3,942

WET Centre

Rainfall at EM, August 2017 – July 2018

WET Centre

Date

01/08/17 01/10/17 01/12/17 01/02/18 01/04/18 01/06/18

Ra

infa

ll (m

m p

er

da

y)

0

10

20

30

40 Year Month Rainfall (mm)

Actual LTA Difference

2017 July 73.2 40.2 33

2017 August 48.4 51.6 -3.2

2017 September 27.6 54 -26.4

2017 October 8.4 73.9 -65.5

2017 November 34.6 68.7 -34.1

2017 December 74.6 66.4 8.2

2018 January 60.6 66.1 -5.5

2018 February 33.6 43.7 -10.1

2018 March 61.8 45.4 16.4

2018 April 79.8 46.2 33.6

2018 May 38.4 48.9 -10.5

2018 June 0.6 42.8 -42.2

2018 July 1.0 40.2 -39.2

Total 542.6 -146

2017 was a “drier than average year”: 282 mm rainfall between April – Oct 2017

WET Centre

Summary of RWH to date (2017 – 2018)

Overview

RWH fully installed by 18/07/17

Measuring hardware operational by 11/08/17

Main pump down until 17/08/17

Storage tank full on 02/12/17

Rainfall over period: 184 m3

Water pumped from Sump tank: 174 m3

155 mm (266 m3) “lost” between Jan – Mar 2018 W

ate

r vo

lum

e (

m3)

2018 season

Starting with a full header tank (150 m3)

Malling™ Centenary planted on 31 March and 1 May

Resumption of RWH on 23 April 2018

Data being recorded over the 2018 growing season

NIAB EMR to prepare a cost/benefit analysis

0

50

100

150

200

250

300

17

/08

/17

17

/09

/17

17

/10

/17

17

/11

/17

17

/12

/17

17

/01

/18

17

/02

/18

17

/03

/18

17

/04

/18

17

/05

/18

17

/06

/18

Rain water harvesting (10 months)

Run-off efficiency at EM = 95%

WET Centre

Year Rainfall (mm)

Jan-Dec Apr-Dec

2012 901 866

2013 724 691

2014 924 588

2015 622 453

2016 583 342

2017 505 357

2018

LTA

275

648

116

492

Rainfall in atypical years: 2012, 2017

2012 Spring

2012 Autumn

2012 Summer

2017 Spring

2017 Autumn

2017 Summer

WET Centre

Date

01/04/12 01/06/12 01/08/12 01/10/12 01/12/12

Ra

infa

ll (c

um

mu

lative

mm

pe

r m

on

th)

0

20

40

60

80

100

120

140

160

180

Date

01/04/17 01/06/17 01/08/17 01/10/17 01/12/17

Ra

infa

ll (c

um

mu

lative

mm

pe

r m

on

th)

0

20

40

60

80

100

120

140

160

180

2012

Apr–Dec: 866 mm, ~ 1,490 m3

2017

Apr–Dec:391 mm, ~ 673 m3

2012

Apr–Dec = 866 mm

1,490 m3

8,662 m3 ha-1

350% of water needed

2017

Apr–Dec = 391 mm

673 m3

3,910 m3 ha-1

157% of water needed

2018

Apr–July = 117 mm

201 m3

1,170 m3 ha-1

System performance in atypical years: 2012, 2017, 2018

Input-output balance will inform recommendations on optimum storage tank volume and likely

top-up volumes (mains) needed

RWH: Case study – additional benefits

Better soil drainage between polytunnels

Improved humidity control within the polytunnels

“Marked improvement in plant health”

Reduce soil erosion and compaction

www.newleafirrigation.co.uk

WET Centre

Rain water harvesting

www.newleafirrigation.co.uk