SEGH Articles

SEGH2018 Prize Winners Series: Mumba Mwape

20 August 2018
Winner of a Best Poster Prize at SEGH2018: Selection and design of irrigation systems in Zambia - this installment of the Prize Winners Series is contributed by Mumba Mwape.

 

Mumba R. Mwape1, Derek M. Heeren2,3, Dean Eisenhauer3, Aaron Mittelstet2,3 and Laszlo Hayde4

1: Zambia Agricultural Research Institute, Zambia, 2: University of Nebraska-Lincoln, USA, 3: Robert Daugherty Water for Food Global Institute, USA, 4: IHE-Delft Institute for Water Education, Netherlands

Zambia has been making various reforms aimed at improving the agriculture sector for the past two decades. Recent developments have seen a streamlined focus on irrigation as a means of increasing production and productivity to bring about sustainability in the agriculture sector, which had previously been dependant on rainfall. These efforts have been directed at small-scale farmers who have been impacted by reduced rainfall due to climate variability. The high cost of irrigation equipment and the urgent need to increase food production entails that irrigation plans guarantee sustainability, effectiveness and efficiency. This research was aimed at evaluating the suitability and viability of community irrigation systems, and designing systems for two sites (of 60 ha each) in Masaiti and Samfya in agro-ecological region III of the country using surface (river) and ground (well) water sources respectively.

 

 Field infiltration test (taking readings)

 

In establishing the suitability of the areas, soil tests such as infiltration and texture analyses were conducted as well as the depth of the soils. The quality of water was assessed for different parameters for toxicity levels that may restrict water use in irrigated agriculture. To determine the quantity of water, a pumping test was carried out for ground water while 20 year monthly flow rates of the river were used for surface water. Land and water availability were also assessed. Aquacrop was used to determine the crop water requirements and the yield potentials and based on the yield potential results, the most profitable crops with the least water requirements were selected. The soil tests showed high infiltration rates of 10 cm/hr and 11.6 cm/hr for Masaiti and Samfya respectively. This led to the recommendation of only sprinkler and drip irrigation systems. The pumping test gave a potential yield of 110 l/s while the river’s 20-year average flow rate gave 2 m3/s and 26.6 m3/s as the lowest and highest rate respectively. The quality of the water from both sites was found to have no restriction to agricultural use according Food and Agriculture Organization (FAO) standards. The crops selected, for a 60 ha irrigation system, had a water requirement of 50.8 l/s when water is not limited and 34.5 l/s if staggered planting dates are used. This water requirement can be supplied by both sources that were analysed, up to 2 irrigation systems by the well and 9 irrigation systems if 25% of the river’s lowest flow rate is diverted for use. The land tenure system in the area is customary and farm sizes per household was between 5->50 ha and while cultivation was less than 10% of the total area owned. The economic analysis of the irrigation development for a center pivot and drip irrigation system gave a positive outlook with an improvement in yield of 65% to more than 100% and with a profit margin per ha approximately 10 times more than the profit of current production practices.  

Back to archive
Keep up to date
Join Us or Renew

SEGH Events

35th International Conference for Society for Environmental Geochemistry and Health

Manchester, UK

01 July 2019

How to organise an SEGH conference, meeting or event

31 December 2020

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Fate and partitioning of heavy metals in soils from landfill sites in Cape Town, South Africa: a health risk approach to data interpretation 2019-06-14

    Abstract

    The fate and persistence of trace metals in soils and sludge from landfill sites are crucial in determining the hazard posed by landfill, techniques for their restoration and potential reuse purposes of landfill sites after closure and restoration. A modified European Community Bureau of Reference’s (BCR) sequential extraction procedure was applied for partitioning and evaluating the mobility and persistence of trace metals (As, Cd, Cr, Cu, Ni, Pb, Sb, Se, Zn) in soils from three landfill sites and sludge sample from Cape Town, South Africa. Inductively coupled plasma optical emission spectroscopy was used to analyze BCR extracts. The mobility sequence based on the BCR mobile fraction showed that Cu (74–87%), Pb (65–80%), Zn (59–82%) and Cd (55–66%) constituted the mobile metals in the soils from the three sites. The mobility of Cu, Zn and Ni (> 95%) was particularly high in the sludge sample, which showed significant enrichment compared to the soil samples. Geo-accumulation index (Igeo) and risk assessment code were used to further assess the environmental risk of the metals in the soils. Exposure to the soils and sludge did not pose any non-cancer risks to adult and children as the hazard quotient and hazard index values were all below the safe level of 1. The cancer risks from Cd, Cr and Ni require that remedial action be considered during closure and restoration of the landfill sites.

  • An investigation into the use of < 38 µm fraction as a proxy for < 10 µm road dust particles 2019-06-13

    Abstract

    It is well documented that a large portion of urban particulate matters is derived from road dust. Isolating particles of RD which are small enough to be inhaled, however, is a difficult process. In this study, it is shown for the first time that the < 38 µm fraction of road dust particles can be used as a proxy for road dust particles < 10 µm in bioaccessibility studies. This study probed similarities between the < 10 and < 38µm fractions of urban road dust to show that the larger of the two can be used for analysis for which larger sample masses are required, as is the case with in vitro analysis. Road dust, initially segregated to size < 38 µm using sieves, was again size segregated to < 10 µm using water deposition. Both the original < 38 µm and the separated < 10 µm fractions were then subject to single particle analysis by SEM–EDX and bulk analysis by ICP-OES for its elemental composition. Dissolution tests in artificial lysosomal fluid, representative of lung fluid, were carried out on both samples to determine % bioaccessibility of selected potentially harmful elements and thus probe similarities/differences in in vitro behaviour between the two fractions. The separation technique achieved 94.3% of particles < 10 µm in terms of number of particles (the original sample contained 90.4% as determined by SEM–EDX). Acid-soluble metal concentration results indicated differences between the samples. However, when manipulated to negate the input of Si, SEM–EDX data showed general similarities in metal concentrations. Dissolution testing results indicated similar behaviour between the two samples in a simulated biological fluid.

  • Degradation of petroleum hydrocarbons in unsaturated soil and effects on subsequent biodegradation by potassium permanganate 2019-06-13

    Abstract

    To date, the oxidation of petroleum hydrocarbons using permanganate has been investigated rarely. Only a few studies on the remediation of unsaturated soil using permanganate can be found in the literature. This is, to the best of our knowledge, the first study conducted using permanganate pretreatment to degrade petroleum hydrocarbons in unsaturated soil in combination with subsequent bioaugmentation. The pretreatment of diesel-contaminated unsaturated soil with 0.5-pore-volume (5%) potassium permanganate (PP) by solution pouring and foam spraying (with a surfactant) achieved the total petroleum hydrocarbon (TPH) removal efficiencies of 37% and 72.1%, respectively. The PP foam, when coupled with bioaugmentation foam, further degraded the TPH to a final concentration of 438 mg/kg (92.1% total reduction). The experiment was conducted without soil mixing or disturbance. The relatively high TPH removal efficiency achieved by the PP–bioaugmentation serial foam application may be attributed to an increase in soil pH caused by the PP and effective infiltration of the remediation agent by foaming. The applied PP foam increased the pH of the acidic soil, thus enhancing microbial activity. The first-order biodegradation rate after PP oxidation was calculated to be 0.068 d−1. Furthermore, 94% of the group of relatively persistent hydrocarbons (C18–C22) was removed by PP–bioaugmentation, as verified by chromatogram peaks. Some physicochemical parameters related to contaminant removal efficiency were also evaluated. The results reveal that PP can degrade soil TPH and significantly enhance the biodegradation rate in unsaturated diesel-contaminated soil when combined with bioaugmentation foam.