溪 is often combined: 小溪 (xiǎoxī, small stream), 溪流 (xīliú, brook), 溪水 (xīshuǐ, stream water). It refers to smaller waterways than 河 (river) or 江 (large river).
memory
The left radical 氵(water) plus 奚 (xī, phonetic component). Water + the sound = a stream.