Application of the risk monitoring drought of dryland products sub basically scale of sub basin on improvement of drought management(Case study: Khorramabad Basin)

Drought risk management requires a strategy. Choosing a spatial scale is one of the strategic aspects. In the present study, drought monitoring was carried out at sub-basin scale and for dry lands products. For this purpose, using the SWAT simulator, the Khorramabad basin with a total area of 2480 km2 was divided into 31 sub-basins based on homogeneity of soil texture, land use and elevation. The RDI Drought Detection Index was calculated on a 9-month time scale for assessing agricultural drought during the period of 1348-1396, in accordance with the crop year. Using Thiessen method and the use of meteorological stations in the studied area, rainfall and temperature of each sub-basin, the estimation and relative reduction of yield of dryland products were calculated for each of the different drought intensities. The present study was able to compare the different areas of the basin with respect to the drought risk in different products. So that the risk of product production varies from 14 to 30 percent in each sub-basin. The average risk of producing dryland products including wheat, barley, peas and lentils was 21.2%, 18.8%, 17.4% and 18%, respectively. The results also showed that the effect of drought severity on the yield of each product is different. So, in the middle drought, 54-60, 47-55, 46-54, 47-57%, severe drought, 63-70, 58-64, 49-60, 51-62% and very severe drought, 75-82, 69-74, 59-68, 67-74%, reduced potential yield of each product, respectively, wheat, barley, peas and lentils respectively.