Efficiencies in partially closed Irrigation systems

The Egyptian irrigation and drainage network is one of the oldest and most complicatedirrigation systems in the world. The Nile River is the main source of water for the countryproviding it with about 95% of its annual water requirements for various uses. Theavailability of reliable water supplies from Lake Nasser is governed by existing water treatieswith Sudan and other Nile basin countries, under which 55.5 billion cubic meters of water areallocated to Egypt. Due to the increasing demand for water caused by rapidly growingpopulation and fixed water supplies, greater emphasis is now being placed on the need toimprove the efficiency of water in use of the available water resources.A water resource system is closed when there is no usable water leaving the system.Conversely, a water resource system is open when usable water does leave the system. Aclosing system requires mush more management than an open system and this is captured inthe effective efficiency concepts. The key to effective management of water resources inclosing systems is the ability to allocate and reallocate water to accommodate changingdemands and priorities.This study aims to overcome the limitations of the classical irrigation efficiency concept, andto propose a more reliable concept, called effective efficiency. It is defmed as the beneficiallyused water divided by the amount of freshwater consumed for the irrigation process includingthe losses during conveying and applying the water. The volume of water that becomesusable surface runoff or deep percolation is subtracted from the total volume delivered in thisnew concept. This concept is necessary to correctly evaluate the net water losses within theNile river basin or groundwater system in Egypt.By using the mathematical model - to compute the classical efficiency (CE) and effectiveefficiency (EE) - four scenarios have been made to study the influence of the new EE concepton different future water policies in Delta regions. The calculations were based on data fromthe Irrigation Sector, MWRI for five years from 2000/200 I to 2004/2005 for the three Delta.