Analysis Of Annual Rainfall In Zimbabwe For Trends And Periodicities,1891-1988

A GJZ article on climate changes.Recent droughts during the early 1980s have led to the belief that rainfall over Southern Africa has changed or follows some form of periodic behavior. Annual rainfall at 20 stations in Zimbabwe covering the period 1891 to 1988 is analyzed for the presence of trends, discontinuities, persistence and periodicities. The results show that droughts cannot be described by any of these processes

Community Participation in Rural Water Supply

A Geographical Education Magazine article.The need for safe and adequate water by all human beings is well recognized. However, a close examination o-f the accessibility, adequacy and the quality of water for the people of developing countries reveals a very sad story. In 1980 it was estimated that about 70% of the people in developing countries had no reasonable access to safe and adequate water supply. This means that even today, over half of humankind lacks one of the basic requirements for life. The term "reasonable access" means that a disproportionate time of those who draw water should not be spent fetching water, and "safe water” should be free of pathogens. Having realized the plight of the rural population in developing countries, the world community through the United Nations in 1970 aimed at providing reasonably accessible and safe water to 25% of the rural population by 1980. In 1978 the UN Conference on Water emphasized the importance of safe water supply and sanitation in controlling diseases such as diarrhea, typhoid, cholera, infectious hepatitis, etc. During the thirty-fifth session of the UN General Assembly in November 1980, the period 1981-1990 was declared the International Drinking Water Supply and Sanitation Decade (IDWSSD). All the member countries committed themselves to improving the water supply and sanitation services so that by 1990 the Decade target of water supply for all will be achieve

Challenges For Environmental Management In The Mining Sector

An IMR Open Report.Revenue from mineral resources has contributed to the improvement of the quality of life in several countries globally. The importance of mining in the SADC region is demonstrated by the amount of minerals produced; 40% of vanadium, 72% of the platinum group of metals, 40% of chromite, and 55% of diamonds of the global output. Mining contributes about 60% of the foreign currency receipts of the SADC region (www.sadc.int). Some of the major settlements providing much needed services have developed due to mining, e.g. Johannesburg, Francistown, Copperbelt towns of Zambia. Mining contributes significantly to government revenue in Southern Africa, e.g. 45% in -Botswana in 2004. The importance of the mining sector has been recognized at the SADC level through various initiatives aimed at the development of this sector, e.g. SADC Protocol on Mining, and attempts at harmonizing policies relevant to the development of the sector (UNECA, 2004). However, in the international arena, continued exploitation of mineral resources is increasingly depended upon the demonstrated capacity of the industry to effectively deal with the vast amount of waste generated from mining through to beneficiation

Factors influencing sustainability of communally-managed waterfacilities in rural areas of Zimbabwe

Sustainability of point water facilities is a major development challenge in many rural settings ofdeveloping countries not sparing those in the Sub-Saharan Africa region. This study was done inZimbabwe to investigate the factors influencing sustainability of rural water supply systems. A total of399 water points were studied in Nyanga, Chivi and Gwanda districts. Data was collected using aquestionnaire, observation checklist and key informant interview guide. Multi-Criteria analysis was usedto assess the sustainability of water points and inferential statistical analysis such as Chi square tests andAnalysis of Variance (ANOVA) were used to determine if there were significant differences on selectedvariables across districts and types of lifting devices used in the study area. The thematic approach wasused to analyze qualitative data. Results show that most water points were not functional and only 17%across the districts were found to be sustainable. A fusion of social, technical,financial, environmentaland institutional factors was found to be influencing sustainability. On technical factors the ANOVAresults show that the type of lifting devicefitted at a water point significantly influences sustainability(F¼37.4, p<0.01). Availability of spare parts at community level was found to be determining thedowntime period of different lifting devices in the studied wards. Absence of user committees was foundto be central in influencing sustainability as water points that did not have user committees were notsustainable and most of them were not functional during the time of the survey

Contribution of understorey vegetation to evapotranspiration partitioning in apple orchards under Mediterranean climatic conditions in South Africa

Orchard evapotranspiration (ET) is a complex flux which has been the subject of many studies. It often includes transpiration from the trees, cover crops and weeds, evaporation from the soil, mulches and other orchard artefacts. In this study we investigated the contribution of the orchard floor evaporative fluxes to whole orchard ET focusing on the transpiration dynamics of understorey vegetation which is currently not well known. Data on the partitioning of ET into its constituent components were collected in apple (Malus Domestica Bork) orchards with varying fractional canopy cover. The study orchards were in the prime apple growing regions in South Africa. The orchards were planted to the Golden Delicious/Reinders and the red cultivars (i.e. Cripps’ Pink/ Royal Gala/Fuji). Tree transpiration was quantified using the heat ratio method and the thermal dissipation sap flow techniques. Understorey transpiration was measured at selected intervals using micro stem heat balance sap flow gauges calibrated against infrared gas analyser readings. Orchard ET was measured using an open path eddy covariance system while the microclimate, radiation interception, and soil evaporation were also monitored. Orchard floor evaporative fluxes accounted for as much as 80% of the measured ET in young orchards with dense understorey vegetation that covered most of the orchard floor

Water use of selected cover crop species commonly grown in South African fruit orchards and their response to drought stress

Cover crops are widely planted in orchards for a variety of reasons. These include suppressing soil erosion, nutrient cycling, phytosanitary purposes, general orchard aesthetics etc. However, there is need to balance these benefits against use of scarce resources such as water and nutrients. Currently no information exists on how different cover crop species use water in orchards and how they cope with drought stress. The aim of this study was therefore to compare the transpiration dynamics of various cover crop types in order to identify species with conservative water use rates. Studied species included: 1) two exotic legumes i.e. Lupine (Lupinus albus L.), and Common vetch (Vicia sativa), 2) three exotic grasses i.e. Tall fescue (Festuca arundinacea), Rye grass (Lolium perenne), and Kikuyu grass (Pennisetum clandestium) and; 3) grasses that are indigenous to sub-Saharan Africa i.e. African Lovegrass (Eragrostis capensis) and Rhodes grass (Chloris gayana). The crops were planted in pots under controlled greenhouse conditions. Transpiration rates were quantified using miniature stem heat balance sap flow gauges and by manual weighing. Drought stress was imposed by withholding irrigation at selected intervals and the responses were quantified through changes in the water relations of the plants. The study showed that exotic legumes had the highest daily water use which peaked at about 2.4 L per square metre of leaf area per day, followed by exotic grasses at 1.5–2.0 L/m2/d. The indigenous grasses used the least water ranging from 0.8 to 1.2 L/m2/d. The indigenous grasses largely displayed an isohydric response to drought stress by maintaining their leaf water status with increasing soil water deficit. The exotic species, on the other hand, showed risk taking behaviour (anisohydry) wherein both the transpiration and leaf water status decreased sharply as drought stress increased. Consequently, some exotic species failed to recover when stress was relieved. From a water use perspective, this study demonstrates that indigenous grass species are more appropriate as cover crops in South African orchards because of their low transpiration rates and the ability to cope with extended periods of water deficit. © 2021 Elsevier Lt

Effects of selected dams on river flows of Insiza River, Zimbabwe

This paper examines effects of three dams on flow characteristics of Insiza River on which they are located. The storage capacities of these dams varies from an equivalent of 48–456% of the mean annual runoff. Mean annual runoff and annual maximum flood flows have not been modified by the presence of these dams. The average number of days per year without runoff had decreased downstream of two dams. A comparison was made of flow duration curves at sites upstream and downstream of the selected dams. Significant differences were detected between the flow duration curves of upstream and downstream sites. Exceedance frequencies of low flows had decreased downstream of two dams, while these had increased downstream of the other dam. The study recommends development of operating rules for these dams that will ensure that changes detected in low flows do not adversely affect instream flow requirement

Conservation agriculture and climate resilience

Agricultural productivity growth is vital for economic and food security outcomes which are threatened by climate change. In response, governments and development agencies are encouraging the adoption of ‘climate-smart’ agricultural technologies, such as conservation agriculture (CA). However, there is little rigorous evidence that demonstrates the effect of CA on production or climate resilience, and what evidence exists is hampered by selection bias. Using panel data from Zimbabwe, we test how CA performs during extreme rainfall events - both shortfalls and surpluses. We control for the endogenous adoption decision and find that use of CA in years of average rainfall results in no yield gains, and in some cases yield loses. However, CA is effective in mitigating the negative impacts of deviations in rainfall. We conclude that the lower yields during normal rainfall seasons may be a proximate factor in low uptake of CA. Policy should focus promotion of CA on these climate resilience benefits

Using sap flow data to assess variations in water use and water status of apple orchards of varying age groups in the Western Cape Province of South Africa

No accurate quantitative information currently exists on how water use of apple (Malus domestica) orchards varies from planting to full-bearing age, leading to poor irrigation and water allocation decision making. This study sought to address this knowledge gap by investigating how the water use and tree water status vary with canopy cover, cultivar, and climatic conditions in 12 orchards growing in prime apple-producing regions in South Africa. The orchards were planted to the Golden Delicious/Golden Delicious Reinders cultivars which are widely planted in South Africa and the Cripps’ Pink/Cripps’ Red/Rosy Glow which are high-value lateseason cultivars. The performance of two transpiration reduction coefficients, one based on sap flow (Ksf) and the other based on soil water depletion (Ks) (FAO approach) were evaluated against the midday stem water potential (MSWP) in all the orchards. While canopy cover had a clear effect on the whole-tree sap flow rates, there were no significant differences in the transpiration per unit leaf area among the cultivars. The daily average sap flux density under unstressed conditions was highest (~284 cm3∙cm–2) in the medium canopy cover orchards (30–44% fractional cover), followed by the mature orchards (~226 cm3∙cm–2), and was lowest in the young orchards (~137 cm3∙cm–2). Canopy cover rather than growing season length had a greater effect on seasonal total water use. Peak daily orchard transpiration ranged from 1.7 mm for young Golden Delicious Reinders trees to 5.0 mm in mature Golden Delicious trees that were maintained with&nbsp; large canopies to reduce sunburn damage to the fruit. For the red cultivars, the peak daily transpiration ranged from 2.0 to 3.9 mm, and the mature trees were maintained with less dense canopies to facilitate the development of the red fruit colour. The less dense canopies on the red cultivars had water-saving benefits since the seasonal total transpiration was lower relative to the Golden Delicious cultivar. The sap flow derived stress&nbsp; coefficient was strongly correlated to the MSWP (R2 ~ 0.60–0.97) in all the orchards while Ks was not able to detect plant stress due to over-irrigation. Keywords: cultivar canopy cover transpiration reduction xylem water potentia