جستجوی مقالات مرتبط با کلیدواژه « شاخص خشکسالی جریانات رودخانه‏ ای » در نشریات گروه « کشاورزی »

Drought is a natural, repeatedly and temporary event, that is caused by decreasing in rainfall amount than in long term average whether it can happen in every climate, and is one of the disturbing events in nature that causes the most damage to water resources. In this study was used modified Indexes Standardized Precipitation (SPImod) and streamflow drought index (SDImod) for purposes of temporal assessment and analysis of droughts occurrence, monthly data of 15 rain gauge and 4 hydrometric stations in Tajan basin were used and indices in six timeframes short-term (one-month and three-month) intermediate term (six -month and nine -month periods) and long-term (12 months and 24 months were calculated in MATLAB software. In part of the research, Pearson correlation coefficient between precipitation and flow with different time delays was calculated to determine the delay of currents' delay to precipitation in real mode. Then the modified Streamflow drought index (SDImod) with modified Standardized Precipitation Indexe (SPImod) time series at various temporal interval using Pearson correlation was studied in the whole of basin and sub basins also compared separately. The results showed that temporal relationship between hydrological and meteorological drought occurrence is significant at 99 % level with together and this correlation is maximum in the 9 months' time step in Tajan basin. Also Drought occurrence in case study area showed its effect with a delay of 1 to 7 months on surface water resources.

Drought is one of the known environmental phenomenon and impartible part of change climate that occurs in each geographic region. In this study was used Standardized Precipitation Index (SPI) and streamflow drought index (SDI) for assessment and analysis of droughts incidence temporal. For this purpose, were used monthly statistics of 10 rain gauge and 5 hydrometric stations in Karkheh watershed and indicators investigated in 3 timeframes (12, 24, 48 months). At the first, relationship of precipitation and runoff investigated for drought effect study on surface water resources. Then the standardized data rate (SDI) with SPI time series at varies temporal interval using Pearson correlation was studied in the whole of basin and sub basin also compared separately. The results showed that temporal relationship of hydrological and meteorological drought occurrence is meaningful in level of 99 % with together and this correlation is maximum in 48 months. Drought occurrence in case study showed its effect on surface water resources with a delay of 2 months or 1 month that due to the karstic region.

Drought is a natural and recurring phenomenon which causes water scarcity in various sectors. In comparison with other natural hazards and disasters, drought is more important considering intensity and frequency as well as spatial extent and total damage. In the current research, the Standardized Precipitation Index (SPI) and Standardized Discharge Index (SDI) were used to analyze the temporal characteristics of droughts. To this end, monthly precipitation time series of 23 raingauge stations and 7 hydrometry stations across the Atrak River basin were used and SPI and SDI for six time intervals (3, 6, 9, 12, 24 and 48 months) were calculated and analyzed. For assessment of drought impact on surface water resources, first the correlation between rain and discharge time series of different lag times were calculated within the study area. Then, the Pearson correlation method was applied to calculate the correlation between SDI and SPI series for different time intervals at each individual subwatershed and whole watershed of the Atrak River. The results showed that the correlation between meteorological and hydrological droughts was significant at 99 percent confidence level. The maximum correlation was found for SPI and SDI of 3 months time intervals. This indicates that droughts cause decrease in surface flows and this impact is remarkably observed in the discharge values of the same month or one month later. The highest Pearson correlation was found for the Shirabad station and the Darband subwatershed.