Journal of Food, Agriculture and Environment

Evaluation of runoff and the effect of external factors on the potentials of water resources – Case study: Eastern, western and central regions of Guilan Province located in the southwestern coasts of the Caspian Sea in Iran

Author(s):

Mohammad Mohammadi Fatideh

Recieved Date: 2009-01-23, Accepted Date: 2009-04-20

Abstract:

Evaluation of runoff and the effect of external factors on the potentials of water resources is among important studies that experts of water sciences and techniques conduct in their regional researches. In this research by using some common methods, the most significant effective external factors in the potentials of water resources and their annual mean volume throughout Guilan province were evaluated. To do so, main decisive factors of the climatic conditions, including atmospheric circulations, Demarton monthly aridity index (I_m), Demarton annual aridity index (I_y), Emberger precipitation coefficient (Q₂) and Henin drainage index (D), were studied first. Then, factors effective on water balance including potential evapotranspiration (ETP), actual evapotranspiration (ETR) and total runoff (Q) were calculated using Thornthwaite method. By applying Turc and Coutagne formulas, actual evapotranspiration (ETR) and total runoff values were calculated as well. Obtained mean values showed that about 45% of the precipitations turned into total runoff while the remaining 55% was changed into actual evapotranspiration. On the other hand, the mean value of the potential evapotranspiration was about 77% of precipitations. With consideration of the obtained results for the entire Guilan province, having an area of about 14,700 km², the mean value of the annual volume for each external factor was as follows: P (Precipitations) = 13,247,410,000 m³, ETR = 7,281,325,500 m³ and Q = 5,964,485,000 m³. Obtained results and the study of the main decisive climatic factors completely corresponded to those of temperate regions. Thus, the above-mentioned methods were applicable for various fields of water engineering in Guilan climatic conditions. In particular, it was possible to use them for evaluating the total runoff rate in catchment basins, which did not have hydrometric equipment.

Keywords:

Thornthwaite, Turc and Coutagne formulas, runoff, actual evapotranspiration, potential evapotranspiration, water balance

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Journal: Journal of Food, Agriculture and Environment
Year: 2009
Volume: 7
Issue: 2
Category: Environment
Pages: 777-787

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