WHAT IS THE STATE OF OUR WATER SOURCES IN THE WESTERN CAPE AND FUTURE WEATHER TRENDS

Transcription

1 WHAT IS THE STATE OF OUR WATER SOURCES IN THE WESTERN CAPE AND FUTURE WEATHER TRENDS CRI Information Day Alle Bleue : 27 October 2017 A S Roux Pr Eng

2 Content of presentation Limited water resources available Climate FruitLook project Take home message Sustainable Resource Management Private Bag X1, Elsenburg, Stellenbosch, South Africa. 7607

3 When the well is dry, we learn the worth of water. Benjamin Franklin

4 Water is for fighting, whiskey is for drinking Mark Twain

5 2 % POLAR ICE CAPS 97% OCEANS 1% AVAILABLE FOR USE

6 All the fresh water on earth will fill a droplet with a diameter of km Western Cape Government

7 Western Cape Government

8 ANNUAL RAINFALL 857 mm mm 470 mm 80 % in 5 MONTHS WORLD HAWAII Western Cape Government 2012 SOUTH AFRICA 8

9 National Rainfall and Evaporation 9

10 Unique situation of Western Cape Winter 90% of our rain 25% of the demand Somer 10% of our rain 75% of the demand We thus need to store our winter runoff in dams to be available in summer for irrigation 10

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12 Water availability (Million m 3 /a) WMA Natural MAR Ecological Reserve Yield Irrigation use Other use Total use Balance Gouritz Olifants/ Doorn Breede Berg

13 Climate Western Cape Government

14 CONTRASTS 14

15 Western Cape Government

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17 Document Reference #: ops-fcast-ct-059.1

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19 Annual Rainfall figures for Cape Town Weather Office: 1993 till current. Document Reference #: ops-ppt-ct-034.1

20 Rainfall: May to Aug 2017 Area May-17 Jun-17 Jul-17 Aug-17 Long term % Mth LT Mth LT Mth LT Mth LT Total Average Ashton Rawsonville Robertson Worcester

21 Western Cape Government

22 Western Cape Government

23 Outlook for: November 2017 February 2018 (Rainfall) The projection for November 2017 through to February 2018 is for above normal rainfall for the Western and Northern Cape. This is favorable for the summer rainfall region for the Western Cape and Northern Cape. Document Reference #: ops-ppt-ct Western Cape Government 2012

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25 Climate change? Max temp ever on earth in October measured in Vredendal 48.3 C 25

26 Longer Term Climate Outlook More frequent severe weather events Increases in temperature in many regions and resulting changes in precipitation patterns Estimated that by 2050, rainfall in the Western Cape is likely to have decreased by 30% More flooding events less infiltration and recharge of ground water Quality of the water resource, as impacted on by human activities, becomes even more important More fires and droughts poorer water quality (erosion) 26

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28 Agro-meteorological situation in Western Cape Normally winter rain start around the Easter Weekend Winter rain started very late, first significant rain in June Below normal rain fell in May to September (+-50% of Long Term average) which had significant impact on water levels in our major storage dams Dam levels much lower than corresponding time last year Area % on 23/10/ 2017 % on 23/10/2016 % on 23/10/2015 Berg Breede Olifants/Doorn Gouritz WC Province Cape Town supply

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30 Theewaterskloof Dam water levels Percentage Months 120 Dams providing water to Greater Cape Town Percentage Months 30

31 Critical dam levels Dam % on 23/10/2017 % change from last week % on 23/10/2016 Storage capacity Mm 3 Greater Brandvlei Theewaterskloof Voëlvlei Berg River Clanwilliam

32 WC Water Supply System Western Cape Government

33 WC Water Supply System Yield of system: Original system 475 Mm 3 pa Bergrivier Dam 81 Mm 3 pa Total 556 Mm 3 pa Yield: The maximum quantity of water obtainable on a sustainable basis from a dam(s), river or groundwater source in any hydrological year (at a certain level of risk), and under specified conditions of catchment development and system operation. 33

34 Theewaterskloof Dam Inlet to tunnel at Charmaine 30 April

35 Inlet to tunnel at Charmaine 24 May

36 Draaiberg Bridge and Vyeboom Irrigation Scheme Pump Station 24 May

37 Theewaterskloof Dam 24 May

38 Challenges Western Cape Government

39 OVERVIEW OF WATER SITUATION Dam levels currently (16 October) at 35.8% (versus 62.4% in 2016) Thus 42.6% lower Water restrictions for agricultural sector varies between 50% and more than 80% Lower Olifants River Area (Clanwilliam, Klawer, Vredendal) only allocated 17.5% of normal water allocation Western Cape Government 2012 Economic Impact Assessement of AI

40 FruitLook: Innovative method to increase water use efficiency in Agriculture Western Cape Government

41 Western Cape Government

42 Need Improve efficiency of resource use National Water Act (1998): water should be used more efficiently Mitigate impacts of climate change WUE = Crop yield (kg) Water consumption (m 3 ) or Option 1: Reduce water consumption without decrease in yield Option 2: Increase yield without increasing water consumption 42

43 Water Mass Balance S = (I + R + U) - (D + RO + ET) Rain Transpiration Evapo-transpiration Runoff Irrigation Evaporation Root Zone Water Storage Below Root Zone Drainage - Capillary Fares, A. and A.K. Alva (1997) 43

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45 Western Cape Government

46 Remote sensing Sun Satellite Two sources of radiation: Solar radiation visible near infrared short-wave infrared Earth Surface thermal infrared Western Cape Government

47 An image of a surface and its surface Western Cape Government

48 Surface Energy Balance Algorithm for Land (SEBAL) ET is calculated as the residual of the energy balance 48

49 FruitLook Structure Western Cape Government

50 FruitLook Area: Western Cape Western Cape Government 2012 Crops Hectares Grapes 118,900 Deciduous fruit 30,500 Citrus 12,000 Stone fruit 21,000 Total fruits 182,500 51

51 The FruitLook Data Portal Data accessible online through the FruitLook data portal: Free subscription User needs to provide block boundaries once Weekly updates on 9 growth parameters from September to April

52 FruitLook Data Portal MOISTURE GROWTH MINERALS

53 FruitLook overview Web portal containing spatial, remote sensing derived data Growing seasons (35 weeks): 2016/ / / / / / /11 Weekly time interval Area: WC Deciduous Fruit producing areas 9 weekly updated growth data components MOISTURE: Actual evapotranspiration Evapotranspiration deficit Crop factor Biomass water use efficiency GROWTH: Biomass production Leaf Area Index NDVI MINERALS: Nitrogen content (plant) Nitrogen content (top leaf) 20 x 20 meter pixels

54 The FruitLook Data Portal Change in time Change in space

55 FruitLook Data Portal: MyField Analysis In this example three fields from the Grabouw area are compared for the season. The deviating trend in field Grabouw3 is clearly visible.

56 FruitLook Data Portal: MyField Analysis Compare: - Seasons - Blocks - Fertilizer Treatments - Varieties - Irrigation Schemes

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58 Seeing is believing? 59

59 Time & Space sample / see 60

60 Comparison energy (i) Rn H ET G 61

61 FruitLook Use: Disease Detection ) Identification of area with poorer biomass growth 2) Strategic soil sampling of these areas to analyse for nematode presence 3) Treatment of affected areas only Strategic treatment saved 75-80% Block more uniform after treatment 62

62 FruitLook Use: Sampling / Zonation 63

63 FruitLook Use Example Poor yield caused by insufficient irrigation in critical growth stages. 64

64 FruitLook Impact Over 450 active users; Over 32,000 ha in active use; Water productivity improved more than 10% for 60% of the users Unique project in the world for improving production and resource use at an unprecedented scale 65

65 Vorige en 2016/17 FruitLook bedieningsgebied 66

66 Voordele? Vermindering in koste van 10 % (water, brandstof, bemesting, ander) Toename van 10% in opbrengs Finansiele gewin: Wyndruiwe: Tafeldruiwe: Sagtevrugte: R /ha R /ha R /ha 67

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68 Take home message

69 Water is a limited resource Severe water restrictions unavoidable this season Optimal water utilisation required to save the crop Water conservation by all user sectors are not negotiable It is the responsibility of every citizen to conserve water and to protect our resources Start with small efforts close tap while brushing teeth Take a short shower Reuse shower water on your plants Western Cape Government

70 Come gather round people wherever you roam And admit that the waters around you have grown And accept it that soon you ll be drenched to the bone. If your time to you is worth savin Then you better start swimmin or you ll sink like a stone For the times they are a-changin Bob Dylan 71

71 Thank You

72 Contact Us Andre Roux Pr Eng Sustainable Resource Management Tel: Fax: