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Water Flow and Sediment Flux Forecast in the ChókwèIrrigation Scheme, Mozambique

Journal of Water Resource and Protection 2020年第12期12卷 1089-1122页

作者： Lateiro Salvador De Sousa Raphael Muli Wambua james messo raude Benedict Mwavu Mutua Division of Agriculture Instituto Superior Politécnico de Gaza Campus Politécnico de Lionde Chókwè-Gaza Province Mozambique Department of Agricultural Engineering Egerton University Nakuru Kenya Soil Water & Environmental Engineering Department Jomo Kenyatta University of Agriculture & Technology Nairobi Kenya Division of Planning Partnerships Research and Innovation Kibabii University Bungoma Kenya

This study sought to forecast water flow and sediment flux in the scheme as potential contributions for improved management in the Chókwè Irrigation Scheme (CIS). Fieldwork data was collected during dry (DS) and wet (WS) seasons. Flow measurement was performed at 9 stations using a calibrated flow meter OTT C31. Water flow and sediment flux from 2004 to 2019 were used. Hydrodynamic forecast simulations were performed using Mann-Kendall test and ARIMA model for determination of temporal trends. Findings suggest higher values during DS for water discharge and sediment flux. Mann-Kendall test for sediment discharge trends was not significant at 95% significance level, except for the Offtake in WS. ARIMA test for the sediment discharges, at the Intake, for DS and WS, sediments were well described by the ARIMA model and gave a good result for the sediments. Good fit between the observed and the predicted ARIMA model was found. ARIMA model for sediment discharge at CIS based on AIC has a good fit for AR (p = 1), whereby, at the Intake the ARIMA p-value was 0.822 and 0.932, for WS and DS, respectively. Whilst in the Offtake, the ARIMA p-value was 0.877 and 0.893, respectively. These results can be used to improve the CIS management, both for water flow and sediment flux.

关键词： Water Flow Sediment Flux Mann-Kendall Test ARIMA Model Chókwè Irrigation Scheme

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Environmental and energy requirements for different production biomass of Nile tilapia(Oreochromis niloticus)in recirculating aquaculture systems(RAS)in Kenya

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Aquaculture and Fisheries 2021年第6期6卷 593-600页

作者： Daniel Mwendwa Wambua Patrick G.Home james M.raude Stephen Ondimu Department of Soil Water and Environmental EngineeringJomo Kenyatta University of Agriculture and TechnologyP.O.BOX 62000-00200NairobiKenya Department of Agricultural and Biosystems Engineering Jomo Kenyatta University of Agriculture and TechnologyP.O.BOX 62000-00200NairobiKenya

Recirculating Aquaculture Systems(RAS)offers a better option to increase aquaculture production with limited land and water resources while minimizing water *** biggest challenges in RAS is to maintain favorable water quality for the fish to *** practice of RAS in Kenya is minimal with the improper matching of RAS components and production densities for the existing few and in most cases,leading to a system *** study aimed at evaluating environmental and energy requirements for different production biomass of Nile tilapia in a RAS established in a controlled *** production densities and water flow rates were varied while at the same time,the water quality parameters(dissolved oxygen,ammonia,pH,electrical conductivity and temperature)were *** energy consumed for pumping and aeration was also *** stocking biomass varied from 2.3 kg/m^(3) to 10 kg/m^(3) while flow rate was varied from 2.0 L/min and increased at intervals of 1.0 L/min to the maximum attainable flow rate of 10.0 L/*** pumice rock packed in a 1000 L tank and equipped with a bell siphon was used as the *** removal reduced with increasing flow rate with removal rates of 75%at 2.0-3.0 L/min to 9%at 8.0-10.0 L/*** water pH increased with increasing flow rate with R^(2) ranging from 0.4 to *** conductivity increased with flow rate from 112 mg/L to as high as 209 mg/*** oxygen increased with flow rate and ranged from 1.0 mg/L to 7.0 mg/*** consumption increased with flow rate and raged from 0.4 kW h at 2.3 kg/m^(3) stocking biomass to 2.4 kW h at 10 kg/m^(3)stocking *** stocking densities and flow rates resulted to lower purification efficiencies and higher power consumptions than low stocking densities and flow *** order to maintain good RAS water quality,increased production and profits among farmers using RAS in Kenya,there is need to give proper advice on the right combination of st

关键词： Biofilter Flow rate Purification efficiency Stocking biomass Water quality

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Detection of Spatial, Temporal and Trend of Meteorological Drought Using Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) in the Upper Tana River Basin, Kenya

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Open Journal of Modern Hydrology 2018年第3期8卷 83-100页

作者： Raphael M. Wambua Benedict M. Mutua james M. raude Department of Agricultural Engineering Egerton University Nakuru Kenya Division of Planning Research and Innovation Kibabii University Bungoma Kenya Jomo Kenyatta University of Agriculture & Technology Juja Kenya

Drought events across the world are increasingly becoming a critical problem owing to its negative effects on water resources. There is need to understand on-site drought characteristics for the purpose of planning mitigation measures. In this paper, meteorological drought episodes on spatial, temporal and trend domains were detected using Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) in the upper Tana River basin. 41 years (1980-2016) monthly precipitation data from eight meteorological stations were used in the study. The SPI and EDI were used for reconstruction of the drought events and used to characterize the spatial, temporal and trend distribution of drought occurrence. Drought frequency was estimated as the ratio of a defined severity to its total number of events. The change in drought events was detected using a non-parametric man-Kendall trend test. The main drought conditions detected by SPI and EDI are severe drought, moderate drought, near normal, moderate wet, very wet and extremely wet conditions. From the results the average drought frequency between 1970 and 2010 for the south-eastern and north-western areas ranged from 12.16 to 14.93 and 3.82 to 6.63 percent respectively. The Mann-Kendall trend test show that drought trend increased in the south-eastern parts of the basin at 90% and 95% significant levels. However, there was no significant trend that was detected in the North-western areas. This is an indication that the south-eastern parts are more drought-prone areas compared to the North-western areas of the upper Tana River basin. Both the SPI and the EDI were effective in detecting the on-set of drought, description of the temporal variability, severity and spatial extent across the basin. It is recommended that the findings be adopted for decision making for drought-early warning systems in the river basin.

关键词： SPI EDI Drought-Detection Man-Kendall Drought-Prone Areas Drought Frequency Drought-Early Warning System Upper Tana River Basin

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