Irrigation Efficiency

We define irrigation efficiency as the ratio between the water stored in the soil depth inhabited with active plant roots to the water applied by the irrigation system. Thus, water applied by the irrigation system and not being made available to be taken up by plant roots is wasted and reduces irrigation efficiency. The major causes for reduced irrigation efficiency are drainage of excess irrigation water to soil layers deeper than the depth of active roots. Leakage of irrigation water to deep soil layers could result in pollution of the water table.

The cases of irrigation efficiency of 100 percent are practically none existent even in the most modern irrigation systems. Major difficulties in obtaining high irrigation efficiency stems from the inability to obtain an accurate estimate of the quantity of water needed to recharge the soil root zone depth and the lack of valid, real time information concerning the actual soil depth of active roots.

Conservative estimates suggest that even under optimal management practices the average irrigation efficiency is estimated to be 70 percent. Thus, the average water loss under sprinkler and drip irrigation is 30 percent but could drop to values of over 50 percent under furrow and flood irrigation. Water losses of irrigation water under urban and landscape irrigation could easily reach 50 percent of the applied water.

When we apply these estimates to irrigation practices in Israel, a yearly saving of 300 to 400 millions metric volumes of irrigation water could be saved as a result of using technologies capable of increasing substantially irrigation efficiencies.

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