Page - 636 - in Book of Full Papers - Symposium Hydro Engineering

warming), by shifting precipitation from cold seasons to warm seasons and vice versa, or changing the pattern of seasonal precipitation from snow to rain, obligate all water resource management components to be reviewed. Changing the precipitation pattern, discussed in this study also reduces the snow storm and the displacement of the rivers' regeneration regime. In this way, river basic discharge and dams' adjustment capacity are lowered and the supply and demand balance of the water system is impaired. On the other hand, changes in the precipitation pattern will increase the uncertainty in supplying the plant's water requirements with effective precipitation in the cultivation season. The first effect of these uncertainties is to increase the reliability coefficients used in supplying the water needs of the agricultural sector and thus increasing the need for water extraction. Investigating Taleghan Basin data during 1959-2012, indicates that significant changes have occurred in some of the hydrological parameters of the area. The most important results from the calculations are: The issue of the effect of temperature change and precipitation pattern on water resources of Taleghan basin is definite. Figure 9: Time series and trend line for snow cover level in Taleghan basin in February No trend in precipitation series is observed on the annual and monthly scale of precipitation. This confirms other previous researches before referred to in the introduction. Meanwhile, the increasing trend of temperature in the Taleghan basin is in line with the results of the research in other regions of Iran. Due to the lack of trend in runoff, the annual scale is not a suitable scale for study of hydrological changes in rivers with a snow-rainy regime. In discharge time series, an incremental trend is observed during the months of March and April (around 7%), and a decreasing trend in May and June (about 10%). This means that the spring runoff has declined sharply, and instead of winter runoff, increased over these periods. This factor stems from the increase in winter temperature, which is due to the decrease in snowfall during recent years, indicating a change in precipitation pattern in the basin and precipitation change from snow to rain. 636