Citation Context

...g the satellite image values to calibrated radiances and black body temperatures, and by adjusting the black body temperature values according to the emissivities of the land cover in the image (e.g. =-=Lillesand and Kiefer, 1994-=-). Emissivity describes how efficiently an object radiates energy compared to a blackbody. The wavelengths used for thermal remote sensing are in the region 10.5-12.5 µm (thermal infrared, TIR) and 3-...

Citation Context

...nce Vegetation Index (NDVI) (Rouse et al., 1973 cit. Lawrence and Ripple, 1998), but many other algorithms can be found in the literature (cf. Crist and Cicone, 1984; Hall-Könyves, 1988; Huete, 1988; =-=Running and Coughlan, 1988-=-; Nemani et al., 1993a; Filella and Penuelas, 1994; Qi et al., 1994; Danson and Plummer, 1995; McCarthy, 1996; Yoshioka et al., 2000; Qi et al., 2000). Ecoregion classification (Papers I and IV), vege...

Citation Context

...lised Difference Vegetation Index (NDVI) (Rouse et al., 1973 cit. Lawrence and Ripple, 1998), but many other algorithms can be found in the literature (cf. Crist and Cicone, 1984; Hall-Könyves, 1988; =-=Huete, 1988-=-; Running and Coughlan, 1988; Nemani et al., 1993a; Filella and Penuelas, 1994; Qi et al., 1994; Danson and Plummer, 1995; McCarthy, 1996; Yoshioka et al., 2000; Qi et al., 2000). Ecoregion classifica...

Citation Context

...be estimated from satellite images in a Tasselled Cap transformation, i.e. a rotation of the spectral data establishing new axes in components directly related to physical scene characteristics (e.g. =-=Kauth and Thomas, 1976-=-; Cohen and Spies, 1992; Lauver and Whistler, 1993). The index is a contrast between the mid infrared (MIR) bands and the visible and NIR bands. Microwave remote sensing (e.g. Boisvert et al., 1995; M...

Citation Context

...s of indices were used in the thesis: Vegetation index: Use in thesis: Wetness index: Use in thesis: Indicates spatial distribution of photosynthetically active vegetation (cf. Peterson et al., 1987; =-=Nemani et al., 1993-=-a). Used for parameterising various ecological functions in models of hydrology and climate (for example FOREST-BGC, Nemani et al. 1993b). Most vegetation indices are based on relations between the Re...

Citation Context

...), but many other algorithms can be found in the literature (cf. Crist and Cicone, 1984; Hall-Könyves, 1988; Huete, 1988; Running and Coughlan, 1988; Nemani et al., 1993a; Filella and Penuelas, 1994; =-=Qi et al., 1994-=-; Danson and Plummer, 1995; McCarthy, 1996; Yoshioka et al., 2000; Qi et al., 2000). Ecoregion classification (Papers I and IV), vegetation dynamics (grazing pressure) (Paper I), surface temperature e...

Citation Context

...e Landsat ETM data, but the fires could not be uniquely identified in the data. MODIS (25 scenes) Two different algorithms were applied to the MODIS data (by D. Roy); the MODIS active fire algorithm (=-=Kaufman et al. 1998-=-) (1.0 km resolution) and a newly developed burned area algorithm (Roy et al., 2002) (500 m resolution). The MODIS instrument calibration was still being refined during the 2000 fire season, and the f...

Citation Context

... commonly used vegetation index is the Normalised Difference Vegetation Index (NDVI) (Rouse et al., 1973 cit. Lawrence and Ripple, 1998), but many other algorithms can be found in the literature (cf. =-=Crist and Cicone, 1984-=-; Hall-Könyves, 1988; Huete, 1988; Running and Coughlan, 1988; Nemani et al., 1993a; Filella and Penuelas, 1994; Qi et al., 1994; Danson and Plummer, 1995; McCarthy, 1996; Yoshioka et al., 2000; Qi et...

Citation Context

...(25 scenes) Two different algorithms were applied to the MODIS data (by D. Roy); the MODIS active fire algorithm (Kaufman et al. 1998) (1.0 km resolution) and a newly developed burned area algorithm (=-=Roy et al., 2002-=-) (500 m resolution). The MODIS instrument calibration was still being refined during the 2000 fire season, and the fire algorithms were known to be under-performing. MAS (1 scene) Intense and low-gra...

Citation Context

...t. Lawrence and Ripple, 1998), but many other algorithms can be found in the literature (cf. Crist and Cicone, 1984; Hall-Könyves, 1988; Huete, 1988; Running and Coughlan, 1988; Nemani et al., 1993a; =-=Filella and Penuelas, 1994-=-; Qi et al., 1994; Danson and Plummer, 1995; McCarthy, 1996; Yoshioka et al., 2000; Qi et al., 2000). Ecoregion classification (Papers I and IV), vegetation dynamics (grazing pressure) (Paper I), surf...

Citation Context

...nd are not based directly on satellite image bands. Patch indices can be used to describe the structure of a landscape (cf. O´Neill et al., 1988; McGarigal and Marks, 1994; Goward and Williams, 1997; =-=Haines-Young and Chopping, 1996-=-). These indices are often applied in landscape ecology. The simplest forms of patch indices are perimeter vs. area ratios, increasing in complexity up to fractal dimensions and contagion indices. A s...

Citation Context

...on; and MODIS Airborne simulator and Landsat ETM data were used for high resolution studies of fires of single occasions.sHistorically, AVHRR images have been widely adopted for detecting fires (e.g. =-=Matson and Dozier, 1981-=-; Kaufman et al., 1990; Justice et al. 1992; Langaas, 1995), but not specifically for sub-surface fires. In this study, peat fires were detected using standard fire detection algorithms with absolute ...

Citation Context

...ace. The following types of indices were used in the thesis: Vegetation index: Use in thesis: Wetness index: Use in thesis: Indicates spatial distribution of photosynthetically active vegetation (cf. =-=Peterson et al., 1987-=-; Nemani et al., 1993a). Used for parameterising various ecological functions in models of hydrology and climate (for example FOREST-BGC, Nemani et al. 1993b). Most vegetation indices are based on rel...

Citation Context

... 1984; Hall-Könyves, 1988; Huete, 1988; Running and Coughlan, 1988; Nemani et al., 1993a; Filella and Penuelas, 1994; Qi et al., 1994; Danson and Plummer, 1995; McCarthy, 1996; Yoshioka et al., 2000; =-=Qi et al., 2000-=-). Ecoregion classification (Papers I and IV), vegetation dynamics (grazing pressure) (Paper I), surface temperature estimations (Paper III). Soil and canopy moisture can be estimated from satellite i...

Citation Context

... the Okavango River and Delta are shared between three countries - Angola, Namibia and Botswana. The total area of the catchment is approximately 325 000 km 2 , covering 1 % of the African continent (=-=FAO, 1997-=-). The largest area of the catchment (about 52 %) is found inside Angola, and the least (15 %) belongs to Botswana (Figure 2). The western parts of the catchment (in Namibia) are dormant, and essentia...

Citation Context

...ypes of land cover ecoregions of the Okavango Delta were classified using a rule-based contextual classification method (for examples of rule based classifications, see e.g. Robinson and Frank, 1987; =-=Argialas and Harlow, 1990-=-; Srinivasan and Richards, 1993; Dymond and Luckman, 1994; Chmiel and Gumbricht, 1996; Lein and Lemons, 1997; Houhoulis and Michener, 2000). Ringrose et al. (1988) used visual and digital analysis of ...

Citation Context

...wetland have not previously been mapped. NOAA AVHRR images have successfully been used to classify water in other geographic regions (e.g. Schneider et al., 1985; Harris and Mason, 1989; Prata, 1990; =-=Birkett, 2000-=-). In this Okavango study, nearly 3000 AVHRR images from the period 1985-2000 were used. One scene for every 10-day period was manually selected for water versus land classification. To extend the tim...

Citation Context

...ated and formed in different ways. The nucleus of an island may be an anthill (termite mound) where nutrients are accumulated and after a while becoming colonized by terrestrial vegetation and fauna (=-=Dangerfield et al., 1998-=-; McCarthy et al., 1998b) (Figure 6a). An island is thus developed and continues to grow by chemical precipitation. Another group of islands originates from meandering river channels, where the outer ...

Citation Context

... utilising the reflectance difference in vegetation foliage in these wavelengths. The most commonly used vegetation index is the Normalised Difference Vegetation Index (NDVI) (Rouse et al., 1973 cit. =-=Lawrence and Ripple, 1998-=-), but many other algorithms can be found in the literature (cf. Crist and Cicone, 1984; Hall-Könyves, 1988; Huete, 1988; Running and Coughlan, 1988; Nemani et al., 1993a; Filella and Penuelas, 1994; ...

Citation Context

...ave remote sensing (e.g. Boisvert et al., 1995; Mattikalli et al., 1996; Ulaby et al., 1996; Ahern, 1998) and ratios between TM spectral bands 4,5 and 7 (NIR to MIR) (e.g. Musick and Pelletier, 1986; =-=Fiorella and Ripple, 1993-=-) are also used for wetness estimations. The Tasselled Cap wetness index was used in the land cover ecoregion classification described in Papers I and IV. 18sBrightness index: Use in thesis: Thermal b...

Citation Context

...M data were used for high resolution studies of fires of single occasions.sHistorically, AVHRR images have been widely adopted for detecting fires (e.g. Matson and Dozier, 1981; Kaufman et al., 1990; =-=Justice et al. 1992-=-; Langaas, 1995), but not specifically for sub-surface fires. In this study, peat fires were detected using standard fire detection algorithms with absolute thresholds in the mid infrared region, diff...

Citation Context

... algorithms can be found in the literature (cf. Crist and Cicone, 1984; Hall-Könyves, 1988; Huete, 1988; Running and Coughlan, 1988; Nemani et al., 1993a; Filella and Penuelas, 1994; Qi et al., 1994; =-=Danson and Plummer, 1995-=-; McCarthy, 1996; Yoshioka et al., 2000; Qi et al., 2000). Ecoregion classification (Papers I and IV), vegetation dynamics (grazing pressure) (Paper I), surface temperature estimations (Paper III). So...

Citation Context

...rete class (object) data, and are not based directly on satellite image bands. Patch indices can be used to describe the structure of a landscape (cf. O´Neill et al., 1988; McGarigal and Marks, 1994; =-=Goward and Williams, 1997-=-; Haines-Young and Chopping, 1996). These indices are often applied in landscape ecology. The simplest forms of patch indices are perimeter vs. area ratios, increasing in complexity up to fractal dime...

Citation Context

...ed Cap transformation, i.e. a rotation of the spectral data establishing new axes in components directly related to physical scene characteristics (e.g. Kauth and Thomas, 1976; Cohen and Spies, 1992; =-=Lauver and Whistler, 1993-=-). The index is a contrast between the mid infrared (MIR) bands and the visible and NIR bands. Microwave remote sensing (e.g. Boisvert et al., 1995; Mattikalli et al., 1996; Ulaby et al., 1996; Ahern,...

Citation Context

...ngo Delta, Botswana. The maps are projected to S UTM 34, using the Cape datum. The coordinates are given in km in the main map. The average annual inflow to the Delta is approximately 9.0 x 10 9 m 3 (=-=McCarthy and Ellery, 1998-=-) but has during the past 60 years ranged from 6.0 x 10 9 to 1.6 x 10 10 m 3 (McCarthy et al., 2000). The peak flow in the upper Panhandle occurs around April, and takes approximately four months to t...

Citation Context

...species. In Paper IV, 12 types of land cover ecoregions of the Okavango Delta were classified using a rule-based contextual classification method (for examples of rule based classifications, see e.g. =-=Robinson and Frank, 1987-=-; Argialas and Harlow, 1990; Srinivasan and Richards, 1993; Dymond and Luckman, 1994; Chmiel and Gumbricht, 1996; Lein and Lemons, 1997; Houhoulis and Michener, 2000). Ringrose et al. (1988) used visu...

Citation Context

...n in km in the main map. The average annual inflow to the Delta is approximately 9.0 x 10 9 m 3 (McCarthy and Ellery, 1998) but has during the past 60 years ranged from 6.0 x 10 9 to 1.6 x 10 10 m 3 (=-=McCarthy et al., 2000-=-). The peak flow in the upper Panhandle occurs around April, and takes approximately four months to traverse the Delta, resulting in flooding during the otherwise 6sdry winter months. The rains over t...

Citation Context

...s of indices were used in the thesis: Vegetation index: Use in thesis: Wetness index: Use in thesis: Indicates spatial distribution of photosynthetically active vegetation (cf. Peterson et al., 1987; =-=Nemani et al., 1993-=-a). Used for parameterising various ecological functions in models of hydrology and climate (for example FOREST-BGC, Nemani et al. 1993b). Most vegetation indices are based on relations between the Re...

Citation Context

... beautiful appearance. This was particularly the case at sunrise and sunset, when the luxuriant vegetation received additional charms by the brilliant, but softened, rays of a tropical sun.” In: C.J. =-=Andersson, 1856-=-. Lake Ngami; or, Explorations and Discoveries During Four Years’ Wanderings in the Wilds of South Western Africa. Hurst and Blackett Publishers, London. p. 495. iiisivsPreface Since 1999 I have had t...

Citation Context

...ces are often based on discrete class (object) data, and are not based directly on satellite image bands. Patch indices can be used to describe the structure of a landscape (cf. O´Neill et al., 1988; =-=McGarigal and Marks, 1994-=-; Goward and Williams, 1997; Haines-Young and Chopping, 1996). These indices are often applied in landscape ecology. The simplest forms of patch indices are perimeter vs. area ratios, increasing in co...

Citation Context

...o have been presented by Ringrose et al. (1988, 1997) and McCarthy et al. (1993a), and the seasonal flood by McCarthy et al. (1998a). Studies of the surrounding Kalahari have been more abundant (e.g. =-=Ringrose et al., 1990-=-, 1991, 1998, 1999a, 1999b; Gustafsson, 1994; Vanderpost et al., 1998) and research within the ongoing SAFARI 2000 regional science initiative (Swap et al., 2000) are currently adding to the volume vi...

Citation Context

...ite images in a Tasselled Cap transformation, i.e. a rotation of the spectral data establishing new axes in components directly related to physical scene characteristics (e.g. Kauth and Thomas, 1976; =-=Cohen and Spies, 1992-=-; Lauver and Whistler, 1993). The index is a contrast between the mid infrared (MIR) bands and the visible and NIR bands. Microwave remote sensing (e.g. Boisvert et al., 1995; Mattikalli et al., 1996;...

Citation Context

...mulator and Landsat ETM data were used for high resolution studies of fires of single occasions.sHistorically, AVHRR images have been widely adopted for detecting fires (e.g. Matson and Dozier, 1981; =-=Kaufman et al., 1990-=-; Justice et al. 1992; Langaas, 1995), but not specifically for sub-surface fires. In this study, peat fires were detected using standard fire detection algorithms with absolute thresholds in the mid ...

Citation Context

... waters are fresh in spite of the high evapotranspiration rates (~97%) (Gieske, 1997). The salt concentration increases less than could be expected from the Panhandle to the lower parts of the Delta (=-=McCarthy and Metcalfe, 1990-=-). One important factor explaining this is the salt encrusted island interiors. Evapotranspiration by the riparian forests on the islands causes saturation of calcite and amorphous silica, leading to ...

Citation Context

...nt ways. The nucleus of an island may be an anthill (termite mound) where nutrients are accumulated and after a while becoming colonized by terrestrial vegetation and fauna (Dangerfield et al., 1998; =-=McCarthy et al., 1998-=-b) (Figure 6a). An island is thus developed and continues to grow by chemical precipitation. Another group of islands originates from meandering river channels, where the outer side of the channel has...

Citation Context

...ns of the Okavango Delta were classified using a rule-based contextual classification method (for examples of rule based classifications, see e.g. Robinson and Frank, 1987; Argialas and Harlow, 1990; =-=Srinivasan and Richards, 1993-=-; Dymond and Luckman, 1994; Chmiel and Gumbricht, 1996; Lein and Lemons, 1997; Houhoulis and Michener, 2000). Ringrose et al. (1988) used visual and digital analysis of Landsat MSS data to differentia...

Citation Context

...sted island interiors. Evapotranspiration by the riparian forests on the islands causes saturation of calcite and amorphous silica, leading to precipitation in the soils (McCarthy and Metcalfe, 1990; =-=McCarthy et al., 1993-=-b). More soluble salts (sodium carbonate / bicarbonate) are collected as surface crusts at island centres during the dry season (see Figure 6 d) but are flushed from the surface during the rains, and ...

Citation Context

...tract water from water systems which are riparian to them, according to international law and the Southern African Development Community (SADC) Protocol on shared water systems (ILA, 1966; ILC, 1994; =-=SADC, 1995-=- cit. Ashton, 2000). The civil war in Angola has so far prevented large-scale water resources development on the Quito and Cubango rivers, but it seems unclear what pace development will take when pea...

Citation Context

.... Kauth and Thomas, 1976; Cohen and Spies, 1992; Lauver and Whistler, 1993). The index is a contrast between the mid infrared (MIR) bands and the visible and NIR bands. Microwave remote sensing (e.g. =-=Boisvert et al., 1995-=-; Mattikalli et al., 1996; Ulaby et al., 1996; Ahern, 1998) and ratios between TM spectral bands 4,5 and 7 (NIR to MIR) (e.g. Musick and Pelletier, 1986; Fiorella and Ripple, 1993) are also used for w...

Citation Context

...lassified using a rule-based contextual classification method (for examples of rule based classifications, see e.g. Robinson and Frank, 1987; Argialas and Harlow, 1990; Srinivasan and Richards, 1993; =-=Dymond and Luckman, 1994-=-; Chmiel and Gumbricht, 1996; Lein and Lemons, 1997; Houhoulis and Michener, 2000). Ringrose et al. (1988) used visual and digital analysis of Landsat MSS data to differentiate ecological zones of the...

Citation Context

...gical regime The channels of the Delta are fringed by dense aquatic vegetation. As the organic material accumulates in and around the channels, layers of peat develop, sometimes as thick as 5 metres (=-=Ellery et al., 1989-=-). When the channels are abandoned the peat desiccates and catches fire, as a result of lightning strikes or fires lit by humans. The peat fires are of a smouldering type, with several fire fronts, bu...

Citation Context

...ow in the Delta is to the eastern and middle parts, in the Nqoga/Maunachira and Jao/Boro River systems. 7sSalt balance The Delta waters are fresh in spite of the high evapotranspiration rates (~97%) (=-=Gieske, 1997-=-). The salt concentration increases less than could be expected from the Panhandle to the lower parts of the Delta (McCarthy and Metcalfe, 1990). One important factor explaining this is the salt encru...

Citation Context

...anhandle, which is the entry channel into the Okavango Delta (Figure 4). The Delta surface is very flat with an elevation difference of approximately 60 metres between the northern and southern tips (=-=Gumbricht et al., 2002-=-).sFigure 3. The Okavango River in the Panhandle. Photo T. Gumbricht Figure 4. The Okavango Delta, Botswana. The maps are projected to S UTM 34, using the Cape datum. The coordinates are given in km i...

Citation Context

...high resolution studies of fires of single occasions.sHistorically, AVHRR images have been widely adopted for detecting fires (e.g. Matson and Dozier, 1981; Kaufman et al., 1990; Justice et al. 1992; =-=Langaas, 1995-=-), but not specifically for sub-surface fires. In this study, peat fires were detected using standard fire detection algorithms with absolute thresholds in the mid infrared region, differences between...

Citation Context

...nt ways. The nucleus of an island may be an anthill (termite mound) where nutrients are accumulated and after a while becoming colonized by terrestrial vegetation and fauna (Dangerfield et al., 1998; =-=McCarthy et al., 1998-=-b) (Figure 6a). An island is thus developed and continues to grow by chemical precipitation. Another group of islands originates from meandering river channels, where the outer side of the channel has...

Citation Context

...ses Angola. The Tripartite Permanent Water Commission on the Okavango River basin (OKACOM), formed in 1994, has the mission to secure sustainable water management and use between the riparian states (=-=OKACOM, 1994-=-). The future of the Delta attracts worldwide attention concerning conservation, and mutual agreements on sustainable water use between Botswana and upstream catchment countries are of great concern. ...

Citation Context

...the Okavango wetland have not previously been mapped. NOAA AVHRR images have successfully been used to classify water in other geographic regions (e.g. Schneider et al., 1985; Harris and Mason, 1989; =-=Prata, 1990-=-; Birkett, 2000). In this Okavango study, nearly 3000 AVHRR images from the period 1985-2000 were used. One scene for every 10-day period was manually selected for water versus land classification. To...

Citation Context

...re referred to as “ physiographic regions” throughout this thesis (Figure 5). Figure 5. Physiographic regions of the Okavango Delta. The flooding patterns are constantly changing in the Okavango (cf. =-=Wilson and Dincer, 1976-=-). The Thaoge River in the western Delta used to carry more water than today, filling up Lake Ngami south of the Delta (see Figure 4). In the 1850s the lake was filled with water (Andersson, 1856) but...

Citation Context

...6; Cohen and Spies, 1992; Lauver and Whistler, 1993). The index is a contrast between the mid infrared (MIR) bands and the visible and NIR bands. Microwave remote sensing (e.g. Boisvert et al., 1995; =-=Mattikalli et al., 1996-=-; Ulaby et al., 1996; Ahern, 1998) and ratios between TM spectral bands 4,5 and 7 (NIR to MIR) (e.g. Musick and Pelletier, 1986; Fiorella and Ripple, 1993) are also used for wetness estimations. The T...

Citation Context

...ganic debris. When the river changes its course due to lateral hydraulic gradients, it leaves a raised linear feature in the landscape, to be colonised by vegetation forming inverted channel islands (=-=McCarthy, 1992-=-) (Figure 6c). Once nucleated, islands continuously develop and change as a result of physical, chemical and biological processes. Different processes shape islands, predominantly chemical precipitati...

Citation Context

...as surface crusts at island centres during the dry season (see Figure 6 d) but are flushed from the surface during the rains, and are believed to accumulate in the deep groundwater below the islands (=-=McCarthy and Ellery, 1994-=-). There is a clear vegetation zonation across the salt encrusted islands, with salt tolerant species in the centre and riparian forest at the rim. Solute sediment input to the Delta is approx. 350 00...

Citation Context

...sted island interiors. Evapotranspiration by the riparian forests on the islands causes saturation of calcite and amorphous silica, leading to precipitation in the soils (McCarthy and Metcalfe, 1990; =-=McCarthy et al., 1993-=-b). More soluble salts (sodium carbonate / bicarbonate) are collected as surface crusts at island centres during the dry season (see Figure 6 d) but are flushed from the surface during the rains, and ...

Citation Context

...isible and NIR bands. Microwave remote sensing (e.g. Boisvert et al., 1995; Mattikalli et al., 1996; Ulaby et al., 1996; Ahern, 1998) and ratios between TM spectral bands 4,5 and 7 (NIR to MIR) (e.g. =-=Musick and Pelletier, 1986-=-; Fiorella and Ripple, 1993) are also used for wetness estimations. The Tasselled Cap wetness index was used in the land cover ecoregion classification described in Papers I and IV. 18sBrightness inde...

Citation Context

...ial and economic benefits that are derived from the Delta (Ashton, 2000). It seems uncertain, however, what actual effects water abstraction will have, as the natural variations in flow are high (cf. =-=Ashton and Manley, 1999-=-). To clarify the effects, hydrological and ecosystem modelling needs to be developed further. To do so, an extensive digital spatial database is needed to quantify the characteristics of the Delta. T...

Citation Context

...ion and island quantification studies in particular both relied heavily on the GIS analytic capabilities. The different systems used were ER-Mapper (Earth Resource Mapping), IDRISI (Clark University; =-=Eastman, 1993-=-) and ArcView (ESRI). Both satellite and thematic GIS data were used in the image analysis and GIS software, moving between the systems after data conversions. Data processing tools were programmed in...

Citation Context

...f the inundated area of the Okavango wetland have not previously been mapped. NOAA AVHRR images have successfully been used to classify water in other geographic regions (e.g. Schneider et al., 1985; =-=Harris and Mason, 1989-=-; Prata, 1990; Birkett, 2000). In this Okavango study, nearly 3000 AVHRR images from the period 1985-2000 were used. One scene for every 10-day period was manually selected for water versus land class...

Citation Context

...ecovered. The areal results are in general lower than the size quoted in the literature. The quoted size of the Okavango wetland varies with a range of 12 000 to 16 000 km 2 (cf. Ellery et al., 1991; =-=McCarthy, 1993-=-; Gieske, 1997; Ellery and Ellery, 1997; Ashton and Manley, 1999). These figures are crude average estimates of the actual size, and the large difference in size probably depends on whether or not the...

Citation Context

... very dry country, future needs may force Namibia to abstract water from the Okavango system. Today, Namibia uses approximately 0.05% of the mean annual flow in the Okavango River and Botswana 0.04% (=-=Ashton, 2000-=-). The upstream countries Namibia and Angola are not abstracting large quantities, but are entitled (as any country) to abstract water from water systems which are riparian to them, according to inter...

Citation Context

...drological modelling effort using this data is reported in Bauer et al. (2002a,b) with encouraging preliminary results. The island data set is being used for studies of the salt balance in the Delta (=-=Bauer et al., 2002-=-c). Future possible studies include analysis of spatial distribution of the inundated area compared to precipitation in the catchment and in the Delta. The analysis of vegetation dynamics presented in...

Citation Context

...ed contextual classification method (for examples of rule based classifications, see e.g. Robinson and Frank, 1987; Argialas and Harlow, 1990; Srinivasan and Richards, 1993; Dymond and Luckman, 1994; =-=Chmiel and Gumbricht, 1996-=-; Lein and Lemons, 1997; Houhoulis and Michener, 2000). Ringrose et al. (1988) used visual and digital analysis of Landsat MSS data to differentiate ecological zones of the Okavango, albeit in 250 m r...

Citation Context

...d (Schwarz, 1918; 1920; Du Toit, 1927; Wellington, 1948; Standish-White, 1972; UNDP, 1976 cit. McCarthy et al., 1998a). A much debated pipeline from the Okavango River to Grootfontein in Namibia (cf. =-=CSIR, 1997-=-) seems to have been put on hold, but as Namibia is a very dry country, future needs may force Namibia to abstract water from the Okavango system. Today, Namibia uses approximately 0.05% of the mean a...

Citation Context

... main regions defined by their hydrological regime: the Panhandle where the Okavango River enters the Delta; the permanent swamps; the seasonal swamps; the islands and sandveld tongues (Wilson, 1973; =-=Ellery and Ellery, 1997-=-); and the occasionally flooded swamps. These regions are referred to as “ physiographic regions” throughout this thesis (Figure 5). Figure 5. Physiographic regions of the Okavango Delta. The flooding...

Citation Context

...t least temporarily recovered. The areal results are in general lower than the size quoted in the literature. The quoted size of the Okavango wetland varies with a range of 12 000 to 16 000 km 2 (cf. =-=Ellery et al., 1991-=-; McCarthy, 1993; Gieske, 1997; Ellery and Ellery, 1997; Ashton and Manley, 1999). These figures are crude average estimates of the actual size, and the large difference in size probably depends on wh...

Citation Context

...od classification did not work out on its own in this study, and it is clear that contextual rules can improve classifications in fragmented landscapes, as supported by this study and by others (e.g. =-=Gumbricht et al., 1995-=-; Gumbricht et al., 1996). Table 3. Ecoregion classification scheme; vegetation classes and examples of species within each class. Ecoregions / land cover classes River / Madiba / Backswamp lakes Perm...

Citation Context

...t work out on its own in this study, and it is clear that contextual rules can improve classifications in fragmented landscapes, as supported by this study and by others (e.g. Gumbricht et al., 1995; =-=Gumbricht et al., 1996-=-). Table 3. Ecoregion classification scheme; vegetation classes and examples of species within each class. Ecoregions / land cover classes River / Madiba / Backswamp lakes Permanent swamp communities ...

Citation Context

...anhandle, which is the entry channel into the Okavango Delta (Figure 4). The Delta surface is very flat with an elevation difference of approximately 60 metres between the northern and southern tips (=-=Gumbricht et al., 2002-=-).sFigure 3. The Okavango River in the Panhandle. Photo T. Gumbricht Figure 4. The Okavango Delta, Botswana. The maps are projected to S UTM 34, using the Cape datum. The coordinates are given in km i...

Citation Context

...997) and McCarthy et al. (1993a), and the seasonal flood by McCarthy et al. (1998a). Studies of the surrounding Kalahari have been more abundant (e.g. Ringrose et al., 1990, 1991, 1998, 1999a, 1999b; =-=Gustafsson, 1994-=-; Vanderpost et al., 1998) and research within the ongoing SAFARI 2000 regional science initiative (Swap et al., 2000) are currently adding to the volume vi .sScientific problem The Okavango Delta is ...

Citation Context

...n index is the Normalised Difference Vegetation Index (NDVI) (Rouse et al., 1973 cit. Lawrence and Ripple, 1998), but many other algorithms can be found in the literature (cf. Crist and Cicone, 1984; =-=Hall-Könyves, 1988-=-; Huete, 1988; Running and Coughlan, 1988; Nemani et al., 1993a; Filella and Penuelas, 1994; Qi et al., 1994; Danson and Plummer, 1995; McCarthy, 1996; Yoshioka et al., 2000; Qi et al., 2000). Ecoregi...

Citation Context

...f rule based classifications, see e.g. Robinson and Frank, 1987; Argialas and Harlow, 1990; Srinivasan and Richards, 1993; Dymond and Luckman, 1994; Chmiel and Gumbricht, 1996; Lein and Lemons, 1997; =-=Houhoulis and Michener, 2000-=-). Ringrose et al. (1988) used visual and digital analysis of Landsat MSS data to differentiate ecological zones of the Okavango, albeit in 250 m resolution. In such coarse resolution, many of the isl...

Citation Context

...try) to abstract water from water systems which are riparian to them, according to international law and the Southern African Development Community (SADC) Protocol on shared water systems (ILA, 1966; =-=ILC, 1994-=-; SADC, 1995 cit. Ashton, 2000). The civil war in Angola has so far prevented large-scale water resources development on the Quito and Cubango rivers, but it seems unclear what pace development will t...

Citation Context

...n the literature (cf. Crist and Cicone, 1984; Hall-Könyves, 1988; Huete, 1988; Running and Coughlan, 1988; Nemani et al., 1993a; Filella and Penuelas, 1994; Qi et al., 1994; Danson and Plummer, 1995; =-=McCarthy, 1996-=-; Yoshioka et al., 2000; Qi et al., 2000). Ecoregion classification (Papers I and IV), vegetation dynamics (grazing pressure) (Paper I), surface temperature estimations (Paper III). Soil and canopy mo...

Citation Context

...but some aspects will be brought up as a brief background. Several large-scale water abstraction schemes have been planned for the Okavango through the years, but none have thus far been implemented (=-=Schwarz, 1918-=-; 1920; Du Toit, 1927; Wellington, 1948; Standish-White, 1972; UNDP, 1976 cit. McCarthy et al., 1998a). A much debated pipeline from the Okavango River to Grootfontein in Namibia (cf. CSIR, 1997) seem...

Citation Context

...und. Several large-scale water abstraction schemes have been planned for the Okavango through the years, but none have thus far been implemented (Schwarz, 1918; 1920; Du Toit, 1927; Wellington, 1948; =-=Standish-White, 1972-=-; UNDP, 1976 cit. McCarthy et al., 1998a). A much debated pipeline from the Okavango River to Grootfontein in Namibia (cf. CSIR, 1997) seems to have been put on hold, but as Namibia is a very dry coun...

Citation Context

...hari have been more abundant (e.g. Ringrose et al., 1990, 1991, 1998, 1999a, 1999b; Gustafsson, 1994; Vanderpost et al., 1998) and research within the ongoing SAFARI 2000 regional science initiative (=-=Swap et al., 2000-=-) are currently adding to the volume vi .sScientific problem The Okavango Delta is a dynamic ecosystem, with variations in water flow and a continuous remoulding of the surface by sediment transport p...

Citation Context

...le water abstraction schemes have been planned for the Okavango through the years, but none have thus far been implemented (Schwarz, 1918; 1920; Du Toit, 1927; Wellington, 1948; Standish-White, 1972; =-=UNDP, 1976-=- cit. McCarthy et al., 1998a). A much debated pipeline from the Okavango River to Grootfontein in Namibia (cf. CSIR, 1997) seems to have been put on hold, but as Namibia is a very dry country, future ...

Citation Context

...et al. (1993a), and the seasonal flood by McCarthy et al. (1998a). Studies of the surrounding Kalahari have been more abundant (e.g. Ringrose et al., 1990, 1991, 1998, 1999a, 1999b; Gustafsson, 1994; =-=Vanderpost et al., 1998-=-) and research within the ongoing SAFARI 2000 regional science initiative (Swap et al., 2000) are currently adding to the volume vi .sScientific problem The Okavango Delta is a dynamic ecosystem, with...

Citation Context

...as a brief background. Several large-scale water abstraction schemes have been planned for the Okavango through the years, but none have thus far been implemented (Schwarz, 1918; 1920; Du Toit, 1927; =-=Wellington, 1948-=-; Standish-White, 1972; UNDP, 1976 cit. McCarthy et al., 1998a). A much debated pipeline from the Okavango River to Grootfontein in Namibia (cf. CSIR, 1997) seems to have been put on hold, but as Nami...

Citation Context

...ided into five main regions defined by their hydrological regime: the Panhandle where the Okavango River enters the Delta; the permanent swamps; the seasonal swamps; the islands and sandveld tongues (=-=Wilson, 1973-=-; Ellery and Ellery, 1997); and the occasionally flooded swamps. These regions are referred to as “ physiographic regions” throughout this thesis (Figure 5). Figure 5. Physiographic regions of the Oka...