شناسايي عوامل موثر بر جريان كم در حوزه هاي آبخيز استان تهران

Determining effective factors on low flow regime using component analysis(Case study: Tehran province watersheds)

Low flow is a complex phenomenon that different factors directly or indirectly affect on its procedure. This factors contain edaphic, climatic and management factors. Morphogenetic characteristic are the important edaphic factors which with regard to less changeability and affecting on flows procedures has the especially importance. Morphometry factors with climatic and geology is the principal factors in hydrologic interactions. Although, principal method for morphometey and flows relations investigating and analyzing relations between watershed characteristic, climatic data and flow characteristics. Identify effect factors on low flows has the especially importance. To determine the effective factors on low flow, Tehran province watersheds were divided into 12 sub-watersheds. Then, all affects physical and climatic factors on low flow in each sub-watershed using GIs was recognized. In addition Drainage densities Graveluous, Miller, Schumm, Horton coefficient, and unit shape factor were calculated. Then these factors were analysed using the principal compenent analysis. Based on the most effective factors were: Area, mean annual precipitation, average weighted infiltration and average slope of the watershed that illustrate 99. 36 of variation of data. Then homogeneity areas were identified using cluster analysis and two-homagenity area was obtained.