DEVELOPMENT AND APPLICATION OF DROUGHT FORECASTING MODELS FOR NIGERIA SUDANO SAHELIAN REGION

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Department of Engineering

ABSTRACT
Drought is a creeping natural phenomenon affecting the arid and semi arid regions, including Nigerian Sudano-Sahelian Region. This research investigated droughts in Nigeria Sudano-Sahelian Region and developed forecasting models for drought monitoring and management in the region using well analysed meteorological data and imageries. The meteorological data consists of temperature and rainfall data, both from 1979 to 2008, collected from Nigeria Meteorological Organisation (NIMET), Oshodi, Lagos. The Imageries consist of Normalized Difference Vegetation Index (NDVI) spanning 1981 to 2011, obtained from National Aeronautics and Space Administration (NASA) and SPOT – Vegetation Programme of Vision on Technology (VITO), websites. Standardized Precipitation Index (SPI) at different time scales were extracted from the rainfall record and compared to determine the most suitable one for real time and early warning tool for drought forecasting and, it was discovered that SPI_1 reflected nearly all droughts from near normal condition to very severe dry condition. As a result, SPI_1 was chosen for modelling but, it was compared with monthly NDVI anomaly to select the better one. The results indicated that drought episodes detected by NDVI anomaly lagged some months behind the corresponding ones identified by SPI_1. Hence SPI_1 was modelled, based on Auto Regressive Moving Average/Seasonal Auto Regressive Moving Average (ARIMA/SARIMA), to simulate drought occurrence at each station. Multiplicative SARIMA model found suitable for SPI_1 forecasting at Sokoto, Nguru, Potiskum, Kano and Gusau Stations was (011)x(011)12 while SARIMA model (1,1,1)x(1,1,1)12 was found suitable for SPI_1 forecasting in Katsina and Maiduguri Stations. The multiplicative SARIMA temperature models developed for Sokoto, Nguru, Potiskum, Kano and Gusau Stations was SARIMA (2,1,1)x(2,1,1)12 while SARIMA (3,1,1)x(3,1,1)12 was found most vii suitable for Katsina and Maiduguri Stations. Drought analysis in the region showed that the region had been exposed to droughts of different severity and magnitudes although, the level of risk varies from one location to another. The region had been classified into high drought risk zone consisting of Sokoto, Katsina, Damaturu and Nguru Stations, both in Yobe, and Maiduguri. Moderate risk zone included Guzau, Kano and Dutse while parts of Bauchi and Gombe States were identified as low risk zone. A drought management plan was proposed for the study area based on the developed forecasting models. The plan has three phases of drought emergence watch, warning and emergency.