Manual - Participatory rapid diagnosis and action ... - FAO.org

PRDA Manual 57(Plot distributionefficiency)Only carry out this measurement when high water losses arecausing constraints as it is relatively time-consuming.Method 1: Distribution efficiency between furrows/basins:• Measure discharge and application time at the beginningof several furrows on a plot. Compare the total appliedvolume per unit length/area to see if water is distributedevenly among them.Method 2: Distribution efficiency within a furrow:• Measure discharge at the beginning, middle and end ofeach furrow.• Calculate the infiltration for both parts of the furrow(=upstream inflow – downstream outflow at the dischargemeasurement location).• Compare the infiltration rate in the upper and lower halfof the furrow. Ideally they are almost equal.Discharge measurements within plots can be done with smallflumes or V-notches (cheaper and easier to operate).Transect walkWhyTransect walks are a structured way to walk through an area to observeparticular things or indicators (such as water availability, maintenance status,crop diseases). They provide a good first overview of the irrigation schemeand plot use.How to1. Decide what things to observe during the transect walk and dividetasks amongst the team members.2. Assemble a group of farmers and start by briefly introducing thepurpose of the tool. Make sure that it is clear to everyone.3. Ask farmers to indicate their own plot on your sketch map of theirrigation schemes. If you do not have a sketch map you can askfarmers to draw one on-the-spot before you start.4. Ask farmers to take you to their own fields but follow the route thatthe water takes to get there. You, therefore, start at the headwork andthen follow the water delivery system from the primary canal all theway to a tertiary unit and the farmers’ inlet.