Abstract. The main objective of this study was to calibrate and validate the eco-hydrological model Soil and Water Assessment Tool (SWAT) with satellite-based actual evapotranspiration (AET) data from the Global Land Evaporation Amsterdam Model (GLEAM_v3.0a) and from the Moderate Resolution Imaging Spectroradiometer Global Evaporation (MOD16) for the Ogun River Basin (20 292 km2) located in southwestern Nigeria. Three potential evapotranspiration (PET) equations (Hargreaves, Priestley–Taylor and Penman–Monteith) were used for the SWAT simulation of AET. The reference simulations were the three AET variables simulated with SWAT before model calibration took place. The sequential uncertainty fitting technique (SUFI-2) was used for the SWAT model sensitivity analysis, calibration, validation and uncertainty analysis. The GLEAM_v3.0a and MOD16 products were subsequently used to calibrate the three SWAT-simulated AET variables, thereby obtaining six calibrations–validations at a monthly timescale. The model performance for the three SWAT model runs was evaluated for each of the 53 subbasins against the GLEAM_v3.0a and MOD16 products, which enabled the best model run with the highest-performing satellite-based AET product to be chosen. A verification of the simulated AET variable was carried out by (i) comparing the simulated AET of the calibrated model to GLEAM_v3.0b AET, which is a product that has different forcing data than the version of GLEAM used for the calibration, and (ii) assessing the long-term average annual and average monthly water balances at the outlet of the watershed. Overall, the SWAT model, composed of the Hargreaves PET equation and calibrated using the GLEAM_v3.0a data (GS1), performed well for the simulation of AET and provided a good level of confidence for using the SWAT model as a decision support tool. The 95 % uncertainty of the SWAT-simulated variable bracketed most of the satellite-based AET data in each subbasin. A validation of the simulated soil moisture dynamics for GS1 was carried out using satellite-retrieved soil moisture data, which revealed good agreement. The SWAT model (GS1) also captured the seasonal variability of the water balance components at the outlet of the watershed. This study demonstrated the potential to use remotely sensed evapotranspiration data for hydrological model calibration and validation in a sparsely gauged large river basin with reasonable accuracy. The novelty of the study is the use of these freely available satellite-derived AET datasets to effectively calibrate and validate an eco-hydrological model for a data-scarce catchment.

comparing the simulated AET of the calibrated model to GLEAM_v3.0b AET, this is a product that has a different forcing 30 data to version of GLEAM used for the calibration, and (ii) assessing the long-term average annual and average monthly water balances at the outlet of the watershed. Overall, the SWAT model structure composed of Hargreaves PET equation and calibrated using the GLEAM_v3.0a data performed well for the simulation of AET and provided a good level of confidence for using the SWAT model as a decision support tool. The 95% uncertainty of the SWAT simulated variable bracketed most

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The study examined the changing pattern in livestock types in Sokoto Rima-River Basin, semi-arid Nigeria. Clustered sampling technique was used to administer questionnaire to 450 respondents from 15 agricultural settlements in 15 Local Government Areas in the basin. Data were analyzed using frequency counts, percentages and pairwise t-test. Seventy-one percent (70.7%) of the farmers reared livestock in the 1970s, out of which 10.2 to 13.6% reared only cattle, sheep and goats while the combination of cattle and sheep, cattle and goats, sheep and goats, and cattle, sheep and goats varied from 3.6 to 20.2%. In the 2000s, 80% of the farmers reared livestock, with a variation of 10.4 to 11.6% for cattle, sheep and goats only, and 2.9 to 26% for cattle and sheep, cattle and goats, sheep and goats and cattle, sheep and goats respectively. The total of 39.6 to 45% farmers in the basin reared cattle, sheep and goats in the 1970s while 44.7 to 55.1% reared it in 2000s. The rearing of cattle only, sheep and goats, and cattle, sheep and goats together increased by 0.2% to 6.6% while sheep only, goats only, cattle and sheep, and cattle and goats decreased by 0.3% to 2%. The total cattle reared has increased by 5.1% over time, while that of sheep and goats increased by 10.1% and 11.4% respectively. Sheep are 2.4% more than goats and 10.4% more than cattle. Livestock rearing has increased by 9.3% during the study period. A pairwise t-test showed no significant difference between the livestock types in the 1970s and 2000s in the study period.

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