A Historical Analysis of Rainfall Trend in the Olifants Basin in South Africa

Gyamfi, Charles; Ndambuki, Julius M.; Salim, Ramadhan Wanjala

doi:10.5539/esr.v5n1p129

Cited by 13 publications

(9 citation statements)

References 35 publications

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“…Rainfall is seasonal in the basin, occurring during the months of October to April with appreciable spatio-temporal variability. The mean annual precipitation (MAP) is documented by Gyamfi et al [25] to be 664 mm with peaks in January. Temperatures range from 18 • C to 34 • C in summer and 5 • C to 26 • C in winter.…”

Section: Study Locationmentioning

confidence: 99%

Hydrological Responses to Land Use/Cover Changes in the Olifants Basin, South Africa

Gyamfi

Ndambuki

Salim

2016

Water

107

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This paper discusses the hydrological impacts of land use changes on the Olifants Basin in South Africa using the Soil and Water Assessment Tool (SWAT). A three-phase land use scenario (2000, 2007 and 2013) employing the "fix-changing" method was used to simulate the hydrology of the Olifants Basin. Changes in land uses were related to different hydrological responses through a multi-regression analysis to quantify the effects of land use changes. Results reveal that from 2000 to 2013, a 31.6% decrease in rangeland with concomitant increases in agriculture lands (20.1%), urban areas (10.5%) and forest (0.7%) led to a 46.97% increase in surface runoff generation. Further, urbanization was revealed as the strongest contributor to increases in surface runoff generation, water yield and evapotranspiration (ET). ET was found to be a key water availability determinant as it has a high negative impact on surface runoff and water yield. Urbanization and agriculture were the most essential environmental factors influencing water resources of the basin with ET playing a dominant role. The output of the paper provides a simplistic approach of evaluating the impacts of land use changes on water resources. The tools and methods used are relevant for policy directions on water resources planning and adaptation of strategies.

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Section: Study Locationmentioning

confidence: 99%

Hydrological Responses to Land Use/Cover Changes in the Olifants Basin, South Africa

Gyamfi

Ndambuki

Salim

2016

Water

107

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“…The subcatchment is located within a semi-arid environment and geographically stretches from latitudes 24.43°-25.81° S and longitudes 29.73°-30.66° E. The area is characterized by Inter-Tropical Convergence Zone (ITCZ) with temperatures ranging 5°C -34°C (IWMI, 2008). Rainfall is seasonal in the catchment occurring during the months of October to April with appreciable spatio-temporal variability with coefficient of variation of 24% (Gyamfi et al, 2016). Land uses are documented to include agricultural, urban or built up settlements and grasslands among others (CSIR, 2003).…”

Section: Study Areamentioning

confidence: 99%

Spatial Variability Modeling of Soil Erodibility Index in Relation to Some Soil Properties at Field Scale

Gyamfi¹,

Ndambuki²,

Salim³

2016

ENRR

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Soil erosion is a major land degradation issue affecting various facets of human lives. To curtail soil erosion occurrence requires understanding of soil properties and how they influence soil erosion. To this end, the soil erodibility index which gives an indication of the susceptibility of soils to erosion was examined. In particular, we aimed to determine soil erodibility index at field scale and establish relationships that exist between selected soil properties and soil erodibility index. It was hypothesized that for soil erodibility index to vary spatially, then the existing soil properties should have varying spatial structure. Hundred disturbed and 100 undisturbed soil samples were collected from a 7.3 ha gridded area. The samples were analyzed for particle size distribution, bulk density, particle density, organic matter content and porosity. All soil analyses were conducted following standard procedures. Data were analyzed statistically and geostatistically on the basis of semivariograms. Sandy clay loam was the dominant soil texture in the studied field. Results indicate significant negative relationship between sand content, bulk density, particle density and organic matter with soil erodibility index. Silt correlated significantly with a positive relation with soil erodibility. Estimated erodibility for the sampled field ranged from 0.019 t.ha.hr/ha.MJ.mm to 0.055 t.ha.hr/ha.MJ.mm. The order of dominance of erodibility ranges were 0.038-0.042 t.ha.hr/ha.MJ.mm > 0. 036-0.08 t.ha.hr/ha.MJ.mm > 0.032-0.036 t.ha.hr/ha.MJ.mm > 0.019-0.032 t.ha.hr/ha.MJ.mm > 0.042-0.055 t.ha.hr/ha.MJ.mm . Regression analysis revealed silt to be the most significant variable that influences soil erodibility. The best regression of soil properties on soil erodibility index gave an R 2 of 0.90. A comparison of the regression equation with other studies indicated good performance of the equation developed.

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“…The mean annual rainfall is 630 mm with peaks in January [38]. Rainfall in the basin varies both in space and time with a coefficient of variation of 24% [39]. Temperatures range from 18 °C -34 °C in summer and 5 °C -26 °C in winter.…”

Section: Description Of the Study Locationmentioning

confidence: 99%

Simulation of Sediment Yield in a Semi-Arid River Basin under Changing Land Use: An Integrated Approach of Hydrologic Modelling and Principal Component Analysis

2016

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Abstract:Intensified human activities over the past decades have culminated in the prevalence of dire environmental consequences of sediment yield resulting mainly from land use changes. Understanding the role that land use changes play in the dynamics of sediment yield would greatly enhance decision-making processes related to land use and water resources management. In this study, we investigated the impacts of land use and cover changes on sediment yield dynamics through an integrated approach of hydrologic modelling and principal component analysis (PCA). A three-phase land use scenario (2000, 2007 and 2013) employing the "fix-changing" method was used to simulate the sediment yield of the Olifants Basin. Contributions in the changes in individual land uses to sediment yield were assessed using the component and pattern matrixes of PCA. Our results indicate that sediment yield dynamics in the study area is significantly attributed to the changes in agriculture, urban and forested lands. Changes in agriculture and urban lands were directly proportional to sediment yield dynamics of the Olifants Basin. On the contrary, forested areas had a negative relationship with sediment yield indicating less sediment yield from these areas. The output of this research work provides a simplistic approach of evaluating the impacts of land use changes on sediment yield. The tools and methods used are relevant for policy directions on land and water resources planning and management.

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A Historical Analysis of Rainfall Trend in the Olifants Basin in South Africa

Cited by 13 publications

References 35 publications

Hydrological Responses to Land Use/Cover Changes in the Olifants Basin, South Africa

Hydrological Responses to Land Use/Cover Changes in the Olifants Basin, South Africa

Spatial Variability Modeling of Soil Erodibility Index in Relation to Some Soil Properties at Field Scale

Simulation of Sediment Yield in a Semi-Arid River Basin under Changing Land Use: An Integrated Approach of Hydrologic Modelling and Principal Component Analysis

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