Assessing soil erosion and conservation with various methodologies at different

scales

SymposiumAssessing benefits of SLM-Key for success Rabat 2009

MOROCCAN DESIRE TEAM

Sehoul is located between Oued Bouregreg and Grou

is part of the natural geographic unit " Plateau Central Marocain".

Marginal land with a high rate of poverty and important indicators of

degradation

Land degradation, characterized by high variability and chronic shortage in term of natural resources.

Crop rotation Cereal /

leguminous

Fodder cultivation: e.g. the lupine

Rainfed tree plantation: olive

associated with annual cultivation

Assisted regeneration of cork oak

The assessed approaches

METHODOLOGY

Results

Crop rotation: Cereal / Leguminous

1- Increased soil protection by providing better cover

2- Maintaining and improving soil fertility

Cereal / leguminous rotation vegetation cover reached 65,5%

Cereal / Cereal rotation vegetation cover is < 50 %

3- Improving soil structural stability

0

1

2

3

4

5

6

7

bean/wheat wheat/bean Wheat/chick peas oats / wheat Barley/barley

Compaction Capacity Penetrometr (Kg/cm3)

Mecanic Resistance Torvan (Kg/cm3)

Fig.1: Compaction capacity penetrometr and mecanic resistance torvan in various rotation types

Kg/cm3

Crop rotation (cereal/leguminous): Improves soil resistance to compaction and limits surface crusting.

(%)

-

2,0

4,0

6,0

8,0

10,0

12,0

bean/wheat wheat/bean Wheat/chickpeas

oats / wheat Barley/barley

Fig.2: Moisture conten in various rotation types

4- Soil moisture

The Rainfed fruit tree plantation associated with annual cultivations

1- Protecting the soil surface (vegetation cover)

In the olive grove (15 years), we recorded the most important herbaceous cover (66%). However, the average cover of herbaceous in the rotation Cereal / Cereal does not exceed 52,5%.

2- Improvement of soil fertility and surface characteristics

0

2

4

6

8

10

12

14

olive parcel of 15years

olive parcel of 7 years wheat Barley

Moisture Content (%) organic matter (%)

(%)

Fig.3: Moisture content and Organic matter

Fodder cultivation: (the

lupine)

0102030405060708090

100

Matorral Fallow (10 years) Fallow Lupin

herbaceous Litter bare soil(%)

Fig.11: Soil Cover

Lupin: offers the best vegetation cover

(%)

0,00

0,50

1,00

1,50

2,00

2,50

3,00

3,50

Matorral Fallow (10years)

Lupin Fallow oats Barley

Fig.13: Organic matter

Offers a medium organic matter content in the soil.

Assessment of soil erosion by 137Cs measurements

barley/wheat rotation leguminous/ wheat rotation vine monoculture

barley/wheat rotation

Wheat / leguminous

rotation

Vine monoculture

Mean erosion (tha-1yr-1)

12.5 2 8

Less erosion forwheat /leguminous crop rotation

Medium term assessment of Erosion rates ~50 years

Rainfall simulation technique: Soil loss and runoff coefficient under different land use

 

Novembre 2007 Avril 2008

Coefficient Ruissellement

en %

Taux d'érosion

(g/m²)

Coefficient Ruissellement

en %

Taux d'érosion

(g/m²)

Sol fersialitique

Labour 1,5 2,5 *** ***

Chaume pâturé 8,6 17,6 *** ***

Jachère annuelle *** *** 3,3 1,76

Jachère longue 6 5,8 6,3 2,6

Céréale *** *** 1,7 0,2

Nu très caillouteux *** *** 25 205

Sol Calcimagnésique

Jachère 6,6 24 9 55,4

Parcours *** *** 17,8 37,8

HYDROLOGIC MEASUREMENTS/ THE Hannanat catchement

Water balance in 2008-2009

rainfall 726,7mm

Runoff coefficient : 10%

Follow-up of the vegetation growth and effect on runoff

Variation du couvert végétal au niveau du microbassin Hannanat

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90

14/10/2008 25/10/2008 12/11/2008 11/12/2008 09/01/2009 09/02/2009 17/03/2009 24/04/2009

% c

ou

ve

rt

vé

gé

tal

Céréales

Fève

jachère

Inculte

Vigne

Autumn Winter Spring

Rainy events with important runoff

22 31 1

Rainy events without runoff

14 20 8

Hydrologic behaviour at the experimental micro catchment :

Réponse hydrologique du bassin à l'évènement pluvieux du 1/12/09 (automne)

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Déb

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Déb

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Débit liquide (l/s)

Intensité(mm/h)

Autumn winter

•In autumn: the flood hydrograph shows a quick response. The peak discharges are around several hundreds of liters per second (469 l/S) with a Runoff coefficient up to 54%.

•In winter : rainfall events are longer and complicated compared to the autumnal period. Most of rainfall events shows a runoff coefficient lower than 5%.

The high content of suspended load during the intense rain events

Surface runoff and erosion modelling Our will is to model the Surface runoff, using a

Model (for example the LISEM). This modelling will permit to imagine scenarios of

functioning of the watershed in relation with the global changes expected to be recorded in the area, first the scenario of success of the WSC actions our team is implementing, but also other scenarios of change like climatic change or land use and land cover transformations.

Conclusion

Study of vegetation cover, soil fertility, soil texture and moisture.

Use of 137Cs measurements

Soil loss and runoff coefficient

Crop rotation Cereal /

Leguminous seems to be a good strategy

to use in Sehoul

But there is need for providing fodder

Study of Water balance

Hydrologic behavior

Enable to understand the soil

behaviour at the catchment scale and

to evaluate the global soil loss

Thank you