Search

Full and reliable rainfall data are required for hydrological modelling, integrated water resource management, and planning. However, these data suffer from record gaps and sparse rain gage distribution, which implies that the use of an imputation method is crucial. This study aims to compare the outputs from 10 imputation methods that were used to infill missing rainfall depth data (MRD) in an arid Mediterranean region. Different statistical tests were used to assess the outputs from the imputation methods. The results showed that for MRD ranges between 5 and 20% the stepwise multiple linear regression (MLRsw) method was valid and produced the best results with a root‐mean‐square error (RSME) and mean absolute error (MAE) of less than 7 and 2 mm, respectively. This was followed by the Monte Carlo Markov chain expectation–maximization‐based multiple imputation (MI‐MCMC) method, which had an RSME and MAE of 1.01 and 0.08 mm, respectively, at 20% MRD. On the other hand, the use of satellite data for imputation (LR_GPCC estimates) was appropriate for MRD ranging between 10 and 15%, while the statistical and spatial method was suitable for MRD of less than 5%. [ABSTRACT FROM AUTHOR]

Arid regions are characterized by fragile soils that differ in behavior according to their physical and chemical compositions. In this study, the wetted soil surface area was measured for four different soil types to assess the impact of the individual soil particles (silt, sand and clay separates) on soil surface wetting area, under different application rates using point source trickle irrigation. Three flow rates were tested 4, 8 and 12 liters per hour (Lph) on four different soil types (silt loam, loam, sandy loam58sand and sandy loam77sand). Soil surface wetted area increases as emitter flow rate increases. The results showed that increasing emitter flow rate from 4 to 8 and to 12 Lph, increased soil surface wetted area by about 60 and 160%, respectively. Soil surface wetted areas in loam soil and silt loam soils were 1.5 and 2.8 times that in sandy loam soils, respectively. Soil surface wetted area increases rapidly with time initially, but then increases at a decreasing rate, until the application rate became in equilibrium with soil infiltration rate. The surface wetted area had good correlation with the percentages of silt, sand and clay soil particles, with regression correlation ranging from 0.90 to 0.97. The trends were increased wetting with clay and silt and decreased wetting with sand. The expected losses on the form of evaporation in arid soils suffering from surface crust, therefore, would increase in soils dominated by silt or clay when compared with sand, indicating that cropping pattern in arid environments should be carefully selected in areas with scarce water resources. [ABSTRACT FROM AUTHOR]