19 research outputs found
Assessment of impacts of climate change on surface water availability using coupled SWAT and WEAP models: case of upper Pangani River Basin, Tanzania
This study was designed to investigate the dynamics of current and future
surface water availability for different water users in the upper Pangani
River Basin under changing climate. A multi-tier modeling technique was used
in the study, by coupling the Soil and Water Assessment Tool (SWAT) and Water
Evaluation And Planning (WEAP) models, to simulate streamflows under climate
change and assess scenarios of future water availability to different
socio-economic activities by year 2060. Six common Global Circulation Models
(GCMs) from WCRP-CMIP3 with emissions Scenario A2 were selected. These are
HadCM3, HadGEM1, ECHAM5, MIROC3.2MED, GFDLCM2.1 and CSIROMK3. They were
downscaled by using LARS-WG to station scale. The SWAT model was calibrated
with observed data and utilized the LARS-WG outputs to generate future
streamflows before being used as input to WEAP model to assess future water
availability to different socio-economic activities. GCMs results show future
rainfall increase in upper Pangani River Basin between 16–18 % in 2050s
relative to 1980–1999 periods. Temperature is projected to increase by an
average of 2 °C in 2050s, relative to baseline period. Long-term
mean streamflows is expected to increase by approximately 10 %. However,
future peak flows are estimated to be lower than the prevailing average peak
flows. Nevertheless, the overall annual water demand in Pangani basin will
increase from 1879.73 Mm3 at present (2011) to 3249.69 Mm3 in the
future (2060s), resulting to unmet demand of 1673.8 Mm3 (51.5 %).
The impact of future shortage will be more severe in irrigation where
71.12 % of its future demand will be unmet. Future water demands of
Hydropower and Livestock will be unmet by 27.47 and 1.41 % respectively.
However, future domestic water use will have no shortage. This calls for
planning of current and future surface water use in the upper Pangani River
Basin
Critical review of SWAT applications in the upper Nile basin countries
The Soil and Water Assessment Tool (SWAT) is an integrated river basin model that is widely applied within the Nile basin. Up to date, more than 20 peer-reviewed papers describe the use of SWAT for a variety of problems in the upper Nile basin countries, such as erosion modelling, land use and climate change impact modelling and water resources management. The majority of the studies are focused on locations in the tropical highlands in Ethiopia and around Lake Victoria. The popularity of SWAT is attributed to the fact that the tool is freely available and that it is readily applicable through the development of geographic information system (GIS) based interfaces and its easy linkage to sensitivity, calibration and uncertainty analysis tools. The online and free availability of basic GIS data that are required for SWAT made its applicability more straightforward even in data-scarce areas. However, the easy use of SWAT may not always lead to appropriate models which is also a consequence of the quality of the available free databases in these regions. In this paper, we aim at critically reviewing the use of SWAT in the context of the modelling purpose and problem descriptions in the tropical highlands of the Nile basin countries. To evaluate the models that are described in journal papers, a number of criteria are used to evaluate the model set-up, model performances, physical representation of the model parameters, and the correctness of the hydrological model balance. On the basis of performance indicators, the majority of the SWAT models were classified as giving satisfactory to very good results. Nevertheless, the hydrological mass balances as reported in several papers contained losses that might not be justified. Several papers also reported the use of unrealistic parameter values. More worrying is that many papers lack this information. For this reason, most of the reported SWAT models have to be evaluated critically. An important gap is the lack of attention that is given to the vegetation and crop processes. None of the papers reported any adaptation to the crop parameters, or any crop-related output such as leaf area index, biomass or crop yields. A proper simulation of the land cover is important for obtaining correct runoff generation, evapotranspiration and erosion computations. It is also found that a comparison of SWAT applications on the same or similar case study but by different research teams and/or model versions resulted in very different results. It is therefore recommended to find better methods to evaluate the representativeness of the distributed processes and parameters (especially when land use studies are envisaged) or predictions of the future through environmental changes. The main recommendation is that more details on the model set-up, the parameters and outputs should be provided in the journal papers or supplementary materials in order to allow for a more stringent evaluation of these models
Critical review of SWAT applications in the upper Nile basin countries
The Soil and Water Assessment Tool (SWAT) is an integrated river basin model that is widely applied within the Nile basin. Up to date, more than 20 peer-reviewed papers describe the use of SWAT for a variety of problems in the upper Nile basin countries, such as erosion modelling, land use and climate change impact modelling and water resources management. The majority of the studies are focused on locations in the tropical highlands in Ethiopia and around Lake Victoria. The popularity of SWAT is attributed to the fact that the tool is freely available and that it is readily applicable through the development of geographic information system (GIS) based interfaces and its easy linkage to sensitivity, calibration and uncertainty analysis tools. The online and free availability of basic GIS data that are required for SWAT made its applicability more straightforward even in data-scarce areas. However, the easy use of SWAT may not always lead to appropriate models which is also a consequence of the quality of the available free databases in these regions. In this paper, we aim at critically reviewing the use of SWAT in the context of the modelling purpose and problem descriptions in the tropical highlands of the Nile basin countries. To evaluate the models that are described in journal papers, a number of criteria are used to evaluate the model set-up, model performances, physical representation of the model parameters, and the correctness of the hydrological model balance. On the basis of performance indicators, the majority of the SWAT models were classified as giving satisfactory to very good results. Nevertheless, the hydrological mass balances as reported in several papers contained losses that might not be justified. Several papers also reported the use of unrealistic parameter values. More worrying is that many papers lack this information. For this reason, most of the reported SWAT models have to be evaluated critically. An important gap is the lack of attention that is given to the vegetation and crop processes. None of the papers reported any adaptation to the crop parameters, or any crop-related output such as leaf area index, biomass or crop yields. A proper simulation of the land cover is important for obtaining correct runoff generation, evapotranspiration and erosion computations. It is also found that a comparison of SWAT applications on the same or similar case study but by different research teams and/or model versions resulted in very different results. It is therefore recommended to find better methods to evaluate the representativeness of the distributed processes and parameters (especially when land use studies are envisaged) or predictions of the future through environmental changes. The main recommendation is that more details on the model set-up, the parameters and outputs should be provided in the journal papers or supplementary materials in order to allow for a more stringent evaluation of these models
Role of potyviruses in synergistic interaction leading to maize lethal necrotic disease on maize
International Journal of Current Microbiology and Applied SciencesSynergistic interactions among pathogenic viruses are common in plants.
Though not all, but a number of reported cases involving such interactions
have a potyvirus partner during co-infection. The presence of the potyvirus
group seems to favor its own multiplication on host and multiplication of a
co-infecting partner. In this review, some characteristics favoring higher
pathogenesis have been discussed using maize lethal necrosis (MLN)-
causing viruses namely Maize chlorotic mottle virus (MCMV) and its
synergistic potyvirus, Sugarcane mosaic virus (SCMV). A comprehensive
discussion on the role of potyvirus in the synergism has been presented to
show that in MLN and similar synergisms - the machinery for induction,
transmission and colonization of the host is catalysed by the potyvirus and
not the co-infecting viral partner which otherwise seems to be the most
virulent in the synergism-based diseases such as MLN disease in maize.
Furthermore, the effect of MLN to food security and areas for future
research for Africa has been discussed in this review
Role of potyviruses in synergistic interaction leading to maize lethal necrotic disease on maize
International Journal of Current Microbiology and Applied SciencesSynergistic interactions among pathogenic viruses are common in plants.
Though not all, but a number of reported cases involving such interactions
have a potyvirus partner during co-infection. The presence of the potyvirus
group seems to favor its own multiplication on host and multiplication of a
co-infecting partner. In this review, some characteristics favoring higher
pathogenesis have been discussed using maize lethal necrosis (MLN)-
causing viruses namely Maize chlorotic mottle virus (MCMV) and its
synergistic potyvirus, Sugarcane mosaic virus (SCMV). A comprehensive
discussion on the role of potyvirus in the synergism has been presented to
show that in MLN and similar synergisms - the machinery for induction,
transmission and colonization of the host is catalysed by the potyvirus and
not the co-infecting viral partner which otherwise seems to be the most
virulent in the synergism-based diseases such as MLN disease in maize.
Furthermore, the effect of MLN to food security and areas for future
research for Africa has been discussed in this review