DROUGHT RISK ASSESSMENT IN KADUNA RIVER BASIN, NIGERIA :IMPLICATIONS FOR AGRICULTURAL PLANNING

Abstract

This study assessed drought risk in Kaduna River Basin (KRB) and its implications for agricultural planning. In achieving this, monthly data on rainfall, temperature, streamflow and crop yields (maize, millet and soybean) were sourced from relevant government agencies such as Nigerian Meteorological Agency (NIMET), Nigeria Hydrological Services Agency (NIHSA), Kaduna State Water Board, Shiroro Hydro-Electric Power Station Niger State Agricultural Development Project (NADP) and Kaduna State Bureau of Statistics (KDBS) for ten hydrometeorological stations (1990-2018). In addition, rainfall data were obtained from the Climate Hazards Group InfraRed Precipitation with Station data (CHIRPS) website while temperature and soil moisture data were retrieved from the ERA5 Copernicus data archive (in NetcDF) and then processed in Ferret PMEL (Linux-based) software to augment the hydrometeorological data. Landsat imageries 4, 5, 7 and 8 of 30m resolutions were also used to generate Vegetation Condition Index (VCI), Modified Normalized Difference Water Index (MNDWI) and Landuse/Landcover (LULC). DrinC (Drought Indices Calculator) software was used to calculate Potential Evapotranspiration (PET), Reconnaissance Drought Index (RDI), Standardized Precipitation Index (SPI), Agricultural Standardized Precipitation Index (ASPI) and Streamflow Drought Index (SDI) while GIS technique was used to examine the spatial dimension of drought. Pearson Correlation Coefficient Analysis was used to examine the relationship among the three drought indices and crop yields. Water Balance (WB) model was further used to estimate other WB components such as actual evapotranspiration (ETa), Water surplus (S) and Runoff (R). KRB was divided into two sub-basins (lower stream and upstream). Agricultural and hydrological drought vulnerability maps were equally produced in this study. The result from WB analysis showed the peak of R generally occurs during the wet season (April through October) mostly at the upstream. The study further revealed that the runoff efficiencies imply that <44% of annual P results in R at the upstream while <27% of annual P results in R at the lower stream. Also, from the result, it was found that Soil moisture (SM) utilization occurs mostly towards the end of the year through to the early months (November through March) across the basin while the majority of S is generated during wet season months, particularly from April through October when ~95% of S occurs on average with the peak S in August. The study revealed the base year of 1998/1999 as common year of drought onset for meteorological,