Poster Thèse Bouregreg_Bensalah Najoua

Najoua Bensalah

Description

Poster de thèse publié à l'occasion de la rencontre annuelle de l' European Forest Institute- Mediterranean Regional Office- EFIMED, 2009
Thèse (en français) soutenue en 2008, à l'Université Mohammed V, Faculté des Lettres et Sciences Humaines, Département de Géographie, Rabat, Maroc.
Intitulé " INDICATEURS DES RISQUES DE RUISSELLEMENT ET D’ÉROSION
EN VUE D’UNE GESTION DURABLE DES EAUX ET SOLS(Bassin versant de Bouregreg (S.S), MAROC)

Informations

• Publié par: Bensalah
• Publié le: 30 mars 2012
• Nombre de lectures: 190
• Langue: English

Extrait

I N T R O D U C T I O N

O B J E C T I V E S

Impact of land uses on runoff and erosion risks indicators of the Bouregreg catchment(Morocco) Poster présenté à EFIMED Annual Meeting, Marrakech, 2009

a bc a Najoua BENSALAH, Mohamed SABIR, Eric ROOSE& AbdellahLAOUINA a FLSH : Faculté des Lettres et Sciences Humaines, Université Mohammed V, Rabat, Maroc b ENFI: Ecole Nationale d’Ingénieurs Forestiers, Salé, Maroc c IRD: Institutde Recherche pour le Développement, Montpellier, France

The overexploitation of natural resources becomes an alternative forthe rural people livelihood. The vegetation and land are degraded.The soils are poorly protected, eroded and lose their fertility . Dramatical erodingevents occur. 3 Dams are silted.Morocco loses are annually 75 millionm ofits storage capacity of water. Severalresearchers were interested in the development of methodologies thatcan provide decision makers with effectivetools and easy to use forguiding watershed management.  Understandthe impact of land uses (natural forests, overgrazed matorral, cereal  growing)on the hydrological behaviours of the soils,  Identifyrunoff and erosion risk indicators easily and rapidly measurable,  Explorethe relationship between these indicators and physicochemical  characteristicsof soil.

The watershed of Bouregreg, is equipped with one of the major dams to feed the two major cities, Rabat and Casablanca. The damSidi Mohamed Ben Abdellahproduces 31.5% of drinking water in Morocco.

S T U D Y S I T E

EFFECT OF LAND USES ON SOIL HYDRODYNAMIC PROPERTIES EXPERIMENTATION SITES Effect of land uses on runoff coefficient (Kr %) Using the mapping tool (GIS), the Bouregreg watershed has been 18 representative  Brunifiedsoil (Bf) divided into homogeneous areas according to the soils and land study sites Brown soil (Br) Fersiallitic soil (F) uses.  Sandysoil (S) Quercusnatural forest Ma ofland use in the Bourere catchment (Green oak and cork oak)in soil (F) Fersiallitic  Brunified soil (Bf) Brown soil, brunified soil  Hydromorphicsoil (Hyd) fersialitic soil  Brownsoil (Br) Calsimagnesic soil (Ca)  Isohumicsoil (Is) Overgrazed matorral in  Verticsoil (V) Forest Matorral Cerealgrowing Brown soil, brunified soil fersialitic soil, Effect of land uses on soil detachability (D g/m²/h) calcimagnesic soil  Brunifiedsoil (Bf) Cereal growing in  Brownsoil (Br) Fersiallitic soil (F) Brown soil, brunified soil  Sandysoil (S) fersialitic soil,  Fersialliticsoil (F) calcimagnesic soil,Isohumic  Brunified soil (Bf) soil, hydromorphicSoil, Hydromorphic soil (Hyd) vertic soil,sandy soil Calsimagnesic soil (Ca)  Brownsoil (Br) soil (Is) Isohumic FIELD MEASURMENTS soil (V) Vertic The ra n as mu aon measure parameters are: EFFECT OF LAND USES ON SURFACE FEATURES AND TOPSOILS PROPERTIES The hydrological behaviours Pi :prepounding rainfall (mm), 1 R of soils were studied with a M If :stable infiltration rate (mm/h), Effect of land uses on covered surface (SC %) and opened surface (SO %) rainfallsimulation. E Lr :runoff recoverable after the end of A 2 rain (mm), S SC (%)SO (%) T A simple irrigator (Roose, 1996) Kr :runoff coefficient (%) , U was used to simulate 50mm E D :soil detachability (g/m²/h). rainfalls at 90 mm/h on 1 m² L R The soil surface features have been microplots. T described by “quartile points I 3 repetitions were made bythe 1,66 m method” (Roose,1996): S combination of soil and 3 A SO:opened surface (%) ( clods, stones occupation where a total of L 0,66 m incorporated into the soil and crusts) 54 plots representative of  BrBf FBr Bf F Ca IsV Hyd SCa IsV Hyd S & SC:covered surface (%) (by litter, S various soils and land uses, on stones not incorporated into the soil, Effect of land uses on waterstable macroaggregates at 5 cm depth (MA5 %) 20 to 40 % hillslopes. and weeds); D Bf & Rug :rugosity index(%). I 1:Water tank of 60 liters located Br 4 The soil surface status have been S at 1m above the top the parcel F S M With a valve at the exit for described: C adjusting water intensity; PEN:resistance to penetration (Kg/cm²); F E SS:resistance to shearing stress (Kg/cm²); Bf 2:Metal bars; U Hyd T 3:Ramp wetting 50 cm wide 3 Da:bulk density (g/cm ) at 2, 10 and 30 S Ca connected to the tank by a hose; H cm depth. 4:Canvas plastic covering channel 5Br S Is O runoff; I V 5:Water runoff collected D O S RELATIONSHIP BETWEEN HYDROLOLOGICAL INDICATORS AND TOPSOIL PROPERTIES N Measuring theMeasuring the Taking bulk Principal Component Analysis (PCA) Adjusting the rain Tightness by penetration shearstrength density intensity applyingpaint and Strength with thewith the samples silicone Penetrometer Scissometer The soil hydrological behaviour is mainly governed by its surface features and its texture. The final infiltration is SOIL SAMPLE ANALYSIS negatively correlated to the surface compaction and the silts content and positively to calcareous content. The soil aggregation is positively correlated to the content of silt, clay and (clay + silt) and vegetation cover. The soil detachability is The physicochemical soil properties measured are: strongly positively correlated to thin silt content, total silt and Soil texture( clay (A), silt (L), sand (S), coarsesilt (LG), finesilt (LF), sand plus coarse silt. It is negatively correlated to clay plus silt coarsesand (SG) %); content and to content of waterstable macroaggregates. It is pH; related negatively to the opened surface, the vegetation cover MA5 :(%) for the first 5 cmwaterstable macroaggregates > 0.2 mm and soil bulk density. depth (Kemper et Roseneau modified by par Barthès andal.; 2001); Corg:carbon stocks at 10, 20 and 30 cm depth ( Walkley black ;1934); SOM:soil organic matter (%) at 10, 20 and 30 cm depth (= Corgx1,74). Measuring theMeasuring the soil aggregationcarbon stocks

C ONCLUSION RECOMMANDATIONS The most significants runoff and erosion risks indicators are: This study has confirmed the positive impacts of vegetation, mainly Covered surface (SC) : litter, opened surface (SO), forest vegetation, on the production of water with a high quality to be stored Bulk density (Da) at 2, 10 and 30 cm depths (soil settlement); in dams, on the protection and conservation of soil against water erosion Soil aggregation (MA) and soil texture. and the environmental role that should play watersheds, particularly The relationship betweenrunoff and erosion risks indicators are validated: carbon sequestration in soils. Strengthening the roles of vegetation Hydrological behaviour of soil= f(soil surface features(SC, SO, settlement)); cover is a necessity, through the rehabilitation of existing forests, Soil aggregation = f(Soil texture, organic matter (MO) ). planting new settlements and the encouragement of agroforestry plantation. The crop land are the most land use susceptible to runoff and erosion Overgrazing and overcultivation of sensitive land have to be reduced through (effects of bare soil and export crop residues) a change of existing practices. Selected references Roose E., 1996.Méthodes de mesure des états de surface du sol, de la rugosité et des autres caractéristiques qui peuvent aider au diagnostic de terrain des risques de ruissellement et d’érosion, en particulier sur les versants cultivés des montagnes. IRD, Montpellier, BulletinRéseau Erosion 16: 87 96. Sabir M., Barthès B & Roose E., 2004. Sabir M., 1994.un milieu steppiqueInfluence du pâturage sur l’état de surface et les propriétés hydrologiques d’un sol dans de l’Aarid, haute Moulouya).marocain (périmètreIAV : 161p Thèse du doctorat èsSciences agronomiques, Sabir M., Barthès B & Roose E., 2004.Recherche d’indicateurs des risques de ruissellement et d’érosion sur les principaux sols des montagnes méditerranéennes du Rif occidental (Maroc). Science et changements planétaires /Sécheresse ; vol 15 (1) : 105110. Laboratoire MOST(IRD) UFR:CHAIRE UNESCO–GN BP 64 501 F 34394, Montpellier, France «Gestion de l’environnement et Développement Durable» Tel : [phone], Fax : [phone] Faculté des Lettres et Sciences Humaines, 34394, Montpellier, France, BP 1040, Rabat, Tél. [phone], Fax [phone] Email :[e-mail] Email:laouina enara.ma

Corresponding author :[e-mail]

Département Sol Eau Biodiversité, L’Ecole Nationale Forestière d’Ingénieurs BP 511, Tabriquet, Salé Tél & Fax : [phone] Email : sabirenfianadoo.net.ma