Efficiency of Different Irrigation Systems

Project Summary and Aims

This project will investigate the efficiency of different irrigation systems for sustainable management of water and nutrient flows in the Harvey Irrigation District.

Background

Around the world, demand on water resources is increasing and irrigation efficiency is one of the key issues facing irrigation farmers and water managers. Improving irrigation efficiency has many benefits, including both environmental and economic. The benefits include less stress on water resources, reduced losses of water and nutrients to groundwater and surface water resources, improved production and overall profits; and potentially allowing a greater area to be irrigated with a given volume of water.

Irrigation efficiency can be defined in many different ways, with over 30 definitions currently in use. Efficient on-farm irrigation depends on water use, energy use, labour and capital investment, and aspects related to production and profitability. Consequently, there is no single definition that covers all aspect of irrigation efficiency.

Research and Extension Engineers at Kansas State University (Rogers et al. 1997) have discussed the irrigation efficiency from an engineering and conservation perspective , and the most common efficiency terms in use for irrigation systems and how these terms apply to some common irrigation situations are defined as follows:

Water Conveyance Efficiency(E_c):

Ec = 100(Wf/Ws)

where W_f is water delivered to field and W_s is water delivered from source.
Conveyance efficiency is generally a concern for irrigation districts that supply a group of farmers through a system of canals and open ditches.

Water Application Efficiency(E_a):

    Ea = 100 (Wc/Wf)
    

where W_c is water available for use by the crop and W_f is water delivered to the field.
Water application efficiency gives a general sense of how well an irrigation system performs its primary task of getting to the plant roots.

Irrigation Efficiency (E_i):

    Ei = 100 (Wb/Wf)
    

where W_b is water used beneficially and W_f is water delivered to field.
Irrigation efficiency is more broadly defined than water application efficiency in that irrigation water may have more uses than simply satisfying crop water requirements.

Water Distribution Efficiency(E_d):

    Ed = 100 [1- (y/d)]    

where y is the average absolute numerical deviation in depth water stored from average depth stored during the irrigation and d is the average depth of water stored during irrigation.

Distribution Uniformity(U_d):

    Ud = 100 (Lq/Xm)    

where L_q is the average low-quarter depth of water infiltrated (or caught) and X_m is average depth of water infiltrated (or caught).
The distribution uniformity gives an indication of the magnitude of the distribution problem.

Reservoir Storage Efficiency(E_s):

    Es = Vr/Vdr    

where V_r is water taken from the reservoir and V_dr is water delivered to the reservoir.
A reservoir may be a pond, lake, tank, or other storage mechanism. The most common type of reservoir is pond which can be natural or man made.

Overall Irrigation Efficiency(E_o):

    Eo = Es x Ec x Ea

Effective Irrigation Efficiency (E_e):

    Ee = Eo + FR (1-Eo)
    

where FR is the fraction recycled.
The fraction cycled would be any water that is captured leaving the irrigated area and returned to the source without degradation in quality. Tailwater return systems in seepage would be an example of a method to increase the effective efficiency of an irrigation system.

Goal

The goal of this study is to evaluate the irrigation efficiency of the Harvey Irrigation District, Western Australia using a variety of irrigation performance measures: efficiency and uniformity; design and operation of irrigation methods; comparison of irrigation methods, irrigation management (using a water balance model), sustainable irrigation, and irrigation scheduling modelling. It is proposed to address the following aims:

1. To evaluate the irrigation efficiency of different irrigation methods in Harvey irrigation district and recommend the best irrigation method as defined by in term of efficiency and uniformity for this area or in any other subregion.
2. To identify the key drivers for water losses within on-farm irrigation systems and promote better on-farm irrigation system efficiency and irrigation practice.
3. To bring innovation to the irrigation systems and agronomy on-farm in the Harvey water irrigated area that will increase the water use efficiency and agricultural productivity, and reduce ecological impacts such as water and nutrient seepage to the water table, downstream nutrient run-off and soil structural problems.
4. To assess the design and operation of farm irrigation systems in Harvey or other sub-region irrigation districts and establishes the state of knowledge on irrigation efficiency.
5. To develop appropriate methodologies for analyzing social, economic and environmental benefits of improved irrigation and soil management and increased access to non-conventional water resources such as drainage water, stormwater and recycled water for the purpose of irrigation uses.