irrigation water saving by management of existing subsurface drainage in egypt

IRRIGATION AND DRAINAGE

Irrig. and Drain. 54: 205–215 (2005)

Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ird.164

IRRIGATION WATER SAVING BY MANAGEMENT OF EXISTINGSUBSURFACE DRAINAGE IN EGYPTy

M. A. S. WAHBA,1 E. W. CHRISTEN2 AND M. H. AMER1*1 Drainage Research Institute, National Water Research Centre, Egypt

2 CSIRO Land and Water, Griffith, NSW, 2680, Australia

ABSTRACT

Egypt is faced with a water scarcity situation due to increasing demands on a fixed resource which could limit the

country’s ability to further its overall economic development. There is a danger that farmers in the Nile Valley and

Delta may receive less irrigation water and of lower average quality in the future if no actions are taken towards

irrigation water saving.

In Egypt more than 2 million ha have a subsurface drainage system. These systems have been designed with

fixed drain depths and spacings to meet certain strict drainage criteria based on conservative design assumptions

regarding crop type and rooting depth. However, over the life of a drainage system under different conditions of

crop type, crop growth stages and water availability occur. The original design assumptions only occur for short

periods and so for most of the time excessive drainage occurs. Approximately 7.2 BCM of water is drained from

areas with subsurface drainage systems in Egypt.

A new perspective for managing these systems as a key part of integrated water resources management is needed.

For that reason newmanagement concepts for existing subsurface drainage systems have been developed to improve

irrigation water use efficiency. The management concepts were to change the effective drain spacing and effective

drain depth by applying simple, easily adoptablemanagement measures. These management options were compared

with the conventional ‘‘no management’’ by applying the DRAINMOD-S model to the Western Delta of Egypt.

The results indicate that by using the proposedmanagement concepts it is possible to improve the existing irrigation

water use efficiency by 15–20% without any yield reduction. Overall it was found that about 0.4BCM of irrigation

water may be saved in theWestern Delta of Egypt alone by application of these management concepts. Copyright#2005 John Wiley & Sons, Ltd.

key words: subsurface drainage system; controlled drainage; water table management; irrigation water use efficiency

RESUME

L’Egypte est en face d’un probleme de manque d’eau par des demandes croissantes d’une source fixe qui pourrait

limiter les competences du pays pour le developpement de l’economie. Il y a un danger que les fermiers dans la

Vallee du Nil et dans le Delta peuvent recevoir moins d’eau d’irrigation et d’une qualite moyenne degradee si on ne

prend pas de mesures pour sauver l’eau d’irrigation.

En Egypte il y a plus de 2 millions d’hectares qui ont un systeme de drainage souterrain. Ces systemes ont ete

dessines avec une profondeur et une espace fixee, pour repondre a certains criteres d’irrigation bases sur le type

d’agriculture et la profondeur des racines des plantes dans la terre. Cependant, durant la vie d’un systeme de

drainage on voit des conditions differentes d’agriculture, de stade de croissance et de disponibilite d’eau. Les

assomptions des dessins originaux sont seulement pour des periodes courtes, ainsi pour la plupart du temps il y a

Received 1 June 2004

Revised 2 January 2005

Copyright # 2005 John Wiley & Sons, Ltd. Accepted 9 January 2005

*Correspondence to: Dr Mohamed H. Amer, ENCID, Coastal Protection Building, Fum Ismalia Canal, Shoubra El-Kheima, Egypt.E-mail: [email protected]’economie de l’eau d’irrigation par la gestion de drainage sousterrain existante en Egypte.

beaucoup de problemes avec le drainage excessif. En Egypte on draine environ 7.2 BCM d’eau des regions avec

des systemes souterrains.

Il faut une nouvelle perspective sur le traitement de ces systemes comme une role cle de la gestion des ressources

en eau et qu’il y ait de nouvelles idees pour utiliser plus effectivement les systemes de drainage existants. C’est

pourquoi que les idees nouvelles pour les systemes de drainage souterrain ont ete developpees pour ameliorer

l’efficacite de l’utilisation d’eau d’irrigation. Les concepts de gestion sont pour changer les profondeurs et les

espaces de drainage effectif par appliquer de nouvelles mesures de gestion des eaux, facilement acceptees.

Ces idees de gestion des eaux ont ete comparees au ‘pas de gestion’ conventionnel en appliquant le modele

DRAINMOD-S a l’ouest du Delta. Les resultats indiquent qu’on peut augmenter l’efficacite de l’usage de l’eau

par les concepts proposes avec 15–20% sans de la diminution de recoltes. On a trouve qu’on peut sauver 0.4 BCM

de l’eau d’irrigation sur l’ouest du Delta seulement en appliquant ces nouvelles idees de gestion des eaux.

Copyright # 2005 John Wiley & Sons, Ltd.

mots cles: des systemes de drainage souterrains; le drainage controle; la gestion de la surface de la nappe phreatique; l’efficacite de l’usagede l’eau d’irrigation

INTRODUCTION

Egypt is faced with water scarcity due to increasing demands set against a fixed supply of the resource. There is a

danger that farmers in the Nile Valley and Delta may receive less irrigation water and of lower average quality in

the future if no actions are taken to save irrigation water (Fahmy et al., 2002).

The future of water resources in Egypt necessitates the optimization of each drop of water. The nation has thus

set its water policy on this basis and has actually started to implement several irrigation improvement and water

recycling projects (Abu-Zeid, 1994).

Drainage is required in many irrigated arid lands to prevent rise of the groundwater table, waterlogging, and

salinity build-up in the soil. In Egypt the total area covered by subsurface drainage systems will reach some 2.4

million ha in 2005, and it is estimated that after this date another 0.3 million ha in the new reclamation areas will

require subsurface drainage (Abdel-Aziz, 1997). These systems have been designed with fixed drain depths and

spacings to specific criteria that only occur over short periods, or during a reclamation phase. This results in

groundwater tables being drawn down to a greater depth than is actually required to maintain crop production. This

removes water from the soil profile that would otherwise have been used by the crop. This effect is often called

‘‘over-drainage’’. There is an optimum depth to the groundwater table for most crops, above which the crop is

affected by waterlogging and below which the soil is overdry.

In line with these views, this paper explores how the drainage system in Egypt could be managed to make

irrigation practices more efficient by holding water in the profile for plant use. Currently, subsurface drainage

makes irrigation less efficient by quickly removing water from the profile before the plant has an opportunity to use

water from the shallow groundwater.

Irrigation and drainage systems should be managed as an integrated water management system to conserve

irrigation water and reduce drainage volumes (Christen and Ayars, 2001). Recent research recommends modi-

fication in current drainage design criteria in arid areas (drain depths and spacing) to preserve water quality, reduce

drainage volume and reduce the volume of irrigation water required (Grismer, 1993; Ayars et al., 1997; Christen

and Skehan, 2001).

Abu-Zeid (1992) recommended the investigation of controlled drainage as a measure to maximize the

contribution of the water table to crop evapotranspiration and drainage water quality conservation, while meeting

drainage requirements. Also he recommended the implementation of an integrated package of irrigation, water table

and salinity management practices to achieve effective control of soil-water and salinity when controlled drainage is

used. He has also encouraged the researchers in the arid and semi-arid zone to carry out field studies in this direction,

taking into account the response of crops to drought conditions and salinity during the different stages of growth.

A shift towards an integrated approach to drainage provides a major technical and professional challenge. The

physical design and operation of many drainage systems have a long-standing bias towards agricultural productivity.

The challenge is to include topics like controlled drainage, flood management, management of effluent quality, and

drainage water reuse in the design and operation of multipurpose drainage (Abdel-Dayem et al., 2004).

206 M. A. S. WAHBA ET AL.

Copyright # 2005 John Wiley & Sons, Ltd. Irrig. and Drain. 54: 205–215 (2005)

GOALS OF THE PAPER

In Egypt more than 2 million ha of agricultural land are covered by intensive subsurface drainage systems. These

systems have positive impacts in controlling waterlogging and soil salinity, but need to be managed properly. If we

consider the design daily drainage rate is 2mmd�1 and this occurs for 180 days of the year, the total drainage water

from all these drained areas will be about 7.2 BCMyr�1. This provides a large opportunity for more irrigation

water saving by proper management of these existing systems.

For that reason, the goals of this paper are to develop and evaluate new concepts of management for existing

subsurface drainage systems to save irrigation water, while maintaining crop yield. The concepts must be simple,

easily understood by farmers, stakeholders and managers and be applicable under different conditions.

EXISTING SUBSURFACE DRAINAGE SYSTEMS IN EGYPT

Large-scale drainage activities in Egypt started in 1970 with a World Bank loan for the first Nile drainage project.

The Egyptian Public Authority for Drainage Projects (EPADP) was established in 1973 to implement all drainage

projects in the Nile valley and delta (Abdel-Aziz, 1997). The subsurface drainage systems consist of lateral pipes,

connected to collector pipes that outfall into surface drains. After the construction of subsurface drainage systems,

no formal management is implemented and the systems are left to flow continuously. Sometimes farmers try to

control the amount of drainage by blocking drains. These actions are informal, untested and jeopardize the overall

functioning of the system. Simple, easy-to-implement measures are required so that farmers can implement with

known results that do not affect long-term productivity.

SUBSURFACE DRAINAGE MANAGEMENT CONCEPTS

The design of subsurface drainage aims to find the best spacing between drains and the depth of drains which

maintains the water table at a suitable depth for crop root development based on soil properties, irrigation data and

crop types. After the system is implemented the drain spacing and depth cannot be changed, even though the

system parameters such as crop type, crop root development, weather, quantity and quality of irrigation water, and

available water resources are constantly changing.

The management concepts developed for Egyptian conditions are based on controlling the water table by

managing the effective spacing and effective depth during specific stages of the growing season. In this way it is

possible to make the subsurface drainage a dynamic system to match the dynamic crop production parameters.

A flow chart of the subsurface drainage management concepts is shown in Figure 1 and a description of the

concepts follows.

Changing the effective drain spacing

Changing of the effective drain spacing depends on doubling the effective drain spacing from L to 2L during the

crop growing season. This can easily be applied by blocking alternate drains; when the blockage is removed the

effective spacing returns to the original L. This management can be applied to the whole season or in two stages as

follows.

Stage 1z. Change the effective drain spacing from L to 2 L (Figure 2a).

How: Close alternate drains.

Time of application: Beginning of the growing season to about halfway through the season.

Applied irrigation water: X% reduction of irrigation water (suggested reduction by 5–20% depending on

prevailing condition and testing).

zThis stage can be applied for one irrigation event, part of the growing season, or for the whole season, depending on prevailing conditions.

WATER SAVING BY MANAGEMENT OF SUBSURFACE DRAINAGE 207


Figure

1.Flow

chartforsubsurfacedrainagesystem

managem

entconcepts



Stage 2. Return the effective drain spacing from 2L to L (Figure 2b).

How: Unblock the drains.

Time of application: End of stage 1 to the end of the growing season.

Applied irrigation water: Standard irrigation.

Changing effective drain depth

Changing of the effective drain depth depends on controlling the water table depth during the cropping season.

This can easily be applied by using a weir across a sump or riser on a drain. This management can be applied for the

whole season or in two stages as follows.

Stage 1§. Controlling water table depth (Figure 3a).

How: By using weirs or risers at depth 60 or 70 or 80 cm below ground level.

Time of application: Beginning of the growing season to Y% of the growing season.

Applied irrigation water: X% reduction of irrigation water (suggested reduction by 5–20%, depending on

prevailing conditions and testing).

Stage 2. Allow free drainage to the design drainage depth d (Figure 3b)

How: By adjusting/removing the control device.

Time of application: End of stage 1 to end of the growing season.

Applied irrigation water: Standard irrigation.

Figure 2. (a) Stage 1 of changing drain spacing management; (b) Stage 2 of changing drain spacing management

§This stage can be applied for one irrigation event, part of the growing season, or the whole season, depending on the prevailing conditions.



APPLICATION OF THE SUBSURFACE DRAINAGE MANAGEMENT CONCEPTS

The groundwater table management simulation model, DRAINMOD-S, was used to evaluate the management

concepts described above. The model was tested using field data from Maruit experimental station in the Western

Delta of Egypt for three cropping seasons; maize 1999, wheat 1999/2000 and maize 2000. Two groundwater table

managements (conventional drainage and controlled drainage) were applied in the study area. The recorded data

included daily groundwater table depth, drain outflows during flow events, soil salinity to depth of 1.20m from the

soil surface (0.30m interval), and relative crop yield for each applied crop. The reliability of the model was

evaluated by comparing measured and predicted values of daily groundwater table depth, cumulative outflow

based on total monthly outflow, soil salinity during each season, and relative crop yield.

Good agreement was found between the measured and predicted data. The model showed the potential for long-

term simulation and planning of groundwater table management under semi-arid conditions of the Western Delta

of Egypt (Wahba et al., 2002).

Five scenarios for subsurface drainage management have been developed as options to manage the existing

drainage systems (Table I).

The DRAINMOD-S model was used to simulate these scenarios for 10 years under the same conditions as the

experimental field using a crop rotation of wheat, maize, barseem (alfalfa) and cotton, which is the most common

crop rotation in the Nile Delta. Crop yield was considered as the most practical measure of crop response to water

stresses for the purpose of optimizing the water management system. Thus, the selected scenarios were evaluated

by water use efficiency in terms of crop yield (gmm�1) and how much irrigation water was used.

The relative crop yield predicted by the DRAINMOD-S is given by the following equation:

RY ¼ RY�w RY�

d RY�p RYs ð1Þ

Figure 3. (a) Stage 1 of changing the water control depth management; (b) Stage 2 of changing the water control depth management



where

RY¼overall relative yield for a given season

RYw¼ relative yield that would be obtained if only wet or excessive water stresses occurred

RYd¼ relative yield that would be obtained if only drought stresses occurred

RYp¼ relative yield that would be obtained if the only stresses are due to planting delays

RYs¼ relative yield resulting from the soil salinity.

The relative yield may be expressed as

RY ¼ Y=Y0 ð2Þwhere

Y¼measured or observed yield for a given season

Y0¼ long-term average yield that would result from an ideal circumstance.

The predicted yield will be calculated from Equation (2) using the data of the predicted relative yield

from the output of the simulation and the average crop yield for the applied crops in the study area. The

crop yield per m3 will be calculated using the values of predicted yield and the amount of irrigation water

used.

RESULTS AND DISCUSSION

Water use efficiency

The results of the long-term simulation (10 years) for wheat are shown in Figure 4. This shows that the average

water use (gmm�1) for wheat was lowest with conventional irrigation and drainage at about 1.35 gmm�1. The

highest water use was obtained with DCPþ SCF and DCP scenarios, which was about 1.6 gmm�1, and a 16%

increase on the conventional. The other scenarios had a value of 1.53 gmm�1. The increased production per unit

water did not result in any overall yield reduction in any of the scenarios.

The water use for the maize crop for all scenarios is shown in Figure 5. The lowest water use efficiency obtained

was also with the conventional scenario, which was about 1.16 gmm�1, and the highest value was about

1.51 gmm�1 with the DCP scenario, an increase of about 23%. The average relative yield for maize over the

10 years was 94% with conventional, and ranged from 98 to 100% for the other scenarios. This shows that not only

can the productivity per unit of water be increased but also the overall yield per unit land area.

Table I. Scenarios of management concept options

Scenarios Timing Management Drain Drain Control Applied irrigationtype spacing (m) depth (m) depth (m) water (%)

ES Full season None 30 1.15 1.15 100SCF Full season Spacing control 60 1.15 1.15 85DCF Full season Depth control 30 1.15 0.6 80DCP Part season Depth control 30 1.15 0.6 85

Part season Free drainage 30 1.15 1.15 85DCPþ SCF Part season Depth/spacing control 60 1.15 0.6 80

Part season Spacing control 60 1.15 1.15 80

ES: Existing drainage system; SCF: Spacing control, full season; SCP: Spacing control, part season; DCP: Depth control, part season; DCF:Depth control, full season.



The water use efficiency for barseem (alfalfa) by all scenarios is shown in Figure 6. The lowest water use

efficiency again was the conventional at about 12.1 gmm�1, and the highest value was about 14.3 gmm�1 with

the DCPþ SCF scenario, an increase of about 15%. Again the relative yield was unchanged, indicating that water

use efficiency can be increased while still maintaining high levels of production.

The water use efficiency for cotton is shown in Figure 7. The lowest water use efficiency was the conventional at

about 0.35 gmm�1. The highest value was about 0.44 gmm�1, indicating a 20% increase in yield per unit water

applied.

From the above results it is clear that the water use efficiency is improved by subsurface drainage man-

agement concepts coupled with reduced irrigation without affecting production. The results show that water

Figure 4. Average wheat water use efficiency

Figure 5. Average maize water use efficiency



can be saved, and can be used elsewhere, while production can be maintained and even increased in existing

areas.

POTENTIALWATER SAVING WITH THE CONCEPTS IN EGYPT

The average irrigation water used for each crop during the 10-year simulation is given in Table II. All the crops

used less irrigation water with the management scenarios compared to the conventional irrigation and drainage

management. The results indicate that it is possible to save about 577–770m3 ha�1 for wheat, 1071–1280m3 ha�1

Figure 6. Average alfalfa water use efficiency

Figure 7. Average cotton water use efficiency



for maize, 455–603m3 ha�1 for alfalfa and 1117–1476m3 ha�1 for cotton with the proposed management

concepts.

The total area which is covered with the subsurface drainage system is expected to reach 2.5 million ha by the

year 2007. For analysis we have taken only the Western Delta area as representative of the experimental area on

which the model calibration is based. The area covered by subsurface drainage in the Western Delta is

approximately 0.4 million ha (Figure 8). The results of the drainage management scenarios were applied for

the Western Delta area, with the assumption that the crops grown have the same distribution as the national

average. The analysis shows that over a two-year rotation the water saving is considerable, ranging from 62 million

m3 with cotton to 132 million m3 for maize (Table III). In total the water saving could be in the order of 379 million

m3 over a two-year crop rotation.

Table III. Analysis of controlled drainage water savings for Western Delta area

Crop Crop intensity applied to Potential irrigation water Total saving for WesternWestern Delta (%)* saving per crop (m3 ha�1) Delta area (Mm3)

Barseem (Alfalfa) 40 529 85Wheat 37 674 100Maize 28 1178 132Cotton 12 1297 62

Total potential water saving 379

*Derived from data in Egyptian National Agricultural Library (2001).

Table II. Average water use and total water saving for all scenarios (m3 ha�1)

Crop ES SCF DCF DCP DCP/SCF

Wheat 4778 4201 4008 4201 4008Maize 6406 5433 5126 5433 5126Barseem (alfalfa) 3947 3492 3340 3492 3340Cotton 7394 6277 5918 6277 5918

Total irrigation water — 3122 4133 3122 4133saving during the two seasons

Cairo

Mediterranean SeaMediterranean Sea

Alexandria

IsmailiyaZagazigShibin el Kom

Tanta

El MansuraDamanhur

Lake Burullus

Lake Manzala

Proposed Area

Figure 8. Proposed areas of subsurface drainage system in Western Delta of Egypt



CONCLUSIONS

When controlled drainage is implemented irrigation volumes can be reduced, without sacrificing yields.

Application of controlled drainage has the potential to maintain and even increase yields per unit land while

increasing the irrigation water use efficiency (yield per unit water) by 15–20%.

When the potential on-farm water savings by using controlled drainage are applied to large areas then the

potential for water saving in Egypt is large. For the Western Delta area of about 0.4 million ha this could amount to

about 0.4 BCM over a two-year rotation. These water savings can then allow an increase in cropping intensity or

irrigation of new lands.

Implementation of subsurface drainage management such as the low-cost and easily understood options

described in this paper need to be undertaken as part of an integrated approach to water saving. When controlled

drainage is implemented then appropriate reductions in irrigation application needs to occur. This will require

coordination and training between irrigation authorities, drainage authorities and farmers.

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irrigation water saving by management of existing subsurface drainage in egypt

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