جستجوی مقالات مرتبط با کلیدواژه « شدت و مدت خشکسالی » در نشریات گروه « آب و خاک »

Determining the onset, severity and duration of drought provides vital information for managing water resources to decision makers. The computation of these parameters requires integrated data on soil moisture content and groundwater level. The installation and utilization of a regular network system for recording these data in massive water basins is very costly. In the central plateau catchment of Iran where the average rainfall is very small, the required observational data with suitable spatial distribution are not available. In this paper, the frequency, duration and severity of agricultural droughts in this catchment are determined by the Total Storage Deficit Index (TSDI) obtained from the GRACE satellite based-data. Then, due to the heterogeneous distribution of meteorological stations in the studied area, 142 stations were selected and the MicroMet interpolation model and Kriging geostatistical method were used to fit a homogenous network on the meteorological data at the catchment area. Finally, the Standardized Precipitation Evapotranspiration Index (SPEI) was calculated with timescales of 3, 6 and 12 months to be compared with the results of TSDI. Based on these calculations, the studied area has experienced several agricultural droughts with different severity and extent that the spatio-temporal distribution and drought severity obtained from both indices are in good agreement with each other.

To analyze and manage the risk of drought in a region, access to some certain information is required, the most important of which is the frequency of drought severity-duration. Realizing the high correlation of these factors, one must pick up a method that pinpoint the relation and effects of these factors on drought analysis. In this paper, numerous copula families were employed to model the correlation structure of variables. Drought data and a three month standardized precipitation index in six stations of Tehran were employed. It is illustrated how to fit a model and compare different copula families to find the most appropriate copula function for the data. Next, by using the best selected copula function, the probabilistic behavior of drought from the severity–duration aspect was modeled based on the observations. The results show the relative closeness of frequencies of drought duration-severity in these stations, so that they can be presented for the province. In addition, the data were also analyzed based on the fitted model and the drought thresholds. That would make the results be more applicable, especially in bringing about the possibility of defining drought scenarios.