Irrigation Improvement Options part 1- on field irrigation

Transcription

1 Training Course Conceptual irrigation design in the context of IRBM Arba Minch University, Arba Minch March, 2012 Irrigation Improvement Options part 1- on field irrigation March 2012, Henk Ritzema

2 Hare Irrigation Scheme Inlet Crop

3 Case Study Area: Water shortage? What is causing the water shortage?

4 Contents Crop water requirements and irrigation scheduling Irrigation water requirements at field level Field irrigation systems Daily Water and Salt Balance Model

5 Irrigation: manipulating the water balance Inflow - Outflow =Change in storage (P+I) (T+E+R+D)= ±ΔS

6 Plant-Water-Atmosphere Movement of water due to Δ potential energy

7 How to calculate evapotranspiration 1. Reference Evapotranspiration (ET o ) based on climatic data 2.Crop Evapotranspiration (ET c ): ET c = k c * Et o where K c = crop coefficient, depending on crop type, crop variety and development stage

8 Crop coefficient K c depending on crop type, crop variety and development stage

9 From Crop water requirements Irrigation water requirements Soil properties affecting water flow and water storage in the soil: finer soil textures have higher water holding capacity compared to coarser soil textures, but available water depends on water holding capacity

10 Water holding capacity

11 Available Water Capacity (AWC) AWC = fc - wp where fc wp moisture content at field capacity moisture content at permanent point Soil texture Ө fc (m/m) Ө wp (m/m) AWC (m/m) Coarse sand Sand Loamy sand Sandy loam Loam Silt loam Silty clay loam Clay loam Silty clay Clay

12 CROPWAT Design: crop water requirements irrigation requirements Management: irrigation schedules scheme water supply for varying crop patterns. Evaluation: farmers irrigation practices crop performance under both rainfed and irrigated conditions

13 CROPWAT: input output INPUT: Reference Crop Evaporation (ET 0 ) using climatic data Rainfall Cropping pattern Soil type Scheduling criteria (e.g. 80 mm/14 days) OUTPUT: Reference Crop Evaporation Crop K c Effective rain Crop water requirements Exercise and or apply in Hare Irrigation Project Irrigation requirements TAM, RAM, ET c, ET c /ET max, daily soil moisture deficit, irrigation interval, irrigation losses and estimated yield reduction

14 Irrigation water requirements field irrigation system ET 0 ET c CWR IWR field irrigation system

15 Design of field irrigation system Input: IWR & AWC required water depth Soil Type Slope of field Width of furrow border Output: Length of field Flow rate Cutback time

16 SURDEV - Basin, border and furrow irrigation Design, operation and evaluation of basin, border and furrow irrigation

17 SURDEV Design of individual plot layout

18 SURDEV - Design of individual plot layout Matching field (physical) with operational parameters Output: length, width and slope with frequency, rate and duration

19 SURDEV - Evaluation operation efficiency Exercise and or apply in Hare Irrigation Project

20 Remember: Irrigation = manipulating the water balance To evaluate how you did this you can use: WaSIM (for Education) SWAP (for complex applications)

21 WaSim Daily Water and Salt Balance Model WaSim is a computer-based training package for the teaching and demonstration of issues involved in irrigation, drainage and salinity management. WaSim simulates soil water salinity relationships for designs and water management practices and environmental scenarios

22 SWAP - Soil, Water, Atmosphere and Plant SWAP simulates transport of water, solutes and heat in unsaturated/saturated soils at field scale level, during growing seasons and for long term time series. Used for: Education Applied Research Scenario studies

23 Application in this training course on Conceptual Irrigation design It is up to you: modelling assignments for case study area Good luck