C.A. Odiji; O.M. Aderoju; M.C. Ekwe; D.T. Oje; J.O. Imhanfidon
Abstract
Runoff assessment and estimation is crucial for watershed management as it provides information that is needed to expedite the course of watershed planning and development. The most commonly used model due to its simplicity and versatility in runoff estimation is the soil conservation service curve number ...
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Runoff assessment and estimation is crucial for watershed management as it provides information that is needed to expedite the course of watershed planning and development. The most commonly used model due to its simplicity and versatility in runoff estimation is the soil conservation service curve number developed by the United States Department of Agriculture. The study estimates the surface runoff of Upper Benue watershed using a geospatial based soil conservation service curve number model. Datasets utilized for this purpose are; Rainfall, land use, digitial elevation model and FAO-Soil. The soil and land use data were intersected to create the curve number grid and database. The curve number grid combined with the mean annual rainfall data from 1990 – 2017 was used to estimate runoff. The result revealed that 61.5% of rainfall was direct runoff while 38.5% of the rainfall was retained by tree/plant cover and soil. The average curve number for the normal condition was calculated to be 80.1 while the dry and wet season was 59.6, and 93.2 respectively. The average runoff volume for 27 years was estimated to be 69,887.43mm3. A correlation coefficient of 0.79 was found for the relationship between rainfall and runoff. The research highlights the importance of geospatial technique when integrated with soil conservation service curve number to estimate runoff conditions in Upper Benue Watershed.
M. Eshghizadeh; A. Talebi; M.T. Dastorani; H.R. Azimzadeh
Abstract
Erosion plots were selected for characterizing the effects of main natural factors on runoff and soil loss in a semi-arid region. These erosion plots with an area of 40 m2 are located in the Kakhk experimental watershed in Gonabad County of Khorasan-e Razave Province in the north-eastern Iran. Data acquired ...
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Erosion plots were selected for characterizing the effects of main natural factors on runoff and soil loss in a semi-arid region. These erosion plots with an area of 40 m2 are located in the Kakhk experimental watershed in Gonabad County of Khorasan-e Razave Province in the north-eastern Iran. Data acquired from 2008 to 2015 include slope, aspect, soil texture and land covers (canopy and litter) factors that were selected as main natural factors and it was tried to determine the effects of these factors on runoff and soil loss amount. In the next stage, it was focused on evaluation of the effects of land covers on runoff generation and soil loss in more details. For this purpose, in each class of the mentioned factors, the relationship between land covers and runoff and soil loss was analysed. The maximum of runoff and soil loss were occurred at E site with the amount of 15.6 mm and 140 g/m2 respectively. Results showed that soil loss and runoff have decreased where the amounts of land covers have increased, and the line gradient is steeper for soil loss reduction than runoff generation. The result especially characterized the role of land covers on soil loss. Based on these results land covers have a significant effect on soil loss but this effect is mostly highlighted in the highest and lowest conditions of erosion potential, rather than the medium erosion potential condition. Furthermore, in each plot and event, a dominant factor determines the quantity of the effect of land cover on runoff and soil loss.