Adequacy of satellite derived rainfall data for stream flow modeling

Floods are the most common and widespread climate-related hazard on Earth. Flood forecasting can reduce the death toll associated with floods. Satellites offer effective and economical means for calculating areal rainfall estimates in sparsely gauged regions. However, satellite-based rainfall estimates have had limited use in flood forecasting and hydrologic stream flow modeling because the rainfall estimates were considered to be unreliable. In this study we present the calibration and validation results from a spatially distributed hydrologic model driven by daily satellite-based estimates of rainfall for sub-basins of the Nile and Mekong Rivers. The results demonstrate the usefulness of remotely sensed precipitation data for hydrologic modeling when the hydrologic model is calibrated with such data. However, the remotely sensed rainfall estimates cannot be used confidently with hydrologic models that are calibrated with rain gauge measured rainfall, unless the model is recalibrated. G. Artan, J. L. Smith and K. Asante – work performed under USGS contract 03CRCN0001.     

Testing the capability of spectral resolution of the new multispectral sensors on detecting the severity of grey leaf spot disease in maize crop

Abstract

In this study, we tested whether GLS field symptoms on maize can be detected using hyperspectral data re-sampled to WorldView-2, Quickbird, RapidEye and Sentinel-2 resolutions. To achieve this objective, Random Forest algorithm was used to classify the 2013 re-sampled spectra to represent the three identified disease severity categories. Results showed that Sentinel-2, with 13 spectral bands, achieved the highest overall accuracy and kappa value of 84% and 0.76, respectively, while the WorldView-2, with eight spectral bands, yielded the second highest overall accuracy and kappa value of 82% and 0.73, respectively. Results also showed that the 705 and 710 nm red edge bands were the most valuable in detecting the GLS for Sentinel-2 and RapidEye, respectively. On the re-sampled WorldView 2 and Quickbird sensor resolutions, the respective 608 and 660 nm in the yellow and red bands were identified as the most valuable for discriminating all categories of infection.     

Estimating daily streamflow in the Congo Basin using satellite-derived data and a semi-distributed hydrological model

ABSTRACT

The application of remotely-sensed data for hydrological modeling of the Congo Basin is presented. Satellite-derived data, including TRMM precipitation, are used as inputs to drive the USGS Geospatial Streamflow Model (GeoSFM) to estimate daily river discharge over the basin from 1998 to 2012. Physically-based parameterization was augmented with a spatially-distributed calibration that enables GeoSFM to simulate hydrological processes such as the slowing effect of the Cuvette Centrale. The resulting simulated long-term mean of daily flows and the observed flow at the Kinshasa gauge were comparable (40 631 and 40 638 m³/s respectively), in the 7-year validation period (2004–2010), with no significant bias and a Nash-Sutcliffe model efficiency coefficient of 0.70. Modeled daily flows and aggregated monthly river outflows (compared to historical averages) for additional sites confirm the model reliability in capturing flow timing and seasonality across the basin, but sometimes fails to accurately predict flow magnitude. The results of this model can be useful in research and decision-making contexts and validate the application of satellite-based hydrological models driven for large, data-scarce river systems such as the Congo.     

Problems of Artisanal Marine Fishermen in Ghana: The Way Ahead

Marine fishing is an important traditional economic activity of the coastal communities in Ghana and contributes over 80 per cent of the total fish catch. The traditional sector accounts for over 75 per cent of the marine catch. The small-scale artisanal marine fishing communities, which contribute less than 30 per cent of the traditional sector landings, are generally characterised by low levels of production and, hence, low incomes, poor living conditions and chronic indebtedness. Based on field data on artisanal fishing communities in the Ahanta West and Gomoa districts, this paper summarises the chronic problems of artisanal fishermen that perpetuate their precarious existence in the coastal environment. Overcoming the problems of these increasingly marginalised and migrant communities calls for the provision of supplementary employment opportunities, improved social services and the formation of solidarity groups to enhance access to micro credit. These would require technical and management training as well as support services from government and non-governmental organisations (NGOs).     

Towards a pro-community-based water resource management system in Northwest Cameroon: practical evidence and lessons of best practices

This paper examines community-based water supply management (CBWSM) in three rural districts of Northwest Cameroon as well as a review of the literature focusing on some successful community-based natural resource management initiatives in sub-Saharan Africa. Using empirical and secondary data collected through participatory research methods, it is argued that CBWSM has failed to achieve sustainable water supplies in Northwest Cameroon. Findings revealed that centralized control, the prevalence of poverty, passive involvement of public, private and grassroots community has continued to thwart water supplies within these districts. It is important to note that in any natural resource management system, power becomes a crucial factor as it determines who has and does not have access to common-pool resources. This paper argues that argues that strong traditional leadership, resolute devolution, and active participation of rural communities will facilitate and invigorate a platform for capturing the views of diverse user groups and this can bring about a people-centered and community-driven development process. Some aspects of best practice arising from successful case studies in Cameroon can contribute significantly to promoting the development of effective CBWSM in other rural communities with similar characteristics in and out of Cameroon. This will be possible only if rural groups are involved and engaged in the management of their resources while integrating some aspects of best practice.

     

Impact of climate change on streamflow in selected river basins in Ghana

Abstract

This study uses the Soil and Water Assessment Tool (SWAT) and downscaled climate projections from the ensemble of two global climate models (ECHAM4 and CSIRO) forced by the A1FI greenhouse-gas scenario to estimate the impact of climate change on streamflow in the White Volta and Pra river basins, Ghana. The SWAT model was calibrated for the two basins and subsequently driven by downscaled future climate projections to estimate the streamflow for the 2020s (2006–2035) and 2050s (2036–2075). Relative to the baseline, the mean annual streamflow estimated for the White Volta basin for the 2020s and 2050s showed a decrease of 22 and 50%, respectively. Similarly, the estimated streamflow for the 2020s and 2050s for the Pra basin showed a decrease of 22 and 46%, respectively. These results underscore the need to put in place appropriate adaptation measures to foster resilience to climate change in order to enhance water security within the two basins.

Citation Kankam-Yeboah, K., Obuobie, E., Amisigo, B., and Opoku-Ankomah, Y., 2013. Impact of climate change on streamflow in selected river basins in Ghana. Hydrological Sciences Journal, 58 (4), 773–788.