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Evaluation of the ambient air quality analysis of HCL, H2S and NH3 from enhanced evaporation spray system ponds on the Highveld of South AfricaHermandez Peral, Ivan. January 2006 (has links)
Thesis (MSc (Meteorology))-University of Pretoria, 2006. / Includes bibliographical references. Available on the Internet via the World Wide Web.
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Quantifying evaporation on the surface of slimes dams in the southeastern part of the North West ProvinceVon Bredow, Sigrid 15 April 2014 (has links)
M.A. (Geography and Environmental Management) / Water can be regarded as a scarce commodity in South Africa and one cannot rely solely on the discovery of new water resources to meet the ever increasing demands. Water is arguably the most precious resource in South Africa and its proper management in all spheres of activity is imperative ( Middleton and Stern,1987 ). This is no different in the mining industry where a primary consumptive use of water is in the tailings dams and associated return water. Restricted implementation of Government water plans and a series of droughts has forced users of water to optimise their use of water. A key to correct water management of a tailings disposal system on a gold mine lies in accurate and meaningful water balance. To provide an accurate water balance, quantifying the water loss is necessary. The water loss in a tailings system is mainly due to evaporation and interstitial flow. For the purpose of this study, evaporation is dealt with in more detail.
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Time series modelling of water evaporation from selected dams in the Limpopo Province of South AfricaPhasha, Mmanyaku Goitsemang January 2022 (has links)
Thesis (M.Sc. (Statistics)) -- University of Limpopo, 2022 / Water is a precious natural resource and one of the most vital substance
for sustainability of life . The increase in water evaporation is a major prob lem where factors such as high temperature and minimum rainfall are the
contributing factors. The aim of the study was to perform time series mod elling of water evaporation from the selected dams in the Limpopo province
South Africa. A daily evaporation time series data was used in the study
with variables such as temperature and rainfall. Daily water evaporation
rate time series data was differenced to make the data series stationary and
Dickey-Fuller test was used to test the stationarity of the data series. The
Autoregressive Conditional Heteroskasticity (ARCH) and Generalized Au toregressive Conditional Heteroskasticity (GARCH) model was performed
on the water evaporation time series data from the selected dams. Vec tor Autoregression (VAR) was used to determine the relationship between
the variables evaporation, rainfall and temperature. Identification of time
series models was done using the autoregressive integrated moving average
(ARIMA). The best ARIMA models were selected based on the autocor relation function (ACF) and partial autocorrelation function (PACF), and
the smallest value of Bayseian Information (BIC). The best models selected
for each dam are: Mokolo dam, ARIMA (1, 1, 2) model; Ga-Rantho dam,
ARIMA (1, 1, 2) model; Leeukraal DeHoop dam, ARIMA (1, 1, 1) model
and Luphephe dam, ARIMA (2, 1, 3) model. The correlation coefficient,
coefficient of determinant (R2
) and root mean square (RMSE) were used to
determine the performance of the model. The water evaporation time series
data from the selected dams was forecasted using the best selected ARIMA
models from the selected dams and then predicted for the next 3 years, where
the results showed a positive constant water evaporation rate.
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Trickle-down ecohydrology : complexity of rainfall interception and net precipitation under forest canopiesAllen, Scott T. (Scott Thomas) 12 June 2012 (has links)
Rainfall interception is a primary control over the moisture input to a forested ecosystem through the partitioning of precipitation into throughfall, stemflow, and an evaporated component (i.e. the interception loss). Rainfall interception is a spatially and temporally varying process at multiple scales, but heterogeneity in interception processes are poorly understood and poorly described in the literature. We need to know how net precipitation varies in ecosystems because natural systems are driven by non-linear ecohydrological processes where mean values cannot capture localized effects or the cumulative consequences associated with an extremely heterogeneous input. In this thesis, we present two studies that investigate the heterogeneity of interception loss and throughfall in a forested catchment in the western Cascades range of Oregon. In one study, we examined the spatio-temporal patterns among point measurements of throughfall depth and isotopic composition to determine the cause of isotopic differences between throughfall and rainfall. Our results indicated that the residual moisture retained on the canopy from previous events plays a major role in determining the isotopic composition of the next event's throughfall. Differences between the isotopic composition of throughfall samples could indicate further partitioning of throughfall into various flow-paths from the canopy. The second project examined the question of how vegetation variability and terrain complexity drive interception loss heterogeneity at the whole-catchment scale. We applied a simple interception model to a watershed gridded at a 50 m resolution to investigate the relative importance of topographic and vegetative controls over the spatial variability of interception loss. We found that storm characteristics are crucial regarding the impact of spatial heterogeneities in vegetation and evaporation rates. In the Pacific Northwest climate, interception loss is not highly variable for the majority of the year because the annual precipitation is dominated by large storms with low interception losses. However, the net precipitation input to a watershed becomes extremely heterogeneous in the summer due to high interception loss variability. Summer interception loss could be an important control over the spatial variability of the availability of moisture, coinciding with when vegetation is most water-limited. / Graduation date: 2013
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Comparative evaporation measurements above commercial forestry and sugarcane canopies in the KwaZulu-Natal Midlands.Burger, Caren. January 1999 (has links)
An understanding of the water use of different crops commonly grown in an area is
essential for the implementation of integrated catchment management in South Africa.
With increasing pressure on water resources, mainly due to the recent changes in the
Water Act, it has become important to determine the actual water demands of agricultural
and other crops. Policy makers require knowledge of whether forestry canopies use more
water than grassland and other agricultural crops.
The Bowen ratio and Penman-Monteith methods were used in a comparative study of the
evaporation from Saccharum, Acacia and Eucalyptus. All of the research was conducted
at marginal sites located in the KwaZulu-Natal Midlands of South Africa over a period of
two years.
The Bowen ratio energy balance (BREB) technique combines the Bowen ratio (J3) (the
ratio between the sensible, H and latent heat flux density, XE), with the net irradiance (Rn)
and soil heat flux densities (G) to calculate evaporation. A comparative study of the sitespecific
energy balance components (Rn, G, H and AE), general climatic conditions
(rainfall, solar irradiance and air temperature) and other site-specific parameters (leaf area
index and average canopy height) was conducted on Saccharum and young commercial
forests consisting of Acacia and Eucalyptus. The energy balance highlighted important
differences in the energy balance components between the different canopies. The
differences between the reflection coefficients at the three sites contributed mainly to the
differences in the evaporation rates. The low reflection coefficients of the forest canopies
(Acacia and Eucalyptus) (0.1 and 0.08 respectively) were smaller than of the sugarcane
canopy (0.2). This resulted in more energy available (« 6 %) for partitioning between the
sensible and latent heat flux densities and higher evaporation rates for the forestry
canopies. Where low leaf area indices existed (Acacia and Eucalyptus sites) (LAI < 2),
the soil heat flux density contributed up to 40 % of the net irradiance (G = 0.4 Rn). The evaporation rates for Saccharum, Acacia and Eucalyptus averaged 2 mm day"1 in
winter and 5 mm day"1 in summer. The slightly higher summer evaporation rate for
Eucalyptus (5.6 mm day"1), compared to Acacia (4.9 mm day"1), resulted from the lower
reflection coefficients and canopy resistance (rc) for Eucalyptus (ocs = 0.08, rc = 35 s m"1)
compared to Acacia (ocs = 0.1, rc = 45 s m"1).
Automatic weather station data (solar irradiance, air temperature, water vapour pressure
and windspeed) were applied to site-specific Penman-Monteith equations to predict
evaporation for all three sites. Statistically significant relationships (slope, m « 1,
r2 > 0.8) were found between the measured (Bowen ratio) and simulated (site-specific
Penman-Monteith) evaporation estimates. The current study has demonstrated the
effectiveness of applying the Penman-Monteith equation to forest and sugarcane canopies
to predict evaporation, provided accurate net irradiance, soil heat flux densities and
canopy resistances are used. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1999.
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Water and salt management strategies in a closed drainage basin.Ali, Hatem M. M. January 1998 (has links)
No description available.
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Total evaporation estimation from sugarcane using the scintillation technique.Wiles, Luke Wilson. January 2006 (has links)
Ongoing concerns about the efficient and sustainable utilisation of South Africa’s water resources have resulted in much interest regarding the water use of different land uses within a catchment. Research has been focussed on water use by different dryland vegetation, in particular commercial forestry which has been declared a Stream Flow Reduction Activity for which a water use license is required for production. Consequently, concerns about the water use of other dryland crops have lead to a need to quantify water use by other land uses, particularly sugarcane. In this document, previous research focussed on water use by sugarcane is reviewed and summarised, together with an experiment where an energy balance approach has been used to quantify water consumption in the form of total evaporation for an area of sugarcane production in the KwaZulu-Natal Midlands with an assessment of the seasonal variability of this water consumption for a period of 1 year. The study was performed using a Large Aperture Scintillometer to measure sensible heat flux, whilst all other energy balance components, as well as rainfall, soil moisture and other climatic data were obtained using standard methods. Total evaporation was estimated from latent heat flux which was derived as a residual of the energy balance. Total evaporation varies over the year with substantially higher values occurring in summer in response to high energy and water availability. Over the year, the crop used approximately 630mm of water which equates to 53% of rainfall at the site. The two main factors affecting the seasonal variability of water use by sugarcane are net radiation and soil moisture content. In the wetter months when soil moisture is readily available, net radiation limits total evaporation. In the drier months, soil moisture is not as readily available, and limits total evaporation. Air temperature and relative humidity proved to also be important considerations in their effect on total evaporation. The total evaporation estimates obtained could be compared to a baseline (grassland) and used in simulations for a better understanding of the stream flow reduction potential of sugarcane and the seasonal variability thereof. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.
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