IMPACT ASSESSMENT

The great devastating Sahelian drought that lasted from 1968 - 1975 with a peak in 1973 lefl between 100,000 to 150,000 people dead. Drought disaster is one of the natural disasters that have a long-lasting impact on the lives of people worldwide. Moderate to severe droughts does occur in Tanzania on an annual basis as well as in the seasons. This study has shown the distribution, duration and severity of these droughts. An attempt to relate drought events and crop production

(food and cash crops) was done. Production figures for crops were available for the period 1985 - 1991 from the Ministry of Agriculture of the United Republic of Tanzania.

Results indicate that there was substantial decrease in yields of both cash and food crops when droughts occur. Sorghum, millet and cassava (drought resistant food crops) were not affected much by droughts.

Famine reported in 1975, 1976 and 1984 affecting most parts of country coincided with the drought years. It is likely that these famines were a result of low food production occasioned by deficient rainfall. Since sorghum, millet and cassava production is little affected by drought occurrence, it is recommended that the Government sensitize and encourage farmers to grow these type of cereals as precautionary measure to droughts impacts in the country in the event a drought year is forecasted.

6 Summary

Large areas of the country are affected by droughts either in the annual rainfall or seasonal rainfall.

Droughts were found to be frequent during the seasons in the bimodal region. Droughts were found to occur more frequently in La-Nina years compared to ENS0 years. Persistence of these droughts was not significant at 95% confidence level as shown by the auto-correlation coefficients. The longest drought was found to run five consecutive years representing a return period of 15 years.

The probability of a seven consecutive year’s drought is 2.7% having a corresponding return period of 36 years. Analysis of the annual and seasonal run-sums indicated that the worst drought was

1990 - 1994 in the unimodal region with a deficit of 3 123 mm in 5 years.

Spectral analysis of annual/seasonal rainfall data revealed four significant peaks in the following wavelengths: 2 years, 3-6 years, 9.5 - 12.5 years and 19.0 years. The repetitive alignments of the sun, earth and moon approximately tie with Lamb’s periods of 13.6 and 27.2 years, The ENS0 event is associated with the 3 - 6 year’s wavelength. Wavelengths of 2 years are related to the QBO phenomena.

References

Brooks, C.E.P. and Carruthers, N., 1953: Handbook of Statistical Methods in Meteorology. HMSO, 4 12pp.

Chatfield, C., 1980: The Analysis of Time series. Chapman and hall, London Das, P.K., 1983: Droughts and Famines in India. Mausam. 34, 123-130

Griffiths, J.F., 1972: Climate of Africa. World survey of Climatologv, Vol. 10, Elsevie, Amsterdam.

190

Hastenrath, S., Nicklis, A. and Greischar, L., 1993: Atmospheric - Hydrospheric Mechanisms of Climate Anomalies in Western Equatorial Indian Ocean, Journalof Geophvsical Research Vol. 98. No. C II, 20219 - 20235.

Hastenrath, S. and Greischar, L., 1995: Prediction of the Summer Rainfall over South Africa. Journal of Climate. Vol. 8. No. 6. American Meteorological Society.

Ininda, J., 1984: Spatial and temporal characteristics of drought in Eastern and Southern Africa. MSc Thesis. University of Nairobi

Jerkins, G.M. and Watts, D.G., 1968: Spectral analysis and its applications. Holden - Dav, San Francisco.

Jury, M.R. and MC Queen, C., 1993: Correlation atlas of climatic determinants for Tanzania Kabanda, T.A., 1995: Seasonal and Intra-Seasonal Dynamics and Precursors of Rainfall over Northern Tanzania. M. SC. Thesis, University of Cape Town.

Kavishe, M.M. and Matitu, M.R., 1993: Drought frequencies over Southeast of Lake Victoria Basin of Tanzania. Paper presented at the First African Meteorological Societv Meeting, January 8 - 12, Nairobi, Kenya.

Kavishe, M.M., 1996: Bimodal Rainfall Variability over Tanzania. Paper presented at the Third Kenva Meteorological Society Workshop, October 7- 11, Mombasa, Kenya.

Krishinan, A., 1979: Factors relevant to specification of Agricultural and Hydrological Droughts. International symposium of Hvdrological Droughts, 3 - 7 December 1979, New Delhi.

Lars Hyden, 1996: Meteorological Droughts and Rainfall Variability in the Lesotho Lowlands. M. SC Thesis. Royal Institute of Technology Stockholm, Sweden.

Mhita, M.S., 1990: The analysis of rainfall Data for agriculture in Tanzania. TMRP Research Report No. 2/90; Directorate of Meteorology Tanzania.

Mhita, M.S., and Venalainen, A., 1992. The Variability of Rainfall in Tanzania.

FINNIDA/SATCC/WMO Meteorology proiect dot., Helsinki, Finnish Meteorological Institute.

Minja, W.S.M., 1982: The weather anomalies during Northern Summers of 1972 and 1978 over Africa. Tech. Conf. on Climate of Africa, Arusha Tanzania, pp 195 - 208.

Nieuwolt, S., 1978: Rainfall and drought frequencies in East Africa, Erkunde 32: 81 - 88.

Nieuwolt, S., 1979: The East African Monsoons and their effects on Agriculture.

GEOJOURNAL. 3.2: 193 - 200

Nigan, S. and Shen, H., 1993 : Structure of Oceanic and Atmospheric Low frequency variability of the Tropical Pacific and Indian Oceans. Part I: COADS observations, American Met. Society, 657 - 676.

Nyenzi, B.S. 1984: Equatorial Zonally moving disturbances that contributed to the East African Long rains of March to May 1979. M.Sc Thesis, FSU, 73pp.

Nyenzi, B. S ., 1988: Mechanisms of East African Rainfall variability. PH.D Dissertation, FSU, Tallahassee, USA.

Nyenzi, B.S. 1990: Analysis of the Interannual variability of rainfall in East Africa. Second Tech. Conf. on Weather forecasting, in Eastern and Southern Africa, Nairobi, Kenya.

Nyeti, B.S., 1992: El Nino/Southem Oscillation (ENSO) Fluctuations and its influence to Southern Africa Climate. Proceedings of the First SADC Conference on Climate Change, Windhoek, Namibia, March 2 - 6, 1992, SADC - ELMS Coordination Unit, Maseru

1995.

Ogallo, L.J., 1980: Time Series Analysis of rainfall in East Africa. Ph.D. Thesis, University of Nairobi, Kenya.

Ogallo, L.J., and Nassib, I.R., 1984: Drought patterns and Famines in East Africa during 1982 - 83. TMP No. 15

Ogallo, L.J., 1989: The Spatial and temporal patterns of East African seasonal rainfall derived from principal component analysis. Royal Meteorological Society, 145 - 167.

Ogallo, L. J., 1994: Interannual Variability of East African Monsoons Wind Systems and their impact on East African Climate. WMO/TD-No. 619, 99-104.

Ogallo, L.J., and Ambanje, P.G., 1996: Monitoring Drought in Eastern Ati-ica.

WMO/TD NO. 753.

Palmer, W.C., 1965: Meteorological Drought. U.S.A. Weather Bureau Research paper No. 45

Thompson, B.W., 1965: Climate of Africa. Oxford Universitv Press.

Wei, W.S., 1990: Time series analysis. Addison - Weslev Publishing Company, Inc.

WMO, 1975: Special Environmental Report No. 5. Drought WMO No. 403 Yao, C.S., 1983. A statistical approach to historical records of flood and drought.

Journal of Appl. Met.. No. 21, 588 - 594

Yevjevich, V., 1967: An objective Approach to Definition and Investigations of Continental Hydrological Droughts. Hydrology Papers, Colorado State Universitv No. 23, August.

Figure 1: PhysicaL Map of Tanpnia

Figure 2: Rainfd Patterns in Taqania

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Figure 3: C~matok@.d Homogeneous Regions of Tanqaniia

LONGITUDE Figure 4: Mean Ann& Rain&!! (mm)Jw Taqania

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Figure 5: ^{Mean Seasonal} (Man&-My) Rainfal (mm) in the Bimodal Areas

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Figure 6: Areal Mean Seasonal (Ott-Dee) lbi~fal (mm) in Bimodal Atzas

194

F3gure 7: Coeflcient of Variation ofArea Seasonal (Ott-Dee) Rainfall in Bimodal Area

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Figure 8: Mean Areal Seasonal (O&April) Rainfall (mm) in Unimodd Areas