Showing papers by "Atsushi Tsunekawa published in 2016"

Analyzing the hydrologic effects of region-wide land and water development interventions: a case study of the Upper Blue Nile basin

Abstract: In the drylands of the Upper Blue Nile basin, high climate variability and land degradation are rampant To enhance adaptive capacity in the region, various soil and water conservation interventions have been implemented Moreover, water resources development schemes such as the Grand Ethiopian Renaissance Dam should be implemented by 2025 We modeled the effects of these interventions on surface runoff in the basin for both current and future (2025) basin conditions, using the runoff coefficient method in a spatially explicit approach Under current conditions, we observed high spatial variability of mean annual runoff The northeastern Blue Nile-1 sub-basin produces the highest mean annual runoff (391 mm or 10 × 109 m3), whereas the northwestern Blue Nile-2 sub-basin produces the lowest mean annual runoff (178 mm or 02 × 109 m3) The basin generates a total annual runoff volume of 477 × 109 m3, of which about 54 % comes from cultivated land The strong association between land use and topography masked the direct effect of rainfall on runoff By 2025, total annual runoff yield could decrease by up to 38 % if appropriate basin-wide soil and water conservation interventions and the Grand Ethiopian Renaissance Dam are implemented However, the full effects of most physical structures will only last for 1 or 2 years without regular maintenance The improved understanding of the dynamics of the Upper Blue Nile basin’s hydrology provided by the present study will help planners to design appropriate management scenarios Developing the basin’s database remains important for a holistic understanding of the impacts of future development interventions

Evaluation of kinetic energy and erosivity potential of simulated rainfall using Laser Precipitation Monitor

Abstract: Rainfall kinetic energy is a widely recognized indicator of a raindrop's ability to detach soil particles in rainsplash erosion. However, it is challenging to estimate the kinetic energy (KE) of a given rain event, because it involves analysis of the terminal velocity and drop size distribution (DSD) of raindrops. A preferred alternative is to relate KE to rainfall intensity. Therefore we sought to characterize simulated rainfall, establish a relationship between kinetic energy and intensity as a function of both time ( KE t , J m − 2 h − 1 ) and volume ( KE vol , J m − 2 mm − 1 ), and examine the erosivity potential of each event. A rainfall simulator and Laser Precipitation Monitor (optical disdrometer) were used to characterize raindrop size, terminal velocity and KE at different rainfall intensities (1.5 to 202 mm h − 1 ). Values of KE t ranged from 26.67 to 5955 J m − 2 h − 1 and KE vol ranged from 16.10 to 34.85 J m − 2 mm − 1 , which is comparable to values determined from natural rain of similar intensity ranges. A power-law function and a polynomial function between KE t and rainfall intensity had coefficients of determination ( R 2 ) of 0.99 and 0.98 ( P KE vol and intensity was a power-law function ( R 2 = 0.95; P R 2 = 0.99; P