I don't know much about the LCD driver that you're using, but you could always use the "sprintf" function to format a string variable with the value to be displayed embedded, then print the resulting file.
char buffer [17]; // 17 chars = "WATER LEVEL 100%" & null
sprintf(buffer, "WATER LEVEL %3d", level);
lcd.print(buffer);
...it does use ram, for the buffer, and more NVM for the library (I guess)