Spatio-Temporal Variation of Actual Evapotranspiration of Lower River Kaduna Catchment, Nigeria

Assessing spatio-temporal variation of actual evapotranspiration is very important, most especially in the areas that are prone to changing climate. Lower River Kaduna is one of the critical ecosystems in the northwest, Nigeria. As such it is critical to investigate the evapotranspiration of this area, because of its impact on water availability for both human, plants, and other organism population dwelling the basin. ModisTerra imageries from 2000-2014 were used to computecrop coefficient (Kc) through a relationship with normalize difference vegetation index (NDVI). Makkink method was used to estimate the reference evapotranspiration using temperature and solar radiation obtained from Nigerian Meteorological Agency. Actual evapotranspiration was estimated by multiplying evapotranspiration and crop coefficient. Trend analysis was determined using Mann-Kendall and Sen’s slope. The results reveal that the actual evapotranspiration of annual is less than 61% of winter and 71% of autumn. Spring and summer Actual evapotranspiration value are less than annual with 51% and 79%. Annual, winter and summer have a decreased of actual evapotranspiration. It also reveals that spring and autumn has an increased of actual evapotranspiration. The spatio-temporal result reveals that the vegetated area has a high Actual evapotranspiration while the non-vegetated area has lower Actual evapotranspiration value.