en Optimal design Optimal design پژوهشي Research <p dir="ltr">In this study, optimum combinations of available rainfall gauging stations are selected by a&nbsp;model which is consist of geo statistics model as an estimator &nbsp;and an optimized model. At&nbsp;the &nbsp;first, &nbsp;watershed &nbsp;is &nbsp;approximated &nbsp;to &nbsp;several &nbsp;regular &nbsp;geometric &nbsp;shapes. &nbsp;Then &nbsp;kriging&nbsp;calculates &nbsp;the &nbsp;variance &nbsp;of &nbsp;the &nbsp;estimation &nbsp;error &nbsp;of &nbsp;different &nbsp;combinations &nbsp;from &nbsp;available&nbsp;rainfall gauging stations using inside and outside stations of watershed. In each combination,&nbsp;n is number of considered stations and N is number of available stations (N>n). At the end,&nbsp;the best combination is selected by genetic algorithm (the &nbsp;error variance of this combination&nbsp;is minimum). For optimal set with one sample point (station) estimator model and optimize&nbsp;model select station that locates near to center of watershed. While for two stations case,&nbsp;these models select two stations that l ocate in boundaries face to face. Also for combination&nbsp;n &nbsp;stations &nbsp;of &nbsp;N &nbsp;stations, &nbsp;selected &nbsp;stations &nbsp;have good &nbsp;and &nbsp;proportional &nbsp;distribution &nbsp;in&nbsp;watershed. These results show correctness of research methodology.<br> In this study, effects of variations of paramet ers of theoretical variogram and number of&nbsp;blocks &nbsp;in &nbsp;block &nbsp;estimation &nbsp;of &nbsp;kriging &nbsp;method &nbsp;are &nbsp;evaluated &nbsp;too. &nbsp;The &nbsp;variance &nbsp;of &nbsp;the&nbsp;estimation error from block estimation with 8*8 blocks has showed the acceptable results.<br> This research shows a linear relation between variations of error variance and scale of&nbsp;variogram. Optimum combination does not vary with variations of scale of variogram but it&nbsp;varies with variations of range of variogram. Increasing of nugget effect of variogram would&nbsp;raise the variance but does not vary optimum combinations.</p> kriging, geo statistics, genetic algorithm, combination of rainfall gauging stations. 581 594 http://ijoce.iust.ac.ir/browse.php?a_code=A-10-66-118&slc_lang=en&sid=1 A. Adib 180031947532846001043 180031947532846001043 Yes M. Moslemzadeh 180031947532846001044 180031947532846001044 No