Em4885 irrigation management practices to protect ground water

4 CHAPTER
IP 2.02.12 - Reduce Furrow Flows to Minimum Necessary to
Ensure Down-row Uniformity if Excess Runoff is a Problem
Objective
Minimize surface runoff from a furrow irrigation system while maintaining acceptable
down-row uniformity.
Description
Furrow irrigation involves runoff. The faster the advance of water down the furrow in
the initial wetting phase, the more runoff there will be, assuming that there is no cutback
flow used. Furrow flows should be reduced as much as possible while still maintaining an
acceptable advance ratio if runoff (or soil erosion) is a problem. If at that point there is still
too much runoff, consider using either surge flow (IP 2.02.03) or a cutback furrow flow
(IP 2.02.10), or installing a runoff reuse system (IP 2.02.11). Spreading straw in furrows
will also help to slow water advance and improve infiltration.
IP 2.02.13 - Control the Total Application of Water
Objective
Assuming distribution uniformity is acceptable, implementing this Practice will reduce
deep percolation to a minimum. The amount and disposition of surface runoff depends on
the specific management (surge flow, cutback, advance ratios) and whether runoff reuse
systems are used.
Description
This Practice requires four things:
1. The grower knows how much water is supposed to be applied. Some form of
irrigation scheduling (IP 2.01.05) should be used, even if it is using the feel method.
The “how much” to apply is the soil water deficit in the effective root zone along
with any required leaching water.
2. The water application is being measured (IP 2.01.01). Although a soil probe or
shovel can be used to judge the amount of water infiltrated during an irrigation,
modern irrigation managers utilize water measurement devices.
3. There are sufficient control structures in the irrigation system to control the
total application.
4. There is sufficient flexibility in the water supply to allow it to be turned on and
off as desired. A well provides that flexibility as the grower can turn it on and off
as desired. Water supplied by irrigation districts may not have this flexibility.
SCS National Practice 449 addresses general irrigation water management.
Practice 587 covers water control structures.
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