19 research outputs found
Integrated SASSCAL research to assess and secure current and future water resources in Southern Africa
No full textNo abstract available
The SASSCAL contribution to climate observation, climate data management and data rescue in Southern Africa
No full textA major task of the newly established "Southern African Science Service Centre for Climate Change and Adaptive Land Management" (SASSCAL; www.sasscal.org) and its partners is to provide science-based environmental information and knowledge which includes the provision of consistent and reliable climate data for Southern Africa. Hence, SASSCAL, in close cooperation with the national weather authorities of Angola, Botswana, Germany and Zambia as well as partner institutions in Namibia and South Africa, supports the extension of the regional meteorological observation network and the improvement of the climate archives at national level. With the ongoing rehabilitation of existing weather stations and the new installation of fully automated weather stations (AWS), altogether 105 AWS currently provide a set of climate variables at 15, 30 and 60 min intervals respectively. These records are made available through the SASSCAL WeatherNet, an online platform providing near-real time data as well as various statistics and graphics, all in open access. This effort is complemented by the harmonization and improvement of climate data management concepts at the national weather authorities, capacity building activities and an extension of the data bases with historical climate data which are still available from different sources. These activities are performed through cooperation between regional and German institutions and will provide important information for climate service related activities
Bayesian trend analysis in annual rainfall total, duration and maximum in the Kara River basin (West Africa)
No full textStudy region: The Kara River basin, northern Togo and Benin, West Africa.
Study focus: This study investigated long-term trends in annual rainfall (annRAIN), annual rainfall duration (DURATION) and annual maximum rainfall (MAXAN) for seven stations between 1950 and 2010. A Bayesian trend analysis was performed by fitting the Lognormal, Normal and Generalized Extreme Value (GEV) distributions to annRAIN, DURATION and MAXAN, respectively, with a time covariate for both the location and scale parameters. Spatio-temporal variation of the mean decadal rainfall and the seasonality of the mean monthly rainfall were also analyzed.
New hydrological insights for the region: The results indicate that the interannual variability of annRAIN is decreasing over time at all stations, and the average annRAIN is also markedly decreasing at several stations. However, DURATION is increasing at most stations suggesting that in those parts of the basin where annRAIN is decreasing, rainfall occurs more frequently but with less intensity. For MAXAN, evidence for decreasing trend is found in two stations, and for increasing trend in one station. It is also shown that the peak of the rainy season shifted from September to August since the 1980s. Furthermore, changes in the spatio-temporal distribution of the mean decadal rainfall are also observed. This study provides valuable new insights into trends affecting rainfall variables in the Kara River basin
A comparative analysis of the PRMS and J2000 hydrological models applied to the Sandspruit Catchment (Western Cape, South Africa).
No full textPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]
Initial hydrological modelling to assess impacts of different land uses on process hydrology in a small-scale semi-arid catchment in the Western Cape Province, South Africa
No full textPlease help us populate SUNScholar with the post print version of this article. It can be e-mailed to: [email protected]
Assessment of data uncertainty and plausibility over the Nam Co Region, Tibet
No full textOne of the major challenges for water balance studies in the remote and
mostly ungauged region of the Tibetan Plateau is the lack of suitable and
reliable climate data to drive hydrological models. Ground observations are
rare in the high-mountainous region of the Nam Co basin and only global and
regional gridded climate products are available as model input data, but
these data sets need to be carefully analysed if used as driving force for
hydrological modelling. In this study, various global and regional gridded
data products for temperature and precipitation were compared to assess
spatio-temporal deviations between several data sets. For the comparison
absolute and relative differences of annual and seasonal long-term means
were calculated. Climatic trends were analysed by using the non-parametric
Mann-Kendall trend test. In addition, gridded climate data sets were
compared to meteorological observations in order to evaluate their
plausibility. The comparative statistical analysis showed significant
differences in the magnitude, the seasonality, the spatial pattern and the
trend behaviour of the analysed climate variables, in particular for
precipitation data. The identified inconsistencies underpin the necessity to
quantify the uncertainty of such climate data. Moreover, the presented study
highlights the importance of further research efforts to develop regional
climate data sets with finer resolutions to reduce the model's uncertainty
resulting from climate input data. Such higher resolution is needed for a
sufficient representation of regional topographic and orographic effects in
order to simulate important hydrological processes in mountainous areas like
snow accumulation and melting
Assessing basin heterogeneities for rainfall–runoff modelling of the Okavango River and its transboundary management
No full textThe neighbouring river systems Cubango and Cuito drain the southeastern part of the Angolan Highlands and form the Okavango River after their confluence, thus providing 95% of the Okavango River discharge. Although they are characterised by similar environmental conditions, runoff records indicate remarkable differences regarding the hydrological dynamics. The Cubango River is known for rapid discharges with high peaks and low baseflow whereas the Cuito runoff appears more balanced. These differences are mainly caused by heterogeneous geological conditions or terrain features. The Cubango headwaters are dominated by crystalline bedrock and steeper, v-shaped valleys while the Cuito system is characterised by wide, swampy valleys and thick sand layers, thus attenuating runoff. This study presents model exercises which have been performed to assess and quantify these effects by applying the distributive model J2000g for each sub-basin. The models provide reasonable results representing the spatio-temporal runoff pattern, although some peaks are over- or underestimated, particularly in the Cuito catchment. This is explained by the scarce information on extent and structure of storages, such as aquifers or swamps, in the Cuito system. However, the model results aid understanding of the differences of both tributaries in runoff generation and underpin the importance of floodplains regarding the control of runoff peaks and low flows in the Cuito system. Model exercises reveal that basin heterogeneity needs to be taken into account and must be parameterised appropriately for reliable modelling and assessment of the entire Okavango River basin for managing the water resources of the transboundary Okavango River in a harmonious way
Integrated water management tools supporting future water security and food production in West Africa
No full textNo abstract available
Hydrological system analysis and modelling of the Nam Co basin in Tibet
No full textThe Tibetan Plateau and the adjacent high mountain regions of the Himalayas
play an important role in the global climate dynamic through its impact on
the Asian monsoon system, which in turn is impacting the water resources of
this extremely vulnerable region. To provide further knowledge about the
changing impact of rainfall patterns, spatial and temporal variability of
snow cover contribution, amount of snow and ice melt runoff,
evapotranspiration as well as dynamics of wetlands and permafrost water
balance studies are required. This is of particular importance in terms of
global climate change because of a severe gap in the knowledge of the short,
mid and long term implications on the hydrological system.
This study concentrates on the macroscale catchment of the lake Nam
Co, located at 4718 m a.s.l. at the foot of the Nyainqentanglha Mountains
in central Tibet (30° N, 90° E). The water balance of the
Nam Co basin is dominated by semi-arid climate, snow and ice melt
runoff and high evaporation rates due to the high radiation input and the low
air humidity. The observed temperature rise, glacier retreat, permafrost
decay and lake level increase indicate significant system changes and the
high sensitivity of the Tibetan Plateau on global warming. The development of
a suitable water balance model and its preliminary application was the main
objective of this study. The development was done with the Jena Adaptable
Modelling System JAMS along with existing scientific process components of
the J2000 module library which were partly further developed to reflect the
specific conditions of the high elevation Nam Co basin.
The preliminary modelling exercise based on gridded data from a downscaled
ECHAM5 data set provided reasonable estimates about the important
hydrological water balance components of the Nam Co basin. With the
modelling results the observed lake level rise could be reproduced and it
could be shown that the runoff from the glaciered areas seems to be the most
important component to explain the increasing amount of lake water
Cumulative effects of policy and management actions on ecosystem services. Challenges and methodological approaches in The Future Okavango project
No full textThe Okavango Basin encompasses a wide range of ecosystems and, corresponding to its extension across Angola, Botswana and Namibia, a multitude of communities with diverse socio-economic contexts, that in turn are determined both, by local traditions and regional and national policies. With the river acting as a connecting element, managing the use of natural resources under consideration of conservation issues is a challenging task. The interdisciplinary research project "The Future Okavango" (TFO) aims at contributing to integrated, sustainable land management by providing scientific support to stakeholders from local to national levels. The region under investigation, a system of woodlands, floodplains and extended wetlands is of crucial global importance for biological diversity. Simultaneously it is threatened by rapid transformation through climate change, population growth and anthropogenic over-utilization of natural resources, which may amplify land and water conflicts. The project adopts an approach of mapping and valorising a set of representative ecosystem services and the underlying ecosystem functions. Since these are provided at different spatial and temporal scales, and can show varying properties at different scales, a multi-scale approach is required that covers services from the plot-scale to the full Okavango Basin area. Besides the issue of multi-scale variation, cumulative effects may occur between different processes in both, the spatial and temporal dimension, and causing off-site effects or services being partially determined by past processes. In this paper we identify key issues in the assessment process in a wider conceptual context and describe mapping and assessment procedures. Finally, we introduce the concepts utilized to integrate sectorial assessments of ecosystem services and provide an example of an integrated assessment for a theoretical case study in Northern Namibia
