Water Application Methods - Practices of Irrigation and On-farm Water Management - page 39

downstream losses, like for furrow irrigation. Larger inflow rates are utilized when
the field slope is very small with management becoming similar to that of basins.
Automated water control is often applied.
If it is possible, irrigate each block of border individually when irrigating. To
maintain control with border irrigation, discharge the well into the top block until
the desired application is achieved. The total well discharge then is moved to the
second border and the first levee cut. Erosion control measures may be required if
large stream sizes are used.
2.3.1.2 Suitability, Capabilities, and Limitations of Border Method
Crop Suitability
Border irrigation is best adapted to grain and forage crops where there are large
areas of flat topography and water supplies are large. Border irrigation could be
used on precision leveled rice fields, where beans or other grain crops are grown in
rotation with rice.
Soil and Land Suitability
Border irrigation system performs better when soils are uniform, and the slope is
mild. Undulating topography and shallow soils do not respond well to grading to a
plane. Steep slopes and irregular topography increase the cost of land leveling and
reduce border size. Deep cuts may expose areas of nonproductive soils, requiring
special fertility management.
Economy and Financial Involvement
The major investment in border irrigation is that of land grading or leveling. The cost
is directly related to the volume of earth that must be moved, the area to be finished,
and the length and size of farm canals. Border irrigation is relatively inexpensive to
operate after installation.
Attainable Irrigation Efficiency
Reasonable irrigation efficiency is possible with border irrigation method. Typical
efficiencies for border strip irrigation ranges from 70 to 85%. With the border
method, runoff return flow systems may be needed to achieve high water use
efficiency.
The system designer and operator can control many of the factors affecting irri-
gation efficiency, but the potential uniformity of water application with surface
irrigation is limited by the variability of soil properties (primarily infiltration rate)
throughout the field. Results of field studies indicate that even for relatively uniform
soils, there may be a distribution uniformity of infiltration rates of only about 80%.