Télédétection et ressources en eau/Remote sensing and water resources
259
TABLE 7
Parameters and methodology considered to compute CN
SCS-CN Factors
Parameters used for estimation
Method
Field
data
Laboratory
analysis
Emp. formula
and bibliog.
Aerial
photos
Satellite
images
Hydrologic Soil Group
Soil Texture
X
X
Soil Structure
X
Soil Depth
X
Topsoil Sealing susceptibility
X
X
Soil Hydrolog. conductivity
X
X
X
Cover type
Land use and land cover
X
X
X
Management
Cultural practices
X
Hydrologic condition
Vegetation cover
X
X
AMC
Daily rainfall
X
Impervious area
Rockiness
X
X
As a confirmation, we have calculated the soil water balance after Thornthwaite (1948),
assuming an available water capacity of 100 mm, obtaining a surface runoff of 91 mm/year; this
figure can be considered in good agreement with data estimated by the SCS-CN method (95
mm/year for Shiketi and 84 for Emni-Tzellim). In the present case, the CN method has proved to
be an useful tool for runoff estimation.
A future development is the validation of results with a series of ground measurements. After
such a campaign it will be possible to extend the results to other catchments of the Eritrean
highland and to supply watershed management projects with reliable data.
BIBLIOGRAPHY
Colombo, R., Martucci, A., Rodolfi, G., Sarfatti, P., Kahsay, T. and Yohannes, A. 1995. Stima
dell'erosione del suolo nell'alto bacino del fiume Mareb (Eritrea). Atti VII Convegno Nazionale AIT,
Chieri (TO): 349-353.
Fantoli, A. 1966. Contributo alla climatologia dell'altopiano Etiopico - Regione Eritrea. Ministero
degli Affari Esteri-Cooperazione Scientifica e Tecnica, Roma.
FAO/UNEP/UNESCO. 1980. Méthode provisoire pour l’évaluation de la dégradation des sols. FAO,
Rome.
FAO. 1994. Eritrea. Agricultural Sector Review and Project Identification. TCP/ERI/2353, FAO, Rome
(3 Vol.).
Fletcher, R.D. 1950. A Relation between Maximum Observed Point and Areal Rainfall Values. Trans.
Am. Geophys. Union, 31: 344-348
Griffiths, J.F. 1972. Climates of Africa. World Survey of Climatology, vol 10. Edited by J. F. Griffiths.
Elsevier Publishing Company, Amsterdam-London-New York.
259
TABLE 7
Parameters and methodology considered to compute CN
SCS-CN Factors
Parameters used for estimation
Method
Field
data
Laboratory
analysis
Emp. formula
and bibliog.
Aerial
photos
Satellite
images
Hydrologic Soil Group
Soil Texture
X
X
Soil Structure
X
Soil Depth
X
Topsoil Sealing susceptibility
X
X
Soil Hydrolog. conductivity
X
X
X
Cover type
Land use and land cover
X
X
X
Management
Cultural practices
X
Hydrologic condition
Vegetation cover
X
X
AMC
Daily rainfall
X
Impervious area
Rockiness
X
X
As a confirmation, we have calculated the soil water balance after Thornthwaite (1948),
assuming an available water capacity of 100 mm, obtaining a surface runoff of 91 mm/year; this
figure can be considered in good agreement with data estimated by the SCS-CN method (95
mm/year for Shiketi and 84 for Emni-Tzellim). In the present case, the CN method has proved to
be an useful tool for runoff estimation.
A future development is the validation of results with a series of ground measurements. After
such a campaign it will be possible to extend the results to other catchments of the Eritrean
highland and to supply watershed management projects with reliable data.
BIBLIOGRAPHY
Colombo, R., Martucci, A., Rodolfi, G., Sarfatti, P., Kahsay, T. and Yohannes, A. 1995. Stima
dell'erosione del suolo nell'alto bacino del fiume Mareb (Eritrea). Atti VII Convegno Nazionale AIT,
Chieri (TO): 349-353.
Fantoli, A. 1966. Contributo alla climatologia dell'altopiano Etiopico - Regione Eritrea. Ministero
degli Affari Esteri-Cooperazione Scientifica e Tecnica, Roma.
FAO/UNEP/UNESCO. 1980. Méthode provisoire pour l’évaluation de la dégradation des sols. FAO,
Rome.
FAO. 1994. Eritrea. Agricultural Sector Review and Project Identification. TCP/ERI/2353, FAO, Rome
(3 Vol.).
Fletcher, R.D. 1950. A Relation between Maximum Observed Point and Areal Rainfall Values. Trans.
Am. Geophys. Union, 31: 344-348
Griffiths, J.F. 1972. Climates of Africa. World Survey of Climatology, vol 10. Edited by J. F. Griffiths.
Elsevier Publishing Company, Amsterdam-London-New York.