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Hydrology ◽  
2022 ◽  
Vol 9 (1) ◽  
pp. 12
Author(s):  
Mouhamed Idrissou ◽  
Bernd Diekkrüger ◽  
Bernhard Tischbein ◽  
Felix Op de Hipt ◽  
Kristian Näschen ◽  
...  

Water scarcity for smallholder farming in West Africa has led to the shift of cultivation from uplands to inland valleys. This study investigates the impacts of climate and land use/land cover (LULC) change on water resources in an intensively instrumented inland valley catchment in Southwestern Burkina Faso. An ensemble of five regional climate models (RCMs) and two climate scenarios (RCP 4.5 and RCP 8.5) was utilized to drive a physically-based hydrological model WaSiM after calibration and validation. The impact of climate change was quantified by comparing the projected period (2021–2050) and a reference period (1971–2000). The result showed a large uncertainty in the future change of runoff between the RCMs. Three models projected an increase in the total runoff from +12% to +95%, whereas two models predicted a decrease from −44% to −24%. Surface runoff was projected to show the highest relative change compared to the other runoff components. The projected LULC 2019, 2025, and 2030 were estimated based on historical LULC change (1990–2013) using the Land Change Modeler (LCM). A gradual conversion of savanna to cropland was shown, with annual rates rom 1 to 3.3%. WaSiM was used to simulate a gradual increase in runoff with time caused by this land use change. The combined climate and land use change was estimated using LULC-2013 in the reference period and LULC-2030 as future land use. The results suggest that land use change exacerbates the increase in total runoff. The increase in runoff was found to be +158% compared to the reference period but only +52% without land use change impacts. This stresses the fact that land use change impact is not negligible in this area, and climate change impact assessments without land use change analysis might be misleading. The results of this study can be used as input to water management models in order to derive strategies to cope with present and future water scarcities for smallholder farming in the investigated area.


Author(s):  
P. M. Ngegba ◽  
S. M. Kanneh ◽  
D. D. Quee

The experiment was conducted in an Inland Valley Swamp during the dry spell of 2017 laid out in a randomized complete block design (RCBD) three replications at the Kabala Horticultural Crops Research Centre (KHCRC) cropping site, Ogoo Farm of the Sierra Leone Agricultural Research Institute (SLARI), Freetown, Sierra Leone. Raised beds measuring 5m x 1m (6 m2) with a 1m furrow between beds. Inter and intra row spacing of 75 cm by 50 cm with two rows per bed and two seeds per hills were directly sown. The treatments constituted NPK 15:15:15 at the rate of 0, 90, 120 and 150 kg/ha designated as T1, T2, T3 & T4  and Two hybrids of okra were used as experimental materials obtained from Indo-American Hybrid Seed Company, India; Okra-WASA-HyOKR-1 and Okra-WASA-HyOKR-2. Seeds were treated with Thiram Poison for longevity. Result indicates T2 (25.2; 35.1 cm) and T4 (56.9 cm) treatments recorded tallest plant heights followed by T2 (24.0, 34.4 & 50.1 cm), while T1 (18.8, 28.4 & 33.3 cm) had the shortest plant heights at 4, 8 & 10 Week After Planting respectively. Similarly, T4 & T2 (38.9, 65.5 & 44.8 cm) exhibited the largest SG and T1 (21.7, 33.0 & 52.0 cm) the least values at 4, 8 & 10 Week After Planting. While, the widest and narrowest LA at 4, 8 & 10 Week After Planting was observed in T3 (131.3, 135.0 & 158.5 cm2) and T1 (120.8, 121.8 & 128.1 cm2). With respect to yield and yield components, the longest (22.0 cm) and heaviest (112.7 g) fruit were recorded by T3 followed by T2 (19.1 cm & 101.3 g) with T1 having the shortest (11.7 cm) and lightest (52.3 g). The width of pod in T3 (31.2 cm) was greater than the rest of treatments and as usual, T1 indicated the least value (14.6 cm) respectively. The average NP produced plant-1 was shown by T2 & T3 (4.0) with the least of fruit produced by T1 (2.0). Also, 100 seed weight, T3 (106.7 g) weighted the highest followed by T2 (103.3 g), while T1 (60.3 g) accounted for the lowest seed weight. Conclusively, the two materials are adaptable to the climatic conditions of Sierra Leone (Western area). Hence further evaluation required across vegetable growing zones.


Hydrology ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 43
Author(s):  
Mouhamed Idrissou ◽  
Bernd Diekkrüger ◽  
Bernhard Tischbein ◽  
Boubacar Ibrahim ◽  
Yacouba Yira ◽  
...  

This study investigates the robustness of the physically-based hydrological model WaSiM (water balance and flow simulation model) for simulating hydrological processes in two data sparse small-scale inland valley catchments (Bankandi-Loffing and Mebar) in Burkina Faso. An intensive instrumentation with two weather stations, three rain recorders, 43 piezometers, and one soil moisture station was part of the general effort to reduce the scarcity of hydrological data in West Africa. The data allowed us to successfully parameterize, calibrate (2014–2015), and validate (2016) WaSiM for the Bankandi-Loffing catchment. Good model performance concerning discharge in the calibration period (R2 = 0.91, NSE = 0.88, and KGE = 0.82) and validation period (R2 = 0.82, NSE = 0.77, and KGE = 0.57) was obtained. The soil moisture (R2 = 0.7, NSE = 0.7, and KGE = 0.8) and the groundwater table (R2 = 0.3, NSE = 0.2, and KGE = 0.5) were well simulated, although not explicitly calibrated. The spatial transposability of the model parameters from the Bankandi-Loffing model was investigated by applying the best parameter-set to the Mebar catchment without any recalibration. This resulted in good model performance in 2014–2015 (R2 = 0.93, NSE = 0.92, and KGE = 0.84) and in 2016 (R2 = 0.65, NSE = 0.64, and KGE = 0.59). This suggests that the parameter-set achieved in this study can be useful for modeling ungauged inland valley catchments in the region. The water balance shows that evaporation is more important than transpiration (76% and 24%, respectively, of evapotranspiration losses) and the surface flow is very sensitive to the observed high interannual variability of rainfall. Interflow dominates the uplands, but base flow is the major component of stream flow in inland valleys. This study provides useful information for the better management of soil and scarce water resources for smallholder farming in the area.


2020 ◽  
Vol 69 (5) ◽  
pp. 1095-1105
Author(s):  
Mohamed M. Blango ◽  
Richard A.C. Cooke ◽  
Juana P. Moiwo ◽  
Patrick A. Sawyerr ◽  
Emmanuel Kangoma

Climate ◽  
2020 ◽  
Vol 8 (7) ◽  
pp. 83
Author(s):  
Geofrey Gabiri ◽  
Bernd Diekkrüger ◽  
Kristian Näschen ◽  
Constanze Leemhuis ◽  
Roderick van der Linden ◽  
...  

The impact of climate and land use/land cover (LULC) change continues to threaten water resources availability for the agriculturally used inland valley wetlands and their catchments in East Africa. This study assessed climate and LULC change impacts on the hydrological processes of a tropical headwater inland valley catchment in Uganda. The hydrological model Soil and Water Assessment Tool (SWAT) was applied to analyze climate and LULC change impacts on the hydrological processes. An ensemble of six regional climate models (RCMs) from the Coordinated Regional Downscaling Experiment for two Representative Concentration Pathways (RCPs), RCP4.5 and RCP8.5, were used for climate change assessment for historical (1976–2005) and future climate (2021–2050). Four LULC scenarios defined as exploitation, total conservation, slope conservation, and protection of headwater catchment were considered. The results indicate an increase in precipitation by 7.4% and 21.8% of the annual averages in the future under RCP4.5 and RCP8.5, respectively. Future wet conditions are more pronounced in the short rainy season than in the long rainy season. Flooding intensity is likely to increase during the rainy season with low flows more pronounced in the dry season. Increases in future annual averages of water yield (29.0% and 42.7% under RCP4.5 and RCP8.5, respectively) and surface runoff (37.6% and 51.8% under RCP4.5 and RCP8.5, respectively) relative to the historical simulations are projected. LULC and climate change individually will cause changes in the inland valley hydrological processes, but more pronounced changes are expected if the drivers are combined, although LULC changes will have a dominant influence. Adoption of total conservation, slope conservation and protection of headwater catchment LULC scenarios will significantly reduce climate change impacts on water resources in the inland valley. Thus, if sustainable climate-smart management practices are adopted, the availability of water resources for human consumption and agricultural production will increase.


2020 ◽  
Author(s):  
Claudia Schepp ◽  
Bernd Diekkrüger ◽  
Mathias Becker

<p>Due to their prolonged water availability wetlands are of increasing importance for small scale agriculture in East Africa. In the inundating landscape of central Uganda, inland valley wetlands are a common landscape unit with high potential for crop cultivation year-round. Yet little is known about the hydrological processes which bring out these favourable conditions. This study focusses on the relevance of interflow processes from the slopes into the wetland regarding water and nutrient delivery from different land use types. Hereby special attention is given to water pathways at the transition from upland geology to valley sediments and to nutrient relocation along the slopes.</p><p>Electrical Resistivity Tomography (ERT) was used as a non-invasive method to characterise interflow pathways in the highly variable saprolite geology and for subsurface delineation of the valley sediments. The measurements were complimented by a drilling campaign and infiltration experiments in different depths. Interflow collection pits were installed at the slope toe in order to quantify water and nutrient fluxes towards the wetland during two consecutive years. Additionally, soil moisture and nitrate content in the soil water were quantified at various positions along the slope.</p><p>ERT-imaging supports the hypothesis of a separation between a confined shallow aquifer and the soil water in the wetland sediments. Drilling results and hydrogeochemical analysis of the interflow and this shallow groundwater indicate a connection of the two components via macropores in the upper saprolite at the slope toe. At the same time interflow is transferred to the soil water of the wetland via a sandy loam layer which is found on top of the confining clay-loam layer of the wetland sediments. Both processes are active even during the dry season and therefore water from the interflow is relevant for water storage (shallow aquifer) and agricultural production (soil water) in the wetland.</p><p>Interflow volume and nitrate content both show a fast reaction to rainfall events, while the amount of water and nutrients delivered to the wetland is related to the land-use on the slope. Nitrate content in the soil water on the slopes suggests a relocation of nutrients in the upper soil horizons towards the slope toe. As infiltration capacity of the soil’s A-horizon is higher compared to the B-horizon a second  lateral flow component appears to be present close to the soil surface.</p><p>The results of this study emphasize the relevance of subsurface flow for wetland hydrology and give first explanations of wetland-upland connectivity in a complex saprolite geology.</p>


2020 ◽  
Vol 709 ◽  
pp. 136165 ◽  
Author(s):  
Komlavi Akpoti ◽  
Amos T. Kabo-bah ◽  
Elliott R. Dossou-Yovo ◽  
Thomas A. Groen ◽  
Sander J. Zwart

Agriculture ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 256 ◽  
Author(s):  
Bashiru Mansaray ◽  
Shaosheng Jin ◽  
Godwin S. Agbemavor Horlu

This study investigates the impact of farmland ownership and agro-ecological location on the adoption of the two most important sources of improved rice varieties (NERICA and ROK) in the context of Sierra Leone. In terms of farmland ownership, the results showed that farmers who cultivated their own land had a higher tendency of remaining as non-adopters of improved varieties, but those who rented farmland or were engaged in sharecropping had higher adoption rates of improved rice varieties. Also, the location of farmland (uplands or inland valley swamps) determined the rates of adoption of improved varieties differently. For instance, upland regions showed faster adoption of ROK varieties, but inland valley areas showed faster adoption of NERICA varieties. We also examined the survival rates of local rice varieties. The adoption of improved varieties was only occurring at a very low rate, and the farmers’ adoption of ROK varieties was swifter than for NERICA varieties. This study recommends that policies advocating the adoption of improved rice varieties in Sierra Leone must take into consideration the patterns of farmland ownership and location.


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