Water Conservation practices for landscape irrigation

Transcription

1 Water Conservation practices for landscape irrigation Meagan Donnelly: Coordinator Water Wise and Research SABI Congress 2017 FOR FURTHER INFORMATION ON WATER WISE, PLEASE CONTACT US ON:

2 Introduction and Outline Where does our water comes from? What is the current water situation? The impact of Climate Change Water restrictions How much water is used in a landscape? Potential tools to calculate outdoor water use Common water conservation principles

3 Where does our water come from? An introduction to Rand Water Rand Water is a bulk supplier of potable (drinking) water for most of Gauteng and some neighbouring provinces. Rand Water receives water through the Lesotho Highlands Water Project (LHWP) and the upper Vaal River Catchment. This transfer scheme transports water from Katse Dam in Lesotho to the Vaal River and Dam in Gauteng.

4 Where does our water come from? An introduction to Rand Water Katse Dam is part of the LHWP It is 185m high (2nd highest in Africa) The dam supplies SA with litres of water per second The water is used to generate electricity in Lesotho and SA

5 Where does our water come from? An introduction to Rand Water Raw (untreated) water is abstracted from the Vaal Dam to the purification stations in Vereeniging and Zwartkopjes. It is then purified to ensure the final product meets international standards. It is pumped to municipal reservoirs and distributed to the end consumer. DWS = custodian of water resources in SA RW = bulk water services provider (buy and treat) Municipalities = provide water to end user

6 Where does our water come from? An introduction to Rand Water km 2 WINTERVELDT RUSTENBURG PRETORIA BRITS JOHANNESBURG Rand Water purifies 4800 Megalitres of water per day Clean drinking water is distributed to 58 reservoirs, via 3400 km of pipelines, to 19 municipalities It services over 15 million people in Gauteng and parts of Mpumalanga, North West and Free State. CARLETONVILLE BETHAL VEREENIGING VAAL RIVER SASOLBURG VAAL DAM VAAL RIVER HEILBRON

7 What is our current water situation? Water Availability 97% of all water on earth in in the oceans Only 3% of all water on earth is fresh water 2% in in the polar ice caps LESS THAN 1% is available for use in lakes and rivers

8 What is our current water situation? Water Availability SA is classified as water scarce The world average rainfall is around 860mm per year SA receives approximately 497mm per year with 65% of the country receiving less than 500mm per annum Rainfall is not distributed evenly throughout the year Rainfall is not distributed evenly throughout the province Rainfall records from 1900 s till 1980 s show that the annual rainfall has been decreasing since 1968 UNEP, 2002 The number of disasters has increased in frequency and severity in the past 30 years UNEP, 2002

9 What is our current water situation? Water Availability DWA info shows: Dams levels in Gauteng are higher than at the same time last year IVRS River System State of Dams on # Means latest available data FSC is full storage capacity in million cubic meters Dam River FSC This Week Last Week Last Year Bloemhof Dam Vaal River Grootdraai Dam Vaal River Katse Dam Malibamatso River Mohale Dam Senqunyane River Nooitgedacht Dam Komati River Sterkfontein Dam Nuwejaarspruit River Vaal Dam Vaal River Westoe Dam Usutu River Woodstock Dam Tugela River Total

10 What is our current water situation? Water Availability DWA info shows: Dams levels in WC are lower than at the same time last year Cape Town River System State of Dams on # Means latest available data FSC is full storage capacity in million cubic meters Dam River FSC This Week Last Week Last Year Berg River Dam Berg River Steenbras Dam-Lower Steenbras River Steenbras Dam-Upper Steenbras River Theewaterskloof Dam Riviersonderend River Voelvlei Dam Voelvlei River Wemmershoek Dam Wemmers River Total

11 What is our current water situation? Water Availability In most areas in of South Africa evapotranspiration is higher than the rainfall received Winter, 2010 Annual evapotranspiration ranges from 1100mm 4000mm Conversion ratios of rain available as surface water: stream flow into rivers Canada: 65% Australia: 9.8% South Africa: 8.6% World Bank Group, 2015

12 The impact of Climate Change Changes in weather Decreased yield in vineyards Hot & dry Cool & wet Increased variability Slightly wetter on average, but wetter wets & drier drys. Becoming frost-free Encroachment of ecosystems Expect increase in minimum temperatures. Generally hotter and drier conditions in South Africa Wetter Wets and Drier Drys Rainfall to become more unpredictable and extreme Northern Region prediction: 5-10% decrease in rain and increase in evapotranspiration

13 The impact of Climate Change Changes in plants Evidence that natural biomes are changing, some are expanding while others are retracting Stevens et al, 2015 Changes in temperature impact where agricultural crops are grown Impact on ornamental plants? Impact on biodiversity

14 Water restrictions The status quo Level 4 restrictions implemented in the Cape 100 litres /person/day No landscape watering allowed with municipal water Restrictions in Gauteng lifted Recommendations made at municipal level regarding watering times etc.. Map key Name Code Seat Area (km²) Population (2011) [1] J City of Johannesburg Metropolitan Municipality JHB Johannesburg 1,645 4,434,827 T City of Tshwane Metropolitan Municipality TSH Pretoria 6,345 2,921,488 E Ekurhuleni Metropolitan Municipality EKU Germiston 1,924 3,178, Sedibeng District Municipality DC42 Vereeniging 4, , West Rand District Municipality DC48 Randfontein 4, ,995 P

15 How much water is used in a landscape? What has been documented Bill & Veck (2000) noted the following in Alberton: Alberton total group Average water usage 26 (Kilo-litres per month) Indoor usage 81% Outdoor water usage 19% Garden 14% Car 1% Other 4%

16 How much water is used in a landscape? What has been documented Other Reports: Bill&Veck 2000 Jacobs et al 2004 duplessis &Jacobs 2014 UNISA 2015 Wright& Jacobs 2016 Area Gauteng Stellenbosch Australia Gauteng Cape Town Indoor usage 81% 63% 74.6% 93-54% 65% Outdoor usage 19% 37% 25.4% 7-46% 35% Garden 14% 20% Alternative Sources Notes Perceptions of water use are 24% lower than actual % Varies based on irrigation, outdoor water features, pools Grey water Weekly watering No automation 35% Boreholes Seasonal variability. Linked to water restrictions

17 How much water is used in a landscape? What does this tell us? Landscape water use is difficult to calculate Landscape water use in Gauteng is different to Western Cape Water restrictions influence water use patterns Availability of water varies Knowledge of alternative water sources varies Outdoor water use is dependant on numerous factors Price of water Size of property Plant choice Weather Water pressure Behavioural factors Method of irrigation Time of irrigation Frequency of irrigation

18 Potential tools to calculate outdoor water use What is available? Potential formulas have been established but need more testing e.g. Jacobs et al, du Plessis & Jacobs, Wright & Jacobs Water Wise Calculator Tool for domestic users Determines water usage activities Specific to Gauteng Available on Water Wise website To be developed into an app for national use Landscape water use formula Being developed as part of a PhD study Take into account numerous site specific factors Quantifies water use in a landscape and factors that could reduce water use

19 Common water conservation principles Irrespective of province Understand your landscape Soil type, slope, weather conditions (rainfall, evapotranspiration, wind) Group plants according to their watering needs (1-drop / 2-drop /3-drop) Hydro zone your landscape (High / Medium / Low) Irrigate according to zones based on water needs Water less frequently but more deeply Time of irrigation In line with provincial water restrictions Minimize water lost through evapotranspiration Method of irrigation most efficient Install water meters in the landscape Use alternative sources of water

20 Common water conservation principles Irrespective of province What is a Water Wise Plant? Planted in the right zone Watered based on its watering needs Maintained according to irrigation design (H, M, L)

21 Common water conservation principles Irrespective of province What is a Water Wise Plant / Hydro zone? Summer- 25mm(100%)/week Spring/Autumn- 15mm(60%)/week High Medium Low No watering Winter-12mm (50%)/week Summer- 15mm(60%)/week Spring/Autumn- 12mm(50%)/week Winter-7mm (25%)/week Summer-12mm(50%)/week Spring/Autumn- 7mm(25%)/week Winter-12mm every second week (including lawns but not at all if dormant) No watering required unless in extreme cases Receive over > 750mm of annual rainfall. Water once a week in general, and twice or three times a week during very hot dry spells Receive between mm rainfall a year. If they show signs of distress in dry times water. Water once a month in winter. Receive annual rainfall of between mm rainfall. Water every 6-8 weeks Receive less than 300mm rainfall per annum. Water only in severe cases.

22 Concluding comments Landscape water use is variable Potable water use for landscape irrigation is become more restricted Need to use water wisely Be innovative in approach to water use in landscapes Promote education on water conservation practices for landscapes

23 Questions? Please visit our website and click on the Water Wise logo Meagan Donnelly / Thank You!