A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of requirements for the degree of Master of Science. May 30, 2016. / In statistics, a model is as good as the data fed to it. Data about hydrological events continues to grow rapidly over the years, with different variables being recorded on a continuous scale. These variables can be interpreted and used in a different manner among disciplines. Thus, choosing the right variables and interactions among variables is an important statistical step in building a good and accurate model. This dissertation involved the development of a statistical model which can be used to predict weekly water level within the Okavango river in northern Namibia. The parameters of the statistical mixed model were estimated based on two methods for longitudinal data, the Generalised Estimating Equations (GEE) which is a well known method of parameter estimation in longitudinal data analysis when the observed variables are correlated, and the Restricted Maximum Likelihood Estimation (REML) which is a likelihood based approach method, unlike the GEE. Using cross-validation and a simulation study, the GEE method of estimation was found to be less accurate and inconsistent in terms of prediction of parameter estimation of water level while the well known REML was found to predict the water level with a good degree of accuracy, consistency and with lower variance. Parameters from a simulation study have also shown less bias in REML method and predicted the cross-validation test-set with less bias. / GR 2016

The Okavango River Basin (ORB) located in southern Africa is a region of highly sensitive and biodiverse ecosystems. It spans Angola, Namibia and Botswana, with the world-famous Okavango Delta located in the latter country. The ecosystems depend on the highly seasonal ORB streamflow, which is also the major source of freshwater for the rural population, most of whom depend on subsistence farming. Climate variability and extremes such as droughts, hot days and extreme rainfall events are not well understood over this region. Also, the relationship between climate and other aspects like vegetation and river discharge are not well understood. To contribute to a better understanding of this relationship, the thesis investigated relationships between rainfall, temperature, Normalized Difference Vegetation Index (NDVI) and river discharge, and their interannual variability and trends. It was found that at monthly and seasonal time scales, NDVI spatial patterns are closely related to those of rainfall than temperature. The NDVI-rainfall and NDVI-temperature relationships differ north of 18.9°S where rainfall is higher than to its south. Correlations between NDVI and rainfall show lags of 1-2-months. Large areas across the region show significant warming trends in all seasons but mainly in October-December (OND), as well as wetting mainly in the north. The warming trend may imply more evaporation and desiccation which may exacerbate extreme event impacts such as severe droughts. Interannual variability of rainfall, NDVI and temperature is pronounced with significant correlations with El Niño-Southern Oscillation (ENSO), the subtropical Indian Ocean Dipole (SIOD) and the Botswana High for rainfall and temperature, and for NDVI with ENSO. The temperature (rainfall) correlations with ENSO and the Botswana were positive (negative), with the SIOD they were negative (positive), and the NDVI-ENSO correlations were negative. On longer time scales, the wet 2006-2013 period was analysed relative to much drier 1999-2005 epoch for OND. The 2006-2013 wetter conditions appear linked to La Niña Modoki conditions, regional circulation differences and warmer sea surface temperature near Angola. Extreme rainfall events over the ORB were analysed. The analysis was performed within a larger region in western central southern Africa (WCSA), given that many rainfall events extend beyond river basin boundaries. Focus was placed on extreme rainfall events accumulated over 1-day (DP1) and 3-days (DP3), during the main rainy season, January-April (JFMA). Due to data sparsity, the Climate Hazards Group Infrared Precipitation with Station data (CHIRPS) were used to identify these events. It was found that contributions of DP1 and DP3 events to JFMA rainfall totals are, on average, ~10% and ~17%, respectively, but in some years their contributions exceed 30%. Most of the events result from tropical-extratropical cloud bands, with tropical lows being also important. Interannual variability in extreme events is substantial and appears linked to ENSO and the Botswana High. Although ENSO influences the extreme events and rainfall totals more generally over southern Africa, by far the neutral JFMA 2017 season experienced the wettest conditions over the world-famous Okavango Delta region. Factors that contributed to these heavy rains included a deeper Angola Low, weaker mid-level Botswana High and anomalous westerly moisture fluxes from the tropical southeast Atlantic during January – early March. The second most intense rainfall event occurred on April 22nd, resulting from a cut-off low. DP1 frequencies show significant increasing trends, and similarly, rain-days and rain totals over many areas. These trends have important implications for agricultural and water management as well as wildlife conservation in the ORB. To contribute to a better understanding of drought over the ORB region, the thesis analysed various drought metrics. These include a Cumulative Drought Intensity (CDI) index, based on the product of maximum dry spell duration and maximum temperature anomaly, and the Standardised Precipitation-Evapotranspiration Index (SPEI). Strong horizontal gradients in frequencies of dry spells and hot days were found to shift south over the ORB from August to November as the tropical rain-belt shifts increasingly south of the equator, the Congo Air Boundary declines and the Botswana High strengthens and shifts south-westwards. By December, the tropical gradient in dry spell frequencies is unnoticeable while that across the Limpopo River and southern ORB region, where the Botswana High is centred, stands out. On seasonal time scales, October-November 2013-2021 is particularly hot and dry over the Okavango Delta region. The thesis provided evidence that this hot and dry epoch is related to a stronger and southward shifted Botswana High and reduced low-level moisture convergence. On interannual time scales, there were strong relationships with the Botswana High, and to lesser extent ENSO. A strong drying-warming trend was found in the early summer, linked to a significant strengthening of the Botswana High. These trends, in conjunction with the Coupled Model Intercomparison Project Phase 6 (CMIP6) projected early summer drying over southern Africa found in the literature, may impact severely on the sensitive ecosystems of the ORB, and on water availability as well as subsistence farming in the region.

Large catfishes (Clarias gariepinus & Clarias ngamensis) are not exploited commercially in the Okavango Delta, Botswana. They however constitute a large proportion of the gill net fishery catch (23 %) albeit as by-catch, coming second after cichlids (70 %). Monthly experimetal gill net sampling over 8 years showed that C. gariepinus was the most abundant species in the Okavango Delta by mass making up 37 % of the catch composition by fresh weight. Despite the relatively high abundance of C. gariepinus in the Okavango Delta, its status has never been fully assessed. For this reason, this study aimed to assess the status of C. gariepinus in the Okavango Delta with the particular goal to determine if the species could support a directed commercial gill net fishery. Investigation of the effects of the flood pulse on abundance of C. gariepinus showed that variability in water levels was the major driver of population abundance for this species. Three biological variables: (1) catch per unit effort (CPUE); (2) % catch composition and (3) Shannon's diversity index (H') exhibited a negative and significant relationship with the flood index within a year. The variation in these variables was statistically significant between months. There was a weak positive relationship between water levels and the biological variables between years suggesting increase in productivity of the system at high water levels without a lag period. Age and growth were determined using sectioned otoliths. Edge analysis showed that growth zone deposition occurred during the drawdown period in summer when water temperature and day length were increasing. The maximum recorded age was 15 years. Growth of this species was best described by the linear models (y = 21.50x + 427.39 mm LT; r² = 0.35) for females and (y = 23.79x + 440.83 mm LT; r² = 0.38) for males. The von Bertalanffy growth model described growth as Lt = 10000(1- exp(-0.002(t + 18.07))) mm LT for combined sexes Lt = 10000(1- exp( -0.002(t + 18.50))) mm LT , for females and Lt =908(1-exp(-0.076(t+7.95)))mmLT for males. Age at 50 % maturity was attained in the first year of life. Spawning occurred throughout the year with an apparent peak between November and April. The mean total annual mortality rate (Z) was 0.25 per year. The mean annual natural mortality rate (M) was 0.20 per year and fishing mortality (F) was calculated at 0.05 per year. The life history strategy of C. gariepinus was in between the periodic and opportunistic strategies. Therefore management of this species should be aimed at maintaining a healthy adult population and age structure. Since a large portion of the Okavango Delta is already protected and most other parts are also inaccessible to fishers there are enough spatial refugia for the species and the status quo should be maintained. Under this scenario, there is no need for regulation of the current mesh sizes because the species is harvested after maturity and replenishment of exploited populations will always occur from other parts of the system. Per recruit analyses indicate that the current fishing mortality maintains spawner biomass at levels greater than 90 % of pristine levels. Therefore a commercial fishery may be established using mesh 93 mm to maximize yield with a rotational harvesting strategy. Close monitoring is essential to ensure that re-colonization of overexploited habitats does indeed occur. Recreational angling and commercial gill net fishing need to be separated on a spatial and temporal scale during the feeding run to minimize potential conflicts.

Meyer’s Parrot Poicephalus meyeri is the smallest of the nine Poicephalus parrots, forming the P. meyeri superspecies complex with five congeners. Their distributional range far exceeds any other African parrot, extending throughout subtropical Africa. Meyer’s Parrots had previously not been studied in the wild, and therefore, gathering high-quality empirical data on their behavioural ecology became a research and conservation priority. The primary aim of the study was to correlate environmental (e.g. rainfall, habitat availability, resource characteristics, food resource abundance and temperature) and social (e.g. inter- and intra-specific competition, predation, and human disturbance) variables with aspects of their ecology (e.g. flight activity, food item preferences, breeding activity, and group dynamics) to evaluate the degree of specialization in resource use (e.g. trophic, nesting and habitat niche metrics). African deforestation rates are the highest in the world, resulting in twelve out of the eighteen Meyer’s Parrot range states undergoing drastic loss of forest cover over the last 25 years. Most commentary on the population status of Meyer’s Parrots and other Poicephalus parrots pre-dates this period of rapid deforestation In addition, over 75 000 wild-caught Meyer’s Parrots and almost 1 million wild-caught Poicephalus parrots have been recorded in international trade since 1975. Empirical data from this study was used to identify ecological weaknesses (e.g. niche specialization or low breeding turnover) for evaluation within the context of deforestation in the African subtropics. Baseline data on the breeding biology and nest cavity requirements of Meyer’s Parrots was also necessary to assess the viability of applying the conservative sustained-harvest model to African parrots. A unifying goal of this study was to advance our knowledge of the ecology of African parrots and other Psittaciformes by assessing the validity of current hypotheses put forward in the literature. The Meyer’s Parrot Project was initiated in January 2004 on Vundumtiki Island in the north-eastern part of the Okavango Delta, Botswana. Due to high flood waters between March and July 2004, road transects were postponed till August 2004. Transects were conducted at Vundumtiki from August 2004 to July 2005 and February 2007 to August 2007, and at Mombo from August 2005 to January 2006. During 480 road transects over 24 months, food item preferences closely tracked fruiting and flowering phenology, resulting in significant positive correlations between Levins’ niche breadth, rainfall and food resource availability. Meyer’s Parrot can, therefore, be considered opportunistic generalists predispersal seed predator that tracks resource availability across a wide suite of potential food items, including 71 different food items from 37 tree species in 16 families. Meyer’s Parrots were, however, found to be habitat specialists preferring established galleries of riverine forest and associated Acacia-Combretum marginal woodland. These strong habitat associations facilitate their wide distribution throughout the Kavango Basin, Linyanti Swamps, down the Zambezi valley, up along the Rift Valley system in associations with the great lakes, through the Upper Nile and the Sudd, and west as far as Lake Chad through the Sahel. Seventy-five nest cavities were measured during this study, including 28 nest cavities utilized by Meyer’s Parrots within the 430ha sample area at Vundumtiki. Over 1700 hours of intensive nest observations at six nest cavities was undertaken. Meyer’s Parrots formed socially monogamous pair-bonds maintained over at least four breeding seasons. Breeding pairs established breeding territories up to an estimated 160ha within which there were 1–6 nest cavities. Eggs hatched asynchronously, yet nestlings fledged synchronously with similar body size and condition. There was evidence to support the incidence of extra-pair copulations, however, mitochondrial DNA sequence data are required to confirm the incidence of extra-pair fertilizations. Meyer’s Parrots had no preferences in regard to nest tree species beyond the incidence of suitable nest cavities, which are selected and further excavated to accommodate their non-random nest cavity preferences. There was a significant non-nesting Meyer’s Parrot population during the breeding season, likely due to this longlived cavity-nester delaying nesting until a suitable breeding territory becomes available. Meyer’s Parrots utilize communal roosts during summer and disperse from them according to the Foraging Dispersal Hypothesis. Due to the requirement to roost during the middle of the day to avoid heat stress, Meyer’s Parrots have bimodal flight and feeding activity patterns. The highest probability of locating Meyer’s Parrots is between 08h30 and 11h00 during summer when both adults are feeding on the seeds of fleshy-fruits in riverine forest communities. Due to the paucity of data on the current distribution and population status of Meyer’s Parrots and other African parrots, a continent-wide survey of all African parrots represents a conservation priority. Current deforestation rates in several Meyer’s Parrot range, their specialist habitat associations, and lack of evidence to support adaptability to a changing landscape mosaic necessitate the re-classification of Meyer’s Parrots as data deficient or nearthreatened. Based on low breeding population due to limited breeding opportunities, the CITES Appendix II wild-caught bird trade should also be halted until the sustainability of this trade has been evaluated and the relevant information made available. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

This thesis presents an evaluation of the dispersive solid-phase extraction (d-SPE) method referred to as the quick, easy, cheap, effective, rugged and safe (QuEChERS) method for the determination of four organochlorine pesticide residues in fish samples. The pesticides investigated in this study were o, p′-DDT, p, p′-DDE, aldrin and dieldrin. The combined use of Gas Chromatography with an Electron Capture Detector (GC-ECD) and sensitive Time of Flight (TOF) mass detector facilitated the identification of the target analytes. In the absence of certified reference material, the overall analytical procedure was validated by systematic recovery experiments on spiked samples at three levels of 2, 5 and 10 ng/g. The targeted compounds were successfully extracted and their recovery ranged from 76 to 96% with relative standard deviations of less than 13%. The optimum QuEChERS conditions were 2g of fish powder, 10 ml acetonitrile and 1 min shaking time. The optimal conditions were applied to assess the levels of chlorinated pesticides in blunt-tooth catfish (Clarias ngamensis), tigerfish (Hydrocynus vittatus), Oreochromis andersonii and red-breasted tilapia (Tilapia rendalli) from the Okavango Delta, Botswana. Dieldrin, p, p′-DDE and aldrin were detected in all the analysed samples with a concentration range of 0.04 – 0.29, 0.07 – 0.33, 0.04 – 0.28 and 0.03 – 0.24 ng/g per dry weight in O. andersonii, C. ngamensis, T. rendalli and H. vittatus respectively. These concentrations were below the US-EPA 0.1 μg/g allowable limit in edible fish and the Australian Maximum Residue Limit (MRL) of 50 - 1000 ng/g in fresh fish. DDT was not detected in all the fish species investigated. The mean lipid content recorded in the fish samples were 1.24, 2.16, 2.18 and 4.21% for H. vittatus, T. rendalli, O. andersonni and C. ngamensis respectively. No systematic trend was observed between fish age and pesticide levels in fish. Acetylcholinesterase (AChE) activity assays were performed to assess the effects of organochlorine pesticides in Clarias ngamensis. The enzyme activity recorded in Clarias ngamensis from the Okavango Delta and the reference site was 12.31 μmol of acetylcholine iodide hydrolysed/min/g brain tissue. The enzyme activity remained the same indicating no enzyme inhibition. The conclusions drawn from this study are that the QuEChERS method is applicable for the determination of organochlorine pesticide residues in fish matrices. The fish from the Okavango Delta are safe for human consumption.

Water resources management practice has undergone changes in management approaches and principles over time. It was previously characterised by what scholars refer to as the hydraulic mission where ‘extreme engineering’ was the order of the day (Allan, 2003). As Radif (1999) argues, water resources managers and policy makers were initially driven to manage and supply water to people for its direct use / these included drinking, growing food, and providing power for domestic and industrial use. This modus operandi continued until the end of the 1970s. Over two decades later, this focus is still prevalent in many countries in southern Africa including Botswana. As Swatuk and Rahm (2004) state, “augmenting supply is a continuing focus of government activity”. The National Water Master Plan (NWMP) is the current policy document guiding water resources management in Botswana and it focuses on supply-side interventions in response to increasing water demand. According to SMEC et al. (1991), the consulting company that conducted the NWMP study, “the investigation and studies... indicated the need for the continuing development of water supplies throughout Botswana over the next 30 years”. Based on these observations, government has developed significant human and technical capacity in exploiting both surface and groundwater resources (Swatuk and Rahm, 2004).

Water resources management practice has undergone changes in management approaches and principles over time. It was previously characterised by what scholars refer to as the hydraulic mission where ‘extreme engineering’ was the order of the day (Allan, 2003). As Radif (1999) argues, water resources managers and policy makers were initially driven to manage and supply water to people for its direct use / these included drinking, growing food, and providing power for domestic and industrial use. This modus operandi continued until the end of the 1970s. Over two decades later, this focus is still prevalent in many countries in southern Africa including Botswana. As Swatuk and Rahm (2004) state, “augmenting supply is a continuing focus of government activity”. The National Water Master Plan (NWMP) is the current policy document guiding water resources management in Botswana and it focuses on supply-side interventions in response to increasing water demand. According to SMEC et al. (1991), the consulting company that conducted the NWMP study, “the investigation and studies... indicated the need for the continuing development of water supplies throughout Botswana over the next 30 years”. Based on these observations, government has developed significant human and technical capacity in exploiting both surface and groundwater resources (Swatuk and Rahm, 2004).

Thesis (Ph.D.(Agricultural Economics))--University of Pretoria, 2006. / Includes summary. Includes bibliographical references. Available on the Internet via the World Wide Web.

The Okavango is a vast inland delta system in northern Botswana which receives an annual flood from the highlands of southern Angola. There are distinct communities of fish in the Okavango which can be separated from each other by the physical characteristics of the different habitat types with which they co-evolved. This thesis provides an account of the biology and ecology of selected fish species in the Okavango Delta. Their response to the annual flood regime, and the environmental factors which limit their distribution and abundance, are examined. The thesis emphasizes the importance of water fluctuations in determining the nature of the fish fauna and the reaction of the fishes in terms of community structure, movements, breeding, predator-prey interactions and feeding. Four major ecotones were studied in the Okavango Delta. In the riverine floodplain and perennial swamp ecotones a higher species diversity was recorded than in the seasonal swamp and drainage rivers ecotones where diversity was lowest and comprised mainly of smaller fish species. A greater variety of habitat types was associated with the riverine floodplain and perennial swamp relative to the seasonal swamp and drainage rivers. The variety of habitat types between ecotones is associated with the degree of flood inundation in the respective ecotones. During the course of this study, annual recruitment of fish into the drainage rivers was from refugia in the seasonal swamp whereas the greatest degree of lateral and longitudinal movement was in the riverine floodplain and perennial swamp. Movement was in response to both biological requirements, such as availability of food and spawning sites, and physical features of the environment, such as the changing water depth. The total catch per unit effort (CPUE) of fish throughout the year was more constant in the riverine floodplain and perennial swamp than in the seasonal swamp and drainage rivers where CPUE fluctutated widely. An increase in CPUE during the duration of this study was apparent and related to the magnitude of the annual flood. In contrast to most other African wetlands, the arrival of the annual flood in the Okavango Delta coincides largely with the dry winter months. This situation presented an opportunity to compare the influence of floods and water temperature on the reproductive biology of the selected fish species. The results show a definite pattern and indicate that both the flood cycle and increased water temperatures greatly influence the breeding cycles of the selected species. The tilapia Oreochromis andersonii exhibited a considerable degree of phenotypic plasticity. Fish from the seasonally inundated areas showed a smaller mean size, egg size and larger number of eggs relative to fish in the perennially flooded areas. The size at sexual maturity was also smaller. These different reproductive characteristics exhibited by O. andersonii are dependent on the degree of water retention in the different habitats. The fishes of the Okavango have adopted other reproductive strategies to survive the changing environmental conditions brought about by an annual flood cycle. These strategies include the construction of foam nests, as described for Hepsetus odoe, for guarding the young and to provide an oxygen-rich environment. Two main non-piscivorous feeding pathways were identified in the Okavango. These are a detritus pathway based on dead plant and animal material, and an epiphyte pathway, based on algae and invertebrates that are attached to plant stems. Seasonal changes in diet in relation to the annual flood were recorded. The most dramrtic change was demonstrated by the catfish Clarias gariepinus which congregates in mass aggregations in the northern regions of the Delta and hunt in packs. Pack-hunting by catfish is a regular response to the annual fluctuations in water level. It is my conclusion that the main flow of biotic and abiotic stimuli within the Okavango Delta originates from the relatively hydrologically stable riverine floodplain and perennial swamp ecotones to the widely fluctuating seasonal swamp and drainage rivers ecotones. The relatively stable ecotones allow a diverse and biotically interdependent fish community to develop, whereas the widely fluctuating seasonal swamp and drainage rivers ecotones are characterized by a less diverse and interdependent fish community. The degree of abiotic and biotic interdependence among fish in an ecotone is very important for the long term management of the Okavango Delta. Potential developers have to determine whether the effect of a given action by man is likely to result in a long term disturbance or merely in an elastic recoil to a more or less similar state. Recommendations are made on the conservation and management of Okavango fishes taking into account the ecological characteristics of the delta.

This dissertation reviews the principles of International River Basin Management and their application by the governments of Angola, Botswana and Namibia. The dissertation deals with the issues popularised by governments, water planners and international agencies that the twenty-first century's conflicts will be fought over water. Increasingly this concern is being used to justify new water-supply dams and river diversion projects. This is especially so in arid Southern Africa, the focus of this dissertation, where numerous major international water transfers are underway and many more are being planned. While Namibia's growing thirst is a serious problem, the story is more complicated than just too many basin states putting their straws into one glass. The growing conflicts over the Okavango's water use raise broader questions about ownership of common resources, and equity of access to those resources. Most southern African countries depend on primary natural resources to sustain economies and their people. The environmental issues are remarkably similar in countries within the region, and the economic, social and political fortunes of the individual countries are intertwined. Furthermore, the ways in which resources are being managed are similar and thus cause for common concern. In general, the ability of countries in the region to achieve sustainable development depends not on national policies but also on the commitment of neighbours to practice sound environmental management. This is because activities in one country can easily cause impacts on a neighbour and possibly result in "downstream" opportunity costs. This case study of the Okavango River Basin, a river facing prospective developments from riparian states Angola, Botswana and Namibia, attempts to find sustainable solutions to solving international resource conflict. In addition to outlining the possible future threats to the Okavango River, this study proclaims a number of recommendations in the way of declaring alternatives to Namibia's plans to extract water from the Okavango River. One such recommendation is the encouragement of Water Demand Management as an alternative to water transfer by Namibia. This management strategy is aimed at optimising the use of available water rather than developing new or extended supplies and as a result it has a vital role to play since it contributes to sustainable development rather than over exploitation of limited natural resources. The majority of large rivers in the Southern African Development Community (SADC) are shared by three or more countries, and as the region's water resources come under growing development pressure, the importance of establishing effective national and regional methods and institutions for sustainably managing these resources will increase greatly. From economic, ecological and human welfare perspectives, the Okav,ango River Basin is arguably one of the most important transboundary natural resources (TBNR) in the region. Owing to the basin's remoteness and history of conflict, the Okavango was spared much of the destructive developments that rivers in the region have suffered. As a result, the relatively pristine Okavango ecosystem continues to provide significant benefits to the region much as it has done for centuries. As we approach the new millennium, however, it is clear that the health of the Okavango River Basin is threatened as riparian states increasingly turn to the Okavango to support their growing populations and economies. / Thesis (M.Env.Dev.)-University of Natal, Pietermaritzburg, 2002.