الري فى مصر(السؤال السادس فى شيت التقاريرالتانى)

ده بحث عن الري فى مصر و هو مطلوب فى الشيت التانى بتاع التقارير

اللى تحت النص بتاعه

و اي خدمة

Irrigation in Egypt and Role of National water Research

Center

IRRIGATION IN EGYPT AND ROLE OF NATIONAL WATER RESEARCH CENTER

1- Introduction

Rainfall is scarce in Egypt, even the small amount which normally occurs over the Delta comes during the winter when crop demands are low. Consequently, the nation’s farmlands are and have been since an immemorial time, almost entirely dependent on irrigation from the Nile River. These farmlands include approximately 6 million feddans of alluvial soil along the Nile and in the Delta, They are so-called “ old lands’’. Some additional land has been and is being reclaimed from the bordering

desert, the tidelands along the northern coast, in Sinai and in south of Egypt, Figure (1).

The last century witnessed a radical change in Egyptian irrigation methods. The ancient system of basin irrigation and cultivation of one crop per year, which prevailed since the dawn of civilization, has been superseded by perennial irrigation. Due to the construction of many control structures, including the High Aswan Dam, water is now available for a year-round crop cultivation.

Perennial irrigation has provided new opportunities for more intensive crop production, but at the same time, it has generated new problems. The use of more water on a relatively fixed area of land has caused waterlogging, buildup of salts in the soil and excessively high water tables in various farming areas.

Management of the delivery and drainage systems has become more difficult under conditions of year-round irrigation and changes in cropping patterns. The challenge is to minimize or solve these problems while fully exploiting the new opportunities for the benefit of the nation.

2- Irrigation systems in Egypt

The High Aswan Dam presently ensures Egypt’s annual quota of 55.5 milliard cubic meters of water for irrigation and other purposes. The discharge of water from the High Aswan Dam is under full control. The release of water for irrigation is adjusted throughout the year to provide all agricultural areas with sufficient water for crops needs. Distributary canal cross sections are designed to serve command areas according to specified water duties. Mesqas (private canals) are served from the distributary canals which are on a two or three – turn rotation. The time interval between the periods when water is turned off and when it is later turned on depends on the cropping patterns and the seasonal climatic conditions.

The on – days of a canal rotation are considered 24 hour periods (starting at sundown) without any adjustments between daytime and nightime use. The number of on-days in a turn is sometimes modified

CIHEAM -

The water supply for any given area is monitored by observing water surface levels in delivery canals. The water is typically delivered from 50 to 75 cm below the ground surface of the fields, so irrigators must lift the water onto the land. Delivery canals are closed for approximately one month during the winter to permit maintenance and construction of structures. In general, the winter closure is preceded and followed by a general irrigation for ten days.

Farmers are not required to pay for water. Its use along the mesqa is determined by custom, which usually favors the farmers at the head of the mesqa. Similarly, mesqas at the head of a distributary canal have an advantage over those at the tail end.

After lifting water from the mesqa, a farmer is free to distribute over his fields by his own methods. Generally, he distributes the water through a marwa ( filed ditch) to small bunded units called basins. The surface of the fields may be furrowed for row crops or smoothed for basin crops. Excess surface water may be drained – off into open field drains or, in some cases, back into the mesqa.

The best environment for crop production is achieved when the plants’ root zones are kept adequately moist. Either inadequate or excess water in the root zone causes plant stress and reduces yields. Good irrigation management should maintain optimum root zone moisture conditions without using excessive water. Poor irrigation management wastes water, sometimes wastes plant nutrients, contributes to potentially harmful high water table conditions, and tends to overload drains. It may also waste labor and energy required for lifting excess water to the fields and from the drains.

Good on-farm water management requires levelled fields, appropriately designed on-farm distribution systems, and knowledge of when to irrigate and how much water to apply. It also requires a dependable source of water, available when needed, in quantity and quality which can be distributed efficiently over the farmer’s field. Consequently, there must be close communication and interaction among all farmers served by a mesqa and with the districeirrigation engineer who regulates the water, upstream from the mesqa intakes.

The potential for achieving benefits from better water management is substantial. Approximately half of the water resources available are presently required for evapotranspiration by crops. Of the remainder, most is lost from the system in the delivery process through seepage, evaporation, and flow –through. Some , of course, must be allocated for domestic, industrial and navigation uses. Any measure which conserves water and reduces losses provides an opportunity for increased agricultural production through horizontal expansion as well as reducing drainage costs.

3 - Irrigation Practices

3.1 - Traditional System

Egyptian farmers have traditionally irrigated by dividing their field into small basins of not more than 10m x 10m served by a within-field marwa. These basins provided the farmer with fairly good water control and allowed application of fairly uniform amounts of water even when fields were somewhat unlevelled. The small basins with internal marwas also allowed surface drainage when the soil sealed. However, these basins hindered mechanization, particularly operations of large four-wheel type tractors commonly used in Egypt.

The lifting of water at the farm level was usually done by animal-powered saqias, hand-operated tambours and increasingly by diesel-powered pumps.

The farmers frequently had prolonged “irrigation gaps” between the last irrigation of one crop and the first irrigation of the next. The duration of the irrigation gaps depended on the two crops involved. Even though these irrigation gaps were prolonged, the individual crops received appropriate final and initial irrigations when viewed separately. The irrigation gaps represented periods of general decline in the irrigation demand, even though crop consumptive use and potential evapotranspiration remained relatively high. When large volumes of water are released during these periods, much of the water flowed through the system was discharged directly from mesqas into the drains. Irrigation planning,therefore, had to be based on the entire cropping pattern rather than individual crops.

4. The Distribution of Waters

The system of water distribution from the High Dam lake to meet the water requirements through out the year for different agricultures, in old and reclaimed lands is not as easy as someone expects. It is a matter of high sophistication in which many integrated and joint factors participate due to the varying soil characteristics, whether natural or chemical, weather conditions, crop water requirements in fluctuation levels, irrigation system used, method of cultivation , and the difference in groundwater levels, in addition to the natural , ecological, social and other aspects.

This can not be performed except through the management and operation of a great number of structures to ensure the control and the distribution of water according to the actual water requirements throughout the country.

4.1 Characteristics of the water Delivery system

The Nile River is the main source of Irrigation water in Egypt . This water is delivered to farms through an extensive system of channels. The delivery system, which contains some large canals discharging up to 1000m3/sec, has a combined length of 30,300 km. Canals are classified according to size and functions as follows :

1 Principal canals receive water directly from the Nile River for conveyance to main canals. No direct irrigation from these canals is permitted.

2 Main canals receive water from principal canals for conveyance to branch canals. ( Some main canals may take water directly from the Nile River ). No direct irrigation from main canals is permitted.

3 Branch canals receive water from the main canals for conveyance to Distributary canals. Direct irrigation is permitted along the lower reaches of these canals, where they are comparable in size to a Distributary canal.

4 Distributary canals receive water from branch canals for distribution to mesqas. Direct irrigation along all distributary canal banks is permitted through legal farm outlets. Rotations are normally applied at this level.

5 Private ditches ( mesqas ) receive water from Distributary canals for distribution to marwas or directly to basins and / or furrows on private farms.

To control the proportional distribution of water to the canals, seven main barrages have been built on the Nile River. These main control structures are at Aswan, Esna, Nagga Hammadi, Asyut, Delta, Zifta and Edfina. Additional structures in the delivery system include:

Type of structure Number

Intake regulators 5623

Head regulators 2887

Weirs 162

Tail Escapes 1761

Spillways 153

Bridges 9955

Crossing Works 567

4.2 Drainage system

Public drains in Egypt comprise a system of large open channels having a combined length of 17,497 km. Private drains consisting of small open channels for removal of excess surface water and / or closed tile drains for removal of ground water, convey water to the larger drains. Drains are classified according to function and size as follows:

a) Principal drains receive water from main drains mainly by lifting (sometimes by gravity).

b) Main drains receive water from branch drains mainly by gravity (sometimes by lifting).

c) Branch drains receive water from collector drains.

d) Collector drains receive water from field drains.

CIHEAM - Options Mediterraneennes

e) Field drains are either small open channels, zawariq, for drainage of surface water from farms, or subsurface tile drains, sometimes called laterals , for drainage of groundwater.

f) Principal, main, and branch drains are public drains constructed and maintained by the MPWWR while, collector and field drains are private drains constructed and maintained by farmers.

شكرا جدا يابشمهندس على المشاركة الفعالة والرائعة جدا جدا

ويثبت الموضوع

لاشكر على واجب لأن ده منتدانا و دى دفعتنا و لازم نشارك باللى نقدر عليه

شكرا يا بشمهندس على المجهود .
والى الامام..

شكرا يا باش مهندس جون على المعلومات الهامه دى

ينقل لسله المحذوفات لتمام الانتفاع به

» السؤال للبنات والاولاد
» ويبقى السؤال
» اجب عن السؤال الآتي؟؟‎
» ملخص اليوم السادس
» أكاديمية الدور السادس !!