Streamflow Estimation in the Snowmelt Season Using Meteorological Factors (A Case Study: Lighvan Basin)

Study of the relations between measured variables at meteorological stations and mountain basins’ surface runoff is useful in flow modeling. In this study, to investigate the effects of time series of the recorded meteorological variables at Sahand synoptic station on the amount of snowmelt and runoff in the Lighvan basin, the correlation between these variables and average daily temperature (2001 - 2009) were reviewed to choose the variables those having appropriate correlation with the temperature. Then four index intervals in snowmelt season were determined during the period of Dec. 22nd to Jun. 21st. The correlation between the related variables and daily runoff with different lag times were examined and the variables with the highest correlation were selected. Regression equations were applied on the selected variables and then they were validated with the Liqvan hydrometry station measured runoff values. Due to the optained results, the underground temperature at the depth of 20cm had the best correlation (r = 0.911) with runoff measured values during the period of Dec. 22nd to Jun. 21st while no lag time was considered the relevant series. Also, the lowest correlation (r = -0.476) was obtained for the humidity at time of 3am in the same period with lag times of 4 and 5 days. The results of validatation of the regression models showed that the stepwise regression model had an admissible accuracy (CE = 0.61) in estimation of streamflow in snowmelt season.