Statistical and spatial variability of climate data in the Mareb-Gash river basin in Eritrea

Introduction. Global reanalysis products are extensively used for hydrologic applications in sparse data regions. The establishment of inputs for hydrologic modelling from such global reanalysis requires prior checking and analyses. Materials and methods. The present study attempts to utilize Climate Forecast System Reanalysis (CFSR) datasets for the Mereb-Gash river basin in Eritrea, to prepare the input data for forthcoming hydrological modelling studies. The activities include statistical analyses, computation of PET, and drought indices using different methods so as to understand basin characteristics through the use of geospatial and geostatistical tools. Results. The results of statistical analyses indicated that there was predominantly a significant monotonic trend in the majority of the data. Precipitation (P) and relative humidity tend to decrease, whereas temperature (T) and potential evapotranspiration (PET) tend to increase. Among the PET estimation methods, the Thornthwaite method gave inconsistent results as compared to Hargreaves and Penman-Monteith methods, the former being highly dependent on the elevation of the station. In most cases, it was found that Penman-Monteith produced the highest PET values. Conclusions. Besides, Standardized Precipitation and Evapotranspiration Index (SPEI) analyses in the basin indicate persistent dry conditions over the period 2000–2013 and predominantly humid conditions over the period 1979–2000. The study concluded that the presence of a significant trend in most of the climatic variables and persistent drought conditions in recent years were found to be congruent with global and regional climatic studies that are highly likely linked to human and climate influence on the environment.