CT4410: Distribution and management
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CT4410: Distribution and management

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CT4410: Distribution and management CT4410: Distribution and management Presentation Transcript

  • Farmers and irrigation Irrigation and Drainage CT4410 Maurits Ertsen December 14, 2011 1 Water Resources Management
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  • Outlet structures in India (Mollinga and Bolding)What does the figure show?An intake / outlet is not just atechnical ‘thing’.It is also a social ‘thing’: it createssocial action.And it is the result of social action. 5
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  • Groundwater use in Pakistan 8
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  • Campo de Cartagena 21
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  • Original designPressurized systemConstant flowTime measurementPrepared for sprinkler,suitable for surfaceirrigation 23
  • But, what happened? Constant flow appeared to be less constant… Two responses from farmers: Water meters: from time to flow On-farm storage 24
  • Proyecto Rio Dulce 25
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  • CT3Tertiary unit CT3 C1 C9 C3 C5 C7 C2 C4 28
  • The average farmer in CT3 irrigated about 7 hectares,using a flow of 200 l/s for three hours,thus putting on a hectare about 2.200 m3 (220 mm).This same average farmer irrigated 2 times in the season. Canal Mean Maximum Minimum C2 1.2 2 1 C4 1.7 3 1 C5 1.9 3 1 C3 2 3 1CT3 (Tertiairy canal) 2.1 6 1 C7 2.3 4 1 C9 3.3 6 1 29
  • Comunero Flow max (l/s) Flow min (l/s) Min/max C2 230 172 0.75 C3 235 198 0.84 C5 290 265 0.91 C9 238 122 0.51 C4 254 116 0.46 CT3 250 175 0.7Responses:Farmers irrigate longer or more oftenFarmers decrease their irrigated area during the seasonFarmers increase their irrigated area during the season 30
  • Irrigation: water control Irrigation and Drainage CT4410 1 Water Resources Management
  • What to do? December 14, 2011 2
  • Water control: Main issues Please note that water allocation (and water • Distribution: demand or supply rights) is a very important issue, • Free demand or arranged demand but that we do not discuss that • Control: Upstream or downstream now • Type of (configurations of) structures to use • Sensitivity and flexibility December 14, 2011 3
  • What is desirable on system levelDecember 14, 2011 4
  • Whatcan beselec-ted December 14, 2011 5
  • ProportionalDecember 14, 2011 6
  • Proportional (splitted)December 14, 2011 7
  • What is this?December 14, 2011 8
  • Proportional, but arrangedDecember 14, 2011 9
  • Variable (adjustable) flows:continuouslyDecember 14, 2011 10
  • Variable flow: intermittentDecember 14, 2011 11
  • December 14, 2011 12
  • December 14, 2011 13
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  • Demand based, downstream controlDecember 14, 2011 15
  • Which element supports downstream control and which element does not?December 14, 2011 16
  • SensitivityDecember 14, 2011 17
  • SensitivityDecember 14, 2011 18
  • Hydraulic flexibilityDecember 14, 2011 19
  • Fluctuations in the systemDecember 14, 2011 20
  • ExamplesDecember 14, 2011 21
  • Irrigation design Irrigation and Drainage CT4410 Maurits Ertsen 1 Water Resources Management
  • Most of you worked a little mechanical on the irrigation needs. Looking at these from a slightly bigger distance shows that we have a cropping pattern that can be sustained on pre-sowing gifts and some additional irrigation later in the cropping cycle. Basically, in fall, things may become a little tricky. The rhythm of the cropping pattern suggests that you are dealing with an irrigation system that needs to give supplemental water, in addition to rainfall. The pre-sowing gift is likely to be one of the more important irrigation turns to consider.Another issue is how to deal with water needs and water availability. Quite a few of you seem to confuse supply and demand management – which is a way to organize water allocation and distribution – with upstream of downstream control – which are hydraulic terms. I can have demand management with upstream control. December 14, 2011 2
  • Most of you show what the systems will look like. Not that many can clearly tell me what the system is supposed to do. I have not really seen any sensible arrangement of how water needs, water supply, canals and units are linked in terms of water quantities and timing of irrigation turns.As your system needs to work in all kind of circumstances, you cannot base your design on a typical organizational model. Yet, you have to design a system with flows and controls, which is obviously somehow connected to an organizational model. A way to deal with this paradox is make it very clear what actions are needed in your system to ensure the functioning of the system. When should structures be opened or closed, that kind of issues. Who opens or closes them is almost irrelevant.I have seen many different layouts, and with all of them I am not sure that you have the required head loss available to irrigate all fields. You need to check much more carefully whether the available energy levels and gradients allow the designs you want. December 14, 2011 3
  • Delivering water in a gravity system is a combination of Matching needs with availability Thinking of a smart irrigation rhythm Think of control actions and structures Fit the infrastructure in the topographyLinking water needs and water availability typically could be arranged with two strategies. Either one aims to ensure that the correct flow is on the correct place at the correct time – this requires pretty precise water control – or one ensures that the correct amount can be drawn on (almost) any place at the time needed, which decouples main system supply and water use. Obviously, storage will be needed between main system and water use. December 14, 2011 4
  • 10 m in about 8 km Gradient = 10/8000 = 0.00125 If I could use a canal gradient of 0.0001 for some 4 km, I need about 4000*0.0001 = 0.4 m of head 12 m That leaves plenty of meters22 m storage upstream for 19 m 17 mDecember 14, 2011 5 15 m