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Analysis of Depth-area-duration Curves of Rainfall in Semi-arid and Arid Regions Using Geostatistical Methods (Case Study: Sirjan Kafeh Namak Watershed)

Author(s): K. Solaimani | A. Abkar | M. Habibnejad | M.Z. Ahmadi

Journal: Pakistan Journal of Biological Sciences
ISSN 1028-8880

Volume: 9;
Issue: 9;
Start page: 1764;
Date: 2006;
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Keywords: Sijan Kafah Namak watershed | Krigging | isohyets maps | DAD curve

Drawing isohyets maps is one of the main steps in preparation of depth-area-duration (DAD) curves. To draw these maps different methods are used such as using rainfall gradient, simple classic statistical methods and complicated Geostatistical methods like Krigging method. For this purpose, after collection of data and information related to 59 rainfall gauging stations in the study area, The dominant and maximum rainfall for durations of one to three days were selected. Then for drawing the isohyets maps, the relationship between rainfall and the elevation were investigated, but due to insignificant difference of this relationship, two methods of Geostatistical Krigging and inverse distance with powers of 1 to 3, were evaluated to draw the isohyets maps and determination of the average rainfall. To evaluate the above two methods, Mean Absolute Error (MAE) was used in this research. The results of this evaluation showed that the Krigging method is better than inverse distance method for determination of average rainfall of the region. Then, by using krigging method, the isohyets maps of one to three -day duration and DAD curves were drawn. By using this method, conversion of point rainfall to average rainfall for an area of up to 20000 km2 of the area under study is possible. Also, the investigation of the curves shows that the ratio of the amount of rainfall at the center to the amount of rainfall at an area of 20000 km2 is 1.98, .74 and 1.48 for durations of 1, and 3- day, respectively.
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