Responses of soil crusting, runoff and erosion to fallowing in the sub-humid and semi-arid regions of West Africa

Valentin, Christian; Rajot, Jean-Louis; Mitja, Danielle

doi:10.1016/j.agee.2004.01.035

Cited by 81 publications

(56 citation statements)

References 34 publications

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“…These processes have been proposed as an explanation for the observed changes in Niamey's hydrograph. In Sahel, runoff is mainly controlled by surface conditions (Collinet et Valentin, 1979;Albergel et al, 1987;Cazenave et Valentin, 1992), which have been changing under climatic (Hiernaux and Le Houérou, 2006;Leblanc et al, 2008) and anthropic pressure -wood harvesting (Peltier et al, 1995;Leblanc et al, 2008) or crop extension (Valentin et al, 2004). Several authors (Amani and Nguetora, 2002;Mahé et al, 2003;Leblanc et al, 2008;Amogu et al, 2010;Descroix et al, 2009Descroix et al, , 2012Descroix et al, , 2013 have highlighted that hydrological changes in Niamey hydrograph could be triggered by the land use-land cover (LULC) changes (and the resulting runoff increase) that have occurred since the 1970s in the three main tributaries of the Niger responsible for the red flood in Niamey (the Gorouol, Dargol and Sirba rivers).…”

Section: Introductionmentioning

confidence: 99%

Model-based study of the role of rainfall and land use–land cover in the changes in the occurrence and intensity of Niger red floods in Niamey between 1953 and 2012

Cassé

Gosset

Vischel

et al. 2016

Hydrol. Earth Syst. Sci.

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Abstract. Since 1950, the Niger River basin has gone through three main climatic periods: a wet period (1950)(1951)(1952)(1953)(1954)(1955)(1956)(1957)(1958)(1959)(1960), an extended drought (1970)(1971)(1972)(1973)(1974)(1975)(1976)(1977)(1978)(1979)(1980) and since 1990 a recent partial recovery of annual rainfall. Hydrological changes co-occur with these rainfall fluctuations. In most of the basin, the rainfall deficit caused an enhanced discharge deficit, but in the Sahelian region the runoff increased despite the rainfall deficit. Since 2000 the Sahelian part of the Niger has been hit by an increase of flood hazards during the so-called red flood period. In Niamey city, the highest river levels and the longest flooded period ever recorded occurred in 2003, 2010, 2012 and 2013, with heavy casualties and property damage. The reasons for these changes, and the relative role of climate versus land use-land cover (LULC) changes are still debated and are investigated in this paper. The evolution of the Niger red flood in Niamey from 1950 to 2012 is analysed based on long-term records of rainfall (three data sets based on in situ and/or satellite data) and discharge, and a hydrological model. The model is first run with the present LULC conditions in order to analyse solely the effect of rainfall variability. The impact of LULC and drainage area modification is investigated in a second step. The simulations based on the current surface conditions are able to reproduce the observed trend in the red flood occurrence and intensity since the 1980s. This has been verified with three independent rainfall data sets and implies that rainfall variability is the main driver for the red flood intensification observed over the last 30 years. The simulation results since 1953 have revealed that LULC and drainage area changes need to be invoked to explain the changes over a 60-year period.

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Section: Introductionmentioning

confidence: 99%

Model-based study of the role of rainfall and land use–land cover in the changes in the occurrence and intensity of Niger red floods in Niamey between 1953 and 2012

Cassé

Gosset

Vischel

et al. 2016

Hydrol. Earth Syst. Sci.

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“…In West Africa, both field-based studies and hydrological modelling has been used to assess impacts of land use changes on hydrology at various scales [14,17,[23][24][25][26][27]. However, in the rainforest regions of the south, where the majority of West African population live, there remains a lack of knowledge on the hydrological impacts of land use changes at the local scale, despite land use changes being significant over the past three decades [1,28].…”

Section: Introductionmentioning

confidence: 99%

Assessing Impacts of Land Use Changes on the Hydrology of a Lowland Rainforest Catchment in Ghana, West Africa

Aduah

Jewitt

Toucher

2017

Water

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Impact assessments of actual and potential land use (LU) changes on hydrology are vital in land use planning, which is a prerequisite for effective water resources management. In this study, impacts of actual, as well as potential, LU changes on the hydrology of the Bonsa catchment (1482 km 2 ), Ghana, West Africa, were assessed using the Agricultural Catchments Research Unit (ACRU) hydrological model. Baseline, current and potential future LU maps for three scenarios, namely, business-as-usual (BAU), economic growth (EG) and economic growth and reforestation (EGR), driven by observed climate between 1990 and 2009, were used for the study. The results indicate that peak and dry season streamflows between 1991 and 2011 have increased by 21% and 37%, respectively, under the current land use in comparison to the baseline due to a decrease in evergreen and secondary forests by 18% and 39%, respectively, and an increase in settlements, mining areas and shrubs/farms by 81%, 310% and 343%, respectively. The potential future LU scenarios suggest that there may be further increases in streamflows, but the historical land use changes between 1991 and 2011 were so substantial that they will continue to impact streamflow changes in any of the future land use scenarios. The study also showed that variability of streamflow changes at the catchment scale was lower than at the subcatchment scale. For the scenarios of potential future LU changes, the BAU shows the highest increases in streamflows, while the EGR shows the least. Policy interventions for effective management of the catchment are recommended.

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“…Improved fallows have been demonstrated to improve crop production in subsequent years (Buresh and Tian 1997;Mafongoya and Dzowela 1999) as well as improving a number of other beneficial factors and processes in an agroecosystem such as erosion control (Valentin et al 2005), control of pests such as striga [Striga hermonthica (Del. ) Benth.]…”

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confidence: 99%

Modelling of planted legume fallows in Western Kenya using WaNuLCAS. (I) Model calibration and validation

Walker

Mutuo²,

Noordwijk³

et al. 2007

Agroforest Syst

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Poor soil fertility is the biggest obstacle to agricultural productivity in Sub-Saharan Africa. Improved fallows can help to raise agricultural productivity in these systems of low financial capital, however, experimental testing of their potential application domain and design is costly and time consuming. Models can evaluate alternative systems relatively quickly and at relatively low cost, but must first be validated to assess satisfactory simulation of the target systems. Specific climatic, edaphic, crop and fallow growth data was used from five sites in Western Kenya to calibrate and validate simulations of maize and improved fallow growth using the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model. The model predicted continuous maize yields across the sites with an R 2 of 0.72, an EF (model efficiency) of 0.66 and a CD (coefficient of determination) of 2.73, although the default pedotransfer functions (PTF) for volumetric soil water content used in the model had to be substituted for a tropical soils specific PTF before this was achieved. Predicted maize yield was consistently related to fallow biomass (i.e. higher fallow biomass correlated with higher subsequent maize yields) at two sites and the model predicted maize yields following fallow growth from this subset of the data with an R 2 of 0.42. This relationship of fallow biomass to subsequent maize yield was not observed across the whole data set due to incomplete fallow litterfall data, factors not included in the model and associated poor model prediction of recycled tree biomass. After site and tree calibration, the model can thus be applied to assess fallow management strategies for sites limited by water and nitrogen.

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Responses of soil crusting, runoff and erosion to fallowing in the sub-humid and semi-arid regions of West Africa

Cited by 81 publications

References 34 publications

Model-based study of the role of rainfall and land use–land cover in the changes in the occurrence and intensity of Niger red floods in Niamey between 1953 and 2012

Model-based study of the role of rainfall and land use–land cover in the changes in the occurrence and intensity of Niger red floods in Niamey between 1953 and 2012

Assessing Impacts of Land Use Changes on the Hydrology of a Lowland Rainforest Catchment in Ghana, West Africa

Modelling of planted legume fallows in Western Kenya using WaNuLCAS. (I) Model calibration and validation

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