Hydrodynamic Analysis of Riverbed Deposits of Underground Dam Construction Site for Water Harvesting (Case Study Mashnaq Underground Dam)

Today, the use of underground dam technology is considered as one of the efficient methods of rainwater harvesting systems and flood management in order to eliminate the shortage of water resources in arid and semi-arid regions. Underground dams block the subsurface flow of water across the river and stores it in the riverbed. The construction of an underground dam, while helping the environment, will compensate for surface water and expand cultivated lands. The content of water extracted from these dams depends on the hydraulic and hydrodynamic of alluvial sediments. The aim of the present study was to determine the hydrodynamics of the riverbed deposits of the Meshnaqeh underground dam in the north of Lake Urmia. Feasibility study and location of the dam axis was done using ArcGIS system. Three options were determined and finalized after a geophysical evaluation of the location of the main alluvium with a thickness of 14 m. Engineering studies showed that the sedimentation of bed was in gravel and sandy soils in UNIFIDE division with more than 78% of sand, and according ASTM method, were in the GC and GM. Lefranc experiment showed that alluvial sediments had a permeability of 0.0012 cm/s and a porosity above 35%. According to the special discharge, 163,800 m3 of water can be harvested in each flooding period. Drinking water and sanitation of the region is provided hundreds of kilometers away through Zarrinehroud water transmission line. The construction of this dam with a realistic view of the real value of water and its role in human societies, will have constructive environmental effects requiring independent study.