Performance Evaluation of Irrigation Projects - Practices of Irrigation and On-farm Water Management - page 129

• Advance phases and time

• Recession time

• Topography of the field

• Crop type and stage of the crop

The measurement steps and procedures are as follows:

- The border dimensions can be measured using a “measuring tape.”
- Soil surface elevations (at different points, 10-30 m interval along the borders) can
be determined using a “total topographic station” or “Level instrument.” Slope and
standard deviation of soil surface elevations can be determined from the measured
data.
- The “inflow” or “irrigation discharge” can be measured using suitable flow
measuring device such as mini-propeller meter and flume.
- The advance phase can be determined from recording of the advance time to
reference points located along the border (every 10-30 m).
- A number of flow depth measurements are to be performed across the border,
every 5-10 m. The average of all measurements is used to represent the flow
depth at this point and time.
- The flow depth at the upstream end of the border is to be measured shortly before
cutoff.
- In open border, surface runoff (if conditions permit) is to be monitored. The runoff
can be measured using the mini-propeller meter or a flume.

A hydrograph is to be established from discharge measurements, and its time
integration will yield the runoff volume.

- Infiltration in “ring infiltrometer” and border infiltration can be correlated,
and a relationship can be established. Then the infiltration parameters can be
determined.
- To estimate the infiltrated depths of water (required for computing uniformity
and efficiency indices), field data from evaluation can be utilized to derive
the infiltration parameters of a Kostiakov type infiltration equation. The infil-
tration parameters ( K , a ) and roughness coefficient ( N ) can be determined
through the solution of inverse surface irrigation problem (Katapodes et al.,
1990 ) .
For that, a hydrodynamic one-dimensional surface irrigation model (e.g.,
SIRMOD) can be used. Such a model is to be executed using tentative values
of the coefficient “ K ” and the exponential “ a ” from the Kostiakov infiltra-
tion equation, and the Manning's N . The parameters should be adjusted until
the model satisfactorily reproduces the experimental values of flow depth and
irrigation advance for each evaluation.
- Performance indices - application efficiency and the low-quarter distribution
uniformity - should be determined using the formula described in an earlier
section.