170 research outputs found
Sustainable groundwater use, the capture principle, and adaptive management
The purpose of this paper is to review the case for using ‘capture’ rather than recharge as the conceptual basis for sustainable groundwater use in South Africa. Capture refers to the sum of the increase in recharge and decrease in discharge brought about by pumping. Definitions of sustainability are reviewed, and the capture process is outlined. Implications for using the capture principle in the implementation of the NWA are discussed, and adaptive management is proposed as an appropriate management approach. Implications for groundwater monitoring are also discussed. Case studies are described that support the need for adaptive management and the application of the capture principleDepartment of HE and Training approved lis
Groundwater discharges to aquatic ecosystems associated with the Table Mountain Group (TMG) aquifer: a conceptual model
This paper reports on a conceptual model that was developed to describe the different groundwater discharge ‘types’ from
the Table Mountain Group (TMG) aquifer, that contributes to the different components of the flow regime in each of the recognised river reaches for streams and rivers associated with the TMG. This model integrates hydrogeological, ecological and
geomorphological understandings into an ecohydrological perspective linking ground- and surface water systems. Through
geospatial intersections of existing GIS layers a GIS model was also developed to highlight the quaternary catchments containing sensitive aquatic ecosystems that could be vulnerable to groundwater use from the TMG. The conceptual model demonstrates the intimate link between groundwater from the TMG aquifer and aquatic ecosystems in the mountain and foothill reaches of streams and rivers in the Cape Folded Mountains in particular. It also identifies
two primary zones of interaction between groundwater and surface water in the TMG, namely, the ‘TMG aquifer daylight-
domain’, located in the recharge zone, and the ‘TMG aquifer surface water interface-domain’, located at the discharge end of
the aquifer. The conceptual model clearly indicates the difference between real groundwater, and perceived groundwater contributions to streamflow in the TMG. It is the lower flows of the flow regime that will be most vulnerable to groundwater use from
the TMG aquifer in the ‘TMG aquifer daylight-domain’, which are unfortunately also the most important flows from an
ecological perspective. However, any groundwater use from the TMG aquifer will also affect the discharge end of the aquifer,
located far from the higher elevation recharge areas, or the point of groundwater abstraction, in lowland settings in the ‘TMG
aquifer surface water interface-domain’. The GIS model integrated the conceptual understanding into a management tool by highlight all quaternary catchments
associated with TMG containing sensitive aquatic ecosystems and gave the variable vulnerability for each.Web of Scienc
Pools "on the rocks" : freshwater rock pools as model system in ecological and evolutionary research
Rock pools inarguably exhibit a number of characteristics which make them attractive as a model system in ecological and evolutionary research. They are usually small, pristine, clearly delineated and structurally simple systems that occur on a global scale. They facilitate the quantification of important population and community structuring processes which are often hard or impossible to quantify in larger more complex systems. Basic properties and spatial configuration of rock pools also closely resemble theoretical metapopulation and metacommunity models. Due to the simple morphometry of rock pool basins and the lack of any groundwater interactions, rock pool hydrologies are simple allowing to reliably reconstruct the disturbance regime against which patterns of variation in life histories, population genetics, species diversity and community structure can be interpreted.Sin lugar a dudas las pozas en rocas presentan numerosas caracterÃsticas que las hacen atractivas para su uso como sistema modelo en la investigación evolutivo-ecológica. Normalmente son sistemas vÃrgenes de pequeño tamaño, estructuralmente sencillos y claramente delineados, que se encuentran a escala global. Permiten la cuantificación de importantes procesos estructuradores de poblaciones y comunidades que, a menudo, son muy difÃciles o imposibles de cuantificar en sistemas mayores más complejos. Las propiedades básicas y la configuración espacial de las pozas en rocas también muestran una estrecha semejanza con los modelos teóricos de metapoblación y metacomunidad. Debido a la morfometrÃa simple de las cubetas de estas pozas y a la carencia de interacciones con las aguas subterráneas, las hidrologÃas de estas pozas son de poca complejidad, lo que permite reconstruir con fiabilidad el régimen de perturbación determinante de los patrones de variación de los ciclos de vida de los organismos, de la genética de poblaciones, diversidad de especies y estructura de comunidades
Application of the rainfall infiltration breakthrough (RIB) model for groundwater recharge estimation in west coastal South Africa
Recharge estimation in arid and semi-arid areas is very challenging. The chloride mass balance method applied in western
South Africa fails to provide reliable recharge estimates near coastal areas. A relationship between rainfall events and water
level fluctuations (WLF) on a monthly basis was proposed in the rainfall infiltration breakthrough (RIB) model for the
purpose of groundwater recharge estimation. In this paper, the physical meaning of parameters in the CRD and previous
RIB models is clarified, and the RIB model is reviewed with the algorithm improved to accommodate various time scales,
namely, daily, monthly and annual scales. Recharge estimates on a daily and monthly basis using the revised RIB approach
in 2 study areas, one in a sandy alluvial aquifer (Riverlands) and the other in the Table Mountain Group (TMG) shallow
unconfined aquifer (Oudebosch), are presented, followed by sensitivity analysis. Correlation analysis between rainfall
and observed WLF data at daily scale and monthly scale, together with recharge estimates obtained from other methods,
demonstrates that the RIB results using monthly data are more realistic than those for daily data, when using long time
series. Scenarios using the data from Oudebosch with different rainfall and groundwater abstraction inputs are simulated to
explore individual effects on water levels as well as recharge rate estimated on a daily basis. The sensitivity analysis showed
that the recharge rate by the RIB model is specifically sensitive to the parameter of specific yield; therefore, the accurate
representative specific yield of the aquifer needs to be selected with caution. The RIB model demonstrated in these two cases
can be used to estimate groundwater recharge with sufficiently long time series of groundwater level and rainfall available in
similar regions. In summary, the RIB model is best suited for shallow unconfined aquifers with relatively lower transmissiv
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ity; the utility of the RIB model for application in different climatic areas under different hydrogeological conditions needs
to be further explored.Web of Scienc
Long Distance Dispersal of Zooplankton Endemic to Isolated Mountaintops - an Example of an Ecological Process Operating on an Evolutionary Time Scale
Recent findings suggest a convergence of time scales between ecological and evolutionary processes which is usually explained in terms of rapid micro evolution resulting in evolution on ecological time scales. A similar convergence, however, can also emerge when slow ecological processes take place on evolutionary time scales. A good example of such a slow ecological process is the colonization of remote aquatic habitats by passively dispersed zooplankton. Using variation at the protein coding mitochondrial COI gene, we investigated the balance between mutation and migration as drivers of genetic diversity in two Branchipodopsis fairy shrimp species (Crustacea, Anostraca) endemic to remote temporary rock pool clusters at the summit of isolated mountaintops in central South Africa. We showed that both species colonized the region almost simultaneously c. 0.8 My ago, but exhibit contrasting patterns of regional genetic diversity and demographic history. The haplotype network of the common B. cf. wolfi showed clear evidence of 11 long distance dispersal events (up to 140 km) with five haplotypes that are shared among distant inselbergs, as well as some more spatially isolated derivates. Similar patterns were not observed for B. drakensbergensis presumably since this rarer species experienced a genetic bottleneck. We conclude that the observed genetic patterns reflect rare historic colonization events rather than frequent ongoing gene flow. Moreover, the high regional haplotype diversity combined with a high degree of haplotype endemicity indicates that evolutionary- (mutation) and ecological (migration) processes in this system operate on similar time scales
Conservation status of large branchiopods in the Western Cape, South Africa
Temporary wetlands are an ecologically and economically important habitat in South Africa. They harbor large branchiopods, known to be flagship species of nonpermanent aquatic habitats, and sensitive to land use changes. In this study we review the current status of large branchiopods in the Western Cape, a South African province subject to increasing agriculture and urbanization. We studied the species diversity and distribution of large branchiopods by sampling 58 temporary wetlands in an area covering about 30% of the Western Cape. Information obtained from field samples was supplemented by incubating resting egg banks from the sampled wetlands. Our data were compared with all known distribution records for large branchiopods in the target region. Based on this combined information, the International Union for the Conservation of Nature and Natural Resources (IUCN) Red List category was assessed for each species. Four of the eight large branchiopod species known to occur in the sampling area were collected. Of all wetlands sampled, 40% harbored large branchiopods. Most anostracan populations were small, and species co-occurred in only one wetland. From the entire Western Cape, 14 species have been recorded in the past. Two of these are already included in the IUCN Red List. Insufficient data are available to determine the IUCN Red Data Category of six other species. A large variation in the telsonic appendages of S. dendyi was found across the studied area. In view of possible ongoing speciation and subsequent radiation, individual populations need protection. Since little information is available, it is difficult to evaluate recent changes in the conservation status of large branchiopods. Their populations are currently very low and have probably diminished in the last few decades. More knowledge about the functioning of temporary systems is needed to manage these vulnerable habitats and conserve their threatened species.Web of Scienc
Toward a Global Phylogeny of the “Living Fossil" Crustacean Order of the Notostraca
Tadpole shrimp (Crustacea, Notostraca) are iconic inhabitants of temporary aquatic habitats worldwide. Often cited as prime examples of evolutionary stasis, surviving representatives closely resemble fossils older than 200 mya, suggestive of an ancient origin. Despite significant interest in the group as ‘living fossils’ the taxonomy of surviving taxa is still under debate and both the phylogenetic relationships among different lineages and the timing of diversification remain unclear. We constructed a molecular phylogeny of the Notostraca using model based phylogenetic methods. Our analyses supported the monophyly of the two genera Triops and Lepidurus, although for Triops support was weak. Results also revealed high levels of cryptic diversity as well as a peculiar biogeographic link between Australia and North America presumably mediated by historic long distance dispersal. We concluded that, although some present day tadpole shrimp species closely resemble fossil specimens as old as 250 mya, no molecular support was found for an ancient (pre) Mesozoic radiation. Instead, living tadpole shrimp are most likely the result of a relatively recent radiation in the Cenozoic era and close resemblances between recent and fossil taxa are probably the result of the highly conserved general morphology in this group and of homoplasy
Macroinvertebrates
this book chapter is published in Ecology to Conservation Management ,a book called Fundamentals of Tropical Freshwater Wetlands page number 307 to 336This chapter introduces the diversity and community composition of macroinvertebrates occurring in wetlands with emphasis on the permanent and temporary wetlands in the Afrotropical region of the world. The chapter explores factors shaping the composition of macroinvertebrate communities of the permanent and temporary habitats, and the structuring role of dispersal mechanisms. The diversity and composition of macroinvertebrates is contrasted between different regions of the world and between permanent and temporary wetland types. Furthermore, the role of macroinvertebrates as indicators of habitat quality, ecosystem functions, and services provided by macroinvertebrates in wetlands is explored. Finally, the threats to macroinvertebrates in wetlands are highlighted
Remote sensing and wetland ecology: a South African case study
Remote sensing offers a cost efficient means for identifying and monitoring
wetlands over a large area and at different moments in time. In this study, we aim at
providing ecologically relevant information on characteristics of temporary and permanent
isolated open water wetlands, obtained by standard techniques and relatively cheap
imagery. The number, surface area, nearest distance, and dynamics of isolated temporary
and permanent wetlands were determined for the Western Cape, South Africa. Open water
bodies (wetlands) were mapped from seven Landsat images (acquired during 1987 – 2002)
using supervised maximum likelihood classification.
This study has indicated that ecologically relevant data can
be generated for the larger wetlands through relatively cheap imagery and standard
techniques, despite the relatively low resolution of Landsat and Envisat imagery. For the
characterisation of very small wetlands, high spatial resolution optical or radar images are
needed. This study exemplifies the benefits of integrating remote sensing and ecology and
hence stimulates interdisciplinary research of isolated wetlands
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