bir türlü çalıştıramadım

Options +FollowSymlinks
Options -Indexes
RewriteEngine on
RewriteBase /siteadi/
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*) $1.php
RewriteRule ^basin/([a-zA-Z0-9_-]+)$ basin.php?id=$1 [L]