Browsing by Author "Mbillinyi, B. P."

Now showing 1 - 3 of 3

Application of self-organizing-maps technique in downscaling GCMs climate change projections for Same, Tanzania
(2010) Tumbo, S. D.; Mpeta, E.; Mbillinyi, B. P.; Kahimba, F. C.; Mahoo, H. F.; Tadross, M.
High resolution surface climate variables are required for end-users in climate change impact studies; however, information provided by Global Climate Models (GCMs) has a coarser resolution. Downscaling techniques such as that developed at the University of Cape Town, which is based on Self-Organizing Maps (SOMs) technique, can be used to downscale the coarse-scale GCM climate change projections into finer spatial resolutions; but that must be combined with verification. The SOM downscaling technique was employed to project rainfall and temperature changes for 2046-2065 and 2080-2100 periods for Same, Tanzania. This model was initially verified using downscaled NCEP reanalysis and observed climate data set between 1979 and 2004, and between NCEP reanalysis and GCM controls (1979 - 2000). After verification, the model was then used to downscale climate change projections of four GCMs for 2046-2065 (future-A) and 2080-2100 (future-B) periods. These projections were then used to compute changes in the climate variables by comparing future-A and B to the control period (1961-2000). Verification results indicated that the NCEP downscaled climate data compared well with the observed data. Also, comparison between NCEP downscaled and GCM downscaled showed that all the four GCM models (CGCM, CNRM, IPSL, and ECHAM) compared well with the NCEP downscaled temperature and rainfall data. Future projections (2046-2065) indicated 56 mm and 42 mm increase in seasonal total rainfall amounts for March-April-May (MAM) and October-November-December (OND) (23% and 26% increase), respectively; and a temperature increase of about 2°C for both seasons. Furthermore, it was found that during MAM there will be a decrease in dry spells by 2 days, and an increase in seasonal length by 8 days, while for OND, there will be also 2 days decrease in dry spells, and 40 days increase in the seasonal length. The results for future-B shows a 4°C rise in temperature, and 46.5% and 35.8% increase in rainfall for MAM and OND, respectively. The results imply a better climatic future for the area because of the increase in the amount of rainfall and decrease in dry spells. However, it is suggested that further investigations are required to see if the projected changes will have real positive effects in agricultural production and also identify better agronomic practices that will take advantage of the opportunities.
Determination of suitability levels for important factors for identification of potential sites for rainwater harvesting
(2016) Tumbo, S. D.; Mbillinyi, B. P.; Mahoo, H. F.; Mkiramwinyi, F. O.
Indigenous and scientific knowledge for locating potential sites for water harvesting technologies do exists, however, a simple and integrated tool to assist farmers’ support agencies, is missing. A geographic information system (GIS)-based decision support system (DSS) can be a valuable tool for such a task. However, pre-requisite for such DSS are the factors and their suitability levels, which are not well developed. This paper focused on development of suitability levels for most important factors/parameters for identification of such sites, which are soil texture, soil depth, drainage, topography and land use or cover. Specific suitability levels were obtained using both the analysis of existing RWH technology at Makanya river catchment and through literature review. Results of field survey together with literature review showed that suitability levels of factors differ with different RWH technologies. For example, suitable levels/areas for water reservoirs (ndiva) are steep slopes (>30o) with clay soils whereas suitable sites for stone terraces are moderately steep slopes (18o – 30o) with sandy loam soils. It was also found that most RWH technologies are located at a distance between 0 and 125m from cropland.
Identification of suitable indices for identification of potential sites for rainwater harvesting
(Tanzania Journal of Agricultural Sciences, 2014) Tumbo, S. D.; Mbillinyi, B. P.; Mahoo, H. F.; Mkilamwinyi, F. O.
Although indigenous and scientific knowledge for locating potential sites for water harvesting technologies do exist, a simple and integrated tool to assist farmers’ support agencies, is missing. A geographic information system (GIS)-based decision support system (DSS) can be a valuable tool for such a task. However, key to such DSS are the factors and their suitability levels, which are not well developed. This study therefore focused on the development of suitability levels for most important factors/parameters for identification of such sites. The factors included rainfall, soil texture, soil depth, drainage, topography and land use or cover. Specific suitability levels were derived from analysis of existing RWH technologies in Makanya river catchment. Results showed that suitability levels of factors differ with different RWH technologies. Suitable areas for ndiva is on steep slopes (18o-30o) with clay soils, stone terraces is on moderately steep slopes (10o – 18o) with sandy clay loam soils, bench terraces (5o-18o slopes, clay or silt clay soils) and “boda” (2o-5o slopes, slit clay or clay soils). It was also found that ndiva, “boda”, stone terrace and bench terrace are located at a distance within 125m from cropland. Testing of the developed parameters using ArcView-based DSS framework showed that 81.4% RWH technologies were located in the very high and high suitability levels, indicating the usefulness of the developed parameters and their suitability levels.