Abstract:
The purpose of this study was to investigate subsurface dam in the alluvial stream flow
areas of Afar National Regional State, where critical water shortage is the problem of the
dwellers in the area. Assessment was done on the selected two (Mille and Jara) rivers in
the Awash river basin. Arc-GIS and its extensions Arc Hydro and HEC-GeoHMS were
used to delineate the sub basins from Digital elevation Model of Awash River basin and
analyze the soil and land use and cover.
In the study HEC-HMS and HEC-RAS modeling software's were used to determine the
rainfall-runoff transformations of the basins from daily rainfall and analysis the flood
depth and bank stability to convey the river flow respectively.
Soil composition of the storage areas was analyzed to estimate the storage capacity of the
reservoir and its yield. Additional soil composition of the catchment was determined
through HEC-GeoHMS to forecast the reason of river flow depletion in the rivers valley.
From hydrological analysis the peak discharges of the two catchments were found
755. lm
3
/ s and 181 . 4m
3
/s with a volume of 19388.2x10
6
m
3
and 2108.6xl0
6
m
3
for Mille
and Jara using daily rainfall analysis of the catchments.
From discharges analyzed in hydrologic model and the flow depth was generated by
HEC-RAS for surveyed sections of the river; and the capacity of the river was rested
whether it safely convey. the discharge or overtop the banks. The rivers can convey the
peak discharge in most of its way and overtop in one or more sections of the bank.
Groyne type ofriver training method was proposed for enhancing both river training and
recharging the subsurface storage area. Additionally levee t ype of river training was
recommended to control over the overtopping problem in some sections of the rivers.
Water requirement analyses was made t o assure that subsurface dam can cover the
\
demand of the area for the critical conditions.
