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**Irrigation water management (IWM)** is the process of determining and
controlling the volume, frequency, and application rate of irrigation
water in a planned, efficient manner.

# Purpose

IWM is applied as part of a conservation management system to support
one or more of the following:

-   Manage soil moisture to promote desired crop response

-   Optimize use of available water supplies

-   Minimize irrigation induced soil erosion

-   Decrease non-point source pollution of surface and groundwater
    resources

-   Manage salts in the crop root zone

-   Manage air, soil, or plant micro-climate

# Use

This practice is applicable to all irrigated lands.

An irrigation system adapted for site conditions (soil, slope, crop
grown, climate, water quantity and quality, etc.) must be available and
capable of applying irrigation water to meet the intended purpose(s).

# Conservation Management Systems

IWM is generally one of several components of a resource management
system used to manage water supplied to a crop through an irrigation
system that is part of an overall

resource management plan for the irrigated cropland.

**Irrigation Water Management Planning**

IWM components of the conservation plan will contain the following
information:

-   field map(s) and soil survey information

-   crop rotation or sequence

-   recommended irrigation water application rates, timing and method of
    application

-   locations of designated sensitive areas

-   guidelines for irrigation system operation and maintenance

IWM is most effective when used in conjunction with other conservation
practices such as irrigation system design, cover crop, residue
management, conservation buffers, nutrient management, pest management
and conservation crop rotation.

IWM requires knowledge, skills and the desire to determine when
irrigation water should be applied. The main factors influencing IWM are
***irrigation interval*** (time between irrigations), ***irrigation**
**set** **time*** (time water is applied) and ***application rate***
(rate at which water is applied). These parameters define the timing and
duration of irrigation and the amount of water applied. System design
and maintenance are also important factors influencing IWM.

**Water Rights**

Under Idaho law, all water is publicly owned. Anyone planning to store
or divert surface or groundwater for the purpose of irrigation must
obtain a permit or water right from the Idaho Department of Water
Resources. These permits or water rights must be obtained prior to the
use of the water. It is the responsibility of the landowner to file for
the necessary permits or water rights.

# Operation and maintenance

There are no operation and maintenance (O&M) aspects applicable to this
standard. Necessary O&M items are addressed in the physical component
standards considered as companions to this standard.

####### Specifications

Site-specific requirements for IWM are listed on specification sheets.
Specifications are prepared

in accordance with the NRCS Field Office Technical Guide. Refer to the
NRCS practice standard, Irrigation Water Management, (449). Use a *Soil
Survey* and NRCS National Engineering Handbook, Part 652 -- *Irrigation
Guide,* or locally accepted references, for procedures to calculate
values such as application rates for various irrigation systems, and to
estimate water holding capacities of soils.

Part of an effective IWM is keeping records of irrigation amount and
timing. Record keeping is required for compliance with a cost-sharing
contract.

**Water Flow Rates and Conversion Factors**