Study of Morphometric Properties and Water Balance Using Thornthwaite Method in Khanaqin Basin, East of Iraq.

Abstract

Water balance techniques are a means of solution of important theoretical and practical hydrological problems, where morphometric analysis of a watershed provides a quantitative description of the drainage system, which is an important aspect of the characterization of watersheds. The evaluated quantities of drainage morphology in Khanaqin basin which located to the East of Iraq were Perimeters (P), length (L), width (W), circulatory ratio (Rc), elongation ratio (Re), form factor (Rf), compactness coefficient (Cc), stream order (Su), stream numbers (Nu) and lemniscate factor (K). The catchment's area was (1920) km2, characterized by is elongated low relief, gentle ground slopes and far from being circular with moderate peak flows of fifth stream order. The ratio of water surplus calculated from annual rainfall was (13.15%) and the actual evapotranspiration and soil moisture was (86.82%) according to average annual rainfall during (1990-2013) using Thornthwaite equations to calculate potential and actual evapotranspiration. The water surplus calculated as (35.973) mm distributed into (25.713) mm as natural recharge of groundwater and (10.26) mm surface runoff.